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Papers by Andrew Hoffmann

Advances in Tissue Engineering & Regenerative Medicine: Open Access, 2016

Background: Coronary Artery Disease (CAD) is a leading source of morbidity, and search continues ... more Background: Coronary Artery Disease (CAD) is a leading source of morbidity, and search continues for viable therapeutic options to stimulate neo-coronary growth. Low sonic Frequency Vibration (LFV) can induce fluid sheer forces and cyclic stretch / strain to endothelial cells and extracellular matrix which is known to up-regulate expression of pro-angiogenic mediators such as Nitric Oxide, Vascular Endothelial Growth Factor, and other sheer responsive proteins. Further, cyclic stretch of coronary microvascular cells has shown to induce coronary angiogenesis in-vitro, and LFV promoted arteriogenesis has recently been demonstrated in vivo. Interestingly there has been no work which address whether transthoracic LFV could induce neo-coronary growth in CAD patients. Methods: To investigate feasibility we present an initial experience (n=1) in use of transthoracic LFV whereby an eighty year old male with New York Heart Classification (NYHC) Class 3 heart failure and inferior ischemia (by Persantine 99mTc Myoview scan) was provided a vibrator (27-35Hz, 6mm) for application to his upper back for 15-30 minute daily home based massage sessions planned for a three month period. Time spent and feelings regarding treatment were recorded. Results: Home delivered device use was feasible, averaging ~3 times per week. There were no lasting adverse safety concerns-although transient musculoskeletal discomforts were reported. While effectiveness of the therapy was not a focus of this study, repeat Myoview testing following 3.5 months of therapy in this single test subject showed an absence of resting and provokable ischemia with reportedly "homogenous uptake-no defects", and patient's heart failure improved from Class 3 to 2. Conclusion: We report an initial experience in use of transthoracic LFV in an IHF patient in view to promoting neo-coronary growth. In view of correlative data that sheer producing and oscillative therapies reportedly induce neo-arterial growth, further pilot testing of transthoracic LFV in a statistically relevant number of CAD patients appears warranted.

American Journal of Biomedical Sciences, 2012

Background: Localized Low Frequency Vibration (LLFV) in the low sonic range is utilized for disru... more Background: Localized Low Frequency Vibration (LLFV) in the low sonic range is utilized for disruption of clots by direct contact in catheter applications. However enhanced clot dissolution whereby an LLFV source is applied external from a clotted lumen (such as to resemble a non-invasive therapy) has not been studied. Objective: To assess the effectiveness of low amplitude extra luminally applied 50 Hz LLFV in dissolution of 1 hr old clots immersed in Heparinized Saline. Methods: One hr old blood clots were each placed within a 3 ml syringe filled with 1.5 ml's of Heparinized Saline. LLFV was then applied against the external surface of each syringe with gentle stroke amplitude (~ 0.5 mm), an intensity within an order of magnitude expected to reach a thrombosed vessel (such as a coronary, pulmonary, cerebral, or peripheral artery), given if a substantially stronger application where to be applied non-invasively across the artery's overlying soft tissue barrier. Results: LLFV yielded statistically superior clot dissolution (25%) in comparison to the non vibrated controls (5%) (p<0.0003). Conclusions: Transluminally applied LLFV (50 Hz) accelerates clot dissolution in vitro. Further study in this area in-vivo appears warranted.

http://isrctn.com/, 2015

Coronary artery disease (CAD) is a leading source of death and morbidity, and the search continue... more Coronary artery disease (CAD) is a leading source of death and morbidity, and the search continues for viable therapeutic options to stimulate new coronary growth. Low frequency vibration (LFV) can induce fluid sheer forces and cyclic stretch/strain to vascular endothelial cells and extracellular matrix which is known to up-regulate expression of pro-angiogenic mediators such as nitric oxide, vascular endothelial growth factor, and other sheer responsive proteins. Further, cyclic stretch of coronary microvascular cells has shown to induce coronary angiogenesis in-vitro, and LFV promoted arteriogenesis has recently been demonstrated in-vivo. Interestingly there has been no work to address whether transthoracic LFV massage could induce neo-coronary growth in CAD patients. We therefore present a single center, prospective, blinded, randomized, controlled pilot study protocol aiming to test whether penetrative LFV (35 Hz) applied to the upper back of refractory angina (RFA) and/or ischemic heart failure (IHF) patients (by daily 30 minute sessions, over a 3 month period) may enhance lasting myocardial perfusion and improve clinical outcomes.

