Thành Phan - Academia.edu (original) (raw)

Papers by Thành Phan

Research paper thumbnail of The pathophysiology of diastolic heart failure

F1000 Biology Reports, 2010

Whilst resting disturbances of both diastolic and long-axis systolic function are observed in pat... more Whilst resting disturbances of both diastolic and long-axis systolic function are observed in patients with heart failure who have normal left ventricular ejection fraction, recent evidence suggests that dynamic disturbances in cardiac function occur during exercise. A paradoxical slowing of left ventricular active relaxation during exercise limits cardiac filling and therefore stroke volume and appears to be due to the combination of cardiac energetic impairment and disturbed ventricularvascular coupling.

Research paper thumbnail of The pathophysiology of diastolic heart failure

F1000 Biology Reports, 2010

Whilst resting disturbances of both diastolic and long-axis systolic function are observed in pat... more Whilst resting disturbances of both diastolic and long-axis systolic function are observed in patients with heart failure who have normal left ventricular ejection fraction, recent evidence suggests that dynamic disturbances in cardiac function occur during exercise. A paradoxical slowing of left ventricular active relaxation during exercise limits cardiac filling and therefore stroke volume and appears to be due to the combination of cardiac energetic impairment and disturbed ventricularvascular coupling.

Research paper thumbnail of 31P magnetic resonance spectroscopy to measure in vivo cardiac energetics in normal myocardium and hypertrophic cardiomyopathy: Experiences at 3 T

European Journal of Radiology, 2010

31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kin... more 31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kinetics in the myocardium. While traditionally 31P cardiac spectroscopy is performed at 1.5 T, cardiac MRS at higher field strength can theoretically increase signal to noise ratio (SNR) and spectral resolution therefore improving sensitivity and specificity of the cardiac spectra. The reproducibility and feasibility of performing cardiac spectroscopy at 3 T is presented here in this study in healthy volunteers and patients with hypertrophic cardiomyopathy.Cardiac spectroscopy was performed using a Phillips 3T Achieva scanner in 37 healthy volunteers and 26 patients with hypertrophic cardiomyopathy (HCM) to test the feasibility of the protocol. To test the reproducibility a single volunteer was scanned eight times on separate occasions. A single voxel 31P MRS was performed using Image Selected In vivo Spectroscopy (ISIS) volume localization.The mean phosphocreatine/adenosine triphosphate (PCr/ATP) ratio of the eight measurements performed on one individual was 2.11 ± 0.25. Bland Altman plots showed a variance of 12% in the measurement of PCr/ATP ratios. The PCr/ATP ratio was significantly reduced in HCM patients compared to controls, 1.42 ± 0.51 and 2.11 ± 0.57, respectively, P < 0.0001. (All results are expressed as mean ± standard deviation).Here we demonstrate that cardiac 31P MRS at 3 T is a reliable method of measuring in vivo high-energy phosphate kinetics in the myocardium for clinical studies and diagnostics. Based on our data an impairment of cardiac energetic state in patients with hypertrophic cardiomyopathy is indisputable.

Research paper thumbnail of 31P magnetic resonance spectroscopy to measure in vivo cardiac energetics in normal myocardium and hypertrophic cardiomyopathy: Experiences at 3 T

European Journal of Radiology, 2010

31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kin... more 31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kinetics in the myocardium. While traditionally 31P cardiac spectroscopy is performed at 1.5 T, cardiac MRS at higher field strength can theoretically increase signal to noise ratio (SNR) and spectral resolution therefore improving sensitivity and specificity of the cardiac spectra. The reproducibility and feasibility of performing cardiac spectroscopy at 3 T is presented here in this study in healthy volunteers and patients with hypertrophic cardiomyopathy.Cardiac spectroscopy was performed using a Phillips 3T Achieva scanner in 37 healthy volunteers and 26 patients with hypertrophic cardiomyopathy (HCM) to test the feasibility of the protocol. To test the reproducibility a single volunteer was scanned eight times on separate occasions. A single voxel 31P MRS was performed using Image Selected In vivo Spectroscopy (ISIS) volume localization.The mean phosphocreatine/adenosine triphosphate (PCr/ATP) ratio of the eight measurements performed on one individual was 2.11 ± 0.25. Bland Altman plots showed a variance of 12% in the measurement of PCr/ATP ratios. The PCr/ATP ratio was significantly reduced in HCM patients compared to controls, 1.42 ± 0.51 and 2.11 ± 0.57, respectively, P < 0.0001. (All results are expressed as mean ± standard deviation).Here we demonstrate that cardiac 31P MRS at 3 T is a reliable method of measuring in vivo high-energy phosphate kinetics in the myocardium for clinical studies and diagnostics. Based on our data an impairment of cardiac energetic state in patients with hypertrophic cardiomyopathy is indisputable.

