Myocardial cell damage during vasospastic anginal attacks with promptly reversible electrocardiographs changes

Influence of repetitive coronary occlusions on myocardial adenine nucleosides, high energy phosphates and ultrastructure

We compared the effects of repeated short periods of myocardial ischemia with those of permanent occlusion (canine open-chest) with regard to tissue content of adenine nucleotides, nucleosides, creatine phosphate, and ultrastructure. Coronary occlusion for 3 min followed by a reperfusion period of 7 min was repeated up to a cumulative occlusion time of either 45 or 90 min. After cumulative occlusions of 15, 30, 45, and 90 min, transmural needle biopsies were taken from the ischemic area to be analyzed for adenine nucleotides, nucleosides, creatine phosphate, and ultrastructural changes. At the end of each experiment, tetrazolium salt staining was used for macroscopic detection of myocardial necrosis. These data were obtained with those obtained from dogs with a permanent coronary occlusion of 45 and 90 min, respectively. After repeated coronary occlusions at a cumulative occlusion time of 45 min, macroscopic detection of necrosis was negative, and after 90 min of cumulative coronary occlusion, patchy subendocardial tissue necrosis was found in only one out of 13 dogs, whereas in the group with permanent coronary occlusion, small patchy subendocardial necrosis was found in 95% after 45 min, and after 90 min permanent coronary occlusion, large subendocardial necrotic areas spreading towards the epicardial layers were found in 90% of the hearts. Ultrastructural investigations showed only slight to moderate ischemic injury after 45 and 90 min intermittent coronary occlusion, whereas permanent coronary occlusion produced moderate to severe ischemic injury after 45 min; and 90 min permanent coronary occlusion produced irreversible ischemic injury in all subendocardial tissue samples and in 80% of the subepicardial tissue samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical aspects of silent myocardial ischemia in patients with angina and other forms of coronary heart disease

Silent myocardial ischemia is defined as objective evidence of myocardial ischemia occurring in the absence of symptoms in a patient who has either coronary artery disease or spasm. The largest number of patients with silent myocardial ischemia identified to date are those with effort angina, in whom silent episodes are at least three to four times as frequent as painful episodes. Since episodes of silent myocardial ischemia are not alarming to the patient and are likely to escape detection, their clinical importance must reside in their association with morbid events of ischemic heart disease. In fact, silent myocardial ischemia can result in silent myocardial infarction, sudden death, or other events. The detection of these episodes has the potential to provide clinicians with a more complete understanding of all the ischemic processes occurring in patients with angina or other forms of coronary disease. Silent myocardial ischemia can be detected by a variety of methods. Transient ischemic-type electrocardiographic abnormalities that occur without symptoms and that have been recorded during exercise testing or by means of ambulatory, coronary care unit, or telemetry monitoring may be used to document silent myocardial ischemia. Reversible left ventricular wall motion abnormalities without symptoms, observed at rest or during exercise radionuclide angiography, 2-D echocardiography, or contrast angiography, may also be used to document silent myocardial ischemia. However, only ambulatory electrocardiographic monitoring provides long-term evaluation that documents repeated episodes of silent myocardial ischemia outside of the laboratory. Controlled studies, directed specifically at preventing silent myocardial ischemia and/or its consequences in patients with angina, are limited. It has been determined, however, that both hourly administration of sublingual nitroglycerin and intravenous administration of isosorbide dinitrate are effective. Other studies examining the effects of beta blockers (propranolol, atenolol, and labetalol) in the treatment of angina have shown that their use also results in a reduced frequency of silent episodes, but that a large number of episodes persist. It has been observed that verapamil alone and nifedipine, either alone or in combination with a beta blocker, appear to significantly decrease silent myocardial ischemia in patients with angina. A major limitation of these studies is that treatment was not specifically titrated to reduce or eliminate silent myocardial ischemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Intermittent brief periods of ischemia have a cumulative effect and may cause myocardial necrosis

We investigated the effects of brief intermittent periods of ischemia on myocardial viability. Brief periodic coronary occlusions were produced up to 18 times by inflating and deflating the balloon of an intracoronary No. 2F catheter for periods of 15, 10 or 5 minutes, followed by 15-minute periods of reperfusion. Creatine kinase (CK) release, triphenyl tetrazolium chloride staining, and light and electron microscopy were used to detect the presence of myocardial necrosis. For the study of CK release, blood was taken from the great cardiac vein and the aorta before and at 5-minute intervals during each left anterior descending coronary occlusion, as well as during and 1, 5, 10 and 15 minutes after balloon deflation. In seven of 24 dogs with 15-minute occlusions, in five of 21 dogs with 10-minute occlusions, and in three of 32 dogs with 5-minute occlusions, small but distinct areas of subendocardial necrosis were present. In all dogs with morphologic proof of necrosis, there was periodic release of CK into the great cardiac vein, which peaked immediately after reperfusion, reflecting CK washout. Thus, brief periods of ischemia, which when single do not cause necrosis, have a cumulative effect and may cause myocardial necrosis. This mechanism of necrosis may be relevant clinically in patients with frequent anginal episodes. Since many dogs of this study did not have any myocardial necrosis, the findings also suggest that intermittent reperfusion has a beneficial effect and may prevent necrosis, even when total occlusion time exceeds 200 minutes.

Spontaneous angina in the coronary care unit. 1. Frequent association with development of acute myocardial infarction

We studied 16 patients, 36 to 75 years old, with repetitive episodes of spontaneous angina (SA) associated with transient ST-segment shifts. At onset SA was not associated with changes in systolic blood pressure, heart rate, or double product, but such increases often occurred late. All patients smoked cigarettes; 13 were hypertensive. History of angina at rest or exertion was present in 13 patients, seven of whom had crescendo chest pain before admission. Twelve patients had an acute myocardial infarction (MI). Complications were not uncommon in the setting of MI. Angina persisted in a few patients after MI, and resulted in its extension in three patients. Coronary arteriography performed on eight patients revealed significant coronary artery disease in seven. There was a good correlation between the loci of coronary lesions and the transient ECG changes. Nitrates were occasionally ineffective in relieving symptoms and failed to prevent SA. High doses of propranolol were also ineffective. Aortocoronary bypass surgery was performed on three patients. Fifteen patients were discharged asymptomatic. One patient died in the hospital. Three additional patients died within the first month after admission. Followup in the clinic revealed good response to nitrates in the 12 surviving patients. SA in the CCU may be a good model to study the pathogenesis of myocardial ischemia and acute MI.