Prinzmetal's variant angina. Coronary arteriogram and left ventriculogram during angina attack induced by methacholine

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.

Impaired muscarinic endothelium-dependent relaxation and cyclic guanosine 5'-monophosphate formation in atherosclerotic human coronary artery and rabbit aorta

The dependence of vascular relaxation on an intact endothelium and the relationship between relaxation and cyclic GMP accumulation were determined in coronary arteries isolated from cardiac transplantation patients with or without coronary atherosclerosis. In nonatherosclerotic arteries, the endothelium-dependent agent acetylcholine produced concentration-related relaxations. In atherosclerotic arteries, endothelium-dependent relaxations were abolished with acetylcholine, partly suppressed with substance P and histamine, and completely preserved with the ionophore A23187. In these arteries, the endothelium-independent agent nitroglycerin remained fully active. Accumulation of cyclic GMP in atherosclerotic strips was suppressed with acetylcholine but unattenuated with A23187 and nitroglycerin. In aortas from rabbits with diet-induced atherosclerosis, there was likewise an impaired cholinergic relaxation and cyclic GMP accumulation in the presence of preserved responses to A23187 and nitroglycerin. The results demonstrate that impaired cholinergic responses in atherosclerotic arteries reflect a muscarinic defect and not an inability of endothelium to release endothelial factor or smooth muscle to respond to it.

Regulation of large coronary arteries

The majority of studies on the control of coronary artery vasoactivity have examined changes in coronary blood flow and coronary vascular resistance, indices that primarily reflect regulation of small arterioles and precapillary vessels. With the emergence of coronary artery vasospasm as a significant cause of angina pectoris, myocardial infarction, and sudden death, the control of large coronary artery caliber has assumed more significance. It is clear that resistance coronary vessels and large coronary arteries differ in response to both pharmacologic and physiologic stimuli. Vasodilation of large coronary arteries may occur by direct action of agents on the arterial smooth muscle or by the indirect action of receptor occupation, changes in blood flow, or liberation of endothelial factors. These indirect factors appear to contribute also to responses to agents that constrict coronary smooth muscle directly or through the autonomic nervous system. Furthermore, the mechanisms responsible for control of large coronary vessels in the normal circulation are likely to be profoundly different from those in the presence of diseased vessels. For example, several factors associated with coronary artery disease--elevated plasma cholesterol levels, endothelial disruption, atherosclerosis, vascular stenosis, and aggregated platelets--all have important actions on the control of large coronary arteries.

Local coronary supersensitivity to diverse vasoconstrictive stimuli in patients with variant angina

It has been shown in different groups of patients with variant angina that coronary spasm can be reproduced by physiologic maneuvers and pharmacologic agents. It is not known, however, to what extent different stimuli can induce spasm in the same patient. To investigate whether coronary arterial spasm results from specific abnormal agonist-receptor interactions or from a local nonspecific coronary supersensitivity to different stimuli, 28 patients with vasospastic angina were submitted to a series of diverse vasoconstrictive stimuli known to provoke coronary spasm. Ergonovine, hyperventilation, handgrip, cold pressor, and exercise-tests, were carried out in all 28 patients. In the last 15 patients histamine was also administered. Spasm was provoked by ergonovine in 96% of patients, by hyperventilation in 54%, by histamine in 47%, by exercise in 46%, and by the cold pressor and handgrip tests in 11% and 7%, respectively. No significant differences were found in the responses to provocative tests of patients with normal coronary arteries or nonsignificant stenoses and those with significant lesions. In the same individual, spasm was induced by at least two vasoconstrictive stimuli, although with a different mechanism of action, in 82% of patients and spasm was induced by three or more stimuli in 39%. Tests were repeated in at least 23 patients and short-term reproducibility paralleled sensitivity. These results suggest that in patients with variant angina, a local nonspecific supersensitivity rather than an abnormal specific agonist-receptor interaction plays a major role in the genesis of coronary arterial spasm.

