Clinical Use of Phosphodiesterase-5 Inhibitors in Chronic Heart Failure

Current understanding of structural and molecular changes in diabetic cardiomyopathy

Diabetic Mellitus has been characterized as the most prevalent disease throughout the globe associated with the serious morbidity and mortality of vital organs. Cardiomyopathy is the major leading complication of diabetes and within this, myocardial dysfunction or failure is the leading cause of the emergency hospital admission. The review is aimed to comprehend the perspectives associated with diabetes-induced cardiovascular complications. The data was collected from several electronic databases such as Google Scholar, Science Direct, ACS publication, PubMed, Springer, etc. using the keywords such as diabetes and its associated complication, the prevalence of diabetes, the anatomical and physiological mechanism of diabetes-induced cardiomyopathy, the molecular mechanism of diabetes-induced cardiomyopathy, oxidative stress, and inflammatory stress, etc. The collected scientific data was screened by different experts based on the inclusion and exclusion criteria of the study. This review findings revealed that diabetes is associated with inefficient substrate utilization, inability to increase glucose metabolism and advanced glycation end products within the diabetic heart resulting in mitochondrial uncoupling, glucotoxicity, lipotoxicity, and initially subclinical cardiac dysfunction and finally in overt heart failure. Furthermore, several factors such as hypertension, overexpression of renin angiotensin system, hypertrophic obesity, etc. have been seen as majorly associated with cardiomyopathy. The molecular examination showed biochemical disability and generation of the varieties of free radicals and inflammatory cytokines and becomes are the substantial causes of cardiomyopathy. This review provides a better understanding of the involved pathophysiology and offers an open platform for discussing and targeting therapy in alleviating diabetes-induced early heart failure or cardiomyopathy.

Heart Failure with Preserved Ejection Fraction and Pulmonary Hypertension: Focus on Phosphodiesterase Inhibitors

Pulmonary hypertension (PH) is common in patients with heart failure with preserved ejection fraction (HFpEF). A chronic increase in mean left atrial pressure leads to passive remodeling in pulmonary veins and capillaries and modest PH (isolated postcapillary PH, Ipc-PH) and is not associated with significant right ventricular dysfunction. In approximately 20% of patients with HFpEF, "precapillary" alterations of pulmonary vasculature occur with the development of the combined pre- and post-capillary PH (Cpc-PH), pertaining to a poor prognosis. Current data indicate that pulmonary vasculopathy may be at least partially reversible and thus serves as a therapeutic target in HFpEF. Pulmonary vascular targeted therapies, including phosphodiesterase (PDE) inhibitors, may have a valuable role in the management of patients with PH-HFpEF. In studies of Cpc-PH and HFpEF, PDE type 5 inhibitors were effective in long-term follow-up, decreasing pulmonary artery pressure and improving RV contractility, whereas studies of Ipc-PH did not show any benefit. Randomized trials are essential to elucidate the actual value of PDE inhibition in selected patients with PH-HFpEF, especially in those with invasively confirmed Cpc-PH who are most likely to benefit from such treatment.

Effects of furosemide and tadalafil in both conventional and nanoforms against adenine-induced chronic renal failure in rats

BACKGROUND

Chronic renal failure (CRF) is a progressive loss of renal function that lead to reduced sodium filtration and inappropriate suppression of tubular reabsorption that ultimately leads to volume expansion. The aim of this study was to study the efficacy of furosemide and tadalafil nanoforms compared to conventional forms against adenine-induced CRF rat-model.

METHODS

Addition of 0.75% adenine to the diet of rats for 4 weeks gained general acceptance as a model to study kidney damage as this intervention mimicked most of the structural and functional changes seen in human chronic kidney disease Urine analysis, histopathological changes and immunohistochemical expression of caspase-3 and interleukin-1 beta (IL-1β) in renal tissues were performed.

RESULTS

Our results showed that the combination of tadalafil and furosemide using conventional and nanoparticle formulations had better renoprotective effect than individual drugs. This was demonstrated by improvement of urinary, serum and renal tissue markers as indicative of organ damage. This was also reflected on the reduction of tubular expression of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Immunohistochemical studies showed that the deteriorated renal cellular changes indicated by increased expression of caspase-3 and IL-1β were greatly improved by the combined treatment particularly with the nanoforms.

CONCLUSIONS

The nanoforms of both furosemide and tadalafil had greater renopreventive effects compared with conventional forms against adenine-induced CRF in rats.

