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Biomedical subjects

D C Sabiston

Publications and source records attributed to D C Sabiston.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1977

Surgical management of chronic pulmonary embolism.

The clinical course of most patients with pulmonary embolism is one of gradual resolution with re-establishment of flow in the pulmonary arteries. In a small but definite group of patients, the emboli do not resolve and a state of chronic pulmonary embolism ensues. The primary thrombotic process in the systemic venous system may persist, and in some instances may be unrecognized. Such patients experience recurrent showers of emboli which may ultimately occlude a large part of the pulmonary arterial circulation with development of severe respiratory insufficiency. Six patients with this syndrome are described, and in each there was a history of dyspnea, cyanoiss, and exercise intolerance associated with a low arterial PO2, right ventricular hypertrophy, and pulmonary hypertension. Pulmonary scans and arteriograms demonstrated that more than half of the major pulmonary arteries were occluded and, in addition, smaller vessels were also obstructed. Pulmonary embolectomy was performed in each patient. Five of the 6 obtained a highly gratifying response, including relief of the dyspnea and cyanosis, an increase in arterial PO2, and a decrease in pulmonary arterial pressure. In each of the five in whom improvement occurred, the back-bleeding from the pulmonary artery at the time of embolectomy was quite good. In the sixth patient, the back-bleeding was very poor, and despite embolectomy, the vessel thrombosed postoperatively with no improvement in the patient's clinical course. Follow-up studies in these patients range up to 8 years with demonstration of continued patency of the pulmonary arteries as well as continued improvement in clinical symptoms and in the arterial PO2.

Adult↗
PubMed1977

The relationship of patient selection to prognosis following aortocoronary bypass.

Operative mortality for the first 787 patients who underwent aortocoronary bypass at Duke University Medical Center was 9.7%. Within 699 patients who underwent elective bypass only, operative mortality was 8.8% before January 1, 1972, and 5.4% subsequently. This apparent variation in operative mortality over time was largely a consequence of changing patterns of patient selection, i.e., a two- to three-fold decrease in the prevalence of ventricular dysfunction. Since January 1, 1972, operative mortality for 444 patients with mild or no heart failure who underwent elective bypass only was 5.0%. The 55 patients with left main disease had 12.7% operative mortality. In the 192 patients without left main disease who had one- or two-vessel disease, operative mortality was 1.0%, whereas, 197 patients with three-vessel disease had a 6.6% operative mortality. The 103 patients with three-vessel disease less than 50 years of age underwent operation with a 2.9% mortality. Although these results demonstrate that selected patients may undergo operation with a mortality approaching 1%, it is not clear that only such low risk patients should be offered surgery. Accurate estimates of benefits and risks of aortocoronary bypass surgery are necessary in the management of specific patients.

Cardiac Catheterization↗
PubMed1976

Pulmonary embolism.

Pulmonary embolism is a common and often fatal postoperative complication. Dyspnea is the most common clinical manifestation in pulmonary embolism, and other signs are frequently inconsistent and often vague. The chest film and electrocardiogram may be helpful in excluding other cardiorespiratory diseases but they are frequently unreliable in establishing an objective diagnosis of pulmonary embolism. Documentation of a decreased arterial saturation provides suggestive evidence of pulmonary embolism. Lung scanning is a safe, sensitive procedure for the initial evaluation of symtoms suggestive of pulmonary embolism, and pulmonary arteriography may be necessary to confirm the diagnosis in certain patients. Anticoagulation is effective in the prevention and treatment of pulmonary embolism and proves successful in the vast majority of patients. Emboli that are not fatal gradually resolve in the pulmonary circulation. Vena caval interruption is occasionally beneficial in selected patients, especially those with septic emboli and cor pulmonale, but should only be performed when the indications are quite clear. Under certain selected circumstances pulmonary embolectomy may be indicated. Patients with massive embolism occluding more than one-half of the pulmonary arterial system and prooducing a markedly elevated pulmonary arterial pressure and severe hypoxemia may die in acute right heart failure. Intractable shock unresponsive to aggressive medical therapy in these patients represents an indication for pulmonary embolectomy. The hazards of these surgical procedures demand that a definite diagnosis of pulmonary embolism be made and a systematic approach to the diagnosis and treatment should be followed in all patients with the disorder.

Adult↗
PubMed1976

The diagnosis of pulmonary embolism.

Objective documentation of pulmonary embolism is an essential prerequisite for appropriate treatment (Figure 7). A chest film, as well as measurement of arterial blood gases, should be obtained immediately, and if the lung fields are essentially normal, a lung scan should then be performed. If the scan shows a definite perfusion defect characteristic of embolism, this provides sufficient evidence to establish a diagnosis of pulmonary embolism. The presence of hypoxemia with a low arterial pO2, further confirms the suspicion of a ventilation-perfusion abnormality, and anticoagulant therapy with heparin should be initiated immediately. Should the chest film show abnormalities in the same anatomic areas in which perfusion defects are present on the scan, further investigation by pulmonary arteriography is required to substantiate the diagnosis. The use of pulmonary angiography for documentation of pulmonary embolism is also indicated at the outset when certain specific disorders that confuse scan interpretation are also present-chronic obstructive lung disease, emphysema, asthma, congestive cardiac failure. Assessment of the arterial blood oxygenation simultaneously with the estimated occlusion and the hemodynamic data can be used as a prognostic index as therapy progresses.

Blood Gas Analysis↗
PubMed1976

Coronary collateral circulation during stress and the effects of aorta-coronary bypass grafts.

The ability of coronary collateral vessels to supply an adequate volume of blood to the subendocardium during the resting state and during periods of stress was studied. Regional myocardial blood flow was determined by the radioactive microsphere technique. Ameroid constricting devices were placed around the left circumflex coronary artery in 22 adult mongrel dogs. Three months later, regional myocardial blood flow was measured in a normal area of the left ventricle as well as in the area supplied entirely by coronary collateral vessels. Collateral blood flow was sufficient in the resting state to prevent myocardial ischemia distal to a gradually occluded coronary artery. However, in 10 animals (Group I) without aorta-coronary bypass grafts (ACBG), a selective underperfusion of the collateralized subendocardium occurred during periods of stress. In 12 animals (Group II), this selective underperfusion of the collateralized subendocardium with stress was abolished by placing ACBG's distal to the site of the coronary artery occlusion.

Animals↗
PubMed1976

The effect of positive end-expiratory pressure on regional ventilation and perfusion in the normal and injured primate lung.

Although positive end-expiratory pressure (PEEP) is being employed in the management of respiratory insufficiency, many of its physiological effects remain undetermined. The cardiopulmonary effects of PEEP as well as its effect on regional ventilation and perfusion were studied in 10 baboons before and after pulmonary injury with oleic acid. In the normal lung, there was significant improvement in oxygenation at a PEEP of 5 cm. of water secondary to improved ventilation and perfusion in all PEEP greater than 5 cm. of water produced increasing mismatch of ventilation and perfusion in all zones. After oleic acid was injected, hypoxemia was evident with a reversal of the normal ventilation-perfusion (V/Q) relationship between upper and lower lung zones. This mismatch of ventilation and perfusion was corrected at a PEEP of 15 cm. of water. It was reasonable to conclude that the use of PEEP in the injured lung exerts it beneficial effect by balancing regional ventilation and perfusion in addition to increasing functional residual capacity.

Animals↗