THE PRE-OPERATIVE RECOGNITION OF THE " MUSCLE-BOUND" RIGHT VENTRICLE IN PULMONARY STENOSIS WITH INTACT VENTRICULAR SEPTUM* BY

In pulmonary stenosis with intact ventricular septum the pre-operative prediction of the severity of the valve stenosis is relatively simple by clinical and hemodynamic criteria (Vogelpoel and Schrire, 1960). However, the assessment of the degree of secondary muscular hypertrophy in the outflow tract is much more difficult and has received little attention. While likely to be pronounced in all moderate and severe cases, the extent of the hypertrophy differs greatly in subjects with valve stenosis of comparable severity and age. The hypertrophy is sometimes massive and, though apparently innocuous and unobtrusive before operation, presents a major problem by causing severe infundibu-lar stenosis following complete relief of the valve stenosis (Kirklin et al., 1953; Brock, 1955, 1957, 1961; Blount et al., 1957; Johnson, 1959). Thus, the pressure in the inflow tract of the right ven-tricle either fails to fall, or drops inadequately. Such a ventricle has been aptly termed "muscle-bound " by Brock (1955). When hypertrophy is modest, the right ventricular pressure falls promptly and whatever secondary infundibular stenosis develops is mild and capable of rapid involution. Hitherto, apart from rapid selective bi-plane angiography or cineangiography (Watson et al., 1960), there have been no reliable signs to enable pre-operative recognition of the degree of sub-valvar muscular hypertrophy in a given subject with pulmonary stenosis. However, it is believe