John Yap - Academia.edu (original) (raw)

Papers by John Yap

Background: There has been a dearth of collaborative learning across tertiary institutions due to... more Background: There has been a dearth of collaborative learning across tertiary institutions due to challenges in scheduling and geographical locations. Three dimensional virtual environments are a viable and innovative tool to bring diverse healthcare students to learn together. Objective: The purpose of this study is to describe the development of a multiuser virtual environment and to evaluate healthcare students' experiences of their collaborative learning in the environment. Methods: A mixed method study design was employed. Participants from six healthcare courses (Medicine, Nursing, Pharmacy, Physiotherapy, Occupational Therapy, and Medical Social Work) were recruited from three institutions to form six interprofessional healthcare teams who participated in interdisciplinary team care via a virtual environment. Four focus groups were conducted with 27 healthcare students after they completed questionnaires to evaluate their perceived usability, the sociability of computer-supported collaborative learning, and senses of presence. Interview transcripts were analyzed using thematic analysis. Results: Four themes emerged from the students' experiences: "Bringing everyone together" to learn in the virtual platform was perceived as a valuable experience; "Feeling real", whereby the students felt immersed in their own healthcare profession's roles; learning in the virtual environment was perceived as "less threatening" compared to face-to-face interactions; and there were some "technical hiccups" related to sound quality and navigation. The participants reported positively on the usability (mean 3.48, SD 0.64) and feasibility (mean 3.39, SD 0.60) of the virtual environment in supporting collaborative learning. With a maximum score of 168, they also perceived a moderately strong sense of presence (mean 107.24, SD 17.78) in the environment. Conclusion: This study provides evidence for the acceptance of a virtual platform for collaborative learning in team care delivery. Given its flexibility, practicality, and scalability, this virtual platform serves as a promising tool for collaborative learning across different healthcare courses and institutions.

Journal of Medical Internet Research, 2019

?hl=en_US&formkey=dGl… 5/41 yes: all primary outcomes were signi cantly better in intervention gr... more ?hl=en_US&formkey=dGl… 5/41 yes: all primary outcomes were signi cantly better in intervention group vs control partly: SOME primary outcomes were signi cantly better in intervention group vs control no statistically signi cant difference between control and intervention potentially harmful: control was signi cantly better than intervention in one or more outcomes

EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology, Jan 18, 2016

The aim of this study was to introduce and demonstrate the feasibility in an acute preclinical mo... more The aim of this study was to introduce and demonstrate the feasibility in an acute preclinical model of a new transcatheter heart valve concept with a self-expanding wire frame, polymeric leaflets and a sealing component. The TRISKELE valve was developed based on a previously validated polymeric leaflet design, an adaptive sealing cuff and a novel nitinol wire frame which reduces stress on the leaflets and radial pressure on the surrounding tissue. A valve prototype of 26 mm nominal diameter was manufactured by automated dip coating of a biostable polymer. The prototype was implanted via brachiocephalic approach in orthotopic position in an acute ovine model through a highly controllable multistage deployment process. The atraumatic retrievability of the valve after full expansion was verified in situ before final release in the optimal position. Observation indicated secure valve anchoring, adequate leaflet motion, and no interference of coronary flow or mitral valve function. The ...

Intensive care medicine, Jan 3, 2015

2015 Systems and Information Engineering Design Symposium, 2015

The potential for developing and spreading antimicrobial resistance in pathogens is the most impo... more The potential for developing and spreading antimicrobial resistance in pathogens is the most important health risk associated with the widespread use of antimicrobials in human medication and in the livestock industry. Residual antimicrobials enter the environment through the discharge of contaminated effluent or through land application of contaminated livestock manure. Many studies have investigated the degradation of antimicrobials in water; however, soils and sediments are also an important environmental matrix as they can act as reservoirs for recalcitrant antimicrobials. This research examines the degradation kinetics of antimicrobials in soils and sediments for two processes, biodegradation and sorption. This paper makes three main research contributions. Firstly, we reviewed the literature to discuss the fate and potential adverse impacts of residual antimicrobials in the environment. Secondly, we examine the important processes governing the environmental fate and transport of residual antimicrobials to highlight trends and contributing factors. Lastly, we developed a multi-level experimental design to study the sorption and biodegradation of five priority antimicrobials (lincomycin, monensin, sulfamethazine, tetracycline, and triclosan) in soils and sediments. The results of this experimental study will be used to model the adsorption and biodegradation kinetics of the target antimicrobials. Soil and sediment samples have been collected from three pristine sites in a Southern Ontario watershed.

European heart journal cardiovascular Imaging, 2012

Haemodynamics alone do not fully explain symptoms and prognosis in clinically severe aortic steno... more Haemodynamics alone do not fully explain symptoms and prognosis in clinically severe aortic stenosis (AS). Myocardial disease, specifically diffuse myocardial fibrosis (DMF), may contribute. We used equilibrium contrast cardiovascular magnetic resonance (EQ-CMR) and sought to non-invasively measure DMF in severe AS and determine its clinical significance before and after valve replacement. Patients with severe AS underwent echocardiography, brain natriuretic peptide (BNP), 6 min walk test (6MWT), and EQ-CMR pre- (n = 63) at baseline and at 6 months post- (n = 42) aortic valve replacement (AVR). EQ-CMR was also performed in 30 normal controls. Baseline: patients with AS had more DMF than controls (18 vs. 13%, P = 0.007) with a wide range (5-38%) that overlapped controls. The extent of diffuse fibrosis correlated inversely with the 6MWT performance (r(2) = 0.22, P = 0.001). Those with severe diastolic dysfunction had more DMF (P = 0.01). On multivariable analysis, the predictors of pe...

