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Biomedical subjects

S K Rerych

Publications and source records attributed to S K Rerych.

13 recordsLinked to original sources
PubMed1981

Accuracy of diagnosis of coronary artery disease by radionuclide management of left ventricular function during rest and exercise.

Rest and exercise radionuclide angiocardiographic measurements of left ventricular function were obtained in 496 patients who underwent cardiac catheterization for chest pain. Two hundred forty-eight of these patients also had an exercise treadmill test. An ejection fraction less than 50% was the abnormality of resting left ventricular function that provided the greatest diagnostic information. In patients with normal resting left ventricular function, exercise abnormalities that were optimal for diagnosis of coronary artery disease were an injection fraction at least 6% less than predicted, an increase greater than 20 ml in end-systolic volume and the appearance of an exercise-induced wall motion abnormality. The sensitivity and specificity of the test were lower in patients who were taking propranolol at the time of study and in patients who failed to achieve an adequate exercise end point. In the 387 patients with an optimal study, the test had a sensitivity of 90% and a specificity of 58%. Radionuclide angiocardiography was more sensitive and less specific than the exercise treadmill test. The high degree of sensitivity of the radionuclide test suggests that it is most appropriately applied to patient groups with a high prevalence of disease, including those considered for cardiac catheterization.

Adult↗
PubMed1981

Accuracy of left ventricular end-diastolic dimension determinations obtained by radionuclide angiocardiography.

This study tested the ability of first-pass radionuclide angiocardiography to detect accurately the left ventricular endocardial surface of the intact, conscious, chronically instrumented dog. A spherical phantom was used to define the influence of collimation: with a 1.0-in. collimator, the optimal count threshold was a border at 31% of the image's maximum counts; and with a 1.5-in. collimator, the optimal count threshold was at 21%. These were used to analyze cardioscintigrams obtained in 19 studies of six dogs. The dogs were provided with pulse transit sonomicrometer dimension transducers on the endocardium, right-atrial pacing electrodes, electrocardiographic leads, and catheters in the superior vena cava and right or left atria. The minor-axis dimension of the left ventricle was measured ultrasonically while the cardioscintigram was being stored. The minor-axis dimension and end-diastolic volume obtained by the two techniques had linear correlation coefficients of 0.95 and 0.98. This correlation indicates the inherent accuracy of radionuclide techniques by defining left-ventricular endocardial edges for a large range of volumes in the dog.

Angiocardiography↗
PubMed1980

Quantitative radionuclide angiocardiography.

This study introduces a new method for calculating actual left ventricular volumes and cardiac output from data recorded during a single transit of a radionuclide bolus through the heart, and describes in detail current radionuclide angiocardiography methodology. A group of 64 healthy adults with a wide age range were studied to define the normal range of hemodynamic parameters determined by the technique. The normal radionuclide cardiac index averaged 3.25 +/- 0.75 liters/min/m2, the end-diastolic volume index was 62 +/- 16 ml/m2, the stroke volume index was 40 +/- 9 ml/m2, and the ejection fraction was 0.66 +/- 0.07. Radionuclide angiocardiograms were performed in patients undergoing cardiac catheterization to validate the measurements. In 33 patients studied by both techniques on the same day, a close correlation was documented for measurement of ejection fraction (r = 0.89) and end-diastolic volume (r = 0.89). Determination of the linear regression equation for the end-diastolic volumes obtained by the two methods (EDVcath = 1.26 x EDVRN - 7.56) permitted correction of end-diastolic volume and provided an approach for calculation of stroke volume and cardiac output. To validate the method of volumetric cardiac output calculation, 33 simultaneous radionuclide and indocyanine green dye determinations of cardiac output were performed in 18 normal young adults and correlated closely over a range of 4-17 liters/min (r = 0.94). These independent comparisons of radionuclide measurements with two separate methods document that initial transit radionuclide angiocardiography accurately assesses left ventricular function.

Adolescent↗
PubMed1980

Detecting abnormalities in left ventricular function during exercise before angina and ST-segment depression.

To determine if abnormalities in left ventricular function precede angina pectoris and electrocardiographic evidence of myocardial ischemia, we used radionuclide angiocardiography to measure left ventricular ejection fraction, volumes, cardiac output and wall motion in 10 normal subjects and 25 patients with coronary artery disease at rest and during two levels of upright bicylce exercise. In the patients with coronary artery disease, the first radionuclide study during exercise was performed before and the second after the onset of ST-segment depression. In all normal subjects, the ejection fraction increased more than 5%, the end-diastolic volume increased less than 25% and the end-systolic volume decreased from rest to both levels of exercise. Wall motion was normal at rest and increased with exercise. No patient with coronary artery disease had chest pain or ST-segment depression during the first level of exercise. The ejection fraction either decreased or increased less than 5% in 18 patients, the end-diastolic volume increased more than 25% in nine, the end-systolic volume increased in 19 and a segmental contraction abnormality developed in 14. Hemodynamic and wall motion abnormalities occurred in all patients during the second level of exercise when ST-segment depression was present. During exercise in patients with coronary artery disease, abnormalities in left ventricular function frequently develop before angina pectoris and electrocardiographic evidence of myocardial ischemia.

Adult↗
PubMed1980

Noninvasive assessment of the effects of aorta-coronary bypass grafting on ventricular function during rest and exercise.

