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

Progressive right ventricular functional and structural changes in a mouse model of pulmonary arterial hypertension

Right ventricle (RV) dysfunction occurs with progression of pulmonary arterial hypertension (PAH) due to persistently elevated ventricular afterload. A critical knowledge gap is the molecular mechanisms that govern the transition from RV adaptation to RV maladaptation, which leads to failure. Here, we hypothesize that the recently established mouse model of PAH, via hypoxia and SU5416 treatment (HySu), captures that transition from adaptive to maladaptive RV remodeling including impairments in RV function and decreases in the efficiency of RV interactions with the pulmonary vasculature. To test this hypothesis, we exposed C57BL6 male mice to 0 (control), 14, 21, and 28 days of HySu and then obtained synchronized RV pressure and volume measurements in vivo. With increasing HySu exposure duration, arterial afterload increased monotonically, leading to a continuous increase in RV stroke work, RV fibrosis, and RV wall stiffening (P < 0.05). RV contractility increased at 14 days of HySu exposure and then plateaued (P < 0.05). As a result, ventricular–vascular coupling efficiency tended to increase at 14 days and then decrease. Our results suggest that RV remodeling may begin to shift from adaptive to maladaptive with increasing duration of HySu exposure, which would mimic changes in RV function with PAH progression found clinically. However, for the duration of HySu exposure used here, no drop in cardiac output was found. We conclude that the establishment of a mouse model for overt RV failure due to PAH remains an important task.

This article describes the progressive changes in mouse right ventricle (RV) structure and function during the pulmonary arterial hypertension development. The findings may shed light on the transition from adaptive to maladaptive RV remodeling, which eventually leads to failure.

Heart failure with preserved ejection fraction: emerging drug strategies

Approximately half of heart failure patients have a normal ejection fraction, a condition designated as heart failure with preserved ejection fraction (HFpEF). This heart failure subtype disproportionately affects women and the elderly and is commonly associated with other cardiovascular comorbidities, such as hypertension and diabetes. HFpEF is increasing at a steady rate and is predicted to become the leading cause of heart failure within a decade. HFpEF is characterized by impaired diastolic function, thought to be due to concentric remodeling of the heart along with increased stiffness of both the extracellular matrix and myofilaments. In addition, oxidative stress and inflammation are thought to have a role in HFpEF progression, along with endothelial dysfunction and impaired nitric oxide-cyclic guanosine monophosphate-protein kinase G signaling. Surprisingly a number of clinical studies have failed to demonstrate any benefit of drugs effective in heart failure with systolic dysfunction in HFpEF patients. Thus, HFpEF is one of the largest unmet needs in cardiovascular medicine, and there is a substantial need for new therapeutic approaches and strategies that target mechanisms specific for HFpEF. This conclusion is underscored by the recently reported disappointing results of the RELAX trial, which assessed the use of phosphodiesterase-5 inhibitor sildenafil for treating HFpEF. In animal models, endothelial nitric oxide synthase activators and If current inhibitors have shown benefit in improving diastolic function, and there is a rationale for assessing matrix metalloproteinase 9 inhibitors and nitroxyl donors. LCZ696, a combination drug of angiotensin II receptor blocker and neprilysin inhibitor, and the aldosterone receptor antagonist spironolactone are currently in clinical trial for treating HFpEF. Here we present an overview of the etiology and diagnosis of HFpEF that segues into a discussion of new therapeutic approaches emerging from basic research and drugs currently in clinical trial that primarily target diastolic dysfunction or imbalanced ventricular-arterial coupling.

Mechanisms of exercise intolerance in heart failure with preserved ejection fraction

Approximately half of patients with heart failure (HF) have a preserved ejection fraction (HFpEF), and with the changing age and comorbidity characteristics in the adult population, this number is growing rapidly. The defining symptom of HFpEF is exercise intolerance, but the specific mechanisms causing this common symptom remain debated and inadequately understood. Although diastolic dysfunction was previously considered to be the sole contributor to exercise limitation, recent studies have identified the importance of ventricular systolic, chronotropic, vascular, endothelial and peripheral factors that all contribute in a complex and highly integrated fashion to produce the signs and symptoms of HF. This review will explore the mechanisms underlying objective and subjective exercise intolerance in patients with HFpEF.

High prevalence of occult pulmonary venous hypertension revealed by fluid challenge in pulmonary hypertension

BACKGROUND

Determining the cause for pulmonary hypertension is difficult in many patients. Pulmonary arterial hypertension (PAH) is differentiated from pulmonary venous hypertension (PVH) by a wedge pressure (PWP)>15 mm Hg in PVH. Patients undergoing right heart catheterization for evaluation of pulmonary hypertension may be dehydrated and have reduced intravascular volume, potentially leading to a falsely low measurement of PWP and an erroneous diagnosis of PAH. We hypothesized that a fluid challenge during right heart catheterization would identify occult pulmonary venous hypertension (OPVH).

