Long-term use of sildenafil in the therapeutic management of heart failure

Exploring the Multifaceted Potential of Sildenafil in Medicine

Phosphodiesterase type 5 (PDE5) is pivotal in cellular signalling, regulating cyclic guanosine monophosphate (cGMP) levels crucial for smooth muscle relaxation and vasodilation. By targeting cGMP for degradation, PDE5 inhibits sustained vasodilation. PDE5 operates in diverse anatomical regions, with its upregulation linked to various pathologies, including cancer and neurodegenerative diseases. Sildenafil, a selective PDE5 inhibitor, is prescribed for erectile dysfunction and pulmonary arterial hypertension. However, considering the extensive roles of PDE5, sildenafil might be useful in other pathologies. This review aims to comprehensively explore sildenafil's therapeutic potential across medicine, addressing a gap in the current literature. Recognising sildenafil's broader potential may unveil new treatment avenues, optimising existing approaches and broadening its clinical application.

Cardiac Effects of Phosphodiesterase-5 Inhibitors: Efficacy and Safety

The coexistence of cardiovascular disease and erectile dysfunction is widespread, possibly owing to underlying endothelial dysfunction in both diseases. Millions of patients with cardiovascular disease are prescribed phosphodiesterase-5 (PDE5) inhibitors for the management of erectile dysfunction. Although the role of PDE5 inhibitors in erectile dysfunction therapy is well established, their effects on the cardiovascular system are unclear. Preclinical studies investigating the effect of PDE5 inhibitors on ischemia-reperfusion injury, pressure overload-induced hypertrophy, and chemotoxicity suggested a possible clinical role for each of these medications; however, attempts to translate these findings to the bedside have resulted in mixed outcomes. In this review, we explore the biologic preclinical effects of PDE5 inhibitors in mediating cardioprotection. We then examine clinical trials investigating PDE5 inhibition in patients with heart failure, coronary artery disease, and ventricular arrhythmias and discuss why the studies likely have yet to show positive results and efficacy with PDE5 inhibition despite no safety concerns.

Cyclic nucleotide phosphodiesterases as therapeutic targets in cardiac hypertrophy and heart failure

Cyclic nucleotide phosphodiesterases (PDEs) modulate the neurohormonal regulation of cardiac function by degrading cAMP and cGMP. In cardiomyocytes, multiple PDE isozymes with different enzymatic properties and subcellular localization regulate local pools of cyclic nucleotides and specific functions. This organization is heavily perturbed during cardiac hypertrophy and heart failure (HF), which can contribute to disease progression. Clinically, PDE inhibition has been considered a promising approach to compensate for the catecholamine desensitization that accompanies HF. Although PDE3 inhibitors, such as milrinone or enoximone, have been used clinically to improve systolic function and alleviate the symptoms of acute HF, their chronic use has proved to be detrimental. Other PDEs, such as PDE1, PDE2, PDE4, PDE5, PDE9 and PDE10, have emerged as new potential targets to treat HF, each having a unique role in local cyclic nucleotide signalling pathways. In this Review, we describe cAMP and cGMP signalling in cardiomyocytes and present the various PDE families expressed in the heart as well as their modifications in pathological cardiac hypertrophy and HF. We also appraise the evidence from preclinical models as well as clinical data pointing to the use of inhibitors or activators of specific PDEs that could have therapeutic potential in HF.

Combined pre- and post-capillary pulmonary hypertension in left heart disease

Patients with heart failure (HF) often have pulmonary hypertension (PH), which is mainly post-capillary; however, some of them also develop a pre-capillary component. The exact mechanisms leading to combined pre- and post-capillary PH are not yet clear, but the phenomenon seems to start from a passive transmission of increased pressure from the left heart to the lungs, and then continues with the remodeling of both the alveolar and vascular components through different pathways. More importantly, it is not yet clear which patients are predisposed to develop the disease. These patients have some characteristics similar to those with idiopathic pulmonary arterial hypertension (e.g., young age and frequent incidence in female gender), but they share cardiovascular risk factors with patients with HF (e.g., obesity and diabetes), with both reduced and preserved ejection fraction. Thanks to echocardiography parameters and newly introduced scores, more tools are available to distinguish between idiopathic pulmonary arterial hypertension and combined PH and to guide patients' management. It may be hypothesized to treat patients in whom the pre-capillary component is predominant with specific therapies such as those for idiopathic pulmonary arterial hypertension; however, no adequately powered trials of PH-specific treatment are available in combined PH. Early evidence of clinical benefit has been proven in some trials on phosphodiesterase type 5 inhibitors, while data on prostacyclin analogues, endothelin-1 receptor antagonists, and soluble guanylate cyclase stimulators are still controversial.

Investigation of Genes and Proteins Expression Associating Serotonin Signaling Pathway in Lung and Pulmonary Artery Tissues of Dogs with Pulmonary Hypertension Secondary to Degenerative Mitral Valve Disease: The Preliminary Study

Simple Summary

Pulmonary hypertension is an unusual elevation of the blood pressure in pulmonary circulation. In dogs, pulmonary hypertension is commonly occurred as a complication of progressive degenerative mitral valve disease especially in senior small-breed dogs. Previous studies revealed that the serotonin signaling pathway is associated with the pathogenesis of pulmonary hypertension. However, research in dogs was scarce. Therefore, the present study aimed to illustrate the understanding of this point by assessing the expression of the targeted genes and proteins related to the serotonin pathway in lung tissues and pulmonary arteries of dogs. Our results showed that the pattern of gene and protein expression was different in canine lung and pulmonary arteries. The targeted proteins in pulmonary artery tissues of the degenerative mitral valve disease dogs with and without pulmonary hypertension tended to be upregulated. In addition, the expression of these protein was increased in the pneumocytes of the alveolar walls, pulmonary alveolar macrophages, and bronchial epithelial cells. A correlation between the targeted gene and protein expression and the echocardiographic data was also founded. Overall results pointed out that the serotonin pathway in lung and pulmonary artery tissues might have different roles in degenerative mitral disease with and without pulmonary hypertension.

Abstract

Pulmonary hypertension (PH) is defined as an increase in pulmonary vascular pressure. It is one of the most common complications that occur as a result of degenerative mitral valve disease (DMVD) in dogs. Serotonin (5-HT) can trigger the development of PH. Accordingly, this study investigated the changes in the expression of genes and proteins associated with local 5-HT signaling in the lungs and pulmonary arteries (PA) of dogs with PH secondary to DMVD. Lung and PA tissue samples were collected from the cadavers of fourteen small-breed dogs and divided into normal (n = 4), DMVD (n = 5) and DMVD with PH (n = 5) groups. Gene expression (tph1, slc6a4 and htr2a) was analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The expression of proteins (TPH-1, SERT, 5-HTR2A, ERK1/2 and pERK1/2) was examined by Western blot analysis and immunohistochemical staining. The results showed that the expression of genes and proteins evaluated by qRT-PCR and Western blot analysis in lung and PA tissues did not differ among groups. However, the expression of proteins related to 5-HT signaling tended to be upregulated in PA tissues from DMVD dogs with and without PH. Immunohistochemical examination revealed the overexpression of these proteins in the DMVD and DMVD with PH groups in lung tissue. These findings suggest a local effect of 5-HT signaling in DMVD dogs with and without PH.

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.

Sex-specific effects of daily tadalafil on diabetic heart kinetics in RECOGITO, a randomized, double-blind, placebo-controlled trial

Cyclic GMP-phosphodiesterase type 5 (PDE5) inhibition has been shown to counteract maladaptive cardiac changes triggered by diabetes in some but not all studies. We performed a single-center, 20-week, double-blind, randomized, placebo-controlled trial (NCT01803828) to assess sex differences in cardiac remodeling after PDE5 inhibition in patients with diabetic cardiomyopathy. A total of 122 men and women (45 to 80 years) with long-duration (>3 years) and well-controlled type 2 diabetes mellitus (T2DM; HbA1c < 86 mmol/mol) were selected according to echocardiographic signs of cardiac remodeling. Patients were randomly assigned (1:1) to placebo or oral tadalafil (20 mg, once daily). The primary outcome was to evaluate sex differences in cardiac torsion change. Secondary outcomes were changes in cardiovascular, metabolic, immune, and renal function. At 20 weeks, the treatment-by-sex interaction documented an improvement in cardiac torsion (-3.40°, -5.96; -0.84, P = 0.011) and fiber shortening (-1.19%, -2.24; -0.14, P = 0.027) in men but not women. The primary outcome could not be explained by differences in cGMP concentrations or tadalafil pharmacodynamics. In both sexes, tadalafil improved hsa-miR-199-5p expression, biomarkers of cardiovascular remodeling, albuminuria, renal artery resistive index, and circulating Klotho concentrations. Immune cell profiling revealed an improvement in low-grade chronic inflammation: Classic CD14⁺⁺CD16^- monocytes reduced, and Tie2⁺ monocytes increased. Nine patients (14.5%) had minor adverse reactions after tadalafil administration. Continuous PDE5 inhibition could offer a strategy to target cardiorenal complications of T2DM, with sex- and tissue-specific responses. Further studies are needed to confirm Klotho and hsa-miR-199-5p as markers for T2DM complications.