Nitric oxide — soluble guanylate cyclase — cyclic guanosine monophosphate signaling pathway in the pathogenesis of heart failure and search for novel therapeutic targets

Heart failure is a severe disease with an unfavorable prognosis, which requires intensification of therapy and the search for novel approaches to treatment. In this review, the physiological significance of soluble guanylate cyclase-related signaling pathway, reasons for decrease in its activity in heart failure and possible consequences are discussed. Pharmacological methods of stimulating the production of cyclic guanosine monophosphate using drugs with different mechanisms of action are considered. Data from clinical studies regarding their effectiveness and safety are presented. A promising approach is stimulation of soluble guanylate cyclase, which showed beneficial effects in preclinical studies, as well as in the recently completed phase III VICTORIA study.

Targeting Cyclic Guanosine Monophosphate to Treat Heart Failure: JACC Review Topic of the Week

The significant morbidity and mortality associated with heart failure with reduced ejection fraction (HFrEF) or heart failure with preserved ejection fraction (HFpEF) justify the search for novel therapeutic agents. Reduced cyclic guanosine monophosphate levels contribute to HF progression. Among molecules modulating the nitric oxide (NO)-GMP-phosphodiesterase (PDE) pathway, the evaluation of nitrates, synthetic natriuretic peptides (NP), and NP analogs has yielded mixed results. Conversely, sacubitril/valsartan, combining NP degradation inhibition through neprilysin and angiotensin receptor blockade, has led to groundbreaking findings in HFrEF. Other strategies to increase tissue cyclic guanosine monophosphate have been attempted, such as PDE-3 or PDE-5 inhibition (with negative or neutral results), NO-independent soluble guanylate cyclase (sGC) activation, or enhancement of sGC sensitivity to endogenous NO. Following the positive results of the phase 3 VICTORIA (A Study of Vericiguat in Participants With Heart Failure With Reduced Ejection Fraction) trial on the sGC stimulator vericiguat in HFrEF, the main open questions are the efficacy of the sacubitril/valsartan-vericiguat combination in HFrEF and of vericiguat in HFpEF.

The hypertensive effect of sorafenib is abolished by sildenafil

Background

Contrasting to the well documented tyrosine kinase inhibitor (TKI)-induced hypertension, little is known on their intrinsic vasomotor effects. We investigated the vasomotor effects of sorafenib, a widely used multikinase inhibitor in the treatment of hepatocellular and renal cell carcinoma and tested the hypothesis that sildenafil, a phosphodiesterase-5 (PDE-5) inhibitor, could represent a pharmacological strategy for the treatment of TKI-induced hypertension.

Methods

Concentration-response curves of sorafenib were constructed in endothelium-intact or denuded precontracted rat aorta, in the presence or absence of several inhibitors. Acute intravenous effects of sorafenib on arterial blood pressure were also investigated in anaesthetized rats. Finally, rats were chronically treated with sorafenib during 4 weeks in the presence and absence of sildenafil.

Results

In endothelium intact aortic ring, sorafenib induced a potent concentration-dependent relaxation of precontracted rat aorta. Removal of the endothelium shifted the concentration-response curve of sorafenib to the right and significantly reduced its maximal effects, demonstrating that sorafenib-induced vasorelaxation is endothelium-dependent and endothelium-independent. Inhibition of the different pathways implicated in the endothelium-dependent and independent vasorelaxation revealed that the endothelium-dependent effects of sorafenib result mainly from the activation of prostaglandin and the nitric oxide (NO) pathways. The endothelium-independent vasodilatory effects of sorafenib may result mainly from the activation of Na/K-ATPase and soluble guanylate cyclase. These vasodilatory effects observed in vitro were confirmed by the decrease in arterial blood pressure observed during acute administrations of sorafenib in anesthetized rats. Finally, and most importantly, we report here for the first time that chronic administration of sorafenib in rats induced an increase in SBP that was abolished by sildenafil.

Conclusion

The multikinase inhibitor sorafenib induced in vitro vasorelaxation of large conductance artery, primary by activating soluble guanylate cyclase. Its chronic administration led to arterial blood hypertension that was counteracted by a PDE-5 inhibitor, sildenafil. Our results suggest that targeting the cGMP pathway including NO signalling might be an interesting pharmacological strategy for the treatment of TKI-induced hypertension.

Pulmonary Hypertension and Heart Failure: A Dangerous Liaison

Pulmonary hypertension (PH) is a common hemodynamic evolution of heart failure (HF) with preserved or reduced ejection fraction, responsible for congestion, symptoms worsening, exercise limitation, and negative outcome. In HF of any origin, PH develops in response to a passive backward pressure transmission as result of increased left atrial pressure. Sustained pressure injury and chronic venous congestion can trigger pulmonary vasoconstriction and vascular remodeling, leading to irreversible pulmonary vascular disease, right ventricular hypertrophy, and failure. In this article, the key determinants of this "dangerous liaison" are analyzed with some digressions on related "leitmotiv" at the horizon.

