Coronary artery spasm induced in miniature swine: angiographic evidence and relation to coronary atherosclerosis

Mechanisms of Coronary Artery Spasm

Recent clinical trials have highlighted that percutaneous coronary intervention in patients with stable angina provides limited additional benefits on top of optimal medical therapy. This has led to much more attention being paid to coronary vasomotion abnormalities regardless of obstructive or non-obstructive arterial segments. Coronary vasomotion is regulated by multiple mechanisms that include the endothelium, vascular smooth muscle cells (VSMCs), myocardial metabolic demand, autonomic nervous system and inflammation. Over the years, several animal models have been developed to explore the central mechanism of coronary artery spasm. This review summarises the landmark studies on the mechanisms of coronary vasospasm demonstrating the central role of Rho-kinase as a molecular switch of VSMC hypercontraction and the important role of coronary adventitial inflammation for Rho-kinase upregulation in VSMCs.

Coronary Artery Spasm-Related Heart Failure Syndrome: Literature Review

Although heart failure (HF) is a clinical syndrome that becomes worse over time, certain cases can be reversed with appropriate treatments. While coronary artery spasm (CAS) is still underappreciated and may be misdiagnosed, ischemia due to coronary artery disease and CAS is becoming the single most frequent cause of HF worldwide. CAS could lead to syncope, HF, arrhythmias, and myocardial ischemic syndromes such as asymptomatic ischemia, rest and/or effort angina, myocardial infarction, and sudden death. Albeit the clinical significance of asymptomatic CAS has been undervalued, affected individuals compared with those with classic Heberden's angina pectoris are at higher risk of syncope, life-threatening arrhythmias, and sudden death. As a result, a prompt diagnosis implements appropriate treatment strategies, which have significant life-changing consequences to prevent CAS-related complications, such as HF. Although an accurate diagnosis depends mainly on coronary angiography and provocative testing, clinical characteristics may help decision-making. Because the majority of CAS-related HF (CASHF) patients present with less severe phenotypes than overt HF, it underscores the importance of understanding risk factors correlated with CAS to prevent the future burden of HF. This narrative literature review summarises and discusses separately the epidemiology, clinical features, pathophysiology, and management of patients with CASHF.

Epicardial atherosclerosis and coronary tortuosity in patients with acetylcholine-induced coronary spasm

BACKGROUND

Angina pectoris in the absence of relevant epicardial stenoses is frequently caused by coronary spasm. This mechanism of angina is common yet underdiagnosed in daily clinical practice. The pathophysiology of coronary spasm is complex, multifactorial, and not completely understood. The purpose of this study was to analyze the relationship between macroscopic coronary morphologies and coronary spasm.

METHODS

Epicardial atherosclerosis, coronary vessel tortuosity, coronary aneurysms, and myocardial bridges were analyzed angiographically in 610 patients and a potential association with the result of an intracoronary acetylcholine (ACh) provocation test was investigated.

RESULTS

The comparison showed that angiographic morphologic variations in the coronary arteries are related to the occurrence of coronary spasm. We observed a strong association between the presence of epicardial atherosclerosis and epicardial spasm [87 patients of 179 with epicardial spasm had epicardial atherosclerosis (49%) vs. 45 patients of 172 with microvascular spasm (26%) vs. 89 patients of 259 with negative/inconclusive ACh test (36%); P < 0.005]. Moreover, we found a higher frequency of coronary tortuosity in patients with microvascular spasm [99 patients of 172 with microvascular spasm had at least moderate coronary tortuosity (58%) vs. 76 patients of 179 with epicardial spasm (43%) vs. 126 patients of 259 with negative/inconclusive ACh test (49%); P = 0.017]. Multivariable analysis revealed epicardial atherosclerosis (<50% stenosis) on coronary angiography as a predictor for epicardial spasm (OR, 2.096; 95% CI, 1.467-2.995; P < 0.0005). Female sex (OR, 5.469; 95% CI, 3.433-8.713; P < 0.0005), and exertional angina (OR, 2.411; 95% CI, 1.597-3.639; P < 0.0005) were predictors of microvascular spasm in multivariable analysis.

CONCLUSION

In angina patients with no obstructive coronary artery disease, epicardial atherosclerosis is associated with ACh-induced epicardial coronary spasm. Moreover, coronary microvascular spasm is more prevalent in female patients and those with exertional angina. Our results provide insights into the relationship between coronary morphology and coronary vasomotor function.

Effect of Epicardial Pulsed Field Ablation Directly on Coronary Arteries

BACKGROUND

The unique tissue selectivity of pulsed field ablation (PFA) allows for minimizing collateral damage to the nerves/esophagus. However, the safety profile of epicardial PFA on coronary arteries (CAs) has not been well defined.

OBJECTIVES

This study sought to evaluate the effect of epicardial PFA directly on CAs in a swine model.

METHODS

In 4 swine, an 8-F linear quadripolar PFA catheter (FARAPULSE Inc) was introduced into the pericardial space via a subxiphoid puncture. After coronary angiography (Angio), QRS synchronized, biphasic, bipolar PFA was delivered directly on the left anterior descending artery, left circumflex artery, or normal myocardium (control) (2.0 kV × 4 applications per site). Angio was repeated immediately after ablation and repeated every 5 minutes to quantify the degree of CA narrowing. After 4- or 8-week survival, repeat Angio was performed followed by gross and histologic lesion analyses.

RESULTS

A total of 15 lesions were delivered (8 left anterior descending arteries, 3 left circumflexes, and 4 controls). Target site Angio revealed median of 47% (IQR: 38%-69%) acute luminal narrowing immediately after PFA, which gradually resolved over 30 minutes. Epicardial PFA lesions extended into the myocardium with a median depth of 4.1 mm (IQR: 3.6-5.6 mm) passing across the CAs and adipose tissue. However, 87.5% of the CAs demonstrated minimal to mild CA stenosis associated with neointimal hyperplasia and tunica media fibrosis.

CONCLUSIONS

In a swine model, epicardial PFA directly on CAs allowed the creation of myocardial lesions but led to a CA response characterized by acute moderate spasm and chronic mild stenosis via neointimal hyperplasia.

Histological and Mechanical Behavior of INC 01 and 02 Bare Metal Stents Against a Commercial Stent: A Preclinical Study in a Porcine Model

BACKGROUND

PCI is an expensive procedure in our population and it implies a huge cost for the institutions and National Health Service.

AIM OF THE STUDY

The main objective was to evaluate the technical and biological success of two stents designed in Mexico.

METHODS

Ten York pigs, 4-6 months of age, underwent implantation of the bare metal INC-01 (10 stents) and INC-02 (6 stents) coronary stent in addition to a conventional commercial stent (10 stents). Technical success was evaluated immediately with angiography and Intravascular Ultrasound IVUS, continued by a mean follow-up of 4 month and a final angiographic, IVUS and histological evaluation.

RESULTS

Initial technical success, angiography and IVUS between the three stents were not significant. One stent presented restenosis in follow-up (commercial stent), but all other stents presented excellent clinical outcome, satisfactory angiographic and IVUS results. Inflammation, proliferation and endothelialization between the stents had no major differences in histological analysis in a mean of 4 months follow-up.

CONCLUSIONS

In this pig model, the INC 01 and INC 02 stents showed the same delivering technical success, angiographic and IVUS features, biological and histological response compared to commercial last generation stents.

Diagnostic Utility and Pathogenic Role of Circulating MicroRNAs in Vasospastic Angina

We investigated the diagnostic value and pathophysiological role of circulating microRNA (miR) in vasospastic angina (VA). We enrolled patients who underwent coronary angiography for chest pain to explore the miR’s diagnostic utility. In addition, we investigated the role of miRs in regulating endothelial nitric oxide synthase (eNOS) expression in human coronary artery endothelial cells (hCAECs). Among the 121 patients, 46 were diagnosed with VA (VA group), 26 with insignificant coronary lesions (ICL group), and 49 with atherothrombotic angina (AA group). The VA group showed a significantly higher expression of miR-17-5p, miR-92a-3p, and miR-126-3p than the ICL group. In contrast, miR-221-3p and miR-222-3p were upregulated in the AA group compared to the VA group, and all levels of miR-17-5p, miR-92a-3p, miR-126-3p, miR-145-5p, miR-221-3p, and miR-222-3p differed between the AA group and the ICL group. In the hCAECs, transfection with mimics (pre-miR) of miR-17-5p, miR-92a-3p, and miR-126-3p was associated with eNOS suppression. Additionally, transfection with inhibitors (anti-miR) of miR-92a-3p significantly rescued the eNOS suppression induced by lipopolysaccharide. In conclusion, the circulating miRs not only proved to have diagnostic utility, but also contributed to pathogenesis by eNOS regulation.