Surgery (Oxford), 2007

Preoperative investigations in cardiac surgery can be divided into diagnostic studies and assessm... more Preoperative investigations in cardiac surgery can be divided into diagnostic studies and assessment of fitness for surgery; in general, the former are conducted by cardiologists. Increasingly, cardiac patients (particularly complex cases) are discussed at joint cardiology and cardio thoracic meetings. this contribution highlights the tests for preoperative diagnosis and assessment of fitness for surgery in adult cardiac patients. Comorbidities must be assessed to stratify risk of surgical morbidity and mortality and to allow for accurate informed consent. the results of preoperative investigations guide management decisions and predict the postoperative support required to maximize the chances of uneventful recovery.

Surgery (Oxford), 2012

Preoperative investigations in cardiac surgery can be divided into diagnostic and assessment of f... more Preoperative investigations in cardiac surgery can be divided into diagnostic and assessment of fitness for surgery. Diagnostic investigations are used to detect and evaluate coronary, valvular, myocardial and thoracic aortic disease. Knowledge of an individual patient's comorbidities is essential in determining the risk of postoperative morbidity and mortality, thus allowing for more accurate informed consent. Furthermore, the results of preoperative investigations may predict the likely postoperative hospital stay and support required in order to maximize the chances of uneventful recovery. Additionally, the changing operative demographic, with an increased age and burden of co-morbidities frequently makes open-heart surgery challenging prompting a reliance on minimally invasive procedures that may not require cardiopulmonary bypass such as transcatheter aortic valve implantation (TAVI) and mitral valve repair. This article highlights the tests for preoperative diagnosis and assessment of fitness for surgery in adult cardiac patients. They should be used to guide clinicians in making appropriate management decisions, particularly with regard to elderly, frail or complex cardiac cases discussed in the setting of joint cardiology and cardiothoracic meetings.

The Heart Surgery Forum, 2004

The endoscopic atraumatic coronary artery bypass (endo-ACAB) procedure allows single-vessel coron... more The endoscopic atraumatic coronary artery bypass (endo-ACAB) procedure allows single-vessel coronary artery bypass grafting (CABG), avoiding sternotomy or thoracotomy. We set out to define the effect of this surgical approach on postoperative recovery, blood loss, and return to work. Methods: We performed a case-control comparison of our first 29 endo-ACAB procedures for left anterior descending coronary artery (LAD) disease against 29 control patients, who underwent off-pump beating heart CABG via sternotomy for isolated LAD disease in the same institution. Control pairs were matched for age, sex, and ventricular function. Results: In a matched population, endo-ACAB is associated with shorter postoperative ventilation times (6.2 hours versus 9.0 hours, P = .034) and hospital stays (5.3 nights versus 6.4 nights, P = .04), less blood loss (363.9 mL versus 570.3 mL, P = .017), and lower transfusion requirements. Endo-ACAB patients were more likely to return to employment and did so at a mean of 6.6 weeks earlier than sternotomy patients (P = .019). Conclusions: Endo-ACAB for grafting of the left internal mammary artery to the LAD is associated with reduced blood loss and faster postoperative recovery. Avoiding sternotomy appears to be a significant factor in recovery after beating heart single-vessel CABG surgery. I N T R O D U C T I O N Minimally invasive techniques have been developed and incorporated into most surgical specialties. In cardiac surgery, endoscopically-assisted left internal thoracic artery (LITA) harvest and anterior minithoracotomy is a less invasive approach to off-pump coronary artery bypass (CAB) on the anterior and lateral heart surfaces and has evolved into the endoscopic atraumatic CAB (endo-ACAB) procedure [Vassiliades 2001]. Thoracoscopic dissection of the LITA removes the need for a large thoracotomy and painful rib retraction, which are required for open LITA harvest and identification of the left anterior descending coronary artery (LAD) in the minimally invasive direct CAB (MIDCAB) approach. Surgery for isolated LAD stenosis remains popular for several reasons. First, recent randomized trials have demonstrated reduced reintervention rates following both multiplevessel [Serruys 2001, SoS Investigators 2002] and isolated LITA-to-LAD grafting [Cisowski 2002, Diegeler 2002], compared with percutaneous stenting. In addition, some coronary lesions, particularly occluded or tortuous lesions, are difficult to treat percutaneously. A debate remains among surgeons as to the optimal surgical approach for single-vessel LITA-to-LAD off-pump CAB (OPCAB). The long-term patency of sternotomy LITA-to-LAD grafting is excellent [Lytle 1985, Fitzgibbon 1986], and equivalent early angiographic patency rates of 98% have been reported with the MIDCAB approach [Diegeler 1999]. The sternotomy approach is known to all cardiac surgeons but is associated with uncommon yet serious complications, including dehiscence and mediastinitis [Demmy 1990, Bellchambers 1999]. Endoscopic assistance has been shown to be less painful in the early postoperative period than sternotomy or MIDCAB approaches [Bucerius 2002]. However, little direct comparison of patient recovery following these alternative approaches has been reported. Since 1999, 1 surgeon at our hospital (A.D.S.) has used the endo-ACAB approach as the procedure of choice for patients referred for LITA-to-LAD grafting as part of a robotic CAB grafting development program within our hospital. We set out to determine the effect of surgical incision on postoperative recovery after beating heart surgery by performing a case-control analysis of the first 29 endo-ACAB procedures performed in our institution for single-vessel LAD disease. We used case controls drawn from our OPCAB LITA-to-LAD sternotomy patients during the same period.