Effects of sildenafil on symptoms and exercise capacity for heart failure with reduced ejection fraction and pulmonary hypertension (The SilHF study): A randomised placebo-controlled multicentre trial

Aims

Pulmonary hypertension (PHT) may complicate heart failure with reduced ejection fraction (HFrEF) and is associated with a substantial symptom burden and poor prognosis. Sildenafil, a phosphodiesterase‐5 (PDE‐5) inhibitor, might have beneficial effects on pulmonary haemodynamics, cardiac function and exercise capacity in HFrEF and PHT. The aim of this study was to determine the safety, tolerability, and efficacy of sildenafil in patients with HFrEF and indirect evidence of PHT.

Methods and results

The Sildenafil in Heart Failure (SilHF) trial was an investigator‐led, randomized, multinational trial in which patients with HFrEF and a pulmonary artery systolic pressure (PASP) ≥40 mmHg by echocardiography were randomly assigned in a 2:1 ratio to receive sildenafil (up to 40 mg three times/day) or placebo. The co‐primary endpoints were improvement in patient global assessment by visual analogue scale and in the 6‐min walk test at 24 weeks. The planned sample size was 210 participants but, due to problems with supplying sildenafil/placebo and recruitment, only 69 patients (11 women, median age 68 (interquartile range [IQR] 62–74) years, median left ventricular ejection fraction 29% (IQR 24–35), median PASP 45 (IQR 42–55) mmHg) were included. Compared to placebo, sildenafil did not improve symptoms, quality of life, PASP or walk test distance. Sildenafil was generally well tolerated, but those assigned to sildenafil had numerically more serious adverse events (33% vs. 21%).

Conclusion

Compared to placebo, sildenafil did not improve symptoms, quality of life or exercise capacity in patients with HFrEF and PHT.

Pulmonary vasodilator use in continuous-flow left ventricular assist device management

Pulmonary hypertension (PH) due to left heart disease is the most common etiology for PH. PH in patients with heart failure with reduced fraction (HFrEF) is associated with reduced functional capacity and increased mortality. PH-HFrEF can be isolated post-capillary or combined pre- and post-capillary PH. Chronic elevation of left-sided filling pressures may lead to reverse remodeling of the pulmonary vasculature with development of precapillary component of PH. Untreated PH in patients with HFrEF results in predominant right heart failure (RHF) with irreversible end-organ dysfunction. Management of PH-HFrEF includes diuretics, vasodilators like angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers or angiotensin-receptor blocker-neprilysin inhibitors, hydralazine and nitrates. There is no role for pulmonary vasodilator use in patients with PH-HFrEF due to increased mortality in clinical trials. In patients with end-stage HFrEF and fixed PH unresponsive to vasodilator challenge, implantation of continuous-flow left ventricular assist device (cfLVAD) results in marked improvement in pulmonary artery pressures within 6 months due to left ventricular (LV) mechanical unloading. The role of pulmonary vasodilators in management of precapillary component of PH after cfLVAD is not well-defined. The purpose of this review is to discuss the pharmacologic management of PH after cfLVAD implantation.

CRD-733, a Novel PDE9 (Phosphodiesterase 9) Inhibitor, Reverses Pressure Overload-Induced Heart Failure

BACKGROUND

Augmentation of NP (natriuretic peptide) receptor and cyclic guanosine monophosphate (cGMP) signaling has emerged as a therapeutic strategy in heart failure (HF). cGMP-specific PDE9 (phosphodiesterase 9) inhibition increases cGMP signaling and attenuates stress-induced hypertrophic heart disease in preclinical studies. A novel cGMP-specific PDE9 inhibitor, CRD-733, is currently being advanced in human clinical studies. Here, we explore the effects of chronic PDE9 inhibition with CRD-733 in the mouse transverse aortic constriction pressure overload HF model.

METHODS

Adult male C57BL/6J mice were subjected to transverse aortic constriction and developed significant left ventricular (LV) hypertrophy after 7 days (P<0.001). Mice then received daily treatment with CRD-733 (600 mg/kg per day; n=10) or vehicle (n=17), alongside sham-operated controls (n=10).

RESULTS

CRD-733 treatment reversed existing LV hypertrophy compared with vehicle (P<0.001), significantly improved LV ejection fraction (P=0.009), and attenuated left atrial dilation (P<0.001), as assessed by serial echocardiography. CRD-733 prevented elevations in LV end diastolic pressures (P=0.037) compared with vehicle, while lung weights, a surrogate for pulmonary edema, were reduced to sham levels. Chronic CRD-733 treatment increased plasma cGMP levels compared with vehicle (P<0.001), alongside increased phosphorylation of Ser²⁷³ of cardiac myosin binding protein-C, a cGMP-dependent protein kinase I phosphorylation site.

CONCLUSIONS

The PDE9 inhibitor, CRD-733, improves key hallmarks of HF including LV hypertrophy, LV dysfunction, left atrial dilation, and pulmonary edema after pressure overload in the mouse transverse aortic constriction HF model. Additionally, elevated plasma cGMP may be used as a biomarker of target engagement. These findings support future investigation into the therapeutic potential of CRD-733 in human HF.

Sacubitril-valsartan improves conduit vessel function and functional capacity and reduces inflammation in heart failure with reduced ejection fraction

The Prospective comparison of ARNI with angiotensin-converting enzyme inhibitor to Determine Impact on Global Mortality and morbidity in Heart Failure trial identified a marked reduction in the risk of death and hospitalization for heart failure in patients with heart failure with reduced ejection fraction (HFrEF) treated with sacubitril-valsartan (trade name Entresto), but the physiological processes underpinning these improvements are unclear. We tested the hypothesis that treatment with sacubitril-valsartan improves peripheral vascular function, functional capacity, and inflammation in patients with HFrEF. We prospectively studied patients with HFrEF (n = 11, 10 M/1 F, left ventricular ejection fraction = 27 ± 8%) on optimal, guideline-directed medical treatment who were subsequently prescribed sacubitril-valsartan (open-label, uncontrolled, and unblinded). Peripheral vascular function [brachial artery flow-mediated dilation (FMD, conduit vessel function) and reactive hyperemia (RH, microvascular function)], functional capacity [six-minute walk test (6MWT) distance], and the proinflammatory biomarkers tumor necrosis factor-α (TNF-α) and interleukin-18 (IL-18) were obtained at baseline and at 1, 2, and 3 mo of treatment. %FMD improved after 1 mo of treatment, and this favorable response persisted for months 2 and 3 (baseline: 3.25 ± 1.75%; 1 mo: 5.23 ± 2.36%; 2 mo: 5.81 ± 1.79%; 3 mo: 6.35 ± 2.77%), whereas RH remained unchanged. 6MWT distance increased at months 2 and 3 (baseline: 420 ± 92 m; 1 mo: 436 ± 98 m; 2 mo: 465 ± 115 m; 3 mo: 460 ± 110 m), and there was a sustained reduction in TNF-α (baseline: 2.38 ± 1.35 pg/mL; 1 mo: 2.06 ± 1.52 pg/mL; 2 mo: 1.95 ± 1.34 pg/mL; 3 mo: 1.92 ± 1.37 pg/mL) and a reduction in IL-18 at month 3 (baseline: 654 ± 150 pg/mL; 1 mo: 595 ± 140 pg/mL; 2 mo: 601 ± 176 pg/mL; 3 mo: 571 ± 127 pg/mL). This study provides new evidence for the potential of this new drug class to improve conduit vessel function, functional capacity, and inflammation in patients with HFrEF.NEW & NOTEWORTHY We observed an approximately twofold improvement in conduit vessel function (brachial artery FMD), increased functional capacity (6MWT distance), and a reduction in inflammation (TNF-α and IL-18) following 3 mo of sacubitril-valsartan therapy. These findings provide important new information concerning the physiological mechanisms by which this new drug class provokes favorable changes in HFrEF pathophysiology.

