Features of atherosclerosis in patients with angina and no obstructive coronary artery disease

Microvascular Resistance Reserve to Assess Microvascular Dysfunction in ANOCA Patients

BACKGROUND

Microvascular resistance reserve (MRR) is a new index to assess coronary microvascular (dys)function, which can be easily measured invasively using continuous thermodilution. In contrast to coronary flow reserve (CFR), MRR is independent of epicardial coronary disease and hemodynamic variations. Its measurement is accurate, reproducible, and operator independent.

OBJECTIVES

The aim of this study was to establish the range of normal values for MRR and to determine an optimal cutoff point.

METHODS

In this exploratory study in 214 patients with angina and no obstructive coronary artery disease, after excluding significant epicardial disease, all physiological parameters, such as fractional flow reserve, index of microvascular resistance, CFR, absolute blood flow, absolute microvascular resistance, and MRR, were measured. On the basis of concordant positive or concordant negative results of index of microvascular resistance and CFR, subgroups of patients were defined with high probability of either normal (n = 122) or abnormal (n = 24) microcirculatory function, and MRR was studied in these groups.

RESULTS

Mean MRR in the "normal" group was 3.4 compared with a mean MRR of 1.9 in the "abnormal" group; these values were significantly different between the groups. MRR >2.7 ruled out coronary microvascular dysfunction (CMD) with a certainty of 96%, whereas MRR <2.1 indicated the presence of CMD with a similar high certainty of 96%.

CONCLUSIONS

MRR is a suitable index to distinguish the presence or absence of CMD in patients with angina and no obstructive coronary artery disease. The present data indicate that an MRR of 2.7 virtually excludes the presence of CMD, while an MRR value <2.1 confirms its presence.

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.

Cellular Mechanisms of Coronary Artery Spasm

Coronary artery spasm (CAS) is a reversible phenomenon caused by spontaneous excessive vascular smooth muscle contractility and vascular wall hypertonicity, which results in partial or complete closure of the lumen of normal or atherosclerotic coronary arteries. The clinical picture of CAS includes chest discomfort which is similar in quality to that of stable effort angina. Mechanisms underlying the development of CAS are still unclear. CAS certainly is a multifactorial disease. In this review, we paid attention to the role of the main pathophysiologic mechanisms in CAS: endothelial dysfunction, chronic inflammation, oxidative stress, smooth muscle hypercontractility, atherosclerosis and thrombosis, and mutations leading to deficient aldehyde dehydrogenase 2 (ALDH2) activity. These findings might shed novel insight on the underlying mechanisms and identify potential diagnostic and therapeutic targets for cardiovascular diseases in the future.