Effect of sarpogrelate and high-dose statin on the reduction of coronary spasm in vasospastic angina: A two by two factorial, pilot randomized study

Background

Vasospastic angina (VSA) is characterized by coronary spasm, which can be aggravated by vasoactive substances such as serotonin. Hypothesis Sarpogrelate, a selective serotonin receptor antagonist, and high‐dose statin have some effects on the reduction of coronary spasm in patients with VSA.

Methods

We recruited 100 patients with angiographically confirmed VSA, and randomly assigned them into four groups: sarpogrelate with high‐dose statin (Group A, n = 25), sarpogrelate with low‐dose or no statin (Group B, n = 25), placebo with high‐dose statin (Group C, n = 25), and placebo with low‐dose or no statin (Group D, n = 25). The primary endpoint was the remission of coronary spasm on 1‐year follow‐up provocation test.

Results

The most common site of coronary spasm was left anterior descending artery (42%). Most patients (96%) took calcium channel blockers, and 46% were treated with vasodilators. Overall, 40% of patients reported no chest pain at 1 year, and 23% showed complete remission of coronary spasm on 1‐year follow‐up provocation test. No difference was observed in symptomatic and angiographically complete remission rate between the sarpogrelate and the placebo group. Although the apolipoprotein B level at the 1‐year follow‐up was significantly lower in the high‐dose statin group, symptomatic and angiographic outcomes were not different according to statin intensity. Distal thrombolysis in myocardial infarction (TIMI) flow on initial provocation test was independently associated with angiographically complete remission.

Conclusions

Sarpogrelate or high‐dose statin did not significantly improve the angiographic remission rate in patients with VSA. Distal TIMI flow on initial provocation test could predict the complete remission of coronary spasm at follow‐up.

Catastrophic catheter-induced coronary artery vasospasm successfully rescued using intravascular ultrasound imaging guidance

A 46-year-old man underwent coronary angiography for stable angina. He developed inferior ST-segment myocardial infarction during the angiography. Intravascular ultrasound (IVUS) findings suggested coronary vasospasm. Intracoronary administration of isosorbide dinitrate restored the coronary flow. This case illustrates the essential role IVUS imaging played in establishing the diagnosis of catheter-induced coronary vasospasm.

High susceptibility of atherosclerotic coronary arteries to the onset of vasospasm and angina pectoris-like symptoms due to coronary spasm in WHHLMI rabbits

We examined the relationship between atherosclerosis and the provocation of coronary spasm as well as the influence of coronary spasm on the onset of acute ischemic myocardial disease. Coronary spasm was provoked in anesthetized normal Japanese white (JW) rabbits and myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits, an animal model for coronary atherosclerosis and myocardial infarction, by injecting ergonovine during the infusion of norepinephrine through a marginal ear vein. A decrease in contrast flow in the left circumflex artery was observed on coronary angiograms. Ischemic changes were observed on the electrocardiograms of 29% (2/7) of JW and 79% (27/34, P=0.007) of WHHLMI rabbits. The frequency of coronary spasm was significantly high in rabbits with severe coronary plaques showing diffuse lesions. Left ventricle motility in vasospasm-positive rabbits, which was evaluated with echocardiograms, was decreased by 29% following the ergonovine injection (P<0.001), and every serum ischemic marker markedly increased 4 h after the provocation of vasospasm. These results demonstrate that atherosclerotic coronary arteries are positively related to the provocation of vasospasm, and vasospasm in severe atherosclerotic coronary segments evokes angina pectoris-like findings and/or non-fatal myocardial infarction. WHHLMI rabbits may be a novel animal model for angina pectoris and acute ischemic heart disease.

2014 Williams Harvey Lecture: importance of coronary vasomotion abnormalities-from bench to bedside

Coronary vasomotion abnormalities play important roles in the pathogenesis of ischaemic heart disease, in which endothelial dysfunction and coronary artery spasm are substantially involved. Endothelial vasodilator functions are heterogeneous depending on the vessel size, with relatively greater role of nitric oxide (NO) in conduit arteries and predominant role of endothelium-derived hyperpolarizing factor (EDHF) in resistance arteries, where endothelium-derived hydrogen peroxide serves as an important EDHF. The functions of NO synthases in the endothelium are also heterogeneous with multiple mechanisms involved, accounting for the diverse functions of the endothelium in vasomotor as well as metabolic modulations. Cardiovascular abnormalities and metabolic phenotypes become evident when all three NO synthases are deleted, suggesting the importance of both NO and EDHF. Coronary artery spasm plays important roles in the pathogenesis of a wide range of ischaemic heart disease. The central mechanism of the spasm is hypercontraction of vascular smooth muscle cells (VSMCs), but not endothelial dysfunction, where activation of Rho-kinase, a molecular switch of VSMC contraction, plays a major role through inhibition of myosin light-chain phosphatase. The Rho-kinase pathway is also involved in the pathogenesis of a wide range of cardiovascular diseases and new Rho-kinase inhibitors are under development for various indications. The registry study by the Japanese Coronary Spasm Association has demonstrated many important aspects of vasospastic angina. The ongoing international registry study of vasospastic angina in six nations should elucidate the unknown aspects of the disorder. Coronary vasomotion abnormalities appear to be an important therapeutic target in cardiovascular medicine.

Coronary artery spasm: review and update

Coronary artery spasm (CAS), an intense vasoconstriction of coronary arteries that causes total or subtotal vessel occlusion, plays an important role in myocardial ischemic syndromes including stable and unstable angina, acute myocardial infarction, and sudden cardiac death. Coronary angiography and provocative testing usually is required to establish a definitive diagnosis. While the mechanisms underlying the development of CAS are still poorly understood, CAS appears to be a multifactorial disease but is not associated with the traditional risk factors for coronary artery disease. The diagnosis of CAS has important therapeutic implications, as calcium antagonists, not β-blockers, are the cornerstone of medical treatment. The prognosis is generally considered benign; however, recurrent episodes of angina are frequently observed. We provide a review of the literature and summarize the current state of knowledge regarding the pathogenesis of CAS.

Current advances in the understanding of coronary vasospasm

Recent years have witnessed progress in our understanding of coronary vasospasm (CVS). It is evident that this is not only an East Asian but also a global disease associated with significant symptoms and possible lethal sequelae for afflicted individuals. A correct diagnosis depends on the understanding of pathogenesis and symptomatology of CVS. With the correct diagnosis, we can manage CVS patients effectively and promptly, providing optimal patient safety. Advances in our understanding of interactions between inflammation, endothelium, and smooth muscle cells have led to substantial progress in understanding the pathogenesis of symptoms in CVS and have provided some insights into the basic etiology of this disorder in some patient subpopulations. We look forward to a time when therapy will address pathophysiology and perhaps, even the primary etiology.

Recent insights into the mechanisms of vasospastic angina

Coronary artery spasm plays an important role in the pathogenesis of many types of ischemic heart disease, not only in vasospastic angina but also in myocardial infarction and sudden death, particularly in the asian population. Patients with vasospastic angina are known to have defective endothelial function due to reduced nitric oxide bioavailability. Moreover, markers of oxidative stress and plasma levels of C-reactive protein are elevated. Smoking, polymorphysms of endothelial nitric oxide synthetase (eNOS), and low-grade inflammation have been regarded as the most important risk factors for vasospastic angina. The recent body of evidence indicates that RhoA and its down stream effector, ROCK/Rho-kinase, are associated with hypercontraction of vascular smooth muscle of the coronary artery and regulation of eNOS activity. Thus, endothelial dysfunction through abnormalities of eNOS and enhanced contractility of vascular smooth muscle in coronary artery segments are considered major mechanisms in vasospastic angina. However, the precise mechanisms for coronary vasospasm are not well understood. This article will review current understanding of the mechanism of coronary artery spasm.