The Heart Surgery Forum, 2004

Endoscopic internal thoracic artery (ITA) harvesting is employed during minimal-access coronary a... more Endoscopic internal thoracic artery (ITA) harvesting is employed during minimal-access coronary artery bypass grafting. To improve case selection, we prospectively analyzed our entire experience to identify variables that predict intraoperative conversion to sternotomy. We performed a prospective study from September 1999 to November 2003 of 100 consecutive patients with an endoscopically harvested left ITA (LITA). Success was defined as an endoscopic dissection of the LITA sufficient to reach the anastomosis. Multivariate logistic regression analysis was performed to identify independent preoperative and procedural predictors of success. The measured parameters (mean +/- SD) were age (62 +/- 9 years), height (174 +/- 9 cm), weight (81 +/- 14 kg), and logistic Euroscore (2.0 +/- 1.7). Patients comprised 8 (8%) women, 17 (17%) with urgent operations, 42 (42%) with multiple vessel disease, 17 (17%) with a left ventricular ejection fraction <50%, 2 (2%) redo procedures, and 3 (3%) with pleural disease. The Zeus robot was used in 17 patients (17%). Eight-eight (88%) of the LITA were successfully harvested endoscopically. Among the 12 patients who underwent conversions, pleural adhesions were the most common finding (n = 4, 33%). One LITA was unusable. In the final multivariate model, lung disease was a negative predictor of successful endoscopic harvest (odds ratio, 0.13; 95% confidence interval, 0.02-0.63; P =.012). The variables of age, sex, left ventricular function, logistic Euroscore, operative priority, and use of the Zeus robot did not achieve statistical significance. Acceptable conversion rates and low conduit wastage are achievable during a unit's initial experience. Lung disease is associated with increased conversion frequency, and surgeons embarking on endoscopic harvesting should consider excluding these patients to improve their chances of success. Pleural adhesions increase the technical difficulty of surgery.

The Journal of Thoracic and Cardiovascular Surgery, 2003

See related editorial on page 994. Objective: The protective effect of adenovirus-mediated ex viv... more See related editorial on page 994. Objective: The protective effect of adenovirus-mediated ex vivo multigene transfer with superoxide dismutase, a free radical scavenger, and nitric oxide, a vasodilator with anti-inflammatory properties, was examined in the rat heart during experimental ischemia-reperfusion mimicking preservation for cardiac transplantation. Methods: Donor rat hearts (n ϭ 6 per group) were perfused with solution containing adenoviral vector carrying genes for ␤-galactosidase (group A), endothelial nitric oxide synthase (group B), manganese superoxide dismutase (group C), or both endothelial nitric oxide synthase and manganese superoxide dismutase (group D). Hearts were then implanted heterotopically into the abdomens of recipient rats. Four days later, transplanted hearts were collected, connected to a Langendorff perfusion apparatus, and subjected to 6 hours of ischemia followed by 1 hour of reperfusion. Cardiac function was evaluated with an intraventricular balloon at the beginning of Langendorff perfusion and after ischemia-reperfusion. Results: Effective gene transfection was confirmed with X-gal staining in group A hearts. Positive immunoreactivity for endothelial nitric oxide synthase, manganese superoxide dismutase, or both was present predominantly in cardiomyocytes in group B, C, and D hearts. Percentage recovery of preischemic left ventricular developed pressure was 62.1% Ϯ 7.36% in group A; recoveries were increased to 79.6% Ϯ 6.4%, 86.8% Ϯ 9.1%, and 79.4% Ϯ 6.2% in groups B, C, and D, respectively. Conclusion: These results indicate that adenoviral gene transfer of manganese superoxide dismutase and endothelial nitric oxide synthase can attenuate myocardial ischemia-reperfusion injury, with the former providing the most significant protection. Combined overexpression of manganese superoxide dismutase and endothelial nitric oxide synthase did not enhance myocardial recovery any further. O xidative stress, which is associated with increased formation of reactive oxygen species, plays a major part in the pathogenesis of myocardial ischemia-reperfusion injury. 1,2 Superoxide dismutase (SOD) catalyzes the dismutation of superoxide anion to hydrogen peroxide. Three isoforms of SOD exist; copper/zinc SOD, which has a cytoplasmic location, extracellular SOD, present outside the cell, and manganese SOD (Mn-SOD), which is found in the mitochondrial matrix.

Journal of the American College of Cardiology, 2014

The study sought a prospective multicenter nonrandomized evaluation of the Direct Flow Medical (D... more The study sought a prospective multicenter nonrandomized evaluation of the Direct Flow Medical (DFM) system for the treatment of severe aortic stenosis. Background The DFM transcatheter aortic valve system is a nonmetallic design with a pressurized support structure that allows precise positioning, retrieval, and assessment of valve performance prior to permanent implantation. Methods One hundred high surgical risk patients with severe aortic stenosis were evaluated for the primary endpoint. There were 75 patients in the group evaluable for the secondary endpoints and 25 in the pre-specified roll-in training phase. Echocardiographic and angiographic data were evaluated by an independent core laboratory and adverse events adjudicated by clinical event committee and classified according to Valve Academic Research Consortium (VARC) criteria. Results There was 99% freedom from all cause mortality at 30 days (primary endpoint). VARC criteria defined 30 day combined freedom from patient safety event rate was 91% and overall device success was 93%. The postimplantation echocardiography results demonstrated mild or no aortic regurgitation in 99% (73 of 74) with a mean gradient of 12.6 AE 7.1 mm Hg (n ¼ 72) and effective orifice area of 1.50 AE 0.56 cm 2 and New York Heart Association functional class was I or II in 92% of cases. Conclusions The present study demonstrates the safety and efficacy of the DFM system in surgical high risk patients with severe aortic stenosis and complex anatomy aortic regurgitation was less than moderate in 99% of patients. (J Am Coll Cardiol 2014;63:763-8) ª 2014 by the American College of Cardiology Foundation Transcatheter aortic valve replacement has been successfully applied to high risk patients with symptomatic aortic stenosis (1,2). Currently available devices include the inability to fully reposition or remove it after deployment. Misplacement of the valve can result in severe complications (3,4).

