Right ventricular dysfunction in systemic sclerosis-associated pulmonary arterial hypertension

World Health Organization Group I Pulmonary Hypertension: Epidemiology and Pathophysiology

Pulmonary arterial hypertension (PAH) is a debilitating disease characterized by pathologic remodeling of the resistance pulmonary arteries, ultimately leading to right ventricular (RV) failure and death. In this article we discuss the definition of PAH, the initial epidemiology based on the National Institutes of Health Registry, and the updated epidemiology gleaned from contemporary registries, pathogenesis of pulmonary vascular dysfunction and proliferation, and RV failure in PAH.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

Idiopathic and Systemic Sclerosis-Associated Pulmonary Arterial Hypertension: A Comparison of Demographic, Hemodynamic, and MRI Characteristics and Outcomes

BACKGROUND

Previous studies have identified survival in systemic sclerosis (SSc)-associated pulmonary arterial hypertension (SSc-PAH) as being worse than in idiopathic pulmonary arterial hypertension (IPAH). We investigated differences between these conditions by comparing demographic, hemodynamic, and radiological characteristics and outcomes in a large cohort of incident patients.

METHODS

Six hundred fifty-one patients diagnosed with IPAH or SSc-associated precapillary pulmonary hypertension were included. Patients with pulmonary disease or two or more risk factors for left heart disease were identified, leaving a primary analysis set of 375 subjects. Subgroup analysis using cardiac magnetic resonance (CMR) imaging was performed.

RESULTS

Median survival was 7.8 years in IPAH and 3 years in SSc-PAH (P < .001). Patients with SSc-PAH were older with less severe hemodynamics but lower gas transfer (diffusing capacity for carbon monoxide [Dlco]). Independent prognostic factors were age, SSc, Dlco, pulmonary artery saturation, and stroke volume. After excluding patients with normal or only mildly elevated resistance, there was no difference in the relationship between pulmonary vascular resistance (PVR) and compliance in IPAH and SSc-PAH. The relationship between mean pulmonary arterial pressure (mPAP) and systolic pulmonary arterial pressure (sPAP) in IPAH was identical to that previously reported (mPAP = 0.61 sPAP + 2 mm Hg). The relationship in SSc-PAH was similar: mPAP = 0.58 sPAP + 2 mm Hg (P value for difference with IPAH = 0.095). The correlation between ventricular mass index assessed at CMR imaging and PVR was stronger in SSc-PAH.

CONCLUSIONS

The reasons for poorer outcomes in SSc-PAH are likely to be multifactorial, including but not limited to older age and reduced gas transfer.

Heart Rate Dependence of the Pulmonary Resistance x Compliance (RC) Time and Impact on Right Ventricular Load

Background

The effect of heart rate (HR) and body surface area (BSA) on pulmonary RC time and right ventricular (RV) load is unknown.

Methods

To determine the association of HR and BSA with the pulmonary RC time and measures of RV load, we studied three large patient cohorts including subjects with 1) known or suspected pulmonary arterial hypertension (PAH) (n = 1008), 2) pulmonary hypertension due to left heart disease (n = 468), and 3) end-stage heart failure with reduced ejection fraction (n = 150). To corroborate these associations on an individual patient level, we performed an additional analysis using high-fidelity catheters in 22 patients with PAH undergoing right atrial pacing.

Results

A faster HR inversely correlated with RC time (p<0.01 for all), suggesting augmented RV pulsatile loading. Lower BSA directly correlated with RC time (p<0.05) although the magnitude of this effect was smaller than for HR. With incremental atrial pacing, cardiac output increased and total pulmonary resistance (TPR) fell. However, effective arterial elastance, its mean resistive component (TPR/heart period; 0.60±0.27 vs. 0.79±0.45;p = 0.048), and its pulsatile component (0.27±0.18 vs 0.39±0.28;p = 0.03) all increased at faster HR.

Conclusion

Heart rate and BSA are associated with pulmonary RC time. As heart rate increases, the pulsatile and total load on the RV also increase. This relationship supports a hemodynamic mechanism for adverse effects of tachycardia on the RV.

Right Ventricular Functional Reserve in Pulmonary Arterial Hypertension

BACKGROUND

Right ventricular (RV) functional reserve affects functional capacity and prognosis in patients with pulmonary arterial hypertension (PAH). PAH associated with systemic sclerosis (SSc-PAH) has a substantially worse prognosis than idiopathic PAH (IPAH), even though many measures of resting RV function and pulmonary vascular load are similar. We therefore tested the hypothesis that RV functional reserve is depressed in SSc-PAH patients.

METHODS AND RESULTS

RV pressure-volume relations were prospectively measured in IPAH (n=9) and SSc-PAH (n=15) patients at rest and during incremental atrial pacing or supine bicycle ergometry. Systolic and lusitropic function increased at faster heart rates in IPAH patients, but were markedly blunted in SSc-PAH. The recirculation fraction, which indexes intracellular calcium recycling, was also depressed in SSc-PAH (0.32±0.05 versus 0.50±0.05; P=0.039). At matched exercise (25 W), SSc-PAH patients did not augment contractility (end-systolic elastance) whereas IPAH did (P<0.001). RV afterload assessed by effective arterial elastance rose similarly in both groups; thus, ventricular-vascular coupling declined in SSc-PAH. Both end-systolic and end-diastolic RV volumes increased in SSc-PAH patients to offset contractile deficits, whereas chamber dilation was absent in IPAH (+37±10% versus +1±8%, P=0.004, and +19±4% versus -1±6%, P<0.001, respectively). Exercise-associated RV dilation also strongly correlated with resting ventricular-vascular coupling in a larger cohort.

