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Biomedical subjects

S H Rahimtoola

Publications and source records attributed to S H Rahimtoola.

At least 19 recordsLinked to original sources
PubMed1992

Hibernating myocardium: a historical perspective.

Hibernating myocardium refers to the presence of persistent myocardial and left ventricular dysfunction at rest, associated with conditions of severely reduced coronary blood flow. This left ventricular dysfunction probably represents an adaptive mechanism preventing irreversible myocardial cell damage, since myocardial and left ventricular dysfunction in hibernating myocardium improve following the restoration of coronary blood flow. This review examines the evolution of the concept of hibernation from a clinical observation of the potential underlying mechanisms recently proposed.

Adenosine Triphosphate↗
PubMed1992

Detection of acute myocardial infarction with digital image processing of two-dimensional echocardiograms.

We have previously described the ability of a computer-based image digitizing system to assess early textural changes in acute canine myocardial infarction. To determine whether this technique could be applied to human beings, we studied 12 patients with a first acute transmural myocardial infarction and five normal subjects. Two-dimensional echocardiograms were performed on days 1 and 8 in normal subjects and on days 1 (day of admission), 2, 3, 5, and 14 in the patient population. All recording parameters on the echocardiography machine were kept identical for serial studies. The mean period between hospitalization and first echocardiogram was 11.1 hours (range 4 to 20 hours). End-diastolic frames from the two-dimensional echocardiographic images were digitized and displayed on a monitor. The mean pixel intensity (MPI) (+/- SD) in the region of asynergy (area of myocardial infarction) and a normal area were determined. In normal volunteers, no significant change in MPI was noted between anteroseptal and lateral areas on two separate two-dimensional echocardiographic studies, which were performed 7 days apart (anteroseptal: MPI, 21.6 +/- 1.1 vs 21.8 +/- 0.4, p = not significant) and (lateral: MPI, 21.5 +/- 1.2 vs 21.4 +/- 1.4, p = not significant). In patients with myocardial infarction, a significant increase in MPI was noted on the first day of myocardial infarction between normal and infarcted myocardium (20.4 +/- 2.0 vs 24.3 +/- 2.3, p less than 0.05) and progressively increased thereafter until day 14 (20.5 +/- 1.7 vs 31.9 +/- 3.7, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiography↗
PubMed1992

Prognostic significance of programmed ventricular stimulation in patients surviving complicated acute myocardial infarction: a prospective study.

In survivors of complicated myocardial infarction, the inducibility of sustained ventricular tachycardia may help identify a subset that is at increased risk for subsequent sudden cardiac death or spontaneous sustained ventricular tachycardia. We performed prehospital discharge programmed ventricular stimulation in 86 survivors of acute myocardial infarction complicated by heart failure, angina pectoris, or nonsustained ventricular tachycardia. These patients also underwent cardiac catheterization with coronary angiography and 24-hour ambulatory ECG recording. Programmed ventricular stimulation induced sustained ventricular tachycardia in 19 patients (22%) and ventricular fibrillation in six (7%) and did not induce these arrhythmias in 61 patients (71%). During an average follow-up of 18 +/- 13 months, 11 patients had arrhythmic events (seven sudden death and four nonfatal spontaneous sustained ventricular tachycardia) and 10 patients had nonsudden cardiac death. The total cardiac mortality rate was 20%. Arrhythmic events occurred in 32% of the 19 patients with inducible sustained ventricular tachycardia compared with 7% of the remaining 67 patients (p less than 0.003). By multivariate analysis the occurrence of arrhythmic events was independently predicted by both inducible sustained ventricular tachycardia and Killip class III or IV heart failure. The risk of arrhythmic events was 4.4% in the absence of both variables versus 38.4% (p less than 0.001) when both variables were present. The total cardiac mortality rate was best predicted by low left ventricular ejection fraction (less than 30%). Thus programmed ventricular stimulation is useful in risk stratification of survivors of complicated acute myocardial infarction. The prognostic utility appears to be particularly high in patients with infarction complicated by Killip class III or IV heart failure.