Sildenafil beyond erectile dysfunction and pulmonary arterial hypertension: Thinking about new indications

Sildenafil, approved two decades ago, is the inhibitor of phosphodiesterase 5 (PDE5). First of all, it was designated for angina pectoris, but soon it showed a wonderful efficacy in erectile dysfunction (ED) and then pulmonary arterial hypertension (PAH). Due to the distribution of phosphodiesterase (PDE) in almost all organs, maybe it effects other diseases. Hence, a great number of investigations began to understand the role of PDEi in different organs. Preliminary research on sildenafil in cell culture and animal models has yielded promising results. Soon, a greater number of animal researches and clinical trials joined them. The results disclosed sildenafil can have beneficial effects in each organ such as heart, liver, kidney, brain, and intestines. Furthermore, it has significantly improved the prognosis of organ ischemia in various animal models. Clinical trials in several diseases, such as recurrent spontaneous miscarriage, fatty liver disease, bronchopulmonary dysplasia (BPD), heart failure, and premature ejaculation (PE) brought promising results. Although some clinical trials are available on the effects of sildenafil on various diseases, further studies on humans are needed to consolidate the ultimate effects of sildenafil. The aim of this review was to describe the effects of sildenafil on each organ and explain its mechanisms of action. Further, other PDE inhibitors such as tadalafil and vardenafil have been briefly discussed in parts of this review.

Factors Associated with Ineffectiveness of Sildenafil Treatment in Patients with End-Stage Heart Failure and Elevated Pulmonary Vascular Resistance

Introduction: Elevated pulmonary vascular resistance (PVR) unresponsive to vasodilator treatment is a marker of heart failure (HF) severity, and an important predictor of poor results of heart transplantation (HT). Objective: We sought to analyze factors associated with ineffectiveness of sildenafil treatment in end-stage HF patients with elevated PVR with particular emphasis placed on tenascin-C (TNC) serum concentrations. Patients and Methods: The study is an analysis of 132 end-stage HF patients referred for HT evaluation in the Cardiology Department between 2015 and 2018. TNC was measured by sandwich enzyme-linked immunosorbent assay (Human TNC, SunRedBio Technology, Shanghai, China). The endpoint was PVR > 3 Wood units after the six-month sildenafil therapy. Results: The median age was 58 years, and 90.2% were men. PVR >3 Wood units after 6 months of sildenafil treatment were found in 36.6% patients. The multivariable logistic regression analysis confirmed that TNC (OR = 1.004 (1.002–1.006), p = 0.0003), fibrinogen (OR= 1.019 (1.005–1.033), p = 0.085), creatinine (OR =1.025 (1.004–1.047), p = 0.0223) and right ventricular end-diastolic dimension (RVEDd) (OR = 1.279 (1.074–1.525), p = 0.0059) were independently associated with resistance to sildenafil treatment. Area under the ROC curves indicated an acceptable power of TNC (0.9680 (0.9444–0.9916)), fibrinogen (0.8187 (0.7456–0.8917)) and RVEDd (0.7577 (0.6723–0.8431)), as well as poor strength of creatinine (0.6025 (0.4981–0.7070)) for ineffectiveness of sildenafil treatment. Conclusions: Higher concentrations of TNC, fibrinogen and creatinine, as well as a larger RVEDd are independently associated with the ineffectiveness of sildenafil treatment. TNC has the strongest predictive power, sensitivity and specificity for evaluation of resistance to sildenafil treatment.

Multiplicity of Nitric Oxide and Natriuretic Peptide Signaling in Heart Failure

Heart failure (HF) is a common consequence of several cardiovascular diseases and is understood as a vicious cycle of cardiac and hemodynamic decline. The current inventory of treatments either alleviates the pathophysiological features (eg, cardiac dysfunction, neurohumoral activation, and ventricular remodeling) and/or targets any underlying pathologies (eg, hypertension and myocardial infarction). Yet, since these do not provide a cure, the morbidity and mortality associated with HF remains high. Therefore, the disease constitutes an unmet medical need, and novel therapies are desperately needed. Cyclic guanosine-3',5'-monophosphate (cGMP), synthesized by nitric oxide (NO)- and natriuretic peptide (NP)-responsive guanylyl cyclase (GC) enzymes, exerts numerous protective effects on cardiac contractility, hypertrophy, fibrosis, and apoptosis. Impaired cGMP signaling, which can occur after GC deactivation and the upregulation of cyclic nucleotide-hydrolyzing phosphodiesterases (PDEs), promotes cardiac dysfunction. In this study, we review the role that NO/cGMP and NP/cGMP signaling plays in HF. After considering disease etiology, the physiological effects of cGMP in the heart are discussed. We then assess the evidence from preclinical models and patients that compromised cGMP signaling contributes to the HF phenotype. Finally, the potential of pharmacologically harnessing cardioprotective cGMP to rectify the present paucity of effective HF treatments is examined.

[Problematic aspects of pulmonary hypertension due to left heart disease: focus on combined postcapillary and precapillary pulmonary hypertension]

Рulmonary hypertension (PH) is a common complication of left heart diseases. In addition to a passive increase of pressure in the venous bed of the pulmonary circulation, leading to an increase of mean pulmonary pressure, signs of precapillary PH could be detected in some patients. Since 2013, a hemodynamic subtype of PH due to left heart diseases combined post/precapillary PH has been identified, with a more unfavorable prognosis and high mortality.

Targeted therapy with phosphodiesterase 5 inhibitors in patients with pulmonary hypertension due to heart failure and elevated pulmonary vascular resistance: a systematic review

Pulmonary Hypertension due to left heart disease is the most common type of Pulmonary Hypertension. Morbidity and mortality significantly increase once Pulmonary Hypertension is present. Treatment is aimed toward optimizing the underlying condition. Targeted therapy has been evaluated in small studies with mixed results. The goal of this systematic review is to identify the possible benefit and safety of Phosphodiesterase 5 inhibitors in Pulmonary Hypertension due to left heart disease with elevated pulmonary vascular resistance, diagnosed by right heart catheterization. Electronic searches using MEDLINE/PREMEDLINE, EMBASE, and The Cochrane Library were searched on 21 October 2018. Randomized clinical trials comparing Phosphodiesterase 5 inhibitors versus placebo in patients with proven Pulmonary Hypertension by right heart catheterization secondary to left heart disease (both heart failure with reduced ejection fraction and with preserved ejection fraction) and reported pulmonary vascular resistance were included. We identified 436 potentially relevant studies. After reviewing the titles and abstracts to exclude irrelevant articles, five randomized clinical trials were considered for the study. Sildenafil was well tolerated among all studies. Sildenafil was found to improve hemodynamics, exercise capacity, and quality of life in patients with elevated pulmonary vascular resistance. Phosphodiesterase 5 inhibitors therapy in patients with proven Pulmonary Hypertension due to left heart disease and elevated pulmonary vascular resistance by right heart catheterization may improve the quality of life, exercise capacity, and pulmonary hemodynamics. Further prospective randomized controlled studies are needed to confirm.

Cardiac Cyclic Nucleotide Phosphodiesterases: Roles and Therapeutic Potential in Heart Failure

The cyclic nucleotides cyclic adenosine-3′,5′-monophosphate (cAMP) and cyclic guanosine-3′,5′-monophosphate (cGMP) maintain physiological cardiac contractility and integrity. Cyclic nucleotide–hydrolysing phosphodiesterases (PDEs) are the prime regulators of cAMP and cGMP signalling in the heart. During heart failure (HF), the expression and activity of multiple PDEs are altered, which disrupt cyclic nucleotide levels and promote cardiac dysfunction. Given that the morbidity and mortality associated with HF are extremely high, novel therapies are urgently needed. Herein, the role of PDEs in HF pathophysiology and their therapeutic potential is reviewed. Attention is given to PDEs 1–5, and other PDEs are briefly considered. After assessing the role of each PDE in cardiac physiology, the evidence from pre-clinical models and patients that altered PDE signalling contributes to the HF phenotype is examined. The potential of pharmacologically harnessing PDEs for therapeutic gain is considered.

