E A Cohen

University of Toronto, Toronto, Ontario, Canada

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Publications (15)94.46 Total impact

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    ABSTRACT: Balloon angioplasty (PTCA) of occluded coronary arteries is limited by high rates of restenosis and reocclusion. Although stenting improves results in anatomically simple occlusions, its effect on patency and clinical outcome in a broadly selected population with occluded coronary arteries is unknown. Eighteen centers randomized 410 patients with nonacute native coronary occlusions to PTCA or primary stenting with the heparin-coated Palmaz-Schatz stent. The primary end point, failure of sustained patency, was determined at 6-month angiography. Repeat target-vessel revascularization, adverse cardiovascular events, and angiographic restenosis (>50% diameter stenosis) constituted secondary end points. Sixty percent of patients had occlusions of >6 weeks' duration, baseline flow was TIMI grade 0 in 64%, and median treated segment length was 30.5 mm. With 95.6% angiographic follow-up, primary stenting resulted in a 44% reduction in failed patency (10.9% versus 19.5%, P=0.024) and a 45% reduction in clinically driven target-vessel revascularization at 6 months (15.4% versus 8.4%, P=0.03). The incidence of adverse cardiovascular events was similar for both strategies (PTCA, 23.6%; stent, 23.3%; P=NS). Stenting resulted in a larger mean 6-month minimum lumen dimension (1.48 versus 1.23 mm, P<0.01) and a reduced binary restenosis rate (55% versus 70%, P<0.01). Primary stenting of broadly selected nonacute coronary occlusions is superior to PTCA alone, improving late patency and reducing restenosis and target-vessel revascularization.
    Full-text · Article · Aug 1999 · Circulation
  • P W Johnston · S Fort · EA Cohen
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    ABSTRACT: To review the diagnosis and management of noncritical left main stem disease. MEDLINE was searched using the key phrases 'intravascular ultrasound' and 'left main coronary artery'. Articles addressing the angiographic or ultrasound assessment of left main stem disease were systematically reviewed. Reference is also made to articles dealing with outcomes for patients with left main stem disease. The assessment of left main stem disease by coronary angiography is often suboptimal. Intravascular ultrasound has demonstrated significant left main stem disease in angiographically normal arteries. It has also demonstrated that mild to moderate left main stem disease frequently accompanies disease in the other coronary arteries. The natural history of mild to moderate left main stem disease has not been well characterized; thus, the optimum management of this condition is not known. To establish the natural history of noncritical left main stem stenosis, it is proposed that centres performing frequent intravascular ultrasound examinations systematically and quantitatively interrogate the left main stem during all left coronary examinations. Angiographic and ultrasonic measures of left main stem disease can then be correlated with clinical outcome during long term follow-up. This will clearly require the collaboration of several centres to generate a sufficiently large database to address these clinical questions.
    No preview · Article · Apr 1999 · The Canadian journal of cardiology
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    ABSTRACT: Laboratory evidence supports the use of adenosine-supplemented cardioplegia. An initial phase 1 dose-ranging clinical evaluation demonstrated that an adenosine concentration of 15 mumol/L could be safely administered with warm blood cardioplegia and suggested that phase 2 studies were warranted. Two separate double-blind, randomized, placebo-controlled trials were performed in patients undergoing primary, isolated, nonemergent coronary artery bypass graft surgery. Patients were randomized to receive adenosine 15 mumol/L versus placebo in the first study (n = 200) and adenosine 50 or 100 mumol/L versus placebo in the second study (n = 128). Adenosine was infused with both initial and final doses of warm antegrade blood cardioplegia. The data from the 2 trials were combined using the methods of Mantel and Haenszel, and the results of the meta-analysis are presented as the relative risk with their associated 95% confidence intervals (CI). The different study groups were comparable with respect to all preoperative clinical characteristics, angiographic findings, and intraoperative variables. In both trials 1 and 2, no differences were found between groups in the incidence of the individual primary or secondary outcomes. Similarly, when both studies were combined, there was no significant evidence of any consistent treatment benefit (primary: death: relative risk [RR] = 1.02, 95% CI = 0.06, 16.6; myocardial infarction by CK-MB: RR = 0.84, CI = 0.54, 1.31; low output syndrome: RR = 1.38, CI = 0.29, 6.42; any of the above: RR = 0.98, CI = 0.78, 1.25; secondary: Q-wave myocardial infarction: RR = 1.30, CI = 0.41, 4.13; myocardial infarction by troponin T: RR = 0.7, CI = 0.40, 1.21; inotrope requirement: RR = 0.9, CI = 0.46, 1.79; intra-aortic balloon pump requirement: RR = 0.6, CI = 0.07, 4.81; P > 0.20). Despite promising experimental data, adenosine supplementation of warm blood cardioplegia did not demonstrate any statistically significant benefit in patients undergoing elective coronary artery bypass graft surgery. Although sample sizes were relatively small, based on our interim analyses, it is unlikely that increased patient enrollment would reveal any substantive clinical differences between groups.
