Coronary artery spasm: demonstration, definition, diagnosis, and consequences

Contraction of isolated porcine coronary arteries is inhibited by high concentrations of propranolol

Isometric tension responses of isolated porcine coronary artery rings were studied in the presence of concentrations of propranolol higher than those necessary to block effects mediated by beta-adrenergic receptors. Propranolol (50-300 microM) inhibited contractions induced by 30 mM KCl and by histamine, norepinephrine, and acetylcholine in a concentration-dependent, noncompetitive fashion. The (+) propranolol isomer and the racemic mixture were equipotent inhibitors of contraction. Propranolol inhibition was partly reversed by increased extracellular Ca++. These effects of propranolol thus appeared to be independent of beta-blockade and could be relevant to some of the drug's observed but still unexplained in vivo actions.

Management of vasospastic angina--role of nicorandil

Clinical and experimental observations have confirmed that an episodic increase in the vasomotor tone of a major coronary artery may play a pathogenetic role not only in "variant angina" but also in other, more common anginal syndromes. In chronic stable angina, dynamic changes of vascular smooth muscle tone at the site of eccentric atheromatous plaques are responsible for "mixed angina." Abnormal coronary vasomotion contributes to myocardial ischemia in acute coronary syndromes as well. Studies have shown that a "primary" reduction of coronary blood flow, usually associated with plaque fissuring and thrombus formation, causes infarction and unstable angina. Abnormal vasoconstriction associated with the release of vasoactive substances by platelets and other constituents of the thrombus can contribute to coronary flow reduction in patients with unstable angina and myocardial infarction. Better understanding of the complex interactions among atherosclerotic coronary obstructions, the vascular smooth muscle, and the vascular endothelium has resulted in novel therapeutic approaches and has stimulated the search for more efficacious and safer coronary vasodilators. Recently interest has focused on vasodilator agents such as nicorandil that influence coronary arterial tone by acting through potassium channel activation. Nicorandil appears to be effective for treatment of vasospastic angina, as suggested by studies in Japan and Europe. In addition to its "antivasospastic" properties, nicorandil dilates coronary artery stenoses in patients with stable angina pectoris.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced insulin response relates to acetylcholine-induced vasoconstriction in vasospastic angina

OBJECTIVES

This study investigated whether insulin response to an oral glucose load correlates to acetylcholine-induced coronary vasoconstriction in subjects with vasospastic angina.

BACKGROUND

It has been suggested that coronary vasospasm is caused by augmented vascular responsiveness possibly exerted by atherosclerosis. Recently, insulin resistance syndrome has been proposed as a major promotor of atherosclerotic disease, potentially enhancing vascular smooth muscular tone.

METHODS

Among subjects with angiographically smooth coronary arteries, we selected 14 subjects with vasospastic angina and 14 age- and gender-matched subjects with atypical chest pain. We compared coronary vasomotor response to acetylcholine infusion, glucose and insulin responses to an oral glucose load (75 g), serum lipid concentrations, obesity, heart rate, blood pressure and smoking habits in both groups.

RESULTS

Fasting serum insulin concentrations and insulin response were higher in subjects with vasospastic angina than in those with atypical chest pain; however, glucose tolerance, obesity, heart rate, blood pressure and smoking habits did not differ between groups. In subjects with vasospastic angina, nearly all coronary segments, except distal segments of the left circumflex coronary artery, were constricted at peak acetylcholine infusion (20 to 100 micrograms), whereas all segments were dilated in subjects with atypical chest pain. Regression analysis for both groups demonstrated a correlation between coronary vasoconstriction and fasting serum insulin concentrations (r = 0.52, p < 0.01), insulin response (r = 0.71, p < 0.001), serum triglyceride concentrations (r = 0.51, p < 0.05) and atherogenic index (r = 0.44, p < 0.05).

CONCLUSIONS

Results show that acetylcholine-induced coronary vasoconstriction in subjects with vasospastic angina correlates with hyperinsulinemia and enhanced insulin response, suggesting insulin resistance syndrome as a feature of vasospastic angina.

Sudden death in the young. Is acute coronary thrombosis the major precipitating factor?

BACKGROUND

Atherosclerotic coronary artery disease, complicated by acute thrombosis, is the usual cause of sudden death in adults. This study addresses the pathology of coronary arteries in sudden death in the young (< or = 35 years old).

METHODS AND RESULTS

Among 200 consecutive cases of sudden death in youth in the Veneto region of Italy, 37 (33 men and 4 women, age 18 to 35 years; mean, 29.4 years) showed obstructive atherosclerotic coronary artery disease in the absence of other cardiac pathological conditions and causes of death. No patient had previous angina pectoris or myocardial infarction. Cardiac arrest occurred at rest in 30 subjects and was related to effort in 7. A histological study was carried out on the obstructive coronary plaques. Degree of lumen stenosis and extension of lipid core and intimal fibrocellular hyperplasia facing the lumen were calculated morphometrically. Immunohistochemistry and electron microscopy were used to further characterize the plaque cell population. Single-vessel disease was found in 33 patients and triple-vessel disease in 4, with an overall total of 45 obstructive plaques, 34 of which were located in the proximal left anterior descending coronary artery. At histological study, only 10 plaques from 10 patients showed acute thrombosis (occlusive in 5 and subocclusive in 5); the remaining 35 were uncomplicated. Thirty-one plaques were fibrous in nature, while the other 14 were atheromatous. Compared with the atheromatous lesions, the fibrous plaques were rarely complicated by thrombosis (3% versus 64%; P < .001) and distinctly exhibited a fairly well-preserved tunica media (81% versus 21%; P < .001) as well as a stratum of neointimal fibrocellular hyperplasia (68% versus 7%; P < .001), which on immunohistochemistry and electron microscopy appeared to be proliferating smooth muscle cells.

CONCLUSIONS

In our study population, sudden death was precipitated by acute coronary thrombosis in only 27% of patients with obstructive coronary atherosclerotic plaque. Most of the young victims of sudden death with obstructive coronary atherosclerosis showed single-vessel disease that affected the left anterior descending coronary artery and was due to fibrous plaques with neointimal smooth muscle cell hyperplasia and a preserved tunica media in the absence of acute thrombosis.

