Endothelial nitric oxide synthase T-786C mutation, a reversible etiology of Prinzmetal's angina pectoris

Because the endothelial nitric oxide synthase (eNOS) T-786C polymorphism is associated with reduced nitric oxide production and coronary artery spasm in Japanese patients, we speculated that it might be reversibly associated with Prinzmetal's variant angina in white Americans. Polymerase chain reaction analyses of eNOS T-786C and stromelysin 5A6A polymorphisms were done in 31 women and 12 men (42 white and 1 black American, median age 50 years), with well-documented Prinzmetal's variant angina. We matched each case with 1 healthy control by race and gender. Of the 43 cases, 21 (49%) were homozygous for wild-type normal eNOS, 19 (44%) were T-786C heterozygotes, and 3 (7%) were T-786C homozygotes. Of the 43 controls, 31 (72%) were homozygous for wild-type normal eNOS, 12 (28%) were T-786C heterozygotes, and 0 (0%) were T-786C homozygotes (p = .013). The mutant eNOS T-786C allele frequency in patients was 25 (29%) of 86 vs 12 (14%) of 86 in the controls (p = 0.016). Patients did not differ from controls for the distribution of the stromelysin 6A mutation (p = 0.66) or for the mutant 6A allele frequency (53% in cases, 50% in controls; p = 0.65). Nineteen patients took nitric oxide-elevating l-arginine (9.2 g/day, orally). Of these 19 patients, 10 (53%) became free of angina, 3 (16%) were improved but not angina free, and 6 (32%) had no change in their angina. Using l-arginine, the physical ability score (Seattle Angina Questionnaire) increased from a median of 42 to 72 of a total possible score of 100 (p = 0.011), satisfaction with symptom reduction increased from 53 to 61 (p = 0.004), and the perception of quality of life as acceptable increased from 29 to 50 (p = 0.001). In conclusion, the eNOS T-786C mutation appears to be a reversible etiology of Prinzmetal's variant angina in white Americans whose angina might be ameliorated by l-arginine.

Relationship between the Degree of Intracellular Magnesium Deficiency and the Frequency of Chest Pain in Women with Variant Angina

OBJECTIVES

This study sought to clarify the relationship between the degree of intracellular magnesium deficiency and the frequency of anginal attacks in women with variant angina.

PATIENTS AND METHODS

We evaluated the intracellular and extracellular magnesium status of twelve women with variant angina: group A (> or = 4 attacks/week, n = 5) and group B (< 4 attacks/week, n = 7). Magnesium levels were determined in serum, urine, and erythrocytes, and the 24-h magnesium retention rate was calculated by magnesium loading test.

RESULTS

Group A showed a higher 24-h magnesium retention rate (58.2 +/- 9.1% vs. 31.3 +/- 4.4%; p < 0.01) and a lower intracellular concentration of magnesium in erythrocytes than group B (3.1 +/- 1.1 vs. 5.0 +/- 0.8 fg/cell; p < 0.05), demonstrating the presence of magnesium deficiency in group A. The 24-h magnesium retention rate and intracellular concentrations of magnesium in erythrocytes correlated well with the activity of variant angina (r = 0.61, p < 0.01; and r = -0.74, p < 0.01, respectively) for these patients.

CONCLUSION

This study demonstrates that the degree of intracellular magnesium deficiency in women with variant angina is closely related to the frequency of chest pain.

Episodic coronary artery vasospasm and hypertension develop in the absence of Sur2 K(ATP) channels

K(ATP) channels couple the intracellular energy state to membrane excitability and regulate a wide array of biologic activities. K(ATP) channels contain a pore-forming inwardly rectifying potassium channel and a sulfonylurea receptor regulatory subunit (SUR1 or SUR2). To clarify the role of K(ATP) channels in vascular smooth muscle, we studied Sur2 gene-targeted mice (Sur2(-/-)) and found significantly elevated resting blood pressures and sudden death. Using in vivo monitoring, we detected transient, repeated episodes of coronary artery vasospasm in Sur2(-/-) mice. Focal narrowings in the coronary arteries were present in Sur2(-/-) mice consistent with vascular spasm. We treated Sur2(-/-) mice with a calcium channel antagonist and successfully reduced vasospastic episodes. The intermittent coronary artery vasospasm seen in Sur2(-/-) mice provides a model for the human disorder Prinzmetal variant angina and demonstrates that the SUR2 K(ATP) channel is a critical regulator of episodic vasomotor activity.