    No preview · Article · Dec 1998 · Circulation
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    ABSTRACT: Left internal thoracic artery (LITA) grafts to the left anterior descending coronary artery (LAD) during coronary bypass surgery (CABG) have greater patency rates than saphenous vein grafts and reduce long-term cardiac morbidity and mortality rates. The benefits of multiple versus single arterial grafts and the role of different arterial conduits with respect to short- and medium-term outcome remains controversial. The purpose of this study was to compare the perioperative and intermediate-term results of: (1) patients receiving 2 arterial grafts versus 1 arterial graft and (2) patients receiving a right internal thoracic artery (RITA) versus a radial artery (RA) as the second arterial graft. Retrospective analysis of prospectively gathered data on consecutive patients undergoing isolated CABG at our institution between 1989 and 1996 was conducted. The first section of the study compared outcomes for 1 arterial graft (LITA to LAD, n = 2333) versus 2 arterial grafts (LITA + RA or LITA + RITA, n = 378). The second section of the study compared outcomes for the RITA (n = 132) versus the RA (n = 171) as second arterial grafts since 1992, when the radial series was initiated. Part I: By multivariable stepwise logistic regression, the use of 1 arterial graft was associated with an increased incidence of perioperative cardiac morbidity and mortality (odds ratio 2.2, 95% confidence interval 1.4 to 3.3), with the use of our current patient selection criteria. Double-arterial graft patients had a nonsignificant trend toward increased intermediate-term actuarial survival (P = 0.12) and cardiac event-free survival (P = 0.09). Part II: Comparison of preoperative demographics revealed a higher incidence of diabetes (27% vs 11%, P < 0.001), peripheral vascular disease (16% vs 8%, P = 0.03), and elderly age (13% vs 2%, P = 0.001) in patients receiving an RA versus those receiving a RITA as the second arterial graft. Perioperative outcome analysis revealed a decreased intensive care unit stay in the RA versus RITA group (median 30.4 vs 36.2 hours, respectively, P = 0.005) but no significant difference in hospital length of stay. There was no significant difference in perioperative mortality or cardiac morbidity rates. RITA patients had a higher incidence of sternal wound infection (5.3% vs 0.6%, P = 0.01), however, and tended to have increased blood product transfusion rates (51% vs 40%, P = 0.06). The use of 2 arterial grafts is safe, with a reduction in perioperative cardiac morbidity or mortality rates compared with 1 arterial graft after adjustment for other risk variables. When comparing RITA to RA as second arterial grafts, patients receiving an RA have a lower incidence of sternal wound infection and decreased transfusion requirements, with no difference in perioperative or intermediate-term cardiac morbidity or mortality rates.
