Transient transmural reduction of myocardial blood flow demonstrated by thallium-201 scintigraphy, as a cause of variant angina

Effects of platelet inhibition on myocardial ischaemia

Ticlopidine, a potent inhibitor of platelet aggregation, was found to have no direct effects on coronary resistance or coronary flow in 5 dogs. To determine whether platelets can be implicated in the pathogenesis of myocardial ischaemia the effects of this drug were studied in 10 patients with proven coronary-artery disease and daily angina pectoris. Each underwent three single-blind treatments: (a) placebo for 2 weeks; (b) ticlopidine 500 mg for 4 weeks; and (c) placebo for 2 weeks. For 4 days after the end of each treatment ambulatory S-T segments were monitored and a record was kept of the reported frequency of chest pain. 4 weeks' treatment with ticlopidine resulted in a significant fall in both the reported frequency of chest pain and the number of episodes of S-T segment depression. This effect was most striking in those episodes of S-T segment depression that occurred without increase in heart rate and in the middle of the night. Thus, although the exact mechanisms remain to be clarified this study suggests that platelets may play an important part in the pathogenesis of myocardial ischaemia.

Pharmacologic effects of a nitrate coronary vasodilator on cardiac perfusion and function, measured semiquantitatively

Peritrate (pentaerythritol tetranitrate), a nitrate coronary vasodilator, was capable of significantly increasing perfusion and function in ischemic heart muscle. The A2 image-processing computer with software developed by Burow was used to evaluate regional perfusion and segmental wall motion in six patients with ischemic areas in the myocardium. These image-processing techniques were satisfactory for evaluation of ischemic heart muscle.

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.

Processing of 201T1 serial images for the assessment of myocardial clearance and redistribution

Regional activity changes over the myocardium after IV injection of 201T1 were assessed in 90 patients by applying a superposition algorithm for paired images. The kinetics were expressed as quotients C1/C2 of the initial divided by the delayed count rate within any myocardial segment. Regarding the total left ventricular myocardium, normal subjects showed count rate ratios (C30 min/C4 h) of 1.75 +/- 0.075 (SD, n = 19) when the nuclide was injected under submaximal (80% of maximum) exercise. In patients with triple-vessel disease (n=21) the corresponding values were 1.46 +/- 0.05, in single-vessel (n=14) disease the quotients averaged 1.62 +/- 0.12. Average quotients in poststenotic myocardial segments increased from 1.46 before to 1.73 following bypass surgery in cases of graft patency (n=8), while a decrease was observed in a patient with occlusion of the bypass graft. In small-vessel disease and in congestive cardiomyopathy, global values of 1.50 +/- 0.07 (n=7) and 1.53 +/- 0.12 (n=19) were obtained. The display of C1/C2 matrices provided typical patterns in uptake defects caused by ischemic heart disease and by congestive cardiomyopathy. The procedure described may provide diagnostic information in addition to conventional myocardial scintigraphy in triple-vessel disease, in patients with angina who fail to demonstrate hemodynamically significant coronary artery stenoses, and in patients with inhomogeneous T1-scintigrams.

Nifedipine in unstable angina: a double-blind, randomized trial

We assessed the efficacy of adding nifedipine to the conventional treatment of unstable angina in 138 patients in a prospective, double-blind, randomized, placebo-controlled trial. There was no difference between the two groups in the dose of conventional antianginal medication or in age, prior myocardial infarction, ejection fraction, or other risk factors. Failure of medical treatment (defined as sudden death, myocardial infarction, or bypass surgery within four months) occurred in 43 of 70 patients given placebo and in 30 of 68 given nifedipine. Kaplan-Meier survival-curve analysis of the number and time dependence of treatment failures demonstrated a benefit of nifedipine over placebo (P = 0.03). The benefit was particularly marked in patients with ST-segment elevation during angina (P = 0.02). Side effects (transient hypotension or diarrhea) required withdrawal of the drug from four patients given nifedipine and from one given placebo. We conclude that the addition of nifedipine to conventional therapy is safe and effective in unstable angina.

