Search PubMed⌕ Search

Biomedical subjects

R Shabetai

Publications and source records attributed to R Shabetai.

At least 19 recordsLinked to original sources
PubMed2001

Effect of pravastatin-to-simvastatin conversion on low-density-lipoprotein cholesterol.

The effects of a pravastatin-to-simvastatin conversion program on low-density-lipoprotein (LDL) cholesterol levels were studied. Patients receiving pravastatin at a Veterans Affairs medical center were switched to simvastatin beginning in 1997. The dosage of simvastatin was based on the additional percent reduction in LDL cholesterol needed to achieve the goal specified by the National Cholesterol Education Program. The primary endpoint was the change in the percentage of patients meeting their LDL cholesterol goal at baseline and follow-up. Changes in lipid indices, the relative risk (RR) of coronary heart disease (CHD), and program costs were also evaluated. A total of 1032 patients completed the program. The mean +/- S.D. daily doses of pravastatin and simvastatin were 25.2 +/- 11.3 and 22.7 +/- 13.3 mg, respectively. Median baseline and follow-up LDL cholesterol concentrations were 116 and 99 mg/dL, respectively (p < 0.001). Overall, 44% of the patients met their LDL cholesterol goal while taking pravastatin, compared with 69% after conversion to simvastatin (p < 0.001). The predicted mean RR of a future CHD event (based on changes in serum lipids) was 0.87 (95% confidence interval, 0.83-0.91) four years after conversion. The total cost of the program was $40,644 in the first year, and there was a net saving thereafter. Therapeutic interchange between pravastatin and simvastatin increased the number of patients meeting their LDL cholesterol goal.

Aged↗
PubMed2000

Sarcoidosis and the Heart.

The treatment of sarcoid cardiomyopathy can be considered in part the treatment of the systemic disorder, and in part cardiac involvement, the manifestations of which may differ greatly. Therapy for the systemic disease is corticosteroid. Therapy for cardiac involvement includes prednisone, but because treatment must ameliorate or abolish many differing manifestations, therapy differs among patients. Asymptomatic patients (the majority) who are free from serious manifestations of the disease do not require pharmacologic or interventional treatment. Patients with dilated cardiomyopathy require treatment for congestive heart failure. High-grade atrioventricular conduction delay usually necessitates a permanent electronic pacemaker. Life-threatening arrhythmia usually requires implantation of an automatic implantable cardiac defibrillator (AICD). Antiarrhythmic drugs may also be needed. Cardiac tamponade should be treated by drainage of pericardial fluid. Pericardiectomy is usually the appropriate treatment for patients who develop significant constrictive pericarditis. Calcium channel blockers may be helpful for severe diastolic dysfunction that occurs in those with restrictive cardiomyopathy. Therapy should be given to those few patients who manifest hypertrophic cardiomyopathy to relieve left ventricular outflow obstruction. Cardiac transplantation for intractable heart failure or arrhythmia may be needed.

Journal Article↗
PubMed1999

Function of the normal pericardium.

Until recently, instrumenting the pericardium was possible only when a pericardial effusion is present or by surgical exposure of the pericardium. Techniques are now being developed to instrument the normal pericardium. This development will allow clinicians and investigators to study pericardial fluid in health and in a variety of disorders not associated with pericardial effusion. It will also be possible to improve our knowledge of pericardial pressure and the pericardial restraints on the heart.

Animals↗
PubMed1998

The electrocardiographic exercise test in a population with reduced workup bias: diagnostic performance, computerized interpretation, and multivariable prediction. Veterans Affairs Cooperative Study in Health Services #016 (QUEXTA) Study Group. Quantitative Exercise Testing and Angiography.

BACKGROUND: Empirical scores, computerized ST-segment measurements, and equations have been proposed as tools for improving the diagnostic performance of the exercise test. OBJECTIVE: To compare the diagnostic utility of these scores, measurements, and equations with that of visual ST-segment measurements in patients with reduced workup bias. DESIGN: Prospective analysis. SETTING: 12 university-affiliated Veterans Affairs Medical Centers. PATIENTS: 814 consecutive patients who presented with angina pectoris and agreed to undergo both exercise testing and coronary angiography. MEASUREMENTS: Digital electrocardiographic recorders and angiographic calipers were used for testing at each site, and test results were sent to core laboratories. RESULTS: Although 25% of patients had previously had testing, workup bias was reduced, as shown by comparison with a pilot study group. This reduction resulted in a sensitivity of 45% and a specificity of 85% for visual analysis. Computerized measurements and visual analysis had similar diagnostic power. Equations incorporating nonelectrocardiographic variables and either visual or computerized ST-segment measurement had similar discrimination and were superior to single ST-segment measurements. These equations correctly classified 5 more patients of every 100 tested (areas under the receiver-operating characteristic curve, 0.80 for equations and 0.68 for visual analysis; P < 0.001) in this population with a 50% prevalence of disease. CONCLUSIONS: Standard exercise tests had lower sensitivity but higher specificity in this population with reduced work-up bias than in previous studies. Computerized ST-segment measurements were similar to visual ST-segment measurements made by cardiologists. Considering more than ST-segment measurements can enhance the diagnostic power of the exercise test.