Cardiovascular engineering (Dordrecht, Netherlands), 2010

Our institution is in development of a low frequency, non-invasive Diastolic Timed Vibrator (DTV)... more Our institution is in development of a low frequency, non-invasive Diastolic Timed Vibrator (DTV) for use in emergency treatment of ST Elevation Myocardial Infarction (STEMI). It is preferable to avoid vibration emissions during the IsoVolumetric Contraction Period (IVCP) and at least the majority of mechanical systole thereafter, as systolic vibration may cause a negative inotropic effect in the ischemic heart. Furthermore diastolic vibration should preferably include the IsoVolumetric Relaxation Period (IVRP) which has been shown in clinical studies to improve cardiac performance and enhance coronary flow. Electrocardiographic (ECG) monitoring can be used to enable diastolic tracking, however, the timing of the phases of the cardiac cycle in relation to the ECG waveform must first be verified. The objective of this study was therefore to determine timing of onset of mechanical systole and diastole in reference to the QRS-T Complex. One hundred and twenty-three adult echocardiograp...

Journal of Thrombosis and Thrombolysis, 2011

Our institution is developing a non-invasive Diastolic Timed Vibrator (DTV) to enhance emergency ... more Our institution is developing a non-invasive Diastolic Timed Vibrator (DTV) to enhance emergency clearance of acute coronary thrombosis. Sonic frequency diastolic vibro-percussion (i.e. 50 Hz, 2 mm amplitude) applied upon the rib-spaces of the left sternal border has shown to improve left ventricular performance and coronary flow in human volunteers. However, therapeutic acoustic penetrability cannot be assumed depending on varying chest size and lung position which attenuates acoustic transmissions. Furthermore, chest locations enabling a direct lung free pathway overlying the base of the heart (wherein the coronaries arise) should be promoted, while locations overlying the left ventricular apex (site of potential thrombus formation) should be avoided. We therefore set out to determine preferred chest wall placement positions for a vibratory interface suitable for treatment of ST Elevation Myocardial Infarction (STEMI). Inter-Costal Space (ICS) positions to the left or right of the sternum were interrogated in 90 adults following routine Echocardiography to ascertain whether the base of the heart could be imaged (hence inferring acoustic transmissibility), and to determine over what part of the heart each transducer position was overlying. The third and fourth ICS proximate the left sternal border provided acoustic transmissibility in 96 and 100% of cases respectively, with only one unwanted occurrence from the fourth ICS where the transducer overlaid the apical third of the left ventricle. Acoustic transmissibility from third and fourth ICS right sternal border was documented in 53 and 85% of cases respectively. A vibration interface in STEMI treatment should allow for contact overlying the left and right third and fourth ICS generally proximate the sternal borders. As vibration transmission to the cardiac apex and/or left atrium cannot be completely avoided, vibration therapy should be contra-indicated in late presenters for antero-septal apical STEMI, and in cases of new onset atrial fibrillation persisting greater than 48 h which have not been adequately anti-coagulated.

