Tolerance of the hypertrophic heart to ischemia. Studies in compensated and failing dog hearts with pressure overload hypertrophy.

Tolerance of the canine heart to prolonged ischemic arrest was studied in 10 hearts from normal control dogs and 15 hearts from dogs with left ventricular hypertrophy (LVH); experiments were performed 1 year after banding the aorta in 8-week-old puppies. At 1 year, hemodynamic studies revealed decreased left ventricular (LV) fiber shortening and elevated end-diastolic pressure (EDP) in five dogs (group with LVH failure); 10 dogs exhibited normal shortening and normal EDP (group with LVH compensation). The left ventricle-to-body weight ratio (g/kg) was 4.

Stress-shortening relations and myocardial blood flow in compensated and failing canine hearts with pressure-overload hypertrophy.

Serial changes in left ventricular (LV) size and function during the adaptation to chronic pressure overload and the transition to pump failure were studied in 16 conscious dogs (aortic bands placed at 8 weeks of age). Echocardiographic data at baseline and at 3, 6, 9, and 12 months after banding revealed a progressive increase in LV mass in all dogs. In six dogs with LV pump failure, there was a progressive decline in circumferential fiber shortening (29 +/- 4% at 12 months); this was significantly less than that seen in five littermate controls (38 +/- 3%, p less than 0.

Effect of propranolol on the left ventricular response to the Valsalva maneuver in normal subjects.

Ten normal subjects performed the Valsalva maneuver before and after the administration of propranolol (1 mg/kg). Changes in left ventricular (LV) size and function were assessed with noninvasive techniques (echocardiography and sphygmomanometer). Data were obtained at baseline, at 20 seconds of the strain phase (phase II) and 10 seconds after the release of strain (phase IV).

When to intervene in chronic aortic regurgitation.

Symptomatic patients with chronic aortic regurgitation should undergo aortic valve replacement. Asymptomatic patients with normal left ventricular function are not surgical candidates, but aortic valve replacement should be performed in most patients with left ventricular dysfunction, even if symptoms are not yet present. The short-term administration of vasodilators is generally beneficial, but there is only meager evidence that the hemodynamic benefits are maintained; for this reason, the wide application of these agents should be postponed until well-designed clinical trials document a long-term benefit.