    No preview · Article · Dec 1998 · Circulation
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    ABSTRACT: In autumn 1996, shortly after the platelet glycoprotein (GP) IIb/IIIa inhibitor abciximab was approved for clinical use by the Health Protection Branch of Health Canada, seven interventional cardiologists met in a roundtable forum to review the use of abciximab in percutaneous transluminal coronary angioplasty (PTCA). While a compelling body of data was presented that argued strongly for adjunctive abciximab in conventional balloon angioplasty, the participants found in difficult to extrapolate the findings to contemporary interventional practice dominated by stent implantation. This uncertainty stemmed from the lack of clinical trials of abciximab during the stent era. Concerns were also raised that the unrestricted use of two expensive therapeutic modalities (stent implantation and GP IIb/IIIa inhibition) would place severe strains on catheterization laboratory budgets. The general consensus was that, pending the availability of further data, abciximab should probably be reserved for selected at-risk patients. This article summarized the roundtable discussions to provide cardiologists' perspectives on the use of abciximab in interventional practice. An overview of platelet physiology and the rationale for GP IIb/IIIa receptor inhibition; a summary of the results of recent randomized clinical trials that assessed the efficacy of abciximab in PTCA; an account of how stents became the most prevalent technique used in coronary intervention; a summary of the available data evaluating abciximab in conjunction with stent implantation; and a synopsis of the conference discussions are included.
    No preview · Article · Sep 1998 · The Canadian journal of cardiology
  • S Kassam · K Freskiw · K Sykora · C D Morgan · E A Cohen
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    ABSTRACT: Various strategies exist for the use of cardiac catheterization in unstable angina or non-Q wave myocardial infarction. At the authors' institution, the overall volume of cardiac catheterization has increased in recent years. To investigate whether this increased volume of cardiac catheterization was due to adoption of a more invasive approach to the management of patients with acute ischemic syndromes. A retrospective cohort study was conducted using detailed chart review of coronary care unit admissions during 1990/91 and 1993/94. A university-affiliated tertiary care referral centre with facilities for cardiac catheterization. One hundred patients randomly selected from among those with unstable angina, non-Q wave myocardial infarction or chest pain not yet diagnosed in each of the study years. Detailed follow-up was complete for all patients. The use of cardiac catheterization during the index admission was documented. There was a trend towards more frequent use of same admission cardiac catheterization in the later period (21% [CI 14% to 31%] versus 12% [CI 7% to 20%], P = 0.09). However, after controlling for baseline characteristics and in-hospital events, the year of admission did not independently predict the use of catheterization (P = 0.60). By multivariate logistic regression, recurrence of chest pain and evidence of myocardial necrosis were most closely associated with same-admission cardiac catheterization. Although clinical factors partially explain the increased use of catheterization over time, there may have also been shift towards a more aggressive practice style at the authors' institution. Further study is needed to address this possibility.
    No preview · Article · Nov 1997 · The Canadian journal of cardiology
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    ABSTRACT: The Canadian Coronary Atherectomy Trial (CCAT) assessed, in a randomized comparison, the clinical and angiographic outcomes following atherectomy with those following balloon angioplasty for the treatment of de novo lesions in the proximal one-third of the left anterior descending artery (LAD). Although the procedural success rate was somewhat higher and the postprocedure lumen larger in patients treated with atherectomy, lumen dimensions, restenosis rates and clinical outcomes were similar in the two groups at six months. To determine whether late differences emerged between the groups, clinical follow-up was obtained at a median of 18 (range 10 to 31) months after randomization. Patients were contacted monthly by telephone for the first six months. Subsequent follow-up information was obtained in 272 (99%) of the 274 randomized patients via a clinic visit or telephone interview with the patient and/or a relative. Additional information was obtained from the referring physician as required. There were no differences in adverse events between the two groups during follow-up. In patients randomized to atherectomy compared with balloon angioplasty, death occurred in 1.5% versus 2.2% (cardiac death 0.7% versus 0.7%); myocardial infarction in 5.1% versus 5.9% (Q wave 1.5% versus 1.5%); coronary bypass surgery in 13.1% versus 12.6%; and repeat target lesion intervention in 22.6% versus 21.5%. Persistent or recurrent Canadian Cardiovascular Society class III/IV angina not treated by a further intervention was present in 1.5% versus 2.2%. The combined end-point of death or nonfatal myocardial infarction occurred in nine (6.6%) versus 11 (8.1%) patients and any adverse cardiac event in 50 (36.5%) versus 53 (39.3%). Multivariate logistic regression indicated that unstable angina, reference vessel size and preprocedure minimum lumen diameter were the only variables independently associated with adverse events. The initial choice of directional atherectomy or balloon angioplasty had no impact on clinical outcome over a period of 18 months in this patient population. With either technique, just over 60% of patients with proximal LAD disease experienced sustained symptomatic improvement without an adverse event following a single procedure, and 80% achieved this status following a repeat percutaneous intervention.