Gamma camera quantitation of thallium-210 redistribution at rest in a dog model

Defects seen at rest on thallium-201 (201TI) scintigraphy can disappear over time. We obtained sequential 5-minute scans over 127 +/- 9.4 minutes in seven open-chest dogs with fixed, stable regional flow reductions (normal zone flow 0.76 +/- 0.09 ml g-1/min, ischemic zone flow 0.49 +/- 0.04 ml g-1 min [mean +/- SEM], p less than 0.05) as determined by microsphere injection. Sequential 5-minute scans were obtained after i.v. injection of 1.5 mCi of 201TI. Data were stored in a 64 x 64 pixel computer matrix. Qualitatively, defects that showed redistribution were seen in all dogs. Quantitatively, greater count loss from peak activity distinguished the normal zone, but overlap was great. Alternate quantitative methods using background subtraction altered the characteristics of the time-activity curves, but did not enhance the separation of ischemic from normal zones. Patterns of 201TI redistribution from gamma camera imaging are profoundly influenced by the method of quantitation. No single method of quantitative analysis separated ischemic from normal zones in all dogs. The clinical significance of patterns at rest requires redefinition.

Role of coronary arterial spasm in sudden coronary ischemic death

Sudden coronary death is a syndrome caused by different mechanisms, all of which should be separately considered with respect to preventive measures. Ventricular fibrillation, tachycardia, and complete atrioventricular block were repeatedly observed during ischemic episodes caused by spasm in both the presence and absence of anginal pain. Spasm is, therefore, a potential cause of sudden coronary death. In "variant" angina, which is a reasonably reliable indicator of coronary spasm, arrhythmias occur in about 25% of patients and tend to recur in the same patient. The severity of coronary atherosclerosis in patients who develop severe arrhythmias is quite variable and not dissimilar from patient who do not. Mortality is considerably higher in patients with severe disease, but fibrillation and death can occur also in patients with angiographically normal arteries. In these patients acute and long-term treatment with nitrates and slow channel blockers appears to give remarkable results. Prevention of arrhythmias in patients in whom arrhythmias are secondary to acute ischemic episodes caused by vasospasm should be attempted by preventing vasospasm.

Transient giant R waves in the early phase of acute myocardial infarction: association with ventricular fibrillation

An unusual electrocardiographic (ECG) pattern was observed in five patients who suffered an acute anterior myocardial infarction. Early in their illness and following resuscitation from ventricular fibrillation (three patients), in the midst of recurrent ventricular irritability prior to development of ventricular fibrillation (one patient), and following a period of seizures (one patient), the ECG showed ST-segment elevation, marked increase in the R-wave amplitude, disappearance of S waves and merging of QRS complexes with the elevated ST segments, ECG patterns noted in these patients were similar to the ones recorded from dogs immediately after ligation of a large coronary artery, and from patients with severe episodes of variant angina. Although these early electrocardiographic changes probably reflect either marked regional transmural blood flow deprivation or its aftermath, they could not be taken as indices of eventual massive myocardial necrosis since in most of these patients the alterations were followed by development of nontransmural myocardial infarction. The possible mechanisms and the implications of such discrepancy between early and late electrocardiographic indicators of injury or necrosis is discussed.

Dynamic coronary tone in precipitation, exacerbation and relief of angina pectoris

Until recently, understanding of the pathogenesis of angina pectoris was based primarily on the concept of a fixed stenosis of one or more coronary arteries: Myocardial ischemia and angina occurred when myocardial oxygen consumption (MVO2) outstripped the capacity of the diseased coronary artery to delivery oxygen. Therapeutic strategies focused on interventions designed to reduce MVO2. The concept of dynamic obstruction, first applied to coronary spasm induced at rest and more recently to spasm induced by exercise, adds an additional important pathophysiologic mechanism responsible for causing angina pectoris. This study deals with the possibility that the concept of "spasm," as commonly understood, is too narrowly defined. It develops the hypothesis that subcritical increases in large vessel coronary tone occur, either in a "normal" coronary artery or in one with an existing lesion, that augment the degree of large vessel coronary resistance but not enough to exceed the vasodilator reserve of the coronary arterioles. Hence, although total coronary resistance, and thereby coronary flow, is unaltered at rest, the impingement on arteriolar vasodilator reserve would diminish the capacity to augment flow in response to increases in MVO2. Such coronary constriction would not precipitate angina at rest but would increase anginal threshold. Conversely, dilatation of a stenotic coronary artery could decrease the degree of obstruction and increase anginal threshold. This concept of dynamic coronary obstruction in the presence of "normal" or diseased coronary arteries implies a direct role for coronary vasodilators in some patients with angina pectoris, even when frank coronary spasm is absent. Also implicit in this hypothesis is the concept that dynamic and fixed components to obstruction may contribute variably to the degree of obstruction in different patients. Some patients with largely fixed obstruction would benefit mainly from attempts to lower MVO2 with nitrates and beta blocking agents. Dynamic coronary obstruction may constitute the major mechanism responsible for angina in other patients. In these persons nitrates or calcium channel blocking agents might provide the most efficacious form of therapy. Both fixed and dynamic obstruction may play an important role in symptom production in yet other patients. In such persons attempts to decrease MVO2 and the magnitude of coronary obstruction might provide the most successful form of therapy.