Journal of Molecular and Cellular Cardiology, 2009

Experimental studies suggest that cardioprotection can be achieved through either the activation ... more Experimental studies suggest that cardioprotection can be achieved through either the activation of PKC-ɛ prior to the index ischaemic episode or the inhibition of PKC-δ at the onset of reperfusion. However, whether these PKC isoforms exert such divergent roles in human myocardium, subjected to simulated ischaemiareperfusion injury, is unclear. Human atrial trabeculae were isolated from right atrial appendages harvested from patients undergoing elective cardiac surgery. These were subjected to 90 min of hypoxia followed by 120 min of reoxygenation, at the end of which the recovery of baseline contractile function was determined. Atrial trabeculae were randomised to receive various treatment protocols comprising a peptide activator of PKC-ɛ, a peptide inhibitor of PKC-δ and their respective inactive control peptides. Administering the PKC-δ peptide inhibitor at reoxygenation improved the recovery of function at all the concentrations tested (39.3 ± 1.4% at 5 nM, 52.4 ± 2.9% at 50 nM and 46.8 ± 2.9% at 500 nM versus the control group, 27.5 ± 1.4%: N ≥ 6/ group: P b 0.02). Preconditioning with the PKC-ɛ peptide activator improved the recovery of function (40.0 ± 0.8% at 50 nM and 49.7 ± 3.1% at 500 nM versus the control group 27.5 ± 1.4%: N ≥ 6/group: P b 0.02). This cardioprotective effect was comparable to that achieved by a standard hypoxic preconditioning protocol (52.3 ± 3.2%). Interestingly, administering the PKC-ɛ activator (500 nM) at the onset of reperfusion also improved the recovery of contractile function (40.7 ± 2.1% versus 27.5 ± 1.5%: N ≥ 6/group: P b 0.05). In human myocardium, cardioprotection can be achieved by either inhibiting PKC-δ or activating PKC-ɛ at the onset of reperfusion. In addition, PKC-ɛ activation offers cardioprotection when administered as a preconditioning strategy.

European Journal of Cardio-Thoracic Surgery, 2001

Objective: Both superoxide dismutase (SOD), a free radical scavenger, and nitric oxide (NO), a va... more Objective: Both superoxide dismutase (SOD), a free radical scavenger, and nitric oxide (NO), a vasodilator with anti-in¯ammatory properties, have been shown to protect the myocardium from reperfusion injury. They are known to interact in vivo, the in¯uence of which on myocardial protection has not been studied. Methods: Four groups of rats (n 7, per group) were subjected to experimental infarction following injections into the anterior wall of the left ventricle with adenoviral vector encoding b-galactosidase (group A), eNOS (group B), Mn-SOD (group C) and both eNOS and MnSOD (group D). Hearts were assessed for protein expression and size of infarction. Results: Ef®ciency of gene up regulation was con®rmed by immunostaining for eNOS and Mn-SOD, and X-gal staining for b-gal respectively. In B and D, overexpression of eNOS was demonstrated in cardiac myocytes in addition to that in the endothelium, while in C and D, Mn-SOD was overexpressed in mainly cardiomyocytes. Infarct size was 49.7^4.8% in A, and was signi®cantly reduced in the other groups (29.8^2.7%, 21.8^2.5% and 24.9^2.4% in B, C and D respectively). Conclusion: Adenoviral gene transfer of Mn-SOD was superior to eNOS in reducing the extent of in vivo ischemia-reperfusion injury in the rat heart in our model. The effect of combined application of Mn-SOD and eNOS was not different from their individual effect.

Basic Research in Cardiology, 2011

The acute administration of atorvastatin has been reported to reduce myocardial infarct size in a... more The acute administration of atorvastatin has been reported to reduce myocardial infarct size in animal studies. However, this cardioprotective effect is lost with the chronic administration of atorvastatin, although it can be recaptured by administering an acute high-dose of atorvastatin. We hypothesised that pre-treatment with highdose atorvastatin, on a background of chronic standard 'statin' therapy, would reduce myocardial injury in patients undergoing elective coronary artery bypass graft (CABG) surgery. One hundred and one consenting patients undergoing elective CABG surgery at a single tertiary cardiac centre were recruited into two randomised controlled, single-blinded clinical studies. Study 1: 45 patients were randomised to receive either 160 mg of atorvastatin 2 h preoperatively and 24 h following surgery or their standard statin therapy. Study 2: 56 patients were randomised to receive either 160 mg of atorvastatin 12 h preoperatively and 24 h following surgery or their standard statin therapy. Blood samples for troponin T and creatine kinase were taken prior to surgery and then at 6, 12, 24, 48 and 72 h post-surgery. Cardiac enzyme levels at each time point and the total area-under curve (AUC) were calculated. The group characteristics and surgical methods were well matched. High-dose atorvastatin was not associated with any significant side effects. There was no significant difference in serum troponin T or creatine kinase in either study at each time point or over 72 h.

Asian Cardiovascular and Thoracic Annals, 2005

Primary intracardiac malignant mesotheliomas are extremely rare and carry a very poor prognosis. ... more Primary intracardiac malignant mesotheliomas are extremely rare and carry a very poor prognosis. We present such a case where the lesion encompassed two chambers, the left atrium and ventricle, with no pericardial involvement. Initial echocardiography mimicked a myxoma, and urgent surgical intervention was required in view of significant cardiorespiratory compromise. To the best of our knowledge this is the first case of a primary two-chamber intracardiac malignant sarcomatoid mesothelioma.

The Annals of Thoracic Surgery, 1999

We report a case of symptomatic partial vascular ring that to our knowledge has not been previous... more We report a case of symptomatic partial vascular ring that to our knowledge has not been previously described. This anomaly includes a right aortic arch with an aberrant left subclavian artery and an atypical origin of the right subclavian artery.

Journal of Cardiothoracic Surgery, 2013

Previous study suggested semi continuous technique increases the risk of re-operation for parapro... more Previous study suggested semi continuous technique increases the risk of re-operation for paraprosthetic leak AVR compared with interrupted suture technique. We aim to evaluate our experience in these two techniques performed in our institution.

