The pressure-overloaded right ventricle in pulmonary hypertension

Atrial Arrhythmias in Patients With Pulmonary Hypertension

TOPIC IMPORTANCE

Atrial arrhythmias (AA) are common in patients with pulmonary hypertension (PH) and contribute to morbidity and mortality. Given the growing PH population, understanding the pathophysiology, clinical impact, and management of AA in PH is important.

REVIEW FINDINGS

AA occurs in PH with a 5-year incidence of 10% to 25%. AA confers a higher morbidity and mortality, and restoration of normal sinus rhythm improves survival and functionality. AA is thought to develop because of structural alterations of the right atrium caused by changes to the right ventricle (RV) due to elevated pulmonary artery pressures. AA can subsequently worsen RV function. Current guidelines do not provide comprehensive recommendations for the management of AA in PH. Robust evidence to favor a specific treatment approach is lacking. Although the role of medical rate or rhythm control, and the use of cardioversion and ablation, can be inferred from other populations, evidence is lacking in the PH population. Much remains to be determined regarding the optimal management strategy. We present here our institutional approach and discuss areas for future research.

SUMMARY

This review highlights the epidemiology and pathophysiology of AA in patients with PH, describes the relationship between AA and RV dysfunction, and discusses current management practices. We outline our institutional approach and offer directions for future investigation.

Right ventricular dysfunction in patients with acute respiratory distress syndrome receiving venovenous extracorporeal membrane oxygenation

Acute respiratory distress syndrome is characterized by non-cardiogenic pulmonary edema, decreased pulmonary compliance, and abnormalities in gas exchange, especially hypoxemia. Patients with acute respiratory distress syndrome (ARDS) who receive support with venovenous (V-V) extracorporeal membrane oxygenation (ECMO) usually have severe lung disease. Many patients with ARDS have associated pulmonary vascular injury which can result in elevated pulmonary vascular resistance and right heart dysfunction. Since V-V ECMO relies upon preserved cardiac function, right heart failure has important implications for patient evaluation, management, and outcomes. Worsening right heart function complicates ARDS and disease processes. Given the increasing use of ECMO to support patients with ARDS, an understanding of right ventricular-ECMO and cardiopulmonary interactions is essential for the clinician. A narrative review of the manifestations of right heart dysfunction, as well as diagnosis and management strategies for the patient with ARDS on ECMO, is provided.

Pulmonary Hypertension, an Echo Assessment: Is it Arterial or Venous?

Introduction

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling, right heart failure, and reduced survival. PH can be PH without left ventricular (LV) dysfunction - pulmonary arterial hypertension (PAH) - (Dana point Class I) and PH with LV dysfunction - pulmonary venous hypertension (PVH) - (Dana point Class II). Whatever the underlying cardiac disease, the presence of PH in patients with heart failure is associated with poor prognosis. Right ventricular dysfunction by ventricular interdependence can cause LV dysfunction.

Objective

We aim to provide a distinction between PAH and PVH by echocardiography.

Methods

Retrospective cross-sectional single-center data of 1075 subjects having PH as defined by echocardiography was collected. These were segregated into mild, moderate, and severe categories. The same cohort of PH subjects was also segregated by E/e' derived pulmonary capillary wedge pressure (PCWP) values. Echocardiographic measurements and effort tolerance in Mets were analyzed. Data for 707 normal subjects were taken from an earlier published study on normative echocardiographic measurements of healthy Indians.

Results

Our findings show that PAH and PVH can be distinguished using PCWP value >15 mmHg obtained by applying Nagueh's formulaon E/e'.

Conclusion

We recommend that PCWP derived from E/e' should be reported with pulmonary artery systolic pressure measurement to distinguish between PAH and PVH.

Increased biventricular hemodynamic forces in precapillary pulmonary hypertension

