Coronary hemodynamic findings during spontaneous angina in patients with variant angina

Coronary artery spasm

Coronary artery spasm is a transient reduction in lumen diameter of an epicardial coronary artery of sufficient degree to produce objective evidence of myocardial ischemia in the absence of any significant increase in heart rate or blood pressure. In this article are summarized pathophysiological observations, the coronary angiographic anatomy of patients with coronary spasm, etiologic considerations, methods to provoke coronary artery artery spasm and their clinical usefulness, the role of coronary artery spasm in patients with clinical angina pectoris and myocardial infarction, and finally, the role of coronary artery spasm in patients undergoing coronary artery surgery.

Dynamic variations in resistance of coronary arterial narrowings in angina pectoris at rest

The coronary hemodynamic events in 4 patients with frequent episodes of spontaneous rest angina were investigated. The basal coronary transstenotic pressure gradients showed more severe stenosis than that seen on coronary arteriography, suggesting that angiography in this setting may underestimate the true extent of coronary atherosclerosis. Episodes of angina were triggered by marked, sudden increases in the transstenotic coronary pressure gradient and a decrease in coronary blood flow without alterations in systemic arterial pressure or heart rate. These changes in coronary hemodynamics were promptly reversed by the intracoronary administration of nitroglycerin. No such spontaneous variations in transstenotic coronary pressure gradients were observed in 37 patients with a history of classic exertional angina but no rest angina. These unique data represent direct hemodynamic evidence that an increase in resistance at the site of a coronary stenosis, most likely the result of an increase in arterial tone, can be a cause of transient myocardial ischemia in patients with angina at rest.

Unstable angina pectoris: the first half century: natural history, pathophysiology, and treatment

Unstable angina pectoris as a distinct syndrome intermediate between chronic stable angina and acute myocardial infarction was first described about a half century ago. The incidence of death or myocardial infarction rises in the first few months after destabilization of angina. Hemodynamic, scintigraphic, and arteriographic studies in the last 15 years have shown that unstable angina is chiefly due to "dynamic" coronary stenoses, transient reversible limitations in coronary blood flow caused by a complex interaction between coronary vasoconstriction, transient platelet plugging, and transient thrombosis. The trigger for the onset of dynamic coronary stenoses is probably acute changes in coronary arterial morphology in or near atherosclerotic plaques making those areas more thrombogenic. A large fraction of patients with unstable angina restabilize initially with medical management. The role of beta blockers is unclear, but they may protect against development of coronary events for patients with unstable angina similar to that reported for patients with myocardial infarction. Nitrates and calcium blockers are probably superior to beta blockers in restabilization of angina, but protection against coronary events has not yet been demonstrated clearly. Further investigation is needed to distinguish the relative benefits of a two-drug (heart rate-limiting calcium blocker plus nitrates) regimen vs. a three-drug regimen including beta blocker. There is no basis for emergency coronary bypass surgery to prevent myocardial infarction or death. Urgent surgery should be limited to patients who do not stabilize readily with medical therapy. One third or more of the patients who initially restabilize with medical therapy will require coronary revascularization in the year after unstable angina because of severe angina. An antithrombotic regimen of aspirin (or possibly heparin) reduces the incidence of progression to death or myocardial infarction. Two important future directions for research should be promising: development of better antithrombotic regimens other than aspirin alone for protection against coronary events; and improved ability to distinguish the patients who initially respond to medical therapy who are at low risk for later severe angina from those at higher risk.