METHODS AND RESULTS

We reviewed the results of patients undergoing fluid challenge in our pulmonary hypertension database from 2004 to 2011. Baseline hemodynamics were obtained and repeated after infusion of 0.5 L of normal saline for 5 to 10 minutes. Patients were categorized as OPVH if PWP increased to >15 mm Hg after fluid challenge. Baseline hemodynamics in 207 patients met criteria for PAH. After fluid challenge, 46 patients (22.2%) developed a PWP>15 mm Hg and were reclassified as OPVH. Patients with OPVH had a greater increase in PWP compared with patients with PAH, P<0.001, and their demographics and comorbid illnesses were similar to patients with PVH. There were no adverse events related to fluid challenge.

CONCLUSIONS

Fluid challenge at the time of right heart catheterization is easily performed, safe, and identifies a large group of patients diagnosed initially with PAH, but for whom OPVH contributes to pulmonary hypertension. These results have implications for therapeutic trials in PAH and support the routine use of fluid challenge during right heart catheterization in patients with risk factors for PVH.

Update on heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFPEF) is the most common form of heart failure (HF) in older adults, and is increasing in prevalence as the population ages. Morbidity and long-term mortality in HFPEF are substantial and can be similar to HF with reduced ejection fraction (HFREF), yet HFPEF therapy remains empirical and treatment guidelines are based primarily on expert consensus. Neurohormonal blockade has revolutionized the management of HFREF, but trials in HFPEF based on this strategy have been disappointing to date. However, many recent studies have increased knowledge about HFPEF. The concept of HFPEF has evolved from a 'cardio-centric' model to a syndrome that may involve multiple cardiovascular and non-cardiovascular mechanisms. Emerging data highlight the importance of non-pharmacological management strategies and assessment of non-cardiovascular comorbidities. Animal models, epidemiological cohorts, and small human studies suggest that oxidative stress and inflammation contribute to HFPEF, potentially leading to development of new therapeutic targets.

Current treatment of heart failure with preserved ejection fraction: should we add life to the remaining years or add years to the remaining life?

According to the ejection fraction, patients with heart failure may be divided into two different groups: heart failure with preserved or reduced ejection fraction. In recent years, accumulating studies showed that increased mortality and morbidity rates of these two groups are nearly equal. More importantly, despite decline in mortality after treatment in regard to current guideline in patients with heart failure with reduced ejection fraction, there are still no trials resulting in improved outcome in patients with heart failure with preserved ejection fraction so far. Thus, novel pathophysiological mechanisms are under development, and other new viewpoints, such as multiple comorbidities resulting in increased non-cardiac deaths in patients with heart failure and preserved ejection fraction, were presented recently. In this review, we will focus on the tested as well as the promising therapeutic options that are currently studied in patients with heart failure with preserved ejection fraction, along with a brief discussion of pathophysiological mechanisms and diagnostic options that are helpful to increase our understanding of novel therapeutic strategies.

Pressure reflection in the pulmonary circulation by echocardiography in patients with left heart disease indicates reactive pulmonary hypertension

OBJECTIVES

The two hemodynamic profiles in left heart disease (LHD) with pulmonary hypertension (PH), passive PH with increased pulmonary venous pressure and reactive PH with increased pulmonary vascular resistance (PVR > 3 Wood units, WU), are difficult to distinguish non-invasively. We hypothesized that echocardiographic signs of pressure reflection (PR) in the pulmonary circulation can be used to diagnose reactive PH.

MATERIAL AND METHODS

The study comprised 122 patients divided into three groups: patients without PH (No PH, n = 61), patients with LHD, PH and normal PVR (passive PH, n = 29) and patients with LHD, PH and increased PVR (reactive PH, n = 32). Echocardiography and right heart catheterization were performed within 24 h. Three parameters were selected related to PR [the acceleration of flow in the right ventricular outflow tract (RVOT), the interval and the augmentation of pressure between peak RVOT flow and peak RV pressure]. Cutoff values aiming at ruling in (high positive likelihood ratio, PLR) and ruling out (low negative likelihood ratio, NLR) increased PVR were determined using receiver operator characteristic (ROC) curves.

RESULTS

The proportions of the patients with PH and PVR > 3 WU were 50% and 29%. Twenty-one percent had both increased pulmonary capillary wedge pressure and PVR. The area under the ROC curve for the PR parameters was 0.82-0.89. The PLR with ruling in cutoff values ranged from 4.7 to 9.4. The NLR with ruling out cutoff values ranged from 0.20 to 0.12.