Induction of coronary artery spasm by acetylcholine in patients with variant angina: possible role of the parasympathetic nervous system in the pathogenesis of coronary artery spasm

We injected acetylcholine (ACh), the neurotransmitter of the parasympathetic nervous system, into the coronary arteries of 28 patients with variant angina. Injection of 10 to 80 micrograms ACh into the coronary artery responsible for the attack induced spasm together with chest pain and ST segment elevation or depression on the electrocardiogram in 30 of the 32 arteries of the 25 of the 27 patients. The injection of 20 to 100 micrograms ACh into the coronary artery not responsible for the attack in 18 patients resulted in various degrees of constriction in most of them, but no spasm in any of them. After intravenous injection of 1.0 to 1.5 mg atropine sulfate, the injection of ACh into the coronary artery responsible for the attack did not induce spasm or attack in any of the nine coronary arteries injected in eight patients. We conclude that the intracoronary injection of ACh induces coronary spasm and attack in patients with variant angina and that the activity of the parasympathetic nervous system may play a role in the pathogenesis of coronary spasm. We also conclude that the intracoronary injection of ACh is a useful test for provocation of coronary spasm.

Paradoxical vasoconstriction induced by acetylcholine in atherosclerotic coronary arteries

Acetylcholine is believed to dilate normal blood vessels by promoting the release of a vasorelaxant substance from the endothelium (endothelium-derived relaxing factor). By contrast, if the endothelium is removed experimentally, acetylcholine constricts blood vessels. We tested the hypothesis that muscarinic cholinergic vasodilation is impaired in coronary atherosclerosis. Graded concentrations of acetylcholine and, for comparison, the nonendothelial-dependent vasodilator nitroglycerin were infused into the left anterior descending artery of eight patients with advanced coronary stenoses (greater than 50 percent narrowing), four subjects with angiographically normal coronary arteries, and six patients with mild coronary atherosclerosis (less than 20 percent narrowing). Vascular responses were evaluated by quantitative angiography. In several segments each of four normal coronary arteries, acetylcholine caused a dose-dependent dilation from a control diameter of 1.94 +/- 0.16 mm to 2.16 +/- 0.15 mm with the maximal acetylcholine dose (P less than 0.01). In contrast, all eight of the arteries with advanced stenoses showed dose-dependent constriction, from 1.05 +/- 0.05 to 0.32 +/- 0.16 mm at the highest concentration of acetylcholine (P less than 0.01), with temporary occlusion in five. Five of six vessels with minimal disease also constricted in response to acetylcholine. All vessels dilated in response to nitroglycerin, however. We conclude that paradoxical vasoconstriction induced by acetylcholine occurs early as well as late in the course of coronary atherosclerosis. Our preliminary findings suggest that the abnormal vascular response to acetylcholine may represent a defect in endothelial vasodilator function, and may be important in the pathogenesis of coronary vasospasm.

Parathyroid hormone in coronary artery disease--results of a prospective study

Parathyroid hormone (PTH) influences the calcium metabolism of many different mammalian cell types; indeed, hypertension due to changes in muscle tone is a frequent symptom of hypercalcemic hyperparathyroidism. In a blind study of 81 patients with various forms of heart disease undergoing coronary angiography, the plasma concentrations of the midcarboxyl regional PTH immunoreactivity were determined. PTH concentrations were elevated in 26 of the 56 patients exhibiting organic coronary artery disease (CAD). The plasma PTH levels were highest in those patients with CAD affecting three vessels and in patients with evidence of myocardial infarction. PTH levels were not influenced by previous drug treatments, and did not correlate to stress hormone levels. We propose that increased PTH levels may be a marker for initiation or potentiation of calcium-dependent changes in vascular smooth muscle behavior inducing coronary functional and anatomic lesions typical of CAD.

Pathogenesis of angina pectoris in patients with one-vessel disease: possible role of dynamic coronary obstruction

We examined the pathogenesis of angina pectoris in 101 patients with one-vessel disease except those with 99% to 100% occlusion. The attacks could not be induced or could not be reproducibly induced by maximal treadmill exercise at the same hour of different days within a week period in 54 (53.5%) of the patients. In the 47 patients whose attacks were reproducibly induced by the exercise, propranolol, 80 mg orally, did not suppress the attacks in 41 (87.2%) of the patients. Diltiazem, 90 mg, and nifedipine, 20 mg given orally, suppressed the attacks completely in 39 (83.0%) of the 47 patients and in 36 (81.8%) of the 44 patients, respectively. Coronary arteriography showed that dynamic obstruction of the artery supplying the area of myocardium represented by ST segment deviation appeared during the attacks and disappeared with subsidence of the attacks in all 55 patients in whom coronary arteriography was done during the attack. We conclude that angina pectoris is usually caused not by increased myocardial oxygen demand but by dynamic coronary obstruction or by a combination of both in most patients with one-vessel disease.