Alcohol and coronary spasm

Alcohol is known to sometimes cause coronary spasm, the mechanism of which is still unknown. The authors monitored changes in plasma levels of prostanoids (thromboxane [TX B2], 6-keto prostaglandin F1 alpha [PGF1 alpha]), catecholamines (CA), serotonin (5-HT), cyclic nucleotides (cyclic adenosine monophosphate--cAMP, cyclic guanosine monophosphate--cGMP), and platelet aggregation after alcohol ingestion (Japanese rice wine 400 mL) in 8 patients with alcohol-induced variant angina and 8 healthy men as controls. Coronary spasm was confirmed to have been induced in 4 patients nine hours after alcohol challenge (VA[+]), when their plasma ethanol levels had already returned to a null level. Neither CA nor 5-HT levels showed any change after alcohol ingestion either in patients or controls, though controls showed high levels of CA during alcohol ingestion. TX B2 in VA(+) patients increased gradually after alcohol ingestion to reach up to a statistically significantly high level just before attack, as compared with those of controls and VA(-) patients, who, on the contrary, did not show such changes. The levels of 6-keto PGF1 alpha, however, which were significantly lower in patients than in controls before the test, exhibited a gradual increase in VA(+) patients in parallel with the increase in TX B2. No significant changes in cAMP levels between either controls or patients were present. On the contrary, cGMP levels had a gradual decrease in patients after alcohol ingestion. Especially six hours after alcohol ingestion, cGMP levels in VA(+) patients decreased so much as to make a statistically significant difference, as compared with the level in controls. Platelet aggregability in controls showed a decrease after alcohol ingestion, in spite of no change or even increase in patients. These data suggest that low levels of PGF1 alpha and the decrease of cGMP levels from alcohol ingestion play important roles in the mechanism of coronary spasm induced by alcohol ingestion.

Vasotonic angina: a spectrum of ischemic syndromes involving functional abnormalities of the epicardial and microvascular coronary circulation

OBJECTIVES

The present study was undertaken to investigate the response of large and small coronary arteries in a subgroup of patients with no or minimal coronary artery disease found to have objective signs of myocardial ischemia.

BACKGROUND

Many patients apparently have normal coronary arteries despite abnormal electrocardiographic (ECG) changes during spontaneous anginal attacks or exercise stress testing.

METHODS

Twenty-five patients with no or minimal (< 30% stenosis) coronary artery disease were chosen from a pool initially selected on the basis of spontaneous anginal attacks and ST segment shifts in the anterior leads. Of these, 10 were grouped as having variant angina (at least one episode of ST elevation) and the remaining 15 as having syndrome X (exercise-induced anginal pain, ST depression and reversible thallium abnormalities). Data were compared with those obtained in 10 patients with stable angina and documented coronary artery disease. Eighteen patients with supraventricular arrhythmias and normal coronary arteries served as control patients. Patients showing focal spasm during ergonovine testing were not included in the subsequent angiographic analysis. Great cardiac vein blood flow, aortic pressure and changes in coronary artery diameter were measured at rest and 2 to 4 min after hyperventilation in the remaining study group. The same procedure was repeated after sublingual administration of 0.3 mg of nitroglycerin in eight patients (four with syndrome X and four with variant angina).

RESULTS

Hyperventilation induced diffuse epicardial coronary diameter reduction, which was marginal in control patients (9 +/- 4%) and those with coronary artery disease (5 +/- 3%) but severe (p < 0.001) in those with variant angina (28 +/- 14%) or syndrome X (25 +/- 13%). Concomitant determination of coronary blood flow showed significant (p < 0.001) decreases in those with variant angina (25 +/- 11%) and syndrome X (28 +/- 10%) but not in control patients (5 +/- 8%) or those with coronary artery disease (4 +/- 5%). Changes in great cardiac vein blood flow during hyperventilation were similar before and after nitroglycerin.

CONCLUSIONS

These findings indicate that vasoconstrictor stimuli may trigger a diffuse abnormal response of both epicardial and resistance vessels in some patients with chest pain and angiographically normal coronary arteries. Patients showing such diffuse vasoconstrictor abnormalities are suggested to have a single pathogenetic entity with a spectrum of ECG manifestations ranging from ST depression to ST elevation.

Somatic and social prognosis of patients with angina pectoris and normal coronary arteriography: a follow-up study

A follow-up over a 7-year period demonstrated that 8.6% of all patients subjected to coronary arteriography because of angina pectoris had normal coronary arteries (NCA). The somatic and social prognosis of these patients were evaluated and these were compared to that of an age- and sex-matched group of patients with arteriographically verified coronary atherosclerosis (CAD). On average 44 months after coronary arteriography, 2.4% with NCA had died versus 20.5% with CAD (P < 0.001). Myocardial infarction occurred in 0% (NCA) versus 12.8% (CAD) among survivors (P < 0.001). Coronary revascularization was carried out in 0% (NCA) versus 76.9% (CAD). Chest pain was unchanged or had worsened in 58.2% (NCA) versus 21.1% (CAD) (P < 0.001) and this in the NCA patients was correlated to the occurrence of minimal lesions of the coronary arteries. Of the NCA patients, 33.3% had ischaemia during exercise-ECG. Normalization was seen in 12 patients and newly developed ischaemia in seven patients. Three patients developed ischaemia during hyperventilation test. Eighty percent (NCA) versus 63.9% (CAD) gave up work due to chest pain (P < 0.001). Further, 55.7% (NCA) versus 34.6% (CAD) had reduced daily activities (P < 0.001); similarly, the frequency of divorce was higher in the NCA group (10.2%) than in the CAD group (1.3%) (P < 0.05).

Effects of a new calcium antagonist, CD-832, on experimental coronary artery spasm in miniature pigs

The effects of a new calcium antagonist, CD-832, on experimental coronary artery spasms were studied in Göttingen miniature pigs. Pigs underwent endothelial denudation at the left anterior descending coronary artery using a balloon catheter. Changes in the diameter of the denuded and nondenuded site in response to an intracoronary administration of serotonin (10 micrograms/kg) or histamine (10 micrograms/kg) were assessed quantitatively by selective coronary arteriography 1 week after endothelial denudation. Percent reductions of the coronary artery diameter induced by serotonin or histamine in the denuded site were significantly greater than those in the nondenuded site (p < 0.01). Coronary artery spasm induced by serotonin or histamine in the denuded site was attenuated in a dose-dependent manner by intravenous infusion of CD-832 (10 and 30 micrograms/kg/min) or nifedipine (1 and 3 micrograms/kg/min). The degrees of inhibition of coronary artery spasm by CD-832 were similar to those produced by nifedipine. CD-832 and nifedipine at the high dose caused comparable increases in the basal coronary artery diameter. These results suggest that CD-832 may be a useful drug for the treatment of coronary artery spasm.

