Prevention of ventricular rhythm disturbances in patients with acute myocardial infarction.
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Biomedical subjects
Publications and source records attributed to L Resnekov.
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Twenty-one patients in severe congestive heart failure refractory to conventional medical management were treated with sodium nitroprusside on 22 occasions. On 14 occasions (responders) there was significant improvement in clinical and haemodynamic indices. On 8 occasions (non-responders) hypotension developed without haemodynamic improvement and nitroprusside treatment had to be abandoned. The initial mean arterial pressure and the capillary wedge pressure tended to be higher in the responders while the cardiac index tended to be higher in the non-responders. The systemic vascular resistance was higher in the responders than in the non-responders (2560 +/- 160 vs 1800 +/- 180 dynes s cm-5, P less than 0.001). All of the responders had systemic vascular resistance greater than 1900 dynes s cm-5, while only one of the non-responders had a systemic vascular resistance in this range. Thus, a variable response to vasodilator therapy for congestive cardiac failure is documented. The favourable response appears to be limited to patients with a high systemic vascular resistance.
Fifteen patients with significant coronary artery disease confirmed by cardiac catheterisation were studied before and after aortocoronary artery bypass graft surgery by rest and exercise 201Tl myocardial scintigraphy in an attempt to predict graft status non-invasively. Segmental myocardial perfusion comparisons in pre- and postoperative exercise images allowed correct predictions of high (greater than or equal to 67%) or low (less than or equal to 50%) graft patency rates in 10 of 15 patients, while similar comparisons in postoperative rest and exercise images yielded 13 of 15 correct predictions. Furthermore, 20 of 21 myocardial segments with increased postoperative perfusion when compared with corresponding segments in preoperative exercise studies were supplied by patent grafts. Regional graft occlusion, however, was difficult to predict. It was also difficult to predict graft status when myocardial segments were shown to have unchanged perfusion postoperatively as compared with the preoperative segmental assessment. Despite these limitations, the non-invasive technique of 201Tl imaging can provide useful information regarding coronary artery bypass graft patency.
One hundred consecutive patients undergoing aorta-coronary bypass grafting (ACBG) alone, without ventricular venting, were prospectively studied to determine the incidence and consequence of perioperative myocardial infarction (PMI) and the clinical variables that were predictive of PMI. Incidence was determined by serial electrocardiography (ECG) 100 patients; serum CK, GOT, and LDH (100 patients). CK isoenzymes (qualitative 100 patients, quantitated 50 patients); vectorcardiography (VCG) (78 patients); and 99mtechnetium pyrophosphate scintigraphy (TcPyp) (52 patients). The incidence of PMI by ECG was 9%; an additional 8% of cases was diagnosed by enzymes alone. The incidence of diagnostic change by VCG was 19% and by scintigraphy, 25%. Using at least one changed variable of the remaining three as the reference standard, the relative sensitivity and relative specificity of given variables in the diagnosis of PMI were as follows: ECG 67% and 100%, respectively; VCG 85% and 94%; scintigraphy 92% and 97%; and serum enzymes 86% and 96%. By univariate analysis, unstable angina was the only significant predictor of PMI. The operative mortality rate was 2% and the mortality rate at 12 months was 5%. There was a significantly greater mortality rate in patients with PMI diagnosed by ECG (p less than 0.01), in patients with unstable angina pectoris before operation (p less than 0.05), and in women (p less than 0.05).
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We reviewed current concepts and techniques of cardiac assistance, including orthotopic and heterotopic cardiac allografting. Whereas intraaortic balloon counterpulsation has had the greatest clinical use, other techniques are now becoming available, including the implantable abdominal left ventricular assistance device, and much effort is being expended on the development of artificial hearts and their power sources. Despite the present technical shortcomings, exciting advances have occurred in the clinical management of intractable acute or chronic ventricular failure and cardiogenic shock since the introduction of circulatory assistance in man. The continued development and implementation of these techniques will help reduce the still unacceptably high mortality rate in this group of patients.
To facilitate the radiographic identification of prosthetic heart valves, radiographic silhouettes of various aortic, mitral and tricuspid valve prostheses were analyzed and shematized. Forty different prosthetic valve models (heterograft and mechanical) were obtained from seven domestic manufacturers. Each prosthesis was positioned to approximate the aortic, mitral or tricuspid valve anulus plane. The valves were then radiographed and photographed as they would appear in posteronanterior and left lateral chest radiographs. The radiographic silhouettes were examined and a scheme was designed to enable easy, yet accurate, differentiation of the many heart valve prostheses. Illustrations of the various valve types are presented as they would appear in routine chest radiographs.