Background: There has been a dearth of collaborative learning across tertiary institutions due to... more Background: There has been a dearth of collaborative learning across tertiary institutions due to challenges in scheduling and geographical locations. Three dimensional virtual environments are a viable and innovative tool to bring diverse healthcare students to learn together. Objective: The purpose of this study is to describe the development of a multiuser virtual environment and to evaluate healthcare students' experiences of their collaborative learning in the environment. Methods: A mixed method study design was employed. Participants from six healthcare courses (Medicine, Nursing, Pharmacy, Physiotherapy, Occupational Therapy, and Medical Social Work) were recruited from three institutions to form six interprofessional healthcare teams who participated in interdisciplinary team care via a virtual environment. Four focus groups were conducted with 27 healthcare students after they completed questionnaires to evaluate their perceived usability, the sociability of computer-supported collaborative learning, and senses of presence. Interview transcripts were analyzed using thematic analysis. Results: Four themes emerged from the students' experiences: "Bringing everyone together" to learn in the virtual platform was perceived as a valuable experience; "Feeling real", whereby the students felt immersed in their own healthcare profession's roles; learning in the virtual environment was perceived as "less threatening" compared to face-to-face interactions; and there were some "technical hiccups" related to sound quality and navigation. The participants reported positively on the usability (mean 3.48, SD 0.64) and feasibility (mean 3.39, SD 0.60) of the virtual environment in supporting collaborative learning. With a maximum score of 168, they also perceived a moderately strong sense of presence (mean 107.24, SD 17.78) in the environment. Conclusion: This study provides evidence for the acceptance of a virtual platform for collaborative learning in team care delivery. Given its flexibility, practicality, and scalability, this virtual platform serves as a promising tool for collaborative learning across different healthcare courses and institutions.

Journal of Medical Internet Research, 2019

?hl=en_US&formkey=dGl… 5/41 yes: all primary outcomes were signi cantly better in intervention gr... more ?hl=en_US&formkey=dGl… 5/41 yes: all primary outcomes were signi cantly better in intervention group vs control partly: SOME primary outcomes were signi cantly better in intervention group vs control no statistically signi cant difference between control and intervention potentially harmful: control was signi cantly better than intervention in one or more outcomes

EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology, Jan 18, 2016

The aim of this study was to introduce and demonstrate the feasibility in an acute preclinical mo... more The aim of this study was to introduce and demonstrate the feasibility in an acute preclinical model of a new transcatheter heart valve concept with a self-expanding wire frame, polymeric leaflets and a sealing component. The TRISKELE valve was developed based on a previously validated polymeric leaflet design, an adaptive sealing cuff and a novel nitinol wire frame which reduces stress on the leaflets and radial pressure on the surrounding tissue. A valve prototype of 26 mm nominal diameter was manufactured by automated dip coating of a biostable polymer. The prototype was implanted via brachiocephalic approach in orthotopic position in an acute ovine model through a highly controllable multistage deployment process. The atraumatic retrievability of the valve after full expansion was verified in situ before final release in the optimal position. Observation indicated secure valve anchoring, adequate leaflet motion, and no interference of coronary flow or mitral valve function. The ...

Intensive care medicine, Jan 3, 2015

2015 Systems and Information Engineering Design Symposium, 2015

The potential for developing and spreading antimicrobial resistance in pathogens is the most impo... more The potential for developing and spreading antimicrobial resistance in pathogens is the most important health risk associated with the widespread use of antimicrobials in human medication and in the livestock industry. Residual antimicrobials enter the environment through the discharge of contaminated effluent or through land application of contaminated livestock manure. Many studies have investigated the degradation of antimicrobials in water; however, soils and sediments are also an important environmental matrix as they can act as reservoirs for recalcitrant antimicrobials. This research examines the degradation kinetics of antimicrobials in soils and sediments for two processes, biodegradation and sorption. This paper makes three main research contributions. Firstly, we reviewed the literature to discuss the fate and potential adverse impacts of residual antimicrobials in the environment. Secondly, we examine the important processes governing the environmental fate and transport of residual antimicrobials to highlight trends and contributing factors. Lastly, we developed a multi-level experimental design to study the sorption and biodegradation of five priority antimicrobials (lincomycin, monensin, sulfamethazine, tetracycline, and triclosan) in soils and sediments. The results of this experimental study will be used to model the adsorption and biodegradation kinetics of the target antimicrobials. Soil and sediment samples have been collected from three pristine sites in a Southern Ontario watershed.

European heart journal cardiovascular Imaging, 2012

Haemodynamics alone do not fully explain symptoms and prognosis in clinically severe aortic steno... more Haemodynamics alone do not fully explain symptoms and prognosis in clinically severe aortic stenosis (AS). Myocardial disease, specifically diffuse myocardial fibrosis (DMF), may contribute. We used equilibrium contrast cardiovascular magnetic resonance (EQ-CMR) and sought to non-invasively measure DMF in severe AS and determine its clinical significance before and after valve replacement. Patients with severe AS underwent echocardiography, brain natriuretic peptide (BNP), 6 min walk test (6MWT), and EQ-CMR pre- (n = 63) at baseline and at 6 months post- (n = 42) aortic valve replacement (AVR). EQ-CMR was also performed in 30 normal controls. Baseline: patients with AS had more DMF than controls (18 vs. 13%, P = 0.007) with a wide range (5-38%) that overlapped controls. The extent of diffuse fibrosis correlated inversely with the 6MWT performance (r(2) = 0.22, P = 0.001). Those with severe diastolic dysfunction had more DMF (P = 0.01). On multivariable analysis, the predictors of pe...

