Coronary arterial spasm and Prinzmetal's variant form of angina induced by hyperventilation and Tris-buffer infusion

Perioperative coronary arterial spasm: long-term follow-up

Six patients who survived episodes of coronary arterial spasm occurring immediately after coronary bypass grafting were followed up for 15 to 30 (mean 20) months after operation. In all patients coronary spasm occurred in an unobstructed dominant right coronary artery and caused inferior transmural ischemia. Sudden circulatory collapse occurred in five of the six patients as a consequence of acute coronary spasm. All patients were treated with nitroglycerin followed by nifedipine. No patient has had recurrent angina or other evidence of spontaneous coronary spasm since surgery. Cardiac catheterization studies, including ergonovine maleate testing, were repeated 3 to 12 months after surgery in five of the six patients. The right coronary artery and all bypass grafts were patent in all five. Four patients had new inferior wall motion abnormalities. Ergonovine provoked focal right coronary arterial spasm in one patient. It is concluded that manifestations of coronary spasm after myocardial revascularization range from asymptomatic S-T segment elevation to severe hypotension. These episodes of perioperative spasm may cause myocardial necrosis. Coronary spasm has not recurred in patients who survived perioperative spasm, but some patients may have a continued predisposition to development of coronary spasm late after surgery.

Diurnal variation in exercise responses in angina pectoris

Thirty caucasian male patients with stable angina were investigated in two groups of nine and one group of 12. Nine normal subjects were also studied. Patients in the first group (on no treatment) underwent symptom-limited exercise electrocardiography at 0800, 1200, and 1600 hours on the same day. Their heart rates and ST segment displacements at 1600 hours were significantly greater than at 0800 hours and the same phenomenon was seen in the second group who had been receiving propranolol 40 mg four times a day. A similar effect was noted for ST segment displacement but not for heart rate in the third group (on no treatment) tested at 0800 hours and 1600 hours on separate days, two to three weeks apart. Normal control subjects showed no diurnal variation in heart rate and their heart rate responses at 1600 hours were reduced by propranolol. The observations show a circadian variation in the ST segment response to exercise in patients with angina and a possible training effect on heart rate with multiple exercise testing on the same day. This variation is associated with a reduction in vagal parasympathetic tone to the heart and should be taken into account in the assessment of patients with angina and in particular when comparing responses to treatment.

Effects of calcium channel blocking agents on reperfusion arrhythmias

The effect of the calcium antagonists nifedipine (NF) and diltiazem (DT) on reperfusion after release of circumflex coronary artery (CX) occlusion was studied in open-chest dogs. Dogs were randomized to receive a bolus of 5 micrograms/kg NF (seven dogs), 1 microgram/kg NF (nine dogs), or vehicle (nine dogs). After bolus, high and low dose NF dogs were infused with 1 microgram/kg/min NF. All dogs then underwent 30 minutes CX occlusion followed by reperfusion. Dogs that did not develop ventricular fibrillation (VF) in the first 10 minutes of reperfusion were considered survivors. NF caused a dose-related increase in CX blood flow and decrease in mean arterial pressure (MAP), significant at the higher dose. Reperfusion VF occurred in five of nine low dose NF dogs, five of seven high dose NF dogs, and five of nine controls. Another 21 dogs were randomized to receive a bolus of 0.2 mg/kg DT (11 dogs) or vehicle (10 dogs). Infusion rates (and an additional bolus injection, if necessary) were chosen to produce a 10 to 20 mm Hg drop in MAP. CX occlusion and reperfusion were performed as above. Reperfusion VF occurred in 9 of 11 DT dogs vs 8 of 10 controls. Thus neither nifedipine nor diltiazem enhanced survival during reperfusion of myocardium previously subjected to 30 minutes of ischemia.