Research paper thumbnail of Heart Failure With Preserved Ejection Fraction Is Characterized by Dynamic Impairment of Active Relaxation and Contraction of the Left Ventricle on Exercise and Associated With Myocardial Energy Deficiency

Journal of The American College of Cardiology, 2009

We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation an... more We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation and of LV contractile function and vasculoventricular coupling (VVC) in the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and to assess myocardial energetic status in these patients.To date, no studies have investigated exercise-related changes in LV relaxation and VVC as well as in vivo myocardial energetic status in patients with HFpEF.We studied 37 patients with HFpEF and 20 control subjects. The VVC and time to peak LV filling (nTTPF, a measure of LV active relaxation) were assessed while patients were at rest and during exercise by the use of radionuclide ventriculography. Cardiac energetic status (creatine phosphate/adenosine triphosphate ratio) was assessed by the use of 31P magnetic resonance spectroscopy at 3-T.When patients were at rest, nTTPF and VVC were similar in patients with HFpEF and control subjects. The cardiac creatine phosphate/adenosine triphosphate ratio was reduced in patients with HFpEF versus control subjects (1.57 ± 0.52 vs. 2.14 ± 0.63; p = 0.003), indicating reduced energy reserves. Peak maximal oxygen uptake and the increase in heart rate during maximal exercise were lower in patients with HFpEF versus control subjects (19 ± 4 ml/kg/min vs. 36 ± 8 ml/kg/min, p < 0.001, and 52 ± 16 beats/min vs. 81 ± 14 beats/min, p < 0.001). The relative changes in stroke volume and cardiac output during submaximal exercise were lower in patients with HFpEF versus control subjects (ratio exercise/rest: 0.99 ± 0.34 vs. 1.25 ± 0.47, p = 0.04, and 1.36 ± 0.45 vs. 2.13 ± 0.72, p < 0.001). The nTTPF decreased during exercise in control subjects but increased in patients with HFpEF (−0.03 ± 12 s vs. +0.07 ± 0.11 s; p = 0.005). The VVC decreased on exercise in control subjects but was unchanged in patients with HFpEF (−0.01 ± 0.15 vs. −0.25 ± 0.19; p < 0.001).Patients with HFpEF have reduced cardiac energetic reserve that may underlie marked dynamic slowing of LV active relaxation and abnormal VVC during exercise.

Research paper thumbnail of Heart Failure With Preserved Ejection Fraction Is Characterized by Dynamic Impairment of Active Relaxation and Contraction of the Left Ventricle on Exercise and Associated With Myocardial Energy Deficiency

Journal of The American College of Cardiology, 2009

We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation an... more We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation and of LV contractile function and vasculoventricular coupling (VVC) in the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and to assess myocardial energetic status in these patients.To date, no studies have investigated exercise-related changes in LV relaxation and VVC as well as in vivo myocardial energetic status in patients with HFpEF.We studied 37 patients with HFpEF and 20 control subjects. The VVC and time to peak LV filling (nTTPF, a measure of LV active relaxation) were assessed while patients were at rest and during exercise by the use of radionuclide ventriculography. Cardiac energetic status (creatine phosphate/adenosine triphosphate ratio) was assessed by the use of 31P magnetic resonance spectroscopy at 3-T.When patients were at rest, nTTPF and VVC were similar in patients with HFpEF and control subjects. The cardiac creatine phosphate/adenosine triphosphate ratio was reduced in patients with HFpEF versus control subjects (1.57 ± 0.52 vs. 2.14 ± 0.63; p = 0.003), indicating reduced energy reserves. Peak maximal oxygen uptake and the increase in heart rate during maximal exercise were lower in patients with HFpEF versus control subjects (19 ± 4 ml/kg/min vs. 36 ± 8 ml/kg/min, p < 0.001, and 52 ± 16 beats/min vs. 81 ± 14 beats/min, p < 0.001). The relative changes in stroke volume and cardiac output during submaximal exercise were lower in patients with HFpEF versus control subjects (ratio exercise/rest: 0.99 ± 0.34 vs. 1.25 ± 0.47, p = 0.04, and 1.36 ± 0.45 vs. 2.13 ± 0.72, p < 0.001). The nTTPF decreased during exercise in control subjects but increased in patients with HFpEF (−0.03 ± 12 s vs. +0.07 ± 0.11 s; p = 0.005). The VVC decreased on exercise in control subjects but was unchanged in patients with HFpEF (−0.01 ± 0.15 vs. −0.25 ± 0.19; p < 0.001).Patients with HFpEF have reduced cardiac energetic reserve that may underlie marked dynamic slowing of LV active relaxation and abnormal VVC during exercise.

Research paper thumbnail of Auf dem Weg zu einer allgemeinen Nucleophilie-Skala?

Angewandte Chemie, 2006

Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu... more Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu entwickeln. 1 Dem vielversprechenden Anfang in den 1950ern, aus dem die Swain-Scott-Gleichung [Gl.(1)((1))] 2 und die Edwards-Gleichung 3 hervorgingen, folgte in ...

Research paper thumbnail of Towards a General Scale of Nucleophilicity?

Angewandte Chemie-international Edition, 2006

Research paper thumbnail of Nucleophilic reactivity of the azide ion in various solvents

Journal of Physical Organic Chemistry, 2006

Page 1. Nucleophilic reactivity of the azide ion in various solvents y Thanh Binh Phan and Herber... more Page 1. Nucleophilic reactivity of the azide ion in various solvents y Thanh Binh Phan and Herbert Mayr* Department Chemie und Biochemie der Ludwig-Maximilians-Universita¨t Mu¨ nchen, Butenandtstrasse 5-13 (Haus F), 81377 Mu¨ nchen, Germany ...