CONCLUSIONS

Echocardiographic assessment of PR in patients with LHD can be used to identify or exclude reactive PH.

Pathophysiology of cardiorenal syndrome in decompensated heart failure: role of lung-right heart-kidney interaction

Cardiorenal syndrome (CRS) is defined as an interaction of cardiac disease with renal dysfunction that leads to diuretic resistance and renal function worsening, mainly with heart failure (HF) exacerbation. Hemodynamic variables linking heart and kidney are renal blood flow (cardiac output) and perfusion pressure, i.e., the aortic - renal venous pressure gradient. CRS has traditionally been interpreted as related to defective renal perfusion and arterial underfilling and, more recently, to elevation in central venous pressure transmitted back to renal veins. Our suggestion is that in a setting where aortic pressure is generally low, due to heart dysfunction and to vasodrepressive therapy, the elevated central venous pressure (CVP) contributes to lower the renal perfusion pressure below the threshold of kidney autoregulation (≤80mm Hg) and causes renal perfusion to become directly pressure dependent. This condition is associated with high neurohumoral activation and preglomerular vasoconstriction that may preserve pressure, but may decrease filtration fraction and glomerular filtration rate and enhance proximal tubular sodium absorption. Thus, congestion worsens and drives the vicious cycle of further sodium retention and HF exacerbation. Lowering CVP by targeting the lung-right heart interaction that sustains elevated CVP seems to be a more rational approach rather than reducing intravascular volume. This interaction is crucial and consists of a cascade with stepwise development of pulmonary post-capillary hypertension, precapillary arteriolar hypertone, right ventricular overload and enlargement with tricuspid incompetence and interference with left ventricular filling (interdependence). The resultant CVP rise is transmitted to the renal veins, eventually drives CRS and leads to a positive feedback loop evolving towards HF refractoriness.

Discordant Doppler right heart catheterization pulmonary artery systolic pressures: importance of pulmonary capillary wedge pressure

BACKGROUND

Although the echo Doppler (D) estimation of pulmonary artery systolic pressure (PASP) was initially highly correlated with right heart catheterization (RHC), recent D-RHC studies have questioned its accuracy. The aim of this study was to reevaluate this relationship and to determine possible explanations for disparate D-RHC results.

METHODS

We retrospectively identified all patients at one institution who underwent RHC and had an echocardiogram within the prior month. Echocardiographic and catheterization hemodynamic factors were evaluated by regression and Bland-Altman analysis.

RESULTS

Of 69 patients, 52 (75.4%) had estimable D-PASP. D-RHC PASP r = 0.62 and 51.9% had a PASP difference >10 mmHg, comparable to other recent studies. The D-RHC difference correlated with pulmonary capillary wedge pressure (PCWP) (r = -0.60, P < 0.001) and right atrial pressure (r = -0.43, P = 0.002). Multivariate analysis including wedge pressure improved the relation between D and RHC for PASP (r = 0.86). These results were little changed using only the respective RV-RA pressure gradients from D and RHC.

CONCLUSION

Pulmonary capillary wedge pressure appears to be a significant covariate in the correlation between D and RHC PASP.

Right ventricular afterload and the role of nitric oxide metabolism in left-sided heart failure

Awareness has grown in recent years that right ventricular (RV) function is equally important as left ventricular (LV) function in the setting of left-sided heart disease. RV dysfunction can be the consequence of an increased afterload imposed by the failing LV. The concept of "afterload" is physically most correctly described by vascular input impedance. However, for clinical purposes, afterload is most often modeled to consist of 3 components; pulmonary vascular resistance (PVR), pulmonary arterial compliance (PAC), and characteristic impedance. Whereas PVR is historically most described, PAC (which represents the distensibility of the vasculature) has rapidly gained recognition for its prognostic ability in both pulmonary arterial hypertension and left-sided heart disease. Owing to the specific anatomy of the pulmonary circulation, PVR and PAC have an inverse hyperbolic relationship, which position can be shifted by varying wedge pressures. Knowledge of the afterload components helps one to understand how elevated left-sided filling pressures increase pulsatile load on the RV. An increase in resistive load (known as "reactive" or "out-of-proportion" pulmonary hypertension) ultimately complements the increase in pulsatile load. Perturbations in nitric oxide metabolism are thought to be crucial in this evolution and have therefore been sought as a major therapeutic target.

