Early versus late cardiac remodeling during right ventricular pressure load and impact of preventive versus rescue therapy with endothelin-1 receptor blockers.

Pulmonary artery banding (PAB) causes right ventricular (RV) dysfunction, biventricular fibrosis, and apoptosis, which are attenuated by endothelin-1 receptor blockade (ERB). Little is known about the time course of remodeling and whether early versus late ERB confers improved outcome. PAB was performed in five groups of rabbits: Shams, 3-wk PAB (3W), 6-wk PAB (6W), 6-wk PAB + ERB administered from day 1 (6WERB1), and 6-wk PAB + ERB administered from day 21 (6WERB21). Biventricular development of profibrotic molecular signaling, fibrosis, apoptosis, and conductance catheter and echocardiography function were studied. Thirty-three rabbits [ n = 6-7 per group; 3.00 (0.23) kg, mean (SD)] developed half to full systemic RV pressures. Biventricular profibrotic signaling and collagen deposition [RV collagen: Shams 3.8 (0.58) vs. 3W 8.69 (2.52) vs. 6W 8.83 (4.02)%, P < 0.005] and apoptosis [RV: Shams 8.32 (3.2) vs. 3W 55.95 (47.55) vs. 6W 38.85 (17.26) apoptotic cells per microfield, P < 0.0005] increased with PAB. Early and late ERB attenuated fibrosis [RV: 6WERB1 5.55 (1.18), 6WERB21 5.63 (0.72)%] and apoptosis [RV: 6WERB1 11.1 (5.25), 6WERB21 20.24 (7.16) apoptotic cells per microfield, P < 0.0001 vs. 6W]. RV dimensions progressively increased at 3W and 6W and decreased with early ERB [end-diastolic dimensions: Shams 0.4 (0.13) vs. 3W 0.55 (0.78) vs. 6W 0.78 (0.25) vs. 6WERB1 0.71 (0.26) vs. 6WERB21 0.49 (0.23) cm, P < 0.05]. Despite increased RV contractility with PAB [RV end-systolic pressure-volume relationship: Shams 3.76 (1.76) vs. 3W 12.21 (3.44) vs. 6W 19.4 (6.88) mmHg/ml], biventricular function and cardiac output [Shams 196.1 (39.73) vs. 3W 149.9 (34.82) vs. 6W 151 (31.69) ml/min] worsened in PAB groups and improved with early and late ERB [6WERB1 202.8 (26.8), 6WERB21 194.8 (36.93) ml/min, P < 0.05 vs. PAB]. In conclusion, RV pressure overload induces early biventricular fibrosis, apoptosis, remodeling, and dysfunction that worsens with persistent RV hypertension. This remodeling is attenuated by early and late ERB. NEW & NOTEWORTHY Our results in a rabbit model of progressive right ventricular (RV) pressure loading indicate that biventricular fibrosis, apoptosis, and dysfunction are already present when RV hypertension is reached at 3 wk of progressive pulmonary artery banding. These findings worsen with persistent RV hypertension to 6 wk and are attenuated with both early and late endothelin-1 receptor blockade, with some advantages to early therapy. These findings highlight the role of endothelin-1 in driving biventricular remodeling secondary to RV hypertension and suggest that early therapy with an endothelin-1 receptor blocker may be beneficial in attenuating biventricular remodeling but that late therapy is also effective.