Plaque components at coronary sites with focal spasm in patients with variant angina: virtual histology-intravascular ultrasound analysis

BACKGROUND

We compared the plaque components at coronary sites with focal spasm after ergonovine provocation test in 30 variant angina (VA) patients with those at culprit coronary sites in 32 unstable angina (UA) patients using virtual histology-intravascular ultrasound (VH-IVUS).

METHODS

VH-IVUS classified and color-coded tissue into four major components: fibrotic; fibro-fatty; dense calcium (DC); and necrotic core (NC). Thin-cap fibroatheroma (TCFA) was defined as a NC≥10% of plaque area in at least 3 consecutive frames without overlying fibrous tissue in the presence of ≥40% plaque burden.

RESULTS

The lesion site plaque burden was significantly smaller (44.5±10.8% vs. 70.5±13.1%, p<0.001), the plaque volume was significantly smaller (135±118 mm³ vs. 223±160 mm³, p=0.020), the remodeling index was significantly lower (0.90±0.14 vs. 0.97±0.23, p=0.023), and more plaque was hypoechoic with less calcium (87% vs. 56% and 0% vs. 19%, respectively, p=0.033) in VA patients compared with UA patients. The % NC and DC areas were significantly smaller at the minimum lumen site within spasm/culprit lesion (12.9±12.9% vs. 22.3±11.7%, p=0.004, and 6.5±8.0% vs. 12.8±10.8%, p=0.011, respectively), and the % NC and DC volumes were significantly smaller in VA patients compared with UA patients (12.2±10.3% vs. 17.7±8.1%, p=0.025, and 6.4±6.0% vs. 11.8±8.5%, p=0.007, respectively). The TCFA within lesion segments was less frequently observed in VA patients compared with UA patients (13% vs. 53%, p=0.001).

CONCLUSIONS

VA patients have less plaque, more negative remodeling behavior, more hypoechoic plaque with less calcification, and less NC- and DC-containing lesions and less TCFA lesions compared with UA patients.

Intermediate fixed coronary artery stenosis at the site of ergonovine-provoked spasm as a predictor of long-term major adverse cardiac events of patients with coronary spastic angina

BACKGROUND

Organic coronary artery stenosis is a significant prognostic factor in patients with coronary spastic angina (CSA), so the present study was focused on assessing the impact of intermediate fixed stenosis at sites of provoked spasm on the long-term outcomes of CSA patients.

METHODS AND RESULTS

CSA patients diagnosed on the basis of ergonovine-provoked spasm were enrolled and the clinical background and long-term prognosis of CSA patients with intermediate fixed stenosis at the site of provoked spasm (with-fixed-stenosis group, n=37) and those without fixed stenosis (without-fixed-stenosis group, n=126) were retrospectively compared. During the follow-up period (average 4.01 years for with-fixed-stenosis, 4.47 years for without-fixed-stenosis), the with-fixed-stenosis group had a significantly lower event-free survival rate, as well as a higher frequency of admission for unstable angina and percutaneous coronary intervention than the without-fixed-stenosis group, whereas the survival rate did not differ significantly between the 2 groups. In the multivariate analysis, intermediate fixed stenosis at the site of provoked spasm was a predictor of long-term major adverse cardiac events (MACE).

CONCLUSIONS

Intermediate fixed stenosis at the site of ergonovine-provoked spasm is an independent risk factor for MACE during the long-term period in CSA patients.

Impact of oxidized low density lipoprotein on vascular cells

Oxidized LDL (OxLDL) is a proatherogenic lipoprotein, accumulating in the vascular wall and contributing to the pathogenesis of vascular dysfunction early in the development of atherosclerosis. Enhanced serum levels of OxLDL, as well as antibodies against its epitopes, are predictive for endothelial dysfunction and coronary heart disease. While enhanced oxidative stress is one factor triggering formation of OxLDL, OxLDL itself has been identified as a potent stimulus for vascular oxygen radical formation, causing a vicious circle. OxLDL-induced O(2)(-) formation, largely through activation of NADPH oxidase, but also through uncoupling of endothelial NO-synthase and through direct O(2)(-) release, leads to endothelial dysfunction. Furthermore, OxLDL-induced O(2)(-) formation has a strong impact on tissue remodeling, resulting in either cell growth - proliferation or hyperplasia - or apoptotic cell death. The effect of OxLDL on cell cycle regulation is mediated by activation of the small GTPase RhoA and consequent regulation of p27(KIP1), a key enzyme of the cell cycle. In addition, OxLDL-induced activation of RhoA sensitizes the contractile apparatus of the vessel wall, enhancing the contractile tonus and favoring vasospasm. Thus, through a variety of mechanisms, OxLDL importantly contributes to vascular dysfunction and remodeling.

Coronary vasospasm and the regulation of coronary blood flow

Under physiologic conditions, epicardial arteries contribute minimally to coronary vascular resistance. However, in the presence of endothelial dysfunction, stimuli that normally produce vasodilation may instead cause constriction. Examples include neural release of acetylcholine or norepinephrine, platelet activation and production of serotonin and thrombin, and release of local factors such as bradykinin. This shift from a primary endothelial-mediated vasodilator influence to one of endothelial dysfunction and unchecked vasoconstriction is precisely the milieu in which coronary vasospasm is observed. This condition, which typically occurs during periods of relatively sedentary activity, is associated with focal and transient obstruction of an epicardial arterial segment resulting in characteristic echocardiographic changes and symptoms of myocardial ischemia. This review highlights the current understanding of mechanisms regulating the coronary circulation during health and examines the pathophysiologic changes that occur with coronary spasm. Genetic and other predisposing conditions are addressed, as well as novel therapies based on recent mechanistic insights of the coronary contractile dysfunction associated with coronary spasm.

Evidence for protein kinase C-mediated activation of Rho-kinase in a porcine model of coronary artery spasm

OBJECTIVE

We have recently demonstrated that protein kinase C (PKC) and Rho-kinase play important roles in coronary vasospasm in a porcine model. However, it remains to be examined whether there is an interaction between the two molecules to cause the spasm.

METHODS AND RESULTS

A segment of left porcine coronary artery was chronically treated with IL-1beta-bound microbeads in vivo. Two weeks after the operation, phorbol ester caused coronary spasm in vivo and coronary hypercontractions in vitro at the IL-1beta-treated segment; both were significantly inhibited by hydroxyfasudil, a specific Rho-kinase inhibitor. Guanosine 5'-[gamma-thio]triphosphate (GTPgammaS), which activates Rho with a resultant activation of Rho-kinase, enhanced Ca2+ sensitization of permeabilized vascular smooth muscle cells, which were resistant to the blockade of PKC by calphostin C. The GTPgammaS-induced Ca2+ sensitization was greater in the spastic segment than in the control segment. Western blot analysis revealed that only PKCdelta isoform was activated during the hypercontraction.

CONCLUSIONS

These results demonstrate that PKC and Rho-kinase coexist on the same intracellular signaling pathway, with PKC located upstream on Rho-kinase, and that among the PKC isoforms, only PKCdelta may be involved. Thus, the strategy to inhibit Rho-kinase rather than PKC may be a more specific and useful treatment for coronary spasm.