Functional significance of transient collaterals during coronary artery spasm

Coronary collateral vessels appear transiently during vasospasm. To examine the functional role of such collaterals in acute myocardial ischemia, regional coronary flow was determined in patients who showed isolated total spasm in the proximal left anterior descending coronary artery associated with (n = 7, group I) and without (n = 9, group II) collaterals, which were donated by the nonspastic right coronary artery during ergonovine provocative test. Aortic pressure and heart rate were not significantly different in the 2 groups before and during spasm. During vasospasm, the levels of pulmonary artery end-diastolic pressure were significantly higher in group II (19 +/- 2 mm Hg, mean +/- standard error) than in group I (15 +/- 1 mm Hg, p less than 0.05). Under these conditions, great cardiac vein flow (GCVF) measured by thermodilution was markedly reduced in group II (from 60 +/- 4 ml/min to 37 +/- 4 ml/min, p less than 0.01), whereas GCVF was slightly reduced in group I (from 56 +/- 4 ml/min to 51 +/- 4 ml/min), indicating that residual GCVF was greater in patients with than in those without collaterals (p less than 0.05). The calculated coronary collateral resistance index during vasospasm was significantly lower in group I (2.06 +/- 0.18 mm Hg min/ml) than in group II (2.91 +/- 0.30 mm Hg min/ml, p less than 0.05). Total left anterior descending coronary artery spasm with collaterals was less frequently associated with ST elevation in the precordial electrocardiogram recorded during spasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary hemodynamic responses during spontaneous angina in patients with and patients without coronary artery spasm

The mechanisms of spontaneous angina were evaluated during cardiac catheterization in 13 patients who had angina occurring without provocation at rest. Left ventricular and systemic hemodynamics, coronary venous flows (thermodilution technique), electrocardiogram and coronary angiograms were recorded before and during spontaneous angina. Angiography during spontaneous angina showed that 5 patients had coronary spasm (group I) and 8 patients did not (group II). In group II there was a preponderance of multivessel coronary artery disease. Left ventricular end-diastolic pressure increased in all patients in both groups during spontaneous angina. In group I, 4 patients had transient ST elevation and 1 patient had peaked T waves during angina. Transient ST depression occurred during spontaneous angina in all group II patients. Group I patients had decreased coronary sinus flow (4 of 5 patients) or decreased regional flow (5 of 5) during spontaneous angina. Coronary resistance and ratio of double product to coronary blood flow increased in all patients. In group II, coronary hemodynamic responses during spontaneous angina varied. Coronary venous flows, coronary resistance and ratio of double product to coronary blood flow showed no uniform pattern. Thus, patients with severe coronary artery disease can have spontaneous angina without angiographic findings of coronary spasm. After analysis of angiograms and coronary hemodynamics in these patients, no apparent uniform mechanism for spontaneous angina was found.

Effect of nitroglycerin on coronary collateral flow and pressure during acute coronary occlusion

Coronary collateral function was evaluated in 21 conscious, unsedated patients by measuring aortic and distal coronary pressures and great cardiac vein flow during transient (1 minute) balloon occlusion of the anterior descending artery in the course of coronary angioplasty. Measurements were made before and during administration of intravenous nitroglycerin (NTG). Clinical, electrocardiographic and hemodynamic events of transient myocardial ischemia occurred in 10 patients before and 6 patients during NTG administration (p = 0.11). The NTG infusion consistently decreased pressure determinants of myocardial oxygen demand without increasing heart rate. NTG also decreased a calculated coronary collateral resistance index in 13 patients. Responsiveness to NTG did not appear to depend on the presence or absence of collateral vessels detected by angiography or on any other angiographic variable assessed. Measurement of coronary collateral function during coronary angioplasty is a new technique with the potential to assess the ability of interventions to prevent transient myocardial ischemia and improve myocardial perfusion during acute coronary occlusion in humans.

Regional myocardial dysfunction in patients with angina at rest and response to isosorbide dinitrate assessed by phase analysis of radionuclide ventriculograms

Left and right ventricular synchrony was assessed in 15 patients with angina at rest but no previous infarction by phase analysis of equilibrium radionuclide ventriculograms. Transient thallium-201 perfusion defects were noted in all during angina at rest and coronary vasospasm was documented in nine of the patients. Radionuclide ventriculograms were performed at control, during the ischemic episodes and after intravenous isosorbide dinitrate. Left and right ventricular phase histograms were quantified by the standard deviation from the mean of the peak (SD). Left ventricular ejection fraction averaged 65 +/- 11% (mean +/- standard deviation) at control, decreased in all patients during angina at rest to 49 +/- 14% (p less than 0.01) and increased in all patients after isosorbide dinitrate to 66 +/- 12%. However, ejection fraction during ischemia was abnormal in only nine patients and changed in two by less than 5% from the control value. Regional wall motion abnormalities were noted in all patients during the ischemic episodes but resolved after isosorbide dinitrate administration. Control left ventricular SD was 14.5 +/- 4 degrees, increased in all patients to 22.8 +/- 5 degrees during angina at rest (p less than 0.01) and returned to control values after isosorbide dinitrate administration (14.2 +/- 4 degrees). In contrast, right ventricular SD did not significantly change during ischemia as compared with control and isosorbide dinitrate. It is concluded that in angina at rest, a normal left ventricular ejection fraction does not exclude severe regional dysfunction; separate left and right ventricular SD is a sensitive index in detecting transient left ventricular dysfunction, and relief of ischemia is associated with rapid normalization of regional left ventricular function.

