LEFT VENTRICULAR OUTFLOW OBSTRUCTION CAUSED BY MITRAL RING CALCIFICATION

Kanji Iga M.D., Kenjiro Hori M.D.

The patient is a 77 year-old woman who has been followed up in our outpatient department for past posterior myocardial infarction and Parkinsonism. She has been asymptomatic for the past few years. A grade 3/6 mid-systolic murmur, heard maximally at the 4th left intercostal space, transmitted slightly to the right carotid artery. Electrocardiography showed normal sinus rhythm and tall T waves in leads V1 through V4. An abnormal round calcification, observed in a lateral chest film has become more severe than it has been 5 years previously (Figure 1). Echocardiography showed the aortic and mitral valves to be free of organic change; a dense, thick calcification was seen along the mitral ring which extended to the rim of anterior mitral leaflet and the left ventricular outflow tract (Figure 2-A). There was no systolic anterior motion of the mitral valve (Figure 2-C) ; the left ventricular wall thickness was normal . Two-dimensional Doppler echocardiography revealed a mosaic signal in the left ventricular outflow tract; mild mitral regurgitation was seen. Continuous wave Doppler echocardiography showed that peak velocity of the left ventricular outflow tract to be 3.5m/sec. in late systole (Figure 2-B).

Mitral ring calcification, an aging process frequently seen via routine echocardiography and lateral chest film and sometimes involves considerable cardiovascular disease (1). Labovitz et al. studied 51 patients with mitral ring calcification via Doppler echocardiography; hemodynamically, mitral stenosis was seen in 8 % and mitral regurgitation was seen in 55 % (2). However, there have been no reports of mitral ring calcification causing left ventricular tract obstruction documented via Doppler echocardiography. In the present patient, although the velocity waveform of the left ventricular outflow tract was late-peaking similar to those described in hypertrophic obstructive cardiomyopathy (3), there were neither systolic anterior motion of the mitral valve nor hypertrophy of the left ventricle. We think that the cause of this dynamic obstruction in the left ventricular outflow tract is not due to hypertrohic cardiomyopathy frequently associated by mitral ring calcification (4), but the interventricular septum contracting against extended mitral ring calcification . Cardiac murmur is frequently heard in cases with mitral ring calcification. We feel that left ventricular outflow obstruction caused by mitral ring calcification can be an origin of systolic murmur in patients with mitral ring calcification.