Oxidized LDL and its compound lysophosphatidylcholine potentiate AngII-induced vasoconstriction by stimulation of RhoA

RhoA stimulates vascular tone by increasing smooth muscle Ca(2+) sensitivity, e.g., in atherosclerosis. This study was an investigation of the influence of oxidized LDL (OxLDL), which accumulates in atherosclerotic plaques, on vascular tone induced by angiotensin II (AngII), with particular emphasis on the RhoA pathway. OxLDL had no influence on unstimulated vascular tone of isolated rabbit aorta, but it potentiated contractile responses induced by AngII. The Ca(2+)-antagonist felodipin partially prevented potentiation of contractile responses, whereas the AT(1) receptor antagonist losartan blunted AngII responses in presence and in absence of OxLDL. Rho-kinase inhibition by Y27632 abolished potentiation of contractile responses, and RhoA inhibition by C3-like transferase partially prevented it, suggesting that OxLDL activated RhoA. Activation of RhoA was further analyzed by detection of its translocation to the cell membrane after stimulation with OxLDL. Western blot analysis of aorta homogenates, as well as direct visualization in cultured smooth muscle cells using confocal laser scan microscopy, revealed that OxLDL potently activated RhoA. The effect of OxLDL was mimicked by its compound lysophosphatidylcholine, and C3 inhibited both lysophosphatidylcholine and OxLDL-induced RhoA stimulation. In conclusion, OxLDL stimulates the RhoA pathway, resulting in potentiation of AngII-induced vasoconstriction. Lysophosphatidylcholine mimics the OxLDL effect, consistent with a causal role of this OxLDL compound. Stimulation of RhoA by OxLDL may contribute to vasospasm in atherosclerotic arteries.

Lesion Severity and Hypercholesterolemia Determine Long-Term Prognosis of Vasospastic Angina Treated With Calcium Channel Antagonists

Although patients with medically treated vasospastic angina have a good outcome, few data exist regarding the role of underlying lesion severity associated with or without hyperlipidemia in the prognosis. Therefore, the aim of the present study was to assess the relationship between the long-term outcome of vasospastic angina and the factors influencing its prognosis. A total of 256 patients (219 men, 37 women; mean age, 54.1+/-9.2) who had coronary spasm with or without underlying lesions and were being treated with calcium channel antagonists were enrolled and followed for 13.6+/-3.7 years. Cardiac events consisted of cardiac death and ischemic events, which included acute myocardial infarction and unstable angina. Cox analysis selected coronary artery stenosis (CAS, >/=50%) and risk factors such as age, hypertension, diabetes mellitus, low-density lipoprotein-cholesterol (LDL-C), sex and smoking. There were 19 cases of cardiac death (7.4%) and 58 of ischemic events (22.7%) during the follow-up period. The presence of significant CAS was an independent predictor of event-free survival (hazard ratio (HR) =2.84, 95% confidence interval (CI) =1.79-4.52, p<0.0001). In 193 patients without significant CAS, there were 10 cases of cardiac death (5.2%, p<0.05) and 34 of ischemic events (17.6%, p<0.01). In that group, high LDL-C was the independent predictor of event-free survival (HR = 3.89, 95% CI = 1.20-12.6, p=0.02). Kaplan-Meier survival analysis revealed significantly lower event-free survival in patients with than in those without lesions (p<0.0001 by log-rank test). These results demonstrate that the most important factor for long-term prognosis of vasospastic angina treated with calcium channel antagonists is significant CAS. High LDL-C, which might alter the underlying coronary endothelial function and/or accelerate atherosclerotic lesions, could also contribute to the occurrence of cardiac events, particularly in patients without significant CAS.

Plaque Morphology at Coronary Sites With Focal Spasm in Variant Angina-Study Using Intravascular Ultrasound-

In the present study, the intravascular ultrasound (IVUS) morphologic appearance of coronary atherosclerotic plaque associated with focal spasm was prospectively studied in 45 patients with or without focal coronary spasm provoked by ergonovine or acetylcholine. The percent plaque area and plaque arc were determined from the IVUS images at the sites of spasm. Calcified lesion was defined as the presence of high-intensity echo with acoustic shadowing. Twenty-three patients had focal coronary spasm defined as angiographic narrowing >75% and IVUS demonstrated atherosclerotic plaque in these 23 sites. In the 22 patients without focal spasm, IVUS demonstrated 18 atherosclerotic lesions in 17 patients and the remaining 5 patients did not have significant lesions. There was no difference in the percent plaque area and plaque arc between plaque lesions with (47+/-10%, 298+/-71 degrees ) and without (39+/-15%, 249+/-83 degrees ) coronary spasm. Interestingly, calcified lesion was less frequently present at the sites with than at those without spasm (p<0.05). These results indicate that the presence of plaque without calcification is likely to be related to the occurrence of focal vasospasm, although the severity and distribution of the disease did not differ between each patient group.

Our animal model of coronary spasm--my personal view

We developed an animal model of coronary spasm in swine, similar to coronary spasm in patients with variant angina based on the angiographic findings. In this animal model, an impairment of endothelium dependent dilatation appeared to play a minor role while the hypercontraction of the medial muscle cells by histamine and serotonin at the spastic site played a major role in the induction of coronary spasm. In Göttingen male miniature swine receiving focal endothelial denudation, moderate hypercholesterolemia and X ray irradiation, the abrupt, severe and prolonged coronary spasm resulted in a sudden progression of organic coronary stenosis mainly due to intraplaque hemorrhage and also in acute myocardial infarction.

Intravascular ultrasound findings of negative arterial remodeling at sites of focal coronary spasm in patients with vasospastic angina

BACKGROUND

There are few data about the intravascular ultrasound (IVUS) findings in patients with vasospastic angina, especially regarding patterns of vascular remodeling.

METHODS AND RESULTS

Coronary spasm was documented by angiography and electrocardiographic evidence of ischemia in 36 patients after administration of ergonovine (cumulative doses up to 350 microg). After relief of spasm with 1000 microg of intracoronary nitroglycerin, quantitative angiography and IVUS imaging were performed and analyzed by standard methods. The 36 focal spasm sites were compared with the proximal and distal reference segments. The angiographic baseline minimum lumen diameter measured 1.78 +/- 0.66 mm, which decreased to 0.66 +/- 0.38 mm with ergonovine provocation (P <.0001), increased to 2.66 +/- 0.64 mm after intracoronary nitroglycerin (P <.0001 compared with baseline and after ergonovine), and did not change after IVUS imaging (2.66 +/- 0.63, P =.9). By IVUS, atherosclerotic lesions were observed at all coronary spasm sites; the mean plaque burden measured 56% at the spasm site and 35% at the reference. Spasm site plaque composition was hypoechoic in 31 and hyperechoic, noncalcific in 5; there was no calcium. The mean eccentricity index (maximum divided by minimum plaque thickness) was 6.7. Positive remodeling (spasm site arterial area greater than proximal reference) was present in 5; intermediate remodeling (proximal reference greater than spasm site greater than distal reference arterial area) was present in 7; and negative remodeling (spasm site arterial area less than distal reference) was present in 24.

CONCLUSIONS

Sites of vasospasm in patients with variant angina showed characteristics of early atherosclerosis, except for an unusually high incidence of negative arterial remodeling.

Increased expression of L-type calcium channels in vascular smooth muscle cells at spastic site in a porcine model of coronary artery spasm

Coronary artery spasm is caused primarily by increased contractility of vascular smooth muscle. Excessive Ca2+ entry into vascular smooth muscle cells (VSMCs) may be one of the key mechanisms for the spasm, but no study has ever directly examined the possible alterations of Ca2+ channels in the spastic coronary artery. Here we show that L-type Ca2+ channels are excessively expressed at the spastic site of the coronary artery. In a porcine model of coronary spasm with balloon injury, both receptor-mediated stimulation of L-type Ca2+ channels by serotonin and direct stimulation of the channels by Bay K 8644 (a dihydropyridine Ca2+ channel agonist) repeatedly induced coronary spasm in vivo, which was abolished by pretreatment with nifedipine, a dihydropyridine Ca2+ channel antagonist. In a single VSMC freshly dispersed from coronary arteries in vitro, patch-clamp experiments showed that current density of L-type Ca2+ channel current was significantly increased in VSMCs from the spastic site compared with that from the control site even when the channels were maximally stimulated by Bay K 8644. There was no difference in the sensitivity of the channels to Bay K 8644. These results indicate that functionally available L-type Ca2+ channels are excessively expressed at the spastic site of the coronary artery in our porcine model, suggesting that increased expression of L-type Ca2+ channels and concomitant increase in Ca2+ entry into VSMCs through the channels may contribute, at least in part, to the pathogenesis of coronary artery spasm.