Role of phosphodiesterase-5 inhibitors in heart failure: emerging data and concepts

Novel treatment of congestive heart failure (HF) involves utilizing unique pathways to improve upon contemporary therapies. Increasing the availability of cyclic guanosine monophosphate (cGMP) by inhibition of phosphodiesterase-5 (PDE5) is a relatively new, but promising therapeutic strategy. Preclinical studies suggest a favorable myocardial effect of PDE5 inhibitors by blocking adrenergic, hypertrophic and pro-apoptotic signaling, thereby supporting their use in HF. The clinical benefits of acute and chronic PDE5 inhibition on lung diffusion capacity, exercise performance and ejection fraction in humans are emerging and appear promising. Larger, controlled trials are now on-going to assess the safety, efficacy and tolerability of PDE5 inhibitors on morbidity and mortality in patients with both systolic and diastolic heart failure. If the results of these trials are positive, a new avenue for the treatment of HF will open, which will help curtail the societal effects of this costly and morbid disease.

Pathophysiology-based novel pharmacotherapy for heart failure with preserved ejection fraction

Heart failure has become increasingly prevalent and poses a significant socioeconomic burden in the developed world. Approximately half of heart failure patients have preserved ejection fraction (HFpEF) and experience an increased morbidity and mortality attributed to the lack of effective therapies and to the presence of comorbidities. Suppression of neurohormonal activation by beta-blockers and renin-angiotensin-aldosterone system inhibitors is the cornerstone in the pharmacotherapy of heart failure with reduced ejection fraction (HFrEF). However, these medications are not associated with significant clinical benefit in HFpEF. In this review, we provide an in-depth pathophysiology-based update on novel pharmacotherapies of HFpEF. A deeper insight into the pathophysiologic mechanisms of HFpEF may create opportunities for novel pharmacological interventions.

Riociguat for patients with pulmonary hypertension caused by systolic left ventricular dysfunction: a phase IIb double-blind, randomized, placebo-controlled, dose-ranging hemodynamic study

BACKGROUND

Pulmonary hypertension caused by systolic left ventricular dysfunction is associated with significant morbidity and mortality; however, no treatment is approved for this indication. We hypothesized that riociguat, a novel soluble guanylate cyclase stimulator, would have beneficial hemodynamic effects in patients with pulmonary hypertension caused by systolic left ventricular dysfunction.

METHODS AND RESULTS

Overall, 201 patients with heart failure resulting from pulmonary hypertension caused by systolic left ventricular dysfunction were randomized to double-blind treatment with oral placebo or riociguat (0.5, 1, or 2 mg 3 times daily) for 16 weeks in 4 parallel arms. The primary outcome was the placebo-corrected change from baseline at week 16 in mean pulmonary artery pressure. Although the decrease in mean pulmonary artery pressure in the riociguat 2 mg group (-6.1±1.3 mm Hg; P<0.0001 versus baseline) was not significantly different from placebo (P=0.10), cardiac index (0.4 L·min(-1)·m(-2); 95% confidence interval, 0.2-0.5; P=0.0001) and stroke volume index (5.2 mL·m(-2); 95% confidence interval, 2.0-8.4; P=0.0018) were significantly increased without changes in heart rate or systemic blood pressure compared with placebo. Both pulmonary (-46.6 dynes·s(-1)·cm(-5); 95% confidence interval, -89.4 to -3.8; P=0.03) and systemic vascular resistance (-239.3 dynes·s(-1)·cm(-5); 95% confidence interval, -363.4 to -115.3; P=0.0002) were significantly reduced with riociguat 2 mg. Riociguat reduced the Minnesota Living With Heart Failure score (P=0.0002). Discontinuation of treatment was similar between treatment groups.

CONCLUSIONS

Although the primary end point of the study was not met, riociguat was well tolerated in patients with pulmonary hypertension caused by systolic left ventricular dysfunction and improved cardiac index and pulmonary and systemic vascular resistance.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01065454.

A novel paradigm for heart failure with preserved ejection fraction: comorbidities drive myocardial dysfunction and remodeling through coronary microvascular endothelial inflammation

Over the past decade, myocardial structure, cardiomyocyte function, and intramyocardial signaling were shown to be specifically altered in heart failure with preserved ejection fraction (HFPEF). A new paradigm for HFPEF development is therefore proposed, which identifies a systemic proinflammatory state induced by comorbidities as the cause of myocardial structural and functional alterations. The new paradigm presumes the following sequence of events in HFPEF: 1) a high prevalence of comorbidities such as overweight/obesity, diabetes mellitus, chronic obstructive pulmonary disease, and salt-sensitive hypertension induce a systemic proinflammatory state; 2) a systemic proinflammatory state causes coronary microvascular endothelial inflammation; 3) coronary microvascular endothelial inflammation reduces nitric oxide bioavailability, cyclic guanosine monophosphate content, and protein kinase G (PKG) activity in adjacent cardiomyocytes; 4) low PKG activity favors hypertrophy development and increases resting tension because of hypophosphorylation of titin; and 5) both stiff cardiomyocytes and interstitial fibrosis contribute to high diastolic left ventricular (LV) stiffness and heart failure development. The new HFPEF paradigm shifts emphasis from LV afterload excess to coronary microvascular inflammation. This shift is supported by a favorable Laplace relationship in concentric LV hypertrophy and by all cardiac chambers showing similar remodeling and dysfunction. Myocardial remodeling in HFPEF differs from heart failure with reduced ejection fraction, in which remodeling is driven by loss of cardiomyocytes. The new HFPEF paradigm proposes comorbidities, plasma markers of inflammation, or vascular hyperemic responses to be included in diagnostic algorithms and aims at restoring myocardial PKG activity.