Mechanism of ergonovine-induced hyperconstriction of the large epicardial coronary artery in conscious dogs a month after arterial injury

This study investigated the mechanism of ergonovine-induced hyperconstriction of coronary artery in conscious dogs that had undergone endothelial denudation one month earlier. The diameter of the large epicardial coronary artery was continuously measured by a sonomicrometer in 12 dogs in which two pairs of 10-MHz piezoelectric crystals had been surgically implanted at the denuded and nondenuded sites of coronary arteries. A month after the endothelial denudation, intravenous ergonovine (0.01, 0.1, 0.3, and 1.0 mg) produced transient dilation followed by dose-dependent constriction. The degrees of dilation were comparable between the denuded and nondenuded sites. The magnitudes of constriction induced by ergonovine were significantly larger in the denuded site than in the nondenuded site: the percent reductions in diameter evoked with 0.3 mg ergonovine were 14.4 +/- 2.3% and 3.8 +/- 0.8% (p less than 0.01) at the denuded and nondenuded sites, respectively. The magnitudes of constriction induced by intravenous phenylephrine (0.02, 0.06, and 0.2 mg) were comparable in the denuded and nondenuded sites. Methysergide (a nonselective serotonergic blocker) in a dose of 0.5 mg/kg significantly inhibited vasoconstriction induced by ergonovine (0.3 mg) from 13.1 +/- 1.1% to 2.7 +/- 1.0% (p less than 0.01) at the denuded site and from 4.2 +/- 0.6% to 0.8 +/- 0.3% (p less than 0.05) at the nondenuded site. Diltiazem (1.0 mg/kg) selectively inhibited the ergonovine-induced hyperconstriction. Ketanserin (0.5 mg/kg), prazosin (1.0 mg/kg), or indomethacin (5.0 mg/kg) did not prevent the ergonovine-induced hyperconstriction. Histological study revealed intimal thickening and regenerated endothelium in the denuded site.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasoconstrictor effects of endothelin-1 on myocardium microcirculation studied by the Langendorff perfusion method: differential sensitivities among microvessels

An intravital fluorescence microscope system was used to investigate the pharmacological effects of endothelin-1 (ET-1) on the coronary microcirculation in the isolated beating hearts of rats. The heart was perfused by retrograde aortic steady flow with an oxygenated Krebs-Ringer solution containing FITC-dextran. Changes in diameters of coronary microvessels accompanying the cumulative injection of ET-1 in the perfusate were observed and recorded with a video camera system. Coronary perfusion pressure was also measured during each experiment. Bolus injections of ET-1 (1-300 pmole) elicited a dose-dependent increase in perfusion pressure from 54 +/- 6 mm Hg (mean +/- SEM; n = 10, before the ET-1 injection) to 144 +/- 9 mm Hg (n = 8, at the ET-1 dose of 300 pmole). A dose-dependent narrowing of microvessels was also observed. This vasoconstriction was especially prominent in small-sized arterioles; the maximum vasoconstriction of the smaller arterioles was significantly higher than that of the larger arterioles (P less than 0.05). The response induced by ET-1 dose of 3-10 pmole was significantly larger in arterioles than in postcapillary venules in the diameter range between 10 and 40 microns. The vasoconstriction produced by ET-1 was inhomogeneous. Some part of bifurcations of arterioles showed a prominent localized vasoconstriction, and occasionally showed a complete luminal obstruction. Such a segmental vasospasm might be attributed to localized sensitivities of arterioles to ET-1. These findings suggest that ET-1 may have an important role in governing the coronary resistance and regulating the capillary flow in the myocardium.

Preservation of endothelium-dependent vasodilation in the spastic segment of the human epicardial coronary artery by substance P

The objective of this study was to determine if endothelium-dependent vasodilation is preserved in the spastic segment of the epicardial coronary artery. Segmental responses of the coronary artery to substance P were examined by the use of a quantitative angiographic technique in 21 patients with variant angina. Coronary diameter at the basal state did not differ between the spastic and the nonspastic segments (2.3 +/- 0.2 mm, 2.3 +/- 0.4 mm, p greater than 0.05). Changes in coronary diameter in response to substance P did not differ between segments with ergonovine-induced spasm and nonspastic segments. Maximal dilation averaged 27.1 +/- 9.5% in the spastic segment and 24.4 +/- 9.6% in the nonspastic segment (expressed as a percent increase over the value before drug administration). It appears that both the potential of the endothelium to release endothelium-dependent relaxing factor and the dilating response of the smooth muscle to endothelium-dependent relaxing factor are preserved, even in the spastic segment.

Chronic coronary artery constriction leads to moderate myocyte loss and left ventricular dysfunction and failure in rats

Coronary artery narrowing, ranging from 19% to 61%, was induced in rats and ventricular performance, myocardial damage, and myocyte hypertrophy were examined 1 mo later. Animals were separated into two groups, exhibiting ventricular dysfunction and failure, respectively. Dysfunction consisted of a 2.4-fold increase in left ventricular end diastolic pressure (LVEDP), 15% decrease in left ventricular peak systolic pressure (LVPSP), 24% reduction in developed pressure (DP), and a 16% depression in-dP/dt. Failure was defined on the basis of a 4.7-fold elevation in LVEDP, and a 26%, 47%, 45%, and 41% decrease in LVPSP, DP, +dP/dt, and -dP/dt. Moreover, in this group, right ventricular end diastolic and systolic pressures increased 5.5- and 1.2-fold. Left and right ventricular weights expanded 23% and 51% with dysfunction and 30% and 56% with failure. Left ventricular hypertrophy was characterized by ventricular dilation and wall thinning which were more severe in the failing animals. Foci of damage were found in both groups but tissue injury was more prominent in the endomyocardium and in failing rats. Finally, myocyte loss in the ventricle was 10% and 20% with dysfunction and failure whereas the corresponding enlargements of the unaffected myocytes were 34% and 53%. Thus, coronary narrowing led to abnormalities in cardiac dynamics with an increase in diastolic wall stress and extensive ventricular remodeling in spite of a moderate loss of myocytes and compensatory reactive hypertrophy of the viable cells.