Inhibition of myosin phosphatase by upregulated rho-kinase plays a key role for coronary artery spasm in a porcine model with interleukin-1beta

BACKGROUND

We recently demonstrated that the Rho-kinase-mediated pathway plays an important role for coronary artery spasm in our porcine model with interleukin-1beta (IL-1beta). In this study, we examined whether or not Rho-kinase is upregulated at the spastic site and if so, how it induces vascular smooth muscle hypercontraction.

METHODS AND RESULTS

Segments of the left porcine coronary artery were chronically treated from the adventitia with IL-1beta-bound microbeads. Two weeks after the operation, as reported previously, intracoronary serotonin repeatedly induced coronary hypercontractions at the IL-1beta-treated site both in vivo and in vitro, which were markedly inhibited by Y-27632, one of the specific inhibitors of Rho-kinase. Reverse transcription-polymerase chain reaction analysis demonstrated that the expression of Rho-kinase mRNA was significantly increased in the spastic compared with the control segment. Western blot analysis showed that during the serotonin-induced contractions, the extent of phosphorylation of the myosin-binding subunit of myosin phosphatase (MBS), one of the major substrates of Rho-kinase, was significantly greater in the spastic than in the control segment and that the increase in MBS phosphorylations was also markedly inhibited by Y-27632. There was a highly significant correlation between the extent of MBS phosphorylations and that of contractions.

CONCLUSIONS

These results indicate that Rho-kinase is upregulated at the spastic site and plays a key role in inducing vascular smooth muscle hypercontraction by inhibiting myosin phosphatase through the phosphorylation of MBS in our porcine model.

Cellular and molecular mechanisms of coronary artery spasm: lessons from animal models

Coronary artery spasm plays an important role in the pathogenesis of a wide variety of ischemic heart diseases, especially in the Japanese population. Because coronary artery spasm can be induced by a variety of stimuli with different mechanisms of action, the occurrence of the spasm appears to be due to the local hyperreactivity of the coronary artery rather than to an enhanced stimulation with a single mechanism of action. Several lines of evidence indicate that coronary artery spasm is caused primarily by smooth muscle hypercontraction whereas the contribution of endothelial dysfunction may be minimal. In order to elucidate the cellular and molecular mechanisms of the spasm, porcine models of the spasm were developed. In the first model with balloon injury and high-cholesterol feeding, a close topological correlation between the early atherosclerotic lesions and the spastic sites was noted, whereas in the second model with an inflammatory cytokine the potential importance of coronary inflammatory changes, especially at the adventitia, was noted. Subsequent studies in vivo and in vitro demonstrated that protein kinase C (PKC) and Rho-kinase are substantially involved in the intracellular mechanism of the spasm, resulting in increases in the mono- and diphosphorylations of myosin light chain (MLC). Furthermore, molecular biological analyses demonstrated that Rho-kinase is upregulated at the spastic site (at all levels, including mRNA, protein, and activity), resulting in the inhibition of MLC phosphatase through the phosphorylation of its myosin binding subunit and thereby causing the increase in MLC phosphorylations. Preliminary results also suggest that the long-term inhibition of Rho-kinase is effective in inhibiting the development of arteriosclerotic vascular lesions in several porcine models. Thus, Rho-kinase could be regarded as a novel therapeutic target for coronary arteriosclerosis in general and coronary artery spasm in particular.

Endothelial vasodilator function is preserved at the spastic/inflammatory coronary lesions in pigs

BACKGROUND

The question of whether or not endothelial vasodilator function in the spastic coronary artery is preserved is still controversial. We recently developed a porcine model in which long-term and local treatment with interleukin-1beta (IL-1beta) from the adventitial site causes coronary arteriosclerotic changes and vasospastic responses to autacoids. The aim of this study was to examine the endothelial vasodilator function in our new porcine model of the spasm both in vivo and in vitro.

METHODS AND RESULTS

A segment of the porcine coronary artery was aseptically wrapped with cotton mesh that held absorbed IL-1beta-bound microbeads. Two weeks after the procedure, intracoronary administration of serotonin caused coronary vasospasm at the IL-1beta-treated site (n = 10). Coronary vasodilatation to bradykinin, substance P, or an increase in coronary blood flow was preserved at the spastic site. Vasodilator responses to 3-morpholinosydnonimine (an NO donor) and nitroglycerin also were comparable between the 2 sites. The vasoconstricting response to N(G)-monomethyl-L-arginine and the extent of the augmentation of the serotonin-induced vasoconstriction were comparable between the 2 sites. Organ chamber experiments showed that endothelium-dependent relaxations to bradykinin, the calcium ionophore A23187, and even the vasospastic agonist serotonin were preserved at the spastic site, whereas contractions to serotonin were augmented at the spastic site regardless of the presence or absence of the endothelium (n = 6). Endothelium-independent relaxations to sodium nitroprusside were also preserved at the spastic site.

CONCLUSIONS

These results indicate that endothelial vasodilator function is preserved at the spastic site and that the spasm is caused primarily by smooth muscle hypercontraction in our porcine model.

Vasculoprotective role of inducible nitric oxide synthase at inflammatory coronary lesions induced by chronic treatment with interleukin-1beta in pigs in vivo

BACKGROUND

We recently developed a porcine model in which chronic, local treatment with interleukin-1beta (IL-1beta) causes coronary arteriosclerotic changes and hyperconstrictive responses. Inflammatory cytokines are known to induce inducible NO synthase (iNOS) in the vascular smooth muscle. This study was designed to examine whether or not the production of NO by iNOS has a protective or deleterious effect on the coronary artery in vivo.

METHODS AND RESULTS

A segment of the porcine coronary artery was aseptically wrapped with cotton mesh absorbing IL-1beta suspension. We inhibited both eNOS and iNOS activity by cotreatment with L-NAME (a nonspecific inhibitor of NOS) and iNOS activity alone by aminoguanidine (a selective inhibitor of iNOS). Immunostaining showed that iNOS was absent in the normal coronary artery, whereas it was highly expressed 1 day after the application of IL-1beta and thereafter downregulated until 14 days. In contrast, eNOS was well maintained throughout the study period. Two weeks after the operation, hyperconstrictive responses to intracoronary serotonin and neointimal formation were noted at the IL-1beta-treated site, and both responses were significantly greater at the site cotreated with either L-NAME or aminoguanidine.

CONCLUSIONS

These results indicate that iNOS is transiently induced in vivo in response to local inflammation and that NO produced by iNOS exerts an inhibitory effect against the cytokine-induced proliferative/vasospastic changes of the coronary artery in vivo.

Tyrosine kinase inhibitor markedly suppresses the development of coronary lesions induced by long-term treatment with platelet-derived growth factor in pigs in vivo

Platelet-derived growth factor (PDGF) plays an important role in the development of coronary atherosclerosis. However, it remains to be examined what morphologic and functional changes are induced in vivo by the long-term treatment with PDGF itself or what pharmacologic interventions could suppress those changes in vivo. Our study was designed to address these points. We examined the effects of long-term treatment with PDGF on the porcine coronary artery in vivo. Under aseptic conditions, the proximal segments of the left porcine coronary artery were gently wrapped with cotton mesh absorbing sepharose beads either with or without recombinant human PDGF-AA or -BB. Two weeks after the operation, coronary hyperconstrictions to intracoronary serotonin or histamine were noted at the sites treated with PDGF-AA or -BB. Histologically, neointimal formation and geometric remodeling (reduction of the total vessel area) were noted at the PDGF-treated sites. These functional and histologic changes of the coronary artery induced by PDGF were markedly inhibited by cotreatment with ST 638, a specific inhibitor of tyrosine kinases. A Western blot analysis showed that ST 638 markedly suppressed the PDGF-induced tyrosine phosphorylations in the coronary segment. These results indicate that long-term treatment with PDGF induces neointimal formation, geometric remodeling, and vasospastic responses in vivo, for all of which, activation of tyrosine kinases is substantially involved.

