Congenital absence of the left circumflex coronary artery in the systolic click syndrome.

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Abstract
The anatomy of the coronary artery circulation was examined by means of selective coronary arteriography in 19 patients, evaluated because of disabling chest pain and ECG abnormalities, with typical clinical findings of the systolic click syndrome (SCS). In 17 (89.5%), the elft circumflex coronary artery (LCCA) was absent; a single marginal branch arose from the left main vessel, but no vessel was present in or near the atrioventricular (A-V) groove. In contrast, the LCCA was identified in 74 of 78 control patients (94.9%) considered to have representative normal distribution of coronary artery branches, All but two patients with SCS exhibited reduced contraction of the segment of left ventricular (LV) myocardium surrounding the mitral valve ring (extent of systolic diameter decrease 1.4 +/- 3.1% vs normal 31.8 +/- 3.4%, P lwss than 0.001), as well as of the LV inflow tract (diameter decreasce 16.2 +/- 2.5% vs normal 38.6 +/- 1.8% P less than 0.001); both of these regions of the left ventricle derive their vascular supply from the LCCA, An identical segmental LV contraction disorder was observed in seven patients with functionally single vessel occlusive coronary artery disease involving the LCCA, An identical finding in this study was a relatively high incidence of absent LCCA (42%) in 19 patients with atypical angina and normal coronary arteriograms. It is concluded that a congenital anomaly of the coronary circulation, with absent LCCA, may be responsible for segmental myocardial dysfunction in some patients with SCS. In turn, this segmental contraction disorder may determine functional abnormality of the mitral valve apparatus.