CONCLUSIONS

RV contractile reserve is depressed in SSc-PAH versus IPAH subjects, associated with reduced calcium recycling. During exercise, this results in ventricular-pulmonary vascular uncoupling and acute RV dilation. RV dilation during exercise can predict adverse ventricular-vascular coupling in PAH patients.

Unique Abnormalities in Right Ventricular Longitudinal Strain in Systemic Sclerosis Patients

BACKGROUND

Cardiac involvement in systemic sclerosis (scleroderma [SSc]) adversely affects long-term prognosis, often remaining undetectable despite close clinical examination and 2-dimensional echocardiographic monitoring. Speckle-derived strain of the right ventricle (RV) was utilized to detect occult abnormalities in regional and global contractility in SSc patients.

METHODS AND RESULTS

A total of 138 SSc patients with technically adequate echocardiograms was studied and compared with 40 age- and sex-matched healthy non-SSc controls. Standard assessment of RV chamber function included tricuspid annular plane systolic excursion and fractional area change. RV longitudinal systolic speckle-derived strain was assessed in the basal, mid, and apical free wall. Tricuspid annular plane systolic excursion was not different between groups (P=0.307). Although fractional area change was lower in SSc patients than in controls (mean, 48.9 versus 55; P=0.002), the mean fractional area change was still within the normal range (>35). In contrast, RV longitudinal systolic speckle-derived strain measures were significantly different between groups, both globally (-20.4% versus -17.7%; P=0.005) and regionally: they were decreased in the apex (-8.5% versus -17.1%; P<0.0001) and mid segments (-12.4% versus -20.9%; P<0.0001), and increased in the base (-32.2% versus -23.3%; P=0.0001) for the SSc group. The regional difference in the base compared with the apex was significantly greater for SSc than for controls (P<0.0001 for interaction). The differences observed in regional strain between SSc and control were unchanged after adjusting for RV systolic pressure.

CONCLUSIONS

Speckle-derived strain reveals a heterogenous pattern of regional heart strain in SSc that is not detected by conventional measures of function, suggestive of occult RV myocardial disease.

Imaging right ventricular function to predict outcome in pulmonary arterial hypertension

BACKGROUND

Right ventricular (RV) function is a major determinant of outcome in pulmonary arterial hypertension (PAH). However, uncertainty persists about the optimal method of evaluation.

METHODS

We measured RV end-systolic and end-diastolic volumes (ESV and EDV) using cardiac magnetic resonance imaging and RV pressures during right heart catheterization in 140 incident PAH patients and 22 controls. A maximum RV pressure (Pmax) was calculated from the nonlinear extrapolations of early and late systolic portions of the RV pressure curve. The gold standard measure of RV function adaptation to afterload, or RV-arterial coupling (Ees/Ea) was estimated by the stroke volume (SV)/ESV ratio (volume method) or as Pmax/mean pulmonary artery pressure (mPAP) minus 1 (pressure method) (n=84). RV function was also assessed by ejection fraction (EF), right atrial pressure (RAP) and SV.

RESULTS

Higher Ea and RAP, and lower compliance, SV and EF predicted outcome at univariate analysis. Ees/Ea estimated by the pressure method did not predict outcome but Ees/Ea estimated by the volume method (SV/ESV) did. At multivariate analysis, only SV/ESV and EF were independent predictors of outcome. Survival was poorer in patients with a fall in EF or SV/ESV during follow-up (n=44, p=0.008).

CONCLUSION

RV function to predict outcome in PAH is best evaluated by imaging derived SV/ESV or EF. In this study, there was no added value of invasive measurements or simplified pressure-derived estimates of RV-arterial coupling.

The right ventricle and pulmonary hypertension

In patients with pulmonary hypertension (PH), the primary cause of death is right ventricular (RV) failure. Improvement in RV function is therefore one of the most important treatment goals. In order to be able to reverse RV dysfunction and also prevent RV failure, a detailed understanding of the pathobiology of RV failure and the underlying mechanisms concerning the transition from a pressure-overloaded adapted right ventricle to a dilated and failing right ventricle is required. Here, we propose that insufficient RV contractility, myocardial fibrosis, capillary rarefaction, and a disturbed metabolism are important features of a failing right ventricle. Furthermore, an overview is provided about the potential direct RV effects of PH-targeted therapies and the effects of RV-directed medical treatments.

Diagnosing and treating the failing right heart

PURPOSE OF REVIEW

Right ventricular failure (RVF) is associated with significant morbidity and mortality. There is an increasing interest in proper assessment of right ventricle (RV) function as well as understanding mechanisms behind RVF.

RECENT FINDINGS

Within this article, we discuss the metabolic changes that occur in the RV in response to RVF, in particular, a shift toward glycolysis and increased glutaminolysis. We will detail the advances made in noninvasive imaging in assessing the function of the RV and review the methods to assess right ventricle-pulmonary artery coupling. We lastly investigate the role of new treatment options in the failing RV, such as β-blocker therapy.

