The mystery of coronary artery spasm

Vasospastic angina: a review on diagnostic approach and management

Vasospastic angina (VSA) refers to chest pain experienced as a consequence of myocardial ischaemia caused by epicardial coronary spasm, a sudden narrowing of the vessels responsible for an inadequate supply of blood and oxygen. Coronary artery spasm is a heterogeneous phenomenon that can occur in patients with non-obstructive coronary arteries and obstructive coronary artery disease, with transient spasm causing chest pain and persistent spasm potentially leading to acute myocardial infarction (MI). VSA was originally described as Prinzmetal angina or variant angina, classically presenting at rest, unlike most cases of angina (though in some patients, vasospasm may be triggered by exertion, emotional, mental or physical stress), and associated with transient electrocardiographic changes (transient ST-segment elevation, depression and/or T-wave changes). Ischaemia with non-obstructive coronary arteries (INOCA) is not a benign condition, as patients are at elevated risk of cardiovascular events including acute coronary syndrome, hospitalization due to heart failure, stroke and repeat cardiovascular procedures. INOCA patients also experience impaired quality of life and associated increased healthcare costs. VSA, an endotype of INOCA, is associated with major adverse events, including sudden cardiac death, acute MI and syncope, necessitating the study of the most effective treatment options currently available. The present literature review aims to summarize current data relating to the diagnosis and management of VSA and provide details on the sequence that treatment should follow.

Pharmacotherapy in patients with vasomotor disorders

Background

Anginal symptoms in patients with non-obstructive coronary artery disease are frequently related to vasomotor disorders of the coronary circulation. Although frequently overlooked, a distinct diagnosis of different vasomotor disorders can be made by intracoronary function testing. Early detection and treatment seems beneficial, but little evidence is available for the medical treatment of these disorders. Nevertheless, there are several pharmacotherapeutic options available to treat these patients and improve quality of life.

Methods & findings

We performed an extensive yet non-systematic literature search to explore available pharmacotherapeutic strategies for addressing vasomotor disorders in individuals experiencing angina and non-obstructive coronary artery disease. This article presents a comprehensive overview of therapeutic possibilities for patients exhibiting abnormal vasoconstriction (such as spasm) and abnormal vasodilation (like coronary microvascular dysfunction).

Conclusion

Treatment of vasomotor disorders can be very challenging, but a general treatment algorithm based on the existing evidence and the best available current practice is feasible.

Impact of Diltiazem Alone versus Diltiazem with Nitrate on Five-Year Clinical Outcomes in Patients with Significant Coronary Artery Spasm

PURPOSE

Calcium channel blockers diltiazem and nitrate have been used as selective coronary vasodilators for patients with significant coronary artery spasm (CAS). However, no study has compared the efficacy of diltiazem alone versus diltiazem with nitrate for long-term clinical outcomes in patients with CAS.

MATERIALS AND METHODS

A total of 2741 consecutive patients without significant coronary artery disease with positive CAS by acetylcholine (Ach) provocation test between November 2004 and May 2014 were enrolled. Significant CAS was defined as a narrowing of >70% by incremental intracoronary injection of 20, 50, and 100 μg of Ach into the left coronary artery. Patients were assigned to either the diltiazem group (n=842) or the dual group (diltiazem with nitrate, n=1899) at physician discretion. To adjust for potential confounders, a propensity score matching (PSM) analysis was performed using the logistic regression model. After PSM analysis, two well-balanced groups (811 pairs, n=1622, C-statistic=0.708) were generated.

RESULTS

At 5 years, there were similar incidences in primary endpoints, including mortality, myocardial infarction, revascularization, and recurrent angina requiring repeat coronary angiography between the two groups. Diltiazem alone was not an independent predictor for major adverse cardiovascular events or recurrent angina requiring repeat coronary angiography.

CONCLUSION

Despite the expected improvement of endothelial function and the relief of CAS, the combination of diltiazem and nitrate treatment was not superior to diltiazem alone in reducing mortality and cardiovascular events up to 5 years in patients with significant CAS.