The hyperventilation test as a method for developing successful therapy in Prinzmetal's angina

In 10 cases of Prinzmetal's angina in which episodes of myocardial ischemia were easily and reproducibly induced by hyperventilation, this test was performed 111 times, 41 times under control conditions and 70 times during treatment with one or more of the following drugs: phentolamine, isosorbide dinitrate, propranolol, verapamil, nifedipine and amiodarone. Seventeen of 18 negative tests performed under the influence of a long-acting drug coincided with total remission of the patient's anginal episodes when this drug was administered on a short- or long-term basis. No patient died or sustained infarction during a follow-up period of 10.9 months. A negative test was thus a good indication that the clinical response to the corresponding drug would be favorable. The electrocardiographic changes and chest pain provoked by hyperventilation occurred not when alkalosis was greatest (hydrogen ion [pH] change from 7.42 to 7.58, p less than 0.001), but when pH was approaching normal or control values. The onset of electrocardiographic changes occurred an average of 175 seconds after the end of hyperventilation and, in two cases, the time lag was as much as 480 and 705 seconds, respectively. This raises several questions regarding the true mechanism triggering coronary spasm under such conditions. The hyperventilation test appears to be a useful and safe procedure for selecting the best possible drug for long-term treatment of Prinzmetal's angina as well as for comparing the relative efficacy of different drugs.

Efficacy of chronic amiodarone therapy in patients with variant angina pectoris and inhibition of ergonovine coronary constriction

In three patients with vasospastic angina pectoris, chronic amiodarone administered orally at doses of 800 and 1,000 mg/day totally suppressed spontaneous episodes of ischemic chest pain for 8 to 14 months. Before treatment, ergonovine maleate 0.2 to 0.4 mg intravenously provoked chest pain and similar ischemic ECG changes as those occurring spontaneously. During amiodarone treatment ergonovine vasoconstriction was totally or partially inhibited. In addition to calcium-blocking agents, amiodarone is another spasmolytic drug which effects smooth muscle relaxation by different mechanisms and appears to be useful for the chronic treatment and prevention of variant angina. The vasodilator property of amiodarone is achieved by both direct action and noncompetitive alpha receptor antagonism of coronary vasculature.

Nifedipine and propranolol: a beneficial drug interaction

The antianginal effects of two active drugs, nifedipine and propranolol, alone in combination, were compared with those of placebo in a double-blind clinical trial that included 16 patients with chronic stable angina triggered by exertion. A low dose and a high dose of the active drugs were used (nifedipine, 30 and 60 mg/day; propranolol, 240 and 280 mg/day). Precordial exercise mapping and continuous electrocardiographic recordings were used to assess objective response to therapy, and the patients were asked to keep a diary of episodes of chest pain and consumption of nitroglycerin tablets for subjective appraisal. Both frequency of chest pain and nitroglycerin consumption were significantly reduced by each of the active drugs when compared with placebo, and the combination of nifedipine and propranolol added significantly to the effectiveness. Reductions in area of ischemia and number of episodes of ST segment depression on 48-hour ambulatory electrocardiographic monitoring corroborated the efficacy of each active treatment with respect to placebo. Nearly 60 percent of all episodes of ST segment depression were painless and responded to the active treatment in the same manner as did the episodes associated with chest pain. Side effects were mild and all treatments were well tolerated. The objective methods used allowed for clear-cut differentiation of treatment effects with the various regimens. Although the two drugs alone were significantly more effective than placebo, their combination provided an even greater improvement (p less than 0.005), and therefore it appears to be a safe and effective form of treatment for chronic stable angina.

Respiratory alkalemia during exercise reduces angina threshold

The effect of hyperventilation-induced alkalemia on angina threshold was evaluated in nine subjects who had a consistent pattern of chest pain and ST segment depression during exercise. For this study, the subjects performed graded bicycle exercise to angina during normal breathing and during hyperventilation. The maximum workload achieved was not significantly different between normal breathing and hyperventilation exercise. However, in five subjects who had arterial alkalemia during hyperventilation exercise (mean pH = 7.52), the heart rate X blood pressure product (HR X BP) at angina was 224 X 10(2) compared with 240 X 10(2) during normal breathing exercise (P less than 0.05). Four subjects appeared to hyperventilate, but were not alkalemic (mean pH = 7.40). Their HR X BP at angina was not significantly different between the two exercise periods (288 X 10(2) vs 284 X 10(2). In conclusion, the threshold for angina during exercise fell in the five patients in whom hyperventilation caused alkalemia. This finding suggests that the alkalemia interfered with myocardial oxygen supply.