Pulmonary vascular resistance as a potential marker of reactive pulmonary hypertension reduction following sildenafil therapy in patients disqualified from orthotopic heart transplantation

PURPOSE

We sought to determine the predictors of restoration of heart transplantation (HTx) candidacy in patients with systolic heart failure (HF) and reactive fixed pulmonary hypertension (RFPH) defined as pulmonary vascular resistance (PVR) > 2.5 Wood units (WU), transpulmonary gradient (TPG) > 12 mmHg or ≤2.5 WU with systolic arterial pressure ≤85 mmHg during vasoreactivity test, following sildenafil therapy.

MATERIAL AND METHODS

Between 2007 and 2018 1136 patients were evaluated at our department as candidates for HTx. Thirty-five of them, who presented with systolic HF and were not eligible for HTx due to RFPH, were included in the study (31 men aged 55.1 ± 7.4 years). In all the patients sildenafil was introduced and up-titrated to a maximal tolerated dose in addition to optimal medical therapy. Patients were assessed at 3-6 months intervals.

RESULTS

During median 11 months (interquartile range 6-18 months) reduction of RFPH enabling qualification for HTx was observed in 62.9% patients. Higher baseline PVR (OR 0.32; 95% CI (0.14-0.74) p < 0.001), pulmonary artery systolic pressure (PASP) (OR 0.94, 95% CI (0.88-0.99) p = 0.05), mean artery pulmonary pressure (mPAP) (OR 0.87, 95% CI (0.77-0.98) p = 0.02) and TPG (OR 082, 95% CI (0.70-0.96) p = 0.003) were negative predictors of RFPH reduction with sildenafil therapy. In multivariable analysis, lower PVR (p = 0.02) was identified as an independent predictor of RFPH reduction following sildenafil therapy.

CONCLUSION

Sildenafil therapy can support PH reduction in systolic HF patients uneligible for HTx due to RFPH. Lower baseline PVR was identified as an independent predictor of PH reversibility with sildenafil enabling restoration of HTx candidacy.

Peripheral endothelial dysfunction is a novel risk factor for systolic dysfunction and heart failure progression

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Peripheral endothelial dysfunction (PED) predicts adverse outcomes in patients with stage B HF.

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PED was independently associated with stage B HF, even after adjusting for co-variables.

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PED was strongly associated with progression from stage B to overt stage C HF.

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Detecting PED may stratify the risk of HF progression.

Background

ACC/AHA guidelines recognize the progressive nature of heart failure (HF). Patients with risk factors (Stage A) are at risk for developing asymptomatic cardiac dysfunction (Stage B), which may then lead to symptomatic HF (Stage C). As such, therapies targeting abnormalities in stages A and B may protect against development of symptomatic HF. peripheral endothelial dysfunction (PED) is an independent predictor of adverse outcomes in patients with stage C HF. The aim of the current study was to evaluate whether PED might be associated with Stage B HF, where therapeutic interventions to prevent progression might be more efficacious.

Methods

We performed a retrospective cross-sectional analysis of patients who were referred for routine cardiovascular evaluation that included an assessment of peripheral endothelial function with reactive hyperemia-peripheral arterial tonometry. Individuals in this study underwent routine clinically indicated echocardiography within 2 months of testing for PED. Patients with clinical HF were excluded.

Results

The study included 355 patients (mean age 51.5 ± 14.6 years, 231 (65.1%) female). There was a significant association between PED and Stage B HF (Odds Ratio (OR) 6.38; P < 0.0001) that persisted after stratifying by sex. In multivariate analyses PED was significantly associated with Stage B HF (OR 5.33; P = 0.0038), and was also associated with progression to overt stage C HF (OR 4.63; P = 0.033).

Conclusion

Peripheral endothelial dysfunction is risk factor for Stage B HF, even in low risk individuals. Further study is warranted to better understand the mechanistic basis of PED in HF to reduce the risk of symptomatic progression.

Pulmonary Hypertension Due to Left Heart Disease

Pulmonary hypertension (PH) due to left heart disease (LHD) is the most common type of PH and is defined as mean pulmonary artery systolic pressure of >20 mm Hg and pulmonary capillary wedge pressure >15 mm Hg during right heart catheterization. LHD may lead to elevated left atrial pressure alone, which in the absence of intrinsic pulmonary vascular disease will result in PH without changes in pulmonary vascular resistance. Persistent elevation in left atrial pressure may, however, also be associated with subsequent pulmonary vascular remodeling, vasoconstriction, and an increase in pulmonary vascular resistance. Hence, there are 2 subgroups of PH due to LHD, isolated postcapillary PH and combined post- and precapillary PH, with these groups have differing clinical implications. Differentiation of pulmonary arterial hypertension and PH due to LHD is critical to guide management planning; however, this may be challenging. Older patients, patients with metabolic syndrome, and patients with imaging and clinical features consistent with left ventricular dysfunction are suggestive of LHD etiology rather than pulmonary arterial hypertension. Hemodynamic measures such as diastolic pressure gradient, transpulmonary gradient, and pulmonary vascular resistance may assist to differentiate pre- from postcapillary PH and offer prognostic insights. However, these are influenced by fluid status and heart failure treatment. Pulmonary arterial hypertension therapies have been trialed in the treatment with concerning results reflecting disease heterogeneity, variation in inclusion criteria, and mixed end point criteria. The aim of this review is to provide an updated definition, discuss possible pathophysiology, clinical aspects, and the available treatment options for PH due to LHD.

Effects of PDE-5 Inhibition on the Cardiopulmonary System After 2 or 4 Weeks of Chronic Hypoxia

Purpose

In pulmonary hypertension (PH), hypoxia represents both an outcome and a cause of exacerbation. We addressed the question whether hypoxia adaptation might affect the mechanisms underlying PH alleviation through phosphodiesterase-5 (PDE5) inhibition.

Methods

Eight-week-old male Sprague-Dawley rats were divided into two groups depending on treatment (placebo or sildenafil, a drug inhibiting PDE5) and were exposed to hypoxia (10% O₂) for 0 (t0, n = 9/10), 2 (t2, n = 5/5) or 4 (t4, n = 5/5) weeks. The rats were treated (0.3 mL i.p.) with either saline or sildenafil (1.4 mg/Kg per day).

Results

Two-week hypoxia changed the body weight (− 31% vs. − 27%, respectively, P = NS), blood hemoglobin (+ 25% vs. + 27%, P = NS) and nitrates+nitrites (+ 175% vs. + 261%, P = 0.007), right ventricle fibrosis (+ 814% vs. + 317%, P < 0.0001), right ventricle hypertrophy (+ 84% vs. + 49%, P = 0.007) and systolic pressure (+ 108% vs. + 41%, P = 0.001), pulmonary vessel density (+ 61% vs. + 46%, P = NS), and the frequency of small (< 50 µm wall thickness) vessels (+ 35% vs. + 13%, P = 0.0001). Most of these changes were maintained for 4-week hypoxia, except blood hemoglobin and right ventricle hypertrophy that continued increasing (+ 52% vs. + 42%, P = NS; and + 104% vs. + 83%, P = 0.04). To further assess these observations, small vessel frequency was found to be linearly related with the right ventricle-developed pressure independent of hypoxia duration.

Conclusions

Thus, although hypoxia adaptation is not yet accomplished after 4 weeks, PH alleviation by PDE5 inhibition might nevertheless provide an efficient strategy for the management of this disease.

Pulmonary Hypertension in Heart Failure Patients

The development of pulmonary hypertension (PH) in patients with heart failure is associated with increased morbidity and mortality. In this article, the authors examine recent changes to the definition of PH in the setting of left heart disease (PH-LHD), and discuss its epidemiology, pathophysiology and prognosis. They also explore the complexities of diagnosing PH-LHD and the current evidence for the use of medical therapies, promising clinical trials and the role of left ventricular assist device and transplantation.

