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Dive into the research topics where Leonard Schwartz is active.

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Featured researches published by Leonard Schwartz.


American Journal of Cardiology | 2001

The Quinapril Ischemic Event Trial (QUIET): evaluation of chronic ace inhibitor therapy in patients with ischemic heart disease and preserved left ventricular function

Bertram Pitt; Blair O’Neill; Robert L. Feldman; Roberto Ferrari; Leonard Schwartz; Harald Mudra; Theodore A. Bass; Carl J. Pepine; Michele Texter; Harry E. Haber; Andrew C.G. Uprichard; Linda Cashin-Hemphill; Robert S. Lees

Angiotensin-converting enzyme inhibitors improve endothelial function, inhibit experimental atherogenesis, and decrease ischemic events. The Quinapril Ischemic Event Trial was designed to test the hypothesis that quinapril 20 mg/day would reduce ischemic events (the occurrence of cardiac death, resuscitated cardiac arrest, nonfatal myocardial infarction, coronary artery bypass grafting, coronary angioplasty, or hospitalization for angina pectoris) and the angiographic progression of coronary artery disease in patients without systolic left ventricular dysfunction. A total of 1,750 patients were randomized to quinapril 20 mg/day or placebo and followed a mean of 27 +/- 0.3 months. The 38% incidence of ischemic events was similar for both groups (RR 1.04; 95% confidence interval 0.89 to 1.22; p = 0.6). There was also no significant difference in the incidence of patients having angiographic progression of coronary disease (p = 0.71). The rate of development of new coronary lesions was also similar in both groups (p = 0.35). However, there was a difference in the incidence of angioplasty for new (previously unintervened) vessels (p = 0.018). Quinapril was well tolerated in patients after angioplasty with normal left ventricular function. Quinapril 20 mg did not significantly affect the overall frequency of clinical outcomes or the progression of coronary atherosclerosis. However, the absence of the demonstrable effect of quinapril may be due to several limitations in study design.


The Journal of Thoracic and Cardiovascular Surgery | 2000

Autologous porcine heart cell transplantation improved heart function after a myocardial infarction.

Ren-Ke Li; Richard D. Weisel; Donald A.G. Mickle; Zhi-Qiang Jia; Eung-Joong Kim; Tetsuro Sakai; Shinji Tomita; Leonard Schwartz; Mark Iwanochko; Mansoor Husain; Robert J. Cusimano; Robert J. Burns; Terrence M. Yau

OBJECTIVE Fetal cardiomyocyte transplantation improved heart function after cardiac injury. However, cellular allografts were rejected despite cyclosporine (INN: ciclosporin) therapy. We therefore evaluated autologous heart cell transplantation in an adult swine model of a myocardial infarction. METHODS In 16 adult swine a myocardial infarction was created by occlusion of the distal left anterior descending coronary artery by an intraluminal coil. Four weeks after infarction, technetium 99m-sestamibi single photon emission tomography showed minimal perfusion and viability in the infarcted region. Porcine heart cells were isolated and cultured from the interventricular septum at the time of infarction and grown in vitro for 4 weeks. Through a left thoracotomy, either cells (N = 8) or culture medium (N = 8) was injected into the infarct zone. RESULTS Four weeks after cell transplantation, technetium 99m-sestamibi single photon emission tomography demonstrated greater wall motion scores in the pigs receiving transplantation than in control animals (P =.01). Pigs receiving transplantation were more likely to have an improvement in perfusion scores (P =.03). Preload recruitable stroke work (P =.009) and end-systolic elastance (P =. 02) were greater in the pigs receiving transplantation than in control animals. Scar areas were not different, but scar thickness was greater (P =.02) in pigs receiving transplantation. Cells labeled with bromodeoxyuridine in vitro could be identified in the infarct zone 4 weeks after transplantation. Swine receiving transplantation gained more weight than control animals (P =.02). CONCLUSION Autologous porcine heart cell transplantation improved regional perfusion and global ventricular function after a myocardial infarction.


