Right ventricular hypertrophy following chronic pulmonary embolism induced by repeated administration of Sephadex particles.

Abstract

Twenty-four rabbits were divided into three groups. Ten and eight of these animals were injected with Sephadex G 100 particle suspension [particle size 40 to 120 μm; 72, 000 particles in 0.5ml phosphate buffered saline (PBS)] and with Sephadex G 50-coarse particle suspension [particle size 150 to 300μm; 1, 800 particles in 0.5ml PBS], respectively, twice a week intravenously, and the others were injected with PBS alone as control in the same way. Fifteen or 60min before sacrifice these animals were treated with injections of 10 to 20 μCi of thallium-201 in 0.2ml saline. In the Sephadex G 100 embolic animals, the mean weight ratio of the right ventricular free wall (RV) to the left ventricular free wall (LV) plus septum (S) was 36.7% at 4 to 6 weeks, 41.4% at 7 to 9 weeks and 33.4% at 10 to 13 weeks. The mean ratio in the total Sephadex G 100 embolic animals was 36.8±1.9 (S. D.)%, which was approximately 1.30 times as high as control values (control 27.3± 0.9%, p<0.005). In the Sephadex G 50-coarse embolic animals, the weight ratio was 45.5% at 6 weeks, and the mean ratio was 35.3% at 7 to 9 weeks and 31.0% at 10 to 13 weeks. In the total Sephadex G 50-coarse embolic animals it was 34.4±2.6%, which was also significantly different from control value at p<0.05. These data suggest that repeated pulmonary embolization can produce right ventricular hypertrophy. In the distribution of thallium-201, the mean activity ratio of RV to LV +S was 16.4±3.9% in control animals. In the Sephadex G 100 embolic animals it was 31.4% at 4 to 6 weeks, 23.4% at 7 to 9 weeks and 21.1% at 10 to 13 weeks. The mean activity ratio in the total Sephadex G 100 embolic animals was 24.0±2.7%. In the Sephadex G 50-coarse embolic animals the ratio was 49.0% at 6 weeks. The mean ratio was 19.4% at 7 to 9 weeks, and 12.5% at 10 to 13 weeks. In the total Sephadex G 50 embolic animals it was 21. 0±5.1%. These data suggest that the RV weight in experimental right ventricular hypertrophy induced by repeated pulmonary embolization was not always proportional to the increased uptake of the tracer in the myocardium.