Pharmacotherapy of Vasospastic Angina

Vasospastic angina is a diagnosis of exclusion that manifests with signs and symptoms, which overlap with obstructive coronary artery disease, most often ST-segment elevation myocardial infarction. The pharmacotherapy that is available to treat vasospastic angina can help ameliorate angina symptoms. However, the etiology of vasospastic angina is ill-defined, making targeted pharmacotherapy difficult. Most patients receive pharmacotherapy that includes calcium channel blockers and/or long-acting nitrates. This article reviews the efficacy and safety of the pharmacotherapy used to treat vasospastic angina. High-dose calcium channel blockers possess the most evidence, with respect to decreasing angina incidence, frequency, and duration. However, not all patients respond to calcium channel blockers. Nitrates and/or alpha1-adrenergic receptor antagonists can be used in patients who respond poorly to calcium channel blockers. Albeit, evidence for use of nitrates and alpha1-adrenergic receptor antagonists in vasospastic angina is not as robust as calcium channel blockers and can exacerbate adverse effects when added to calcium channel blocker therapy. Despite having a clear benefit in patients with obstructive coronary artery disease, the benefit of beta-adrenergic receptor antagonists, statins, and aspirin remains unclear. More data are needed to elucidate whether or not these agents are beneficial or harmful to patients being treated for vasospastic angina. Overall, the use of pharmacotherapy for the treatment of vasospastic angina should be guided by patient-specific factors, such as tolerability, adverse effects, drug–drug, and drug–disease interactions.

cIMP synthesized by sGC as a mediator of hypoxic contraction of coronary arteries

cGMP is considered the only mediator synthesized by soluble guanylyl cyclase (sGC) in response to nitric oxide (NO). However, purified sGC can synthesize several other cyclic nucleotides, including inosine 3',5'-cyclic monophosphate (cIMP). The present study was designed to determine the role of cIMP in hypoxic contractions of isolated porcine coronary arteries. Vascular responses were examined by measuring isometric tension. Cyclic nucleotides were assayed by HPLC tandem mass spectroscopy. Rho kinase (ROCK) activity was determined by measuring the phosphorylation of myosin phosphatase target subunit 1 using Western blot analysis and an ELISA kit. The level of cIMP, but not that of cGMP, was elevated by hypoxia in arteries with, but not in those without, endothelium [except if treated with diethylenetriamine (DETA) NONOate]; the increases in cIMP were inhibited by the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Hypoxia (Po2: 25-30 mmHg) augmented contractions of arteries with and without endothelium if treated with DETA NONOate; these hypoxic contractions were blocked by ODQ. In arteries without endothelium, hypoxic augmentation of contraction was also obtained with exogenous cIMP. In arteries with endothelium, hypoxic augmentation of contraction was further enhanced by inosine 5'-triphosphate, the precursor for cIMP. The augmentation of contraction caused by hypoxia or cIMP was accompanied by increased phosphorylation of myosin phosphatase target subunit 1 at Thr(853), which was prevented by the ROCK inhibitor Y-27632. ROCK activity in the supernatant of isolated arteries was stimulated by cIMP in a concentration-dependent fashion. These results demonstrate that cIMP synthesized by sGC is the likely mediator of hypoxic augmentation of coronary vasoconstriction, in part by activating ROCK.

Attenuation of exercise induced ST elevation in non-obstructive coronary disease--a case for calcium channel blockade?

A male smoker already on atenolol therapy, presented with chest pain and dramatic exercise induced ST segment elevation. Coronary angiography demonstrated non-obstructive disease and treatment with diltiazem abolished ST segment elevation on subsequent exercise testing.