Mechanisms responsible for coronary vasospasm

Studies have been conducted on isolated segments of the left circumflex coronary artery of the dog to gain information on the mechanism or mechanisms of vasospasm. Coronary arteries contain both postjunctional alpha 1- and beta 1-adrenoceptors, and both are accessible to norepinephrine released from the sympathetic nerves. However, owing to the dominance of the beta 1-adrenoceptors, sympathetic stimulation causes relaxation of the vascular smooth muscle. In the primary branches of the circumflex artery, only beta 1-adrenoceptors are present. In patients with spasm of the coronary arteries, blockade of the beta 1-adrenoceptors may aggravate the spasm by permitting the unopposed constrictor action of the sympathetic nerves on the alpha 1-adrenoceptors on these vessels. The blood platelets contain substances, including 5-hydroxytryptamine (serotonin) and thromboxane A2, which can cause constriction of vascular smooth muscle. These substances are released whenever platelets aggregate. The normal endothelium, by forming and releasing prostacyclin, inhibits platelet aggregation. In addition, in response to platelet products, the normal endothelium forms one or more inhibitory substances that cause relaxation of the underlying smooth muscle. Also, if any thrombin is formed, this also causes an endothelium-mediated relaxation of the artery. Patients with coronary artery spasm usually have morphologic changes in the artery at the site of the spasm. Thus, platelets can aggregate at the site and the resultant release of serotonin and thromboxane A2, acting directly on the smooth muscle, causes constriction of the artery. Hypoxia of the myocardium follows and this augments the constriction.

Coronary artery spasm in a denervated orthotopic transplanted human heart

A case of catheter-induced spasm in a 40-year-old male one year after orthotopic cardiac transplantation is presented. The fact that spasm can occur in this setting of total cardiac denervation demonstrates that other factors can play an important part in modifying the status of coronary artery patency.

The heart as a sensory organ

Three groups of receptors in the heart are activated by changes in pressure in the cardiac chambers. Those at the venous-atrial junctions with myelinated vagal afferent nerves indicate changes in heart rate and degree of atrial filling. A second group, present in all the cardiac chambers, served by unmyelinated vagal afferent nerves, signals changes in ventricular preload, afterload and cardiac contractility. A third group, also present in all the cardiac chambers, has both myelinated and unmyelinated afferent nerves that pass to the spinal cord. Their normal function is unknown. Abnormal activation of the cardiac mechanoreceptors during myocardial ischemia may be important in the genesis of life-threatening arrhythmias.

Cholinergic mechanisms in human coronary artery preparations: implications of species differences

Acetylcholine dilates most arteries, including dog coronaries, if the endothelium is intact. The present study has shown only contraction of human coronary arteries to acetylcholine. Both strip and ring preparations of human coronary epicardial vessels, the latter done particularly to protect the intimal surface from unintentional denudation, contracted to acetylcholine at low to high concentrations (6.84 X 10(-9)-2.05 X 10(-5) M). These responses were blocked by atropine (3.45 X 10(-6) M). Acetylcholine contracted the arteries about as much as ergonovine and considerably more than noradrenaline. Field stimulation of coronary artery strips caused a vasoconstriction which was partially antagonized by atropine (3.45 X 10(-6) M). The release of [3H]noradrenaline from superfused coronary artery preparations during field stimulation was inhibited by methacholine (6.24 X 10(-6) M), a stable muscarinic analogue of acetylcholine. Dog coronary arteries relaxed to acetylcholine but not if the endothelium was intentionally denuded, in which case there was either no response at all or a weak relaxation. Coronary arteries of sheep, pig and cattle always contracted to acetylcholine, and those of monkey contracted in two out of three responsive preparations. Histological examination of the intimal surface of human coronary vascular segments confirmed the presence of an intact endothelial cell layer. Rabbit aorta gave dilator responses to acetylcholine even after being left in the animal for as long after death as the human arteries had been; they did not give dilator responses after the endothelium was rubbed off. It is concluded that cholinergic vasoconstriction of coronary arteries occurs in humans, though not in the dog, and is probably important in some cases of coronary artery spasm.