Journal of the American College of Cardiology | 2011

Alcohol Septal Ablation for the Treatment of Hypertrophic Obstructive Cardiomyopathy: A Multicenter North American Registry

Sherif F. Nagueh; Bertron M. Groves; Leonard Schwartz; Karen M. Smith; Andrew Wang; Richard G. Bach; Christopher D. Nielsen; Ferdinand Leya; John M. Buergler; Steven K. Rowe; Anna Woo; Yolanda Munoz Maldonado; William H. Spencer

OBJECTIVES The purpose of the study is to identify the predictors of clinical outcome (mortality and survival without repeat septal reduction procedures) of alcohol septal ablation for the treatment of patients with hypertrophic obstructive cardiomyopathy. BACKGROUND Alcohol septal ablation is used for treatment of medically refractory hypertrophic obstructive cardiomyopathy patients with severe outflow tract obstruction. The existing literature is limited to single-center results, and predictors of clinical outcome after ablation have not been determined. Registry results can add important data. METHODS Hypertrophic obstructive cardiomyopathy patients (N = 874) who underwent alcohol septal ablation were enrolled. The majority (64%) had severe obstruction at rest, and the remaining had provocable obstruction. Before ablation, patients had severe dyspnea (New York Heart Association [NYHA] functional class III or IV: 78%) and/or severe angina (Canadian Cardiovascular Society angina class III or IV: 43%). RESULTS Significant improvement (p < 0.01) occurred after ablation (~5% in NYHA functional classes III and IV, and 8 patients in Canadian Cardiovascular Society angina class III). There were 81 deaths, and survival estimates at 1, 5, and 9 years were 97%, 86%, and 74%, respectively. Left anterior descending artery dissections occurred in 8 patients and arrhythmias in 133 patients. A lower ejection fraction at baseline, a smaller number of septal arteries injected with ethanol, a larger number of ablation procedures per patient, a higher septal thickness post-ablation, and the use beta-blockers post-ablation predicted mortality. CONCLUSIONS Variables that predict mortality after ablation, include baseline ejection fraction and NYHA functional class, the number of septal arteries injected with ethanol, post-ablation septal thickness, beta-blocker use, and the number of ablation procedures.


Circulation | 1979

The extraction of circulating catecholamines by the lungs in normal man and in patients with pulmonary hypertension.

Michael J. Sole; M Drobac; Leonard Schwartz; M N Hussain; E F Vaughan-Neil

We directly measured the net pulmonary extraction of circulating norepinephrine, epinephrine and dopamine in control patients and patients with primary or secondary pulmonary hypertension. Mixed pulmonary artery norepinephrine, epinephrine and dopamine were 314 ± 13 pg/ml, 102 ± 9 pg/mI, 51 ± 5 pg/mi, respectively, for the control group; values were similar in patients with pulmonary hypertension. The pulmonary extraction of norepinephrine was 25.4 ± 2.6% (clearance 266 ± 62 ng/min) in control patients; epinephrine and dopamine were not extracted. There was no net extraction or production of any of the three catecholamines by the lungs in any of the patients with pulmonary hypertension. We conclude that the lungs play a significant role in the inactivation of circulating norepinephrine in man. This metabolic function of the lungs appears to be lost in pulmonary hypertension.


Circulation | 2002

Coronary Bypass Graft Patency in Patients With Diabetes in the Bypass Angioplasty Revascularization Investigation (BARI)

Leonard Schwartz; Kevin E. Kip; Robert L. Frye; Edwin L. Alderman; Hartzell V. Schaff; Katherine M. Detre

Background—Few studies have compared long-term status of bypass grafts between patients with and without diabetes, and uncertainty exists as to whether diabetes independently predicts poor clinical outcome after CABG. Methods and Results—Among 1526 patients in BARI who underwent CABG as initial revascularization, 99 of 292 (34%) with treated diabetes mellitus (TDM) (those on insulin or oral hypoglycemic agents) and 469 of 1234 (38%) without TDM had follow-up angiography. Angiograms with the longest interval from initial surgery and before any percutaneous graft intervention (mean 3.9 years) were reviewed. An average of 3.0 grafts were placed at initial CABG for patients with TDM (n=297; internal mammary artery [IMA], 33%) and 2.9 grafts for patients without TDM (n=1347; IMA, 34%). Patients with TDM were more likely than those without to have small (<1.5 mm) grafted distal vessels (29% versus 22%) and vessels of poor quality (9% versus 6%). On follow-up angiography, 89% of IMA grafts were free of stenoses ≥50% among patients with TDM versus 85% among patients without TDM (P =0.23). For vein grafts, the corresponding percentages were 71% versus 75% (P =0.40). After statistical adjustment, TDM was unrelated to having a graft stenosis ≥50% (adjusted odds ratio, 0.87; 95% CI, 0.58 to 1.32). Conclusions—Despite diabetic patients’ having smaller distal vessels and vessels judged to be of poorer quality, diabetes does not appear to adversely affect patency of IMA or vein grafts over an average of 4-year follow-up. Previously observed differences in survival between CABG-treated patients with and without diabetes may be largely a result of differential risk of mortality from noncardiac causes.