Adult↗
PubMed1998

Loss of adrenergic control of the force-frequency relation in heart failure secondary to idiopathic or ischemic cardiomyopathy.

This study was designed to determine whether the force-frequency effect on myocardial contractility, known to be importantly regulated by the adrenergic nervous system in experimental animals, can be enhanced by beta-adrenergic receptor stimulation in patients with heart failure. Animal experiments have demonstrated that the positive force-frequency relation in most mammals is subject to enhancement by beta-adrenergic receptor stimulation during exercise or infusion of a beta-receptor agonist. In animal models of heart failure, this regulatory mechanism generally is lost. The response to progressive increases in heart rate to 150 to 160 beats/min by right atrial pacing before and during dobutamine infusion was studied in 3 relatively normal subjects and in 5 patients with severe dilated cardiomyopathy. Left ventricular (LV) pressure and its first derivative (LV dP/dt(max)) were measured with a micromanometer, and the time constant of LV relaxation was assessed. The slopes of the relations between heart rate and LV dP/dt(max) in control subjects were positive at baseline and the mean slope increased substantially and significantly during dobutamine infusion. In patients with heart failure, the heart rate versus LV dP/dt(max) relations were depressed and flattened without a descending limb. Dobutamine infusion shifted this relation upward slightly, without increase in mean slope, indicating lack of amplification. The rate of isovolumic relaxation significantly decreased as heart rate increased at baseline and was further shortened by dobutamine. In patients with heart failure, a depressed and flattened relation between heart rate and LV dP/dt(max) (force-frequency effect) did not show the amplification of myocardial contractility by beta-adrenergic stimulation observed in the normal heart. This abnormality in control of the force-frequency relation undoubtedly plays an important role in the impairment of cardiac function during exercise in heart failure.

Adrenergic beta-Agonists↗
PubMed1997

Pravastatin alone and in combination with low-dose cholestyramine in patients with primary hypercholesterolemia and coronary artery disease.

This randomized, open-label study compared the cost efficiency of low-dose pravastatin combined with low-dose cholestyramine with high-dose pravastatin monotherapy in 59 patients with moderate hypercholesterolemia and coronary disease. Both regimes were effective in improving lipid profiles in these patients; however, low-dose combination therapy enhanced achievement in therapeutic goals and cost efficiency.

Adult↗
PubMed1997

Idiopathic giant-cell myocarditis--natural history and treatment. Multicenter Giant Cell Myocarditis Study Group Investigators.

BACKGROUND: Idiopathic giant-cell myocarditis is a rare and frequently fatal disorder. We used a multicenter data base to define the natural history of giant-cell myocarditis and the effect of treatment. METHODS: We identified 63 patients with idiopathic giant-cell myocarditis through journal announcements and direct mailings to cardiovascular centers worldwide. RESULTS: The patients consisted of 33 men and 30 women with an average age of 42.6 years; 88 percent were white, 5 percent were black, 5 percent were Southeast Asian or Indian, and 2 percent were Middle Eastern. Most presented with congestive heart failure (47 patients, or 75 percent), ventricular arrhythmia (9 patients, or 14 percent), or heart block (3 patients, or 5 percent), although in some cases the initial symptoms resembled those of acute myocardial infarction (4 patients). Nineteen percent had associated autoimmune disorders. The rate of survival was worse than among 111 patients with lymphocytic myocarditis in the Myocarditis Treatment Trial (P<0.001); among our patients, the rate of death or cardiac transplantation was 89 percent, and median survival was only 5.5 months from the onset of symptoms. The 22 patients treated with corticosteroids and cyclosporine, azathioprine, or both therapies survived for an average of 12.3 months, as compared with an average of 3.0 months for the 30 patients who received no immunosuppressive therapy (P=0.001). Of the 34 patients who underwent heart transplantation, 9 (26 percent) had a giant-cell infiltrate in the transplanted heart and 1 died of recurrent giant-cell myocarditis. CONCLUSIONS: Giant-cell myocarditis is a disease of relatively young, predominantly healthy adults. Patients usually die of heart failure and ventricular arrhythmia unless cardiac transplantation is performed. Despite the possibility of fatal disease recurrence, transplantation is the treatment of choice for most patients.

Adolescent↗
PubMed1996

Regional deficits of myocardial blood flow and function in left ventricular pacing-induced heart failure.