Precapillary pulmonary hypertension (PHprecap) is a condition with elevated pulmonary vascular pressure and resistance. Patients have a poor prognosis and understanding the underlying pathophysiological mechanisms is crucial to guide and improve treatment. Ventricular hemodynamic forces (HDF) are a potential early marker of cardiac dysfunction, which may improve evaluation of treatment effect. Therefore, we aimed to investigate if HDF differ in patients with PHprecap compared to healthy controls. Patients with PHprecap (n = 20) and age- and sex-matched healthy controls (n = 12) underwent cardiac magnetic resonance imaging including 4D flow. Biventricular HDF were computed in three spatial directions throughout the cardiac cycle using the Navier-Stokes equations. Biventricular HDF (N) indexed to stroke volume (l) were larger in patients than controls in all three directions. Data is presented as median N/l for patients vs controls. In the RV, systolic HDF diaphragm-outflow tract were 2.1 vs 1.4 (p = 0.003), and septum-free wall 0.64 vs 0.42 (p = 0.007). Diastolic RV HDF apex-base were 1.4 vs 0.87 (p < 0.0001), diaphragm-outflow tract 0.80 vs 0.47 (p = 0.005), and septum-free wall 0.60 vs 0.38 (p = 0.003). In the LV, systolic HDF apex-base were 2.1 vs 1.5 (p = 0.005), and lateral wall-septum 1.5 vs 1.2 (p = 0.02). Diastolic LV HDF apex-base were 1.6 vs 1.2 (p = 0.008), and inferior-anterior 0.46 vs 0.24 (p = 0.02). Hemodynamic force analysis conveys information of pathological cardiac pumping mechanisms complementary to more established volumetric and functional parameters in precapillary pulmonary hypertension. The right ventricle compensates for the increased afterload in part by augmenting transverse forces, and left ventricular hemodynamic abnormalities are mainly a result of underfilling rather than intrinsic ventricular dysfunction.

Prehospital Ultrasound Diagnosis of Massive Pulmonary Embolism by Non-Physicians: A Case Series

Massive pulmonary embolism (hemodynamically unstable, defined as systolic BP <90 mmHg) has significant morbidity and mortality. Point of care ultrasound (POCUS) has allowed clinicians to detect evidence of massive pulmonary embolism much earlier in the patient's clinical course, especially when patient instability precludes computerized tomography confirmation. POCUS detection of massive pulmonary embolism has traditionally been performed by physicians. This case series demonstrates four cases of massive pulmonary embolism diagnosed with POCUS performed by non-physician prehospital personnel.

Management of High-Risk Pulmonary Embolism: What Is the Place of Extracorporeal Membrane Oxygenation?

Pulmonary embolism (PE) is a common disease with an annual incidence rate ranging from 39-115 per 100,000 inhabitants. It is one of the leading causes of cardiovascular mortality in the USA and Europe. While the clinical presentation and severity may vary, it is a life-threatening condition in its most severe form, defined as high-risk or massive PE. Therapeutic options in high-risk PE are limited. Current guidelines recommend the use of systemic thrombolytic therapy as first-line therapy (Level Ib). However, this treatment has important drawbacks including bleeding complications, limited efficacy in patients with recurrent PE or cardiac arrest, and formal contraindications. In this context, the use of venoarterial extracorporeal membrane oxygenation (VA-ECMO) in the management of high-risk PE has increased worldwide in the last decade. Strategies, including VA-ECMO as a stand-alone therapy or as a bridge to alternative reperfusion therapies, are associated with acceptable outcomes, especially if implemented before cardiac arrest. Nonetheless, the level of evidence supporting ECMO and alternative reperfusion therapies is low. The optimal management of high-risk PE patients will remain controversial until the realization of a prospective randomized trial comparing those cited strategies to systemic thrombolysis.

Novel Therapeutic Targets for the Treatment of Right Ventricular Remodeling: Insights from the Pulmonary Artery Banding Model

Right ventricular (RV) function is the main determinant of the outcome of patients with pulmonary hypertension (PH). RV dysfunction develops gradually and worsens progressively over the course of PH, resulting in RV failure and premature death. Currently, approved therapies for the treatment of left ventricular failure are not established for the RV. Furthermore, the direct effects of specific vasoactive drugs for treatment of pulmonary arterial hypertension (PAH, Group 1 of PH) on RV are not fully investigated. Pulmonary artery banding (PAB) allows to study the pathogenesis of RV failure solely, thereby testing potential therapies independently of pulmonary vascular changes. This review aims to discuss recent studies of the mechanisms of RV remodeling and RV-directed therapies based on the PAB model.

The Prognostic Value of Right Atrial Strain Imaging in Patients with Precapillary Pulmonary Hypertension

BACKGROUND

Right ventricular (RV) failure in patients with pulmonary hypertension (PH) is associated with unfavorable clinical events and a poor prognosis. Elevation of right atrial (RA) pressure is established as a marker for RV failure. However, the additive prognostic value of RA mechanical function is unclear.

METHODS

The authors tested the hypothesis that RA function by strain echocardiography has prognostic usefulness by studying 165 consecutive patients with precapillary PH defined invasively: mean pulmonary artery pressure ≥ 25 mm Hg and pulmonary capillary wedge pressure < 15 mm Hg. Speckle-tracking strain analyses of the right atrium and right ventricle were performed, along with routine measures. Peak RA strain values from six segments using generic speckle-tracking software were averaged to RA peak longitudinal strain, representing RA global reservoir function. The primary end point was all-cause mortality during 5 years of follow-up. RA strain was similarly analyzed in a control group of 16 normal subjects for comparison.

