Mitral regurgitation in hypertrophic obstructive cardiomyopathy: Relationship to obstruction and relief with myectomy

OBJECTIVES This study examined: 1) the impact of myectomy on postoperative mitral regurgitation (MR) and 2) the association between the severity of MR and the left ventricular outflow tract (LVOT) gradient. BACKGROUNDS For patients with hypertrophic obstructive cardiomyopathy (HOCM ) and MR, controversy exists as to whether myectomy alone is sufficient in eliminating MR. Furthermore, the relationship between the degree of MR and the LVOT peak gradient has not been well defined. METHODS We performed pre- and postoperative transthoracic as well as intrao perative transesophageal studies in 104 consecutive patients with HOCM unde rgoing septal myectomy. Left ventricular outflow tract gradient and the nat ure of MR were assessed. RESULTS In the 93 patients without independent mitral valve disease, a rela tionship was observed between MR severity and the LVOT gradient. Left ventr icular outflow tract gradient (mean +/- standard deviation) for trivial, mi ld, moderate and severe MR were: 23.2 +/- 19.1, 43.8 +/- 25.4, 70.1 +/- 21. 0 and 104 +/- 21.0 mm Hg (p < 0.001). Early postoperative, MR was absent or trivial in 80%, mild in 19% and moderate in 1%. None of these patients req uired additional mitral valve surgery. For patients with independent mitral valve disease (n = 11), five required mitral valve surgery as well as myec tomy. The remainder had significant reductions in the degree of MR with mye ctomy alone. CONCLUSIONS For patients with HOCM and MR not due to independent mitral val ve disease, myectomy significantly reduced the degree of MR, without requir ement for additional mitral valve surgery. In these patients the severity o f MR was directly related to the magnitude of the LVOT gradient. (C) 2000 b y the American College of Cardiology.