Prognostic significance of electrocardiographic findings in angina at rest. Therapeutic implications

Ninety-five patients with angina at rest were observed in the coronary care unit. Eighty-one per cent presented concomitantly or had previously presented some other manifestations of coronary artery disease. These patients were divided into two subgroups. In subgroup 1 (40 patients), episodes of non-exertional angina were associated with a pattern of hyperacute subepicardial injury and, frequently, with ventricular arrhythmias. In subgroup 2 (55 patients), the episodes of angina at rest were attended by horizontal ST depression, isolated T wave inversion, or trivial ST-T changes. Coronary angiographic findings were similar in both subgroups. Symptoms regressed in only 9% of patients in subgroup 1 while they were receiving beta-receptor antagonists, whereas amiodarone alone or amiodarone with nifedipine was successful in 58%. Of these patients, 25% developed a myocardial infarction shortly after admission. In subgroup 2 patients, beta-blockers were successful in 61%. Amiodarone isolated or associated with nifedipine was successful in 55% of the patients in whom it was tried. Only 5% of patients in this subgroup developed a myocardial infarction during their hospital stay. It is concluded that: (1) observation of the electrocardiogram during spontaneous angina in patients with known atherosclerotic coronary heart disease may be of prognostic significance and may influence therapeutic decision. (2) Amiodarone by virtue of its anginal and antiarrhythmic properties may be particularly useful in the treatment of non-exertional angina.

Effect of stenosed and occluded coronary arteries on immediate and late myocardial uptake of thallium-201

Exercise and redistribution myocardial scintigraphy using thallium-201 was compared with the left ventricular angiogram and with the presence of stenosis or occlusion of coronary arteries on angiography. Irreversible scintigraphic defects representing areas of myocardial infarction were found in all patients with occlusion of the left anterior descending artery but nearly one-third of patients with stenosis of that artery also showed evidence of infarction. For the right coronary or circumflex arteries the incidence of infarction was 82% with vessel occlusion and 57% with vessel stenosis. Of abnormally contracting segments on the left ventricular angiogram, 95% showed irreversible scintigraphic defects but 33% of normally contracting segments supplied by a diseased artery also showed this. Myocardial infarction is not uncommon in patients with angina even in the absence of coronary occlusion. The incidence is underestimated by the left ventricular angiogram. These findings are of importance in the assessment of patients with coronary disease and their evaluation before coronary artery surgery.

Experience with ergonovine provocative testing for coronary arterial spasm

We reviewed our experience with the ergonovine provocative test for coronary arterial spasm in 40 patients with pain in the chest believed to be angina pectoris and in one patient with a myocardial infarction and normal coronary arteries. Twenty-nine patients had normal coronary arteries, while 12 had mild to moderate lesions. Ergonovine maleate was administered incrementally in total cumulative doses of 0.25 mg to 1.2 mg. The effect of ergonovine on coronary arterial caliber was determined by comparing the arterial diameter from the angiogram obtained after administration of ergonovine with that from the control. Measurements were made at the same preselected points in both films and also at points of greatest response. Excluding the three cases with complete occlusion, the mean reduction in coronary arterial diameter at preselected points was 12 +/- 15 percent. When the points of greatest response were examined, the maximum reduction in coronary arterial diameter was less than 25 percent in 13 patients, 25 to 50 percent in 20 patients, and more than 50 percent in eight patients. The patterns of response included complete occlusion of a vessel in the three patients with variant angina, diffuse narrowing in 16, diffuse and focal narrowing in six, and spasm at the catheter tip in three patients. All patients with maximum reductions of more than 50 percent in coronary arterial diameter and six of those with maximum reductions of 25 to 50 percent had pain in the chest, but only the three with complete occlusion had associated changes in the S-T segment. Thus, the response in patients with variant angina represents one end of a spectrum of responses to administration of ergonovine. In addition, a large number of patients may have ergonovine-induced pain in the chest without electrocardiographic changes and only an intermediate degree of coronary arterial spasm.