Thrombin induces endothelial arginase through AP-1 activation

Arterial thrombosis is a common disease leading to severe ischemia beyond the obstructing thrombus. Additionally, endothelial dysfunction at the site of thrombosis can be rescued by l-arginine supplementation or arginase blockade in several animal models. Exposure of rat aortic endothelial cells (RAECs) to thrombin upregulates arginase I mRNA and protein levels. In this study, we further investigated the molecular mechanism of thrombin-induced arginase changes in endothelial cells. Thrombin strikingly increased arginase I promoter and enzyme activity in primary cultured RAECs. Using different deletion and point mutations of the promoter, we demonstrated that the activating protein-1 (AP-1) consensus site located at -3,157 bp in the arginase I promoter was a thrombin-responsive element. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay further confirmed that upon thrombin stimulation, c-Jun and activating transcription factor-2 (ATF-2) bound to the AP-1 site, which initiated the transactivation. Moreover, loss-of-function studies using small interfering RNA confirmed that recruitment of these two transcription factors to the AP-1 site was required for thrombin-induced arginase upregulation. In the course of defining the signaling pathway leading to the activation of AP-1 by thrombin, we found thrombin-induced phosphorylation of stress-activated protein kinase/c-Jun-NH(2)-terminal kinase (SAPK/JNK or JNK1/2/3) and p38 mitogen-activated protein kinase, which were followed by the phosphorylation of both c-Jun and ATF-2. These findings reveal the basis for thrombin induction of endothelial arginase I and indicate that arginase inhibition may be an attractive therapeutic alternative in the setting of arterial thrombosis and its associated endothelial dysfunction.

Recurrent ventricular fibrillation due to coronary artery spasm immediately after ascending aorta replacement

Coronary artery spasm (CAS) is a dangerous complication during cardiac surgery, causing arduous weaning of extracorporeal circulation (ECC) and myocardial tissue loss with consequent left and right ventricular dysfunctions. We describe the case of a 67-year-old man with hypertension and smoking habit, with ECG evidence of lateral myocardial ischemia without symptoms. On this basis, he was investigated with scintigraphy, which confirmed an anterior-lateral area of reversible ischemia and, subsequently, with angiography, which revealed just mild lesion (50%) of diagonal ramus associated with ascending aorta aneurysm: no sign of CAS was detected. Left ventricular function was normal, with mild hypokinesia of the apical segments and trivial aortic regurgitation. The patient underwent ascending aorta replacement with arduous ECC weaning due to CAS: exclusively, the use of intravenous administration of diltiazem led to the solution of this complication. Even if medical therapy is generally efficacious for this complication, the diagnosis is very complicated when it appears in the operating room immediately after cardiac surgery because of the lack of any useful device. The difficulty of diagnosis in the operating room might compromise patient outcome. In our opinion, when ECC weaning is complicated by several episodes of malignant tachyarrhythmia and there is the suspicion of underlying ischemic cause without other obvious causes, CAS must be considered and empirical therapy with calcium channel blockers should be used.

Role of the extracellular matrix and its receptors in smooth muscle cell function: implications in vascular development and disease

PURPOSE OF REVIEW

Cardiovascular disease affects millions of people worldwide, while the sarcoglycan deficient cardiomyopathies are rare disorders. One important common feature, however, is the vascular smooth muscle. Here we focus on the roles of extracellular matrix components and their receptors in the functions of vascular smooth muscle cells.

RECENT FINDINGS

Recent observations highlight the importance of integrins and the dystrophin-glycoprotein complex in development and cardiomyopathy. For example, integrin alpha4 and alpha7 subunits are important for distributing vascular smooth muscle cells during blood vessel development. Studies on delta-sarcoglycan deficient animals have revealed abnormal vascular smooth muscle proliferation and apoptosis. Furthermore, data suggest that perlecan, by affecting smooth muscle cell proliferation, participates in the atherosclerotic process. Overexpression of decorin leads to reduced progression of atherosclerosis and thrombospondin-1 has been implicated in regulation of smooth muscle cell contractility via inhibition of nitric oxide. Novel findings on versican suggest that the binding of versican to fibulin is of great importance for regulating smooth muscle cell function.

SUMMARY

By regulating migration, proliferation and apoptosis as well as extracellular matrix synthesis and assembly, proteoglycans, integrins and the dystrophin-glycoprotein complex may be of great importance both during development and in vascular disease.