Journal of Thrombosis and Thrombolysis, 2007

Myocardial infarction and stroke (arterial thrombosis) comprise the leading killers and sources o... more Myocardial infarction and stroke (arterial thrombosis) comprise the leading killers and sources of disability in the developed world, and incomplete thrombolysis along with high bleeding rates (plus late presentations to cathlabs) have prompted an intensive search for alternative or adjunctive emergency therapies. Transcutaneous ultrasound has been studied in remediation of thrombosis, but has been problematic due to poor penetration, risk of arterial damage, plus the apparent need for a highly skilled approach. Surprisingly there has been no reported studies on the much simpler application of transcutaneous low frequency vibration (well known for its superior penetration and flow enhancing characteristics) to assist arterial thrombolysis. The aim of our experiment therefore was to test the hypothesis whether vibration (i.e. approximately 100 Hz, 0.5 mm), when applied across an attenuating barrier, would assist recanulization of a thrombosed flow system held at arterial like pressure. A teddy bear with a 2 cm slab of New York Steak placed upon its chest surface was used as a test subject with an in-dwelling catheter (approximately 4.0 mm lumen) cannulated through the bear&amp;amp;amp;amp;#39;s thorax. In a series of test runs (n=30), a 2 h old (or older) blood clot was injected into the catheter such as to occlude it at a stenosis site (approximately 90% luminal narrowing) created by a clamp placed along the catheter within the teddy&amp;amp;amp;amp;#39;s chest region. A pressurized heparinized IV system was in all cases connected to the catheter such as to yield an &amp;amp;amp;amp;quot;arterial like&amp;amp;amp;amp;quot; lumen pressure proximal the obstruction. For each test run, after a twenty minute observation period to confirm stability of the occlusion, test groups where randomized to receive vibration to the slab of steak upon the teddy&amp;amp;amp;amp;#39;s &amp;amp;amp;amp;quot;chest wall&amp;amp;amp;amp;quot; (generally overlying the site of the thrombotic obstruction), or no vibration for an evaluation period of up to 45 min. Catheter reflow occurred rapidly (median reflow-time 90 s) in the vibration groups within the evaluation period (i.e. 15/17), while the system remained otherwise blocked in the control groups receiving no vibration (i.e. 0/13). The difference in flow system patency rate for the vibration groups vs. the control groups was statistically significant (P=0.0000009). The frequent and generally rapid re-establishment of flow in vibration groups compared to the complete absence of reflow in control groups confirms the hypothesis that vibration applied across a physical barrier assists clearance of a blood clot in a stenosed flow system under systemic levels of pressure. We studied the incidence of clearance of a blood clot within a stenosed, heparanized catheter system held at arterial like pressure that was treated with externally delivered low frequency vibration (applied proximate the thrombotic occlusion across an attenuating medium--a 2 cm thick slab of New York Steak--at approximately 100 Hz, 0.5 mm), versus no vibration. Reflow in test runs incorporating vibration occurred faster, and resulted in significantly greater recanulization rates in the catheter system versus test runs without vibration (P=0.0000009). Non-invasive vibration holds potential as an adjunct to pharmacologic therapy in treatment of acute arterial thrombosis. Further study of this technique appears warranted in live animal models.

Journal of Experimental Stroke & Translational Medicine, 2017

Slow uncertain reperfusion in Acute Ischemic Stroke (AIS) by intravenous thrombolysis has prompte... more Slow uncertain reperfusion in Acute Ischemic Stroke (AIS) by intravenous thrombolysis has prompted search for alternative therapies. Pressure/flow disturbances from rapid compressions (20-24 Hz) of a clotted flow tube remote from thrombosis site have shown to assist reflow. Carotid Vibro-Compression (VC), a potentially risky maneuver, may therefore enhance AIS reperfusion but verification is needed that vibro-compressions would transmit flow disturbances to the cerebral arteries. From a pool of 15 volunteers (mean age 48) carotid compressions (5 to 8 Hz, < = ~1 cm) (n =11) and vibration (30 Hz ~ 1 mm) (n = 10) were independently and together implemented with ipsilateral and contralateral Doppler flow monitoring of an intra-cranial artery. Doppler pulses from compressions were immediately demonstrated in all vessels (26 / 26) under all conditions. Pulses from vibration were observable in a majority of vessels (22 / 25), but signals were often challenging to obtain. Mean intra-cranial flow velocities trended to increase during compressions (46.1 ± 6 .4 cm/s vs. 44.0 ± 4.9 cm/s), but the difference was not statistically significant (p = 0.06). Carotid VC reliably transmits flow pulses to the cerebral vasculature, however vibration requires biofeedback to ensure device positioning. Carotid VC appears feasible for animal testing, but safety remains a major question.

