Unstable angina pectoris. Natural history, hemodynamics, uncertainties of treatment and the ethics of clinical study

Morphologic correlate of pathologic Q waves as assessed by gradient-echo magnetic resonance imaging

To assess the morphologic correlate of the presence and absence of pathologic Q waves in the electrocardiogram, 30 patients with and 17 patients without pathologic Q waves and chronic myocardial infarction (infarct age > 4 months) and 15 patients without previous myocardial infarction but significant coronary artery disease (> 70% diameter stenoses) were studied by gradient-echo magnetic resonance imaging (MRI). Short-axis MRI tomograms were evaluated on a segmental basis by calculating end-diastolic wall thickness and systolic wall thickening. All segments were graded transmural scar (end-diastolic wall thickness < end-diastolic wall thickness of a healthy control group [n = 21]-2.5 SD and lack of systolic wall thickening), hypokinetic (end-diastolic wall thickness > or = end-diastolic wall thickness of the control group-2.5 SD and systolic wall thickening < or = 2 mm), or normal (end-diastolic wall thickness > or = end-diastolic wall thickness of the control group-2.5 SD and systolic wall thickening > 2 mm) by MRI criteria. Myocardial infarcts were defined as transmural if at least 1 segment fulfilled the MRI criteria for transmural scar. Of 30 patients with Q-wave infarction, 26 (87%) had a transmural defect, and 6 of 17 patients (35%) with non-Q-wave infarction had a transmural infarct. Segmental evaluation yielded 129 of 480 scar segments (27%) for patients with Q-wave infarction, 20 of 272 scar segments (7%) for patients with non-Q-wave infarction, and no scar segments for patients without previous myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Dipyridamole perfusion scintigraphy: the experience with its application in one hundred seventy patients with known or suspected unstable angina

We evaluated the safety, accuracy, and potential clinical utility of intravenous dipyridamole perfusion scintigraphy with thallium-201 in 170 patients, 78 with suspected and 92 with known unstable angina. All had coronary angiography. Noncardiac side effects (26%), induced chest discomfort (44%), and ST segment changes (12%) were similar in the two groups. No significant arrhythmias occurred. Two patients had prolonged chest pain, both with extensive reversible image abnormalities and associated creatinine kinase-MB release. Both had elective bypass surgery. Twenty-eight patients had normal coronary arteries, and 35 had single-vessel disease. Scintigraphic per patient sensitivity and specificity were 91% and 79% with a per vessel sensitivity of 74% and a per vessel specificity of 78% without between-group differences. During a brief follow-up period, 62 patients with image abnormalities had coronary revascularization, and there were seven deaths without intergroup differences. In a similar patient group that did not have angiography, scintigraphic defects were less frequent and less extensive, revascularization was not performed, and subsequent deaths occurred less often. Dipyridamole perfusion scintigraphy is an accurate alternative to exercise testing in the evaluation of patients with unstable angina pectoris. Although not without risk, the method appears relatively safe and should be considered as a guide to diagnosis, and probably to prognosis and management.

Initial ECG in Q wave and non-Q wave myocardial infarction

The initial ECGs in 440 patients admitted for suspected acute myocardial infarction were retrospectively analyzed to determine predictive values of these ECGs for acute myocardial infarction and to determine differences in the initial ECG for Q wave and non-Q wave myocardial infarction. One hundred (23%) of the study patients were diagnosed as having an acute myocardial infarction. Acute injury was seen in 47% of these patients (positive predictive value [PPV], 84%; 95% confidence interval [CI], 72% to 92%), ischemia in 15% (PPV, 39%; 95% CI, 24% to 57%), and left ventricular hypertrophy with strain in 11% (PPV, 19%; 95% CI, 4% to 29%). Forty-three patients were diagnosed as having a Q wave infarction and 50 patients as having a non-Q wave infarction. Seventy-two percent of the patients with a Q wave infarction had acute injury as the initial ECG interpretation compared with 38% in the non-Q wave infarction group (P less than .001). In contrast, only 17% of patients with Q wave infarction had an initial ECG interpretation of ischemia or strain as compared with 36% of patients with non-Q wave infarction (P = .03). Because of the relatively high incidence of acute myocardial infarction in patients admitted with an initial ECG interpretation of ischemia or left ventricular hypertrophy with strain, prospective studies must be performed to determine if selective patients with acute ST segment depression or ischemic T wave inversion in the setting of suspected acute myocardial infarction may benefit from early thrombolytic therapy.