SUMMARY

RVF is a complicated entity. Although some inferences on RV function and treatment can be made from our understanding of the left ventricle, the RV has unique features, anatomically, metabolically and embryologically, that require dedicated RV-directed research.

RV diastolic dysfunction: time to re-evaluate its importance in heart failure

Right ventricular (RV) diastolic dysfunction was first reported as an indicator for the assessment of ventricular dysfunction in heart failure a little over two decades ago. However, the underlying mechanisms and precise role of RV diastolic dysfunction in heart failure remain poorly described. Complexities in the structure and function of the RV make the detailed assessment of the contractile performance challenging when compared to its left ventricular (LV) counterpart. LV dysfunction is known to directly affect patient outcome in heart failure. As such, the focus has therefore been on LV function. Nevertheless, a strategy for the diagnosis and assessment of RV diastolic dysfunction has not been established. Here, we review the different causal mechanisms underlying RV diastolic dysfunction, summarising the current assessment techniques used in a clinical environment. Finally, we explore the role of load-independent indices of RV contractility, derived from the conductance technique, to fully interrogate the RV and expand our knowledge and understanding of RV diastolic dysfunction. Accurate assessment of RV contractility may yield further important prognostic information that will benefit patients with diastolic heart failure.

Adverse Events in Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

OBJECTIVE

Patients with connective tissue disease (CTD)-associated pulmonary arterial hypertension (PAH) have a poorer prognosis compared to those with idiopathic PAH, but little is known about the differences in treatment-related adverse events (AEs) and serious adverse events (SAEs) between these groups. This study was undertaken to characterize these differences.

METHODS

Individual patient-level data from 10 randomized controlled trials of therapies for PAH were obtained from the US Food and Drug Administration. Patients diagnosed as having either CTD-associated PAH or idiopathic PAH were included. A treatment-by-diagnosis interaction term was used to examine whether the effect of treatment on occurrence of AEs differed between patients with CTD-associated PAH and those with idiopathic PAH. Studies were pooled using fixed-effect models.

RESULTS

The study sample included 2,370 participants: 716 with CTD-associated PAH and 1,654 with idiopathic PAH. In the active treatment group compared to the placebo group, the risk of AEs was higher among patients with CTD-associated PAH than among those with idiopathic PAH (odds ratio [OR] 1.57, 95% confidence interval [95% CI] 1.00-2.47 versus OR 0.94, 95% CI 0.69-1.26; P for interaction = 0.061), but there was no difference in the risk of SAEs in analyses adjusted for age, race, sex, hemodynamic findings, and laboratory values. Despite the higher occurrence of AEs in patients with CTD-associated PAH assigned to active therapy compared to those receiving placebo, the risk of drug discontinuation due to an AE was similar to that in patients with idiopathic PAH assigned to active therapy (P for interaction = 0.27).

CONCLUSION

Patients with CTD-associated PAH experienced more treatment-related AEs compared to those with idiopathic PAH in therapeutic clinical trials. These findings suggest that the overall benefit of advanced therapies for PAH may be attenuated by the greater frequency of AEs.

Pulmonary vascular resistance and compliance relationship in pulmonary hypertension

Right ventricular adaptation to the increased pulmonary arterial load is a key determinant of outcomes in pulmonary hypertension (PH). Pulmonary vascular resistance (PVR) and total arterial compliance (C) quantify resistive and elastic properties of pulmonary arteries that modulate the steady and pulsatile components of pulmonary arterial load, respectively. PVR is commonly calculated as transpulmonary pressure gradient over pulmonary flow and total arterial compliance as stroke volume over pulmonary arterial pulse pressure (SV/PApp). Assuming that there is an inverse, hyperbolic relationship between PVR and C, recent studies have popularised the concept that their product (RC-time of the pulmonary circulation, in seconds) is "constant" in health and diseases. However, emerging evidence suggests that this concept should be challenged, with shortened RC-times documented in post-capillary PH and normotensive subjects. Furthermore, reported RC-times in the literature have consistently demonstrated significant scatter around the mean. In precapillary PH, the true PVR can be overestimated if one uses the standard PVR equation because the zero-flow pressure may be significantly higher than pulmonary arterial wedge pressure. Furthermore, SV/PApp may also overestimate true C. Further studies are needed to clarify some of the inconsistencies of pulmonary RC-time, as this has major implications for our understanding of the arterial load in diseases of the pulmonary circulation.

Management of pulmonary hypertension due to heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is a major cause of HF-related morbidity and mortality, with no medical therapy proven to modify the underlying disease process and result in improvements in survival. With long-standing pulmonary venous congestion, a majority of HFpEF patients develop pulmonary hypertension (PH). Elevated pulmonary pressures have been shown to be a major determinant of mortality in this population. Given the paucity of available disease-modifying therapies for HFpEF, there has been a considerable interest in evaluating new therapeutic options specifically targeting PH in this patient population.