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.

Molecular and cellular basis for diastolic dysfunction

Heart failure with preserved ejection fraction (HFpEF) is highly prevalent and is frequently associated with metabolic risk factors. Patients with HFpEF have only a slightly lower mortality than patients with HF and reduced EF. The pathophysiology of HFpEF is currently incompletely understood, which precludes specific therapy. Both HF phenotypes demonstrate distinct cardiac remodeling processes at the macroscopic, microscopic, and ultrastructural levels. Increased diastolic left-ventricular (LV) stiffness and impaired LV relaxation are important features of HFpEF, which can be explained by changes in the extracellular matrix and the cardiomyocytes. In HFpEF, elevated intrinsic cardiomyocyte stiffness contributes to high diastolic LV stiffness. Posttranslational changes in the sarcomeric protein titin, affecting titin isoform expression and phosphorylation, contribute to elevated cardiomyocyte stiffness. Increased nitrosative/oxidative stress, impaired nitric oxide bioavailability, and down-regulation of myocardial cyclic guanosine monophosphate and protein kinase G signaling could trigger posttranslational modifications of titin, thereby augmenting cardiomyocyte and LV diastolic stiffness.

Management of pulmonary hypertension in left heart disease

Pulmonary hypertension (PH) due to left heart disease is classified as group II according to the Dana Point classification, which includes left ventricular systolic and/or diastolic left heart failure, and left-sided valvular disease. PH due to left heart disease is the most common cause and when present, especially with right ventricular dysfunction, is associated with a worse prognosis. Left heart disease with secondary PH is associated with increased left atrial pressure, which causes a passive increase in pulmonary pressure. Passive PH could be superimposed by an active protective, and in some patients by an ‘out of proportion’, elevated precapillary pulmonary vasoconstriction and vascular remodelling which leads to greater or lesser further increase of the pulmonary artery pressure. In this review, epidemiological and pathophysiologic mechanisms for the development of group II PH are summarized. The conflicting data about the haemodynamic and possible parameters to diagnose passive versus reactive and ‘out of proportion’ PH are presented. The different therapeutic concepts, along with novel treatment strategies, are reviewed in detail and critically discussed regarding their effectiveness and safety.

Prolonged mean VO2 response time in systolic heart failure: an indicator of impaired right ventricular-pulmonary vascular function

BACKGROUND

In patients with left ventricular systolic dysfunction (LVSD), the rate at which oxygen uptake (VO2) increases on initiation of exercise is inadequate to match metabolic demands. To gain mechanistic insights into delayed VO2 kinetics in LVSD, we simultaneously assessed hemodynamic measurements, ventilatory parameters, and peripheral oxygen usage during exercise.

METHODS AND RESULTS

Forty-two patients with symptomatic LVSD (age, 59±2 years [mean±SEM]; LV ejection fraction, 30±1%) and 17 controls (LV ejection fraction, 68±1%) underwent maximum upright cycle ergometry cardiopulmonary exercise testing. Hemodynamic monitoring and first-pass radionuclide ventriculography were performed at rest and during exercise. VO2 kinetics were quantified by mean response time (MRT), which was significantly longer in patients with LVSD compared with controls (64±3 versus 45±5 s; P=0.004). In LVSD patients, MRT was associated with higher biventricular filling pressures and reduced cardiac output during early exercise. LVSD patients with MRT ≥60 s, compared with LVSD subjects with MRT <60 s, demonstrated greater impairment in right ventricular-pulmonary vascular function during exercise as evidenced by lower right ventricular ejection fraction (35±2 versus 45±2%; P=0.03), steeper increment in transpulmonary gradient relative to cardiac output (3.7 versus 2.2 mm Hg/L; P<0.001), and increased ventilatory dead-space fraction (17±1 versus 12±2%; P=0.03). In contrast, MRT was not associated with LV ejection fraction (rest, exercise), PaO2, hemoglobin, or resting pulmonary function test results.

