Background: Arterial systemic hypertension (SH) can be associated with a decrease in endothelium-dependent nitric oxide (NO). Sildenafil increases cyclic guanosine monophosphate (cGMP), a mediator of NO. However, little is known about the effects of PDE5 inhibition on 24-hour ambulatory pressure (ABP) and exercise blood pressure, noreprinephrine (Nor), and exercise capacity, especially after orthotopic heart transplantation (OHT).
Methods: We studied 22 OHT patients who on the 1st day underwent a cardiopulmonary (CP) self-controlled treadmill 6' walk test (6') and, then, an ECG monitored CP treadmill maximal exercise test (Ex) within 60 and 90 minutes after oral Sildenafil (Sil; 50 mg) or placebo (Pl) given at random, and ABP. We determined at basal position (b), in the last minute of the 6' and at the peak Ex, the HR (bpm), Systolic blood pressure (SBP), and diastolic blood pressure (DBP), (mm Hg), VO2 (mL/kg/min), Slope VE/VCO2, exercise time (ET, min), distance (D; miles), and Nor (pg/mL). Also, after CP tests, 24-h SBP and DBP, the measurements were repeated on the 2nd day when the cross-over was done.
Results: Sil significantly reduced blood pressure in the basal position and during exercise. It also promoted a significant reduction in SBP and DBP during 24 hours, daytime and nighttime. Sil did not change exercise capacity.
Conclusion: The NO-cGMP pathway seems to play a role in blood pressure control in OHT. In addition to antihypertensive therapy, PDE5 inhibition may have potential beneficial effects on hypertensive OHT.