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

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Abstract
Rabbits (24) were divided into 3 groups. Ten and 8 of these animals were injected with Sephadex G 100 particle suspension [particle size 40-120 .mu.m; 72,000 particles in 0.5 ml phosphate buffered saline (PBS)] and with Sephadex G 50-coarse particle suspension [particle size 150-300 .mu.m; 1800 particles in 0.5 ml PBS] respectively, twice a week i.v.; the others were injected with PBS alone as control in the same way. At 15 or 60 min before sacrifice these animals were treated with injections of 10-20 .mu.Ci of 201T in 0.2 ml 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 4-6 wk 41.4% at 7-9 wk and 33.4% at 10-13 wk. The mean ratio in the total Sephadex G 100 embolic animals was 36.8 .+-. 1.9 (SD) percent which was .apprx. 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 wk and the mean ratio was 35.3% at 7-9 wk and 31.0% at 10-13 wk. In the total Sephadex G 50-coarse embolic animals it was 34.4 .+-. 2.6%, which was significantly different from control value at P < 0.05. Repeated pulmonary embolization evidently can produce right ventricular hypertrophy. In the distribution of 201Tl, 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 4-6 wk, 23.4% at 7-9 wk and 21.1% at 10-13 wk. 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 wk. The mean ratio was 19.4% at 7-9 wk and 12.5% at 10-13 wk. In the total Sephadex G 50 embolic animals it was 21.0 .+-. 5.1%. The RV weight in experimental right ventricular hypertrophy induced by repeated pulmonary embolization apparently was not always proportional to the increased uptake of the tracer in the myocardium.
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