Angiotensin II facilitates tricyclic antidepressant-induced changes in QRS-duration in the rat

Experimental evidence indicates that angiotensin II can modulate sodium channel and gap junction function. This raises the possibility that variations in angiotensin II could alter the effect of drugs that act on these mechanisms. In this study, the influence of changing salt status and angiotensin II activity has been investigated by evaluating the QRS prolonging effects of the sodium channel blocking drug, desmethylimipramine. In control rats with a normal salt intake, intravenous infusion of desmethylimipramine (0.8 mg/kg/min) over 60 min increased QRS duration over time to 150% of control by 60 min; mean arterial blood pressure and pulse rate were decreased. In salt-deplete rats, the response to desmethylimipramine was similar to controls for 30 min. Thereafter, QRS duration increased more rapidly than controls. In rats on a high salt diet, the same desmethylimipramine infusion produced no change in QRS duration for 30 min, despite equivalent reductions in mean arterial blood pressure. Thereafter, QRS duration increased, reaching values similar to control by 60 min. In rats on a normal salt diet pretreated with captopril, there was a similar blunting of the QRS response to desmethylimipramine to that observed in salt-loaded rats. The QRS response to desmethylimipramine and salt-loaded rats on normal salt diets receiving captopril returned to the control pattern after a subpressor infusion of angiotensin II (3 ng/min), while a higher rate of angiotensin II (10 ng/min) further enhanced the QRS prolonging effect of desmethylimipramine. These data demonstrate that endogenous angiotensin II contributes to the regulation of the cardiac electro-physiological response to DMI.

Chronic nonocclusive coronary artery constriction in rats. Beta-adrenoceptor signal transduction and ventricular failure

To determine the effects of chronic coronary artery constriction on the relationship between cardiac function and regulation of beta-adrenoceptor signal transduction, the left main coronary artery was narrowed in rats and the animals were killed 5 mo later. An average reduction in coronary luminal diameter of 44% was obtained and this change resulted in an increase in left ventricular end-diastolic pressure and a decrease in positive and negative dP/dt. Significant increases in left and right ventricular weights indicative of global cardiac hypertrophy were observed. Radioligand binding studies of beta-adrenoreceptors, agonist-stimulated adenylate cyclase activity, and ADP ribosylation of 45-kD substrate by cholera toxin were all depressed in the failing left ventricle. In contrast, in the hypertrophic non-failing right ventricle, beta-adrenoreceptor density was preserved and receptor antagonist affinity was increased. In spite of these findings at the receptor level, agonist stimulated cyclic AMP generation was reduced in the right ventricular myocardium. The quantity of the 45-kD substrate was also decreased. In conclusion, longterm nonocclusive coronary artery stenosis of moderate degree has profound detrimental effects on the contractile performance of the heart in association with marked attenuation of adrenergic support mechanisms.

Effects of cocaine on epicardial coronary artery reactivity in miniature swine after endothelial injury and high cholesterol feeding. In vivo and in vitro analysis

The purpose of this study was to determine the effects of cocaine on vasoreactivity in the swine model. Eight miniature pigs underwent regional endothelial denudation of the left anterior descending coronary artery and were then fed a high cholesterol diet. Cross-sectional area (CSA) of coronary arteries was measured by quantitative angiography. Before denudation, intravenous cocaine (1, 3, and 10 mg/kg) decreased CSA of epicardial vessels by 19-44%. At 3 mo after the denudation, the percent reduction in CSA of the denuded vessels induced by the 10 mg/kg dose was significantly augmented compared to nondenuded vessels (59 +/- 5% vs. 48 +/- 4%, P less than 0.05). Under in vitro conditions where isometric force of isolated ring segments was measured, methoxamine (an alpha 1 agonist) or BHT-920 (an alpha 2 agonist) produced similar degrees of contraction of denuded and control vessels; however, cocaine in concentrations up to 3 x 10(-3) M did not produce contraction. These responses were unaffected by removal of the endothelium. Histologically, myointimal thickening was noted at the denuded site. The present study demonstrates an enhanced vasoreactivity of atherosclerotic coronary arteries to cocaine in vivo, the mechanism of which appears to be mediated by endogenous vasoactive substances rather than by a direct action of cocaine on vascular smooth muscle.

Coronary vasoconstriction induced by vasopressin. Production of myocardial ischemia in dogs by constriction of nondiseased small vessels

BACKGROUND

We studied the effect of intracoronary administration of arginine-8-vasopressin on blood flow in nondiseased coronary arteries and determined whether this vasoconstriction was severe enough to produce ischemia in 30 dogs.

METHODS AND RESULTS

In group 1 (n = 6), after vasopressin administration coronary blood flow was decreased by 41% (p less than 0.002) without changes in heart rate or aortic pressure, and left ventricular ejection fraction measured by radionuclide angiocardiography was decreased by 18% (p less than 0.0005). In group 2 (n = 6), ischemia was confirmed by measurement of transmural pH changes. Administration of vasopressin decreased subendocardial pH of the infused zone from 7.40 +/- 0.03 to 7.31 +/- 0.07 (p less than 0.01). The subendocardial pH of the zone not infused with vasopressin did not change. To overcome the intrinsic regulation of blood flow, operating primarily in small coronary arteries, we hypothesized that vasopressin must increase resistance primarily in large rather than small coronary arteries. After intracoronary infusion in group 3 (n = 6), however, most (94%) of the increase in resistance during vasopressin administration was explained by an increase of resistance in small coronary arteries. In group 4 (n = 9), vasopressin decreased coronary blood flow by 50% and decreased local shortening by 90% at a time when systemic hemodynamics were unchanged. Coronary constriction induced by vasopressin, or the recovery from it, also was not altered by cyclooxygenase blockade.