Journal of the American College of Cardiology | 2011

Long-term survival in patients with resting obstructive hypertrophic cardiomyopathy comparison of conservative versus invasive treatment.

Warren Ball; Joan Ivanov; Harry Rakowski; E. Douglas Wigle; Meredith Linghorne; Anthony Ralph-Edwards; William G. Williams; Leonard Schwartz; Ashley Guttman; Anna Woo

OBJECTIVES The aim of this study was to compare the survival of patients with hypertrophic cardiomyopathy (HCM) and resting left ventricular outflow tract (LVOT) obstruction managed with an invasive versus a conservative strategy. BACKGROUND In patients with resting obstructive HCM, clinical benefit can be achieved after invasive septal reduction therapy. However, it remains controversial whether invasive treatment improves long-term survival. METHODS We studied a consecutive cohort of 649 patients with resting obstructive HCM. Total and HCM-related mortality were compared in 246 patients who were conservatively managed with 403 patients who were invasively managed by surgical myectomy, septal ethanol ablation, or dual-chamber pacing. RESULTS Multivariable analyses (with invasive therapy treated as a time-dependent covariate) showed that an invasive intervention was a significant determinant of overall mortality (hazard ratio: 0.6, 95% confidence interval: 0.4 to 0.97, p = 0.04). Overall survival rates were greater in the invasive (99.2% 1-year, 95.7% 5-year, and 87.8% 10-year survival) than in the conservative (97.3% 1-year, 91.1% 5-year, and 75.8% 10-year survival, p = 0.008) cohort. However, invasive therapy was not found to be a significant independent predictor of HCM-related mortality (hazard ratio: 0.7, 95% confidence interval: 0.4 to 1.3, p = 0.3). The HCM-related survival was 99.5% (1 year), 96.3% (5 years), and 90.2% (10 years) in the invasive cohort, and 97.8% (1 year), 94.6% (5 years), and 86.9% (10 years) in the conservative cohort (p = 0.3). CONCLUSIONS Patients treated invasively have an overall survival advantage compared with conservatively treated patients, with the latter group more likely to die from noncardiac causes. The HCM-related mortality is similar, regardless of a conservative versus invasive strategy.


American Heart Journal | 2008

Decreased complication rates using the transradial compared to the transfemoral approach in percutaneous coronary intervention in the era of routine stenting and glycoprotein platelet IIb/IIIa inhibitor use: A large single-center experience

Jonas Eichhöfer; Eric Horlick; Joan Ivanov; Peter H. Seidelin; John R. Ross; Douglas Ing; Paul Daly; Karen Mackie; Brenda Ridley; Leonard Schwartz; Alan Barolet; Vladimír Džavík

BACKGROUND Studies evaluating the efficacy and safety of the transradial approach for percutaneous coronary intervention (PCI) were carried out mainly before the widespread use of stents and glycoprotein (GP) IIb/IIIa inhibitors. We sought to determine the association between the choice of the vascular access site and procedural complications after PCI performed with routine stenting and GP IIb/IIIa inhibition. METHODS The data source was a prospective registry of 13,499 consecutive cases of PCI at the University Health Network, Toronto, Canada, from April 2000 to September 2006. Logistic regression was used to calculate the probability of selection to the radial access group. Using propensity score methodology, 3,198 patients with femoral access were randomly matched to 3,198 patients with radial access based on clinical, angiographic, and procedural characteristics. Multivariable logistic regression analysis was used to identify the independent predictors of access site-related complications. Major adverse cardiac event was defined as death, myocardial infarction, abrupt vessel closure, or coronary artery bypass surgery. RESULTS Use of the transradial approach was associated with fewer vascular access complications (1.5% vs 0.6%, P<.001) and a shorter length of hospital stay. Multivariable analysis revealed transradial access (OR 0.39, 95% CI 0.2-0.7) to be an independent predictor of lower risk, whereas primary PCI (OR 4.36, 95% CI 1.4, 13), recent myocardial infarction (OR 2.0 95% CI 1.2, 3.4), age (per 10 years increase: OR 1.37, 95% CI 1.1-1.7) and female gender (0R 2.78 95% CI 1.7, 4.6) were independent predictors of a higher risk of access site complications. CONCLUSIONS Use of transradial access for PCI is safe and is independently associated with a reduced rate of in-hospital access site complications and reduced length of hospital stay.