Electrocardiographic changes with coronary artery spasm

The presence or absence of important ECG changes (e.g., ST elevation or depression greater than or equal to 1 mm) was evaluated in 79 consecutive patients with coronary artery spasm. In eight of these patients ECG changes usually did not accompany episodes of rest angina. Evaluation before, during, and after cardiac catheterization included multiple ECGs and ambulatory monitoring during angina. Our observations suggest that the ECG may not always be a sensitive indicator of coronary spasm. Thus the diagnosis of transient myocardial ischemia secondary to coronary spasm should not necessarily be excluded because of a lack of ECG changes during rest angina.

Comparison of coronary hemodynamic effects of nitroprusside and sublingual nitroglycerin with anterior descending coronary arterial occlusion

This study compares the coronary hemodynamic effects of an infusion of nitroprusside and of sublingual nitroglycerin in the same patients. The coronary hemodynamic responses of the anterior left ventricular (LV) region to both drugs were studied in 9 patients whose anterior descending branch of the left coronary artery was filled by collaterals. Before and during administration of each drug (given in doses designed to produce similar changes in LV diastolic pressure), heart rate, LV and aortic pressure, and anterior regional flow, oxygen delivery and lactate metabolism were measured. Given in this manner, as expected, both drugs decreased the double product of heart rate and systolic pressure. Concomitant with these changes, anterior regional blood flow increased or decreased modest amounts or did not change with either drug. Similar directional flow changes or no change occurred in 6 patients and directionally different changes in the other 3 patients. The ratio of mean aortic pressure or of the double product to anterior regional flow consistently decreased during the administration of both drugs. Additionally, anterior regional myocardial oxygen uptake remained similar during both drug periods compared with control values. Anterior region lactate extraction was abnormal (less than 10%) in 4 of the 9 patients during the initial control period. Lactate extraction was usually normal during both the nitroprusside and the nitroglycerin periods. In general, coronary hemodynamic values were remarkably similar during both of these periods. Thus, although relative differences in systemic arterial and venous dilation were obtained with nitroprusside and nitroglycerin, similar and beneficial coronary hemodynamic changes generally occurred.

Regional coronary venous flow responses to transient coronary artery occlusion in human beings

Coronary hemodynamic responses to transient coronary artery occlusion in 21 patients were investigated by using regional coronary venous thermodilution to measure regional coronary venous flows. Transient coronary artery occlusion was produced by coronary artery spasm (13 patients) or balloon inflation during coronary angioplasty (8 patients). The left anterior descending coronary artery was transiently occluded in 12 patients, the right coronary artery in 8 patients and the left circumflex artery in 1 patient. During transient coronary occlusion, regional venous flow decreased in 20 of the 21 patients (79 +/- 31 to 53 +/- 29 ml/min, mean +/- standard deviation [SD]; probability [p] less than 0.05) corresponding to the left ventricular region perfused by the occluded artery. Regional coronary resistance increased in all 21 of these regions (1.42 +/- 0.75 to 2.26 +/- 1.45 mm Hg/ml per min, p less than 0.05). Simultaneously measured blood flow and resistance in the left ventricular region supplied by the nonoccluded arteries did not change significantly (62 +/- 27 to 64 +/- 29 ml/min and 1.85 +/- 0.93 to 1.81 +/- 0.98 mm Hg/ml per min, respectively). Coronary hemodynamic changes were similar during transient coronary occlusion, whether produced by coronary spasm or by balloon inflation. However, the presence of angina, reversible electrocardiographic abnormalities and an increase of the left ventricular filling pressure were more common during coronary spasm (p less than 0.05 for all). Regional coronary hemodynamic changes during transient occlusion of the anterior descending, circumflex or right coronary artery were similar. These data show that coronary occlusion decreases regional left ventricular flow in the region perfused by the affected artery. The method of coronary occlusion or the coronary artery affected during occlusion did not seem to elicit different responses.