Background: Low Frequency Vibro-Percussion (LFVP) assists clearance of thrombi in catheter system... more Background: Low Frequency Vibro-Percussion (LFVP) assists clearance of thrombi in catheter systems and when applied to the heart and timed to diastole is known to enhance coronary flow. However LFVP on a clotted coronary like vessel given engagement over a chest wall sized barrier (to resemble non-invasive heart attack therapy) requires study. Methods: One hour old clots (n=16) were dispensed within a flexible segment of Soft-Flo catheter (4 mm lumen), weighted, interfaced with Heparinized Saline (HS), secured atop a curved dampening base, and photographed. A~4 cm meat slab was placed over the segment and randomized to receive intermittent LFVP (engaged,disengaged at 1 second intervals), or no LFVP for 20 minutes. HS was pulsed (~120/80 mmHg), with the diastolic phase coordinated to match LFVP delivery. The segment was then re-photographed and aspirated of fluid to determine post clot weight. The trial was then repeated with 0.5 mls of Streptokinase (15,000 IU/100 microlitre) delivered~2 cm upstream from the clot. Results: LFVP-HS only samples (vs. controls) showed; a) development of clot length fluid channels absent in the control group (p < 0.0002); b) enhanced dissolved clot mixing scores (5.0 vs. 0.8, p < 2.8 E-6); and c) increased percent clot dissolution (23.0% vs. 1.8% respectively, p < 8.5 E-6). LFVP-SK samples had a similar comparative clot disruptive profile, however fluid channels developed faster and percent clot dissolution more than doubled (51.0% vs. 3.0%, p< 9.8 E-6). Conclusion: Diastolic timed LFVP (50 Hz) engaged across a chest wall sized barrier enhances clot disruptive effects to an underlying coronary like system.

Advances in Tissue Engineering & Regenerative Medicine: Open Access, 2016

Background: Coronary Artery Disease (CAD) is a leading source of morbidity, and search continues ... more Background: Coronary Artery Disease (CAD) is a leading source of morbidity, and search continues for viable therapeutic options to stimulate neo-coronary growth. Low sonic Frequency Vibration (LFV) can induce fluid sheer forces and cyclic stretch / strain to endothelial cells and extracellular matrix which is known to up-regulate expression of pro-angiogenic mediators such as Nitric Oxide, Vascular Endothelial Growth Factor, and other sheer responsive proteins. Further, cyclic stretch of coronary microvascular cells has shown to induce coronary angiogenesis in-vitro, and LFV promoted arteriogenesis has recently been demonstrated in vivo. Interestingly there has been no work which address whether transthoracic LFV could induce neo-coronary growth in CAD patients. Methods: To investigate feasibility we present an initial experience (n=1) in use of transthoracic LFV whereby an eighty year old male with New York Heart Classification (NYHC) Class 3 heart failure and inferior ischemia (by Persantine 99mTc Myoview scan) was provided a vibrator (27-35Hz, 6mm) for application to his upper back for 15-30 minute daily home based massage sessions planned for a three month period. Time spent and feelings regarding treatment were recorded. Results: Home delivered device use was feasible, averaging ~3 times per week. There were no lasting adverse safety concerns-although transient musculoskeletal discomforts were reported. While effectiveness of the therapy was not a focus of this study, repeat Myoview testing following 3.5 months of therapy in this single test subject showed an absence of resting and provokable ischemia with reportedly "homogenous uptake-no defects", and patient's heart failure improved from Class 3 to 2. Conclusion: We report an initial experience in use of transthoracic LFV in an IHF patient in view to promoting neo-coronary growth. In view of correlative data that sheer producing and oscillative therapies reportedly induce neo-arterial growth, further pilot testing of transthoracic LFV in a statistically relevant number of CAD patients appears warranted.