[Activity of transmembrane calcium transport and levels of endothelin-1 in patients with variant angina]

Recent studies showed that coronary artery spasm may be due to disturbances of secretory and excretory endothelial activity in atherosclerotic coronary artery. However, this theory does not explain the reasons of coronary artery spasm when endothelium is not damaged. There must be other patomechanisms of coronary artery spasm. The aim of our study was examination of calcium efflux through the lymphocytic cell membrane and determination of endothelin-1 plasma levels in patients with variant angina in order to define the participation of these factors in pathogenesis of coronary artery spasm. The survey was made in 76 patients with ischaemic heart disease. All patients were divided into 2 groups. The first group consisted of 48 patients with variant angina (d.b.s.), the other consisted of 28 patients with stable angina (d.b.w.). The control group (g.k.) was composed of 25 healthy people. Patients were administered 100 ml of trometamol (TRIS, pH = 10.5) intravenously for 5 minutes. After stopping the infusion the examined patient was breathing deeply for 5 minutes at a rate of 40/min. The endothelin-1 (ET-1) plasma levels and transmembrane calcium transport in lymphocytes were determined before and just after the hyperventilation test, as well as 10 minutes after the test. ET-1 plasma concentrations were estimated with a radioimmunologic assay. The method of estimation of transmembrane calcium transport was elaborated in Laboratory of Department of Cardiology of Medical University of Wrocław. We showed that ET-1 plasma levels and transmembrane calcium transport in patients with d.b.s. before the test were normal. There was an increase in transmembrane calcium efflux in patients with d.b.s. during coronary artery spasm that had been caused by ET-1. ET-1 plasma levels were still high 10 min. after the coronary artery spasm. Disturbances of transmembrane calcium transport and increased endothelin-1 plasma level may be the primary factors responsible for coronary artery spasm.

Impairment of serotonin-mediated nitric oxide release across the coronary bed in patients with coronary spastic angina

Simultaneous assessment of plasma nitrate/nitrite and serotonin levels revealed possible impairment of serotonin-mediated nitric oxide release in patients with coronary spastic angina.

Abnormal fatty acid metabolism in patients with coronary vasospasm

Although various noninvasive methods have been used to detect vasospasm, none of them are sensitive enough for patients with sporadic attacks. Since abnormal fatty acid metabolism is observed in ischemic myocardium, 123I-beta-methyl-p-iodophenyl pentadecanoic acid (BMIPP), a radiolabeled fatty acid analog, has recently been proposed as a useful tracer for detecting myocardial damage. The aim of this study was to clarify the clinical implications of decreased myocardial BMIPP uptake in patients with vasospastic angina. We evaluated 53 patients with vasospastic angina (32 with clinically documented vasospasm [Group-A] and 21 with vasospasm induced by ergonovine provocation [Group-B]) and 27 control subjects, 20 in Group-A were re-evaluated 6 months after medical treatment. The territorial regions of vasospasm-induced coronary artery, the wall motion by left ventriculography, and BMIPP uptake were compared. Vasospasm was induced in multiple coronary arteries in 29 (55%) patients. Reduced wall motion and decreased BMIPP uptake were observed in 19 (36%) patients and 47 (89%) patients, respectively. The sensitivity and specificity of determination of vasospasm-induced coronary arteries with BMIPP scintigraphy were 71% (69/97 coronary arteries) and 88% (126/143), respectively. Vasospasm was re-induced by ergonovine provocation in 8 patients (Group-I) and not re-induced in 12 (Group-II) after treatment. In Group-I, improvement of decreased BMIPP uptake was lower than in Group-II (19+/-11 vs. 59+/-22%, mean+/-SD, p < 0.001). The regions in which vasospasm was re-provoked exhibited decreased BMIPP uptake. Abnormal fatty acid metabolism was more often observed than wall motion abnormality in the vasospastic region in patients with vasospastic angina. BMIPP scintigraphy is a highly accurate and non-invasive technique for determining the presence and location of vasospasm.