Effects of respiratory alkalosis on coronary vascular dynamics and myocardial energetics in patients with coronary artery disease

To determine if respiratory alkalosis produces hemodynamically significant coronary vasoconstriction in coronary artery disease (CAD), we studied the effects of hyperventilation on coronary sinus blood flow (CSBF), myocardial O2 uptake, and lactate extraction in 13 CAD patients. No patient developed chest pain or ischemic ECG changes during hyperventilation. Hyperventilation increased pressure-rate product (myocardial O2 consumption index, MVO2) minimally did not change global CSBF, coronary vascular resistance or lactate extraction. However, hyperventilation increased global myocardial O2 uptake from 14.5 plus or minus 3.2 to 18.7 plus or minus 17.2 ml/min (p less than 0.01) principally due to increased myocardial O2 extraction (65.0 plus or minus 7.4 to 71.6 plus or minus 6.2%, p less than 0.01). The increased pressure-rate product was not sufficient to account for increased myocardial O2 uptake. We conclude that respiratory alkalosis increases myocardial O2 extraction but does not produce hemodynamically significant coronary vasoconstriction in CAD patients.

Alkalosis-induced coronary vasoconstriction: effects of calcium, diltiazem, nitroglycerin, and propranolol

We examined the effects of changes in pH, Ca2+ concentration, diltiazem, nitroglycerin, and propranolol on the vascular tone of the isolated rabbit coronary artery. Stepwise increase in pH of the bath fluid caused pH-dependent increased vascular tone. Increase in Ca2+ concentration of the bath fluid also resulted in increased vascular tone, while removal of Ca2+ abolished the high pH-induced elevated vascular tone. Diltiazem and nitroglycerin suppressed the high pH-induced increased vascular tone. Propranolol in high concentrations exhibited a direct inhibitory effect on the high pH-induced increased vascular tone. We conclude that high pH induces coronary vasoconstriction principally by increasing transmembrane influx of Ca2+ and that diltiazem and nitroglycerin suppress this action.

Role of calcium antagonists in cardiovascular therapy

The development of drugs which selectively block the "slow" channels by which calcium enters the cell (calcium antagonists) has provided valuable information about the role of transmembrane calcium exchange in man and has offered new therapeutic approaches. The principal effect on the cardiovascular system is relaxation of vascular smooth muscle but some of these drugs also have electrophysiological effects, especially slowing of conduction in the atrioventricular node; verapamil is the agent of choice in supraventricular tachycardia. Significant myocardial depression does not usually occur with doses used clinically. The calcium antagonists have specific value in variant angina. By causing peripheral vasodilatation they are also effective hypotensive agents and do not cause reflex tachycardia in chronic use. Their value in hypertrophic cardiomyopathy and in the protection of ischaemic myocardium remains to be proven.

Effect of diltiazem in patients with variant angina: a randomized double-blind trial

Effects of diltiazem of frequency of angina and nitroglycerin (NTG) consumption were studied in 12 patients with variant angina (rest pain with ST elevation). Either diltiazem in two dosage schedules (120 mg/day and 240 mg/day), or placebo was administered in a randomized double-blind program over 10 weeks. Significant decreases in angina frequency and TNG consumption were observed when diltiazem treatment periods were compared to placebo periods. Furthermore, when placebo periods following diltiazem were compared to placebo periods following placebo, significant "carry-over" effect with respect to reduced angina frequency was observed. No patient had an increase in angina frequency or TNG consumption on diltiazem compared to placebo. No "rebound effects" or changes in blood pressure or heart rate were observed. One patient complained of dry mouth on diltiazem. These findings, although in a limited number of patients, suggest that diltiazem is effective in decreasing angina frequency and TNG consumption in patients with variant angina. These encouraging results warrant evaluation of diltiazem in a larger patient population over a longer time period.