Right ventricular remodeling in idiopathic and scleroderma-associated pulmonary arterial hypertension: two distinct phenotypes

Patients with scleroderma (SSc)-associated pulmonary arterial hypertension (PAH) have worse survival than patients with idiopathic PAH (IPAH). We hypothesized that the right ventricle (RV) adapts differently in SSc-PAH versus IPAH. We used cardiac magnetic resonance imaging (cMRI) and hemodynamic characteristics to assess the relationship between RV morphology and RV load in patients with SSc-PAH and IPAH. In 53 patients with PAH (35 with SSc-PAH and 18 with IPAH) diagnosed by right heart catheterization (RHC), we examined cMRIs obtained within 48 hours of RHC and compared RV morphology between groups. Regression analysis was used to assess the association between diagnosis (IPAH vs. SSc-PAH) and RV measurements after adjusting for age, sex, race, body mass index (BMI), left ventricular (LV) mass, and RV load. There were no significant differences in unadjusted comparisons of cMRI measurements between the two groups. Univariable regression showed RV mass index (RVMI) was linearly associated with measures of RV load in both the overall cohort and within each group. Multivariable linear regression models revealed a significant interaction between disease type and RVMI adjusting for pulmonary vascular resistance (PVR), age, sex, race, BMI, and LV mass. This model showed a decreased slope in the relationship between RVMI and PVR in the SSc-PAH group compared with the IPAH group. RVMI varies linearly with measures of RV load. After adjusting for multiple potential confounders, patients with SSc-PAH demonstrated significantly less RV hypertrophy with increasing PVR than patients with IPAH. This difference in adaptive hypertrophy may in part explain previously observed decreased contractility and poorer survival in SSc-PAH.

Recent advances in scleroderma-associated pulmonary hypertension

PURPOSE OF REVIEW

This review summarizes recent advances in pulmonary hypertension, a leading cause of morbidity and mortality in scleroderma (SSc).

RECENT FINDINGS

Although WHO Group I pulmonary arterial hypertension (PAH) is the most common cause of pulmonary hypertension, all WHO Groups can occur. PAH is now a criterion for the diagnosis of SSc. Results of recent research have resulted in greater insight into the epidemiology of SSc-pulmonary hypertension with regard to prevalence, incidence and clinical risk factors. There is also greater understanding of the role of inflammation in the pathogenesis of SSc-PAH. Advances have also been made in the evaluation and screening of patients with SSc-PAH, and early detection has been shown to improve survival in a disease that typically has worse outcomes than other forms of PAH. Finally, recommendations have been made with regard to goal-directed therapy.

SUMMARY

Although there have been many recent advances in SSc-pulmonary hypertension, further research is needed in order to prevent/cure this deadly complication.

The right ventricle in scleroderma (2013 Grover Conference Series)

Pulmonary arterial hypertension (PAH) results from severe remodeling of the distal lung vessels leading irremediably to death through right ventricular (RV) failure. PAH (Group 1 of the World Health Organization classification of pulmonary hypertension) can be idiopathic (IPAH) or associated with other disorders, such as connective tissue diseases. Prominent among the latter is systemic sclerosis (SSc), a heterogeneous disorder characterized by endothelium dysfunction, dysregulation of fibroblasts resulting in excessive collagen production, and immune abnormalities. For as-yet-unknown reasons, SSc-associated PAH (SSc-PAH) carries a significantly worse prognosis compared with any other form of PAH in Group 1, including IPAH. We have previously shown that patients with SSc-PAH have a median survival of only 3 years, compared with 8 years for IPAH, despite modern PAH therapy. Because death is principally due to RV failure, we speculated that RV adaptation to PAH differed between the two entities due to disparate pulmonary artery loading, perhaps from vessel stiffening, or intrinsic RV myocardial disease that might limit function and adaptation to high afterload. In SSc, RV function may also be impaired by inflammatory processes, excess fibrosis of the myocardium, or altered angiogenesis, which may all contribute to impaired contractile reserve exacerbating cardiopulmonary impedance mismatch. This is now suggested by recent findings from our group that demonstrate that, although pulmonary vascular load may be similar between patients with IPAH and those with SSc-PAH, the latter display reduced myocardial contractility as assessed by pressure-volume loop measurements. This review focuses on fundamental hemodynamic, structural, and functional differences in RV from patients with SSc-PAH compared with IPAH, which may account for survival discrepancies between the two populations. Possible underlying basic mechanisms are discussed.

Clinical relevance of right ventricular diastolic stiffness in pulmonary hypertension

Right ventricular (RV) diastolic stiffness is increased in pulmonary arterial hypertension (PAH) patients. We investigated whether RV diastolic stiffness is associated with clinical progression and assessed the contribution of RV wall thickness to RV systolic and diastolic stiffness.

Using single-beat pressure–volume analyses, we determined RV end-systolic elastance (Ees), arterial elastance (Ea), RV­–arterial coupling (Ees/Ea), and RV end-diastolic elastance (stiffness, Eed) in controls (n=15), baseline PAH patients (n=63) and treated PAH patients (survival >5 years n=22 and survival <5 years n=23).

We observed an association between Eed and clinical progression, with baseline Eed >0.53 mmHg·mL-1 associated with worse prognosis (age-corrected hazard ratio 0.27, p=0.02). In treated patients, Eed was higher in patients with survival <5 years than in patients with survival >5 years (0.91±0.50 versus 0.53±0.33 mmHg·mL-1, p<0.01). Wall-thickness-corrected Eed values in PAH patients with survival >5 years were not different from control values (0.76±0.47 versus 0.60±0.41 mmHg·mL-1, respectively, not significant), whereas in patients with survival <5 years, values were significantly higher (1.52±0.91 mmHg·mL-1, p<0.05 versus controls).

