Mid-ventricular obstruction: a variant of obstructive cardiomyopathy.

In two patients with clinical and catheterization findings of hypertrophic obstructive cardiomyopathy, the level of intraventricular obstruction was found to be in the mid-ventricular area rather than at the junction of the inflow and outflow tracts. One patient died suddenly shortly after unsuccessful outflow tract myectomy. In vivo recognition of this probably rare variant form of obstructive cardiomyopathy rests mainly on the angiograhic appearance of the left ventricle and on the recording of pressures in multiple sites of the left ventricular cavity. Surgical relief of the obstruction in these patients is not likely to be obtained by a transaortic left ventricular outflow myectomy but may require either papillary muscle resection by the transatrial or transventricular approach or mid-ventricular septectomy, or both.