RESULTS

There were 151 patients with PH (mean age, 55 ± 16 years; 73% women; mean World Health Organization functional class, 2.6 ± 0.6), after 14 exclusions (three with atrial septal defects and 11 with left ventricular ejection fractions < 50%). RA strain measurement was feasible in 93% of patients and RV strain measurement in 88%. RA peak longitudinal strain was significantly reduced in patients with PH compared with control subjects, as expected (P < .001). During 5-year follow-up, 73 patients (48%) died. Patients with RA peak strain in the lowest quartile (<25%) had a significant risk for death (P = .006), even after correcting for confounding variables. RA strain was independently associated with survival in multivariate analysis (P = .039) and had additive prognostic value to RV strain (log-rank P = .01) in subgroup analysis.

CONCLUSIONS

RA peak longitudinal strain had additive prognostic usefulness to other clinical measures, including RV strain, RA area, and RA pressure, in patients with PH. RA mechanical function by strain imaging has potential for clinical applications in patients with PH.

A cascaded FC-DenseNet and level set method (FCDL) for fully automatic segmentation of the right ventricle in cardiac MRI

Accurate segmentation of the right ventricle (RV) from cardiac magnetic resonance imaging (MRI) images is an essential step in estimating clinical indices such as stroke volume and ejection fraction. Recently, image segmentation methods based on fully convolutional neural networks (FCN) have drawn much attention and shown promising results. In this paper, a new fully automatic RV segmentation method combining the FC-DenseNet and the level set method (FCDL) is proposed. The FC-DenseNet is efficiently trained end-to-end, using RV images and ground truth masks to make a per-pixel semantic inference. As a result, probability images are produced, followed by the level set method responsible for smoothing and converging contours to improve accuracy. It is noted that the iteration times of the level set method is only 4 times, which is due to the semantic segmentation of the FC-DenseNet for RV. Finally, multi-object detection algorithm is applied to locate the RV. Experimental results (including 45 cases, 15 cases for training, 30 cases for testing) show that the FCDL method outperforms the U-net + level set (UL) and the level set methods that use the same dataset and the cardiac functional parameters are computed robustly by the FCDL method. The results validate the FCDL method as an efficient and satisfactory approach to RV segmentation.

Association between right atrial area measured by echocardiography and prognosis among pulmonary arterial hypertension: a systematic review and meta-analysis

OBJECTIVE

The purpose of this meta-analysis was to evaluate the association between enlarged right atrial area (RAA), as measured by echocardiography, and prognosis of patients with pulmonary arterial hypertension (PAH).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

To identify potential publications, a comprehensive literature search through MEDLINE, the Cochrane database and the Embase database was performed up to December 2019.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies were included if they reported Cox regression based-HRs with 95% CIs for all-cause mortality or composite endpoint consisting of death and PAH-related events for echocardiography measurements of the RAA or the right atrial area index (RAAI) in patients with PAH.

DATA EXTRACTION AND SYNTHESIS

The unadjusted HR with 95% CI was extracted for the final pooled analysis. A random-effects model was used to determine the value of RAA/RAAI in the prognosis of patients with PAH. The data heterogeneity among the studies was estimated by the I² statistic and the Cochran Q-statistic.

RESULTS

Twelve studies with a total of 1085 patients with PAH were finally included in the meta-analysis. These studies had a mean follow-up time ranging from 9.2 months to 5.0 years. Their findings showed that patients with PAH with enlarged RAA/RAAI were associated with poor prognosis. The risk of all-cause mortality in patients with PAH was found to statistically increase by 50% for every 5-unit increase in RAA/RAAI (HR 1.50, 95% CI 1.28 to 1.75, p<0.001). Similarly, the risk of the composite endpoint also significantly increased by 53% for every 5-unit increase in RAA/RAAI (HR 1.53, 95% CI 1.23 to 1.89, p<0.001). Subgroup analyses in which the patients were stratified by RAA and RAAI were consistent with the main results.

CONCLUSION

The meta-analysis suggested that enlarged RAA/RAAI were associated with increased risk of poor prognosis in patients with PAH.

Effect of membrane insertion for tricuspid regurgitation using immersed-boundary lattice Boltzmann method

BACKGROUND

Tricuspid regurgitation is treated by valve repair or replacement. However, these methods have limitations, and alternative treatment methods are therefore required.

OBJECTIVES

In this study, a new method of tricuspid valve treatment using artificial membrane insertion is analyzed. We performed tricuspid valve simulations using an artificial membrane inserted into the right ventricle (RV) or right atrium (RA).