Research paper thumbnail of Comparison of the nucleophilicities of alcohols and alkoxides

Canadian Journal of Chemistry, 2005

Comparison of the nucleophilicities of alcohols and alkoxides1 Thanh Binh Phan and Herbert Mayr A... more Comparison of the nucleophilicities of alcohols and alkoxides1 Thanh Binh Phan and Herbert Mayr Abstract: The kinetics of the reactions of benzhydrylium ions with some alcohols and alkoxides dissolved in the corre-sponding alcohols were photometrically investigated. ...

Research paper thumbnail of Auf dem Weg zu einer allgemeinen Nucleophilie-Skala?

Angewandte Chemie, 2006

Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu... more Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu entwickeln. 1 Dem vielversprechenden Anfang in den 1950ern, aus dem die Swain-Scott-Gleichung [Gl.(1)((1))] 2 und die Edwards-Gleichung 3 hervorgingen, folgte in ...

Research paper thumbnail of Contrast-Enhanced Magnetic Resonance Angiography of the Cervical Vessels

Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisiti... more Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisition of high-spatial-resolution, venous-suppressed, 3D MR angiograms of the cervical carotid and vertebral arteries. In this study, an elliptic centric-view ordering with either MR fluoroscopic triggering or test bolus timing was used. The use of CEMRA of the cervical vessels has changed our clinical practice and is replacing conventional angiography for the evaluation of most carotid and vertebral artery diseases. Methods-We retrospectively reviewed our experience with the use of CEMRA performed in 422 patients from January through December 1999.

Research paper thumbnail of A sensory level on the trunk and sparing the face from vertebral artery dissection: how much more subtle can we get?

Journal of Neurology Neurosurgery and Psychiatry, 1999

... (1996) Arterial territories of human brain: brainstem and cerebellum. Neurology 47:1125–1135.... more ... (1996) Arterial territories of human brain: brainstem and cerebellum. Neurology 47:1125–1135. [Abstract/FREE Full text]. ↵: Morrow M,; Sharpe JA. (1988) Torsional nystagmus in the lateral medullary syndrome. Ann Neurol 24:390–398, . ...

Research paper thumbnail of INTRA-ARTERIAL THROMBOLYSIS FOR VERTEBROBASILAR CIRCULATION ISCHEMIA

Critical Care Clinics, 1999

The poor prognosis in acute basilar artery occlusion approaches 80% to 90%.2, 15, 18 and 27 Logic... more The poor prognosis in acute basilar artery occlusion approaches 80% to 90%.2, 15, 18 and 27 Logic dictates that early recanalization of the vessel before tissue death would lead to preservation of the brain stem and cerebellum. The success of thrombolysis in myocardial infarction has led to resurgence of interest in thrombolysis for cerebral ischemia. There have been promising results of thrombolytic therapy in anterior circulation stroke, but there is no placebo control equivalent in stroke of basilar artery occlusion.1 In the past, progress in this area has been hampered by the lack of good imaging and the availability of small mobile angiographic catheters to cannulate the basilar artery. In the past 10 years there have been several uncontrolled series of intra-arterial thrombolysis in basilar artery occlusion with promising results.4, 7, 13, 17, 18, 34, 49 and 54 However, the appropriate patient for intra-arterial thrombolysis for basilar artery occlusion has not been well defined. Although patients who are in coma and tetraplegic have nothing to lose from such therapy, experience at the Mayo clinic and elsewhere has not supported this approach. The question arises as to whether thrombolytic therapy should be reserved for patients who have milder symptoms and signs. There are three small series of angiographically proven basilar artery occlusion in which patients have benign outcome. The patients in these series have less severe neurologic signs.6, 9 and 16 This has raised doubts in the minds of many clinicians as to whether to subject patients to thrombolysis or standard care with intravenous heparin only. This article briefly reviews the anatomy and the anatomic basis for the clinical features of vertebrobasilar ischemia. This is followed by a discussion on the natural history and scientific basis for thrombolysis.

Research paper thumbnail of Guillain-Barr� syndrome and adenocarcinoma of the gall bladder: A paraneoplastic phenomenon?

Research paper thumbnail of Hypertensive Encephalopathy Presenting With Thunderclap Headache

Headache, 2001

A 68-year-old woman presented with thunderclap headache, which led to a search for subarachnoid h... more A 68-year-old woman presented with thunderclap headache, which led to a search for subarachnoid hemorrhage. Both computerized tomography of the head and cerebrospinal fluid examination were normal. Magnetic resonance imaging revealed abnormalities in the white matter in the parieto-occipital regions. There was no aneurysm on magnetic resonance angiography. Treatment of hypertension led to resolution of the posterior leukoencephalopathy. Hypertensive encephalopathy with reversible posterior leukoencephalopathy can present as a thunderclap headache.