    No preview · Article · Oct 1997 · The Canadian journal of cardiology
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    ABSTRACT: The objective of this study was to examine whether there are international variations in the use of evidence-based medical therapy in patients undergoing percutaneous coronary revascularization. We analyzed the medical therapy of patients in the United States (US) (n = 878), Europe (n = 134), and Canada (n = 274) who underwent percutaneous coronary revascularization in either the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT-I) (enrollment from August 1991 to April 1992) or the Canadian Coronary Atherectomy Trial (CCAT) (enrollment from July 1991 to August 1992). We found that at the time of hospital admission, Canadian patients had the highest rates of treatment with aspirin (95% vs 57% US and 78% Europe; p = 0.002), calcium antagonists (75% vs 48% US and 43% Europe; p 0.0001), beta blockers (60% vs 32% US and 46% Europe; p = 0.02), and combination anti-ischemic therapy (67% vs 43% US and 56% Europe; p = 0.0001). By discharge, however, Canadian patients had the lowest rates of treatment with nitrates (12% vs 40% US and 44% Europe; p = 0.0001) and combination anti-ischemic therapy (29% vs 53% US and 47% Europe; p < 0.01). At both admission and discharge, rates of treatment with angiotensin-converting enzyme inhibitors and lipid-lowering agents were < 15% in all 3 regions. We conclude that significant international variations exist in the use of evidence-based medical therapy in patients undergoing percutaneous coronary revascularization.
    No preview · Article · May 1997 · The American Journal of Cardiology
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    ABSTRACT: The cardioprotective role of adenosine in various models of ischemia-reperfusion, including adenosine supplementation to cardioplegic formulations, has been studied extensively. The appropriate dose of adenosine in humans is uncertain and could be limited by systemic hypotension or AV block. An open-label, nonrandomized phase 1 adenosine dose-ranging study was performed. Patients scheduled for primary isolated coronary bypass surgery were eligible for the study. Antegrade warm blood potassium cardioplegia (ratio, 4:1, blood to crystalloid) was administered in the routine fashion, with adenosine added to the initial 1000-mL dose and final 500-mL dose. Patients were studied in blocks of 4 per concentration. An escalating adenosine dosage schedule was planned to produce blood cardioplegia concentrations from 0 to 250 mumol/L, and the blocks were tested sequentially. Stopping rules were defined for systemic hypotension (phenylephrine dose during cardiopulmonary bypass > or = 5.0 mg; phenylephrine dose during cardioplegic induction > or = 800 micrograms) and AV block (permanent pacemaker insertion; temporary pacing dependency for > 90 minutes after cardiopulmonary bypass). Doses of 1, 2.5, 5, 10, and 25 mumol/L were well tolerated. With 50 mumol/L, systemic hypotension occurred during cardioplegic induction in 3 of 4 patients versus 1 of 24 (P < .005) at all lower concentrations (880 +/- 217 versus 297 +/- 286 micrograms phenylephrine per patient). The studies were repeated with an 8:1 blood-to-crystalloid cardioplegia delivery system. Adenosine concentrations of 0 (n = 4), 15 (n = 12), 20 (n = 8), and 25 mumol/L (n = 4) were tested. Hypotension during cardioplegic induction was more prevalent (P = .05) with the higher doses (15 mumol/L, 394 +/- 189 micrograms, 1 of 12 patients; 20 mumol/L, 360 +/- 355 micrograms, 2 of 8 patients; 25 mumol/L, 600 +/- 478 micrograms, 2 of 4 patients). There were no differences with respect to systemic hypotension during cardiopulmonary bypass or for pacing > 90 minutes after discontinuation of cardiopulmonary bypass, and no patient required permanent pacing. There have been no deaths, Q-wave myocardial infarctions, intra-aortic balloon pump insertions, or cerebral infarctions in the total sample of 56 patients. Our initial investigations have shown that adenosine can be safely administered during cardiopulmonary bypass. The authors recommend that further studies are warranted using adenosine 15 to 25 mumol/L, depending on the delivery system.