The ECG in acute myocardial infarction

The initial ECG is the most rapid and readily available tool in the emergency department for the evaluation of patients presenting with suspected myocardial infarction. However, studies have shown that the initial ECG is diagnostic of acute myocardial infarction in only a minority of patients. This paper discusses the importance of the initial ECG and other information in aiding the disposition of patients with suspected myocardial infarction. Classic electrocardiographic descriptions are discussed as well as the newer terminology of Q wave versus non-Q wave infarction and ST segment versus T wave infarction. A brief review is made of the electrophysiology of the ECG changes seen in myocardial infarction. Finally, clinical studies are presented that establish a definite role for the use of the initial ECG.

The haemodynamic significance of asymptomatic ST segment depression assessed by ambulatory pulmonary artery pressure monitoring

A transducer-tipped catheter with simultaneous frequency modulated electrocardiograms and a miniaturised tape recorder was used to record ambulatory pulmonary artery pressure for 24-48 hours in 19 men (mean age 57.7) with clinical and angiographic evidence of coronary artery disease. Sixty seven episodes of ST segment depression (greater than 1 mm) were recorded. Thirty five were accompanied by pain of which six occurred at night; in 34 pulmonary artery diastolic pressure rose significantly. In all but two of the 32 episodes of painless ST segment depression (four of which were at night) there was a significant rise in pulmonary artery diastolic pressure. No such rise was found in six normal subjects during exertion. ST segment changes tended to occur before (24 episodes) or at the same time (27 episodes) as changes in pulmonary artery diastolic pressure. ST segment depression followed an increase in pulmonary artery diastolic pressure in only 13 episodes. The times to maximum ST depression and maximum pulmonary artery diastolic pressure rise were similar. Painful and painless ST segment depression could not be distinguished on the basis of the configuration of the ST segment or in terms of the changes in the pulmonary artery diastolic pressure.

Lack of association between prodromes nausea and vomiting, and specific electrocardiographic patterns of acute myocardial infarction

We conducted an observational study on 164 patients consecutively admitted to our coronary care unit in order to evaluate the predictive role of cardiac prodromes nausea and vomiting, in distinguishing a particular electrocardiographic pattern (Q wave versus non-Q wave and localisation) of an acute myocardial infarction. Patients with the prodromes made up 47.0% of all Q wave myocardial infarction and 59.4% in those without Q wave myocardial infarction. Furthermore, patients had nausea and vomiting in 25.0% of all Q wave myocardial infarction and in 31.2% of all non-Q wave infarction. No significant differences were found in the patients who experienced nausea and vomiting in the localisation (anterior versus inferior) of myocardial infarction. Our findings indicate that the cardiac prodromes of nausea and vomiting do not play any particular role in predicting a specific electrocardiographic pattern of acute myocardial infarction.

Prognosis after extension of myocardial infarct: the role of Q wave or non-Q wave infarction

We examined whether or not subsets of patients with extension of myocardial infarct were at high risk for early and late mortality. Some data suggest increased risk in patients with non-Q wave infarcts and we hypothesized that infarct extension in this group might be associated with a poorer prognosis than that for patients with extension of Q wave infarcts. A total of 1253 patients with acute myocardial infarction who were included in our data base were followed prospectively. The patients were classified according to electrocardiographic results into the following groups: those with non-Q wave (n = 277) infarcts and those with Q-anterior (n = 462) and Q-inferior (n = 497) infarcts. Extension was diagnosed by two of the following criteria: (1) recurrent chest pain 24 hr or more after admission to the hospital, (2) new persistent electrocardiographic changes, and (3) elevation or reappearance of creatine kinase. By these criteria 85 (6%) patients had extension (8% of non-Q wave infarcts, 6% of Q-anterior infarcts, and 6% of Q-inferior infarcts). Hospital mortality in patients with extension was 15% in those with Q wave infarcts vs 43% in those with non-Q wave infarcts (p less than .01). Nine hundred and fifty-two patients were followed for 1 year. In 24% of those who did not survive 1 year there was extension of infarct; only 6% of survivors had extension (p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac receptors: their function in health and disease