Research paper thumbnail of Intracranial saccular aneurysm enlargement determined using serial magnetic resonance angiography

Journal of Neurosurgery, 2002

The goal of this study was to determine the frequency of enlargement of unruptured intracranial a... more The goal of this study was to determine the frequency of enlargement of unruptured intracranial aneurysms by using serial magnetic resonance (MR) angiography and to investigate whether aneurysm characteristics and demographic factors predict changes in aneurysm size. A retrospective review of MR angiograms obtained in 57 patients with 62 unruptured, untreated saccular aneurysms was performed. Fifty-five of the 57 patients had no history of subarachnoid hemorrhage. The means of three measurements of the maximum diameters of these lesions on MR source images defined the aneurysm size. The median follow-up period was 47 months (mean 50 months, range 17-90 months). No aneurysm ruptured during the follow-up period. Four patients (7%) harbored aneurysms that had increased in size. No aneurysms smaller than 9 mm in diameter grew larger, whereas four (44%) of the nine aneurysms with initial diameters of 9 mm or larger increased in size. Factors that predicted aneurysm growth included the size of the lesion (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) and the presence of multiple lobes (p = 0.021). The location of the aneurysm did not predict an increased risk of enlargement. Patients with medium-sized or large aneurysms and patients harboring aneurysms with multiple lobes may be at increased risk for aneurysm growth and should be followed up with MR imaging if the aneurysm is left untreated.

Research paper thumbnail of Posttransplant primary CNS lymphoma

The records and neuro-imaging studies of 8 cases of posttransplant primary CNS lymphoma (PT-PCNSL... more The records and neuro-imaging studies of 8 cases of posttransplant primary CNS lymphoma (PT-PCNSL) diagnosed at Mayo Clinic Rochester between 1970 and 1998 were reviewed retrospectively. All patients received organ transplantation. Patients who had hematologic transplantation were not included in the analysis. The median and mean age of the 4 men and 4 women was 45 years (range, 34 to 50 years). The median duration of symptoms before diagnosis was 36 days (range, 5 to 98 days). At diagnosis, the neurologic examination was focally abnormal in 6 of 8 patients. Compared with the initial computed tomographic study, MRI showed 25 additional brain lesions. Only 43.7% of lesions enhanced with contrast agent; of those that did, all but one were heterogeneous. Ependymal contact occurred in 5 patients. MRI lesion burden increased proportionally to the interval between scans. Diagnostic tissue was obtained by stereotactic biopsy from 6 patients and by open biopsy from 2. Hemorrhage occurred in the biopsy area in 4 patients who had stereotactic biopsy and 2 died (all had normal coagulation studies). Slides available for review (7 patients) showed that the tumors were of CD20-positive lineage and were positive for Epstein-Barr virus, using in situ hybridization. Six patients died. Median survival for the cohort was 13 weeks. PT-PCNSL has clinical and imaging features distinct from typical PCNSL. In our series, (1) PT-PCNSL presented nonspeci cally and progressed rapidly, (2) stereotactic brain biopsy had signi cant morbidity, and (3) despite multimodal therapy, survival was poor. Neuro-Oncology 2, 229-238, 2000 (Posted to Neuro-Oncology [serial online], Doc. 00-034, September 13, 2000

Research paper thumbnail of Safety of Discontinuation of Anticoagulation in Patients With Intracranial Hemorrhage at High Thromboembolic Risk

Archives of Neurology, 2000

Limited data are available to guide the management of anticoagulation in patients with intracrani... more Limited data are available to guide the management of anticoagulation in patients with intracranial hemorrhage (ICH) at high thromboembolic risk. To review the management of anticoagulation in patients with ICH at high thromboembolic risk. We reviewed the management of anticoagulation in 141 patients who have a high risk of ischemic stroke and have ICH while taking warfarin. The 30-day risk of ischemic stroke while not taking anticoagulation treatment was determined using Kaplan-Meier survival estimates. The indications for anticoagulation were a prosthetic heart valve (52 patients [group 1]), atrial fibrillation and cardioembolic stroke (53 patients [group 2]), and a recurrent transient ischemic attack or an ischemic stroke (36 patients [group 3]). A prior ischemic stroke occurred in 14 (27%) of group 1 patients and in 23 (43%) of group 2 patients. Death occurred in 43% of the 141 patients. The median time not taking warfarin in this cohort was 10 days. Three patients had an ischemic stroke within 30 days of warfarin therapy discontinuation. Using Kaplan-Meier survival estimates, the probability of having an ischemic stroke at 30 days following warfarin therapy cessation in groups 1, 2, and 3 was 2.9% (95% confidence interval, 0%-8.0%), 2.6% (95% confidence interval, 0%-7.6%), and 4.8% (95% confidence interval, 0%-13.6%), respectively. In the 35 patients who had warfarin therapy restarted, none had recurrence of ICH during the same hospitalization. Discontinuation of warfarin therapy for 1 to 2 weeks has a comparatively low probability of embolic events in patients at high embolic risk. This should be taken into consideration when deciding whether to continue or discontinue anticoagulation in these patients at high embolic risk. Early recurrence of ICH is exceedingly uncommon.

Research paper thumbnail of Contrast-Enhanced Magnetic Resonance Angiography of the Cervical Vessels Experience With 422 Patients

Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisiti... more Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisition of high-spatial-resolution, venous-suppressed, 3D MR angiograms of the cervical carotid and vertebral arteries. In this study, an elliptic centric-view ordering with either MR fluoroscopic triggering or test bolus timing was used. The use of CEMRA of the cervical vessels has changed our clinical practice and is replacing conventional angiography for the evaluation of most carotid and vertebral artery diseases. Methods-We retrospectively reviewed our experience with the use of CEMRA performed in 422 patients from January through December 1999.