S-T segment elevation and coronary spasm in response to exercise

The prevalence rate of exercise- S-T segment elevation of 0.1 mV or greater in symptomatic patients is 3.0 to 6.5 percent in most studies. S-T segment elevation is associated with a more severe degree of myocardial ischemia than depression and frequently implies a high grade coronary stenosis in the vessel that supplies the site of ischemia. Leads V4 to V6 and bipolar lead CM5 have been found to be relatively insensitive in detecting exercise-induced S-T segment elevation. The pathogenesis of S-T segment elevation is different in three clinical patient subsets reviewed. In patients afer infarction, the largest of the three subgroups, exercise-induced S-T segment elevation usually appears in leads with Q waves, is more common after anterior myocardial infarction and implies underlying akinetic of dyskinetic wall motion. Of patients with variant angina, 10 to 30 percent have during exercise S-T segment elevation that is most likely provoked by coronary arterial spasm. The natural history of variant angina is cyclic, and clinical observations and laboratory findings are dependent on particular phases in the disease process and treatment. Finally, 0.2 to 1.7 percent of symptomatic patients without infarction or variant angina have exercise-induced S-T segment elevation. Although most of the latter have fixed high grade coronary arterial stenoses at angiography, the exact pathogenetic mechanism of S-T segment shift in this patient group is not yet fully understood.

Coronary-artery spasm immediately after myocardial revascularization: recognition and management

We investigated coronary-artery spasm in six patents who had had unexpected hemodynamic collapse within two hours after cardiopulmonary bypass for myocardial revascularization. All six had profound hypotension and recurrent ST-segment elevation in electrocardiographic Leads II, III, and aVF. All had either normal or noncritical luminal irregularities of dominant right coronary arteries and more than 75 per cent occlusions in the left coronary circulation. Right-coronary-artery spasm, which was reversed after intracoronary nitroglycerin, was demonstrated angiographically in one patient; a patent right coronary artery was found at autopsy in another patient. Three patients died despite large intravenous doses of nitroglycerin. Two patients who had been unresponsive to intravenous nitroglycerin recovered after direct infusion of nitroglycerin into the right coronary artery. Coronary-artery spasm immediately after myocardial revascularization may cause circulatory collapse and death; although the spasm may be refractory to usual therapy, it may respond to intracoronary nitroglycerin.

Spontaneous remission in variant angina

Four cases of variant angina are reported, in which total remission of anginal pain was documented during a follow-up of seven months, four years, five years, and 15 years, respectively. During this relatively long follow-up, the clinical course of the disease was apparently benign. The possibility of spontaneously and complete recovery may be postulated. The natural history of relatively benign forms a variant angina is poorly known and understood.

Synergistic relation between vasoconstriction and fixed epicardial vessel stenosis in coronary artery disease

The clinically important hemodynamic consequences of epicardial coronary artery vasoconstriction were examined in the presence of stenosis of major vessels. For this purpose, a special isolated canine circumflex coronary artery preparation was used to provide elimination of reflex, humoral, and distal coronary vasculature resistance influences. Without stenosis, active vasoconstriction induced by either phenylephrine (10-3 M), angiotensin (10-5 M), or acetylcholine (10-5 M) had no effect on flow through the circumflex artery. Coronary arterial stenosis was created by intraluminal obstruction, which itself produced only insignificant effect on vessel flow. When the vasoconstrictor agent stimulation was superimposed on the fixed underlying vascular stenosis, there occurred dose-dependent marked flow decreases through the partially obstructed vessel accompanied by major trans-stenotic pressure gradient increases. Phenylephrine, angiotensin, and acetylcholine separately caused significant (54%, 59%, and 46%) flow decreases with 48, 54 and 50 mm Hg pressure gradient increases respectively. This study demonstrates that vasoconstriction and stenosis act synergistically to reduce flow through obstructed major vessels in coronary artery disease.

Comparison of coronary arteriographic findings during angina pectoris associated with S-T elevation or depression

Coronary arteriographic findings during an attack of angina pectoris associated with S-T segment elevation and angina associated with S-T depression were compared in 54 patients. Thirty-eight attacks with S-T segment elevation included 2 that were spontaneous, 6 induced by methacholine, 4 by epinephrine with or without propranolol, 9 by arm exercise, 5 by hyperventilation with or without Tris-buffer infusion and 12 by ergonovine maleate. Twenty-nine of the 38 attacks were associated with total occlusion, 8 with subtotal occlusion and 1 with diffuse narrowing of a major coronary artery caused by spasm. Twenty-six attacks with S-T segment depression included 3 induced by methacholine, 13 by arm exercise, 3 by hyperventilation with or without Tris-buffer infusion and 7 by ergonovine maleate. Eight of the 26 attacks were associated with subtotal occlusion and 9 with diffuse narrowing of a major coronary artery caused by spasm; 3 attacks were associated with total occlusion of a major coronary artery well supplied with collateral vessels and 2 with total occlusion of a small coronary branch caused by spasm. Four attacks were associated not with spasm but with fixed subtotal occlusion of a major coronary artery (3 attacks) or total occlusion of a major coronary artery receiving collateral vessels (1 attack). Only 2 of the 31 patients with S-T segment elevation had collateral vessels compared with 8 of the 16 patients with S-T segment depression (p less than 0.001). It is concluded that angina pectoris associated with S-T segment elevation usually indicates more severe myocardial ischemia than angina associated with S-T segment depression.