CONCLUSIONS

Thus, vasopressin produces myocardial ischemia by constricting small, nondiseased coronary arteries severely enough to overcome the competition from normal coronary regulation, and this ischemic event is not mediated by prostaglandin products.

Effect of direct intracoronary administration of methylergonovine in patients with and without variant angina

The effects of intracoronary administration of methylergonovine were studied in 21 patients with variant angina and 22 patients with atypical chest pain and in others without angina pectoris (control group). Methylergonovine was administered continuously at a rate of 10 micrograms/min up to 50 micrograms. In all patients with variant angina, coronary spasm was provoked at a mean dose of 28 +/- 13 micrograms (mean +/- SD). In the control group neither ischemic ST change nor localized spasm occurred. The basal tone of the right coronary artery was significantly lower than that of the left coronary artery. The percentage of vasoconstriction of the right coronary artery was significantly higher than that of the left coronary artery. These results suggest that spasm provocation tests, which use an intracoronary injection of a relatively low dose of methylergonovine, have a high sensitivity in variant angina and the vasoreactivity of the right coronary artery may be greater than that of the other coronary arteries.

Experimental induction of spasm, sudden progression of organic stenosis and intramural hemorrhage in the epicardial coronary arteries

Pathogenesis of the so-called "heart attack" still remains to be elucidated. The links between stable effort angina and unstable or acute myocardial infarction, and between asymptomatic and spontaneous angina are all missing. In medicine presently, pathophysiology of ischemic heart disease is considered a consequence of i) the progression of atherosclerotic narrowing of the coronary artery, and ii) dynamic and transient obstruction (coronary spasm), but these mechanisms are traditionally believed to be unrelated. This article demonstrates various experimental evidence indicating that these two mechanisms are related. And, this review article describes how to produce experimental coronary spasm in the presence of atherosclerosis, similar to that seen in patients with variant angina, and that coronary spasm can produce sudden progression of coronary atherosclerotic obstruction due to intramural hemorrhage. Establishment of various animal models to elucidate mechanisms related to various stages of ischemic heart disease are needed.

Clinical characteristics and coronary angiographic findings of patients with unstable angina, acute myocardial infarction, and survivors of sudden ischemic death occurring during and after sport

The clinical characteristics and coronary angiographic findings of 42 well-conditioned subjects with an acute ischemic event related to sport are reported. Five patients had unstable angina, 25 had acute myocardial infarction (AMI), and 12 were resuscitated victims of sudden ischemic death. Twenty-two events occurred during sport (group A) and 20 after sport (group B). There were two women and 40 men. The mean age was 46 years (range 25 to 65). Twelve out of 30 patients who smoked cigarettes had an adjunctive risk factor for coronary artery disease. Twelve others (28%) had no identifiable risk factor. Prodromal cardiac symptoms were detected in three patients (group A). Two patients had previous myocardial infarction (group B). Coronary angiography was performed acutely in 39 patients. The distribution of the ischemia-related coronary artery was comparable in both groups. The lesion morphology of 35 culprit coronary arteries was described as concentric in six patients and eccentric with regular borders (type I lesion) in 11 and irregular borders (type II lesion) in 18. Eccentric lesions consistent with ruptured plaques prevailed in both groups. Associated coronary artery disease was present in 10 patients. There was no relationship between the number of risk factors and the extent of diseased coronary arteries. Clinical characteristics and coronary angiographic findings of patients with unstable angina, AMI, and sudden death either during or after sport are similar and indicate a common pathogenesis. The probable mechanism of a coronary event related to sport is exercise-induced plaque rupture. In most instances such an event is unexpected and unpredictable. Identification of some subjects at risk is possible.

Effects of calcium channel blockers on coronary vasoconstriction induced by endothelin-1 in closed chest pigs

The purpose of this study was to determine the effects of endothelin-1 on the coronary vascular bed of closed chest pigs. Endothelin-1 (3 to 30 pmol/kg body weight) was selectively administered into the left anterior descending coronary artery. Coronary blood flow and epicardial vessel diameter were measured by quantitative arteriography. Arterial pressure increased after a 30 pmol/kg dose and heart rate was not changed. Coronary blood flow and vessel diameter of the left anterior descending artery significantly decreased by 74% and 32%, respectively (p less than 0.01 versus control) after the 30 pmol/kg dose, whereas these variables modestly decreased in the left circumflex artery. Endothelin-1 in doses of 10 to 30 pmol/kg produced electrocardiographic ST segment elevation associated with decreased oxygen saturation of coronary sinus venous blood. Endothelin-induced coronary vasoconstriction was significantly inhibited after treatment with intravenous diltiazem (0.2 mg/kg, n = 6) or nifedipine (0.1 mg/kg, n = 5), but not after vehicle administration (n = 4). This study demonstrates that intracoronary administration of endothelin-1 causes significant myocardial ischemia through coronary vasoconstriction, which is inhibited by a calcium channel blocker. The data suggest that calcium influx into the smooth muscle cells appears to be involved at least in part in the mechanism of endothelin-induced coronary vasoconstriction in vivo.

Sympathetic and nonsympathetic neuropeptide Y-containing nerves in the rat myocardium and coronary arteries

We have examined the neuropeptide Y-containing intrinsic nerves of the heart in young (6-week-old) and adult (4-month-old) rats to determine whether they project to the coronary arteries or are capable of doing so if the neuropeptide Y-containing extrinsic nerves are removed. Chronic treatment of neonates with guanethidine was used to permanently destroy the sympathetic nerves. In the young treated animals, 33-54% of the neuropeptide Y remained in the heart despite a 90-99% reduction in norepinephrine; these proportions did not change in the animals that were allowed to develop to adulthood. The level of neuropeptide Y in the right atrium of young animals was unexpectedly high (252 +/- 28.7 pmol/g) compared with adults (75.4 +/- 18.8 pmol/g). The coronary arteries in the control rats received a moderately dense supply of neuropeptide Y-containing nerves; after guanethidine, all neuropeptide Y-containing nerves innervating the large coronary arteries disappeared, but some were still seen in association with small resistance vessels. No compensatory proliferation of the intrinsic neuropeptide Y-containing neurons occurred in the adult sympathectomized animals, and the intrinsic nerves did not reinnervate the large coronary arteries. These results are discussed in relation to the clinical syndrome of coronary artery spasm.