Research paper thumbnail of The pathophysiology of diastolic heart failure

F1000 Biology Reports, 2010

Whilst resting disturbances of both diastolic and long-axis systolic function are observed in pat... more Whilst resting disturbances of both diastolic and long-axis systolic function are observed in patients with heart failure who have normal left ventricular ejection fraction, recent evidence suggests that dynamic disturbances in cardiac function occur during exercise. A paradoxical slowing of left ventricular active relaxation during exercise limits cardiac filling and therefore stroke volume and appears to be due to the combination of cardiac energetic impairment and disturbed ventricularvascular coupling.

Research paper thumbnail of The pathophysiology of diastolic heart failure

F1000 Biology Reports, 2010

Whilst resting disturbances of both diastolic and long-axis systolic function are observed in pat... more Whilst resting disturbances of both diastolic and long-axis systolic function are observed in patients with heart failure who have normal left ventricular ejection fraction, recent evidence suggests that dynamic disturbances in cardiac function occur during exercise. A paradoxical slowing of left ventricular active relaxation during exercise limits cardiac filling and therefore stroke volume and appears to be due to the combination of cardiac energetic impairment and disturbed ventricularvascular coupling.

Research paper thumbnail of 31P magnetic resonance spectroscopy to measure in vivo cardiac energetics in normal myocardium and hypertrophic cardiomyopathy: Experiences at 3 T

European Journal of Radiology, 2010

31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kin... more 31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kinetics in the myocardium. While traditionally 31P cardiac spectroscopy is performed at 1.5 T, cardiac MRS at higher field strength can theoretically increase signal to noise ratio (SNR) and spectral resolution therefore improving sensitivity and specificity of the cardiac spectra. The reproducibility and feasibility of performing cardiac spectroscopy at 3 T is presented here in this study in healthy volunteers and patients with hypertrophic cardiomyopathy.Cardiac spectroscopy was performed using a Phillips 3T Achieva scanner in 37 healthy volunteers and 26 patients with hypertrophic cardiomyopathy (HCM) to test the feasibility of the protocol. To test the reproducibility a single volunteer was scanned eight times on separate occasions. A single voxel 31P MRS was performed using Image Selected In vivo Spectroscopy (ISIS) volume localization.The mean phosphocreatine/adenosine triphosphate (PCr/ATP) ratio of the eight measurements performed on one individual was 2.11 ± 0.25. Bland Altman plots showed a variance of 12% in the measurement of PCr/ATP ratios. The PCr/ATP ratio was significantly reduced in HCM patients compared to controls, 1.42 ± 0.51 and 2.11 ± 0.57, respectively, P < 0.0001. (All results are expressed as mean ± standard deviation).Here we demonstrate that cardiac 31P MRS at 3 T is a reliable method of measuring in vivo high-energy phosphate kinetics in the myocardium for clinical studies and diagnostics. Based on our data an impairment of cardiac energetic state in patients with hypertrophic cardiomyopathy is indisputable.

Research paper thumbnail of 31P magnetic resonance spectroscopy to measure in vivo cardiac energetics in normal myocardium and hypertrophic cardiomyopathy: Experiences at 3 T

European Journal of Radiology, 2010

31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kin... more 31P magnetic resonance spectroscopy (MRS) allows measurement of in vivo high-energy phosphate kinetics in the myocardium. While traditionally 31P cardiac spectroscopy is performed at 1.5 T, cardiac MRS at higher field strength can theoretically increase signal to noise ratio (SNR) and spectral resolution therefore improving sensitivity and specificity of the cardiac spectra. The reproducibility and feasibility of performing cardiac spectroscopy at 3 T is presented here in this study in healthy volunteers and patients with hypertrophic cardiomyopathy.Cardiac spectroscopy was performed using a Phillips 3T Achieva scanner in 37 healthy volunteers and 26 patients with hypertrophic cardiomyopathy (HCM) to test the feasibility of the protocol. To test the reproducibility a single volunteer was scanned eight times on separate occasions. A single voxel 31P MRS was performed using Image Selected In vivo Spectroscopy (ISIS) volume localization.The mean phosphocreatine/adenosine triphosphate (PCr/ATP) ratio of the eight measurements performed on one individual was 2.11 ± 0.25. Bland Altman plots showed a variance of 12% in the measurement of PCr/ATP ratios. The PCr/ATP ratio was significantly reduced in HCM patients compared to controls, 1.42 ± 0.51 and 2.11 ± 0.57, respectively, P < 0.0001. (All results are expressed as mean ± standard deviation).Here we demonstrate that cardiac 31P MRS at 3 T is a reliable method of measuring in vivo high-energy phosphate kinetics in the myocardium for clinical studies and diagnostics. Based on our data an impairment of cardiac energetic state in patients with hypertrophic cardiomyopathy is indisputable.