Surgery (Oxford), 2007

Preoperative investigations in cardiac surgery can be divided into diagnostic studies and assessm... more Preoperative investigations in cardiac surgery can be divided into diagnostic studies and assessment of fitness for surgery; in general, the former are conducted by cardiologists. Increasingly, cardiac patients (particularly complex cases) are discussed at joint cardiology and cardio thoracic meetings. this contribution highlights the tests for preoperative diagnosis and assessment of fitness for surgery in adult cardiac patients. Comorbidities must be assessed to stratify risk of surgical morbidity and mortality and to allow for accurate informed consent. the results of preoperative investigations guide management decisions and predict the postoperative support required to maximize the chances of uneventful recovery.

Surgery (Oxford), 2012

Preoperative investigations in cardiac surgery can be divided into diagnostic and assessment of f... more Preoperative investigations in cardiac surgery can be divided into diagnostic and assessment of fitness for surgery. Diagnostic investigations are used to detect and evaluate coronary, valvular, myocardial and thoracic aortic disease. Knowledge of an individual patient's comorbidities is essential in determining the risk of postoperative morbidity and mortality, thus allowing for more accurate informed consent. Furthermore, the results of preoperative investigations may predict the likely postoperative hospital stay and support required in order to maximize the chances of uneventful recovery. Additionally, the changing operative demographic, with an increased age and burden of co-morbidities frequently makes open-heart surgery challenging prompting a reliance on minimally invasive procedures that may not require cardiopulmonary bypass such as transcatheter aortic valve implantation (TAVI) and mitral valve repair. This article highlights the tests for preoperative diagnosis and assessment of fitness for surgery in adult cardiac patients. They should be used to guide clinicians in making appropriate management decisions, particularly with regard to elderly, frail or complex cardiac cases discussed in the setting of joint cardiology and cardiothoracic meetings.

The Heart Surgery Forum, 2004

The endoscopic atraumatic coronary artery bypass (endo-ACAB) procedure allows single-vessel coron... more The endoscopic atraumatic coronary artery bypass (endo-ACAB) procedure allows single-vessel coronary artery bypass grafting (CABG), avoiding sternotomy or thoracotomy. We set out to define the effect of this surgical approach on postoperative recovery, blood loss, and return to work. Methods: We performed a case-control comparison of our first 29 endo-ACAB procedures for left anterior descending coronary artery (LAD) disease against 29 control patients, who underwent off-pump beating heart CABG via sternotomy for isolated LAD disease in the same institution. Control pairs were matched for age, sex, and ventricular function. Results: In a matched population, endo-ACAB is associated with shorter postoperative ventilation times (6.2 hours versus 9.0 hours, P = .034) and hospital stays (5.3 nights versus 6.4 nights, P = .04), less blood loss (363.9 mL versus 570.3 mL, P = .017), and lower transfusion requirements. Endo-ACAB patients were more likely to return to employment and did so at a mean of 6.6 weeks earlier than sternotomy patients (P = .019). Conclusions: Endo-ACAB for grafting of the left internal mammary artery to the LAD is associated with reduced blood loss and faster postoperative recovery. Avoiding sternotomy appears to be a significant factor in recovery after beating heart single-vessel CABG surgery. I N T R O D U C T I O N Minimally invasive techniques have been developed and incorporated into most surgical specialties. In cardiac surgery, endoscopically-assisted left internal thoracic artery (LITA) harvest and anterior minithoracotomy is a less invasive approach to off-pump coronary artery bypass (CAB) on the anterior and lateral heart surfaces and has evolved into the endoscopic atraumatic CAB (endo-ACAB) procedure [Vassiliades 2001]. Thoracoscopic dissection of the LITA removes the need for a large thoracotomy and painful rib retraction, which are required for open LITA harvest and identification of the left anterior descending coronary artery (LAD) in the minimally invasive direct CAB (MIDCAB) approach. Surgery for isolated LAD stenosis remains popular for several reasons. First, recent randomized trials have demonstrated reduced reintervention rates following both multiplevessel [Serruys 2001, SoS Investigators 2002] and isolated LITA-to-LAD grafting [Cisowski 2002, Diegeler 2002], compared with percutaneous stenting. In addition, some coronary lesions, particularly occluded or tortuous lesions, are difficult to treat percutaneously. A debate remains among surgeons as to the optimal surgical approach for single-vessel LITA-to-LAD off-pump CAB (OPCAB). The long-term patency of sternotomy LITA-to-LAD grafting is excellent [Lytle 1985, Fitzgibbon 1986], and equivalent early angiographic patency rates of 98% have been reported with the MIDCAB approach [Diegeler 1999]. The sternotomy approach is known to all cardiac surgeons but is associated with uncommon yet serious complications, including dehiscence and mediastinitis [Demmy 1990, Bellchambers 1999]. Endoscopic assistance has been shown to be less painful in the early postoperative period than sternotomy or MIDCAB approaches [Bucerius 2002]. However, little direct comparison of patient recovery following these alternative approaches has been reported. Since 1999, 1 surgeon at our hospital (A.D.S.) has used the endo-ACAB approach as the procedure of choice for patients referred for LITA-to-LAD grafting as part of a robotic CAB grafting development program within our hospital. We set out to determine the effect of surgical incision on postoperative recovery after beating heart surgery by performing a case-control analysis of the first 29 endo-ACAB procedures performed in our institution for single-vessel LAD disease. We used case controls drawn from our OPCAB LITA-to-LAD sternotomy patients during the same period.