Inflammatory cytokines cause coronary arteriosclerosis-like changes and alterations in the smooth-muscle phenotypes in pigs

We recently developed a porcine model in which chronic, local treatment with interleukin-1 beta (IL-1 beta) causes coronary arteriosclerosis-like changes and hyperconstrictive responses. This study was designed to examine whether or not other major inflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha) might also cause similar coronary responses and whether those responses are associated with alterations in the smooth-muscle phenotypes. A segment of the porcine coronary artery was aseptically wrapped with cotton mesh, absorbing IL-1 beta, TNF-alpha, and IL-1 alpha. Two weeks after the operation, coronary arteriography showed the development of mild stenotic lesions at the cytokine-treated sites, where hyperconstrictive responses were repeatedly induced by intracoronary serotonin or histamine. Histologically mild intimal thickening was noted at those cytokine-treated sites. Immunostaining and immunoblotting demonstrated that all three myosin heavy chain isoforms, SM1, SM2 (smooth-muscle type), and SMemb (nonmuscle type), were noted in the normal coronary segments, whereas in the segments treated with inflammatory cytokines, SM1 and SM2 were markedly reduced, and only SMemb was noted. These results indicate that inflammatory cytokines all have a similar ability to induce coronary arteriosclerosis-like changes and hyperconstrictive responses, which are associated with alterations in smooth-muscle phenotypes toward dedifferentiation.

Coronary artery spasm does not depend on the intracellular calcium store but is substantially mediated by the protein kinase C-mediated pathway in a swine model with interleukin-1 beta in vivo

BACKGROUND

The intracellular mechanism for coronary artery spasm is still unknown. Since the protein kinase C (PKC)-mediated pathway and Ca2+ release from sarcoplasmic reticulum (SR) are important intracellular mechanisms of vascular smooth muscle contraction, we examined the possible role of these two mechanisms in the pathogenesis of coronary spasm in our swine model in vivo.

METHODS AND RESULTS

In 25 pigs, interleukin-1 beta (IL-1 beta) was applied chronically to the coronary arteries from the adventitia to induce an inflammatory/proliferative lesion. Two weeks after the operation, either intracoronary serotonin or histamine repeatedly induced coronary spasm at the IL-1 beta-treated site. At those spastic sites, phorbol-12, 13-dibutyrate, a PKC-activating phorbol ester, also induced coronary spasm, which was blocked by pretreatment with the PKC inhibitors staurosporine and sphingosine. Serotonin- and histamine-induced coronary spasm was also significantly inhibited by pretreatment with staurosporine, sphingosine, or nifedipine (an L-type Ca2+ channel antagonist) but not by ryanodine (an inhibitor of Ca(2+)-induced Ca2+ release from SR) or thapsigargin (an inhibitor of Ca(2+)-ATPase of SR). Bay K 8644 (an L-type Ca2+ channel agonist) also induced coronary spasm at the IL-1 beta-treated site, which was significantly inhibited by pretreatment with staurosporine, sphingosine, and nifedipine. In contrast, coronary vasoconstriction induced by prostaglandin F2 alpha was not affected by pretreatment with staurosporine or sphingosine but was significantly inhibited by pretreatment with ryanodine, thapsigargin, or nifedipine.

CONCLUSIONS

These results suggest that (1) PKC activation largely accounts for the serotonin- and histamine-induced coronary spasm; (2) at the spastic site, the calcium influx through L-type Ca2+ channels may be augmented via the PKC-mediated pathway; and (3) the Ca2+ release from the SR into the cytosol may not play a primary role in coronary spasm.

Chronic treatment with interleukin-1 beta induces coronary intimal lesions and vasospastic responses in pigs in vivo. The role of platelet-derived growth factor

Studies in vitro have suggested that inflammatory cytokines may play an important role in the pathogenesis of atherosclerosis. However, little is known about their effects in vivo. Thus, the present study was designed to determine in vivo what histological and functional changes may be induced by chronic treatment with IL-1 beta, one of the major inflammatory cytokines, and also to clarify what mechanisms are involved in those changes. Under aseptic conditions, proximal segments of the left porcine coronary arteries were gently wrapped with cotton mesh absorbing Sepharose beads either with or without recombinant human IL-1 beta. From 1 to 4 wk after the operation, coronary vasospastic responses to intracoronary serotonin or histamine were noted at the IL-1 beta-treated site but not at the control site. Histologically, intimal thickening was greater at the IL-1 beta-treated site than at the control site. Those functional and histological changes induced by the chronic treatment with IL-1 beta were significantly inhibited by the simultaneous treatment with a neutralizing antibody to either IL-1 beta or PDGF. These results indicate that chronic treatment with Il-1 beta induces coronary intimal lesions and vasospastic responses in porcine coronary arteries in vivo and also suggest that these changes are substantially mediated by PDGF.

Fluctuation of spastic location in patients with vasospastic angina: a quantitative angiographic study

OBJECTIVES

This study sought to determine whether the location of coronary spastic activity may change over time in patients with persistent variant angina.

BACKGROUND

Although electrocardiographic studies have provided indirect evidence to indicate that the location of ischemia may change in patients with variant angina, it has not been tested by quantitative angiography whether the location of vasospastic activity may change over time.

METHODS

Paired ergonovine provocation tests and coronary angiography were performed at a mean (+/- SD) interval of 43 +/- 13 months apart in patients with persistent symptoms of vasospastic angina in the absence of significant atherosclerosis. A total of 87 spastic and nonspastic segments of 87 major vessels in 29 patients were analyzed by quantitative angiography at baseline, after the administration of ergonovine and after isosorbide dinitrate at the initial and follow-up tests.

RESULTS

In 13 patients (group 1), coronary spasm was observed in the same 16 coronary segments at both the initial and follow-up ergonovine provocation tests. In 16 patients (group 2), the following angiographic changes occurred between the initial and follow-up tests in 48 major vessels: Of the 23 segments that developed spasm at the initial test, 10 did not have spasm at the follow-up test; of the 25 vessels that did not demonstrate spasm on the initial test, 12 demonstrated spasm on the follow-up test (a new site of spasm). Thus, in 22 (46%) of 48 vessels, fluctuation of spastic location was observed at follow-up.

CONCLUSIONS

Quantitative coronary angiography and repeated ergonovine tests revealed that some patients with persistent vasospastic angina demonstrate fluctuation of vasospastic location, whereas others exhibit a fixed location of vasospasm. Vasospastic angina may not only be a transient disease restricted in location, but may also be a persistent and variable condition involving multiple vessels over many years.

Comparison of vessel wall morphologic appearance at sites of focal and diffuse coronary vasospasm by intravascular ultrasound

Coronary vasospasm is manifested by either focal or diffuse pattern in clinical settings. To examine the differences in vessel wall morphologic appearance between the sites of focal and diffuse vasospasm, we studied 29 patients with chest pain at rest, during exertion, or both by intravascular ultrasound. By angiography, focal vasospasm with diameter reduction of 90% +/- 3% (mean +/- SD) was provoked by intracoronary ergonovine (0.01 to 0.04 mg) in 15 patients. Diffuse vasospasm with diameter reduction of 79% +/- 5% (NS) was provoked in seven patients, and the remaining seven patients served as the control group. By ultrasonography, a significantly thickened intimal leading edge with sonolucent zone was observed in 55 sites from 22 coronary arteries with either focal or diffuse vasospasms (0.61 +/- 0.32 mm), although these sites were normal or minimally narrowed by angiography. Seven segments from the control group exhibited a thin intimal leading edge with sonolucent zone (0.23 +/- 0.08 mm, p < 0.01). When the thickness of the intimal leading edge with sonolucent zone was compared between the abnormal sites with focal and diffuse vasospasm, this was significantly greater at focal spasm, 1.01 +/- 0.35 mm (n = 15), than that at diffuse spasm, 0.46 +/- 0.13 mm (n = 40, p < 0.01). At the sites with diffuse spasm, some of the lesions lay scattered along the coronary vessels, although the lesions were localized at the sites of focal vasospasm. These results indicate that atherosclerosis is present at sites with both focal and diffuse vasospasm even in the absence of angiographically significant coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Tyrosine kinase inhibitor suppresses coronary arteriosclerotic changes and vasospastic responses induced by chronic treatment with interleukin-1 beta in pigs in vivo