Research paper thumbnail of Heart Failure With Preserved Ejection Fraction Is Characterized by Dynamic Impairment of Active Relaxation and Contraction of the Left Ventricle on Exercise and Associated With Myocardial Energy Deficiency

Journal of The American College of Cardiology, 2009

We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation an... more We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation and of LV contractile function and vasculoventricular coupling (VVC) in the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and to assess myocardial energetic status in these patients.To date, no studies have investigated exercise-related changes in LV relaxation and VVC as well as in vivo myocardial energetic status in patients with HFpEF.We studied 37 patients with HFpEF and 20 control subjects. The VVC and time to peak LV filling (nTTPF, a measure of LV active relaxation) were assessed while patients were at rest and during exercise by the use of radionuclide ventriculography. Cardiac energetic status (creatine phosphate/adenosine triphosphate ratio) was assessed by the use of 31P magnetic resonance spectroscopy at 3-T.When patients were at rest, nTTPF and VVC were similar in patients with HFpEF and control subjects. The cardiac creatine phosphate/adenosine triphosphate ratio was reduced in patients with HFpEF versus control subjects (1.57 ± 0.52 vs. 2.14 ± 0.63; p = 0.003), indicating reduced energy reserves. Peak maximal oxygen uptake and the increase in heart rate during maximal exercise were lower in patients with HFpEF versus control subjects (19 ± 4 ml/kg/min vs. 36 ± 8 ml/kg/min, p < 0.001, and 52 ± 16 beats/min vs. 81 ± 14 beats/min, p < 0.001). The relative changes in stroke volume and cardiac output during submaximal exercise were lower in patients with HFpEF versus control subjects (ratio exercise/rest: 0.99 ± 0.34 vs. 1.25 ± 0.47, p = 0.04, and 1.36 ± 0.45 vs. 2.13 ± 0.72, p < 0.001). The nTTPF decreased during exercise in control subjects but increased in patients with HFpEF (−0.03 ± 12 s vs. +0.07 ± 0.11 s; p = 0.005). The VVC decreased on exercise in control subjects but was unchanged in patients with HFpEF (−0.01 ± 0.15 vs. −0.25 ± 0.19; p < 0.001).Patients with HFpEF have reduced cardiac energetic reserve that may underlie marked dynamic slowing of LV active relaxation and abnormal VVC during exercise.

Research paper thumbnail of Heart Failure With Preserved Ejection Fraction Is Characterized by Dynamic Impairment of Active Relaxation and Contraction of the Left Ventricle on Exercise and Associated With Myocardial Energy Deficiency

Journal of The American College of Cardiology, 2009

We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation an... more We sought to evaluate the role of exercise-related changes in left ventricular (LV) relaxation and of LV contractile function and vasculoventricular coupling (VVC) in the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and to assess myocardial energetic status in these patients.To date, no studies have investigated exercise-related changes in LV relaxation and VVC as well as in vivo myocardial energetic status in patients with HFpEF.We studied 37 patients with HFpEF and 20 control subjects. The VVC and time to peak LV filling (nTTPF, a measure of LV active relaxation) were assessed while patients were at rest and during exercise by the use of radionuclide ventriculography. Cardiac energetic status (creatine phosphate/adenosine triphosphate ratio) was assessed by the use of 31P magnetic resonance spectroscopy at 3-T.When patients were at rest, nTTPF and VVC were similar in patients with HFpEF and control subjects. The cardiac creatine phosphate/adenosine triphosphate ratio was reduced in patients with HFpEF versus control subjects (1.57 ± 0.52 vs. 2.14 ± 0.63; p = 0.003), indicating reduced energy reserves. Peak maximal oxygen uptake and the increase in heart rate during maximal exercise were lower in patients with HFpEF versus control subjects (19 ± 4 ml/kg/min vs. 36 ± 8 ml/kg/min, p < 0.001, and 52 ± 16 beats/min vs. 81 ± 14 beats/min, p < 0.001). The relative changes in stroke volume and cardiac output during submaximal exercise were lower in patients with HFpEF versus control subjects (ratio exercise/rest: 0.99 ± 0.34 vs. 1.25 ± 0.47, p = 0.04, and 1.36 ± 0.45 vs. 2.13 ± 0.72, p < 0.001). The nTTPF decreased during exercise in control subjects but increased in patients with HFpEF (−0.03 ± 12 s vs. +0.07 ± 0.11 s; p = 0.005). The VVC decreased on exercise in control subjects but was unchanged in patients with HFpEF (−0.01 ± 0.15 vs. −0.25 ± 0.19; p < 0.001).Patients with HFpEF have reduced cardiac energetic reserve that may underlie marked dynamic slowing of LV active relaxation and abnormal VVC during exercise.

Research paper thumbnail of Auf dem Weg zu einer allgemeinen Nucleophilie-Skala?

Angewandte Chemie, 2006

Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu... more Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu entwickeln. 1 Dem vielversprechenden Anfang in den 1950ern, aus dem die Swain-Scott-Gleichung [Gl.(1)((1))] 2 und die Edwards-Gleichung 3 hervorgingen, folgte in ...

Research paper thumbnail of Towards a General Scale of Nucleophilicity?

Angewandte Chemie-international Edition, 2006

Research paper thumbnail of Nucleophilic reactivity of the azide ion in various solvents

Journal of Physical Organic Chemistry, 2006

Page 1. Nucleophilic reactivity of the azide ion in various solvents y Thanh Binh Phan and Herber... more Page 1. Nucleophilic reactivity of the azide ion in various solvents y Thanh Binh Phan and Herbert Mayr* Department Chemie und Biochemie der Ludwig-Maximilians-Universita¨t Mu¨ nchen, Butenandtstrasse 5-13 (Haus F), 81377 Mu¨ nchen, Germany ...