Mechanisms of the cyclic nucleotide cross-talk signaling network in cardiac L-type calcium channel regulation

Regulation of L-type Calcium (Ca2+) Channel (LCC) gating is critical to shaping the cardiac action potential (AP) and triggering the initiation of excitation-contraction (EC) coupling in cardiac myocytes. The cyclic nucleotide (cN) cross-talk signaling network, which encompasses the β-adrenergic and the Nitric Oxide (NO)/cGMP/Protein Kinase G (PKG) pathways and their interaction (cross-talk) through distinctively-regulated phosphodiesterase isoenzymes (PDEs), regulates LCC current via Protein Kinase A- (PKA) and PKG-mediated phosphorylation. Due to the tightly-coupled and intertwined biochemical reactions involved, it remains to be clarified how LCC gating is regulated by the signaling network from receptor to end target. In addition, the large number of EC coupling-related phosphorylation targets of PKA and PKG makes it difficult to quantify and isolate changes in L-type Ca2+ current (ICaL) responses regulated by the signaling network. We have developed a multi-scale, biophysically-detailed computational model of LCC regulation by the cN signaling network that is supported by experimental data. LCCs are modeled with functionally distinct PKA- and PKG-phosphorylation dependent gating modes. The model exhibits experimentally observed single channel characteristics, as well as whole-cell LCC currents upon activation of the cross-talk signaling network. Simulations show 1) redistribution of LCC gating modes explains changes in whole-cell current under various stimulation scenarios of the cN cross-talk network; 2) NO regulation occurs via potentiation of a gating mode characterized by prolonged closed times; and 3) due to compensatory actions of cross-talk and antagonizing functions of PKA- and PKG-mediated phosphorylation of LCCs, the effects of individual inhibitions of PDEs 2, 3, and 4 on ICaL are most pronounced at low levels of β-adrenergic stimulation. Simulations also delineate the contribution of the following two mechanisms to overall LCC regulation, which have otherwise been challenging to distinguish: 1) regulation of PKA and PKG activation via cN cross-talk (Mechanism 1); and 2) LCC interaction with activated PKA and PKG (Mechanism 2). These results provide insights into how cN signals transduced via the cN cross-talk signaling network are integrated via LCC regulation in the heart.

A Case of Anagrelide-Induced Nonischemic Cardiomyopathy in a Patient With Essential Thrombocythemia

BACKGROUND

Anagrelide is an established treatment option for essential thrombocythemia (ET). Cardiovascular adverse events can occur with its use including heart failure and cardiomyopathy.

CASE REPORT

A 52-year-old African American male with ET presented with chest pain, shortness of breath, and dyspnea on exertion. His ET was managed with hydroxyurea 1500 mg by mouth twice a day and anagrelide 1 mg by mouth 3 times a day. The patient was receiving anagrelide for approximately 2 years prior to presentation. The patient's platelet count was 2.07 × 10⁵ cells/mm³. Transthoracic echocardiography revealed decreased left systolic dysfunction. Also, cardiac magnetic resonance imaging showed an increased left ventricle cavity size with severely depressed systolic dysfunction and an ejection fraction (EF) of 18%. Anagrelide therapy was discontinued and the patient was maintained on hydroxyurea for ET. Three months later, following treatment by a heart failure clinic, the patient's EF was 55%. Five months after discontinuation, the patient improved from New York Heart Association (NYHA) class II to NYHA class I.

CONCLUSION

A 52-year-old man with ET presented with an EF of 18% after 2 years of anagrelide therapy. His EF increased from 18% to 55% 3 months after discontinuation of anagrelide.

Present and future pharmacotherapeutic agents in heart failure: an evolving paradigm

Many conditions culminate in heart failure (HF), a multi‐organ systemic syndrome with an intrinsically poor prognosis. Pharmacotherapeutic agents that correct neurohormonal dysregulation and haemodynamic instability have occupied the forefront of developments within the treatment of HF in the past. Indeed, multiple trials aimed to validate these agents in the 1980s and early 1990s, resulting in a large and robust evidence‐base supporting their use clinically. An established treatment paradigm now exists for the treatment of HF with reduced ejection fraction (HFrEF), but there have been very few notable developments in recent years. HF remains a significant health concern with an increasing incidence as the population ages. We may indeed be entering the surgical era for HF treatment, but these therapies remain expensive and inaccessible to many. Newer pharmacotherapeutic agents are slowly emerging, many targeting alternative therapeutic pathways, but with mixed results. Metabolic modulation and manipulation of the nitrate/nitrite/nitric oxide pathway have shown promise and could provide the answers to fill the therapeutic gap between medical interventions and surgery, but further definitive trials are warranted. We review the significant evidence base behind the current medical treatments for HFrEF, the physiology of metabolic impairment in HF, and discuss two promising novel agents, perhexiline and nitrite.

