摘要:

SUMMARY The widespread popularization of stress testing and the extensive application of its results in a variety of clinical settings make it imperative that a better method than the presently used simplistic "positive" or "negative" interpretation be devised. As a step toward a comprehensive diagnostic and prognostic index based on stress tests, a simple grading system of electrocardiographic changes, together with recognition of clinical modifiers, is suggested.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY Because the mechanism of adverse reactions to abrupt withdrawal of propranolol in patients with coronary disease is an enigma, we studied the effect of cessation of propranolol on beta receptor reactivity to catecholamine stimulation. Heart rate and maximum rate of rise of left ventricular pressure (dP/dt max) during isoproterenol infusions and plasma free fatty acids (FFAs) after epinephrine infusions were measured in six conscious dogs before, during and after four weeks of oral propranolol (40 mg p.o. q8h). Rises in heart rate, dP/dt max and FFAs were blocked during propranolol administration. Twenty-four hours after withdrawal from propranolol, heart rate and dP/dt max responses remained significantly attenuated, although FFA responses were at premedication levels. The 72-hour, 96-hour and one week postmedication responses did not differ from premedication values. Thus, partial beta blockade of the heart was still present at 24 hours and no evidence of heightened beta receptor sensitivity was detected on repeated study one week after withdrawal from a long-term, high dose propranolol regimen.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY Eleven patients with anterior myocardial infarction less than six hours old underwent intraaortic balloon pumping (IABP) in an attempt to control injury. Direct hemodynamic measurements excluded shock. Response to therapy was judged individually by comparison to a one-hour pretreatment period. There was no parallel control group.Five patients responded with an 84% fall in ST elevation in one hour, with preservation of precordial R waves and good ventricular function. In contrast, six patients responded poorly, with a 40% fall in ST elevation in one hour, Q wave development and poorer residual left ventricular function.Coronary angiography demonstrated a significant correlation between response and presence or absence of complete left anterior descending coronary artery occlusion. Early use of IABP in anterior myocardial infarction may interrupt injury, though in this series only in cases with residual left anterior descending patency.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY To determine the effect of ischemia on myocardial clearance of thallium-201 (201TI), we studied 12 dogs with ischemia produced after the injection of Tl. TI was given I.V. 10 minutes before left anterior descending (LAD) coronary artery ligation. 85Sr-microspheres (MS) were administered 5 minutes later, and control biopsies were obtained from the myocardium. The LAD was tied and repeat biopsies obtained from the ischemic zone (IZ) and normal zone (NZ) 15 minutes and 2 hours later. 46Sc-MS were given just before the final biopsy. Tl activity in the IZ was not significantly different from that in the NZ either before LAD occlusion or 15 minutes and 2 hours later. TI clearance at the end of 2 hours was not significantly different (27 ± 5% vs 28 ± 5%, IZ vs NZ respectively) between the two zones. The half-time of TI clearance from both the IZ and NZ was calculated at 4.5 hours (consistent with previously reported normal values). This occurred despite a decrease in regional myocardial blood flow to 24 ± 6% of control (P < 0.01) in the IZ and an increase to 147 ± 14% of control (P < 0.01) in the NZ during the study. We conclude that myocardial ischemia does not alter the normal rate of TI clearance from the myocardium.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY The administration of hyaluronidase is a promising intervention to protect the ischemic myocardium in man, but evidence of the extent to which it may reduce the ultimate size of an infarct is not well-defined. Hence, open chest, anesthetized dogs were randomized into 10 control dogs which received saline and eight treated dogs which received three doses of hyaluronidase (500 NF units/kg I.V.) at 15 minutes, 2 hours and 24 hours after occlusion of the left anterior descending coronary artery (CAO). Regional myocardial blood flow (RMBF) assessed by the microsphere technique was measured 12 minutes after CAO. The chest was then closed and the dogs were allowed to recover. Twenty-one days after CAO, the hearts were excised, divided into I cm thick slices and incubated in triphenyl tetrazolium chloride. Infarct size was then determined by planimetry. The left ventricular myocardium was divided into multiple samples for RMBF analysis. In control dogs 23.2 ± 2% of the left ventricle was infarcted, compared to only 9 i 2.8% (P < 0.001) in hyaluronidase-treated dogs. RMBF in noninfarcted myocardium directly adjacent to the infarct was similar to that in the normal zone remote from the infarct in the control dogs; however, in the hyaluronidase-treated dogs, blood flow in the myocardium adjacent to the infarct was significantly reduced to 68% of normal (P < 0.01) in the outer myocardial wall and to 86% of normal (P < 0.02) in the inner myocardial wall, which indicates that this tissue, at least in some part, was in jeopardy, but was salvaged by hyaluronidase.Epicardial electrocardiographic data showed that three weeks after CAO, Q waves were less frequent and smaller in hyaluronidase compared to untreated dogs. Preservation of the frequency and magnitude of R waves was greater in the hyaluronidase-treated group at three weeks. We conclude that hyaluronidase resulted in long-term preservation of the ischemic myocardium.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY Radionuclide techniques for sizing acute myocardial infarction have been hampered by the intrinsic limitations of the scintillation camera. Emission computed tomography can overcome these limitations. Single photon emission computed tomograms of the distribution of technetium-99m pyrophosphate in acute anterior and posterior infarcts were obtained in 16 dogs after death. Tomograms were also obtained in 10 dogs during life without gating. The size of the infarcts was determined by staining gross sections of the heart with nitro blue tetrazolium, dissecting out the infarcted tissue and weighing it. Infarct sizes were determined from the tomographic images and compared with the measured infarct sizes. Good images showing the location and three-dimensional extent of the infarcts were obtained in all dogs. The measured and calculated infarct sizes correlated well (r = 0.85). Comparison of the calculated sizes in the living (non-gated) and dead ("physiologically" gated) animals showed reasonable agreement (r = 0.87). Single photon emission computed tomography is a feasible and useful technique for localizing and sizing acute myocardial infarctions.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY Even though ventricular fibrillation is used frequently during cardiopulmonary bypass (CPB), the effects of fibrillation on myocardial regions supplied by collateral vessels have not been determined. To study these effects, nine dogs with left ventricles (ameroid model) consisting of a region of myocardium supplied by collateral vessels (CR) and a region supplied by normal coronary arteries (NR) were subjected to normothermic CPB at two perfusion pressures. In both the empty beating heart (EBH) and empty fibrillating heart (EFH) regional myocardial flow was determined by tracer microspheres. Retrograde coronary pressure was measured via cannulation of the circumflex artery distal to the ameroid induced occlusion. When perfusion pressure was maintained at 80 mm Hg, retrograde coronary pressure was similar in the EBH (46 ± 4 mm Hg) and in the EFH (48 ± 3 mm Hg). During fibrillation subendocardial flow in the CR was unchanged, while flow in the NR increased (P < 0.02). In addition, the endo/epi was greater in the NR than in the CR (P < 0.01), a difference which did not exist in the EBH. The flow response to fibrillation in the CR could be produced in the NR by reducing the perfusion pressure to 50 mm Hg. These data suggest that during CPB, fibrillation exaggerates existing subendocardial perfusion deficits in collateral regions and the impaired flow response appears to be related to a low regional intravascular pressure.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID

摘要:

SUMMARY To assess the effects of moderate potassium cardioplegia (37 mEq/l KCI) on the severity of myocardial ischemia during arrest and on post arrest ventricular function, 32 isolated, isovolumic feline hearts were studied before, during and I hour after ischemic arrest. Normothermia (37°C) was maintained in 16 hearts, eight without KCI and eight with KCI. Hypothermia (27°C) was maintained in the remaining 16 hearts, eight with KCI and eight without KCI. Myocardial oxygen (PmO,) and carbon dioxide tensions (PmCO,) were measured by mass spectrometry. Maximum developed intraventricular pressure (max DP) and max dP/dt were used as indices of performance. Compared with normothermic or hypothermic arrest alone, the addition of potassium cardioplegia resulted in a significant reduction in the peak PmCO2 measured during the arrest period. Hypothermia alone resulted in morphologic evidence of improved myocardial preservation and a significant reduction in peak PmCO, compared with normothermia. Post arrest ventricular function was best with the combination of hypothermic arrest and potassium cardioplegia (max DP = 96 ± 6% of control and max dP/dt = 99 ± 5% of control). These data suggest that the beneficial effects of potassium cardioplegia and 27° hypothermia are additive, and that reduction in myocardial ischemia as evidenced by a reduction in peak PmCO, correlated with improvement in ventricular performance in the post arrest period and with preservation of myocardial structure.

ISSN:0009-7322    

出版商:OVID    

年代:1978

数据来源: OVID