Diagnosis of coronary microvascular dysfunction - Present status

Abstract

Definite clinical diagnosis of microvascular angina is not possible with the existing knowledge. Resting electrocardiogram may be normal, and exercise electrocardiogram may be unremarkable. Echocardiography usually does not show regional wall motion abnormalities. Transthoracic Doppler echocardiography can satisfactorily evaluate only left anterior descending coronary artery and that too in some patients. Radio-isotope imaging can detect only severe localized disease. Noninvasive diagnosis needs high index of suspicion. At present, definite diagnosis is based on documentation of normal epicardial coronaries, coronary flow reserve less than 2.5 on adenosine induced hyperemia, and absence of spasm of epicardial coronaries on acetylcholine provocation. Invasive evaluation is costly, needs sophisticated equipments and expertise. Therapeutic and prognostic implications of various parameters remains to be evaluated. At present invasive evaluation is recommended only for patients with intractable symptoms with unconfirmed diagnosis, requiring repeated hospitalization and evaluation with failure of empirical therapy.

Keywords: Angina; Coronary microcirculation; Ischemic heart disease.

Fig. 1

Pathophysiology of microvascular angina.

Fig. 2

Diagnostic algorithm. Abbreviations: Ach, acetylcholine; ACS, acute coronary syndrome; CAD, coronary artery disease; CAG, coronary angiography; IMR, index of microcirculatory resistance; FFR, fractional flow reserve; TMT, treadmill stress test.