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Biomedical subjects

D C Sabiston

Publications and source records attributed to D C Sabiston.

At least 19 recordsLinked to original sources
PubMed1979

Effect of increases in afterload before and after coronary occlusion in awake dogs.

Ventricular function curves relating stroke work and left ventricular end-diastolic pressure were generated in awake dogs during increases in preload produced by infusion of fluid and during increases in afterload produced by administration of phenylephrine. The ventricular function curves produced by preloading were steeply upsloping whereas those produced by afterloading were essentially horizontal. Coronary occlusion produced downward displacement of these horizontal curves, but no change in slope. This increases in afterload did not help to demonstrate the functional impairment produced by coronary occlusion.

Animals↗
PubMed1979

The effects of hypothermia on myocardial oxygen consumption and transmural coronary blood flow in the potassium-arrested heart.

Hypothermia remains the primary adjunct employed to lower cellular metabolism during various cardiac procedures. In these experiments, left ventricular myocardial oxygen consumption (MVO2) and transmural blood flow (TBF) were measured during cardiopulmonary bypass with the range of temperatures used clinically. Determinations were made in empty beating normothermic hearts and after potassium cardioplegia at 37, 32, 28, 22, 18, and 15 degrees (K+ = 15--37 meq/L: Hct 25 volumes %). Oxygen content of the total coronary sinus collection was compared with a large volume arterial sample using a Lex-O2-Con-TL analyzer (vs Van Slyke, R = 0.98). Transmural blood flow was measured at each temperature using microspheres (8 microns), and perfusion was maintained at 80 mmHg. Asystole (37 degrees) alone decreased MVO2 from 5.18 +/- 0.55 to 1.85 +/- 0.20 ml O2/min/100 g of left ventricle or approximately 65% (p less than 0.001). With progressive cooling to 15 degrees an additional 82% decrement in oxygen uptake occurred during asystole (p less than 0.001). During asystole at 37 degrees the decrease in MVO2 was reflected mainly by a large decrement (p less than 0.01) in TBF (1.27 +/- 0.19 to 0.74 +/- 0.17 ml/min/g of mean left ventricular flow). However, with cooling below 32 degrees, the arteriovenous oxygen difference narrowed progressively (p less than 0.001) while TBF paradoxically returned to control levels. Endocardial/epicardial flow ratios were not altered by cooling. These data not only confirm earlier reports describing a sequential drop in MVO2 with incremental myocardial cooling, but also establish MVO2 levels for perfused hearts arrested by potassium at lower temperatures (18--15 degrees). Moreover, as transmural blood flow becomes independent of metabolic necessity during hypothermia, coronary autoregulation appears to be impaired, possibly affecting detrimental tissue over perfusion.

Animals↗
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↗
PubMed1978

The use of heparin bonded shunts for perfusion of the renal artery during resection of complex abdominal aortic aneurysms.

During resection of certain complicated aortic abdominal aneurysms, the circulation of the renal artery may require separate perfusion. To achieve this in a simplified manner, a heparin bonded shunt has been used for continuous perfusion of the kidney. This has been used in patients with a horseshoe kidney undergoing aortic aneurysmectomy; for intraoperative perfusion of a previously inserted saphenous vein to renal artery graft for renovascular hypertension and in simultaneous correction of an aortic aneurysm and insertion of a renal artery graft for hypertension. In each situation, the technique worked well with minimal heparinization and excellent results.

Aged↗
PubMed1977

Heparin-coated shunts for lesions of the descending thoracic aorta. Experimental and clinical observations.

Heparin sodium-coated shunts are employed frequently to maintain trunk and lower extremity perfusion during temporary occlusion of the descending thoracic aorta. In the past five years, this shunt has been used in a series of 39 patients ranging in age from 19 to 72 years old, with 34 survivors (87%). The proximal end of the shunt was placed in the subclavian artery in 17 patients, the left ventricle in ten, and in the ascending or transverse aortic arch in 12. The distal end of the shunt was placed either in the lower thoracic aorta or in the femoral artery. For further evaluation of effectiveness, paired observations were made in dogs to determine the physiological consequences with the proximal end of the shunt inserted at two different sites. Although neither shunt decompressed the left ventricle fully, the subclavian-femoral shunt was significantly more effective than was the left ventricle-femoral artery bypass. If a choice exists for sites of insertion of the shunt, it appears that it should be placed distal to the aortic valve, since this position provides the least increase in systolic blood pressure and is associated with a lower demand for myocardial blood flow.

Adult↗