Consumption of vitamin E in coronary circulation in patients with variant angina

OBJECTIVES

The plasma status of vitamin E has been suggested to be linked to the activity of coronary artery spasm. This study was designed to determine whether vitamin E is actually consumed in the coronary circulation in patients with active variant angina having repetitive spasm-induced transient myocardial ischemia and reperfusion.

METHODS

Blood samples were obtained simultaneously from the aortic root, coronary sinus and right atrium in 12 patients with variant angina due to spasm of the left coronary artery, nine patients with stable effort angina and nine control subjects. Plasma vitamin E (alpha- and gamma-tocopherol) concentrations were determined by use of high-performance liquid chromatography and plasma lipid peroxides were measured as thiobarbituric acid-reactive substances (TBARS).

RESULTS

At baseline, both plasma alpha- (p < 0.01) and gamma- (p < 0.05) tocopherol levels were significantly lower in the coronary sinus (5.50 +/- 0.50 and 0.55 +/- 0.07 mg/l, mean +/- SEM) than in the aortic root (6.63 +/- 0.57 and 0.63 +/- 0.08 mg/l) and also in the right atrium (6.44 +/- 0.61 and 0.63 +/- 0.09 mg/l) in the variant angina group. The TBARS level was significantly (p < 0.05) higher in the coronary sinus than in the aortic in this group. In contrast, these levels were not significantly different between the samples from the coronary sinus and the aortic root or the right atrium in the control group and also in the stable effort angina group. The coronary sinus-aortic difference in plasma vitamin E levels in the variant angina group was not significantly altered after left coronary artery spasm induced by intracoronary injection of acetylcholine. Also, the plasma vitamin E levels in the aortic root, coronary sinus and right atrium all remained unchanged in the stable effort angina group after pacing-induced angina and in the control group after intracoronary administration of acetylcholine.

CONCLUSIONS

Transcardiac reduction in plasma vitamin E concentrations concomitant with lipid peroxide formation was demonstrated in patients with active variant angina, suggesting actual consumption of this major endogenous antioxidant. Oxidative stress and vitamin E exhaustion may be involved in the pathogenesis of coronary artery spasm.

High-density lipoprotein particles are large in patients with variant angina

OBJECTIVE

Dyslipidemia in patients with coronary vasospasm may be characterized by low level of high-density lipoprotein (HDL)-cholesterol as well as apolipoprotein (apo) A-I but not high level of low-density lipoprotein-cholesterol. This study sought to examine the HDL particle size in patients with variant angina.

METHODS

The HDL particle size was examined by analyzing serum lipid levels in 38 patients with variant angina to compare with those of 40 control subjects and 30 normocholesterolemic patients with stable effort angina. Also, actual HDL size distribution was assessed by electrophoresis.

RESULTS

The HDL-cholesterol, apoA-I and apoA-II levels were all lower (P < 0.01 for each) in patients with variant angina and patients with stable effort angina as compared with control subjects. The apoA-II level was lower (P < 0.01) in patients with variant angina than in patients with stable effort angina. The apoA-I/apoA-II ratio was lower (P < 0.01) in patients with stable effort angina, but not in patients with variant angina as compared with control subjects. In contrast, the HDL-cholesterol/apoA-I ratio was higher in patients with variant angina than in control subjects (P < 0.01) and also patients with stable effort angina (P < 0.01). The slope of the regression line, comparing HDL-cholesterol and apoA-I levels, was greater in patients with variant angina than in control subjects (P < 0.05) and patients with stable effort angina (P < 0.05), suggesting an increase in larger HDL particles. Native polyacrylamide gel electrophoresis revealed that HDL particles in patients with variant angina were skewed towards larger sizes compared with control subjects (P < 0.01) and patients with stable effort angina (P < 0.01). The abnormal serum lipid values were normalized in the patients with variant angina after the medical treatment and inactivation of the coronary spasm.

CONCLUSION

High HDL-cholesterol/apoA-I levels associated with low serum HDL-cholesterol and apoA-I levels were characteristic in patients with variant angina, in whom HDL particles were large, cholesterol-rich and possibly malfunctioning.