Journal of the American College of Cardiology | 1990

Percutaneous coronary laser balloon angioplasty: Initial results of a multicenter experience

James Richard Spears; Vincent P. Reyes; Joshua Wynne; Barbara S. Fromm; Edward L. Sinofsky; Scott Andrus; Lan Nigel Sinclair; Barry E. Hopkins; Leonard Schwartz; Harold E. Aldridge; H.W.Thijs Plokker; E.G. Mast; Anthony F. Rickards; Merril L. Knudtson; Ulrich Sigwart; Wayne E. Dear; James J. Ferguson; Paolo Angelini; Louis L. Leatherman; Robert D. Safian; Ronald D. Jenkins; John S. Douglas; Spencer B. King

A multicenter clinical trial was initiated to test the potential safety and short-term efficacy of a percutaneous coronary application of laser balloon angioplasty, which has been shown experimentally to alleviate the common causes (dissection, recoil, thrombus) of suboptimal luminal results of conventional balloon angioplasty. Fifty-five patients, the majority (62%) of whom had relatively high risk lesions, were treated in 10 centers with a laser balloon that was identical in size (3 x 20 mm) to a balloon used for conventional balloon angioplasty performed on the same lesion immediately before laser balloon angioplasty. One or more neodymium:yttrium aluminum garnet (Nd:YAG) (1,060 nm) laser doses of 250 to 450 J were each delivered over a 20 s duration per exposure. Immediately and 1 day after laser balloon angioplasty no significant adverse effects on the arterial lumen were noted in any patient. By computerized image analysis of cineangiograms initial conventional balloon angioplasty failed to achieve a minimal luminal diameter greater than 1.5 mm in 14 patients (25%), including 3 patients with acute closure. However, after subsequent laser balloon angioplasty, minimal luminal diameter exceeded this value in all patients including this subgroup. Overall, minimal luminal diameter increased from 1.74 +/- 0.46 mm after conventional balloon angioplasty to 2.32 +/- 0.31 mm after laser balloon angioplasty (p less than 0.001) with no change found on 1 day and 1 month follow-up angiograms. Thus, laser balloon angioplasty is a safe, effective procedure for improving luminal dimensions after conventional balloon angioplasty.


Life Sciences | 1979

Plasma dopamine responses to standing and exercise in man

Glen R. Van Loon; Leonard Schwartz; Michael J. Sole

Abstract Increases in plasma concentration of dopamine in response to standing are comparable to those observed for norepinephrine and epinephrine. Also, bicycle exercise to maximum heart rate produced 1.5 to 2.5-fold increases above basal plasma concentrations in each of the three catecholamines. Thus, maneouvres which are associated with increases in sympathetic activity are associated with parallel increases in each of the three catecholamines. However, the origin and significance of plasma dopamine remain unknown.


American Journal of Cardiology | 1975

Severe Alcoholic Cardiomyopathy Reversed with Abstention from Alcohol

Leonard Schwartz; Karen Sample; E.Douglas Wigle

In a chronic alcoholic with a severe congestive cardiomyopathy the angiographic and hemodynamic evidence of left ventricular dysfunction was completely reversed after 1 year of abstinence. At the time of initial presentation two of the traditional hallmarks of a poor prognosis were present, namely, a long exposure to alcohol before the onset of symptoms and severe diffuse left ventricular dilation and hypokinesis (ejection fraction 14.9 percent). Yet, today, 18 months later he is asymptomatic, receiving no medications and has normal left ventricular function. A reexamination of prognostic factors in alcoholic cardiomyopathy may be indicated.

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Anna Woo

Toronto General Hospital

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Harry Rakowski

University Health Network

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Joan Ivanov

University Health Network

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Alan Barolet

University Health Network

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Hugh E. Scully

Toronto General Hospital

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