Roles of phosphodiesterases in the regulation of the cardiac cyclic nucleotide cross-talk signaling network

The balanced signaling between the two cyclic nucleotides (cNs) cAMP and cGMP plays a critical role in regulating cardiac contractility. Their degradation is controlled by distinctly regulated phosphodiesterase isoenzymes (PDEs), which in turn are also regulated by these cNs. As a result, PDEs facilitate communication between the β-adrenergic and Nitric Oxide (NO)/cGMP/Protein Kinase G (PKG) signaling pathways, which regulate the synthesis of cAMP and cGMP respectively. The phenomena in which the cAMP and cGMP pathways influence the dynamics of each other are collectively referred to as cN cross-talk. However, the cross-talk response and the individual roles of each PDE isoenzyme in shaping this response remain to be fully characterized. We have developed a computational model of the cN cross-talk network that mechanistically integrates the β-adrenergic and NO/cGMP/PKG pathways via regulation of PDEs by both cNs. The individual model components and the integrated network model replicate experimentally observed activation-response relationships and temporal dynamics. The model predicts that, due to compensatory interactions between PDEs, NO stimulation in the presence of sub-maximal β-adrenergic stimulation results in an increase in cytosolic cAMP accumulation and corresponding increases in PKA-I and PKA-II activation; however, the potentiation is small in magnitude compared to that of NO activation of the NO/cGMP/PKG pathway. In a reciprocal manner, β-adrenergic stimulation in the presence of sub-maximal NO stimulation results in modest cGMP elevation and corresponding increase in PKG activation. In addition, we demonstrate that PDE2 hydrolyzes increasing amounts of cAMP with increasing levels of β-adrenergic stimulation, and hydrolyzes increasing amounts of cGMP with decreasing levels of NO stimulation. Finally, we show that PDE2 compensates for inhibition of PDE5 both in terms of cGMP and cAMP dynamics, leading to cGMP elevation and increased PKG activation, while maintaining whole-cell β-adrenergic responses similar to that prior to PDE5 inhibition. By defining and quantifying reactions comprising cN cross-talk, the model characterizes the cross-talk response and reveals the underlying mechanisms of PDEs in this non-linear, tightly-coupled reaction system.

PDE 5 inhibition with udenafil improves left ventricular systolic/diastolic functions and exercise capacity in patients with chronic heart failure with reduced ejection fraction; A 12-week, randomized, double-blind, placebo-controlled trial

BACKGROUND

Impaired nitric oxide-mediated pulmonary vascular tone is commonly found in heart failure with reduced ejection fraction (HFrEF), and is associated with derangement of left ventricular (LV) hemodynamics and decreased exercise capacity, which may be reversed by PDE5 inhibitor. This study investigated the effects of a new, long-acting PDE5 inhibitor on LV hemodynamics and exercise capacity in HFrEF.

METHODS

Patients with chronic HFrEF on optimal medical therapy for >30 days before enrollment were randomly assigned to placebo or udenafil at a dose of 50mg 2x/day for the first 4 weeks followed by 100mg 2x/day for the next 8 weeks. All patients underwent cardiopulmonary exercise echocardiography before and after the 12-week treatment.

RESULTS

Improvement of subjective functional capacity was more frequently reported in the udenafil group (P = 0.002). Also, a higher increase in peak VO2 (Δpeak VO2, 21.6% (6.9 ~ 106.4%) vs 1.9% (-15.7 ~ 21.0%) in the placebo group, P = 0.04) and a larger decrease in ventilatory efficiency were observed in the udenafil group (Δ-6.4 ± 9.7 vs Δ1.9 ± 12.1 in the placebo group, P = 0.03). Regarding LV systolic function, the extent of increment in LV ejection fraction was significantly greater in the udenafil group (6.6 ± 6.4% vs 2.3 ± 4.8% in the placebo group, P = 0.02). In the udenafil group, an echocardiographic surrogate of LV filling pressure was more prominently decreased (P = 0.006) along with a significant reverse remodeling of left atrial volume index (57 ± 25mL at baseline to 44 ± 23 at 12th week, P = 0.04) and a progressive fall in B-type natriuretic peptide level (589 ± 679pg/mL at baseline to 220 ± 225pg/mL at 12th week, P < 0.001), indicating LV diastolic function improvement. Udenafil was well tolerated without excess of adverse events compared to placebo.

CONCLUSIONS

Udenafil improves LV systolic/diastolic functions and exercise capacity in conjunction with established conventional pharmacotherapy, without significant adverse events in HFrEF.