Spasm of the coronary arteries: causes and consequences (the scientist's viewpoint)

Both beta 1- and alpha 1-adrenoceptors are present on canine coronary arteries, and they are accessible to norepinephrine released from the sympathetic nerves. Under normal conditions, these arteries relax because of the predominance of the beta 1-adrenoceptors, whereas constriction prevails in the presence of beta 1-adrenoceptor antagonists. The coronary arteries also have cholinergic nerves. When activated, these nerves release acetylcholine, which acts on muscarinic receptors on the sympathetic nerve terminals to reduce the output of norepinephrine and thereby lessen the relaxation mediated by beta 1-adrenoceptors. Thus, muscarinic agonists can precipitate coronary artery spasm. If the smooth muscle cells of the coronary arteries become hypoxic, their responsiveness to beta-adrenergic stimulation is lost and constrictor responses are exaggerated. Cardiac glycosides prevent the predominance of the beta-adrenergic effects of norepinephrine. Therefore, after treatment with ouabain, release of norepinephrine from the sympathetic nerves leads not to relaxation but to further contraction of coronary arteries. The endothelium of the coronary arteries inhibits platelet aggregation by the formation and release of prostacyclin, and it reacts to platelet products by causing relaxation of the underlying smooth muscle. In addition, if any thrombin is formed, it also causes endothelium-mediated relaxation. If the endothelium is damaged, these protective mechanisms are lost. Patients with coronary artery spasm usually have morphologic changes in the artery at the site of the spasm. Platelets can aggregate at this site and release vasoactive substances, which--aided by formation of thrombin--cause contraction. Thus, the blood supply to the myocardium is reduced; the ensuing hypoxia augments the constriction. Acute myocardial ischemia caused by coronary vasospasm may precipitate acute cardiac rhythm disturbances and sudden death by ventricular tachycardia or fibrillation.

Coronary angiography during exercise-induced angina with ECG changes

Coronary angiography was performed at rest and during bicycle exercise immediately after the onset of angina and significant ST segment elevation or depression in the ECG. Of 11 patients, six showed significant reduction of coronary lumen diameter at the site of organic stenosis; mean values of stenosis (range) before and during exercise were 55% (25% to 88%) and 98% (89% to 100%), respectively. Five patients did not have any diameter change of the organic lesion; mean values of stenosis (range) before and during exercise were 84% (74% to 89%) and 84% (73% to 92%), respectively. Excluding the areas of these stenoses, diameters of left main coronary artery, proximal, middle, and distal left anterior descending, circumflex, and right coronary artery segments were measured before and during exercise. Diameter in each coronary artery segment during exercise was not significantly changed from that before exercise, both in the groups with and without diameter reduction. Exercise provoked a localized worsening of coronary artery stenosis without changing the diameter in the remaining artery. These findings suggest that the worsening of stenosis might be caused by a regional abnormality of the coronary artery that is not necessarily related to the degree of organic stenosis.

Receptor mechanisms in the human epicardial coronary artery. Heterogeneous pharmacological response to histamine and carbachol

We studied isolated ring segments from a number of sites along the course of epicardial coronary arteries from 24 human hearts in order to characterize regional responsiveness to vasoactive agents. Concentration-response curves revealed heightened sensitivity to histamine in the proximal portion of the coronary arteries, and increased sensitivity to carbachol in the distal portion of these same vessels. In contrast, the response to stimulation by calcium or phenylephrine was uniform throughout the length of the vessels examined. These data suggest that regional variations in agonist response reflect heterogeneity in receptor populations along the course of the human epicardial coronary artery.

Abnormal heart rate response to exercise in vasospastic angina: pathophysiologic mechanism in the provocation of coronary spasm

To examine the alteration in control function of the heart, which may account for the pathophysiologic condition precipitating coronary arterial spasm, the dynamic property of heart rate response to exercise in vasospastic angina was evaluated by using our previously developed frequency analytic procedure. We studied 21 patients with vasospastic angina, divided into two groups (active angina and inactive angina) and 12 normal control subjects. When compared with the transfer function of the heart rate control system in normal control subjects, the transfer function in patients with active vasospastic angina showed moderately lower gain, especially in the middle frequency range, and significantly delayed phase angle over the whole frequency range, especially in the middle and high frequency ranges. These abnormalities were not observed in inactive vasospastic angina. The present exercise test to detect abnormal heart rate control can feasibly be used in the detection and management of vasospastic angina.