Asymptomatic Left Ventricle Systolic Dysfunction

Heart failure is a common debilitating illness, associated with significant morbidity and mortality, rehospitalisation and societal costs. Current guidelines and position statements emphasise the management of patients with overt symptomatic disease, but the increasing prevalence of congestive heart failure underscores the need to identify and manage patients with early left ventricular dysfunction prior to symptom onset. Asymptomatic left ventricular systolic dysfunction (ALVSD), classified as stage B heart failure, is defined as depressed left ventricular systolic function in the absence of clinical heart failure. Early initiation of therapies in patients with presumed ALVSD has been shown to lead to better outcomes. In this article, the authors clarify issues surrounding the definition and natural history of ALVSD, outline clinical tools that may be of value in identifying patients with ALVSD and highlight potential opportunities for future investigations to better address aspects of our understanding of this complex syndrome.

Sildenafil for improving outcomes in patients with corrected valvular heart disease and persistent pulmonary hypertension: a multicenter, double-blind, randomized clinical trial

Aims

We aimed to determine whether treatment with sildenafil improves outcomes of patients with persistent pulmonary hypertension (PH) after correction of valvular heart disease (VHD).

Methods and results

The sildenafil for improving outcomes after valvular correction (SIOVAC) study was a multricentric, randomized, parallel, and placebo-controlled trial that enrolled stable adults with mean pulmonary artery pressure ≥ 30 mmHg who had undergone a successful valve replacement or repair procedure at least 1 year before inclusion. We assigned 200 patients to receive sildenafil (40 mg three times daily, n = 104) or placebo (n = 96) for 6 months. The primary endpoint was the composite clinical score combining death, hospital admission for heart failure (HF), change in functional class, and patient global self-assessment. Only 27 patients receiving sildenafil improved their composite clinical score, as compared with 44 patients receiving placebo; in contrast 33 patients in the sildenafil group worsened their composite score, as compared with 14 in the placebo group [odds ratio 0.39; 95% confidence interval (CI) 0.22–0.67; P < 0.001]. The Kaplan–Meier estimates for survival without admission due to HF were 0.76 and 0.86 in the sildenafil and placebo groups, respectively (hazard ratio 2.0, 95% CI = 1.0–4.0; log-rank P = 0.044). Changes in 6-min walk test distance, natriuretic peptides, and Doppler-derived systolic pulmonary pressure were similar in both groups.

Conclusion

Treatment with sildenafil in patients with persistent PH after successfully corrected VHD is associated to worse clinical outcomes than placebo. Off-label usage of sildenafil for treating this source of left heart disease PH should be avoided.

The trial is registered with ClinicalTrials.gov, number NCT00862043.

Pulmonary hypertension in HFpEF and HFrEF: Pathophysiology, diagnosis, treatment approaches

Pulmonary hypertension (PH) is a frequent hemodynamic condition that is highly prevalent in patients with heart failure and reduced (HFrEF) or preserved ejection fraction (HFpEF). Irrespective of left ventricular EF, the presence of PH and right ventricular (RV) dysfunction are highly relevant for morbidity and mortality in patients with heart failure. While elevated left-sided filling pressures and functional mitral regurgitation primarily lead to post-capillary PH, current guidelines and recommendations distinguish between isolated post-capillary PH (IpcPH) and combined post- and pre-capillary PH (CpcPH), the latter being defined by a pulmonary vascular resistance (PVR) of ≥3 Wood units. Here, we describe the pathophysiology and clinical relevance of these distinct entities, and report on the diagnostic work-up including remote pulmonary artery pressure (PAP) monitoring. Furthermore, we highlight strategies to manage PH and improve RV function in heart failure, which may include optimized management of HFrEF and HFpEF (medical and interventional), sufficient volume control, catheter-based mitral valve repair, and-in selected cases-targeted PH therapy. In this context, we also highlight gaps in evidence and the need for further research.

Challenges in pulmonary hypertension associated with left heart disease

Introduction: Pulmonary hypertension (PH) secondary to left-sided heart disease (Group 2 PH) is a frequent complication of heart failure (HF) and is a heterogeneous phenotypic disorder that worsens exercise capacity, increases risk for hospitalization and survival independent of left ventricular ejection fraction (LVEF) or stage of HF. Areas covered: In this review, an update of the current knowledge and some potential challenges about the pathophysiology and treatments of group 2 PH in patients with HF of either preserved or reduced ejection fraction are provided. Also, this review discusses the epidemiology and provides hints for the optimal evaluation and diagnosis of these patients to prevent misclassification of their pulmonary hypertension. Expert opinion: There are many of areas lacking knowledge and understanding in the field of pulmonary hypertension associated to left heart disease (PH-LHD) that should be addressed in the future. Further research should be performed, in terms of pathobiology, and understanding the predisposition (genetic susceptibility and contributing factors) of the different phenotypes of this disorder. More clinical trials targeting new therapeutic options and specific PH therapies are warranted to help this increasing important patient group as the current guidelines recommend to only treat the underlying left-sided heart disease.

Intersection of Pulmonary Hypertension and Right Ventricular Dysfunction in Patients on Left Ventricular Assist Device Support: Is There a Role for Pulmonary Vasodilators?

Left ventricular assist devices (LVADs) improve survival and quality of life in patients with advanced heart failure. Despite these benefits, combined post- and precapillary pulmonary hypertension can be particularly problematic in patients on LVAD support, often exacerbating right ventricular (RV) dysfunction. Both persistently elevated pulmonary vascular resistance and RV dysfunction are associated with adverse outcomes, including death after LVAD. These observations have led to significant interest in the use of pulmonary vasodilators to treat pulmonary hypertension and preserve RV function among LVAD-supported patients. Although pulmonary vasodilators are commonly used for the treatment of pulmonary hypertension and RV dysfunction in LVADs, the benefits of this practice remain unclear. The purpose of this review is to highlight the current challenges in managing pulmonary vascular disease and RV dysfunction in patients with heart failure on LVAD support.

Effect of prolonged treatment with phosphodiesterase-5-inhibitors on endothelial dysfunction in vascular diseases and vascular risk conditions: A systematic review analysis and meta-analysis of randomized double-blind placebo-controlled trials

OBJECTIVE

To challenge the argument that continuous use of phosphodiesterase-5-selective inhibitors may reduce endothelial cell dysfunction in patients with vascular diseases or vascular risk conditions.

DESIGN

This study included systematic reviews and meta-analysis of randomized double-blind placebo-controlled trials dealing with the prolonged use of phosphodiesterase-5-selective inhibitors. The risk of bias and quality of trials were assessed by the Cochrane algorithm. Fixed or random effect models, standardised mean differences and heterogeneity were estimated in the study.

DATA SOURCES

Systematic search for randomized double-blind placebo-controlled trials was done in PubMed, Scopus, CINAHL, Science direct and the Cochrane Library.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomized double-blind placebo-controlled trials reporting measures of endothelial cell dysfunction and/or endothelial cell activation were included.

RESULTS

On the whole, 469 subjects were allocated to the phosphodiesterase-5-selective inhibitor group, while 463 were assigned to the placebo group in 13 randomized double-blind placebo-controlled trials. Flow-mediated dilation of the brachial artery was found to improve after the administration of phosphodiesterase-5-selective inhibitors (P < 0.0001). The results were questioned by the elevated and uncorrectable heterogeneity (I²  = 92%) and the asymmetry of the funnel plot suggested a publication bias. Phosphodiesterase-5-selective inhibitors have no effect on endothelial cell dysfunction, as assessed in the resistance vessels by digital arterial tonometry. The blood level of endothelin-1 was observed to be decreased in phosphodiesterase-5-selective inhibitors arm (P = 0.03), although the effect disappeared once the publication bias and heterogeneity were corrected. The effect of phosphodiesterase-5-selective inhibitors on biomarkers of endothelial cell activation was found to be inconsistent.

CONCLUSIONS

The results on the benefits of a prolonged use of phosphodiesterase-5-selective inhibitors, with the objective of lowering endothelial cell dysfunction in patients with vascular diseases or vascular risk conditions are not convincing. This is because of the overall low quality of evidence, giving an unclear scientific support to this treatment. Systematic review registration: PROSPERO registration: CRD42017055399.