Arrhythmias, Cardiac↗
PubMed1992

Abnormalities of diastolic filling of the left ventricle associated with aging are less pronounced in exercise-trained individuals.

To determine whether exercise training has an effect on left ventricular diastolic dysfunction associated with the normal aging process, we studied a group of 20 normal healthy adult distance runners (mean miles currently run per week was 45 for an average of 15 years) and 20 normal healthy sedentary individuals (who currently walk less than 1 mile per day and are not involved in a regular exercise program) matched for age and systolic and diastolic blood pressure with the runners. Doppler echocardiographic indices of left ventricular diastolic filling were significantly different between the two groups. The exercise group when compared with the sedentary group had significantly decreased late diastolic peak filling velocity (0.51 +/- 0.11 m/sec versus 0.66 +/- 0.20 m/sec; p = 0.003), late diastolic velocity-time integral (5.2 +/- 1.5 cm versus 6.6 +/- 2.2 cm; p = 0.02), increased early-to-late peak filling velocity ratio (1.29 +/- 0.38 versus 0.96 +/- 0.24; p = 0.001), and early-to-late velocity-time integral ratio (2.08 +/- 0.51 versus 1.42 +/- 0.47; p less than 0.001). We conclude that the left ventricular diastolic dysfunction associated with "normal" aging is less pronounced in those persons who are exercise-trained.

Aging↗
PubMed1992

Response of angina and ischemia to long-term treatment in patients with chronic stable angina: a double-blind randomized individualized dosing trial of nifedipine, propranolol and their combination.

Seventy-four patients with chronic stable mild angina, mild coronary artery disease (83% had one- or two-vessel disease) and normal left ventricular function were studied to measure the response of treadmill exercise performance and painful and silent ischemia in the ambulatory setting to randomly assigned treatment with nifedipine or propranolol and their combination; titration to maximal tolerated dosages was performed in double-blind manner. At 3 months both nifedipine and propranolol reduced the weekly angina rate (p less than 0.05); during treadmill exercise testing, increases (p less than 0.05) were noted in time to angina and total exercise time and decreases in maximal ST depression at the end of exercise. There were no differences between the responses to nifedipine and propranolol and no significant additional changes were seen after another 3 months of therapy. The combination of nifedipine and propranolol reduced the number of patients with angina on exercise treadmill testing from 64% to 38% (p less than 0.05). During ambulatory electrocardiographic monitoring before treatment, there were 1.4 +/- 2.4 (mean +/- SD) episodes/24 h of painful ischemia and a very low silent ischemia frequency: mean 1.1 +/- 2.7 episodes/24 h, mean duration 16 +/- 25 min/24 h. Treatment with propranolol and nifedipine resulted in reduction of episodes and duration of painful and painless ischemia; approximately 77% of patients were free of all ischemic episodes. It is concluded that patients with chronic stable mild angina have a low incidence of silent ischemia. Nifedipine or propranolol alone, titrated to individualized maximally tolerated dosages, are equally effective in long-term control of painful and painless ischemia, anginal episodes and exercise-induced ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1992

Management of heart failure in valve regurgitation.

Heart failure from valve regurgitation usually results from aortic and/or mitral valve dysfunction. Heart failure resulting from acute and chronic valve regurgitation should be considered separately.

Acute Disease↗
PubMed1991

Chagas' heart disease in the United States.