American Journal of Biomedical Sciences, 2012

Background: Localized Low Frequency Vibration (LLFV) in the low sonic range is utilized for disru... more Background: Localized Low Frequency Vibration (LLFV) in the low sonic range is utilized for disruption of clots by direct contact in catheter applications. However enhanced clot dissolution whereby an LLFV source is applied external from a clotted lumen (such as to resemble a non-invasive therapy) has not been studied. Objective: To assess the effectiveness of low amplitude extra luminally applied 50 Hz LLFV in dissolution of 1 hr old clots immersed in Heparinized Saline. Methods: One hr old blood clots were each placed within a 3 ml syringe filled with 1.5 ml's of Heparinized Saline. LLFV was then applied against the external surface of each syringe with gentle stroke amplitude (~ 0.5 mm), an intensity within an order of magnitude expected to reach a thrombosed vessel (such as a coronary, pulmonary, cerebral, or peripheral artery), given if a substantially stronger application where to be applied non-invasively across the artery's overlying soft tissue barrier. Results: LLFV yielded statistically superior clot dissolution (25%) in comparison to the non vibrated controls (5%) (p<0.0003). Conclusions: Transluminally applied LLFV (50 Hz) accelerates clot dissolution in vitro. Further study in this area in-vivo appears warranted.

http://isrctn.com/, 2015

Coronary artery disease (CAD) is a leading source of death and morbidity, and the search continue... more Coronary artery disease (CAD) is a leading source of death and morbidity, and the search continues for viable therapeutic options to stimulate new coronary growth. Low frequency vibration (LFV) can induce fluid sheer forces and cyclic stretch/strain to vascular endothelial cells and extracellular matrix which is known to up-regulate expression of pro-angiogenic mediators such as nitric oxide, vascular endothelial growth factor, and other sheer responsive proteins. Further, cyclic stretch of coronary microvascular cells has shown to induce coronary angiogenesis in-vitro, and LFV promoted arteriogenesis has recently been demonstrated in-vivo. Interestingly there has been no work to address whether transthoracic LFV massage could induce neo-coronary growth in CAD patients. We therefore present a single center, prospective, blinded, randomized, controlled pilot study protocol aiming to test whether penetrative LFV (35 Hz) applied to the upper back of refractory angina (RFA) and/or ischemic heart failure (IHF) patients (by daily 30 minute sessions, over a 3 month period) may enhance lasting myocardial perfusion and improve clinical outcomes.

Cardiovascular engineering (Dordrecht, Netherlands), 2010

Our institution is in development of a low frequency, non-invasive Diastolic Timed Vibrator (DTV)... more Our institution is in development of a low frequency, non-invasive Diastolic Timed Vibrator (DTV) for use in emergency treatment of ST Elevation Myocardial Infarction (STEMI). It is preferable to avoid vibration emissions during the IsoVolumetric Contraction Period (IVCP) and at least the majority of mechanical systole thereafter, as systolic vibration may cause a negative inotropic effect in the ischemic heart. Furthermore diastolic vibration should preferably include the IsoVolumetric Relaxation Period (IVRP) which has been shown in clinical studies to improve cardiac performance and enhance coronary flow. Electrocardiographic (ECG) monitoring can be used to enable diastolic tracking, however, the timing of the phases of the cardiac cycle in relation to the ECG waveform must first be verified. The objective of this study was therefore to determine timing of onset of mechanical systole and diastole in reference to the QRS-T Complex. One hundred and twenty-three adult echocardiograp...

