Effects of sildenafil on invasive haemodynamics and exercise capacity in heart failure patients with preserved ejection fraction and pulmonary hypertension: a randomized controlled trial.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF), with associated pulmonary hypertension is an increasingly large medical problem. Phosphodiesterase (PDE)-5 inhibition may be of value in this population, but data are scarce and inconclusive. METHODS AND RESULTS: In this single centre, randomized double-blind, placebo-controlled trial, we included 52 patients with pulmonary hypertension [mean pulmonary artery pressure (PAP) >25 mmHg; pulmonary artery wedge pressure (PAWP) >15 mmHg] due to HFpEF [left ventricular ejection fraction (LVEF) ≥45%]. Patients were randomized to the PDE-5 inhibitor sildenafil, titrated to 60 mg three times a day, or placebo for 12 weeks. The primary endpoint was change in mean PAP after 12 weeks. Secondary endpoints were change in mean PAWP, cardiac output, and peak oxygen consumption (peak VO2). Mean age was 74 ± 10 years, 71% was female, LVEF was 58%, median NT-proBNP level was 1087 (535-1945) ng/L. After 12 weeks, change in mean PAP was -2.4 (95% CI -4.5 to -0.3) mmHg in patients who received sildenafil, vs. -4.7 (95% CI -7.1 to -2.3) mmHg in placebo patients (P = 0.14). Sildenafil did not have a favourable effect on PAWP, cardiac output, and peak VO2. Adverse events were overall comparable between groups. CONCLUSION: Treatment with sildenafil did not reduce pulmonary artery pressures and did not improve other invasive haemodynamic or clinical parameters in our study population, characterized by HFpEF patients with predominantly isolated post-capillary pulmonary hypertension. (ClinicalTrials.gov, number NCT01726049).

Cardiorenal Effects of Long-Term Phosphodiesterase V Inhibition in Pre-Heart Failure.

Background Phosphodiesterase V (PDEV) is upregulated in heart failure, leading to increased degradation of cGMP and impaired natriuresis. PDEV inhibition improves the renal response to B-type natriuretic peptide in animal models. We tested the hypothesis that long-term PDEV inhibition would improve renal function and cardiorenal response after short-term volume load in subjects with pre-heart failure. Methods and Results A total of 20 subjects with pre-heart failure (defined as an ejection fraction ≤45% without previous diagnosis of heart failure) and renal impairment were randomized in a 2:1 manner to tadalafil or placebo. Baseline echocardiography and renal clearance study were performed, followed by a short-term saline load and repeated echocardiography and renal clearance study. Subjects then received either tadalafil at a goal dose of 20 mg daily or placebo, and the study day was repeated after 12 weeks. Long-term tadalafil did not improve glomerular filtration rate (median increase of 2.0 mL/min in the tadalafil group versus 13.5 mL/min in the placebo group; P=0.54). There was no difference in urinary sodium or cGMP excretion with PDEV inhibition following short-term saline loading. Conclusions Glomerular filtration rate and urinary sodium/cGMP excretion were not significantly different after 12 weeks of tadalafil compared with placebo. These results do not support the use of PDEV inhibition to improve renal response in patients with pre-heart failure. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01970176.

Phosphodiesterase type 5 inhibition may reduce diastolic function in women with ischemia but no obstructive coronary artery disease.

BACKGROUND: Ischemia, in the absence of obstructive coronary artery disease, is prevalent in women, and associated with increased risk for major cardiovascular events. Coronary microvascular dysfunction is prevalent in these patients, and associated with impaired diastolic function. Despite our general understanding, however, optimal treatment of this cohort remains elusive. METHODS: To address this knowledge gap, we performed an open-label treatment trial to assess whether phosphodiesterase type 5 inhibition improves coronary microvascular perfusion and diastolic function in women with signs and symptoms of ischemia but no evidence of obstructive coronary artery disease. Left ventricular morphology and function, along with myocardial perfusion reserve index, were assessed by contrast-enhanced cardiac magnetic resonance imaging. RESULTS: A total of five women enrolled of which four completed the trial, while one was withdrawn by the investigators after developing dyspnea 1 week after treatment. Her symptoms resolved after cessation of the study medication. In contrast to our hypothesis, phosphodiesterase type 5 inhibition reduced the rate of circumferential strain in diastole in all four women who completed the trial (that is, diastolic dysfunction). This impairment could not be explained by changes in heart rate, contractility, blood pressure, or preload, and was not associated with a change in myocardial perfusion reserve index. Frequency of angina also tended to increase with treatment, with the greatest increase occurring in the patient with the greatest impairment in diastolic strain. CONCLUSIONS: Taken together, these data question the efficacy of phosphodiesterase type 5 inhibition to treat women with ischemic heart disease, and highlight the need for further investigation.