Significance of exercise-induced ST-segment elevation in patients without myocardial infarction

Sixteen patients with exercise-induced ST-segment elevation and without a history of myocardial infarction or left ventricular aneurysm were studied. Fourteen complained of angina at rest, which was associated with ST-segment elevation in the same leads where it was recorded during exercise, and two patients had only exertional angina. Exercise-induced ST-segment elevation was generally reproducible in subsequent exercise tests performed in different hours of the day, but exercise tests repeated a mean of 15 months later did not induce this electrocardiographic abnormality. All patients had a marked susceptibility to coronary spasm, as shown by the response to the ergonovine test (12 positive tests in 12 patients) and by the occurrence of spontaneous spasm during coronary arteriography in two patients. In addition, coronary arteriography, performed in seven patients at the time of exercise-induced ST-segment elevation, revealed spasm of a major coronary vessel in all. In two patients we documented that exercise-induced ST-segment elevation was accompanied by a decreased coronary blood flow and increased coronary vascular resistance. We conclude that exercise-induced ST-segment elevation in patients without a history of myocardial infarction or left ventricular aneurysm is caused by coronary spasm of a major coronary vessel.

Exercise testing and thallium-201 myocardial imaging in relation to coronary artery disease in patients with severe aortic valve disease

Thirty-three patients with aortic valve disease, fifteen with regurgitation, eleven with stenosis and seven with mixed disease, undergoing assessment for valve replacement which included adequate coronary angiography, were studied. A symptom limited graded treadmill exercise test was undertaken with administration of 40-70 MBq of 201Tl. Myocardial imaging was started within 15 minutes and repeated after four hours using a 37 PM tube Searle gamma camera. Myocardial images were read independently by three observed. Of the 33 sets of images, 21 were -ve, 5 +ve, 2 I (Indeterminate) and 5 D (Difference of opinion). Eight of the 33 patients had significant coronary artery disease (CAD) and of these three were scored +ve (all triple vessel). Two patients without CAD were scored +ve. Eight subjects developed angina during exercise testing, of whom four had CAD, and four with CAD did no develop angina. Historically, 13 of the 33 subjects had typical angina, six having CAD; an additional eight had other significant chest pain, two having CAD. In these subjects with severe aortic valve disease, exercise testing and myocardial imaging with 201 TI was of little value in detecting CAD. All patients with CAD gave a history of significant chest pain.

Nifedipine therapy for coronary-artery spasm. Experience in 127 patients

We report clinical experience with the coronary vasodilator nifedipine in 127 patients with symptoms of myocardial ischemia associated with electrocardiographic or angiographic evidence, or both, of coronary-artery spasm. In the majority of patients conventional antianginal therapy including nitrates and beta-adrenergic blockers failed, and in one third of the patients at least one episode of ventricular tachycardia developed during an attack of angina. Nifedipine (40 to 160 mg every 24 hours) significantly reduced the mean weekly rate of anginal attacks from 16 to two (P less than 0.001). Similar marked reductions in the nitroglycerin requirement were noted. In 63 per cent of the patients complete control of anginal attacks was achieved, and in 87 per cent the frequency of angina was reduced by at least 50 per cent. Nifedipine was generally well tolerated, with only 5 per cent of the patients requiring termination of the drug because of intolerable side effects. This experience with nifedipine suggests that it is a highly effective drug for the treatment of coronary-artery spasm and variant angina.

Angiographic demonstration of different pathogenetic mechanisms in patients with spontaneous and exertional angina associated with S-T segment depression

Three patients complained of spontaneous and exertional chest pain, both associated with S-T segment depression in anterior electrocardiographic leads. In each, coronary spasm was demonstrated on coronary arteriography during a spontaneous attack of pain. Coronary arteriograms taken during exercise-induced angina did not show evidence of spastic obstruction; this suggests that exercise-induced chest pain and S-T segment depression were secondary to the increase in oxygen requirements rather than to a sudden decrease in coronary blood flow. Thus, two pathogenetic mechanisms coexisting in the same patient may cause chest pain associated with subendocardial ischemia.