    No preview · Article · Nov 1996 · Circulation
  • B P Kimball · S Bui · E A Cohen · P K Cheung · V Lima
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    ABSTRACT: To examine physician bias in reporting percutaneous transluminal coronary angioplasty (PTCA) results and analyze this potential source of errors, and to examine the ability to estimate absolute lumen diameters visually, the authors reviewed 56 successful PTCAs from their institution. Pre- and postprocedural cineangiograms were blindly reviewed by an experienced consensus panel (three members) and compared with the interventional cardiologist's reported outcome (percentage diameter stenosis) and quantitative coronary angiography (QCA) using the Cardiac Measurement System. Staff cardiologists significantly overestimated pre-PTCA stenosis severity (staff 83.7 versus panel 75.2%, P < 0.05) while underestimating residual narrowing (staff 18.4 versus panel 22.8%, P < 0.05), thus exaggerating overall angioplasty benefit (staff -65.3 versus panel -52.4%, P < 0.05). The cumulative error varied greatly among individual staff members (3.4 to 18.0%). Despite these findings, the consensus panel accurately identified pre-PTCA minimum lumen diameter, as measured by quantitative angiography (panel 0.66 versus QCA 0.67 mm, not significant), although they tended to overestimate absolute postprocedural luminal dimensions (panel 2.28 versus QCA 2.00 mm, P < 0.05) and thereby ultimate changes in minimum lumen diameter (panel 1.62 versus QCA 1.33 mm, P < 0.05). Therefore, substantial bias exists in the reporting of PTCA outcomes, which tends to magnify the perceived benefits of the procedure. Well-trained observers can accurately estimate pre-PTCA absolute lumen diameters, although difficulties occur in evaluating residual dimensions.
    No preview · Article · Oct 1994 · The Canadian journal of cardiology
  • B P Kimball · S Bui · E A Cohen · R G Carere · A G Adelman
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    ABSTRACT: To evaluate evolving selection criteria and angiographic outcome ('learning curve') for directional coronary atherectomy. Tertiary referral, university-based hospital. Initial 50 subjects undergoing directional coronary atherectomy of de novo left anterior descending stenoses at The Toronto Hospital from July 1990 to April 1991. Directional coronary atherectomy according to standard interventional techniques, with pre- and post procedure qualitative evaluation and quantitative coronary arteriography (Cardiac Measurement System; Leiden, The Netherlands) to define angiographic outcome. Comparing 'early' (group 1) versus 'late' (group 2) subjects, baseline demographics and clinical parameters were similar. Later subjects demonstrated increased coronary tortuosity (group 1, 1.40 versus group 2, 1.64, P < 0.01) and major side branch involvement within the stenosis (group 1, seven of 25 [28%] versus group 2, 18 of 25 [72%], P < 0.01). Regardless of experience, post procedure residual minimum stenotic diameters were equal (group 1, 2.75 +/- 0.55 versus group 2, 2.49 +/- 0.42 mm) in progressively longer lesions (group 1, 11.4 +/- 4.9 versus group 2, 13.3 +/- 5.5 mm, P < 0.1), with increased symmetry (group 1, 0.60 +/- 0.28 versus group 2, 0.73 +/- 0.19, P < 0.05). Analysis of consecutive pentiles (10 subjects per group) indicated gradual increases in post procedure residual lumen during early experience (the first 30 subjects), with an abrupt deterioration in outcome (fourth pentile), secondary to qualitative changes in coronary anatomy, before a return to satisfactory residual minimum stenotic diameters (fifth pentile). This study defines a distinct 'learning curve' during the initial 30 patients undergoing directional coronary atherectomy, with subtle changes in case selection, predominantly reflected by qualitative indices (eg, tortuosity, dystrophic calcification), resulting in a transient deterioration in final outcomes (patient 31 to 40). Subsequently, optimal results were re-established after defining appropriate case selection criteria, in conjunction with progressive expertise.