Ventricular function was measured by radionuclide angiocardiography during rest and exercise in patients before and approximately 4 months after aorta-coronary bypass grafting. The first group of seven patients continued to have symptomatic chest pain after operation. The second group of 13 patients were asymptomatic after operation but, since they had been studied before operation, consented to postoperative study. Before operation, both patient groups demonstrated similar degrees of myocardial ischemia during exercise as documented by a decrease in ejection fraction, by large increases in end-diastolic and end-systolic volumes, and by exercise-induced wall motion abnormalities. After aorta-coronary bypass grafting, ventricular function in the symptomatic patients was unchanged during rest and exercise. In contrast, ventricular function during rest and exercise in the asymptomatic patients was markedly improved. With exercise, the ejection fraction increased and the exercise-induced wall motion abnormalities seen before operation were abolished. Therefore, aorta-coronary bypass grafting can effectively reverse exercise-induced left ventricular dysfunction in patients with coronary disease. Moreover, the change in left ventricular function demonstrated by radionuclide angiocardiography correlated with the clinical status of the patient groups.

Cardiac Output↗
PubMed1979

Noninvasive assessment of hemodynamic effects of mitral valve commissurotomy during rest and exercise in patients with mitral stenosis.

Noninvasive radionuclide angiocardiography (RNA) provides simple and accurate assessment of parameters of cardiac function during rest and during maximal exercise. Left ventricular function was assessed by RNA in nine patients with isolated mitral stenosis before and approximately 6 months after mitral commissurotomy. Before operation, the mean mitral valve gradient was 14.0 +/- 2.8 mm Hg, and the mean mitral valve area was 1.20 +/- 0.3 cm2. Each patient was evaluated at rest and during maximal exercise on an isokinetic bicycle ergometer before and after commissurotomy. Heart rate, ejection fraction, end-diastolic volume, stroke volume, pulmonary transit time, cardiac output, and diastolic ventricular filling rate were determined by the radionuclide technique. Before operation, patients with mitral stenosis had characteristic changes from rest to exercise which supported restriction to diastolic ventricular filling as the primary limitation in generating a cardiac output during exercise. The stroke volume was unchanged from rest to exercise. Thus the cardiac output during exercise was heart rate dependent. However, after commissurotomy the stroke volume increased from rest to exercise. Therefore, cardiac output during exercise was achieved by heart rate and an augmented stroke volume. Moreover, the pulmonary transit time was reduced during rest and exercise after operation. The maximum ventricular ejection and filling rates were markedly increased during rest and exercise after commissurotomy. These differences in hemodynamic parameters at rest and during exercise document the mechanics of increased exercise tolerance in patients with mitral stenosis after mitral commissurotomy.

Adult↗
PubMed1979

Noninvasive radionuclide assessment of cardiac function in patients with peripheral vascular disease.

Disorders of the peripheral vascular system often are associated with heart disease which may increase operative risk. The purpose of this study was to investigate the clinical usefulness of radionuclide angiocardiography for evaluation of cardiac function in patients with vascular disorders. This simple procedure provides measurements of cardiac output, pulmonary blood volume, and left ventricular end-diastolic volume, stroke volume, and ejection fraction with no significant risk or discomfort to the patient. A total of 22 patients with vascular disorders were studied by this technique. Five patients had systemic arteriovenous malformations. The cardiac output, end-diastolic volume, and stroke volume were documented to be greater than normal in these patients before operation. In three patients studied following closure of the arteriovenous fistula, the cardiac output, left ventricular end-diastolic volume, and stroke volume decreased. Postoperative changes in left ventricular ejection fraction were variable. A group of 17 patients with atherosclerotic vascular disease underwent cardiac evaluation. In nine patients with no history of cardiac disease, the lowest ejection fraction of 0.45 occurred in a patient with a saccular thoracic aneurysm, the only patient of the 22 who died after operation. A wide variation in ejection fraction was observed in patients with a history of cardiac disease which ranged from 0.32 to 0.86. Objective documentation of cardiac function by radionuclide angiocardiography would appear to enhance the management of patients with peripheral vascular disorders.

Adult↗
PubMed1978

Cardiac function at rest and during exercise in normals and in patients with coronary heart disease: evaluation by radionuclide angiocardiography.

This study demonstrates that radionuclide angiocardiography provides a simple and noninvasive approach for evaluation of myocardial function. Previous work concerning myocardial performance has been generally conducted with the patient in the supine position. Radionuclide angiocardiograms were performed in the present study at rest and during exercise in 30 normal subjects and in 30 patients with ischemic coronary artery disease. There were 30 normal controls (Group I), ten with single coronary artery disease (Group II), and 20 patients with multiple vessel coronary disease (Group III). All subjects were studied in the erect posture on a bicycle ergometer. In the normal controls, the mean heart rate doubled and the cardiac output tripled during exercise. Intensive training can lead to extraordinary levels of cardiac performance as shown in a world-class athlete who during peak exercise attained a heart rate of 210, an ejection fraction of 97%, and a cardiac output of 56 litres per minute. In the patients with coronary artery disease, both groups, were able to increase cardiac output to approximately twice the resting value. The magnitude of increase in blood pressure during exercise was not significantly different in the three groups. However, definite changes were present in the end-diastolic volume at rest was 116 and rose to 128 ml in Group I, 93 rising to 132 ml in Group II, and 138 increasing to 216 ml in Group III. The stroke volume increased comparably in all three groups, but the ejection fraction from rest to exercise showed a marked contrast in the controls compared to those with multivessel coronary disease. The ejection fraction rose in Group I from 66 to 80% during exercise, while in Group II it fell from 69 to 67%, and in Group III from 60 to 46%. These findings indicate that patients with ischemic myocardial disease respond to the stress of exercise by cardiac dilatation to maintain of increase stroke volume at increased heart rates. Moreover, the magnitude of this response appears to be greatest in patients with left main coronary artery stenosis. This approach for evaluating myocardial function during exercise provides useful data of importance in selecting medical versus surgical management of patients with ischemic coronary artery disease.

Adult↗