Effects of intermittent pressure loading on the development of ventricular hypertrophy in the cat.

Although the effects of persistent pressure loading on the development of ventricular hypertrophy have been studied extensively, the effects of intermittent pressure loading have not been examined. To study the effects of intermittent pressure loading we subjected the right ventricle of cats to intermittent pulmonary artery constriction over a 2-week period. Two intermittent pressure loading schedules were employed. The first consisted of a right ventricular systolic pressure of 60 mm Hg for 3.5 days and normal right ventricular pressure for 3.5 days; and the second consisted of a right ventricular systolic pressure of 60 mm Hg for 2.3 days and normal right ventricular pressure for 4.7 days. The intermittent pressure-loaded cats were compared with normal unoperated controls, sham-operated controls, and cats with persistent right ventricular pressure load for either 1-week or 1- to 2-month duration. The data indicate that intermittent pressure loading caused significant right ventricular hypertrophy. Since significant residual ventricular hypertrophy was present in both intermittent pressure loading groups, regression of ventricular hypertrophy involves a slower process than the progression of hypertrophy.