The Heart Surgery Forum, 2004

Endoscopic internal thoracic artery (ITA) harvesting is employed during minimal-access coronary a... more Endoscopic internal thoracic artery (ITA) harvesting is employed during minimal-access coronary artery bypass grafting. To improve case selection, we prospectively analyzed our entire experience to identify variables that predict intraoperative conversion to sternotomy. We performed a prospective study from September 1999 to November 2003 of 100 consecutive patients with an endoscopically harvested left ITA (LITA). Success was defined as an endoscopic dissection of the LITA sufficient to reach the anastomosis. Multivariate logistic regression analysis was performed to identify independent preoperative and procedural predictors of success. The measured parameters (mean +/- SD) were age (62 +/- 9 years), height (174 +/- 9 cm), weight (81 +/- 14 kg), and logistic Euroscore (2.0 +/- 1.7). Patients comprised 8 (8%) women, 17 (17%) with urgent operations, 42 (42%) with multiple vessel disease, 17 (17%) with a left ventricular ejection fraction <50%, 2 (2%) redo procedures, and 3 (3%) with pleural disease. The Zeus robot was used in 17 patients (17%). Eight-eight (88%) of the LITA were successfully harvested endoscopically. Among the 12 patients who underwent conversions, pleural adhesions were the most common finding (n = 4, 33%). One LITA was unusable. In the final multivariate model, lung disease was a negative predictor of successful endoscopic harvest (odds ratio, 0.13; 95% confidence interval, 0.02-0.63; P =.012). The variables of age, sex, left ventricular function, logistic Euroscore, operative priority, and use of the Zeus robot did not achieve statistical significance. Acceptable conversion rates and low conduit wastage are achievable during a unit's initial experience. Lung disease is associated with increased conversion frequency, and surgeons embarking on endoscopic harvesting should consider excluding these patients to improve their chances of success. Pleural adhesions increase the technical difficulty of surgery.

The Journal of Thoracic and Cardiovascular Surgery, 2003

See related editorial on page 994. Objective: The protective effect of adenovirus-mediated ex viv... more See related editorial on page 994. Objective: The protective effect of adenovirus-mediated ex vivo multigene transfer with superoxide dismutase, a free radical scavenger, and nitric oxide, a vasodilator with anti-inflammatory properties, was examined in the rat heart during experimental ischemia-reperfusion mimicking preservation for cardiac transplantation. Methods: Donor rat hearts (n ϭ 6 per group) were perfused with solution containing adenoviral vector carrying genes for ␤-galactosidase (group A), endothelial nitric oxide synthase (group B), manganese superoxide dismutase (group C), or both endothelial nitric oxide synthase and manganese superoxide dismutase (group D). Hearts were then implanted heterotopically into the abdomens of recipient rats. Four days later, transplanted hearts were collected, connected to a Langendorff perfusion apparatus, and subjected to 6 hours of ischemia followed by 1 hour of reperfusion. Cardiac function was evaluated with an intraventricular balloon at the beginning of Langendorff perfusion and after ischemia-reperfusion. Results: Effective gene transfection was confirmed with X-gal staining in group A hearts. Positive immunoreactivity for endothelial nitric oxide synthase, manganese superoxide dismutase, or both was present predominantly in cardiomyocytes in group B, C, and D hearts. Percentage recovery of preischemic left ventricular developed pressure was 62.1% Ϯ 7.36% in group A; recoveries were increased to 79.6% Ϯ 6.4%, 86.8% Ϯ 9.1%, and 79.4% Ϯ 6.2% in groups B, C, and D, respectively. Conclusion: These results indicate that adenoviral gene transfer of manganese superoxide dismutase and endothelial nitric oxide synthase can attenuate myocardial ischemia-reperfusion injury, with the former providing the most significant protection. Combined overexpression of manganese superoxide dismutase and endothelial nitric oxide synthase did not enhance myocardial recovery any further. O xidative stress, which is associated with increased formation of reactive oxygen species, plays a major part in the pathogenesis of myocardial ischemia-reperfusion injury. 1,2 Superoxide dismutase (SOD) catalyzes the dismutation of superoxide anion to hydrogen peroxide. Three isoforms of SOD exist; copper/zinc SOD, which has a cytoplasmic location, extracellular SOD, present outside the cell, and manganese SOD (Mn-SOD), which is found in the mitochondrial matrix.

Journal of the American College of Cardiology, 2014

The study sought a prospective multicenter nonrandomized evaluation of the Direct Flow Medical (D... more The study sought a prospective multicenter nonrandomized evaluation of the Direct Flow Medical (DFM) system for the treatment of severe aortic stenosis. Background The DFM transcatheter aortic valve system is a nonmetallic design with a pressurized support structure that allows precise positioning, retrieval, and assessment of valve performance prior to permanent implantation. Methods One hundred high surgical risk patients with severe aortic stenosis were evaluated for the primary endpoint. There were 75 patients in the group evaluable for the secondary endpoints and 25 in the pre-specified roll-in training phase. Echocardiographic and angiographic data were evaluated by an independent core laboratory and adverse events adjudicated by clinical event committee and classified according to Valve Academic Research Consortium (VARC) criteria. Results There was 99% freedom from all cause mortality at 30 days (primary endpoint). VARC criteria defined 30 day combined freedom from patient safety event rate was 91% and overall device success was 93%. The postimplantation echocardiography results demonstrated mild or no aortic regurgitation in 99% (73 of 74) with a mean gradient of 12.6 AE 7.1 mm Hg (n ¼ 72) and effective orifice area of 1.50 AE 0.56 cm 2 and New York Heart Association functional class was I or II in 92% of cases. Conclusions The present study demonstrates the safety and efficacy of the DFM system in surgical high risk patients with severe aortic stenosis and complex anatomy aortic regurgitation was less than moderate in 99% of patients. (J Am Coll Cardiol 2014;63:763-8) ª 2014 by the American College of Cardiology Foundation Transcatheter aortic valve replacement has been successfully applied to high risk patients with symptomatic aortic stenosis (1,2). Currently available devices include the inability to fully reposition or remove it after deployment. Misplacement of the valve can result in severe complications (3,4).