RV diastolic stiffness is related to clinical progression in both baseline and treated PAH patients. RV diastolic stiffness is explained by the increased wall thickness in patients with >5 years survival, but not in those surviving <5 years. This suggests that intrinsic myocardial changes play a distinctive role in explaining RV diastolic stiffness at different stages of PAH.

Effect of acute arteriolar vasodilation on capacitance and resistance in pulmonary arterial hypertension

BACKGROUND

Pulmonary vascular capacitance (PVC) is reduced in pulmonary arterial hypertension (PAH). In normal lung, PVC is largely a function of vascular compliance. In PAH, increased pulmonary vascular resistance (PVR) arises from the arterioles. PVR and PVC share pressure and volume variables. The dependency between the two qualities of the vascular bed is unclear in a state of intense vasoconstriction.

METHODS

We compared PVC and PVR before and during nitric oxide (NO) inhalation during right-sided heart catheterization in eight NO-responsive patients with PAH. NO only directly affects tone in parenchymal vessels.

RESULTS

During NO inhalation, pulmonary arterial systolic pressure decreased, 80 ± 20 SD to 48 ± 20 mm Hg, and stroke volume increased, 62 ± 19 mL to 86 ± 24 mL (P < .01). PVR dropped from 10 ± 4.4 Wood units to 4.7 ± 2.2 Wood units (P < .012), and PVC increased from 1.4 ± 1.1 mL/mm Hg to 3.2 ± 1.8 mL/mm Hg (P < .018). The magnitude of PVR drop was 57% ± 6% and the decrease in 1/PVC was 54% ± 14% (P = not significant).

CONCLUSIONS

In vasoresponsive PAH, PVC is a function of the pressure response of the vasoconstricted arterioles to stroke volume. Immediately upon vasodilation, the capacitance increases markedly. The compliance vessels are, thus, the same as the resistance vessels. The immediate reduction in pulmonary arterial pressure during NO inhalation suggests that large vessel remodeling is not a major contributor to systolic pressure in these patients.

Three-dimensional echocardiography and 2D-3D speckle-tracking imaging in chronic pulmonary hypertension: diagnostic accuracy in detecting hemodynamic signs of right ventricular (RV) failure

BACKGROUND

Our aim was to compare three-dimensional (3D) and 2D and 3D speckle-tracking (2D-STE, 3D-STE) echocardiographic parameters with conventional right ventricular (RV) indexes in patients with chronic pulmonary hypertension (PH), and investigate whether these techniques could result in better correlation with hemodynamic variables indicative of heart failure.

METHODS AND RESULTS

Seventy-three adult patients (mean age, 53±13 years; 44% male) with chronic PH of different etiologies were studied by echocardiography and cardiac catheterization (25 precapillary PH from pulmonary arterial hypertension, 23 obstructive pulmonary heart disease, and 23 postcapillary PH from mitral regurgitation). Thirty healthy subjects (mean age, 54±15 years; 43% male) served as controls. Standard 2D measurements (RV-fractional area change-tricuspid annular plane systolic excursion) and mitral and tricuspid tissue Doppler annular velocities were obtained. RV 3D volumes and global and regional ejection fraction (3D-RVEF) were determined. RV strains were calculated by 2D-STE and 3D-STE. RV 3D global-free-wall longitudinal strain (3DGFW-RVLS), 2D global-free-wall longitudinal strain (GFW-RVLS), apical-free-wall longitudinal strain, basal-free-wall longitudinal strain, and 3D-RVEF were lower in patients with precapillary PH (P<0.0001) and postcapillary PH (P<0.01) compared to controls. 3DGFW-RVLS (hazard ratio 4.6, 95% CI 2.79 to 8.38, P=0.004) and 3D-RVEF (hazard ratio 5.3, 95% CI 2.85 to 9.89, P=0.002) were independent predictors of mortality. Receiver operating characteristic curves showed that the thresholds offering an adequate compromise between sensitivity and specificity for detecting hemodynamic signs of RV failure were 39% for 3D-RVEF (AUC 0.89), -17% for 3DGFW-RVLS (AUC 0.88), -18% for GFW-RVLS (AUC 0.88), -16% for apical-free-wall longitudinal strain (AUC 0.85), 16 mm for tricuspid annular plane systolic excursion (AUC 0.67), and 38% for RV-FAC (AUC 0.62).

CONCLUSIONS

In chronic PH, 3D, 2D-STE and 3D-STE parameters indicate global and regional RV dysfunction that is associated with RV failure hemodynamics better than conventional echo indices.