Calcium channel blockers: an intraoperative and postoperative trial in women

This study analyzes the effects of intraoperative and postoperative calcium channel blockers on myocardial protection, postoperative arrhythmias, perioperative infarctions, and survival. Thirty-nine women undergoing consecutive coronary artery bypass operations were placed either in a control group (N = 23), in which standard cold potassium cardioplegia was used, or in a verapamil-nifedipine group (N = 16), in which verapamil (1 mg per liter) was added to the standard cardioplegic solution and nifedipine was instituted postoperatively. The verapamil-nifedipine group showed a significant reduction in postoperative levels of creatine phosphokinase (p less than 0.05). Levels of aspartate aminotransferase were also reduced (74 IU/L) compared with those for the control group (114 IU/L). In the control group, there were 3 early deaths secondary to abrupt ventricular fibrillation, but no patient in the verapamil-nifedipine group died or had serious early ventricular arrhythmias. Late hemodynamic variables were similar in both groups. We conclude that calcium channel blockers enhance myocardial protection during ischemic arrest and may diminish the incidence of fatal early postoperative ventricular arrhythmias in women undergoing coronary revascularization.

Clinical characteristics and prognosis of patients with postinfarction angina caused by coronary artery spasm

Clinical features and the course of 15 patients with postinfarction angina caused by coronary artery spasm are described. Episodes of postinfarction angina in the patients recurred at rest in the early recovery phase and were accompanied by transient ST-segment elevation. The area where ST-segment elevations were demonstrated on a 12-lead ECG always included the leads with newly developed abnormal Q waves. Pain resolved spontaneously or after sublingual nitroglycerin in several minutes. Holter ECGs during a 24-h period demonstrated frequent episodes of ST-segment elevation that were not always associated with chest pain. Treatment with calcium antagonist and/or nitrates effectively suppressed angina, and only one patient developed reinfarction. The patient's subjective symptoms were abolished by diltiazem and isosorbide dinitrate. A Holter ECG of the patient revealed silent ST-segment elevations before and after the reinfarction and an increase of the drugs completely suppressed the recurrence of silent ischemic ECG changes. Coronary arteriograms were obtained from 8 patients, which demonstrated more than 75% segmental stenosis on one coronary artery in 5 patients and no significant obstruction in the remaining 3. All patients performed a treadmill exercise stress test before discharge and most demonstrated excellent tolerance. All patients experienced no form of chest pain for an average of 25 months follow-up under medication. We conclude that among patients with postinfarction angina, those cases caused by coronary artery spasm have a relatively good prognosis.

Variant angina induced by alcohol ingestion

We gave alcohol to 15 patients with variant angina to induce the attacks at the hospital. Anginal attacks were repeatedly induced in seven of them. Although the time lag between alcohol ingestion and the attacks varied widely among patients, from 1.5 to 12 hours, it was fairly constant in each patient. We carefully examined the histories of 101 patients with variant angina to become familiar with the relationship between alcohol ingestion and the attacks of angina. Seventy-one patients took alcohol in their daily lives. Nineteen of the 71 patients (26.8%) who took alcohol had a definite relationship between alcohol ingestion and the attacks. We conclude that alcohol induces anginal attacks or coronary artery spasm in not a small number of patients with variant angina.

Coronary arteriography and left ventriculography during spontaneous and exercise-induced ST segment elevation in patients with variant angina

The present study is an angiographic demonstration of coronary artery spasm during both spontaneous and exercise-induced angina in three patients with variant angina. In each case, clinical, ECG, coronary angiographic, and left ventriculographic observations were made at rest, during spontaneous angina, and during exercise-induced angina. The character of chest pain was similar during spontaneous and exercise-induced episodes. ST segment elevation was present in the anterior ECG leads during both episodes. The left anterior descending coronary artery became partially or totally obstructed during both types of attacks. When coronary spasm was demonstrated during both types of attacks, left ventriculography disclosed akinetic or dyskinetic wall motion in the area supplied by the involved artery. In those patients with reproducible exercise-induced ST segment elevation and chest pain, thallium-201 scintigraphy showed areas of reversible anteroseptal hypoperfusion. Thus in selected patients exercise-induced attacks of angina were similar to spontaneous episodes.