CONCLUSIONS

Delayed oxygen uptake on initiation of exercise (ie, MRT ≥60 s) in LVSD is closely related to impaired right ventricular-pulmonary vascular function and may represent an important surrogate for inability to augment RV performance during physical activity in patients with heart failure.

Effect of phosphodiesterase-5 inhibition on exercise capacity and clinical status in heart failure with preserved ejection fraction: a randomized clinical trial

IMPORTANCE

Studies in experimental and human heart failure suggest that phosphodiesterase-5 inhibitors may enhance cardiovascular function and thus exercise capacity in heart failure with preserved ejection fraction (HFPEF).

OBJECTIVE

To determine the effect of the phosphodiesterase-5 inhibitor sildenafil compared with placebo on exercise capacity and clinical status in HFPEF.

DESIGN

Multicenter, double-blind, placebo-controlled, parallel-group, randomized clinical trial of 216 stable outpatients with HF, ejection fraction ≥50%, elevated N-terminal brain-type natriuretic peptide or elevated invasively measured filling pressures, and reduced exercise capacity. Participants were randomized from October 2008 through February 2012 at 26 centers in North America. Follow-up was through August 30, 2012.

INTERVENTIONS

Sildenafil (n = 113) or placebo (n = 103) administered orally at 20 mg, 3 times daily for 12 weeks, followed by 60 mg, 3 times daily for 12 weeks.

MAIN OUTCOME MEASURES

Primary end point was change in peak oxygen consumption after 24 weeks of therapy. Secondary end points included change in 6-minute walk distance and a hierarchical composite clinical status score (range, 1-n, a higher value indicates better status; expected value with no treatment effect, 95) based on time to death, time to cardiovascular or cardiorenal hospitalization, and change in quality of life for participants without cardiovascular or cardiorenal hospitalization at 24 weeks.

RESULTS

Median age was 69 years, and 48% of patients were women. At baseline, median peak oxygen consumption (11.7 mL/kg/min) and 6-minute walk distance (308 m) were reduced. The median E/e' (16), left atrial volume index (44 mL/m2), and pulmonary artery systolic pressure (41 mm Hg) were consistent with chronically elevated left ventricular filling pressures. At 24 weeks, median (IQR) changes in peak oxygen consumption (mL/kg/min) in patients who received placebo (-0.20 [IQR, -0.70 to 1.00]) or sildenafil (-0.20 [IQR, -1.70 to 1.11]) were not significantly different (P = .90) in analyses in which patients with missing week-24 data were excluded, and in sensitivity analysis based on intention to treat with multiple imputation for missing values (mean between-group difference, 0.01 mL/kg/min, [95% CI, -0.60 to 0.61]). The mean clinical status rank score was not significantly different at 24 weeks between placebo (95.8) and sildenafil (94.2) (P = .85). Changes in 6-minute walk distance at 24 weeks in patients who received placebo (15.0 m [IQR, -26.0 to 45.0]) or sildenafil (5.0 m [IQR, -37.0 to 55.0]; P = .92) were also not significantly different. Adverse events occurred in 78 placebo patients (76%) and 90 sildenafil patients (80%). Serious adverse events occurred in 16 placebo patients (16%) and 25 sildenafil patients (22%).

CONCLUSION AND RELEVANCE

Among patients with HFPEF, phosphodiesterase-5 inhibition with administration of sildenafil for 24 weeks, compared with placebo, did not result in significant improvement in exercise capacity or clinical status.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00763867.

Experimental designs for small randomised clinical trials: an algorithm for choice

Background

Small clinical trials are necessary when there are difficulties in recruiting enough patients for conventional frequentist statistical analyses to provide an appropriate answer. These trials are often necessary for the study of rare diseases as well as specific study populations e.g. children. It has been estimated that there are between 6,000 and 8,000 rare diseases that cover a broad range of diseases and patients. In the European Union these diseases affect up to 30 million people, with about 50% of those affected being children. Therapies for treating these rare diseases need their efficacy and safety evaluated but due to the small number of potential trial participants, a standard randomised controlled trial is often not feasible. There are a number of alternative trial designs to the usual parallel group design, each of which offers specific advantages, but they also have specific limitations. Thus the choice of the most appropriate design is not simple.

Methods

PubMed was searched to identify publications about the characteristics of different trial designs that can be used in randomised, comparative small clinical trials. In addition, the contents tables from 11 journals were hand-searched. An algorithm was developed using decision nodes based on the characteristics of the identified trial designs.

Results

We identified 75 publications that reported the characteristics of 12 randomised, comparative trial designs that can be used in for the evaluation of therapies in orphan diseases. The main characteristics and the advantages and limitations of these designs were summarised and used to develop an algorithm that may be used to help select an appropriate design for a given clinical situation. We used examples from publications of given disease-treatment-outcome situations, in which the investigators had used a particular trial design, to illustrate the use of the algorithm for the identification of possible alternative designs.