Pathogenetic mechanisms of angina pectoris: expanding views

Images

Treatment of angina at rest with nifedipine: a short-term controlled study

The effectiveness of nifedipine in treating angina pectoris at rest was evaluated in 14 patients with frequent ischemic episodes associated with S-T segment elevation or depression. The trial consisted of (1) a 48 hour control period; (2) a placebo period and a period of treatment with nifedipine of 48 hours each; and (3) a second placebo period and a second period of treatment with nifedipine of 24 hours each. The efficacy of treatment was evaluated by continuous electrocardiographic recording to detect painless ischemic episodes. During coronary angiography coronary spasm was demonstrated in five patients. The ergonovine maleate test was positive in seven of eight patients. No statistically significant difference was found in the mean daily number of ischemic episodes between the control period and the first placebo period, or between the control and the second placebo periods. Nifedipine produced a highly significant reduction in the mean daily number of episodes compared with the response to placebo during the first as well as the second period. Nifedipine is effective in angina at rest caused by coronary arterial spasm. The prevention of ischemia may be related to the ability of nifedipine to decrease calcium-dependent coronary muscle tone and to prevent coronary spasm.

Sequence of events in angina at rest: primary reduction in coronary flow

To investigate the events that lead to acute myocardial ischemia we monitored continuously the ECG, the left ventricular (four patients) or aortic (two patients) pressure and the great cardiac vein oxygen saturation (CSO2S) by a fiberoptic catheter in six patients with frequent anginal attacks at rest. We recorded 137 transient ischemic episodes (10 with chest pain) characterized by ST-segment elevation in 28 episodes, depression in three episodes and by pseudonormalization of previously inverted or flat T waves in 106 episodes. The onset of electrocardiographic and hemodynamic changes was preceded by a large drop in CSO2S in all 135 episodes with ST-T changes in the anterior leads but not in two episodes with ST elevation on inferior leads. The fall in CSO2S, consistently followed by signs of left ventricular function impairment and never preceded by any detectable increase in the hemodynamic determinants of myocardial oxygen consumption, probably reflects a reduction in regional perfusion. Thus, a reduction in coronary flow may cause transient ischemia in patients with angina at rest. These episodes may be associated with variable, often minor electrocardiographic changes and occasionally with anginal pain.

Thallium-201 myocardial scintigraphy in acute myocardial infarction and ischemia

Thallium-201 scintigraphy provides a sensitive and reliable method of detecting acute myocardial infarction and ischemia when imaging is performed with understanding of the temporal characteristics and accuracy of the technique. The results of scintigraphy are related to the time interval between onset of symptoms and time of imaging. During the first 6 hr after chest pain almost all patients with acute myocardial infarction and approximately 50% of the patients with unstable angina will demonstrate 201TI perfusion defects. Delayed imaging at 2--4 hr will permit distinction between ischemia and infarction. In patients with acute myocardial infarction, the size of the perfusion defect accurately reflects the extent of the infarcted and/or jeopardized myocardium, which may be used for prognostic stratification. In view of the characteristics of 201TI scintigraphy, the most practical application of this technique is in patients in whom myocardial infarction has to be ruled out, and for early recognition of patients at high risk for complications.

The evaluation of ischemic heart disease thallium-210 with comments on radionuclide angiography

Coronary artery disease causing myocardial ischemia and infarction is the leading cause of death in America. Methods that can be used to diagnose and follow the response to therapy of coronary artery disease or its effect on myocardial ischemia should help control the morbidity and mortality of ischemic heart disease. The use of ECG monitoring is less sensitive and specific for ischemia than thallium (TI) imaging or the use of radionuclide angiography (RNA). In large patient populations, the findings of a positive ECG and TI or RNA study will be highly predictive for the presence of coronary artery disease, while negative test results make the disease unlikely. A combined approach to the patient with possible ischemic heart disease is presented.