Possible role of coronary artery spasm in unexplained syncope

Coronary spasm provocation by intracoronary methylergonovine was performed in 14 patients (8 men and 6 women, mean age 56 +/- 6 years) with syncope that remained unexplained despite neurologic and noninvasive cardiac evaluations. Electrophysiologic testing was also performed in 6 of 14 patients. No patient had structural heart disease or significant fixed stenosis of greater than or equal to 75% in the coronary arteries. Six patients had no history of chest pain even when they developed syncope. Serious arrhythmia was documented in 2 patients, cardiac standstill in 1 and complete atrioventricular block in the other. Coronary spasm was induced in 9 patients using the methylergonovine provocation test. Multivessel spasms were found in 3 patients. Coronary spasm was induced in the artery supplying the inferior wall in 7 of 9 patients with positive results. In 4 of 9 patients who had a positive result, there was no prior history of chest pain. In 1 patient, whose electrocardiogram was recorded during syncope, cardiac standstill was documented and cardiac standstill and syncope also occurred during the provocation test. Monomorphic ventricular tachycardia was not induced by the electrophysiologic study. These results suggest that coronary spasm is involved in unexplained syncope.

Response of large and small coronary arteries of pigs to intracoronary injection of acetylcholine: angiographic and histologic analysis

With coronary arteriography we examined the effect of acetylcholine (ACh) on large and small coronary arteries. ACh (12.5 to 200 micrograms) was injected into the right coronary arteries of 10 pigs during left ventricular pacing. The percentage of narrowing of the epicardial major coronary artery was used as an indicator of the constriction of the large coronary arteries, and the time required for the contrast medium to reach the posterior descending coronary artery from the ostium of the right coronary artery (blood-flow delay) was used as an indicator of the constriction of the same coronary arteries. A small dose of ACh (12.5 to 100 micrograms) induced mild narrowing (14 to 41%) of the epicardial major coronary artery and a marked blood-flow delay of over 7.0 sec (control: less than or equal to 1.8 sec) in all 10 pigs. A large dose of ACh (100 to 200 micrograms) caused over 75% narrowing of the epicardial major coronary artery and a marked blood-flow delay in 4 of the 10 pigs. When the marked blood-flow delay appeared, the perfused right ventricular myocardium became macroscopically anemic (ischemic). The constriction of large and small coronary arteries was not prevented by diphenhydramine (H1 blocker: 100 mg i.v.), but was prevented by pretreatment with atropine (1.0 mg i.v.). The intracoronary injection of histamine (1.5 mg) in 5 pigs constricted the epicardial major coronary artery over 75% in 2 pigs, 50 to 75% in 1 pig, and 25 to 50% in 2 pigs, but there was no evidence of blood-flow delay. Neither methoxamine nor norepinephrine caused any significant coronary artery narrowing. The histology of the large and small coronary arteries was examined quantitatively with an image analyzer. The coronary artery showed no intimal thickening, and the endothelium was intact on light microscopic examination. The % area of the smooth muscle layer (media) to the calculated total vascular area, and the ratio of the calculated medial thickness to the calculated inner radius (h/Ri) were 64 +/- 7% (mean +/- SD) and 0.69 +/- 0.16, respectively, in the small coronary arteries less than 100 microns in external diameter, 47 +/- 9% and 0.39 +/- 0.12 in the small coronary arteries 100 to 2000 microns in external diameter, and 34 +/- 4% and 0.24 +/- 0.03 in the large right coronary arteries over 2000 microns in external diameter; the % area of the media and the h/Ri showed a negative correlation with the size of the coronary arteries.(ABSTRACT TRUNCATED AT 400 WORDS)

Attenuation of the vasoconstrictor action of neuropeptide-Y by calcium-channel blockers

Neuropeptide-Y (NPY) was administered intracoronarily in dogs to see the modification of its vasoconstrictor action by the calcium (Ca)-channel blockers nisoldipine (0.1 microgram/kg) and nifedipine (1 microgram/kg). Dogs were anesthetized and the left circumflex artery was cannulated without opening the chest by using a specially designed cannula perfused at constant pressure. The change in coronary flow due to NPY was determined before and after the systemic administration of the two Ca-channel blockers. With administration of 1 to 2 nmol of NPY, coronary blood flow decreased maximally by 23.4 +/- 7.8% without changes in perfusion pressure or central venous pressure and it became significantly less after nisoldipine: 16.0 +/- 5.7% (p less than 0.02). A similar attenuation in the decrease in coronary flow was observed in the nifedipine study: 23.2 +/- 7.5% to 12.0 +/- 6.7% (p less than 0.02). A fall in systemic arterial blood pressure was observed after administration of both Ca-channel blockers, but it was significant only after nisoldipine (p less than 0.01). Nonsignificant increases in heart rate were observed after both drugs. Nisoldipine seemed to attenuate the NPY-induced vasoconstriction in dogs, and its equimolar potency is about ten times that of nifedipine.

Myocardial infarction and sudden death after sport: acute coronary angiographic findings

Thirteen patients, seven with acute myocardial infarction and six survivors of sudden death after sport, underwent coronary angiography within a mean of 104 min after the onset of symptoms. The admission electrocardiogram showed transmural myocardial ischemia in all patients. The ischemia-related vessel was occluded in all cases of sudden death and in three cases of acute myocardial infarction. Reperfusion was achieved in eight vessels: after intracoronary streptokinase in three, after intracoronary nitroglycerin in three, and mechanically in two. Coronary spasm was demonstrated in three vessels, and coronary thrombi, in four. The coronary lesion was described as either concentric in two or eccentric with irregular borders in eight. There was a high incidence of eccentric lesions consistent with ruptured plaques. The acute coronary angiographic findings of acute myocardial infarction and sudden death after sport are similar. Physical exercise can provoke myocardial infarction and sudden death probably by inducing plaque rupture that can evoke coronary spasm, thrombosis, or both.