Conclusions

The algorithm that we propose could be a useful tool for the choice of an appropriate trial design in the development of orphan drugs for a given disease-treatment-outcome situation.

Increased cardiac myocyte PDE5 levels in human and murine pressure overload hypertrophy contribute to adverse LV remodeling

Background

The intracellular second messenger cGMP protects the heart under pathological conditions. We examined expression of phosphodiesterase 5 (PDE5), an enzyme that hydrolyzes cGMP, in human and mouse hearts subjected to sustained left ventricular (LV) pressure overload. We also determined the role of cardiac myocyte-specific PDE5 expression in adverse LV remodeling in mice after transverse aortic constriction (TAC).

Methodology/Principal Findings

In patients with severe aortic stenosis (AS) undergoing valve replacement, we detected greater myocardial PDE5 expression than in control hearts. We observed robust expression in scattered cardiac myocytes of those AS patients with higher LV filling pressures and BNP serum levels. Following TAC, we detected similar, focal PDE5 expression in cardiac myocytes of C57BL/6NTac mice exhibiting the most pronounced LV remodeling. To examine the effect of cell-specific PDE5 expression, we subjected transgenic mice with cardiac myocyte-specific PDE5 overexpression (PDE5-TG) to TAC. LV hypertrophy and fibrosis were similar as in WT, but PDE5-TG had increased cardiac dimensions, and decreased dP/dt_max and dP/dt_min with prolonged tau (P<0.05 for all). Greater cardiac dysfunction in PDE5-TG was associated with reduced myocardial cGMP and SERCA2 levels, and higher passive force in cardiac myocytes in vitro.

Conclusions/Significance

Myocardial PDE5 expression is increased in the hearts of humans and mice with chronic pressure overload. Increased cardiac myocyte-specific PDE5 expression is a molecular hallmark in hypertrophic hearts with contractile failure, and represents an important therapeutic target.

Relationship of Right- to Left-Sided Ventricular Filling Pressures in Advanced Heart Failure

Background—

Although right atrial pressure (RAP) and pulmonary capillary wedge pressure (PCWP) are correlated in heart failure, in a sizeable minority of patients, the RAP and PCWP are not tightly coupled. The basis of this variability in the RAP/PCWP ratio, and whether it conveys prognostic value, is not known.

Methods and Results—

We analyzed the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness (ESCAPE) trial database. Baseline characteristics, including echocardiographic assessment of right ventricular (RV) structure and function, and invasively measured hemodynamic parameters, were compared among tertiles of the RAP/PCWP ratio. Multivariable Cox proportional hazard models assessed the association of RAP/PCWP ratio with the primary ESCAPE outcome (6-month death or hospitalization [days]) adjusting for systolic blood pressure, blood urea nitrogen, 6-minute walk distance, and PCWP. The RAP/PCWP tertiles were 0.27 to 0.4 (tertile 1); 0.41 to 0.615 (tertile 2), and 0.62 to 1.21 (tertile 3). Increasing RAP/PCWP was associated with increasing median right atrial area (23, 26, 29 cm 2 , respectively; P <0.005), RV area in diastole (21, 27, 27 cm 2 , respectively; P <0.005), and pulmonary vascular resistance (2.4, 2.9, 3.6 woods units, respectively; P =0.003), and lower RV stroke work index (8.6, 8.4, 5.5 g·m/m 2 per beat, respectively; P <0.001). RAP/PCWP ratio was associated with death or hospitalization within 6 months (hazard ratio, 1.16 [1, 1.4]; P <0.05).

Conclusions—

Increased RAP/PCWP ratio was associated with higher pulmonary vascular resistance, reduced RV function (manifest as a larger right atrium and ventricle and lower RV stroke work index), and an increased risk of adverse outcomes in patients with advanced heart failure.

[Heart failure with preserved ejection fraction (diastolic heart failure)]