Prinzmetal's variant angina

A series of 12 consecutive patients with Prinzmetal's variant angina is presented. There was a preponderance of males (eight/12) and individuals less than 60 years of age (nine/12). Delay in diagnosis was frequent, primarily due to difficulty in achieving a proper 12 lead ECG recording of the attack which often occurred late at night or in the early morning, subsiding within minutes. In some cases, moreover, ST-depression was observed in the ECG monitoring lead as a reciprocal manifestation of subepicardial ischaemia or due to incorrect polarity in the monitoring lead. The incidence of serious arrhythmias, AV-block and ventricular tachycardia was high (eight/12); two patients had to be DC-converted. Coronary arteriography revealed a spectrum from normal or nearly normal coronary arteries to single vessel disease. Nitroglycerin was well suited for treatment of acute attacks. Long-term treatment with calcium antagonists was effective and without serious side-effects. The follow-up time was from 8 months to 5 years (mean 2 years). It is concluded that Prinzmetal's variant angina as such is a rare disease, but that coronary artery spasm is most likely an important contributory factor in the clinical manifestations of coronary artery disease: arrhythmias, sudden death and myocardial infarction.

Comparative pharmacology of calcium antagonists: nifedipine, verapamil and diltiazem

Calcium antagonists (slow channel blocking agents) are a very heterogeneous group of agents with dissimilar structural, electrophysiologic and pharmacologic properties. Nifedipine is a potent, long-acting vasodilator that has proved highly efficacious in relieving anginal symptoms caused by coronary vasospasm. In vivo, it exerts no myocardial depressant effects and has no antiarrhythmic properties. Treatment with nifedipine can safely be combined with administration of a beta receptor blocking agent. VErapamil prolongs atrioventricular (A-V) conduction (A-H interval) in a dose-dependent manner. It is the drug of choice for the treatment of reentrant supraventricular arrhythmias, irrespective of whether reentry occurs within the A-V node or through an accessory pathway (the Wolff-Parkinson-White syndrome). Verapamil is only moderately effective as an antianginal agent. Diltiazem is efficacious for the treatment of angiospastic angina, but its value as an antiarrhythmic agent remains to be delineated.

Efficacy of diltiazem for control of symptoms of coronary arterial spasm

To evaluate the efficacy of the calcium antagonist diltiazem for therapy of active coronary arterial spasm, 13 patients with clinical variant angina attributed to documented coronary arterial spasm completed a prospective randomized double-blind crossover trial of diltiazem (120 and 240 mg/day) versus placebo. Response was assessed with the diary technique measuring frequency of angina, consumption of nitroglycerin and percent of pain-free days. When 120 mg of diltiazem/day was compared with the paired placebo period there was a significant increase in percent of pain-free days (from 43 to 71 percent [p = 0.03]), but no significant decrease in frequency of angina (p = 0.06) or consumption of nitroglycerin (p = 0.32). When 240 mg of diltiazem/day was compared with the paired placebo period there was a significant increase in percent of pain-free days (from 50 to 79 percent [p = 0.03]) and a significant decrease in both frequency of angina (from 1.6 to 0.4 episodes/day [p = 0.03]) and consumption of nitroglycerin (from 1.3 to 0.4/day [p = 0.01]). Diltiazem was found to be a highly effective drug for control of symptoms of active coronary arterial spasm, without side effects and with excellent patient tolerance.