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Previous studies of the incidence, natural history, pathogenesis and diagnosis of cardiac rupture are presented, and 20 additional cases described. Progressive cardiorrhexis after myocardial infarction causes death in possibly more than 25,000 persons a year in the United States, and more frequent antemortem diagnosis is needed. Suggestions for future clinical and experimental studies are described and possible means of early diagnosis and therapy are outlined.
Three patients with thyrotoxicosis are described, in whom the presenting symptom was severe cardiac pain at rest or on effort and who were admitted to hospital with suspected or proven myocardial infarction. All patients were studied by selective coronary arteriography and left ventriculography after thyroid function tests which confirmed thyrotoxicosis. There was no demonstrable disease of the major coronary arteries in any of the patients, yet myocardial infarction and left ventricular aneurysm were shown to be present in 1, and there was definite electrocardiographic evidence of ischaemia in all 3. In addition, under stress the myocardium of all 3 patients produced lactate. It is recommended that thyrotoxicosis be seriously considered in the differential diagnosis of cardiac pain, particularly in younger women. The cause of the pain seems related to the cellular effects of thyrotoxicosis on the myocardium and current views of these effects are summarised. Of the 3 patients, 1 died suddenly 6 months after becoming euthyroid, indicating that the disease may not be as benign as expected. A guarded prognosis and continued medical follow-up are recommended when thyrotoxicosis presents with angina pectoris even when normal coronary arteries have been demonstrated.
The concept of continued and progressive coronary care rather than intermediate coronary care is proposed. At each clinical stage the patient may be at risk and his management needs to be planned appropriately--prevention of the development of coronary disease, prehospital care, acute coronary care, subacute coronary care, and late hospital stay. Meticulous continued care once the patient leaves the hospital and returns home may be needed for a long time. Although the benefit of an intermediate coronary care unit has not yet been proved, significant patient risk continues beyond 12 days of hospital admission. High risk patient subsets are emerging requiring careful continued monitoring and the ability to undertake emergency measures as needed, and this is particularly so in patients suffering large anterior infarction, in those with infarction associated with cardiac failure, when infarction is associated with fascicular block and other types of conduction disturbances, and in patients who continue with rhythm disturbances after their admission to the hospital. Electrocardiograph leads III and VI displayed simultaneously should be routinely monitored in patients with fascicular blocks and acute anterior infarction as a guide to instituting prophylactic transvenous pacemaking. The continuation of intensive patient care and monitoring beyond the usual 2 to 5 days in a coronary care unit allows early mobilisation of patients in safety, thus speeding their ultimate rehabilitation. There is, as yet, no satisfactory study documenting the need for intermediate coronary care units, but much presumptive evidence is available to indicate that this is so. A carefully controlled randomised study would be invaluable.
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The diagnostic value of technetium-99m-pyrophosphate (Tc-pyrophosphate) myocardial scintigraphy was determined in 80 consecutive patients who had been admitted to the coronary care unit in order to rule out an acute myocardial infarction. Scintigraphic findings obtained within 5 days of admission were correlated with the final cardiac diagnosis determined for each patient. Significant myocardial uptake of Tc-pyrophosphate (positive scans) occurred in 13 of 22 patients (59%) who had enzyme and/or electrocardiographic proven acute myocardial infarct: 3 out of 5 with transmural myocardial infarct, 9 of 16 with nontransmural myocardial infarct, and 1 patient with left bundle-branch block. Of 58 patients who showed no evidence of acute myocardial infarction, positive scans occurred in 14 of 33 patients who had unstable angina pectoris (42%), 0 of 6 who had congestive heart failure, 6 of 9 who had other acute cardiac syndromes, and in 0 of 10 who had noncardiac chest pain. In the patients with unstable angina pectoris positive scans could not be predicted on the basis of the history, electrocardiographic findings or the arteriographically determined severity of the coronary artery disease. Blood levels of Tc-99m activity measured in 21 cardiac patients and in 6 volunteers did not correlate with the uptake intensity of Tc-pyrophosphate. These findings suggest caution in the use of this imaging method for the diagnosis of acute myocardial infarct in patients admitted with 'rule out myocardial infarction'.
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