Journal of Molecular and Cellular Cardiology, 2009

Experimental studies suggest that cardioprotection can be achieved through either the activation ... more Experimental studies suggest that cardioprotection can be achieved through either the activation of PKC-ɛ prior to the index ischaemic episode or the inhibition of PKC-δ at the onset of reperfusion. However, whether these PKC isoforms exert such divergent roles in human myocardium, subjected to simulated ischaemiareperfusion injury, is unclear. Human atrial trabeculae were isolated from right atrial appendages harvested from patients undergoing elective cardiac surgery. These were subjected to 90 min of hypoxia followed by 120 min of reoxygenation, at the end of which the recovery of baseline contractile function was determined. Atrial trabeculae were randomised to receive various treatment protocols comprising a peptide activator of PKC-ɛ, a peptide inhibitor of PKC-δ and their respective inactive control peptides. Administering the PKC-δ peptide inhibitor at reoxygenation improved the recovery of function at all the concentrations tested (39.3 ± 1.4% at 5 nM, 52.4 ± 2.9% at 50 nM and 46.8 ± 2.9% at 500 nM versus the control group, 27.5 ± 1.4%: N ≥ 6/ group: P b 0.02). Preconditioning with the PKC-ɛ peptide activator improved the recovery of function (40.0 ± 0.8% at 50 nM and 49.7 ± 3.1% at 500 nM versus the control group 27.5 ± 1.4%: N ≥ 6/group: P b 0.02). This cardioprotective effect was comparable to that achieved by a standard hypoxic preconditioning protocol (52.3 ± 3.2%). Interestingly, administering the PKC-ɛ activator (500 nM) at the onset of reperfusion also improved the recovery of contractile function (40.7 ± 2.1% versus 27.5 ± 1.5%: N ≥ 6/group: P b 0.05). In human myocardium, cardioprotection can be achieved by either inhibiting PKC-δ or activating PKC-ɛ at the onset of reperfusion. In addition, PKC-ɛ activation offers cardioprotection when administered as a preconditioning strategy.

European Journal of Cardio-Thoracic Surgery, 2001

Objective: Both superoxide dismutase (SOD), a free radical scavenger, and nitric oxide (NO), a va... more Objective: Both superoxide dismutase (SOD), a free radical scavenger, and nitric oxide (NO), a vasodilator with anti-in¯ammatory properties, have been shown to protect the myocardium from reperfusion injury. They are known to interact in vivo, the in¯uence of which on myocardial protection has not been studied. Methods: Four groups of rats (n 7, per group) were subjected to experimental infarction following injections into the anterior wall of the left ventricle with adenoviral vector encoding b-galactosidase (group A), eNOS (group B), Mn-SOD (group C) and both eNOS and MnSOD (group D). Hearts were assessed for protein expression and size of infarction. Results: Ef®ciency of gene up regulation was con®rmed by immunostaining for eNOS and Mn-SOD, and X-gal staining for b-gal respectively. In B and D, overexpression of eNOS was demonstrated in cardiac myocytes in addition to that in the endothelium, while in C and D, Mn-SOD was overexpressed in mainly cardiomyocytes. Infarct size was 49.7^4.8% in A, and was signi®cantly reduced in the other groups (29.8^2.7%, 21.8^2.5% and 24.9^2.4% in B, C and D respectively). Conclusion: Adenoviral gene transfer of Mn-SOD was superior to eNOS in reducing the extent of in vivo ischemia-reperfusion injury in the rat heart in our model. The effect of combined application of Mn-SOD and eNOS was not different from their individual effect.

Basic Research in Cardiology, 2011

The acute administration of atorvastatin has been reported to reduce myocardial infarct size in a... more The acute administration of atorvastatin has been reported to reduce myocardial infarct size in animal studies. However, this cardioprotective effect is lost with the chronic administration of atorvastatin, although it can be recaptured by administering an acute high-dose of atorvastatin. We hypothesised that pre-treatment with highdose atorvastatin, on a background of chronic standard 'statin' therapy, would reduce myocardial injury in patients undergoing elective coronary artery bypass graft (CABG) surgery. One hundred and one consenting patients undergoing elective CABG surgery at a single tertiary cardiac centre were recruited into two randomised controlled, single-blinded clinical studies. Study 1: 45 patients were randomised to receive either 160 mg of atorvastatin 2 h preoperatively and 24 h following surgery or their standard statin therapy. Study 2: 56 patients were randomised to receive either 160 mg of atorvastatin 12 h preoperatively and 24 h following surgery or their standard statin therapy. Blood samples for troponin T and creatine kinase were taken prior to surgery and then at 6, 12, 24, 48 and 72 h post-surgery. Cardiac enzyme levels at each time point and the total area-under curve (AUC) were calculated. The group characteristics and surgical methods were well matched. High-dose atorvastatin was not associated with any significant side effects. There was no significant difference in serum troponin T or creatine kinase in either study at each time point or over 72 h.

Asian Cardiovascular and Thoracic Annals, 2005

Primary intracardiac malignant mesotheliomas are extremely rare and carry a very poor prognosis. ... more Primary intracardiac malignant mesotheliomas are extremely rare and carry a very poor prognosis. We present such a case where the lesion encompassed two chambers, the left atrium and ventricle, with no pericardial involvement. Initial echocardiography mimicked a myxoma, and urgent surgical intervention was required in view of significant cardiorespiratory compromise. To the best of our knowledge this is the first case of a primary two-chamber intracardiac malignant sarcomatoid mesothelioma.

The Annals of Thoracic Surgery, 1999

We report a case of symptomatic partial vascular ring that to our knowledge has not been previous... more We report a case of symptomatic partial vascular ring that to our knowledge has not been previously described. This anomaly includes a right aortic arch with an aberrant left subclavian artery and an atypical origin of the right subclavian artery.

Journal of Cardiothoracic Surgery, 2013

Previous study suggested semi continuous technique increases the risk of re-operation for parapro... more Previous study suggested semi continuous technique increases the risk of re-operation for paraprosthetic leak AVR compared with interrupted suture technique. We aim to evaluate our experience in these two techniques performed in our institution.