Pulmonary hypertension in heart failure with preserved ejection fraction

In heart failure with preserved ejection fraction (HFpEF), an entity that remains challenging and difficult to treat, the development of pulmonary hypertension (PH), via an increase in left atrial pressure, is the direct consequence of reduced relaxation and enhanced stiffness of the left ventricle and is now viewed as an important contributor to clinical worsening and increased mortality. PH becomes a relevant clinical phenotype in approximately 50% of patients with HFpEF and represents a true challenge in the clinical follow-up and management of these patients. Along with these epidemiologic insights, there has been increasing recognition of the pathophysiology of PH and its consequences on the right ventricle in patients with HFpEF. Novel and effective therapeutic interventions aimed at preventing and reversing PH are highly relevant in the attempt to modify the poor clinical trajectory and growing health care burden of HFpEF. Many theoretical rationales as well as progressively accumulating evidence support the usefulness of nitric oxide pathway-potentiating compounds in targeting the lung vasculature through phosphodiesterase 5 inhibitors or guanylate cyclase stimulators to produce vasodilation and potentially a biologic effect. These pharmacologic strategies may be clinically effective options for the treatment of PH in patients with HFpEF; however, large controlled trials are necessary to address definitively the safety, tolerability, and potential impact on morbidity and mortality. This review details the pathophysiologic process, prevalence, and consequences of HFpEF-associated PH and discusses current and emerging treatment strategies to prevent or treat this deleterious sequela when present.

Tadalafil enhances the neuroprotective effects of ischemic postconditioning in mice, probably in a nitric oxide associated manner

This study investigates the modulatory effect of tadalafil, a selective phosphodiesterase (PDE-5) inhibitor, on the neuroprotective effects of ischemic postconditioning (iPoCo) in mice. Bilateral carotid artery occlusion (BCAO) for 12 min followed by reperfusion for 24 h was employed to produce ischemia and reperfusion induced cerebral injury. Cerebral infarct size was measured using TTC staining. Memory was assessed using the Morris water maze test. Degree of motor incoordination was evaluated using inclined beam-walking, rota-rod, and lateral push tests. Brain nitrite/nitrate, acetylcholinesterase activity, TBARS, and glutathione levels were also estimated. BCAO followed by reperfusion produced a significant increase in cerebral infarct size, brain nitrite/nitrate and TBARS levels, and acetylcholinesterase activity along with a reduction in glutathione. Marked impairment of memory and motor coordination was also noted. iPoCo consisting of 3 episodes of 10 s carotid artery occlusion and reperfusion instituted immediately after BCAO significantly decreased infarct size, memory impairment, motor incoordination, and altered biochemistry. Pretreatment with tadalafil mimicked the neuroprotective effects of iPoCo. The tadalafil-induced neuroprotective effects were significantly attenuated by l-NAME, a nonselective NOS inhibitor. We concluded that tadalafil mimics the neuroprotective effects of iPoCo, probably through a nitric oxide dependent pathway, and PDE-5 could be a target of interest with respect to the neuroprotective mechanism of iPoCo.

Neuroprotective effect of tadalafil, a PDE-5 inhibitor, and its modulation by L-NAME in mouse model of ischemia-reperfusion injury

BACKGROUND

The present study investigates the neuroprotective effect of tadalafil, a selective phosphodiesterase-5 inhibitor, in a mouse model of ischemia-reperfusion injury.

MATERIALS AND METHODS

Bilateral carotid artery occlusion for 12 min followed by reperfusion for 24 h was employed to produce ischemia-reperfusion-induced cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test. Degree of motor incoordination was evaluated using inclined beam walk test, rota-rod test, and lateral push test. Brain nitrite/nitrate, brain acetylcholinesterase activity, brain thiobarbituric acid reactive species, and glutathione levels were also estimated.

RESULTS

Bilateral carotid artery occlusion, followed by reperfusion, produced a significant rise in cerebral infarct size, brain nitrite/nitrate levels, acetylcholinesterase activity, and thiobarbituric acid reactive species level along with a fall in glutathione. A significant impairment of memory and motor coordination was also noted. Pretreatment of tadalafil significantly attenuated the above effects of ischemia-reperfusion injury. Tadalafil-induced neuroprotective effects were significantly attenuated by administration of L-NAME, a nonselective nitric oxide synthase inhibitor.

CONCLUSIONS

Results indicate that tadalafil exerts neuroprotective effects, probably through nitric oxide-dependent pathways. Therefore, phosphodiesterase-5 can be explored as an important target to contain ischemia-reperfusion injury.

Right ventricular pulmonary hypertension

In heart failure (HF) syndrome, the development of pulmonary hypertension (PH), right ventricular (RV) dysfunction and failure are ominous prognostic signs. Pathophysiology, clinical interest and targeted therapeutic approaches for left-sided PH and its consequences on RV function have been traditionally confined to advanced HF stages. Community- and population-based studies have clearly indicated that PH is frequent even in HF patients with preserved ejection fraction, and may carry important prognostic implications in normal ageing as well. HF guidelines are inconclusive on both preventive and curative strategies for left-sided PH and its consequences on RV function. The search for new therapeutic opportunities targeted on pulmonary vascular and right heart remodeling are an important challenge for the future.