BACKGROUND: Pacing-induced congestive hear, failure has become a preferred model for the study of the pathogenesis of dilated cardiomyopathy. However, little is known regarding regional myocardial blood flow and function during the development of heart failure in this model. METHODS AND RESULTS: To determine whether regional differences in myocardial blood flow are associated with regional dysfunction in ventricular pacing-induced heart failure, regional myocardial blood flow (radioactive microspheres) and regional wall thickening (transthoracic echocardiography) were measured in pigs studied at weekly intervals during the progression of heart failure induced by rapid pacing from the lateral wall of the left ventricle (220 +/- 9 bpm for 26 +/- 4 days). Echocardiography and hemodynamic measurements with the pacemaker off showed progressive, severe global left ventricular dysfunction. During pacing over the 3- to 4-week period, a progressive decrease in systolic wall thickening in the lateral wall occurred compared with the interventricular septum (IVS; P = .001); at 21 to 28 days, the difference was 50% (lateral wall, 14 +/- 6%; IVS, 28 +/- 6%; P = .0001). A difference in subendocardial blood flow per beat between the left ventricular lateral wall (the site of stimulation) and the IVS was found immediately on the initiation of pacing (IVS, 0.009 +/- 0.002 mL.min-1.g-1.beat-1; lateral wall, 0.005 +/- 0.001 mL.min-1.g-1.beat-1; P = .001), a difference that was sustained during pacing throughout the study. Subendocardial blood flow per beat was normal in both regions with the pacemaker off throughout the study. CONCLUSIONS: These data indicate that regional myocardial ischemia is associated with the development of contractile dysfunction of the paced wall during prolonged rapid left ventricular pacing and that regional stunning contributes to persistent global left ventricular dysfunction when pacing is discontinued.

Adenosine Diphosphate↗
PubMed1996

A new method of calibrating left ventricular pressure tracings obtained from micromanometers.

An improved method of calibrating indwelling, or acutely inserted high fidelity micromanometers is presented. The proposed technique consists of linear regression of pressure data obtained from a fluid filled lumen with those obtained from a micromanometer and applying this regression equation to the data obtained from the micromanometer. The conventional calibration technique of matching systolic and late diastolic pressures was developed before analog to digital converters were available on-line in most laboratories. This method can result in erroneous hemodynamic measurements derived from the high fidelity recordings depending on the amount of ringing observed in the pressure recordings from a fluid filled transducer.

Blood Pressure Determination↗
PubMed1996

Mechanisms of venous return and ventricular filling in elasmobranch fish.

The current concept of ventricular filling in the elasmobranch fish (sharks and rays) is that a subambient pericardial pressure establishes a negative diastolic pressure gradient for the atrium and that ventricular end-diastolic volume is exclusively determined by atrial systole. In contrast, recent findings using echo-Doppler and digital imaging techniques have demonstrated two filling phases in the elasmobranch ventricle. In this study, simultaneous atrial and ventricular pressure measurements made on sharks with an open or intact pericardium establish that atrial pressure is above ventricular diastolic pressure until the onset of ventricular systole. A positive biphasic atrioventricular pressure gradient thus ensures ventricular filling during early diastole, as a result of ventricular relaxation, as well as during atrial systole. Although a reduction in pericardial pressure resulted in a decline in the atrial and ventricular pressure, a positive atrioventricular pressure gradient is conserved. The finding that atrial diastolic pressure is not lower than ventricular diastolic pressure, when combined with previous results showing that pericardial pressure is generally at or above ambient and that ventricular filling is biphasic, constitutes a strong body of evidence favoring the operation of a direct venous inflow as the mechanism by which the elasmobranch heart fills.

Animals↗
PubMed1995

Heterogeneity of vasomotor response to acetylcholine along the human coronary artery.

OBJECTIVES: In view of the segmental occurrence of coronary atherosclerosis, we postulated that acetylcholine may cause heterogeneous vasomotion, depending on the extent of vessel analyzed, criteria for change in vessel caliber and dose of drug administered. BACKGROUND: Previous studies have reported that acetylcholine causes constriction of atherosclerotic arteries. This dysfunction of endothelium-dependent dilation may be seen without angiographically detectable disease. METHODS: We developed algorithms to quantitate the dimensions of a single coronary artery over virtually its entire length during a control state and during graded doses of intracoronary acetylcholine. On the basis of triplicate control angiograms, the limit of detection of a change from control diameter was 0.31 mm (> or = 2 SD). RESULTS: Analysis of multiple segments (each 5.6 +/- 1.1 [mean +/- SD] mm) along a single coronary artery revealed a heterogeneous response to acetylcholine in 27 of 31 patients at the 10(-4) mol/liter dose and in 29 of 31 patients when responses at 10(-6), 10(-5) and 10(-4) mol/liter doses were combined; in this latter analysis, constriction and dilation in the same vessel occurred in 45% of the patients. With acetylcholine, most of 349 segments demonstrated no change, but the greatest frequency of vasoconstriction (24.6%) and vasodilation (6.9%) was seen at the 10(-4) mol/liter dose. Inducible vasomotion was observed as far distally as 7.3 cm from the site of acetylcholine infusion. CONCLUSIONS: Response to intracoronary acetylcholine with mild coronary disease is heterogeneous; disparate dimensional responses may occur in different segments of the same vessel. Inclusion of all analyzable regions of a coronary artery and the use of a reproducibility limit for quantitative angiography are optimal for assessment of segmental coronary vasomotion.

Acetylcholine↗