Right ventricle in acute and chronic pulmonary embolism (2013 Grover Conference series)

Venous thromboembolism (VTE) encompasses deep-vein thrombosis and pulmonary embolism (PE). It is the third-most-frequent cardiovascular disease, with an overall annual incidence of 1-2 per 1,000 population. Chronic thromboembolic pulmonary hypertension (CTEPH) is regarded as a late sequela of PE, with a reported incidence varying between 0.1% and 9.1% of those surviving acute VTE. Right ventricular (RV) function is dependent on afterload. The most precise technique to describe RV function is invasive assessment of the RV-to-pulmonary vascular coupling. However, assessments of RV afterload (i.e., steady and pulsatile flow components and their product, the RC-time) may be useful hemodynamic surrogates of coupling. RV load is different in acute and chronic PE. In acute PE, more than 60% occlusion of the cross-sectional area of the pulmonary artery within a short period of time leads to abrupt hemodynamic collapse. If the time of occlusion is limited to ∼15 seconds, significant decreases in fractional area change, tricuspid annulus systolic excursion, and RV free-wall deformation (strain) occur, with the latter showing significant postsystolic shortening. These changes have similarities to ischemic stunning, and they recover within minutes. In CTEPH, studies of pulmonary vascular resistance (PVR) and pulmonary arterial compliance demonstrated low RC-times that were further lowered after pulmonary endarterectomy (PEA). Immediate postoperative PVR was the only predictor of long-term survival/freedom from lung transplantation, suggesting that the effect of PEA on opening vascular territories to flow outweighs its effect on proximal stiffness. This review summarizes the current knowledge on vascular and intrinsic RV adaptation to VTE, including CTEPH, and the role of imaging.

Biomechanics of the right ventricle in health and disease (2013 Grover Conference series)

Right ventricular (RV) function is a major determinant of the symptomatology and outcome in pulmonary hypertension. The normal RV is a thin-walled flow generator able to accommodate large changes in venous return but unable to maintain flow output in the presence of a brisk increase in pulmonary artery pressure. The RV chronically exposed to pulmonary hypertension undergoes hypertrophic changes and an increase in contractility, allowing for preserved flow output in response to peripheral demand. Failure of systolic function adaptation (homeometric adaptation, described by Anrep's law of the heart) results in increased dimensions (heterometric adaptation; Starling's law of the heart), with a negative effect on diastolic ventricular interactions, limitation of exercise capacity, and vascular congestion. Ventricular function is described by pressure-volume relationships. The gold standard of systolic function is maximum elastance (E max), or the maximal value of the ratio of pressure to volume. This value is not immediately sensitive to changes in loading conditions. The gold standard of afterload is arterial elastance (E a), defined by the ratio of pressure at E max to stroke volume. The optimal coupling of ventricular function to the arterial circulation occurs at an E max/E a ratio between 1.5 and 2. Patients with severe pulmonary hypertension present with an increased E max, a trend toward decreased E max/E a, and increased RV dimensions, along with progression of the pulmonary vascular disease, systemic factors, and left ventricular function. The molecular mechanisms of RV systolic failure are currently being investigated. It is important to refer biological findings to sound measurements of function. Surrogates for E max and E a are being developed through bedside imaging techniques.

Connective tissue disease-associated pulmonary arterial hypertension

Although rare in its idiopathic form, pulmonary arterial hypertension (PAH) is not uncommon in association with various associated medical conditions, most notably connective tissue disease (CTD). In particular, it develops in approximately 10% of patients with systemic sclerosis and so these patients are increasingly screened to enable early detection. The response of patients with systemic sclerosis to PAH-specific therapy appears to be worse than in other forms of PAH. Survival in systemic sclerosis-associated PAH is inferior to that observed in idiopathic PAH. Potential reasons for this include differences in age, the nature of the underlying pulmonary vasculopathy and the ability of the right ventricle to cope with increased afterload between patients with systemic sclerosis-associated PAH and idiopathic PAH, while coexisting cardiac and pulmonary disease is common in systemic sclerosis-associated PAH. Other forms of connective tissue-associated PAH have been less well studied, however PAH associated with systemic lupus erythematosus (SLE) has a better prognosis than systemic sclerosis-associated PAH and likely responds to immunosuppression.

RV-pulmonary arterial coupling predicts outcome in patients referred for pulmonary hypertension

OBJECTIVE

Prognosis in pulmonary hypertension (PH) is largely determined by RV function. However, uncertainty remains about what metrics of RV function might be most clinically relevant. The purpose of this study was to assess the clinical relevance of metrics of RV functional adaptation to increased afterload.

METHODS

Patients referred for PH underwent right heart catheterisation and RV volumetric assessment within 48 h. A RV maximum pressure (Pmax) was calculated from the RV pressure curve. The adequacy of RV systolic functional adaptation to increased afterload was estimated either by a stroke volume (SV)/end-systolic volume (ESV) ratio, a Pmax/mean pulmonary artery pressure (mPAP) ratio, or by EF (RVEF). Diastolic function of the RV was estimated by a diastolic elastance coefficient β. Survival analysis was via Cox proportional HR, and Kaplan-Meier with the primary outcome of time to death or lung transplant.

RESULTS

Patients (n=50; age 58±13 yrs) covered a range of mPAP (13-79 mm Hg) with an average RVEF of 39±17% and ESV of 143±89 mL. Average estimates of the ratio of end-systolic ventricular to arterial elastance were 0.79±0.67 (SV/ESV) and 2.3±0.65 (Pmax/mPAP-1). Transplantation-free survival was predicted by right atrial pressure, mPAP, pulmonary vascular resistance, β, SV, ESV, SV/ESV and RVEF, but after controlling for right atrial pressure, mPAP, and SV, SV/ESV was the only independent predictor.

CONCLUSIONS

The adequacy of RV functional adaptation to afterload predicts survival in patients referred for PH. Whether this can simply be evaluated using RV volumetric imaging will require additional confirmation.