Tadalafil Treatment Delays the Onset of Cardiomyopathy in Dystrophin-Deficient Hearts.

BACKGROUND: Cardiomyopathy is a leading cause of mortality among Duchenne muscular dystrophy patients and lacks effective therapies. Phosphodiesterase type 5 is implicated in dystrophic pathology, and the phosphodiesterase type 5 inhibitor tadalafil has recently been studied in a clinical trial for Duchenne muscular dystrophy. METHODS AND RESULTS: Tadalafil was evaluated for the prevention of cardiomyopathy in the mdx mouse and golden retriever muscular dystrophy dog models of Duchenne muscular dystrophy. Tadalafil blunted the adrenergic response in mdx hearts during a 30-minute dobutamine challenge, which coincided with cardioprotective signaling, reduced induction of µ-calpain levels, and decreased sarcomeric protein proteolysis. Dogs with golden retriever muscular dystrophy began daily tadalafil treatment prior to detectable cardiomyopathy and demonstrated preserved cardiac function, as assessed by echocardiography and magnetic resonance imaging at ages 18, 21, and 25 months. Tadalafil treatment improved golden retriever muscular dystrophy histopathological features, decreased levels of the cation channel TRPC6, increased total threonine phosphorylation status of TRPC6, decreased m-calpain levels and indicators of calpain target proteolysis, and elevated levels of utrophin. In addition, we showed that Duchenne muscular dystrophy patient myocardium exhibited increased TRPC6, m-calpain, and calpain cleavage products compared with control human myocardium. CONCLUSIONS: Prophylactic use of tadalafil delays the onset of dystrophic cardiomyopathy, which is likely attributed to modulation of TRPC6 levels and permeability and inhibition of protease content and activity. Consequently, phosphodiesterase type 5 inhibition is a candidate therapy for slowing the development of cardiomyopathy in Duchenne muscular dystrophy patients.

Effect of phosphodiesterase inhibition on insulin resistance in obese individuals.

BACKGROUND: Obesity is associated with cardiometabolic disease, including insulin resistance (IR) and diabetes. Cyclic guanosine monophosphate (cGMP) signaling affects energy balance, IR, and glucose metabolism in experimental models. We sought to examine effects of phosphodiesterase-5 inhibition with tadalafil on IR in a pilot study of obese nondiabetic individuals. METHODS AND RESULTS: We conducted a randomized, double-blinded, placebo-controlled trial of adults age 18 to 50 years with obesity and elevated fasting insulin levels (≥10 µU/mL). Participants were randomized to tadalafil 20 mg daily or placebo for 3 months. Oral glucose tolerance tests were performed, and the effect of tadalafil on IR was examined. A total of 53 participants (mean age, 33 years; body mass index [BMI], 38 kg/m(2)) were analyzed, 25 randomized to tadalafil and 28 to placebo. In the overall sample, measures of IR did not differ between tadalafil and placebo groups at 3 months. However, in individuals with severe obesity (BMI ≥36.2 kg/m(2)), tadalafil use was associated with improved IR (homeostatic model assessment for IR), compared to placebo (P=0.02, respectively). Furthermore, one measure of ß-cell compensation for IR (oral disposition index) improved with tadalafil in the overall sample (P=0.009) and in the subgroup with severe obesity (P=0.01). CONCLUSION: Results of this pilot study did not show improvements in IR with tadalafil, compared to placebo. However, tadalafil may have favorable effects on ß-cell compensation, particularly in individuals with severe obesity. Future studies evaluating the potential metabolic benefits of cGMP modulation in obesity are warranted. CLINICAL TRIAL REGISTRATION URL: ClinicalTrials.gov. Unique Identifier: NCT01444651.