Phosphodiesterase 5 inhibitors for pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) comprises a group of complex and heterogenous conditions, characterised by elevated pulmonary artery pressure, and which left untreated leads to right-heart failure and death. PH includes World Health Organisation (WHO) Group 1 pulmonary arterial hypertension (PAH); Group 2 consists of PH due to left-heart disease (PH-LHD); Group 3 comprises PH as a result of lung diseases or hypoxia, or both; Group 4 includes PH due to chronic thromboembolic occlusion of pulmonary vasculature (CTEPH), and Group 5 consists of cases of PH due to unclear and/or multifactorial mechanisms including haematological, systemic, or metabolic disorders. Phosphodiesterase type 5 (PDE5) inhibitors increase vasodilation and inhibit proliferation.

OBJECTIVES

To determine the efficacy of PDE5 inhibitors for pulmonary hypertension in adults and children.

SEARCH METHODS

We performed searches of CENTRAL, MEDLINE, Embase, CINAHL, and Web of Science up to 26 September 2018. We handsearched review articles, clinical trial registries, and reference lists of retrieved articles.

SELECTION CRITERIA

We included randomised controlled trials that compared any PDE5 inhibitor versus placebo, or any other PAH disease-specific therapies, for at least 12 weeks. We include separate analyses for each PH group.

DATA COLLECTION AND ANALYSIS

We imported studies identified by the search into a reference manager database. We retrieved the full-text versions of relevant studies, and two review authors independently extracted data. Primary outcomes were: change in WHO functional class, six-minute walk distance (6MWD), and mortality. Secondary outcomes were haemodynamic parameters, quality of life/health status, dyspnoea, clinical worsening (hospitalisation/intervention), and adverse events. When appropriate, we performed meta-analyses and subgroup analyses by severity of lung function, connective tissue disease diagnosis, and radiological pattern of fibrosis. We assessed the evidence using the GRADE approach and created 'Summary of findings' tables.

MAIN RESULTS

We included 36 studies with 2999 participants (with pulmonary hypertension from all causes) in the final review. Trials were conducted for 14 weeks on average, with some as long as 12 months. Two trials specifically included children.Nineteen trials included group 1 PAH participants. PAH participants treated with PDE5 inhibitors were more likely to improve their WHO functional class (odds ratio (OR) 8.59, 95% confidence interval (CI) 3.95 to 18.72; 4 trials, 282 participants), to walk 48 metres further in 6MWD (95% CI 40 to 56; 8 trials, 880 participants), and were 22% less likely to die over a mean duration of 14 weeks (95% CI 0.07 to 0.68; 8 trials, 1119 participants) compared to placebo (high-certainty evidence). The number needed to treat to prevent one additional death was 32 participants. There was an increased risk of adverse events with PDE5 inhibitors, especially headache (OR 1.97, 95% CI 1.33 to 2.92; 5 trials, 848 participants), gastrointestinal upset (OR 1.63, 95% CI 1.07 to 2.48; 5 trials, 848 participants), flushing (OR 4.12, 95% CI 1.83 to 9.26; 3 trials, 748 participants), and muscle aches and joint pains (OR 2.52, 95% CI 1.59 to 3.99; 4 trials, 792 participants).Data comparing PDE5 inhibitors to placebo whilst on other PAH-specific therapy were limited by the small number of included trials. Those PAH participants on PDE5 inhibitors plus combination therapy walked 19.66 metres further in six minutes (95% CI 9 to 30; 4 trials, 509 participants) compared to placebo (moderate-certainty evidence). There were limited trials comparing PDE5 inhibitors directly with other PAH-specific therapy (endothelin receptor antagonists (ERAs)). Those on PDE5 inhibitors walked 49 metres further than on ERAs (95% CI 4 to 95; 2 trials, 36 participants) (low-certainty evidence). There was no evidence of a difference in WHO functional class or mortality across both treatments.Five trials compared PDE5 inhibitors to placebo in PH secondary to left-heart disease (PH-LHD). The quality of data were low due to imprecision and inconsistency across trials. In those with PH-LHD there were reduced odds of an improvement in WHO functional class using PDE5 inhibitors compared to placebo (OR 0.53, 95% CI 0.32 to 0.87; 3 trials, 285 participants), and those using PDE5 inhibitors walked 34 metres further compared to placebo (95% CI 23 to 46; 3 trials, 284 participants). There was no evidence of a difference in mortality. Five trials compared PDE5 inhibitors to placebo in PH secondary to lung disease/hypoxia, mostly in COPD. Data were of low quality due to imprecision of effect and inconsistency across trials. There was a small improvement of 27 metres in 6MWD using PDE5 inhibitors compared to placebo in those with PH due to lung disease. There was no evidence of worsening hypoxia using PDE5 inhibitors, although data were limited. Three studies compared PDE5 inhibitors to placebo or other PAH-specific therapy in chronic thromboembolic disease. There was no significant difference in any outcomes. Data quality was low due to imprecision of effect and heterogeneity across trials.

AUTHORS' CONCLUSIONS

PDE5 inhibitors appear to have clear beneficial effects in group 1 PAH. Sildenafil, tadalafil and vardenafil are all efficacious in this clinical setting, and clinicians should consider the side-effect profile for each individual when choosing which PDE5 inhibitor to prescribe.While there appears to be some benefit for the use of PDE5 inhibitors in PH-left-heart disease, it is not clear based on the mostly small, short-term studies, which type of left-heart disease stands to benefit. These data suggest possible harm in valvular heart disease. There is no clear benefit for PDE5 inhibitors in pulmonary hypertension secondary to lung disease or chronic thromboembolic disease. Further research is required into the mechanisms of pulmonary hypertension secondary to left-heart disease, and cautious consideration of which subset of these patients may benefit from PDE5 inhibitors. Future trials in PH-LHD should be sufficiently powered, with long-term follow-up, and should include invasive haemodynamic data, WHO functional class, six-minute walk distance, and clinical worsening.

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.

Pulmonary hypertension-targeted therapies in heart failure: A systematic review and meta-analysis

Background

Pulmonary hypertension (PH) due to left heart failure (HF) is the most common form of PH. However, treatment is unclear because there are conflicting results about safety and efficacy of PH-targeted therapies.

Objectives

To assess the effects of PH-targeted therapy on exercise capacity in HF patients.

Methods

MEDLINE, EMBASE and the Cochrane Library were searched from January 1990 to July 2017 for randomized controlled trials comparing PH-targeted therapies to conventional therapy in HF. The primary outcome was to assess the effects on exercise capacity. Secondary outcomes included mortality, hospitalisation, NT-proBNP levels, echocardiographic and hemodynamics parameters and discontinuation rate.

Results

22 studies were included (n = 5448), including 3, 8 and 11 studies with low, high and unknown risk of bias, respectively. PH-targeted therapies were associated with an improvement of exercise capacity (standardized mean difference 0.29;95%CI:0.08–0.50, p = 0.006). Pre-specified subgroup analyses found that this improvement was predominantly observed in studies evaluating phosphodiesterase-5 inhibitors and prostanoids and in patients with reduced ejection fraction. Moreover, systolic pulmonary artery pressure measured by echocardiography was improved (mean difference: -7.5mmHg; [95%CI]: -14.9,-0.1, p = 0.05), which was also entirely driven by studies evaluating phosphodiesterase-5 inhibitors. However, PH-targeted therapies were associated with an increased treatment discontinuation rates and a potential increase in mortality compared to standard treatment.

Conclusions

In conclusion, PH-targeted therapies and especially phosphodiesterase-5 inhibitors may improve exercise capacity in patients with HF. However, an increase in adverse outcomes was likely. Moreover, most studies were at high or unknown risk of bias, precluding confident conclusions about the effects of PH-targeted therapies.

Pulmonary hypertension associated with left heart disease: Updated Recommendations of the Cologne Consensus Conference 2018

In the summer of 2016, delegates from the German Society of Cardiology (DGK), the German Respiratory Society (DGP), and the German Society of Pediatric Cardiology (DGPK) met in Cologne, Germany, to define consensus-based practice recommendations for the management of patients with pulmonary hypertension (PH). These recommendations were built on the 2015 European Pulmonary Hypertension guidelines, aiming at their practical implementation, considering country-specific issues, and including new evidence, where available. To this end, a number of working groups was initiated, one of which was specifically dedicated to PH associated with left heart disease. In this context, the European Guidelines point out that the drugs currently approved to treat patients with PAH (prostanoids, endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, sGC stimulators) have not sufficiently been investigated in other forms of PH. However, despite the lack of respective efficacy data, an uncritical use of targeted PAH drugs in patients with PH associated with left heart disease is currently observed at an increasing rate. This development is a matter of concern. On the other hand, PH is a frequent problem that is highly relevant for morbidity and mortality in patients with left heart disease. In that sense, the distinction between isolated post-capillary pulmonary hypertension (IpcPH) and combined post- and pre-capillary pulmonary hypertension (CpcPH) and their proper definition may be of particular relevance. The detailed results and recommendations of the working group on PH associated with left heart disease, which were last updated in the spring of 2018, are summarized in this article.