Cardiac receptors include both mechanically and chemically sensitive receptors located in atria and in ventricles. Atrial receptors innervated by myelinated vagal afferent fibers reflexly regulate heart rate and intravascular volume. On the other hand, stimulation of ventricular receptors can cause either reflex bradycardia and hypotension or, alternatively, excitation of the cardiovascular system. The former response is mediated by vagal afferents, whereas the latter is mediated by sympathetic (spinal) afferents. Under normal circumstances, cardiac receptors sense changes in wall motion or diastolic pressure and perhaps provide a fine tuning of the cardiovascular system. However, under certain pathological conditions such as coronary ischemia, which cause release of substances such as bradykinin and prostaglandins, there is an exaggerated response of the ventricular receptors. Because these receptors cause a reflex depression of the cardiovascular system and, in particular, induce renal vasodilation, they may protect the heart and kidney by lessening myocardial oxygen requirements and by increasing renal blood flow. In the situation of heart failure both atrial and ventricular receptors are reset and therefore provide for an exaggerated neurohumoral discharge. Finally, patients with aortic stenosis may demonstrate a paradoxical vasodilation and syncope during exercise when there likely is excessive stimulation of left ventricular receptors by the high transmural pressure.

Submaximal exercise testing after stabilization of unstable angina pectoris

To determine the prognostic value of exercise testing in patients with unstable angina pectoris, 125 hospitalized patients were prospectively evaluated soon after stabilization of their pain. Exercise testing was performed after exclusion of acute myocardial infarction and a pain-free period of at least 3 days (mean +/- SD 3.9 +/- 1.4). No complications were noted during or immediately after exercise testing. A positive test (angina or greater than or equal to 1 mm ST segment depression, or both) was noted in 60 patients (48%). During a 1 year follow-up period, 52 (87%) of these 60 patients had an unfavorable outcome (American Heart Association class III or IV angina, recurrent unstable angina, coronary artery bypass surgery, acute myocardial infarction or cardiac death) compared with 19 (29%) of the 65 patients with a negative test (p less than 0.001). The sensitivity and specificity of exercise testing in predicting outcome were 73 and 85%, respectively. The predictive value of a positive test was 87% and that of a negative test was 71%. Angina by itself during the exercise test was a reliable predictor of severe angina (class III or IV angina) at follow-up (sensitivity 92%, specificity 89%, positive predictive value 83% and negative predictive value 95%; p less than 0.001). The findings were not significantly affected by beta-adrenergic blocking agents or digitalis in the study sample. Thus, in patients with unstable angina which has been stabilized, the results of early submaximal exercise testing may be useful in predicting outcome in the first year after hospital discharge. Patients with a positive test result should be considered for further diagnostic studies.

Prognostic implications of early spontaneous angina after acute transmural myocardial infarction

We investigated the clinical, electrocardiographic and hemodynamic features and the prognostic implications of early spontaneous angina in 31 consecutive patients after acute myocardial infarction. Re-elevation of ST segments in the area of infarction occurred during angina and during reinfarction in all but one patient. Depression of ST segments, when present during pain, involved the same leads as in the acute infarction. Blood pressure and double product tended to increase during pain in 23 patients. The magnitude of this change, however, often varied from crisis to crisis and there were no increases in these parameters in one or more attacks in 15 patients. Sublingual nitroglycerin, 1.0 mg, failed to relieve one or all anginal episodes in 17 of the 28 patients in whom it was given. In-hospital mortality rate was 10% (3/31) and always followed reinfarction. In-hospital reinfarction rate was 16% (5/31) and followed a larger number of anginal crises (7.2 +/- 1.3 vs 3.0 +/- 2.1, P less than 0.001) and a higher incidence of transient hypotensive episodes than in the rest of patients (3/5 vs 3/26). Three additional patients died after discharge. Of the remaining 25 patients and during a follow-up of 26 months (16-34) only one developed reinfarction. Early resting angina after a transmural infarction is almost invariably associated with ECG evidence of ischemia in the leads overlying the infarcted zone. The inconsistent changes in blood pressure and heart rate during pain render these hemodynamic changes an unlikely cause of this form of angina. While postinfarction angina did not carry a grave short- or long-term prognosis, patients with recurrent crises demonstrated as high a risk of reinfarction and death as those with spontaneous hypotension.

Unstable angina pectoris: therapeutic choices

Unstable angina by definition involves a progressive process that has the potential for becoming acutely emergent. The authors offer criteria for monitoring the severity of the process, for designing medical therapy, and for making critical decisions with respect to turning from medical management to surgical intervention, either on an elective or an emergency basis.