Sildenafil Improves Exercise Capacity in Patients with Chronic Heart Failure

SUMMARY Background Phosphodiesterase type 5 inhibitors, as sildenafil, are moderate vasodilators widely used for erectile dysfunction. The evidence currently available establishes that they are potentially useful to treat other conditions like pulmonary hypertension, endothelial dysfunction and chronic heart failure. Objective To evaluate whether sildenafil is useful to improve exercise capacity compared to placebo in patients with chronic heart failure in functional class II-III. Material and Methods A total of 70 patients with chronic heart failure of any etiology, excluding valvular heart disease, were randomly selected. All patients were receiving optimal medical treatment. Patients were included if they had a left ventricular-diastolic diameter of 55 mm, an ejection fraction 90 mm Hg. Patients with anemia, an indication of surgery due to any cause, and those unable to undergo a 6-minute walk test were excluded from the study. After the 6-minute walk test, the patients were randomly assigned to receive 50 mg of sildenafil (sildenafil group) or placebo (placebo group); each group had 35 patients. A second 6-minute walk test was performed 2 hours after the drug was administered. The following variables were evaluated before and after each test: systolic blood pressure, heart rate and the distance walked in meters in each test. Results General characteristic, placebo group versus sildenafil group: men: 74% vs. 88%, ischemic dilated cardiomyopathy: 71% vs. 77%, functional class II: 37% vs. 34%, functional class III: 63% vs. 66%, age: 68±10 vs. 68±12 years, ejection fraction: 26.5%±7.8% vs. 26.5%±6.5%, left ventricular end-diastolic diameter: 65±6 vs. 66±9 mm (all p = ns). Before the first 6-minute walk test, the following variables were measured in the placebo versus the sildenafil group: systolic blood pressure: 115±15 vs. 115±21 mm Hg; diastolic blood pressure: 71±10.5 vs. 68±13 mm Hg (both p = ns); heart rate: 74±13 vs. 64±6 (p <0.001). After the first test and before drug administration: systolic blood pressure: 126±20 vs. 133±26 mm Hg, diastolic blood pressure: 68±11 vs. 72±15 mm Hg; heart rate 84±2 vs. 80±9 (all p = ns). Before the second test and after drug administration, placebo versus sildenafil: systolic blood pressure: 112±14 vs. 95±18 mm Hg; diastolic blood pressure: 69±8 vs. 57±12 mm Hg (both p <0.001); heart rate: 73±11 vs. 75±10 (p = ns). Finally, after the second walk test: systolic blood pressure: 123±17 vs. 115±26 mm Hg (p <0.05), diastolic blood pressure: 65±7 vs. 60±12 mm Hg (p <0.02) and heart rate: 84±13 vs. 86±12 (p = ns). The incidence of headache was 11% (4 patients) in the sildenafil group and 0% in the placebo group. No major events were reported. The sildenafil group walked 222±69 and 313±76 meters before and after drug administration, respectively; the difference was 91±19 meters. The placebo group walked 233±67 and 242±67 meters before and after drug administration, respectively; the difference was 9±5 meters. The difference in the distance walked was greater in the sildenafil group: 91±19 vs. 9±5 (p <0.0001). Conclusions In patients with heart failure in functional class II-III under optimal medical therapy, sildenafil improved exercise capacity compared to placebo.