Research paper thumbnail of Comparison of the nucleophilicities of alcohols and alkoxides

Canadian Journal of Chemistry, 2005

Comparison of the nucleophilicities of alcohols and alkoxides1 Thanh Binh Phan and Herbert Mayr A... more Comparison of the nucleophilicities of alcohols and alkoxides1 Thanh Binh Phan and Herbert Mayr Abstract: The kinetics of the reactions of benzhydrylium ions with some alcohols and alkoxides dissolved in the corre-sponding alcohols were photometrically investigated. ...

Research paper thumbnail of Auf dem Weg zu einer allgemeinen Nucleophilie-Skala?

Angewandte Chemie, 2006

Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu... more Seit mittlerweile mehr als fünfzig Jahren versuchen Chemiker, quantitative Nucleophilie-Skalen zu entwickeln. 1 Dem vielversprechenden Anfang in den 1950ern, aus dem die Swain-Scott-Gleichung [Gl.(1)((1))] 2 und die Edwards-Gleichung 3 hervorgingen, folgte in ...

Research paper thumbnail of Contrast-Enhanced Magnetic Resonance Angiography of the Cervical Vessels

Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisiti... more Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisition of high-spatial-resolution, venous-suppressed, 3D MR angiograms of the cervical carotid and vertebral arteries. In this study, an elliptic centric-view ordering with either MR fluoroscopic triggering or test bolus timing was used. The use of CEMRA of the cervical vessels has changed our clinical practice and is replacing conventional angiography for the evaluation of most carotid and vertebral artery diseases. Methods-We retrospectively reviewed our experience with the use of CEMRA performed in 422 patients from January through December 1999.

Research paper thumbnail of A sensory level on the trunk and sparing the face from vertebral artery dissection: how much more subtle can we get?

Journal of Neurology Neurosurgery and Psychiatry, 1999

... (1996) Arterial territories of human brain: brainstem and cerebellum. Neurology 47:1125–1135.... more ... (1996) Arterial territories of human brain: brainstem and cerebellum. Neurology 47:1125–1135. [Abstract/FREE Full text]. ↵: Morrow M,; Sharpe JA. (1988) Torsional nystagmus in the lateral medullary syndrome. Ann Neurol 24:390–398, . ...

Research paper thumbnail of INTRA-ARTERIAL THROMBOLYSIS FOR VERTEBROBASILAR CIRCULATION ISCHEMIA

Critical Care Clinics, 1999

The poor prognosis in acute basilar artery occlusion approaches 80% to 90%.2, 15, 18 and 27 Logic... more The poor prognosis in acute basilar artery occlusion approaches 80% to 90%.2, 15, 18 and 27 Logic dictates that early recanalization of the vessel before tissue death would lead to preservation of the brain stem and cerebellum. The success of thrombolysis in myocardial infarction has led to resurgence of interest in thrombolysis for cerebral ischemia. There have been promising results of thrombolytic therapy in anterior circulation stroke, but there is no placebo control equivalent in stroke of basilar artery occlusion.1 In the past, progress in this area has been hampered by the lack of good imaging and the availability of small mobile angiographic catheters to cannulate the basilar artery. In the past 10 years there have been several uncontrolled series of intra-arterial thrombolysis in basilar artery occlusion with promising results.4, 7, 13, 17, 18, 34, 49 and 54 However, the appropriate patient for intra-arterial thrombolysis for basilar artery occlusion has not been well defined. Although patients who are in coma and tetraplegic have nothing to lose from such therapy, experience at the Mayo clinic and elsewhere has not supported this approach. The question arises as to whether thrombolytic therapy should be reserved for patients who have milder symptoms and signs. There are three small series of angiographically proven basilar artery occlusion in which patients have benign outcome. The patients in these series have less severe neurologic signs.6, 9 and 16 This has raised doubts in the minds of many clinicians as to whether to subject patients to thrombolysis or standard care with intravenous heparin only. This article briefly reviews the anatomy and the anatomic basis for the clinical features of vertebrobasilar ischemia. This is followed by a discussion on the natural history and scientific basis for thrombolysis.

Research paper thumbnail of Guillain-Barr� syndrome and adenocarcinoma of the gall bladder: A paraneoplastic phenomenon?

Research paper thumbnail of Hypertensive Encephalopathy Presenting With Thunderclap Headache

Headache, 2001

A 68-year-old woman presented with thunderclap headache, which led to a search for subarachnoid h... more A 68-year-old woman presented with thunderclap headache, which led to a search for subarachnoid hemorrhage. Both computerized tomography of the head and cerebrospinal fluid examination were normal. Magnetic resonance imaging revealed abnormalities in the white matter in the parieto-occipital regions. There was no aneurysm on magnetic resonance angiography. Treatment of hypertension led to resolution of the posterior leukoencephalopathy. Hypertensive encephalopathy with reversible posterior leukoencephalopathy can present as a thunderclap headache.