The effects of vasoconstriction on experimental coronary artery stenosis

In summary, we have examined the response to arterial vasoconstriction in an in vitro coronary artery preparation. Without a preexisting stenosis, arterial vasoconstriction had minimal hemodynamic effects. Similarly, with a stenosis created by a circumferential snare, arterial vasoconstriction had minimal hemodynamic effects. In striking contrast, with a stenosis created by intraluminal obstruction, arterial vasoconstriction dramatically increased the hemodyamic severity of the stenosis. The use of an intraluminal obstruction provides a useful animal model for examining hemodynamics in coronary artery disease and had provided some insight into the effects of vasoconstriction on coronary artery hemodynamics. Obviously, this is an experimental study, and care must be taken in extrapolating these results to diseased human coronary arteries.

Ergonovine testing in a coronary care unit

This study describes the results of ergonovine testing in 100 consecutive patients who underwent this procedure in a coronary care unit. All patients had recently undergone coronary arteriography. A bolus injection of ergonovine was administered at 5 minute intervals in the following doses (mg): 0.0125, 0.025, 0.05, 0.1, 0.2, 0.3 and 0.4. The criterion for a positive test was the appearance of S-T elevation greater than 1 mm. The test was positive in all 17 patients known to have variant angina and in 18 (40 percent) of 45 patients who had a history of chest pain judged strongly suggestive of variant angina but who had no electrocardiogram recorded during pain. Of 38 patients with a history of chest pain classified as not entirely typical of variant angina, only 1 (2.6 percent) had a positive test. Of the 64 patients with a negative ergonovine test, 47 had chest pain and 25 had nausea but none had more serious complications. Ventricular arrhythmia accompanied S-T elevation in 18 of the 36 patients with a positive test but occurred in only 4 of the 64 with a negative test (p < 0.0005). No patient needed treatment with antiarrhythmic drugs. Four of the 36 patients with a positive test had serious complications: severe transient hypotension (2 patients), recurrent episodes of angina with S-T elevation (1 patient) and a subendocardial infarction (1 patient). Thus, ergonovine testing is useful in patients with a typical clinical history of variant angina but without an electrocardiogram recorded during pain. In this study, a small but definite incidence of serious complications occurred during a positive test.

Variant angina--correlation of clinical, electrocardiographic and angiographic features: results of medical and surgical management

Angiographic coronary artery disease (CAD) was correlated with clinical features, electrocardiographic (ECG) findings and the results of medical management or aortocoronary bypass in 42 patients with angina at rest associated with transient ST segment elevation (variant angina). Patients were divided into three sub-sets based on the coronary arteriographic findings. On the basis of greater than 75% luminal diameter narrowing, 28 patients had multiple vessel, ten had single vessel and four had minimal (less than 50% narrowing) CAD. The angiographic sub-sets did not differ significantly in age, sex, coronary risk factors, time from onset of rest pain to coronary angiography, or in the presence of arrhythmias during ischaemic episodes. Patients with multiple vessel CAD more commonly had prior coronary events (P less than 0.01), an abnormal baseline ECG (P less than 0.05) or both (P less than 0.001). These features did not distinguish patients with single vessel from those with minimal CAD. ST elevation in the inferior leads during episodes of myocardial ischaemia was more common (P less than 0.005) in patients with minimal CAD. Twenty--four patients with multiple vessel and six with single vessel CAD underwent aortocoronary by-pass surgery and relief of variant angina was achieved in all 25 long-term survivors during an average follow-up period of 36 months. Twelve patients (four of each subset) were treated medically. Among those with multiple vessel CAD, the small medically treated numbers precluded valid comparison of medical and surgical results. Patients with single vessel CAD followed for an average period of 17 months compared unfavourably with the operated group. Calcium antagonists with the operated group. Calcium antagonists or nitrates controlled variant angina in patients with minimal CAD followed for an average of 27 months.