Treatment for pulmonary hypertension of left heart disease

OPINION STATEMENT

Pulmonary hypertension (PH) secondary to left heart disease is a largely underestimated target of therapy. Except for a specific focus on PH consequences in patients with advanced heart failure (HF) receiving a left ventricular mechanical assist device or candidates for transplantation, prevention and treatment of initial subclinical forms of PH are not considered a priority in the management of this chronic disease population. Nonetheless, there is recent growing evidence supporting a clinical and prognostic role of PH in the elderly and in HF with preserved ejection fraction (pEF). Studies have defined PH-HFpEF as a new entity typically defining the evolving nature of disease. Although the prevalence of PH in these populations is not well-defined, the potential for effective pharmacological approaches that might impact the natural history of the disease starting from earlier stages is promising. However, it should be recognized that pharmacological studies performed to date with traditional pulmonary vasodilators in cohorts with HF and left-sided PH have not been positive, primarily because of concomitant systemic hypotension and hepatic side effects. This evidence along with the lack of studies specifically performed in the elderly and HFpEF often lead Guidelines to give neutral recommendations or even arbitrary assumptions. Recent availability of selective well-tolerated pulmonary vasodilators, such as phosphodiesterase type 5 (PDE5) inhibitors, however, seem to offer a solid background for treating left-sided PH at both early and later stages of the disease process.

Sildenafil improves microvascular O2 delivery-to-utilization matching and accelerates exercise O2 uptake kinetics in chronic heart failure

Nitric oxide (NO) can temporally and spatially match microvascular oxygen (O(2)) delivery (Qo(2mv)) to O(2) uptake (Vo(2)) in the skeletal muscle, a crucial adjustment-to-exercise tolerance that is impaired in chronic heart failure (CHF). To investigate the effects of NO bioavailability induced by sildenafil intake on muscle Qo(2mv)-to-O(2) utilization matching and Vo(2) kinetics, 10 males with CHF (ejection fraction = 27 ± 6%) undertook constant work-rate exercise (70-80% peak). Breath-by-breath Vo(2), fractional O(2)extraction in the vastus lateralis {∼deoxygenated hemoglobin + myoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy}, and cardiac output (CO) were evaluated after sildenafil (50 mg) or placebo. Sildenafil increased exercise tolerance compared with placebo by ∼20%, an effect that was related to faster on- and off-exercise Vo(2) kinetics (P < 0.05). Active treatment, however, failed to accelerate CO dynamics (P > 0.05). On-exercise [deoxy-Hb + Mb] kinetics were slowed by sildenafil (∼25%), and a subsequent response "overshoot" (n = 8) was significantly lessened or even abolished. In contrast, [deoxy-Hb + Mb] recovery was faster with sildenafil (∼15%). Improvements in muscle oxygenation with sildenafil were related to faster on-exercise Vo(2) kinetics, blunted oscillations in ventilation (n = 9), and greater exercise capacity (P < 0.05). Sildenafil intake enhanced intramuscular Qo(2mv)-to-Vo(2) matching with beneficial effects on Vo(2) kinetics and exercise tolerance in CHF. The lack of effect on CO suggests that improvement in blood flow to and within skeletal muscles underlies these effects.

Pulmonary hypertension and right ventricular failure in left ventricular systolic dysfunction

PURPOSE OF REVIEW

Pulmonary hypertension and right ventricular failure (RVF) in left ventricular systolic dysfunction (LVSD) is associated with high morbidity and mortality. This review presents an overview of the classification, pathophysiology, natural history, clinical features, prevention and treatment of this common clinical problem with a focus on the most recent studies. Many of the current evidence-based therapeutic agents for pulmonary hypertension in the absence of systolic or diastolic heart failure (e.g. prostaglandins, endothelin antagonists) are not efficacious in pulmonary hypertension with LVSD.

RECENT FINDINGS

Recent clinical evidence strongly supports an evolving role for phosphodiesterase type 5 (PDE5) inhibition in patients with pulmonary hypertension and LVSD. Chronic PDE5 inhibition in the short-to-intermediate duration studies to date significantly reduces pulmonary pressures and pulmonary vascular resistance (PVR), effects reverse right ventricle and left ventricle remodeling, improves ventilator efficiency, improves peak exercise capacity and improves quality of life in selected patients with stable, moderately symptomatic LVSD and pulmonary hypertension.

SUMMARY

Although long-term outcome studies are currently lacking, chronic PDE5 inhibition should be considered in carefully selected LVSD patients who manifest persistent significant elevation of pulmonary hypertension or PVR or uncontrolled RVF after aggressive management with all standard current evidence-based LVSD therapies (neurohormonal antagonists, diuretics and cardiac resynchronization in appropriate candidates).