We recently demonstrated that chronic treatment with IL-1 beta induces coronary arteriosclerotic changes and vasospastic responses to autacoids in pigs in vivo and that those responses are importantly mediated by PDGF. The receptors for PDGF and other major growth factors are known to have tyrosine kinase activity. We therefore investigated the effects of a selective tyrosine kinase inhibitor, ST 638, on those responses induced by IL-1 beta in our swine model. Intimal thickening and coronary vasospastic responses to serotonin and histamine were induced at the site of the coronary artery where IL-1 beta was chronically and locally applied. These responses were significantly suppressed in a dose-dependent manner by cotreatment with ST 638. In addition, ST 494, which is an inactive form of ST 638, did not inhibit those responses. The treatment with ST 638 alone did not affect the coronary vasoconstricting responses to the autacoids. Immunoblotting using an antibody to phosphotyrosines confirmed the inhibitory effects of ST 638 on the tyrosine phosphorylations induced by IL-1 beta. These results thus suggest that tyrosine kinase activation may play an important role in mediating the effects of IL-1 beta, while also suggesting that ST 638 has an inhibitory effect on the arteriosclerotic changes and vasospastic responses to autacoids in our swine model in vivo.

Mechanisms of coronary hyperconstriction in response to serotonin induced by X-irradiation in miniature pigs: increased constrictive response of medial smooth muscle

Experimental and clinical studies suggest that X-irradiation to the coronary artery may enhance vasoconstrictive response. This study aimed to clarify the effect of X-irradiation on the vasomotor response of porcine coronary artery. X-ray (15 Gy) was selectively irradiated to the left anterior descending coronary artery (LAD) in 14 Göttingen miniature pigs. The coronary vasomotor responses to serotonin at the irradiated site (LAD) and the control site (the left circumflex artery; LCX) were assessed by quantitative arteriography before and 1 h and 1, 2, and 4 weeks after X-irradiation. At 2 weeks, endothelium-dependent vasodilation in response to substance P was also evaluated arteriographically in vivo. At 2 weeks, isometric tension studies were performed to evaluate the constrictive responses of medial muscle strips and endothelium-dependent relaxation. Coronary vasoconstriction in response to serotonin was enhanced 1 week after, and further augmentation was noted 2 and 4 weeks after X-irradiation. Endothelium-dependent vasodilation in response to substance P in vivo was preserved 2 weeks after X-irradiation. Coronary arteriography showed no organic stenosis at the irradiated site. In vitro studies demonstrated that medial muscle strips of the irradiated site showed hypercontraction in response to serotonin and that endothelium-dependent relaxation in response to serotonin and substance P was preserved at the irradiated site. A histological study revealed no appreciable changes of the endothelial cells or intimal thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

Does prevalence of migraine and Raynaud's phenomenon also increase in Korean patients with proven variant angina?

BACKGROUND

The incidence of coronary artery spasm in oriental patients is higher than that in western patients. Oriental patients with variant angina (VA) frequently show normal or insignificant coronary artery stenosis by angiogram, compared with western patients. The prevalence of migraine and Raynaud's phenomenon in oriental patients with VA has not yet reported.

OBJECTIVE

We did a prospective study on the prevalence of migraine and Raynaud's phenomenon in patients with proven VA compared with those in two control groups using a radioisotope technique following ice water exposure. Simultaneously, we studied lipid profiles of each group.

METHODS AND RESULTS

migraine was diagnosed if the score in part A totalled 7 or more of 26, and Raynaud's phenomenon was diagnosed if the score in part B totalled 4 or more of 11 by Miller et al. Technetium-99m-labeled red blood cells (99mTc-RBC) radionuclide angiography was performed in all patients. Patients were included in a prospective protocol. Patients were grouped as follows: Group I: 20 patients with proven VA; Group II: 30 patients with coronary artery disease; Group III: 31 patients without heart disease. Age and sex of patients were not statistically different among the three groups. Migraine was diagnosed in 8 patients (40.0%) of group I and in 6 patients (20.0%) of group II and in 12 patients (38.7%) of group III. Raynaud's phenomenon was reported in 2 (10.0%) of the patients in group I and in 5 (16.1%) of the patients of group III. The mean index ratio of the digital blood flow of right over left hand on static image was 0.85 +/- 0.07 (mean +/- S.E.M.) of the patients of group I, 0.73 +/- 0.03 of the patients of group II and 0.74 +/- 0.04 of the patients of group III. The mean flow index ratio of right over left hand of the digital blood flow on dynamic study was 0.51 of the patients of group I, 0.43 of the patients of group II and 0.43 of the patients of group III. The score of migraine did not differ significantly among the three groups. The score of Raynaud's phenomenon of patients with variant angina did not differ significantly from that of patients in the non-coronary control group, although it differed significantly from that of patients in the coronary control group. But, the prevalence of migraine and Raynaud's phenomenon (questionnaire and radionuclide angiography) in patients of group I did not differ significantly from that in groups II and III. In the end, more patients with variant angina than coronary or non-coronary control group did not reach the predetermined point level for the diagnosis of migraine and Raynaud's phenomenon. Lipid profiles were not significantly different among three groups.

CONCLUSIONS

This result suggests that variant angina may not be a manifestation of a generalized vasospastic disorder in Korean patients.

Mechanisms of ergonovine-induced hyperconstriction of coronary artery after x-ray irradiation in pigs

Mechanisms of ergonovine-induced coronary hyperconstriction were examined in vivo and in vitro in miniature pigs. To provoke coronary hyperconstriction, the endothelium of a segment of a major branch of the left coronary artery was denuded in 19 Göttingen miniature pigs (4 to 6 months of age). In Group I (n = 12), the denuded site of the coronary artery was selectively irradiated with 15Gy of x-ray twice, 3 and 4 months after endothelial denudation. The remaining 7 pigs were not irradiated (Group II). The vasoconstrictive effect of intracoronary administration of ergonovine (1 to 1000 microgram) was examined angiographically 3 months (just before irradiation in group I) and 5 months after denudation in the two groups. After the angiographical study, the vessels were isolated and isometric tensions were measured in an organ chamber. In the in vivo studies, ergonovine-induced vasoconstriction at the denuded and x-ray irradiated site in Group I was significantly greater than that at the control site or that at the denuded site in Group II. Pretreatments with serotonin receptor blockers (ketanserin or methysergide) significantly attenuated ergonovine-induced hyperconstriction, while an alpha-adrenergic receptor blocker (prazosin) did not (% inhibition; ketanserin 74 +/- 9%, p < 0.01, methysergide 60 +/- 10%, p < 0.01, prazosin 9 +/- 5%, NS). In the in vitro studies, ergonovine produced significantly greater tension at the denuded and x-ray irradiated site (Group I) than at the control site or at the denuded site (Group II). Ergonovine-induced endothelium-dependent relaxation was impaired at the denuded site in both groups to a similar extent. These results suggest that ergonovine-induced hyperconstriction at the denuded and x-ray irradiated coronary artery resulted mainly from the hyperreactivity of medial smooth muscle mediated by serotonin receptors.

Endothelium, coronary vasodilation, and organic nitrates

Recent investigations have suggested that the vascular endothelium is an active participant in the regulation of arterial tone and blood flow. In a state of health, the endothelium contributes to hemodynamic equilibrium; however, it rapidly becomes dysfunctional in hypercholesterolemia and diabetes mellitus or with exposure to the stress of hypertension or long-term smoking. Among the deficits observed during endothelial dysfunction is a reduction in the synthesis and release or an excessive degradation of EDRF. This potent vasorelaxant is derived from the amino acid L-arginine and has been characterized as NO or a closely related substance. EDRF relaxes vascular smooth muscle by activating guanylate cyclase. A deficiency in the activity of EDRF may be the mechanism of diminished coronary vasodilation in patients with ischemic heart disease. Organic nitrates, which are metabolized to NO or S-nitrosothiol at the cellular level, are often used in the management of myocardial ischemia; they also induce vasodilation by activating guanylate cyclase. The similarities between organic nitrates and endogenous EDRF and their interactions are discussed in this review.