Some clinical considerations regarding the relation of coronary vasospasm to coronary atherosclerosis: a hypothetical pathogenesis

This study explores the relation between coronary arterial spasm and the development of coronary atherosclerosis. The clinical history and coronary angiographic and electrocardiographic data in 212 consecutive patients with ischemic heart disease were correlated. These patients were classified into four groups: Group 1, patients without angiographic evidence of atherosclerosis; Group 2, patients with single vessel disease; Group 3, patients with double vessel disease; and Group 4, patients with significant narrowing of major coronary arteries. Although spontaneous angina occurred in all four groups, it was more common (55 percent) in the patients in Group 1, who were predominantly female and young. Spontaneous angina was confirmed in Group 1 with several techniques, including thallium-201 scintigraphy, ergonovine administration and electrocardiography during attacks of pain. Prior myocardial infarction was present with similar frequency in all four groups. A patient is discussed whose spontaneously occurring coronary arterial spasm later progressed to fixed arteriosclerotic narrowing requiring coronary bypass surgery. These observations and a review of the literature lend support to the hypothesis that coronary arterial spasm can be a possible antecedent leading to the later development of fixed atherosclerotic coronary arterial obstruction.

A consideration of factors affecting the diagnostic accuracy of thallium-201 myocarial perfusion scintigraphy in detecting coronary artery disease

Several factors influence the ability of TI-201 myocardial perfusion scintigraphy to detect coronary artery disease. Among these are the physiologic effect of the coronary lesion on relative myocardial perfusion and radionuclide distribution; technical and physiologic aspects of the scintigraphic process; and observer interpretation. The diagnostic accuracy of this scintigraphic method is related to: (1) the extent of the hypoperfused myocardium, which will depend on the severity and extent of coronary disease, the presence of collaterals, the exercise method, and the timing of thallium administration and scintigraphy; (2) the scintigraphic process, which depends on the nature of the isotope, the imaging system, and the method of image display; and (3) image interpretation, which depends on the experience of the observer as well as on the area of hypoperfused myocardium and the scintigraphic process. The diagnostic accuracy of scintigraphy for detecting coronary disease can be optimized by computer methods of image enhancement, which maximize differences in image contrast; by electrocardiographic gating; and by emission computer tomography. Other computer methods have been developed to reduce or eliminate observer intervention in interpretation and to increase the objectivity of the method.

Nuclear cardiology. II. The role of myocardial perfusion imaging using thallium-201 in diagnosis of coronary heart disease

Since its introduction, thallium-201 has become the agent of choice in the clinical assessment of relative myocardial perfusion. Extensive evaluation has shown that it is of particular value in the diagnosis of coronary heart disease in patients with baseline S-T segment abnormalities or an inadequate heart rate response resulting in an inconclusive exercise electrocardiographic response. In addition, thallium-201 imaging is of value in the patient with a suspected false positive stress test; however, the definite incidence of false negative studies in patients with coronary heart disease tempers complete reliance on this approach. In the patient with a diagnostic exercise electrocardiographic stress test, thallium-201 provides limited additional information. Moreover, current techniques of analysis do not permit assessment of the number of coronary arteries with obstructive lesions. In the setting of acute myocardial ischemia, the role of thallium-201 is less clear. In acute myocardial infarction, the significant incidence of false negative responses combined with a multiplicity of potential causes of resting defects including severe but chronic coronary disease or unstable angina limits its diagnostic value.

Coronary arterial spasm in angina at rest associated with transient ST-segment changes

In order to clarify the role of coronary arterial spasm in the pathogenesis of angina at rest, coronary arteriography was perforned during spontaneous chest pain or following intravenous administration of ergonovine maleate in 40 patients with angina at rest. Coronary vasospasm was demonstrated in 23 patients with ST-segment elevation during chest pain (group I), in 7 with ST-segment depression (group II), and in 4 with both ST-segment depression and elevation (group III). Complete spastic occlusion of the proximal or of the midportion of the left anterior descending artery was always associated with ST-segment elevation in anterior leads. In contrast, transient ST-segment depression in anterior leads was associated with diffuse narrowing of the left anterior descending artery with slow progression of the contrast medium, or complete occlusion of a small branch or of the distal segment of the left anterior descending artery. ST-segment elevation in inferior leads was associated with complete spastic occlusion or with significant spastic narrowing of the right coronary artery or of the circumflex artery. We conclude that coronary spasm can be demonstrated in a selected cohort of patients with angina at rest associated with transient ST-segment changes. In some cases the site and the severity of the spasm may produce varying degrees of ischemia, thus determining the direction of the ST-segment shift.