Journal of Thrombosis and Thrombolysis, 2011

Our institution is developing a non-invasive Diastolic Timed Vibrator (DTV) to enhance emergency ... more Our institution is developing a non-invasive Diastolic Timed Vibrator (DTV) to enhance emergency clearance of acute coronary thrombosis. Sonic frequency diastolic vibro-percussion (i.e. 50 Hz, 2 mm amplitude) applied upon the rib-spaces of the left sternal border has shown to improve left ventricular performance and coronary flow in human volunteers. However, therapeutic acoustic penetrability cannot be assumed depending on varying chest size and lung position which attenuates acoustic transmissions. Furthermore, chest locations enabling a direct lung free pathway overlying the base of the heart (wherein the coronaries arise) should be promoted, while locations overlying the left ventricular apex (site of potential thrombus formation) should be avoided. We therefore set out to determine preferred chest wall placement positions for a vibratory interface suitable for treatment of ST Elevation Myocardial Infarction (STEMI). Inter-Costal Space (ICS) positions to the left or right of the sternum were interrogated in 90 adults following routine Echocardiography to ascertain whether the base of the heart could be imaged (hence inferring acoustic transmissibility), and to determine over what part of the heart each transducer position was overlying. The third and fourth ICS proximate the left sternal border provided acoustic transmissibility in 96 and 100% of cases respectively, with only one unwanted occurrence from the fourth ICS where the transducer overlaid the apical third of the left ventricle. Acoustic transmissibility from third and fourth ICS right sternal border was documented in 53 and 85% of cases respectively. A vibration interface in STEMI treatment should allow for contact overlying the left and right third and fourth ICS generally proximate the sternal borders. As vibration transmission to the cardiac apex and/or left atrium cannot be completely avoided, vibration therapy should be contra-indicated in late presenters for antero-septal apical STEMI, and in cases of new onset atrial fibrillation persisting greater than 48 h which have not been adequately anti-coagulated.

Journal of Thrombosis and Thrombolysis, 2007

Myocardial infarction and stroke (arterial thrombosis) comprise the leading killers and sources o... more Myocardial infarction and stroke (arterial thrombosis) comprise the leading killers and sources of disability in the developed world, and incomplete thrombolysis along with high bleeding rates (plus late presentations to cathlabs) have prompted an intensive search for alternative or adjunctive emergency therapies. Transcutaneous ultrasound has been studied in remediation of thrombosis, but has been problematic due to poor penetration, risk of arterial damage, plus the apparent need for a highly skilled approach. Surprisingly there has been no reported studies on the much simpler application of transcutaneous low frequency vibration (well known for its superior penetration and flow enhancing characteristics) to assist arterial thrombolysis. The aim of our experiment therefore was to test the hypothesis whether vibration (i.e. approximately 100 Hz, 0.5 mm), when applied across an attenuating barrier, would assist recanulization of a thrombosed flow system held at arterial like pressure. A teddy bear with a 2 cm slab of New York Steak placed upon its chest surface was used as a test subject with an in-dwelling catheter (approximately 4.0 mm lumen) cannulated through the bear&amp;amp;amp;amp;#39;s thorax. In a series of test runs (n=30), a 2 h old (or older) blood clot was injected into the catheter such as to occlude it at a stenosis site (approximately 90% luminal narrowing) created by a clamp placed along the catheter within the teddy&amp;amp;amp;amp;#39;s chest region. A pressurized heparinized IV system was in all cases connected to the catheter such as to yield an &amp;amp;amp;amp;quot;arterial like&amp;amp;amp;amp;quot; lumen pressure proximal the obstruction. For each test run, after a twenty minute observation period to confirm stability of the occlusion, test groups where randomized to receive vibration to the slab of steak upon the teddy&amp;amp;amp;amp;#39;s &amp;amp;amp;amp;quot;chest wall&amp;amp;amp;amp;quot; (generally overlying the site of the thrombotic obstruction), or no vibration for an evaluation period of up to 45 min. Catheter reflow occurred rapidly (median reflow-time 90 s) in the vibration groups within the evaluation period (i.e. 15/17), while the system remained otherwise blocked in the control groups receiving no vibration (i.e. 0/13). The difference in flow system patency rate for the vibration groups vs. the control groups was statistically significant (P=0.0000009). The frequent and generally rapid re-establishment of flow in vibration groups compared to the complete absence of reflow in control groups confirms the hypothesis that vibration applied across a physical barrier assists clearance of a blood clot in a stenosed flow system under systemic levels of pressure. We studied the incidence of clearance of a blood clot within a stenosed, heparanized catheter system held at arterial like pressure that was treated with externally delivered low frequency vibration (applied proximate the thrombotic occlusion across an attenuating medium--a 2 cm thick slab of New York Steak--at approximately 100 Hz, 0.5 mm), versus no vibration. Reflow in test runs incorporating vibration occurred faster, and resulted in significantly greater recanulization rates in the catheter system versus test runs without vibration (P=0.0000009). Non-invasive vibration holds potential as an adjunct to pharmacologic therapy in treatment of acute arterial thrombosis. Further study of this technique appears warranted in live animal models.