Relation of coronary arterial spasm to sites of organic stenosis

Among 63 patients with Prinzmetal's variant angina, coronary arterial spasm responsible for attacks of variant angina was documented arteriographically in 9 patients. In each observed episode (11 attacks in nine patients), coronary spasm producing myocardial ischemia occurred at and was superimposed on a site of preexisting organic stenosis. Measurements of normal portions of "spastic" and "nonspastic" vessels suggested a generalized uniform constriction of all major coronary arteries during attacks, with "spasm" limited to the site of an organic lesion in most cases. In two cases the magnitude of constriction in all vessels was consistent with generalized coronary hypercontractility or spasm. Among 104 patients with organic coronary artery disease and documented single vessel coronary spasm (foregoing 9 patients combined with 95 others from published reports), there were 70 patients with essentially single vessel organic coronary disease in 90 percent of whom the spasm involved the diseased vessel. Of 60 cases abstracted from the literature in which the relation of coronary spasm to the site of organic disease was described, 88 percent had the spasm causing ischemia localized to the site of an organic lesion. Hypotheses attempting to describe the pathophysiologic aspects of coronary spasm in variant angina must account for the intimate association of spasm with sites of organic stenosis in the majority of cases.

Pathophysiology and treatment of coronary arterial spasm

Spasm of a large coronary artery occurs most often from midnight to early morning and least often in the afternoon, due to the circadian variation of the tone of the large coronary artery in most patients with variant angina. Alpha adrenergic stimulation induces coronary spasm most easily in the early morning and least easily in the afternoon. Coronary spasm is due to strong contraction of coronary vascular smooth muscle cells which is triggered by an increase of intracellular calcium ions; hyperventilation plus TRIS-buffer infusion induces coronary spasm by decreasing hydrogen ions which antagonize the action of calcium ions. Administration of nitroglycerin promptly relieves the acute attack of coronary spasm, and calcium antagonists such as diltiazem, nifedipine and verapamil, which block the entry of calcium ions into coronary vascular smooth muscle cells and dilate large coronary arteries, prevent the occurrence of coronary spasm.

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.

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.

Refractory variant angina controlled with combined drug therapy in a patient with a single coronary artery

A young man with a single left coronary artery and refractory variant angina is described. Spontaneous coronary artery spasm developed during coronary arteriography at the site of a 50% fixed left anterior descending coronary artery stenosis. Frequent episodes of rest angina with transient ST segment elevation persisted in hospital in spite of treatment with three different calcium antagonist drugs. Symptoms disappeared only when the combination of nifedipine, diltiazem, isosorbide dinitrate, and nitroglycerin ointment were given. Ergonovine testing was used to objectively assess the response to treatment.

The provocation of coronary artery spasm

On the basis of the overall experience, the provocation of coronary artery spasm with ergonovine is thought to be a highly sensitive and specific test for coronary artery spasm in Prinzmetal's variant angina. In spite of occasional complications, in experienced hands the procedure is considered to be safe. The challenge remains to determine the value of this and other provocative interventions in assessing the role of spasm in other aspects of ischemic heart disease, particularly in patients with critical atherosclerotic lesions.

Nifedipine therapy for refractory coronary arterial spasm

Nifedipine was evaluated in the management of eight patients with intractable coronary arterial spasm. All had Prinzmetal's variant angina, normal or mildly abnormal coronary arteriograms, and a positive ergonovine maleate provocative test. Anginal attacks occurred at least three times a week in all patients during isosorbide dinitrate therapy. All patients had a decrease in frequency of ischemic attacks with nifedipine. Seven patients underwent repeat Holter monitor evaluation, which confirmed the absence of ischemic changes while they were taking nifedipine. When nifedipine dosage was decreased.or therapy discontinued in six patients, all experienced a recurrence of anginal attacks. Two patients had minor side effects, which required a decrease in the dose of nifedipine. Nifedipine was well tolerated, and no major complications occurred with its use. Nifedipine appears to be effective in the management of patients with symptomatic coronary arterial spasm and normal or mildly abnormal coronary arteriograms. Our data justify further investigation of nifedipine for treatment of such patients.

Nifedipine in the treatment of Prinzmetal's (variant) angina

The clinical response to therapy with the calcium-blocking agent nifedipine was assessed in 12 patients with variant angina pectoris who were 44 to 67 years old. Five patients had vasospasm of the left anterior descending coronary artery, and seven had spasm of a dominant right coronary artery. Before nifedipine therapy, the frequency of anginal attacks per 24 hour period ranged from 1 to 12, with ventricular tachycardia accompanying ischemic episodes in 7 of 12 patients and high grade atrioventricular block occurring in 2 patients. After therapy with nifedipine, 11 of 12 patients had initial relief of symptoms, and 7 of the 11 had long-term relief. Withdrawal of nifedipine led to recurrence of angina on six occasions in four patients. Provocative testing in the cardiac catheterization laboratory by means of the cold pressor test in one patient and ergonovine maleate in another before and after nifedipine administration showed that this agent can block both alpha adrenergic- and regonovine-induced vasospasm. Nifedipine may have a significant role in the therapy of angina caused by coronary spasm.