The right ventricle in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a right heart failure syndrome. In early-stage PAH, the right ventricle tends to remain adapted to afterload with increased contractility and little or no increase in right heart chamber dimensions. However, less than optimal right ventricular (RV)-arterial coupling may already cause a decreased aerobic exercise capacity by limiting maximum cardiac output. In more advanced stages, RV systolic function cannot remain matched to afterload and dilatation of the right heart chamber progressively develops. In addition, diastolic dysfunction occurs due to myocardial fibrosis and sarcomeric stiffening. All these changes lead to limitation of RV flow output, increased right-sided filling pressures and under-filling of the left ventricle, with eventual decrease in systemic blood pressure and altered systolic ventricular interaction. These pathophysiological changes account for exertional dyspnoea and systemic venous congestion typical of PAH. Complete evaluation of RV failure requires echocardiographic or magnetic resonance imaging, and right heart catheterisation measurements. Treatment of RV failure in PAH relies on: decreasing afterload with drugs targeting pulmonary circulation; fluid management to optimise ventricular diastolic interactions; and inotropic interventions to reverse cardiogenic shock. To date, there has been no report of the efficacy of drug treatments that specifically target the right ventricle.

Structural and mechanical adaptations of right ventricle free wall myocardium to pressure overload

Right ventricular (RV) failure in response to pulmonary hypertension (PH) is a severe disease that remains poorly understood. PH-induced pressure overload leads to changes in the RV free wall (RVFW) that eventually results in RV failure. While the development of computational models can benefit our understanding of the onset and progression of PH-induced pressure overload, detailed knowledge of the underlying structural and biomechanical events remains limited. The goal of the present study was to elucidate the structural and biomechanical adaptations of RV myocardium subjected to sustained pressure overload in a rat model. Hemodynamically confirmed severe chronic RV pressure overload was induced in Sprague-Dawley rats via pulmonary artery banding. Extensive tissue-level biaxial mechanical and histomorphological analyses were conducted to assess the remodeling response in the RV free wall. Simultaneous myofiber hypertrophy and longitudinal re-orientation of myo- and collagen fibers were observed, with both fiber types becoming more highly aligned. Transmural myo- and collagen fiber orientations were co-aligned in both the normal and diseased state. The overall tissue stiffness increased, with larger increases in longitudinal vs. circumferential stiffness. The latter was attributed to longitudinal fiber re-orientation, which increased the degree of anisotropy. Increased mechanical coupling between the two axes was attributed to the increased fiber alignment. Interestingly, estimated myofiber stiffness increased while the collagen fiber stiffness remained unchanged. The increased myofiber stiffness was consistent with clinical results showing titin-associated increased sarcomeric stiffening observed in PH patients. These results further our understanding of the underlying adaptive and maladaptive remodeling mechanisms and may lead to improved techniques for prognosis, diagnosis, and treatment for PH.

Structural and mechanical adaptations of right ventricle free wall myocardium to pressure overload

Right ventricular (RV) failure in response to pulmonary hypertension (PH) is a severe disease that remains poorly understood. PH-induced pressure overload leads to changes in the RV free wall (RVFW) that eventually results in RV failure. While the development of computational models can benefit our understanding of the onset and progression of PH-induced pressure overload, detailed knowledge of the underlying structural and biomechanical events remains limited. The goal of the present study was to elucidate the structural and biomechanical adaptations of RV myocardium subjected to sustained pressure overload in a rat model. Hemodynamically confirmed severe chronic RV pressure overload was induced in Sprague-Dawley rats via pulmonary artery banding. Extensive tissue-level biaxial mechanical and histomorphological analyses were conducted to assess the remodeling response in the RV free wall. Simultaneous myofiber hypertrophy and longitudinal re-orientation of myo- and collagen fibers were observed, with both fiber types becoming more highly aligned. Transmural myo- and collagen fiber orientations were co-aligned in both the normal and diseased state. The overall tissue stiffness increased, with larger increases in longitudinal vs. circumferential stiffness. The latter was attributed to longitudinal fiber re-orientation, which increased the degree of anisotropy. Increased mechanical coupling between the two axes was attributed to the increased fiber alignment. Interestingly, estimated myofiber stiffness increased while the collagen fiber stiffness remained unchanged. The increased myofiber stiffness was consistent with clinical results showing titin-associated increased sarcomeric stiffening observed in PH patients. These results further our understanding of the underlying adaptive and maladaptive remodeling mechanisms and may lead to improved techniques for prognosis, diagnosis, and treatment for PH.

Physiology of the pulmonary circulation and the right heart

The pulmonary circulation is a high-flow and low-pressure circuit. The functional state of the pulmonary circulation is defined by pulmonary vascular pressure-flow relationships conforming to distensible vessel models with a correction for hematocrit. The product of pulmonary arterial compliance and resistance is constant, but with a slight decrease as a result of increased pulsatile hydraulic load in the presence of increased venous pressure or proximal pulmonary arterial obstruction. An increase in left atrial pressure is transmitted upstream with a ratio ≥1 for mean pulmonary artery pressure and ≤1 the diastolic pulmonary pressure. Therefore, the diastolic pressure gradient is more appropriate than the transpulmonary pressure gradient to identify pulmonary vascular disease in left heart conditions. Exercise is associated with a decrease in pulmonary vascular resistance and an increase in pulmonary arterial compliance. Right ventricular function is coupled to the pulmonary circulation with an optimal ratio of end-systolic to arterial elastances of 1.5-2.