Diastolic heart failure, which is also called as heart failure with preserved ejection fraction, is a clinical syndrome in which patients have signs and symptoms of heart failure, normal or near normal left ventricular ejection fraction (≥ 50%) and evidence of diastolic dysfunction. Recent epidemiological studies have demonstrated that more than half of all heart failure patients have diastolic heart failure. The syndrome is more common in women than in men and the prevalence increases with age. Patients with diastolic heart failure form a fairly heterogeneous group with complex pathophysiologic mechanisms. The disease is often in association with other comorbidities, such as hypertension, diabetes mellitus or obesity. The diagnosis of diastolic heart failure is best achieved by two-dimensional and Doppler echocardiography, which can detect abnormal myocardial relaxation, decreased compliance and increased filling pressure in the setting of normal left ventricular dimensions and preserved ejection fraction. Unlike heart failure with reduced ejection fraction, there is no such an evidence-based treatment for heart failure with preserved ejection fraction, which would improve clinical outcomes. Thus, pharmacological therapy of diastolic heart failure is based mainly on empiric data, and aims to the normalization of blood pressure, reduction of left ventricular dimensions and increased heart rate, maintenance of normal atrial contraction and treatment of symptoms caused by congestion. Beneficial effects of angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers may be utilized in patients with diastolic dysfunction, especially in those with hypertension. Beta-blockers appear to be useful in lowering heart rate and thereby prolonging left ventricular diastolic filling time, while diuretic therapy is the mainstay of treatment for preventing pulmonary congestion. Nonetheless, treatment of the underlying disease is also an important therapeutic approach. This review summarizes the state of current knowledge with regard to diastolic heart failure.

Frontiers of therapy for patients with heart failure

This review broadly covers advances in heart failure, which is responsible for significant morbidity, mortality, and cost in the United States. It is a heterogeneous condition, and accurate classification helps ensure appropriate application of evidence-based therapies. Hemodynamics are important in acute heart failure syndromes and may help tailor therapy. Neurohormonal modulation forms the cornerstone of chronic systolic heart failure treatment but does not affect outcomes in diastolic heart failure where management goals emphasize optimization of central volume, blood pressure, and atrial rhythm, as well as the treatment of comorbidities. Frontiers of heart failure therapy range from advances in pharmacology (novel inotropic agents and neurohormonal modulators), to cell biology (nucleic acid-based drugs and cell therapy) to biomedical engineering (devices such as ultrafiltration, biventricular pacemakers, implantable cardiac defibrillators, remote monitoring systems, and left ventricular assist devices), and to health systems (risk stratification and integrated care of comorbidities). The ultimate frontier will be to integrate these data effectively to ensure that patients with heart failure consistently receive the best evidenced-based care possible.

Pulmonary hypertension due to left heart disease: updated Recommendations of the Cologne Consensus Conference 2011

The 2009 European Guidelines on Diagnosis and Treatment of Pulmonary Hypertension (PH) have been adopted for Germany. While the guidelines contain detailed recommendations regarding pulmonary arterial hypertension (PAH), they contain only a relatively short paragraph on other, much more frequent forms of PH including PH owing to left heart disease. The guidelines point out that the drugs currently used to treat patients with PAH (prostanoids, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors) have not been sufficiently 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. It that sense, the practical implementation of the European Guidelines in Germany requires the consideration of several specific issues and already existing novel data. This requires a detailed commentary to the guidelines, and in some aspects an update already appears necessary. In June 2010, a Consensus Conference organized by the PH working groups of the German Society of Cardiology (DGK), the German Society of Respiratory Medicine (DGP) and the German Society of Pediatric Cardiology (DGPK) was held in Cologne, Germany. This conference aimed to solve practical and controversial issues surrounding the implementation of the European Guidelines in Germany. To this end, a number of working groups was initiated, one of which was specifically dedicated to PH due to left heart disease. This commentary describes in detail the results and recommendations of the working group which were last updated in October 2011.

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.

The malignant obesity hypoventilation syndrome (MOHS)

We have coined the term 'malignant obesity hypoventilation syndrome' (MOHS) to describe a severe multisystem disease due to the systemic effects of obesity. Patients with this syndrome have severe obesity-related hypoventilation together with systemic hypertension, diabetes and the metabolic syndrome, left ventricular hypertrophy with diastolic dysfunction, pulmonary hypertension and hepatic dysfunction. This syndrome is largely unrecognized as physicians do not make the association between the patients' multiple medical problems and obesity. Because of the delayed diagnosis and progressive morbidities of this condition, all patients with a body mass index of more than 40 kg m(-2) should be screened for MOHS. The management of patients with MOHS includes short-term measures to improve the patients' medical condition and long-term measures to achieve enduring weight loss. Bariatric surgery reverses or improves the multiple metabolic and organ dysfunctions associated with MOHS and should be strongly considered in these patients.

Pathophysiology of systolic and diastolic heart failure

Systolic and diastolic heart failure are the 2 most common clinical subsets of chronic heart failure. Left ventricular "Starling" function is depressed in patients with systolic heart failure. In systolic heart failure, left ventricular mass is increased, which can be measured by transthoracic echocardiography. Cardiac magnetic resonance imaging is a more precise technique to measure left ventricular mass. Neurohormonal activation is a major pathophysiologic mechanism for ventricular remodeling and progression of heart failure in systolic heart failure.