BACKGROUND AND METHODS: Chagas' heart disease is believed to be rare in the United States, although many persons from countries where the disease is endemic reside here. We performed a retrospective case review and prospective follow-up of 25 patients with Chagas' heart disease and no obstructive coronary artery disease on angiography. RESULTS: The patients mainly presented with symptomatic atrioventricular block, congestive heart failure, anginal chest pain, sudden death averted by resuscitation, or sustained ventricular tachycardia. Of the 25 patients, 18 had been treated for coronary artery disease or idiopathic dilated cardiomyopathy for up to 108 months before the diagnosis of Chagas' disease was considered. The electrocardiograms frequently suggested coronary artery disease. Six of the seven patients who had exercise thallium-perfusion scans had abnormalities suggesting ischemia or infarction. A left ventricular aneurysm was found in 14 of the 25 patients, segmental akinesia or hypokinesia in 5, and diffuse hypokinesia in 3. Programmed ventricular stimulation performed in 13 patients induced sustained ventricular tachycardia in 9 and nonsustained ventricular tachycardia in 2. Actuarial survival (mean +/- SE) after four years for the entire group was 56 +/- 12 percent; it was 32 +/- 16 percent among those with global left ventricular dysfunction, and 78 +/- 14 percent among those without such dysfunction (P = 0.03). Only patients with left ventricular dysfunction or an aneurysm died (four-year survival, 45 +/- 14 percent, as compared with 100 percent for the remaining patients; P = 0.0002). Heart failure and left ventricular aneurysm or dysfunction were the only independent predictors of death. Nine patients required permanent pacemakers. CONCLUSIONS: In the United States, Chagas' heart disease commonly mimics coronary artery disease or idiopathic dilated cardiomyopathy. The prognosis is poor for patients with heart failure or left ventricular aneurysm or dysfunction. The disease may be underdiagnosed in the United States.

Chagas Cardiomyopathy↗
PubMed1991

Current role of digitalis therapy in patients with congestive heart failure.

Digitalis has been used in the treatment of chronic congestive heart failure for 215 years. In this article, numerous clinical studies and trials that have evaluated the efficacy of digitalis in the treatment of patients with congestive heart failure are reviewed. The data indicate that digitalis is a valuable therapeutic agent for relieving symptoms and improving exercise performance and left ventricular function in patients with congestive heart failure. Comparison of the various advantages and disadvantages of digitalis with alternative therapies in patients with congestive heart failure shows an important continuing role for digitalis therapy.

Clinical Trials as Topic↗
PubMed1991

A prospective evaluation of the immediate reproducibility of the signal-averaged ECG.

The purpose of this investigation was to prospectively evaluate the immediate reproducibility of the signal-averaged electrocardiogram (SAECG). A total of 114 patients undergoing evaluation for ventricular arrhythmias were enrolled in this protocol. Two consecutive SAECG's (40 Hz bidirectional high-pass filtering with a computer-automated system) were performed 10 minutes apart. Abnormal SAECG parameters were defined as (1) vector QRS duration more than 120 msec, (2) terminal root mean square (RMS) voltage less than 20 microV, and (3) low-amplitude signal (LAS) duration more than 40 msec. An SAECG was defined as abnormal if at least one vector parameter was abnormal. There was close correlation between vector parameters during the two SAECG observations: QRS duration had the highest reproducibility (r2 = 0.97, p less than 0.001) followed by terminal RMS voltage (r2 = 0.92, p less than 0.001), and LAS duration (r2 = 0.90, p less than 0.001). The mean (+/- SD) percentage of change between the two recordings was 2% +/- 2% of the QRS duration, 13% +/- 22% for terminal RMS voltage, and 7% +/- 11% for LAS duration. The reproducibility of an initially normal SAECG was 92% and of an initially abnormal SAECG, 96%. Seventeen patients (15%) had a change in one of the three vector parameters between the two recordings. There were no clinically significant differences between the 17 patients in whom the SAECG was nonreproducible and the 97 patients in whom the SAECG was reproducible. However, reproducibility was significantly higher in patients with an initially normal versus an initially abnormal SAECG (92% vs 76%, p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1991

Risk stratification in survivors of acute myocardial infarction: routine cardiac catheterization and angiography is a reasonable approach in most patients.