5-HT1Dbeta receptor mediates the supersensitivity of isolated coronary artery to serotonin in variant angina

Although serotonin (5-hydroxytryptamine; 5-HT) is used for provocation of coronary spasm, 5-HT receptor subtypes in spastic coronary arteries remain undetermined. We demonstrated the supersensitivity of isolated coronary artery to ergonovine, 5-HT, and sumatriptan, a 5-HT1D receptor agonist, in a patient with variant angina. Furthermore, we detected gene expression of 5-HT1Dbeta and 5-HT2A receptors in spastic coronary artery using RNase protection assay. These findings suggest that the leftward shift of the dose-response curve for 5-HT, which plays an important role in the pathogenesis of coronary spasm, is mediated by activation of 5-HT1Dbeta receptor.

Relation between severity of magnesium deficiency and frequency of anginal attacks in men with variant angina

OBJECTIVES

We evaluated whether the severity of magnesium deficiency was correlated with the frequency of attacks of variant angina.

BACKGROUND

Magnesium deficiency may be associated with the development of variant angina. However, the relation between the activity of variant angina and magnesium deficiency remains to be elucidated.

METHODS

We assessed the body magnesium status of 18 men with variant angina: Group 1 (> or = 4 attacks/week, n = 7) and Group 2 (< 4 attacks/week, n = 11). Concentrations of magnesium were determined in serum, urine, mononuclear cells and erythrocytes, and the 24-h magnesium retention rate was determined.

RESULTS

Group 1 showed a higher 24-h magnesium retention rate (mean +/- SEM 63.5 +/- 7.6% vs. 24.9 +/- 2.7%, p < 0.01) and a lower intracellular concentration of magnesium in mononuclear cells and erythrocytes than did Group 2 (respectively, 156.3 +/- 13.5 vs. 212.1 +/- 6.9 fg/cell, p < 0.01; and 3.5 +/- 0.5 vs. 5.2 +/- 0.4 fg/cell, p < 0.05), demonstrating the presence of magnesium deficiency in Group 1. The 24-h magnesium retention rate and intracellular concentrations of magnesium in mononuclear cells and erythrocytes correlated well with the frequency of anginal attacks (r = 0.78, p < 0.01; r = -0.78, p < 0.01; r = -0.62, p < 0.01, respectively) for all patients.

CONCLUSIONS

Data suggest that the magnesium status of men with variant angina is closely related to disease activity.

Basal release of endothelium-derived nitric oxide at site of spasm in patients with variant angina

OBJECTIVES

The aim of this study was to investigate the basal release of nitric oxide at spastic sites in patients with variant angina.

BACKGROUND

We previously reported that endothelium-dependent dilator responses to acetylcholine, substance P and bradykinin are preserved at the site of coronary artery spasm. However, it is not known whether the basal release of endothelium-derived nitric oxide is altered at the spastic site.

METHODS

The effects of intracoronary N(G)-monomethyl-L-arginine (L-NMMA, an inhibitor of nitric oxide synthesis) at cumulative doses of 50, 100 and 200 micromol on basal coronary artery tone were investigated in eight patients with variant angina and normal coronary angiograms and in eight control subjects. The lumen diameters of large epicardial coronary arteries were assessed by quantitative coronary arteriography.

RESULTS

Coronary spasm was provoked by the intracoronary administration of acetylcholine in all patients with variant angina. L-NMMA did not alter the arterial pressure and heart rate but significantly decreased the coronary artery diameter at spastic and nonspastic sites. Constrictive responses to L-NMMA were significantly greater (p < 0.01) at the spastic site (constriction by 200 micromol, 22+/-7%, mean +/- SD) than at the nonspastic site (10+/-7%). Constrictive responses to L-NMMA at the nonspastic site in patients with variant angina were comparable to those in the control subjects.

CONCLUSIONS

These findings support the hypothesis that the basal release of nitric oxide may not be decreased at the spastic site in patients with variant angina.