Endothelial dysfunction enhances the pulmonary and systemic vasodilator effects of phosphodiesterase-5 inhibition in awake swine at rest and during treadmill exercise

Cardiovascular disease is characterized by impaired exercise capacity and endothelial dysfunction, i.e. reduced bioavailability of nitric oxide (NO). Phosphodiesterase-5 (PDE5) inhibition is a promising vasodilator therapy, but its effects on pulmonary and systemic hemodynamic responses to exercise in the absence, and particularly in the presence, of endothelial dysfunction have not been studied. We investigated the effects of PDE5 inhibitor EMD360527 in chronically instrumented swine at rest and during exercise with and without NO synthase inhibition (N(ω)-nitro-l-arginine; NLA). PDE5 inhibition caused a 19 ± 3% decrease in systemic vascular resistance (SVR) and a 24 ± 4% decrease in pulmonary vascular resistance (PVR) at rest. At maximal exercise, PDE5 inhibition caused a 13 ± 1% decrease in SVR and a 29 ± 3% decrease in PVR. NLA enhanced PDE5-inhibition-induced pulmonary (decrease in PVR 32 ± 12% at rest and 41 ± 3% during exercise) and systemic (decrease in SVR 24 ± 5% at rest and 18 ± 3% during exercise) vasodilation. Similarly, NLA increased the pulmonary and systemic vasodilation to nitroprusside and 8-bromo-cyclic guanosine monophosphate (cGMP), indicating that inhibition of NO synthase increases responsiveness to stimulation of the NO/cGMP pathway. Thus, PDE5 inhibition causes pulmonary and systemic vasodilation that is, respectively, maintained and slightly blunted during exercise. The degree of dilation in both the pulmonary and systemic beds were paradoxically enhanced in the presence of reduced bioavailability of NO, suggesting that this vasodilator therapy is most effective in patients with cardiovascular disease.

Phosphodiesterase type 5 inhibitors as adjunctive therapy in the management of systolic heart failure

OBJECTIVE

To review the efficacy and safety of phosphodiesterase-5 (PDE5) inhibitors in the treatment of patients with chronic systolic heart failure (HF).

DATA SOURCES

Literature was retrieved through MEDLINE (1966-September 2011) and EMBASE (1980-September 2011), using the medical subject heading terms heart failure and phosphodiesterase-5 inhibitors, sildenafil, tadalafil, and vardenafil. Focus was placed on multidose trials of patients with systolic HF, because of these trials' greater strength of clinical evidence.

STUDY SELECTION AND DATA EXTRACTION

All English-language, peer-reviewed publications were analyzed for relevance. Studies appropriate to the objective were evaluated, including 4 multidose trials investigating the effect of sildenafil on cardiovascular function.

DATA SYNTHESIS

In patients with New York Heart Association class II or III HF, treatment with sildenafil was associated with improvements in cardiac index, right ventricular ejection fraction, and other markers of cardiovascular function, as well as reduced pulmonary arterial pressure. Study durations ranged from 4 weeks to 1 year, and the studies used varying doses of sildenafil, ranging from 75 to 225 mg/day, in divided doses. The most common adverse effects associated with sildenafil therapy were headache and flushing.

CONCLUSIONS

Based on current studies, sildenafil appears to be well tolerated and can improve markers of cardiovascular and pulmonary function in patients with HF. PDE5 inhibitors may be a therapeutic option for patients who cannot tolerate standard therapy for HF or who remain symptomatic with standard therapy. Larger long-term trials are necessary to better understand the role of PDE5 inhibitors in HF.

Phosphodiesterase type 5 (PDE5) in the adipocyte: a novel player in fat metabolism?

Phosphodiesterase type 5 (PDE5) is expressed in many tissues (e.g. heart, lung, pancreas, penis) and plays a specific role in hydrolyzing cyclic guanosine monophosphate (cGMP). In adipocytes, cGMP regulates crucial functions by activating cGMP-dependent protein kinase (PKG). Interestingly, PDE5 was recently identified in adipose tissue, although its role remains unclear. Its inhibition, however, was recently shown to affect adipose differentiation and aromatase function. This review summarizes evidence supporting a role for the PDE5-regulated cGMP/PKG system in adipose tissue and its effects on adipocyte function. A better elucidation of the role of PDE5 in the adipocyte could reveal new therapeutic strategies for fighting obesity and metabolic syndrome.

Pulmonary hypertension in heart failure with preserved ejection fraction: a target of phosphodiesterase-5 inhibition in a 1-year study

BACKGROUND

The prevalence of heart failure with preserved ejection fraction is increasing. The prognosis worsens with pulmonary hypertension and right ventricular (RV) failure development. We targeted pulmonary hypertension and RV burden with the phosphodiesterase-5 inhibitor sildenafil.