Natural history of pure coronary artery spasm in patients treated medically

The clinical course of 59 patients with coronary artery spasm and no fixed severe coronary obstruction was analyzed for an average of 5.9 years. The study group consisted of 27 men and 32 women. Angina at rest was the predominant symptom in 93% of the patients. Myocardial infarction occurred in 19% and syncope during angina in 27%. During spontaneous anginal episodes, 64% of the patients showed ST segment elevation, 17% ST segment depression and 15% no electrocardiographic changes. Major arrhythmias during angina occurred in 24% of the patients. Permanent pacemakers were required in 10% of the patients. Stress tests were positive in 32% of the patients. Long-acting nitrate therapy controlled symptoms in only 31%, and calcium antagonist agents controlled symptoms in 83% of the patients unresponsive to nitrates. Spontaneous remission of angina for at least 1 month while receiving no medical treatment occurred in 39% of the patients. Fifteen percent of patients had an indefinite remission with no recurrence of symptoms for at least 2 years. There were no cardiac deaths. The natural history of medically treated patients with pure coronary spasm is characterized by recurrent angina at rest, frequent spontaneous remission, a poor response to long-acting nitrate therapy and a good response to calcium antagonists. Although myocardial infarction and major arrhythmias are common, cardiac mortality is low in medically treated patients.

Clinical studies of patients with coronary spasm

Coronary artery spasm may cause myocardial ischemia in patients without severe coronary atherosclerotic obstruction. Spontaneous rest angina, particularly at night, is the predominant symptom; most patients are smokers. Ergonovine tests have high sensitivity and specificity for the diagnosis of coronary spasm, but should be used when vasospasm is suspected but no electrocardiogram was recorded during spontaneous angina. Arterial constriction measured during ergonovine testing suggests that the arterial hypersensitivity to vasoconstrictors at sites of atherosclerotic lesions is independent of the severity of the lesion. Coronary vasospasm may also be provoked by exercise, possibly through an alpha-adrenergic mechanism. Both spontaneous and exercise-induced attacks of vasospasm are prevented by calcium-antagonist drugs that remain effective during longer-term treatment. The cyclic nature of the condition is demonstrated when successful therapy is discontinued without recurrence of symptoms and may be due to alteration of arterial hypersensitivity.

Cold pressor test and variant angina

A transient complete coronary occlusion due to spasm was induced by the cold pressor test in a 51-year-old man with variant angina. Arteriography before the test revealed a normal left coronary artery and only minor irregularities of the mid-portion of the right coronary artery. Three minutes after cold stimulation, angina pectoris accompanied by ST-segment elevation was observed in lead II ECG. Simultaneous coronary arteriography during the attack showed a complete occlusion of the proximal right coronary artery due to spasm. The anginal attack together with spastic occlusion disappeared after administration of 0.8 mg of nitroglycerin. Thus, the cold pressor test can trigger coronary artery spasm and may even lead to a total occlusion in patients with variant angina. Individuals with variant angina may be subjected to additional risk when exposed to cold temperatures.

Potentiation of coronary vasoconstriction by beta-adrenergic blockade in patients with coronary artery disease

Although beta-adrenergic blocking agents reduce myocardial oxygen consumption and symptoms of myocardial ischemia in patients with coronary artery disease (CAD), propranolol has been reported to exacerbate coronary artery spasm in some patients with variant angina. To determine whether increased coronary vasomotor tone can be induced by beta-adrenergic blockade, we measured the changes in coronary vascular resistance (CVR) during cold pressor testing (CPT) in 15 patients, nine with severe CAD and six with normal left coronary anatomy, before and after i.v. propranolol (0.1 mg/kg). Coronary blood flow was measured by coronary sinus thermodilution. CVR was calculated as mean arterial pressure divided by coronary sinus blood flow. Heart rate was maintained constant at a paced subanginal rate of 95 +/- 5 beats/min. Before propranolol, CPT induced significant increases in coronary vascular resistance in patients with CAD (15.0 +/- 2.2%, p less than 0.02), but no increase in CVR in the normal patients. After propranolol, the CVR change during CPT was augmented for patients with CAD (29 +/- 6%, p less than 0.01) and for the normal population (9 +/- 5%, NS). The potentiated increase in CVR occurred without significant changes in resting CVR or in the magnitude of the hypertensive response to CPT. We conclude that beta-adrenergic blockade with propranolol can potentiate coronary artery vasoconstriction in some patients with CAD, possibly mediated by unopposed alpha-adrenergic vasomotor tone. These changes may be important in patients in whom intense adrenergic stimulation may increase coronary artery tone and adversely influence the balance between myocardial oxygen supply and demand.