[Assessment of myocardial fatty acid metabolism in patients with vasospastic angina using 123I-BMIPP myocardial SPECT]

Myocardial perfusion and fatty acid metabolism may be unpaired in the patients of vasospastic angina (VSA), because abnormal regional wall motion of left ventricle has been shown in some cases of VSA without apparent history of myocardial infarction. To study the clinical utility of 123I-BMIPP scintigraphy in diagnosis of myocardial ischemia in VSA, both 123I-BMIPP (rest) and 201T1 (exercise) SPECT were performed in the 20 patients of VSA diagnosed by coronary angiography. Defect scores were calculated visually from the 17 segments of myocardial images and were compared with patient's anginal history, period from last attack, numbers of attack, left ventricular (LV) ejection fraction and severity of regional LV wall motion abnormality. 123I-BMIPP SPECT images showed decreased tracer uptake in 14 cases of 20 (70%) VSA patients. Exercise 201T1 SPECT images showed decreased tracer uptake in 3 cases of 20 (15%) of patients. Severity of regional LV wall motion abnormality was correlated with defect score of BMIPP. Though total defect score of BMIPP did not correlate with patient's anginal history, number of symptoms and LV ejection fraction, correlated inversely with period from last attack. It was suggested that 123I-BMIPP myocardial SPECT images in VSA patients showed "memories" of myocardial ischemic damages induced by vasospasm. In summary, 123I-BMIPP myocardial SPECT images could be a useful test for diagnosis and evaluation of VSA.

Platelet reactivity and its dependence on alpha-adrenergic receptor function in patients with ischaemic heart disease

We studied 57 patients admitted to hospital with ischaemic heart disease, including nine patients with variant angina, to evaluate platelet reactivity and its dependence on alpha-adrenergic receptor function. The threshold concentration for biphasic platelet aggregation in response to adrenaline and adenosine diphosphate was measured in fresh platelet rich plasma. There were age related alterations in platelet responsiveness to adrenaline. In 27 age matched control subjects platelets showed adrenaline induced aggregation at a concentration higher than 0.1 mumol. The threshold concentrations for adrenaline and adenosine diphosphate were 0.91 mumol and 4.68 mumol. In 16 patients with acute infarction, 14 with old infarction, nine with effort angina, and nine with rest angina, mean values of platelet aggregation threshold for both adrenaline and adenosine diphosphate were not altered significantly when compared with control subjects. In contrast, the values for adrenaline and adenosine diphosphate in nine patients with variant angina were 0.012 mumol and 2.24 mumol and seven of them showed obvious platelet hyperactivity to adrenaline at a concentration lower than 0.1 mumol. The threshold concentration for adrenaline induced aggregation did not correlate with serum cholesterol and triglyceride levels.

Rapid redistribution of thallium-201 post stress testing in a patient with variant angina

Reperfusion of an ischemic area after stress scanning with 201TI can occur rapidly and early scanning post stress testing is emphasized.

Cardiac prostaglandin release during myocardial ischemia induced by atrial pacing in patients with coronary artery disease

The relation between myocardial release of prostaglandin and myocardial ischemia was studied in 12 selected patients with multivessel coronary artery disease. These 12 were chosen for analysis because they experienced angina pectoris, ischemic electrocardiographic changes and decreased myocardial lactate uptake during atrial pacing. Simultaneous aortic and coronary sinus blood samples were obtained at rest, during angina and after recovery and were assayed for prostaglandins F, E and A with radioimmunoassay. Cardiac release of prostaglandin F was observed during angina in 11 of 12 patients. Aortic prostaglandin levels remained constant throught each study. During angina, the mean aortovenous difference (+/- standard error) was -0.30 +/- 0.04 ng/ml (P less than 0.001) for prostaglandin F and -0.10 +/- 0.03 ng/ml (Pless than 0.001) for prostaglandin E. There was no significant release of prostaglandin A. Blood samples were also drawn at subanginal heart rates in two patients. Prostaglandin F was released only during angina. In three control patients with a chest pain syndrome and normal coronary arteries, comparable atrial pacing produced no release of prostaglandin F, E or A. These results, together with the known vascular and metabolic actions of prostaglandins, suggest that these pharmacologically active compounds may also play a physiologic role in the cardiac response to ischemia in man.