Determinants of right ventricular afterload (2013 Grover Conference series)

Right ventricular (RV) afterload consists of both resistive and capacitive (pulsatile) components. Total afterload can be measured directly with pulmonary artery input impedance spectra or estimated, either with lumped-parameter modeling or by pressure-volume analysis. However, the inverse, hyperbolic relationship between resistance and compliance in the lung would suggest that the pulsatile components are a predictable and constant proportion of the resistive load in most situations, meaning that total RV load can be estimated from mean resistive load alone. Exceptions include elevations in left atrial pressures and, to a lesser extent, chronic thromboembolic disease. The pulsatile components may also play a more significant role at normal or near-normal pulmonary artery pressures. Measures of coupling between RV afterload and RV contractility may provide important information not apparent by other clinical and hemodynamic measures. Future research should be aimed at development of noninvasive measures of coupling.

Conductance catheter measurement and effect of different anesthetics in a rat model of postresuscitation myocardial dysfunction

We demonstrate the usefulness of left ventricular pressure-volume (PV) loops generated by the use of conductance catheter measurements and investigate the influence of the type of general anesthesia on postresuscitation myocardial dysfunction in a rat model of cardiac arrest (CA) and subsequent cardiopulmonary resuscitation. A total of 42 Wistar-Han rats were randomized to receive general anesthesia with sevoflurane and resuscitation after CA, general anesthesia with pentobarbital intraperitoneally and resuscitation after CA, or general anesthesia with pentobarbital without CA (sham group). Myocardial function, assessed by analysis of PV loops, was measured continuously and in real-time by using a PV-conductance catheter. Rats were monitored for 3 h after restoration of spontaneous circulation (ROSC). The use of PV-conductance catheters supported objective and reliable evaluation of myocardial function and proved feasible in this rat model of CA. End-diastolic volume increased in rats anesthetized with pentobarbital after ROSC (before CA, 237 ± 45 μL; after ROSC, 402 ± 64 μL). Preloadadjusted maximal power before CA was the same in all groups but decreased in both resuscitated groups. The decrease was less pronounced in rats anesthetized with sevoflurane compared with pentobarbital (11.8 ± 4.9 mW/μL(2) compared with 4.8 ± 1.9 mW/μL(2) at 3 h after ROSC). This finding indicates that the type of general anesthesia influences postresuscitation myocardial dysfunction in this rat model of experimentally induced CA and cardiopulmonary resuscitation. Rats that were anesthetized with sevoflurane exhibited less postresuscitation myocardial dysfunction than did those anesthetized with pentobarbital.

Right heart dysfunction in heart failure with preserved ejection fraction

AIM

Right heart function is not well characterized in patients with heart failure and preserved ejection fraction (HFpEF). The goal of this study was to examine the haemodynamic, clinical, and prognostic correlates of right ventricular dysfunction (RVD) in HFpEF.

METHODS AND RESULTS

Heart failure and preserved ejection fraction patients (n = 96) and controls (n = 46) underwent right heart catheterization, echocardiographic assessment, and follow-up. Right and left heart filling pressures, pulmonary artery (PA) pressures, and right-sided chamber dimensions were higher in HFpEF compared with controls, while left ventricular size and EF were similar. Right ventricular dysfunction (defined by RV fractional area change, FAC <35%) was present in 33% of HFpEF patients and was associated with more severe symptoms and greater comorbidity burden. Right ventricular function was impaired in HFpEF compared with controls using both load-dependent (FAC: 40 ± 10 vs. 53 ± 7%, P < 0.0001) and load-independent indices (FAC adjusted to PA pressure, P = 0.003), with enhanced afterload-sensitivity compared with controls (steeper FAC vs. PA pressure relationship). In addition to haemodynamic load, RVD in HFpEF was associated with male sex, atrial fibrillation, coronary disease, and greater ventricular interdependence. Over a median follow-up of 529 days (IQR: 143-1066), 31% of HFpEF patients died. In Cox analysis, RVD was the strongest predictor of death (HR: 2.4, 95% CI: 1.6-2.6; P < 0.0001).

CONCLUSION

Right heart dysfunction is common in HFpEF and is caused by both RV contractile impairment and afterload mismatch from pulmonary hypertension. Right ventricular dysfunction in HFpEF develops with increasing PA pressures, atrial fibrillation, male sex, and left ventricular dysfunction, and may represent a novel therapeutic target.

Right heart adaptation to pulmonary arterial hypertension: physiology and pathobiology

Survival in patients with pulmonary arterial hypertension (PAH) is closely related to right ventricular (RV) function. Although pulmonary load is an important determinant of RV systolic function in PAH, there remains a significant variability in RV adaptation to pulmonary hypertension. In this report, the authors discuss the emerging concepts of right heart pathobiology in PAH. More specifically, the discussion focuses on the following questions. 1) How is right heart failure syndrome best defined? 2) What are the underlying molecular mechanisms of the failing right ventricle in PAH? 3) How are RV contractility and function and their prognostic implications best assessed? 4) What is the role of targeted RV therapy? Throughout the report, the authors highlight differences between right and left heart failure and outline key areas of future investigation.