Haemodynamics, dyspnoea, and pulmonary reserve in heart failure with preserved ejection fraction

Aims

Increases in left ventricular filling pressure are a fundamental haemodynamic abnormality in heart failure with preserved ejection fraction (HFpEF). However, very little is known regarding how elevated filling pressures cause pulmonary abnormalities or symptoms of dyspnoea. We sought to determine the relationships between simultaneously measured central haemodynamics, symptoms, and lung ventilatory and gas exchange abnormalities during exercise in HFpEF.

Methods and results

Subjects with invasively-proven HFpEF (n = 50) and non-cardiac causes of dyspnoea (controls, n = 24) underwent cardiac catheterization at rest and during exercise with simultaneous expired gas analysis. During submaximal (20 W) exercise, subjects with HFpEF displayed higher pulmonary capillary wedge pressures (PCWP) and pulmonary artery pressures, higher Borg perceived dyspnoea scores, and increased ventilatory drive and respiratory rate. At peak exercise, ventilation reserve was reduced in HFpEF compared with controls, with greater dead space ventilation (higher VD/VT). Increasing exercise PCWP was directly correlated with higher perceived dyspnoea scores, lower peak exercise capacity, greater ventilatory drive, worse New York Heart Association (NYHA) functional class, and impaired pulmonary ventilation reserve.

Conclusion

This study provides the first evidence linking altered exercise haemodynamics to pulmonary abnormalities and symptoms of dyspnoea in patients with HFpEF. Further study is required to identify the mechanisms by which haemodynamic derangements affect lung function and symptoms and to test novel therapies targeting exercise haemodynamics in HFpEF.

Phosphodiesterase 2 inhibition preferentially promotes NO/guanylyl cyclase/cGMP signaling to reverse the development of heart failure

Heart failure (HF) is a shared manifestation of several cardiovascular pathologies, including hypertension and myocardial infarction, and a limited repertoire of treatment modalities entails that the associated morbidity and mortality remain high. Impaired nitric oxide (NO)/guanylyl cyclase (GC)/cyclic guanosine-3',5'-monophosphate (cGMP) signaling, underpinned, in part, by up-regulation of cyclic nucleotide-hydrolyzing phosphodiesterase (PDE) isozymes, contributes to the pathogenesis of HF, and interventions targeted to enhancing cGMP have proven effective in preclinical models and patients. Numerous PDE isozymes coordinate the regulation of cardiac cGMP in the context of HF; PDE2 expression and activity are up-regulated in experimental and human HF, but a well-defined role for this isoform in pathogenesis has yet to be established, certainly in terms of cGMP signaling. Herein, using a selective pharmacological inhibitor of PDE2, BAY 60-7550, and transgenic mice lacking either NO-sensitive GC-1α (GC-1α^-/-) or natriuretic peptide-responsive GC-A (GC-A^-/-), we demonstrate that the blockade of PDE2 promotes cGMP signaling to offset the pathogenesis of experimental HF (induced by pressure overload or sympathetic hyperactivation), reversing the development of left ventricular hypertrophy, compromised contractility, and cardiac fibrosis. Moreover, we show that this beneficial pharmacodynamic profile is maintained in GC-A^-/- mice but is absent in animals null for GC-1α or treated with a NO synthase inhibitor, revealing that PDE2 inhibition preferentially enhances NO/GC/cGMP signaling in the setting of HF to exert wide-ranging protection to preserve cardiac structure and function. These data substantiate the targeting of PDE2 in HF as a tangible approach to maximize myocardial cGMP signaling and enhancing therapy.

cGMP at the centre of attention: emerging strategies for activating the cardioprotective PKG pathway

The nitric oxide (NO)-protein kinase G (PKG) pathway has been known for some time to be an important target for cardioprotection against ischaemia/reperfusion injury and heart failure. While many approaches for reducing infarct size in patients have failed in the past, the advent of novel drugs that modulate cGMP and its downstream targets shows very promising results in recent preclinical and clinical studies. Here, we review main aspects of the NO-PKG pathway in light of recent drug development and summarise potential cardioprotective strategies in which cGMP is the main player.

Phosphodiesterase-5 Inhibition Alleviates Pulmonary Hypertension and Basal Lamina Thickening in Rats Challenged by Chronic Hypoxia

Background: Hypoxia represents both an outcome of cardiopulmonary diseases and a trigger for severe pulmonary complications as pulmonary hypertension. Because nitric oxide (NO) is a critical mediator in the development of pulmonary hypertension, the modulators of its downstream function may become target of pharmacological interventions aimed at alleviating the impact of this condition. Here, we investigate the effects of an early administration of phosphodiesterase-5 inhibitor in rats where pulmonary artery hypertension was induced by chronic exposure to hypoxia.

Methods: Rats were divided into three groups: normoxic control, hypoxic with no treatments (2 weeks breathing an atmosphere containing 10% oxygen), and hypoxic treated with sildenafil (1.4 mg/Kg per day in 0.3 mL i.p.). After sacrifice, hearts and lungs were removed and harvested for analyses.

Results: Sildenafil reduced hypoxia-induced right ventricle hypertrophy without effects in lung hypertrophy, and blunted the increase in right ventricle pressure without effects on left ventricle pressure. Furthermore, the NO-producing systems (i.e., the phosphorylation of the endothelial isoforms of NO synthase that was measured in both myocardial and lung tissues), and the blood NO stores (i.e., the plasma level of nitrates and nitrites) were up-regulated by sildenafil. We did not find significant effects of sildenafil on weight and hemoglobin concentration. Morphological analysis in lung biopsies revealed that 2-week hypoxia increased the frequency of small pulmonary vessels leaving large vessels unaffected. Finally, ultrastructural analysis showed that sildenafil down-regulated the hypoxia-induced increase in the thickness of the pulmonary basal lamina.

Conclusions: In this model of pulmonary hypertension, sildenafil contrasts the negative effects of hypoxia on pulmonary vascular and right ventricle remodeling. This action does not only encompass the canonical vasomodulatory effect, but involves several biochemical pathways. Although the human pathological model is certainly more complex than that described here (for example, the inflammatory issue), the potential role of phosphodiesterase-5 for long-term treatment, and perhaps prevention, of pulmonary hypertension is worthy of investigation.

Visceral Congestion in Heart Failure: Right Ventricular Dysfunction, Splanchnic Hemodynamics, and the Intestinal Microenvironment

PURPOSE OF REVIEW

Visceral venous congestion of the gut may play a key role in the pathogenesis of right-sided heart failure (HF) and cardiorenal syndromes. Here, we review the role of right ventricular (RV) dysfunction, visceral congestion, splanchnic hemodynamics, and the intestinal microenvironment in the setting of right-sided HF. We review recent literature on this topic, outline possible mechanisms of disease pathogenesis, and discuss potential therapeutics.

RECENT FINDINGS

There are several mechanisms linking RV-gut interactions via visceral venous congestion which could result in (1) hypoxia and acidosis in enterocytes, which may lead to enhanced sodium-hydrogen exchanger 3 (NHE3) expression with increased sodium and fluid retention; (2) decreased luminal pH in the intestines, which could lead to alteration of the gut microbiome which could increase gut permeability and inflammation; (3) alteration of renal hemodynamics with triggering of the cardiorenal syndrome; and (4) altered phosphate metabolism resulting in increased pulmonary artery stiffening, thereby increasing RV afterload. A wide variety of therapeutic interventions that act on the RV, pulmonary vasculature, intestinal microenvironment, and the kidney could alter these pathways and should be tested in patients with right-sided HF. The RV-gut axis is an important aspect of HF pathogenesis that deserves more attention. Modulation of the pathways interconnecting the right heart, visceral congestion, and the intestinal microenvironment could be a novel avenue of intervention for right-sided HF.