Unstable angina, myocardial infarction and sudden death after an exercise stress test

We performed coronary angiography within 95 minutes of the onset of symptoms in seven patients with an acute coronary event after an exercise stress test. The test was normal in six patients. Previous angiography in four patients revealed no evident or moderate obstructive coronary arterial disease. After the test, unstable angina developed in two patients, acute myocardial infarction in four and ventricular fibrillation in one, who was successfully resuscitated. At acute angiography the coronary artery involved was occluded in four and sub-totally obstructed in three. In three cases, coronary occlusion was due to thrombosis, vasospasm, or both. In six vessels there was an eccentric lesion, which is consistent with a ruptured plaque. These findings show that physical exercise can unexpectedly provoke an acute coronary event with sub-total or total occlusion of a previous angiographically normal or moderately obstructed coronary artery. The mechanism is probably related to exercise-induced plaque rupture which can produce coronary (sub)occlusion by coronary thrombosis, spasm, or both.

Neuropeptide-Y. A peptide found in human coronary arteries constricts primarily small coronary arteries to produce myocardial ischemia in dogs

Neuropeptide-Y (NPY), a brain peptide, is located in the walls of human coronary arteries. This study assessed the effects of NPY on the coronary circulation in 40 chloralose-anesthetized, open-chest dogs. Intracoronary NPY (42 nmol over 5.2 min) caused a 39% reduction in coronary blood flow without changing heart rate or aortic pressure. To determine whether this vasoconstriction could produce ischemia, intramyocardial pH was measured in seven dogs (group I) and decreased from 7.45 +/- 0.06 to 7.37 +/- 0.06 pH units after NPY in the subendocardium (P less than 0.0002), and from 7.45 +/- 0.06 to 7.40 +/- 0.05 pH units (P less than 0.04) in the subepicardium of the infused zone. Left ventricular ejection fraction (LVEF), measured by radionuclide angiography, decreased from 0.52 +/- 0.08 to 0.42 +/- 0.12 U (n = 5, P less than 0.01) during NPY. NPY-induced vasoconstriction was also associated with ST-T wave changes on the electrocardiogram (ECG) in eight of nine other animals (group V). In another group of six dogs (group IV), the change in small vessel resistance accounted for 94% of the increase in total resistance, so that the primary vasoconstrictor effect of NPY was exerted on small coronary arteries. Thus, NPY, a peptide found in human coronary arteries, caused constriction of primarily small coronary arteries that was severe enough to produce myocardial ischemia as determined by ECG ST-T wave changes, and decreases in intramyocardial pH and LVEF in dogs.

Enhanced responsiveness of smooth muscle, impaired endothelium-dependent relaxation and the genesis of coronary spasm

Pathophysiology and genesis of coronary artery spasm were examined in vivo and in vitro in Göttingen miniature pigs. Five of 36 consecutive pigs before endothelial denudation showed evidence of regional hyperconstriction after intracoronary administration of histamine (group 1). Histologic examination revealed intimal thickening along the spastic site. Because 5 pigs died during endothelial denudation, cholesterol feeding was randomly assigned to 13 of the remaining 26 pigs (group 2) and others were fed a regular low cholesterol diet (group 3) for 3 months. Regional coronary hyperconstriction was also evident after intracoronary administration of histamine at the site of denudation, and the degree of constriction was 78 +/- 3 and 74 +/- 4% in groups 2 and 3, respectively. Because the intimal thickening was confirmed at the site of spasm in groups 2 and 3, spontaneous as well as denudation-induced intimal thickening accompanied the enhanced responsiveness to histamine, irrespective of the level of serum cholesterol. However, the role of geometry on histamine-induced luminal narrowing was only 6% and was not physiologically significant. Augmented responses of the coronary artery to histamine, but not to phenylephrine or potassium chloride were reproduced in the nonbeating isolated heart preparations perfused at 90 mm Hg with oxygenated Krebs-Henseleit solution, and the degree and location of in vitro hyperconstriction were similar to that in vivo and were not attenuated after pretreatment with the nerve transmitter blockers, guanethidine (3 X 10(-6) M), atropine (10(-6) M) and tetrodotoxin (3 X 10(-7) M). Accordingly, spasm can be provoked without the influence of blood constituents and neural factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Silent myocardial ischemia. Mechanisms and rationale for therapy

The widespread use of Holter monitoring has demonstrated that the majority of ischemic episodes occur during activities that do not require exertion. These episodes tend to occur at only minimal increases in heart rate above resting levels, well below the level of myocardial oxygen demand required to produce ischemia on formal exercise tolerance testing. In all likelihood, therefore, most ischemic events in ambulatory patients are due to a combination of flow-limiting coronary stenosis and superimposed vasoactive or thrombotic elements. Asymptomatic ischemic events are common in subsets of patients with angina pectoris. Traditionally, treatment with calcium channel blockers, beta-blockers, and long-acting nitrates has been aimed at reducing episodes of angina pectoris. Despite a reduction in anginal symptoms, however, it is likely that patients continue to experience silent ischemia, particularly at rest and during activities of daily living. The strategy for treatment in such patients should include the abolition of the patients' "total ischemic activity." It is conceivable that more aggressive anti-ischemic therapy may improve prognosis, as patients with ambulatory ST-segment depression experience frequent cardiac events. Other potential benefits of more aggressive treatment include the prevention of myocardial hibernation, which occurs as a result of a chronic ischemic state, and a reduction in episodes of myocardial stunning. This approach may lead to protection against transient and chronic left ventricular dysfunction, which is associated with a poor prognosis in patients with symptomatic coronary artery disease.

Profile of an ideal antianginal agent

Many antianginal agents are available for the treatment of coronary artery disease. These agents act by influencing the determinants of myocardial oxygen supply and demand. The 3 main classes of agents are the nitrates, beta-adrenergic blocking agents and the calcium entry blockers. Agents from all 3 classes have shown efficacy in treating both symptomatic and asymptomatic myocardial ischaemia. However, some patients cannot be treated with these agents because of side effects or contraindications. An ideal antianginal drug should effectively treat both angina and silent ischaemia. Additionally, it should be free of side effects, allow for maintenance of physical performance and be metabolically neutral. New agents are being developed which strive for this goal.