Role of protein kinase C-mediated pathway in the pathogenesis of coronary artery spasm in a swine model

BACKGROUND

The intracellular mechanism of coronary artery spasm is still unknown. The pathway mediated by protein kinase C (PKC) is an important intracellular process of various cellular responses, including vascular smooth muscle contraction. Thus, we examined the role of the PKC-mediated pathway in the pathogenesis of coronary artery spasm in our in vivo swine model.

METHODS AND RESULTS

Seven Göttingen miniature pigs underwent coronary balloon injury and x-ray irradiation to induce atherosclerotic lesion. After 6 to 18 months, intracoronary serotonin (3 micrograms/kg) or histamine (3 micrograms/kg) repeatedly induced coronary artery spasm at the atherosclerotic site. At the spastic site, intracoronary administration of phorbol-12,13-dibutyrate (PDBu) (10(-9) mol/kg), a PKC-activating phorbol ester, also induced coronary artery spasm, which was completely blocked by pretreatment with intracoronary staurosporine (10 micrograms/kg), a PKC inhibitor. Intracoronary administration of an inactive phorbol ester, phorbol-12,13-didecanoate (10(-9) mol/kg), did not induce coronary vasoconstriction. Coronary artery spasm induced by the autacoids was significantly augmented by pretreatment with intracoronary PDBu and partially inhibited by staurosporine. Intracoronary administration of Bay K 8644 (10 micrograms/kg), a dihydropyridine-sensitive L-type calcium channel agonist, also induced coronary artery spasm at the spastic site, which was significantly inhibited by pretreatment with intracoronary staurosporine or nifedipine (0.1 mg/kg).

CONCLUSIONS

These results suggest (1) the PKC-mediated pathway is importantly involved in the pathogenesis of coronary artery spasm, (2) activation of the PKC-mediated pathway partially accounts for serotonin- and histamine-induced coronary artery spasm, and (3) at the spastic site, calcium influx through dihydropyridine-sensitive L-type calcium channel and/or calcium sensitivity of the contractile proteins may be augmented by the PKC-mediated pathway.

Vasomotor effects of histamine on bovine and equine basilar arteries in vitro

The vasomotor effects of histamine on isolated bovine and equine basilar arteries were examined. Histamine induced contractions in both these preparations. The maximal response to and pEC50 value for histamine of the equine artery were larger than those of bovine tissue. Similar results were obtained with endothelium-denuded basilar arteries. Diphenhydramine (H1-receptor antagonist) inhibited histamine-induced contractions of the basilar arteries from both species in a concentration-dependent manner and its pA2 values (with 95% confidence limits) were 7.61 (7.39-7.83) and 8.15 (8.01-8.29) for the bovine and equine preparations, respectively. Cimetidine (H2-receptor antagonist) slightly potentiated histamine-induced contractions of bovine, but not equine, basilar arteries. 2-Thiazolylethylamine (H1-receptor agonist) induced contractions in both preparations, whereas impromidine (H2-receptor agonist) induced weak relaxation of the bovine, but not the equine, tissue. These findings indicate that bovine basilar arterial smooth muscle cells possess H1- and H2-receptors. Stimulation of the former results in contraction, whereas stimulation of the latter results in weak relaxation. Equine basilar arterial smooth muscle cells possess H1-receptors, stimulation of which results in contraction.

Intravascular ultrasound detection of atherosclerosis at the site of focal vasospasm in angiographically normal or minimally narrowed coronary segments

OBJECTIVES

The purpose of this study was to use intravascular ultrasound imaging to examine the presence of occult atherosclerosis at the site of focal vasospasm in angiographically normal or minimally narrowed segments, testing the role of atherosclerosis in the development of vasospasm.

BACKGROUND

Previous clinical and experimental studies have suggested that early atherosclerosis is present at the site of focal vasospasm. However, no clinical data exist demonstrating occult disease at the site of vasospasm at angiographically insignificant stenoses.

METHODS

Twenty-two patients with chest pain at rest or during exertion, or both, were studied. Vasospasm was provoked by intracoronary administration of ergonovine maleate (0.01 to 0.04 mg). After relief of vasospasm by nitroglycerin administration, intravascular ultrasound imaging was performed with a 32- or 64-element, 20-MHz, synthetic aperture array ultrasound device.

RESULTS

Focal vasospasm (arterial diameter reduction > or = 90%) with ST-T segment elevation was provoked in 15 patients: in the left anterior descending coronary artery in 8 patients and in the right coronary artery in 7. The remaining seven patients (control group) showed diffuse narrowing, averaging 22 +/- 12% (mean +/- SD) in diameter from the baseline angiograms after ergonovine administration. Atherosclerosis, defined as a significantly thickened intimal leading edge (0.42 +/- 0.07 mm) associated with an increased sonolucent zone (0.57 +/- 0.30 mm), was detected by ultrasound at all 15 sites with focal vasospasm, although these sites were normal or minimally narrowed by angiography. In contrast, seven segments from the control group exhibited a thin intimal leading edge (0.14 +/- 0.04 mm, p < 0.01) and sonolucent zone (0.10 +/- 0.07 mm, p < 0.01), indicating the absence of localized atherosclerotic lesions.

CONCLUSIONS

These results indicate that atherosclerosis is present at the site of focal vasospasm, even in the absence of angiographically significant coronary disease. We suggest that the existence of such atherosclerotic lesions is related to the occurrence of focal vasospasm in the clinical settings.

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)

Statistical analysis of clinical risk factors for coronary artery spasm: identification of the most important determinant

Coronary artery spasm plays an important role in acute ischemic events, and it has a close relationship with coronary atherosclerosis. Thus we attempted to determine the most significant risk factor for coronary artery spasm. Among 3000 consecutive patients who underwent coronary cineangiography with ergonovine maleate testing, 330 with typical angina pectoris (group 1) and 294 with old myocardial infarction (group 2) were studied. We divided each group into three or four subgroups according to the presence of fixed organic stenosis (FOS+) or a positive reaction to ergonovine maleate (coronary artery spasm [CAS]+). We examined the relationship between coronary artery spasm and eight coronary risk factors: age, sex, hypertension, diabetes mellitus, smoking, and serum cholesterol, uric acid, and high-density lipoprotein cholesterol levels. The proportion of smokers in the subgroups with CAS(+) was significantly higher than in the subgroups with CAS(-)(p less than 0.01). There was no correlation between smoking and fixed organic stenosis. According to the results of multiple regression analysis, there was a positive correlation between smoking and CAS(+) and between serum high-density lipoprotein cholesterol levels and CAS(+)(p less than 0.01). Thus we concluded that smoking is the most significant risk factor in discriminating between patients with and without coronary artery spasm.

Long-term study of recurrent vasospastic angina using coronary angiograms during ergonovine provocation tests

Chronologic changes of coronary spasm were examined by repeated ergonovine provocation tests during angiography. A total of 322 patients who had variant angina without severe atherosclerosis demonstrated a positive response to the first test. Ninety of these patients had recurrent variant anginal symptoms after an angina-free period of 38 +/- 12 months (mean +/- SD). Of these 90 patients, 76 (84%) had symptoms or electrocardiographic (ECG) findings similar to those of the first test. The initial 9 of these 76 patients underwent a second provocation test and showed coronary responses analogous to those on the first test. Of the 90 patients, 14 (16%) had different symptoms or ECG findings from those elicited at the first episode. All 14 patients again had a positive response to a second ergonovine test and the following angiographic changes were observed in the three major vessels between the two tests. Of the 21 vessels that had spasm on the first test, eight vessels (19%) did not have spasm on the second test. Of the 21 vessels that did not demonstrate spasm on the first test, 10 (24%) demonstrated spasm on the second test. In the present study it is concluded that the majority of patients with recurrent angina seemed to have consistency in the location of coronary spasm, while in some patients the fluctuation of coronary spasm was confirmed by two ergonovine provocation tests.