Intravenous nitroglycerin for the treatment of angina at rest unresponsive to standard nitrate therapy

Thirty-five patients who had angina at rest that was unresponsive to standard therapy comprised of oral or topical nitrates and beta-blocking drugs were treated with a continuous infusion of intravenous nitroglycerin (IVNTG). The infusion was started at 10 micrograms/min and increased by 10 micrograms/min increments every 5 minutes until an infusion rate of 50 micrograms/min was reached. After each episode of rest angina, the infusion was increased by 50 micrograms/min in the same stepwise manner. Data from a 24-hour baseline control period were compared with those from a 24-hour IVNTG endpoint period at which time the highest IVNTG infusion rate was administered. The average IVNTG infusion rate was 140 +/- 15 micrograms/min. With IVNTG therapy, the number of episodes of angina at rest decreased from 3.5 +/- 0.4 to 0.3 +/- 0.1, sublingual nitroglycerin use decreased from 1.9 +/- 0.3 to 0.4 +/- 0.1 mg/day, and morphine sulfate administration decreased from 5.5 +/- 1.3 to 0.4 +/- 0.2 mg/day (all p less than 0.001). When each patient's response on the endpoint day was analyzed, 25 were defined as complete (no rest angina), 8 as partial (greater than 50% decrease in the number of episodes/day from control values), and 2 as nonresponders. No significant drug-induced adverse effects occurred. IVNTG appears to be effective therapy for angina at rest refractory to standard oral and topical medications.

Variability in coronary hemodynamics in response to ergonovine in patients with normal coronary arteries and atypical chest pain

Because an increase in coronary vascular resistance in response to ergonovine maleate has been suggested as a possible diagnostic aid for variant angina, changes were evaluated in coronary hemodynamics and serial myocardial thallium-201 perfusion scans in 15 patients without angina and with normal coronary arteries in response to ergonovine (0.05, 0.10 and 0.20 mg intravenously). For the group, heart rate-blood pressure product increased significantly (p less than 0.001) without any change in coronary sinus flow, coronary vascular resistance, myocardial oxygen extraction, arterial-coronary sinus oxygen difference and lactate extraction. In 7 of 15 patients, however, coronary vascular resistance increased (mean 39%, range 11 to 75%, probability [p] less than 0.001), and coronary sinus flow decreased (14%, p less than 0.001), despite an increase in heart rate-blood pressure product (36%, p less than 0.02). No electrocardiographic, metabolic or thallium-201 scan abnormalities occurred. Therefore, significant increases in coronary vascular resistance in response to ergonovine may occur in patients with normal coronary arteries and atypical chest pain.

Short- and long-term responses to diltiazem in patients with variant angina

Short- and long-term effects of diltiazem on angina frequency were studied in 12 patients with variant angina (pain at rest with S-T elevation). Each patient first entered a double-blind short-term trial. Either diltiazem, in two dosage schedules (120 and 240 mg/day), or placebo was administered in a randomized double-blind program over 10 weeks. Significant decreases in frequency of angina were observed when diltiazem treatment periods were compared with placebo periods. Six patients were asymptomatic, one had 50 percent or greater decrease, and two had a smaller decrease in angina frequency. Two patients showed no important improvement during short-term diltiazem therapy. One patient experienced ventricular fibrillation in the placebo period and was advanced to treatment with open label diltiazem before responses could be ascertained in the double-blind trial. All other patients were then advanced to open label diltiazem therapy and followed up for an average of 16 months (range 8 to 23). Responses during the short-term trial accurately predicted responses during long-term therapy. Of the six patients who were asymptomatic during short-term therapy, five remained asymptomatic and one had rare episodes of angina. One other patient continued to have a good response (50 percent or greater decrease in angina frequency) and two other patients had a partial response. The two patients who did not respond during short-term therapy did not respond during long-term therapy.