Coronary artery spasm in intact dogs induced by potassium and serotonin

Although coronary artery spasm has been implicated as an important cause of myocardial ischemia in humans, an animal model of reversible segmental coronary constriction has not been described. To provoke coronary spasm in open-chest dogs, selected vasoconstricting agents adsorbed to viscous ion exchange gels were applied topically to the surface of epicardial coronary arteries. The procedure provided a sustained localized release of drug, and minimized effects on contiguous myocardium or on the systemic circulation. Segmental arterial constrictor responses were evaluated by sonomicrometry, arteriography, and electromagnetic flow measurements. Potassium evoked sustained constrictions or spasms, and concomitantly reduced flow by -42 +/- 4% (SE; n = 34). Serotonin likewise produced sustained decreases in flow of -22 +/- 6% (SE; n = 5). Other constrictors, including norepinephrine and angiotensin, failed to evoke sustained constrictions. Spasms nearly abolished reactive hyperemic responses elicited by temporary complete occlusion of the artery. Intravenous nitroglycerin and dihydropyridine calcium antagonists promptly relieved the spasms. Scanning electronmicroscopic examination of the intimal surface of arteries undergoing sustained spasm revealed no platelet thrombi. Thus, nonthrombotic, vasodilator-sensitive segmental coronary spasms were elicited by endogenous constrictors which may play a role in regulating flow to ischemic myocardium.

Methacholine provocation of Prinzmetal's variant angina pectoris: a revised perspective

We report 13 patient with unequivocal Prinzmetal's variant angina pectoris as the entire experience with this syndrome during a 7-year period in a single institution. The clinical diagnosis of this relatively uncommon disorder is emphasized. Five patients were given 10 mg of methacholine subcutaneously. Three demonstrated subsequent delayed appearance of chest pain, ECG change, and coronary vasospasm following early appearance of muscarinic effects. Two Prinzmetal patients had no provocation of variant angina following methacholine, though they did experience significantly less blood pressure fall in response to muscarinic provocation. Another 23 subjects with incompletely explained chest pain given methacholine had neither ECG change nor spasm. Methacholine provocation of variant angina need not necessarily implicated a parasympathomimetic mechanism for otherwise spontaneous episodes. Rather, provocation would appear to occur via the customary reflex adrenergic response to drug-induced hypotension. Methacholine is probably safe though unreliable as an agent to be used for spasm provocation.

Postinfarction angina caused by coronary arterial spasm

Recurrent ST-segment elevations in leads where new Q waves developed were repeatedly recorded in six patients during a recovery phase of acute myocardial infarction. Such ST-segment elevations were transient, occurred with or without chest pain, and returned to control levels. No enzymatic changes signifying recurrent myocardial necrosis were found after each episode. Selective coronary cineangiography in one patient demonstrated a mild segmental stenosis in the coronary artery perfusing the infarcted area; this artery became completely occluded after administration of i.v. ergonovine. Administration of calcium antagonists effectively reduced the frequency of postinfarction angina and ST-segment elevations. The clinical features suggest that the postinfarction angina in these patients is produced by coronary arterial spasm and that coronary arterial spasm may cause severe life-threatening dysrhythmias.

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.

Coronary arterial spasm in single coronary artery

A 48-year-old man developed severe chest pain and became unconscious. Coronary cineangiography revealed single coronary artery of the type L2b by Sharbaugh and White. Ergonovine, 0.2 mg i.v., produced coronary arterial spasm in the right coronary artery. This case suggests that coronary arterial spasm might be a cause of sudden death in patients with single coronary artery. However, an association of single coronary artery and coronary arterial spasm might be coincidental.

