Production of Right Ventricular Hypertrophy With and Without Congestive Heart Failure in the Gat

Abstract

Ventricular hyperthrophy and congestive heart failure have been induced in dogs(l), guinea pigs(2), and rabbits(3) and such experimental models have provided considerable insight into these pathologic states. However, a quantitative description of the contractile state of cardiac muscle isolated from the hypertrophied or failing heart is not available. The cat offers unique advantages for analyzing the contractile state of the myocardium in these conditions because the papillary muscle from the right ventricle is small enough to permit in vitro oxygenation and its fibers are oriented in parallel and thus allow definition of heart muscle function per unit of muscle cross-sectional area and length. Further, the functional characteristics of the cat papillary muscle preparation have been described in detail(4) and are sufficiently uniform to allow meaningful comparison of the myocardial contractile state of one group of cats to that of another group(5). To provide the animal model for such studies, a method for production of right ventricular hypertrophy with and without congestive heart failure in the cat has been developed and is the subject of this report. This was accomplished by imposing a chronic pressure load on the right ventricle by reduction of the lumen of the supravalvular portion of the main pulmonary artery.

Methods. The pulmonary artery of the cats was constricted by a circular clip(6) (Fig. 1) which was applied in the following manner. Animals were anesthetized with intravenous sodium methohexital (15 mg/kg). To permit endotracheal intubation and control of respiration intravenous succinylcholine (1 mg kg) was then given and intermittent positive pressure ventilation was applied by a Harvard respirator∗ using air. Under sterile conditions, the chest was opened through the anterior one-third of that left intercostal space lying 2 cm cephalad from the apical impulse, the pericardium was widely excised, and a 5 mm segment of the main pulmonary artery just distal to the pulmonic valve was dissected free of the ascending aorta.