Journal of Experimental Stroke & Translational Medicine, 2017

Slow uncertain reperfusion in Acute Ischemic Stroke (AIS) by intravenous thrombolysis has prompte... more Slow uncertain reperfusion in Acute Ischemic Stroke (AIS) by intravenous thrombolysis has prompted search for alternative therapies. Pressure/flow disturbances from rapid compressions (20-24 Hz) of a clotted flow tube remote from thrombosis site have shown to assist reflow. Carotid Vibro-Compression (VC), a potentially risky maneuver, may therefore enhance AIS reperfusion but verification is needed that vibro-compressions would transmit flow disturbances to the cerebral arteries. From a pool of 15 volunteers (mean age 48) carotid compressions (5 to 8 Hz, < = ~1 cm) (n =11) and vibration (30 Hz ~ 1 mm) (n = 10) were independently and together implemented with ipsilateral and contralateral Doppler flow monitoring of an intra-cranial artery. Doppler pulses from compressions were immediately demonstrated in all vessels (26 / 26) under all conditions. Pulses from vibration were observable in a majority of vessels (22 / 25), but signals were often challenging to obtain. Mean intra-cranial flow velocities trended to increase during compressions (46.1 ± 6 .4 cm/s vs. 44.0 ± 4.9 cm/s), but the difference was not statistically significant (p = 0.06). Carotid VC reliably transmits flow pulses to the cerebral vasculature, however vibration requires biofeedback to ensure device positioning. Carotid VC appears feasible for animal testing, but safety remains a major question.

Background: Low Frequency Vibro-Percussion (LFVP) assists clearance of thrombi in catheter system... more Background: Low Frequency Vibro-Percussion (LFVP) assists clearance of thrombi in catheter systems and when applied to the heart and timed to diastole is known to enhance coronary flow. However LFVP on a clotted coronary like vessel given engagement over a chest wall sized barrier (to resemble non-invasive heart attack therapy) requires study. Methods: One hour old clots (n=16) were dispensed within a flexible segment of Soft-Flo catheter (4 mm lumen), weighted, interfaced with Heparinized Saline (HS), secured atop a curved dampening base, and photographed. A~4 cm meat slab was placed over the segment and randomized to receive intermittent LFVP (engaged,disengaged at 1 second intervals), or no LFVP for 20 minutes. HS was pulsed (~120/80 mmHg), with the diastolic phase coordinated to match LFVP delivery. The segment was then re-photographed and aspirated of fluid to determine post clot weight. The trial was then repeated with 0.5 mls of Streptokinase (15,000 IU/100 microlitre) delivered~2 cm upstream from the clot. Results: LFVP-HS only samples (vs. controls) showed; a) development of clot length fluid channels absent in the control group (p < 0.0002); b) enhanced dissolved clot mixing scores (5.0 vs. 0.8, p < 2.8 E-6); and c) increased percent clot dissolution (23.0% vs. 1.8% respectively, p < 8.5 E-6). LFVP-SK samples had a similar comparative clot disruptive profile, however fluid channels developed faster and percent clot dissolution more than doubled (51.0% vs. 3.0%, p< 9.8 E-6). Conclusion: Diastolic timed LFVP (50 Hz) engaged across a chest wall sized barrier enhances clot disruptive effects to an underlying coronary like system.