Research paper thumbnail of Intracranial saccular aneurysm enlargement determined using serial magnetic resonance angiography

Journal of Neurosurgery, 2002

The goal of this study was to determine the frequency of enlargement of unruptured intracranial a... more The goal of this study was to determine the frequency of enlargement of unruptured intracranial aneurysms by using serial magnetic resonance (MR) angiography and to investigate whether aneurysm characteristics and demographic factors predict changes in aneurysm size. A retrospective review of MR angiograms obtained in 57 patients with 62 unruptured, untreated saccular aneurysms was performed. Fifty-five of the 57 patients had no history of subarachnoid hemorrhage. The means of three measurements of the maximum diameters of these lesions on MR source images defined the aneurysm size. The median follow-up period was 47 months (mean 50 months, range 17-90 months). No aneurysm ruptured during the follow-up period. Four patients (7%) harbored aneurysms that had increased in size. No aneurysms smaller than 9 mm in diameter grew larger, whereas four (44%) of the nine aneurysms with initial diameters of 9 mm or larger increased in size. Factors that predicted aneurysm growth included the size of the lesion (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) and the presence of multiple lobes (p = 0.021). The location of the aneurysm did not predict an increased risk of enlargement. Patients with medium-sized or large aneurysms and patients harboring aneurysms with multiple lobes may be at increased risk for aneurysm growth and should be followed up with MR imaging if the aneurysm is left untreated.

Research paper thumbnail of Posttransplant primary CNS lymphoma

The records and neuro-imaging studies of 8 cases of posttransplant primary CNS lymphoma (PT-PCNSL... more The records and neuro-imaging studies of 8 cases of posttransplant primary CNS lymphoma (PT-PCNSL) diagnosed at Mayo Clinic Rochester between 1970 and 1998 were reviewed retrospectively. All patients received organ transplantation. Patients who had hematologic transplantation were not included in the analysis. The median and mean age of the 4 men and 4 women was 45 years (range, 34 to 50 years). The median duration of symptoms before diagnosis was 36 days (range, 5 to 98 days). At diagnosis, the neurologic examination was focally abnormal in 6 of 8 patients. Compared with the initial computed tomographic study, MRI showed 25 additional brain lesions. Only 43.7% of lesions enhanced with contrast agent; of those that did, all but one were heterogeneous. Ependymal contact occurred in 5 patients. MRI lesion burden increased proportionally to the interval between scans. Diagnostic tissue was obtained by stereotactic biopsy from 6 patients and by open biopsy from 2. Hemorrhage occurred in the biopsy area in 4 patients who had stereotactic biopsy and 2 died (all had normal coagulation studies). Slides available for review (7 patients) showed that the tumors were of CD20-positive lineage and were positive for Epstein-Barr virus, using in situ hybridization. Six patients died. Median survival for the cohort was 13 weeks. PT-PCNSL has clinical and imaging features distinct from typical PCNSL. In our series, (1) PT-PCNSL presented nonspeci cally and progressed rapidly, (2) stereotactic brain biopsy had signi cant morbidity, and (3) despite multimodal therapy, survival was poor. Neuro-Oncology 2, 229-238, 2000 (Posted to Neuro-Oncology [serial online], Doc. 00-034, September 13, 2000

Research paper thumbnail of Safety of Discontinuation of Anticoagulation in Patients With Intracranial Hemorrhage at High Thromboembolic Risk

Archives of Neurology, 2000

Limited data are available to guide the management of anticoagulation in patients with intracrani... more Limited data are available to guide the management of anticoagulation in patients with intracranial hemorrhage (ICH) at high thromboembolic risk. To review the management of anticoagulation in patients with ICH at high thromboembolic risk. We reviewed the management of anticoagulation in 141 patients who have a high risk of ischemic stroke and have ICH while taking warfarin. The 30-day risk of ischemic stroke while not taking anticoagulation treatment was determined using Kaplan-Meier survival estimates. The indications for anticoagulation were a prosthetic heart valve (52 patients [group 1]), atrial fibrillation and cardioembolic stroke (53 patients [group 2]), and a recurrent transient ischemic attack or an ischemic stroke (36 patients [group 3]). A prior ischemic stroke occurred in 14 (27%) of group 1 patients and in 23 (43%) of group 2 patients. Death occurred in 43% of the 141 patients. The median time not taking warfarin in this cohort was 10 days. Three patients had an ischemic stroke within 30 days of warfarin therapy discontinuation. Using Kaplan-Meier survival estimates, the probability of having an ischemic stroke at 30 days following warfarin therapy cessation in groups 1, 2, and 3 was 2.9% (95% confidence interval, 0%-8.0%), 2.6% (95% confidence interval, 0%-7.6%), and 4.8% (95% confidence interval, 0%-13.6%), respectively. In the 35 patients who had warfarin therapy restarted, none had recurrence of ICH during the same hospitalization. Discontinuation of warfarin therapy for 1 to 2 weeks has a comparatively low probability of embolic events in patients at high embolic risk. This should be taken into consideration when deciding whether to continue or discontinue anticoagulation in these patients at high embolic risk. Early recurrence of ICH is exceedingly uncommon.

Research paper thumbnail of Contrast-Enhanced Magnetic Resonance Angiography of the Cervical Vessels Experience With 422 Patients

Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisiti... more Background and Purpose-Contrast-enhanced magnetic resonance angiography (CEMRA) permits acquisition of high-spatial-resolution, venous-suppressed, 3D MR angiograms of the cervical carotid and vertebral arteries. In this study, an elliptic centric-view ordering with either MR fluoroscopic triggering or test bolus timing was used. The use of CEMRA of the cervical vessels has changed our clinical practice and is replacing conventional angiography for the evaluation of most carotid and vertebral artery diseases. Methods-We retrospectively reviewed our experience with the use of CEMRA performed in 422 patients from January through December 1999.