Histamine provocation of clinical coronary artery spasm: implications concerning pathogenesis of variant angina pectoris

Twelve patients with nonexertional chest pain and nonobstructive fixed coronary disease (less than 50% luminal diameter narrowing) were given histamine to investigate the potential role (coronary artery H1 receptor agonism) of the endogenous agent in producing coronary artery spasm (CAS). Histamine, at intravenous dose of 0.5 to 1.0 microgram/kg/min, provoked CAS in four patients. In six patients neither histamine nor ergonovine provoked spasm, and these patients were considered by chronic follow-up evaluation to have noncardiac etiology for their chest pain syndrome. In one patient CAS was provoked with ergonovine but not by histamine, and one ergonovine-positive patient had an equivocally positive histamine result. Pretreatment with cimetidine (H2 receptor antagonism) was necessary to avoid unpleasant side effects of histamine. Thus these observations indicate that histamine should be included among the specific agents capable of inducing CAS and provide new insight concerning the mechanism(s) causing variant angina pectoris.

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.

Prinzmetal's variant angina induced only by alcohol ingestion

Prinzmetal's variant agina occurred in a 52-year-old man 10-11 h after the ingestion of alcohol, when blood levels of alcohol decreased almost to the zero level. Coronary arteriograms revealed significant narrowing in the left circumflex artery and the left anterior descending artery and minimal wall irregularity in the right coronary artery; however, both exercise and pharmacologic stress tests were negative. A withdrawal from an acute exposure to alcohol was discussed as a possible causative mechanism of the alcohol-induced Prinzmetal's variant angina in this case.

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.

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.

Coronary artery spasm in the denervated transplanted human heart: a clue to underlying mechanisms

The mechanism of coronary artery spasm has been poorly understood but there has been some suggestion that cardiac autonomic innervation may play an important role. We report coronary artery spasm in a 43 year old man two years after he had received a transplant. Provocative pharmacologic testing suggested functional denervation of the patient's heart. Thus, coronary artery spasm can occur in the transplanted, denervated human heart. Autonomic innervation of the heart is not essential in all cases of coronary spasm, and circulating catecholamines and/or metabolic of hormonal products may play an important role.

Thromboxane A2 in vasotonic angina pectoris: evidence from direct measurements and inhibitor trials

Thromboxane A2 (TxA2), an arachidonic acid metabolite causing vasoconstriction and platelet aggregation, is a putative mediator of coronary-artery vasospasm. To determine whether platelet-released TxA2 causes coronary arterial vasospasm, we measured plasma thromboxane B2 (TxB2, the inactive hydration product of TxA2) in the radial-artery and coronary-sinus blood of seven patients and performed therapeutic trials of antiplatelet agents in nine. Although coronary-sinus TxB2 levels rose from the base line approximately fivefold with spontaneous ischemia, samples drawn early in ischemia showed no rise over base-line values. Although a 150 mg dose of aspirin reduced urinary dinor-TxB2 levels by over 75 per cent, it had no effect on the course of the chronic recurrent form of angina pectoris due to vasospasm ("vasotonic angina"). Similarly, indomethacin had no effect on the frequency or duration of ischemia. TxA2 is unlikely to cause vasotonic angina, but it may be released during coronary vasospasm.

Medical therapy of Prinzmetal's variant angina

Medical therapy for Prinzmetal's variant angina has been treatment of the acute attack with sublingual nitroglycerin. Prophylactic therapy has been more difficult, utilizing long-acting vasodilators that are limited because of their short half-life and side effects when therapeutic doses are used. Alpha-adrenergic blockade has been effective in some patients but is frequently associated with intolerable side effects or apparent development of tolerance to the drug. Preliminary experience from a randomized double-blind trial of diltiazem, a new calcium antagonist, has demonstrated a 90% reduction in pain episodes, with many patients becoming pain-free on the 240-mg daily dose. These data and the lack of adverse side effects demonstrate a dramatically effective therapy for patients with coronary artery spasm.

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.

Medical therapy of Prinzmetal's variant angina

Medical therapy for Prinzmetal's variant angina has been treatment of the acute attack with sublingual nitroglycerin. Prophylactic therapy has been more difficult, utilizing long-acting vasodilators that are limited because of their short half-life and side effects when therapeutic doses are used. Alpha-adrenergic blockade has been effective in some patients but is frequently associated with intolerable side effects or apparent development of tolerance to the drug. Preliminary experience from a randomized double-blind trial of diltiazem, a new calcium antagonist, has demonstrated a 90% reduction in pain episodes, with many patients becoming pain-free on the 240-mg daily dose. These data and the lack of adverse side effects demonstrate a dramatically effective therapy for patients with coronary artery spasm.

Pathogenetic mechanisms of angina pectoris: expanding views

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