Noninvasive risk assessment in survivors of AMI can effectively subdivide patients into groups with differing risk profiles after hospital discharge, but some patients at risk for late death or recurrent AMI may be incorrectly identified; data from cardiac catheterization and angiography provide complementary and generally more powerful prognostic information. Many patients may derive particular benefit from early cardiac catheterization and angiography, including: (1) patients with AMI complicated by recurrent myocardial ischemia, congestive heart failure, and/or complex ventricular arrhythmias; (2) patients with abnormal or inconclusive results of noninvasive testing or those patients unable to perform an exercise test; (3) patients with abnormal left ventricular global systolic function and those with increased left ventricular end-systolic volume; (4) "young" patients (younger than 50 years of age?); (5) older patients (older than 65 to 70 years of age?); (6) patients with non-Q wave AMI; and (7) patients who are receiving thrombolytic therapy. Performance of early cardiac catheterization and angiography in virtually all survivors of AMI, with selective use of appropriate noninvasive tests, may provide a more efficacious means of risk assessment after AMI; if all tests are performed judiciously, the cost of such an approach need not be excessive. A combination of invasive and selected noninvasive tests probably provides optimal information. The risks to the routine performance of diagnostic cardiac catheterization and angiography in all survivors of AMI are: (1) adequate care and attention may not be paid to proper performance of the procedure(s) and to detailed and proper analyses of the data; (2) the need for additional noninvasive testing in selected patients may be ignored; and most importantly, (3) premature or unnecessary revascularization procedures may be performed subsequently. For optimal patient care, the clinician must obtain all necessary data, avoid unnecessary and repetitive tests, know the accuracy of individual tests at his or her own facility, interpret all data in proper context, and then counsel patients objectively about available management strategies. With this approach, all patients who might appropriately benefit from coronary artery revascularization will be correctly identified, and patients who are truly at very low risk (minimal residual coronary artery disease and preserved left ventricular function particularly if associated with a patent infarct-related artery) may be similarly identified and managed appropriately with elimination of unnecessary additional testing and pharmacologic therapy. Finally, whatever approach to risk stratification one chooses for an individual patient, the importance of and the need to correct and/or ameliorate risk factors for coronary artery disease must be recognized and undertaken.

Age Factors↗
PubMed1991

Normalization of Doppler indices of diastolic dysfunction during pacing is a sign of ischemic mitral regurgitation.

Twenty-three patients with angina who were undergoing diagnostic cardiac catheterization underwent cardiac pacing with simultaneous hemodynamic and Doppler echocardiographic evaluation to assess the effects of pacing-induced ischemic on mitral valve velocity. Seventeen patients had significant coronary artery disease, and six patients had normal coronary arteries. Doppler and hemodynamic measurements were performed at rest and immediately after pacing was discontinued to 91% +/- 7% of maximal predicted heart rate. Seven patients experienced new or significant increases in severity of mitral regurgitation after pacing as revealed by Doppler examination. This group had a significant increase (p = 0.007) in early but not in late peak filling velocities immediately after pacing was discontinued, with a resultant decrease in late to early ratios, which decreased from 1.01% +/- 0.12 to 0.70% +/- 0.19 (p = 0.006). Left ventricular end-diastolic pressure increased significantly from 16.7% +/- 6.8 mm Hg to 29.4% +/- 5.3 mm Hg after cardiac pacing (p less than 0.001). Patients with coronary disease who did not develop mitral regurgitation also had significant increases in left ventricular end-diastolic pressure from 18.7% +/- 5.8 mm Hg to 24.3% +/- 8.6 mm Hg (p less than 0.05). There were no changes in late or early wave amplitude, late to early ratio, or other Doppler measurements in any of the other groups. We conclude that mitral regurgitation caused by pacing-induced myocardial ischemia normalizes Doppler indices of mitral inflow, which in turn, may mask persistent or worsened left ventricular diastolic dysfunction.

Adult↗