    No preview · Article · Apr 1993 · The Canadian journal of cardiology
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    B P Kimball · S Bui · R G Carere · E A Cohen · A G Adelman
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    ABSTRACT: To assess the immediate outcome of directional coronary atherectomy (DCA) versus standard balloon angioplasty (PTCA) in de novo left anterior descending coronary stenoses, 25 consecutive atherectomies (22 men, 3 women) performed at The Toronto Hospital, between July 1990 and March 1991 were compared with 25 (14 men, 11 women) temporally matched successful angioplasties. Coronary stenoses were analyzed by quantitative arteriography, using the Coronary Measurement System (Leiden, The Netherlands), with estimation of transstenotic hemodynamics by fluid dynamic equations. Before and after procedure qualitative blood flow (TIMI criteria) was also evaluated, as was intimal haziness and coronary dissection. In comparison to PTCA, coronary atherectomy produced less residual minimum stenotic diameter (DCA, 2.75 +/- 0.55 vs PTCA, 1.70 +/- 0.44 mm, p < 0.001), and relative percent diameter stenosis (DCA, 17.9 +/- 10.7 vs PTCA, 34.4 +/- 10.7 percent, p < 0.001), with less transstenotic obstructive gradient (DCA, 0.2 +/- 0.2 vs PTCA, 1.0 +/- 1.5 mm Hg, p < 0.05), and greater estimated stenotic flow reserve (DCA, 4.86 +/- 0.15 vs PTCA, 4.50 +/- 0.48 x baseline, p < 0.05). Coronary atherectomy "normalized" TIMI flow patterns in virtually all patients (DCA, 2.96 +/- 0.20 vs PTCA, 2.72 +/- 0.45, p < 0.05), while creating less intimal haziness (DCA, 10/25 [40 percent] vs PTCA, 23/25 [92 percent], p < 0.01), and coronary dissection (DCA, 6/25 [24 percent] vs PTCA, 16/25 [64 percent], p < 0.05). Therefore, when compared with standard balloon angioplasty, DCA produces less residual stenosis, better transstenotic hemodynamics, while decreasing the frequency of coronary artery damage, in de novo left anterior descending stenoses.
    Preview · Article · Jan 1993 · Chest
  • A G Adelman · E A Cohen · R G Carere · B P Kimball
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    ABSTRACT: To assess the procedural success and complication rates of the first 120 directional coronary atherectomy cases performed at two Toronto hospitals. Case series in tertiary referral centres. One hundred and thirteen patients in whom 120 atherectomy procedures were attempted between July 1990 and April 1992. Directional coronary atherectomy. Angiographic success was obtained in 115 of 120 procedures (96%) involving 117 of 123 lesions (95%). Procedural success (angiographic success without death, myocardial infarction or coronary bypass surgery) was obtained in 110 of 120 procedures (92%). Adjunctive balloon angioplasty was required in 20 procedures (17%). There was one death at 36 h in an elderly patient who underwent an emergency procedure while in cardiogenic shock. Periprocedural non-Q wave myocardial infarction occurred in five patients. There were no Q wave myocardial infarctions. Three patients required coronary bypass surgery prior to discharge and vascular complications occurred in five patients. Directional coronary atherectomy can be performed with procedural success and complication rates comparable to conventional balloon angioplasty. Randomized trials are underway to determine if atherectomy results in a lower restenosis rate.
    No preview · Article · Oct 1992 · The Canadian journal of cardiology
  • S. Miwa · N.D. Desai · T. Koyama · E. Chan · E.A. Cohen · S.E. Fremes

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Publication Stats

357 Citations
94.46 Total Impact Points


  • 1997-1999
    • University of Toronto
      • • Division of Cardiology
      • • Sunnybrook Health Sciences Centre
      Toronto, Ontario, Canada
  • 1996-1998
    • Sunnybrook Health Sciences Centre
      Toronto, Ontario, Canada
  • 1992-1997
    • Mount Sinai Hospital, Toronto
      • Department of Cardiology
      Toronto, Ontario, Canada
  • 1993-1994
    • Toronto Western Hospital
      Toronto, Ontario, Canada