Biphasic response of coronary arterial diameter to intracoronary ergonovine

This report presents a case of paradoxical coronary arterial dilation induced by intracoronary ergonovine. When compared with the control angiogram, the right coronary artery obviously dilated with selective, intracoronary administration of cumulative doses of 5 micrograms and 15 micrograms ergonovine without concomitant hemodynamic changes. Additional intracoronary infusion of 35 micrograms ergonovine into the right coronary artery inversely increased vascular tone of the vessel associated with a focal hyperconstriction. Such a biphasic response of arterial diameter to intracoronary ergonovine was also observed in the left coronary artery, but the degree of dilation was much smaller.

Unstable angina: ST segment depression with positive versus negative T wave deflections--clinical course, ECG evolution, and angiographic correlation

Thirty-two consecutive patients who initially had horizontal or downward-sloping ST segment depression confined to the precordial leads were studied. Patients were divided into two groups: group A included 21 patients with horizontal or downward-sloping ST depression with peaked positive T waves, and group B comprised 11 patients with peaked negative T waves and downward or horizontal ST depression. The incidence of acute myocardial infarction (AMI) was similar (group A 38.1% vs group B 36.4%; p greater than 0.05). In-hospital mortality was much more significant in group B (p = 0.03). Coronary arteriography was performed in 31 patients. Of the 10 patients in group B who were catheterized, seven (70%) had left main occlusion. Of the 21 patients in group A, none had a significant left main lesion (p = 0.001), although eight (38.1%) had single-vessel disease (p = 0.05). Thus the ECG pattern of horizontal or downward-sloping ST depression passing into a peaked negative T wave identifies a subgroup of high-risk patients in whom the prognosis is poor once AMI occurs. Early catheterization is recommended when this ischemic pattern is apparent on the ECG.

Coronary artery spasm following coronary artery surgery

Coronary artery spasm during the early postoperative period following cardiopulmonary bypass for coronary artery surgery can be an unrecognized cause of sudden, severe cardiopulmonary collapse. The literature regarding perioperative coronary artery spasm is reviewed, and methods of prevention, diagnosis, and treatment are suggested. Preoperative angina at rest appears to be an important identifying factor in patients who experience postoperative coronary spasm. Anatomically, the presence of a relatively normal, dominant right coronary may also indicate increased risk for early post-coronary bypass spasm. Acute hypotension is often the first sign of coronary artery spasm, and conventional treatment methods may only worsen the vasospastic reaction. Peripheral intravenous nitroglycerin infusion has often been unsuccessful treatment while intragraft or intracoronary nitroglycerin injection or administration of calcium channel-blocking drugs, or both, has proven to be effective in reversing the coronary artery spasm and ventricular dysfunction. Reluctance to use vasodilating agents must be overcome, even in the face of hypotension, when evidence of spasm is present.

Vasospastic coronary occlusion associated with a myocardial bridge

A 53-year-old woman was admitted with unstable angina. Acute coronary angiography showed myocardial bridging and total occlusion of the left anterior descending artery in the middle one-third of its course. The occlusion was completely relieved by intracoronary administration of nitroglycerin. The occurrence of coronary spasm may explain angina and myocardial infarction in symptomatic patients with myocardial bridges.

Attenuation of endothelium-related relaxation and enhanced responsiveness of vascular smooth muscle to histamine in spastic coronary arterial segments from miniature pigs

Mechanism of coronary spasm was examined regarding endothelium-related relaxation and contraction produced by smooth muscle cells of spastic vessels isolated from Göttingen miniature pigs. In these pigs, coronary artery spasm was documented angiographically in vivo three months after endothelial denudation, and spastic and control segments of the coronary artery were suspended in organ chambers at their optimal length for generating tension. Applications of KCl (118 mM), acetylcholine(10(-9) to 10(-4) M), and PGF2 alpha (10(-8) to 3 X 10(-5) M) produced similar tension, at the respective doses, in both the spastic and control coronary arteries. During increasing concentrations of histamine (10(-8) to 3 X 10(-4) M; n = 14) and serotonin (10(-9) to 10(-5) M; n = 13), the maximum tension of the spastic vessel was 136 +/- 6 and 97 +/- 4%, respectively, of the tension produced by 118 mM KCl. That is significantly larger than seen in the control vessels: 98 +/- 4 and 74 +/- 4%, respectively. The ED50 to histamine and serotonin was also significantly less in the spastic vessels. After mechanical removal of the endothelium, the tension generated during the cumulative administration of histamine (n = 8) but not serotonin (n = 8) was larger in the spastic than the control vessels, thereby suggesting the presence of augmented responses of the smooth muscle to histamine in the spastic vessels. The increase in maximum tension after mechanical denudation was greater in the control than the spastic vessels in cases of histamine and serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary artery spasm: involvement of small intramyocardial branches

A study was conducted to determine if the small (resistance) vessels of the coronary circulation could undergo spasm comparable to that of the major conductance (epicardial) arteries which in the rat measure 275-300 micron in diameter. This information may be relevant to the growing evidence of ischemic myocardial disease without significant coronary atherosclerosis or even spasm of the larger vessels. Vascular corrosion casts of the coronary circulation were prepared in the rat 20 min after intravenous injection of arginine vasopressin, a powerful coronary constrictor substance, under continuous electrocardiographic monitoring. Electrocardiographic changes observed consisted of S-T segment elevation and conduction disturbances, implying ischemic effects on the myocardium. Corrosion casts revealed spasm of smaller arteries only (50-150 micron diameter). Controls (vehicle-injected or untreated) showed no abnormalities of the coronary vasculature. These results suggest that myocardial vessels of this size are comparable in their potential for spasm to the large conductance arteries. Similar findings in patients involving smaller vessels could explain ischemic myocardial events in the absence of significant spasm, or organic stenosing pathology of major coronary arteries. As a corollary, it is suggested that the term "coronary artery spasm" could be enlarged in its definition to include other levels of the coronary circulation rather than that of the large conductance arteries alone.

Amplification of serotonin-induced contractions of isolated porcine coronary arteries after pretreatment with therapeutic doses of beta-methyldigoxin

The present experiments demonstrate that after pretreatment of isolated porcine coronary arteries with therapeutic (2.5 X 10(-9) M) was well as with toxic (10(-6) M) doses of beta-methyldigoxin the serotonin-induced contractions were significantly amplified. Since serotonin released from destroyed thrombocytes may be one of the triggering factors eliciting coronary spasms, caution must be taken in the use of digitalis in coronary disease of spastic origin.