Variant angina pectoris: investigation of indexes of sympathetic nervous system function

One thousand forty-five spontaneous episodes of S-T segment elevation were observed in three patients over a total of 72 days of continuous electrocardiographic monitoring. Eighty-nine percent of episodes were asymptomatic; chest pain tended to occur with episodes longer than 3 minutes, and ventricular ectopy occurred almost exclusively with symptomatic episodes. Nitroglycerin regularly relieved angina or S-T elevation, or both. Plasma and urinary catecholamines and their metabolites were normal. Episodes of variant angina were not associated with a generalized increase in sympathetic outflow because serum catecholamine levels at the onset and termination of the S-T abnormalities were not elevated. Controlled trials of propranolol showed no significant beneficial effect. Propranolol significantly increased the length of episodes of S-T elevation in one patient, increasing ventricular irritability. The overall course of variant angina was quite variable, with spontaneous and long-lasting remissions, necessitating cautions interpretation of clinical trials.

Coronary artery spasm: its role in the pathogenesis of myocardial ischemia

The role of coronary artery spasm in the production of myocardial ischemia has recently become the focus of increased attention. This phenomenon is now well established as a causative mechanism underlying the resting chest pain attacks in Prinzmetal's variant angina. There is also evidence that coronary spasm may play a more significant role in the broad spectrum of ischemic heart disease than can be documented by current techniques. The autonomous nervous system constitutes a major element in the pathophysiology of spasm. Coronary arteriography, in spite of important limitations, remains the only technique for final documentation of this phenomenon, but radionuclide scintigraphy appears to be promising. Nitroglycerin is effective for the relief of the acute attack, while long acting nitrates and the calcium antagonists: nifedipine, perhexiline and verapamil are useful in the prevention of recurrences.

Coronary hemodynamic and myocardial metabolic alterations accompanying coronary spasm

Arterial pressure, coronary sinus blood flow with the thermodilution technique and calculated coronary vascular resistance were measured and coronary arteriography performed at rest and after the administration of ergonovine in 14 patients with atypical chest pain (group 1) and 6 patients with variant angina (group II). Mild diffuse narrowing of the left coronary bed in group I was not accompanied by S-T segment shifts, and coronary vascular resistance did not change significantly. In contrast, severe focal spasm (greater than 90 percent narrowing) of the left anterior descending coronary artery in group II patients was accompanied by S-T elevation and a marked overall increase in coronary vascular resistance (from 0.65 +/- 0.07 to 1.14 +/- 0.10 mm Hg/ml per min) (P less than 0.005). In addition, the myocardial arteriovenous oxygen difference increased and net lactate extraction changed to lactate production in the two patients in group II in whom these measurements were made. Thus, thermodilution coronary sinus blood flow measurement may be a sensitive method for detecting primary increases in coronary vascular resistance due to a high grade focal spasm in the left anterior descending coronary artery.

Exertional angina pectoris caused by coronary arterial spasm: effects of various drugs

In four patients with exertional angina induced by arm exercise, coronary arteriograms taken before, during and after the attack demonstrated that spasm appeared in the large coronary artery supplying the area of myocardium shown to be ischemic in the electrocardiogram during the attack. The spasm disappeared with subsidence of the attack after administration of nitroglycerin. Anginal attacks induced by treadmill exercise were not suppressed by propranolol, 60 mg orally, in two of the four patients. However, such attacks were suppressed in all patients by oral administration of diltiazem (90 mg, four patients) or nifedipine (20 mg, three patients) or intramuscular injection of phentolamine (0.2 mg/kg body weight, three patients). It is concluded that coronary arterial spasm can be induced by exercise and can cause exertional angina in some patients. Diltiazem and nifedipine, calcium antagonistic drugs, prevent spasm.