Echocardiographic validation of pulmonary hypertension due to heart failure with reduced ejection fraction in mice

Pulmonary hypertension (PH) associated with left heart diseases is the most prevalent cause of PH. The scarcity of studies exploring the pathophysiology and therapies of group II PH resides in the lack of validated small animal models with non-invasive determination of the presence and severity of PH. Heart failure (HF) was induced in mice by coronary artery ligation. Mice developed PH as evidenced by an elevated right ventricular (RV) systolic pressure and RV hypertrophy. Detailed non-invasive echocardiographic analysis on the left and right ventricles showed impaired left ventricular (LV) systolic and diastolic function. In addition, RV hypertrophy was confirmed by echo and accompanied by impaired function as well as increased pulmonary resistance. Correlation analysis validated the use of the LV wall-motion score index (WMSI) at a threshold value of ≥2.0 as a powerful and reliable indicator for the presence of PH and RV dysfunction. Echocardiography is an accurate non-invasive technique to diagnose PH in a HF mouse model. Moreover, an echocardiographic parameter of infarct size and LV function, the LV WMSI, reliably correlates with the presence of PH, RV hypertrophy and RV dysfunction and could be used to improve efficiency and design of pre-clinical studies.

Targeting phosphodiesterase 5 as a therapeutic option against myocardial ischaemia/reperfusion injury and for treating heart failure

Phosphodiesterase type 5 (PDE5) selectively hydrolyses the second messenger cGMP into 5'-GMP, thereby regulating its intracellular concentrations. Dysregulation of the cGMP-dependent pathway plays a significant role in various cardiovascular diseases. Therefore, its modulation by drugs, such as PDE5 inhibitors, may represent an effective therapeutic approach. There are currently four PDE5 inhibitors available for the treatment of erectile dysfunction: sildenafil, vardenafil, tadalafil and avanafil. Sildenafil and tadalafil have also received Food and Drug Administration approval for the treatment of pulmonary arterial hypertension. This review summarizes the pharmacological aspects and clinical potential of PDE5 inhibition for the treatment of myocardial ischaemia/reperfusion injury and heart failure.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Pulmonary Hypertension in the Era of Mechanical Circulatory Support

Left heart disease (LHD) represents the most common cause of pulmonary hypertension (PH), and is associated with worse prognosis compared with LHD without PH. In addition, PH due to LHD may prevent patients from receiving heart transplantation, because of risk of perioperative right ventricular failure. Current literature lacks comprehensive descriptions and management strategies of PH due to LHD. In this review, we summarize the literature that is available to highlight the definition, pathogenesis, and prognosis of PH due to LHD. Furthermore, we discuss the use of mechanical circulatory support (MCS) in this population. Finally, we provide recommendations regarding the management and reassessment of PH due to LHD in the specific context of MCS.

Therapeutic benefits of phosphodiesterase-5 inhibition in chronic heart failure: A meta-analysis

Background

Phosphodiesterase-5 inhibitors (PDE5i) have been shown to be beneficial for patients with pulmonary arterial hypertension. However, several studies would have documented a useful effect of PDE5i even for pulmonary hypertension secondary to left-sided chronic heart failure (CHF).

Methods

We performed a meta-analysis including randomized controlled trials (RCTs) which had compared PDE5i (mostly sildenafil) and placebo in CHF patients.

Results

Fourteen studies enrolling a total of 928 patients were incorporated in the meta-analysis. In heart failure with reduced left ventricular ejection fraction (HFREF), PDE5i, compared to placebo, significantly improved the composite of death and hospitalization (OR = 0.28; 95% CI: 0.10–0.74). They also improved peak VO₂ [difference in means (MD): 3.76; 95% CI: 3.27–4.25], six-minute walking distance test (MD: 22.7 m; 95% CI: 8.19–37.21), and pulmonary arterial systolic pressure (MD: −11.52 mmHg; 95% CI: −15.56 to −7.49). Conversely, in CHF with preserved left ventricular ejection fraction (HFpEF), PDE5i proved not to yield any significant improvement of the investigated outcomes.

Conclusions

In HFREF, PDE5i showed beneficial effects on the composite of death and hospitalization, as well as on exercise capacity and pulmonary hemodynamics. Conversely, in HFpEF, no significant clinical, spiroergometric, or hemodynamic improvement was achieved using PDE5i therapy.

Pulmonary hypertension due to left heart disease causes intrapulmonary venous arterialization in rats

OBJECTIVE

A rat model of left atrial stenosis-associated pulmonary hypertension due to left heart diseases was prepared to elucidate its mechanism.

METHODS

Five-week-old Sprague-Dawley rats were randomly divided into 2 groups: left atrial stenosis and sham-operated control. Echocardiography was performed 2, 4, 6, and 10 weeks after surgery, and cardiac catheterization and organ excision were subsequently performed at 10 weeks after surgery.

RESULTS

Left ventricular inflow velocity, measured by echocardiography, significantly increased in the left atrial stenosis group compared with that in the sham-operated control group (2.2 m/s, interquartile range [IQR], 1.9-2.2 and 1.1 m/s, IQR, 1.1-1.2, P < .01), and the right ventricular pressure-to-left ventricular systolic pressure ratio significantly increased in the left atrial stenosis group compared with the sham-operated control group (0.52, IQR, 0.54-0.60 and 0.22, IQR, 0.15-0.27, P < .01). The right ventricular weight divided by body weight was significantly greater in the left atrial stenosis group than in the sham-operated control group (0.54 mg/g, IQR, 0.50-0.59 and 0.39 mg/g, IQR, 0.38-0.43, P < .01). Histologic examination revealed medial hypertrophy of the pulmonary vein was thickened by 1.6 times in the left atrial stenosis group compared with the sham-operated control group. DNA microarray analysis and real-time polymerase chain reaction revealed that transforming growth factor-β mRNA was significantly elevated in the left atrial stenosis group. The protein levels of transforming growth factor-β and endothelin-1 were increased in the lung of the left atrial stenosis group by Western blot analyses.

CONCLUSIONS

We successfully established a novel, feasible rat model of pulmonary hypertension due to left heart diseases by generating left atrial stenosis. Although pulmonary hypertension was moderate, the pulmonary hypertension due to left heart diseases model rats demonstrated characteristic intrapulmonary venous arterialization and should be used to further investigate the mechanism of pulmonary hypertension due to left heart diseases.

Pulmonary hemodynamics and effects of phosphodiesterase type 5 inhibition in heart failure: a meta-analysis of randomized trials

Background

Previous studies suggested that phosphodiesterase 5 inhibitors (PDE5i) have a beneficial effect in patients with heart failure (HF), although the results were inconsistent. We performed a meta-analysis to evaluate the effect of PDE5i in HF patients, and investigated the relationship between PDE5i effects and pulmonary hemodynamics.

Method

We searched PubMed, EMBASE and the Cochrane Library for randomized controlled trials (RCTs) that compared PDE5i with placebo in HF with reduced ejection fraction (HFrEF) or HF with preserved EF (HFpEF). PDE5i effects were interpolated according to baseline pulmonary arterial pressure (PAP) or according to changes in PAP after PDE5i treatment.

Results

Thirteen RCTs enrolling 898 HF patients, and two sub-analysis studies with different study outcomes, were included in the meta-analysis. Among patients with HFrEF, PDE5i improved peak VO₂ (mean difference [MD], 3.76 mL/min/kg; 95% confidence interval [CI], 3.27 to 4.25; P < 0.00001), VE/VCO₂ slope (MD, −6.04; 95% CI, −7.45 to −4.64; P < 0.00001), LVEF (MD, 4.30%; 95% CI, 2.18 to 6.42; P < 0.0001), and pulmonary vascular resistance (MD, −80.74 dyn·sec/cm⁵; 95% CI, −110.69 to −50.79; P < 0.00001). The effects of PDE5i in patients with HFpEF were heterogeneous. Meta-regression analyses indicated that the beneficial effect of PDE5i was related to the baseline PAP as well as the extent of PDE5i-mediated PAP decrease.

Conclusion

PDE5i improved pulmonary hemodynamics and exercise capacity in patients with HFrEF, but not in HFpEF. The relationship between the benefits by PDE5i with the baseline PAP and the changes in PAP indicates the therapeutic potential of PDE5i in HF according to pulmonary hemodynamics.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-017-0576-4) contains supplementary material, which is available to authorized users.