METHODS AND RESULTS

Forty-four patients with heart failure with preserved ejection fraction (heart failure signs and symptoms, diastolic dysfunction, ejection fraction ≥50%, and pulmonary artery systolic pressure >40 mm Hg) were randomly assigned to placebo or sildenafil (50 mg thrice per day). At 6 months, there was no improvement with placebo, but sildenafil mediated significant improvements in mean pulmonary artery pressure (-42.0±13.0%) and RV function, as suggested by leftward shift of the RV Frank-Starling relationship, increased tricuspid annular systolic excursion (+69.0±19.0%) and ejection rate (+17.0±8.3%), and reduced right atrial pressure (-54.0±7.2%). These effects may have resulted from changes within the lung (reduced lung water content and improved alveolar-capillary gas conductance, +15.8±4.5%), the pulmonary vasculature (arteriolar resistance, -71.0±8.2%), and left-sided cardiac function (wedge pulmonary pressure, -15.7±3.1%; cardiac index, +6.0±0.9%; deceleration time, -13.0±1.9%; isovolumic relaxation time, -14.0±1.7%; septal mitral annulus velocity, -76.4±9.2%). Results were similar at 12 months.

CONCLUSIONS

The multifaceted response to phosphodiesterase-5 inhibition in heart failure with preserved ejection fraction includes improvement in pulmonary pressure and vasomotility, RV function and dimension, left ventricular relaxation and distensibility (structural changes and/or ventricular interdependence), and lung interstitial water metabolism (wedge pulmonary pressure decrease improving hydrostatic balance and right atrial pressure reduction facilitating lung lymphatic drainage). These results enhance our understanding of heart failure with preserved ejection fraction and offer new directions for therapy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT01156636.

PDE5 inhibition with sildenafil improves left ventricular diastolic function, cardiac geometry, and clinical status in patients with stable systolic heart failure: results of a 1-year, prospective, randomized, placebo-controlled study

BACKGROUND

In heart failure (HF), a defective nitric oxide signaling is involved in left ventricular (LV) diastolic abnormalities and remodeling. PDE5 inhibition, by blocking degradation of nitric oxide second-messenger cyclic guanosine monophosphate, might be beneficial. In a cohort of systolic HF patients, we tested the effects of PDE5 inhibition (sildenafil) on LV ejection fraction, diastolic function, cardiac geometry, and clinical status.

METHODS AND RESULTS

Forty-five HF patients (New York Heart Association class II-III) were randomly assigned to placebo or sildenafil (50 mg three times per day) for 1 year, with assessment (6 months and 1 year) of LV ejection fraction, diastolic function, geometry, cardiopulmonary exercise performance, and quality of life. In the sildenafil group only, at 6 months and 1 year, LV ejection fraction, early diastolic tissue Doppler velocities (E') at the mitral lateral (from 4.62 to 5.20 and 5.19 m/s) and septal (from 4.71 to 5.23 and 5.24 m/s) annuli significantly increased, whereas the ratio of early transmitral (E) to E' lateral decreased (from 13.1 to 9.8 to 9.4) (P<0.01). Changes were accompanied by a reverse remodeling of left atrial volume index (from 32.0 to 29.0 and 29.1 mL/m(2); P<0.01) and LV mass index (from 148.0 to 130.0 and 128.0 g/m(2); P<0.01). Furthermore, sildenafil improved exercise performance (peak Vo(2)), ventilation efficiency (ventilation to CO(2) production slope), and quality of life (P<0.01). Minor adverse effects were noted: flushing in 4 and headache in 2 treated patients.

CONCLUSIONS

Findings confirm that in HF, sildenafil improves functional capacity and clinical status and provide the first human evidence that LV diastolic function and cardiac geometry are additional targets of benefits related to chronic PDE5 inhibition.

Pulmonary hypertension with left-sided heart disease

Pulmonary hypertension (PH) with left-sided heart disease is defined, according to the latest Venice classification, as a Group 2 PH, which includes left-sided ventricular or atrial disease, and left-sided valvular diseases. These conditions are all associated with increased left ventricular filling pressure. Although PH with left-sided heart disease is a common entity, and long-term follow-up trials have provided firm recognition that development of left-sided PH carries a poor outcome, available data on incidence, pathophysiology, and therapy are sparse. Mitral stenosis was reported as the most frequent cause of PH several decades ago, but PH with left-sided heart disease is now usually caused by systemic hypertension and ischemic heart disease. In patients with these conditions, PH develops as a consequence of impaired left ventricular relaxation and distensibility. Chronic sustained elevation of cardiogenic blood pressure in pulmonary capillaries leads to a cascade of untoward retrograde anatomical and functional effects that represent specific targets for therapeutic intervention. The pathophysiological and clinical importance of the hemodynamic consequences of left-sided heart disease, starting with lung capillary injury and leading to right ventricular overload and failure, are discussed in this Review, focusing on PH as an evolving contributor to heart failure that may be amenable to novel interventions.