METHODS

We use the lattice Boltzmann method with the immersed boundary condition to model the structural motion of the valve leaflet. The effect of membrane insertion is analyzed in terms of the stress, force, and impulse on the valve leaflet, along with the velocity, pressure, jet volume, and Reynolds stress in the flow field.

RESULTS

While the use of either membrane (RA or RV) leads to improved valve closure relative to the use of no membrane, the RV membrane is more effective than the RA membrane in achieving improved valve closure. In addition, a larger membrane area with a shorter distance between the leaflet and membrane increases membrane efficacy.

CONCLUSION

Our results suggest that membrane insertion can form an effective new method for the treatment of tricuspid regurgitation.

Associations of 2D speckle tracking echocardiography-based right heart deformation parameters and invasively assessed hemodynamic measurements in patients with pulmonary hypertension

BACKGROUND

We aimed to evaluate associations of right atrial (RA) and right ventricular (RV) strain parameters assessed by 2D speckle tracking echocardiography (2D STE) with invasively measured hemodynamic parameters in patients with and without pulmonary hypertension (PH).

METHODS

In this study, we analyzed 78 all-comer patients undergoing invasive hemodynamic assessment by left and right heart catheterization. Standard transthoracic echocardiographic assessment was performed under the same hemodynamic conditions. RA and RV longitudinal strain parameters were analyzed using 2D STE. PH was defined as invasively obtained mean pulmonary arterial pressure (mPAP) ≥25 mmHg at rest and was further divided into pre-capillary PH (pulmonary capillary wedge pressure [PCWP] ≤ 15 mmHg), post-capillary PH (PCWP > 15 mmHg) and combined PH (PCWP > 15 mmHg and difference between diastolic PAP and PCWP of ≥7 mmHg). Correlation analyses between variables were calculated with Pearson's or Spearman's correlation coefficient as applicable.

RESULTS

Out of 78 patients, 45 presented with PH. Within the PH group, 39 had post-capillary, five had combined pre- and post-capillary PH, and one had pre-capillary PH. Patients with PH had a significantly increased RA area (PH 22.0 ± 9.2 cm², non-PH 17.3 ± 10.7 cm²; p = 0.003) and end-systolic RV area (PH 14.7 ± 6.1, non-PH 11.9 ± 4.8 cm²; p = 0.022). RV mid strain was significantly reduced in PH (PH -17.4 ± 7.8, non-PH: - 21.6 ± 5.5; p = 0.019). Average peak systolic RA strain (RAS) and average peak systolic RV strain (RVS) showed a significant association with mPAP (r = - 0.470, p = 0.001 and r = 0.490, p = 0.001, respectively) and with PCWP (r = - 0.296, p = 0.048 and r = 0.365, p = 0.015, respectively) in patients with PH. Furthermore, RV apical, mid and basal strain as well as RV free wall strain showed moderate associations with mPAP. In patients without PH, there were no associations detectable between RA or RV strain parameters and mPAP and PCWP.

CONCLUSION

In an all-comer cohort, RA and RV strain parameters showed significant associations with invasively assessed mPAP and PCWP in patients with predominantly post-capillary PH. These associations may be useful in clinical practice to assess the impact of post-capillary PH on myocardial right heart function.

Chronic progression of cardiac surgery associated acute kidney injury: Intermediary role of acute kidney disease

OBJECTIVE

The association between acute kidney injury (AKI) and chronic kidney disease (CKD) remains elusive in cardiac surgery. We investigated the association between postoperative AKI and CKD development, emphasizing the intermediary role of acute kidney disease (AKD), in patients undergoing valvular heart surgery.

METHODS

We assessed the occurrence of postoperative AKI (7 days postsurgery), AKD (3 months postsurgery), and CKD (12 months postsurgery) in 1386 patients. The primary outcome was the development of AKD and CKD according to AKI occurrence. Relevant risk factors of AKI, AKD, and CKD were identified through multivariable regression analysis.

RESULTS

AKI occurred in 23.9% of patients with normal preoperative renal function. Even with early recovery of renal function within 3 days, AKI increased the risk of AKD (odds ratio [OR], 3.21; 95% confidence interval [CI], 1.98-5.20, P < .001) and CKD (OR, 2.86; 95% CI, 1.68-4.86, P < .001), whereas persistent AKI further increased the risk of AKD (OR, 12.07; 95% CI, 5.56-26.21, P < .001) and CKD (OR, 10.54; 95% CI, 4.01-27.76, P < .001). We also found these relationships in patients with pre-existing renal dysfunction. Multivariable analysis identified 3-month postoperative heart failure and high right ventricular systolic pressure as independent risk factors for CKD.

CONCLUSIONS

Even after early recovery, postvalvular heart surgery AKI was associated with increased risk of CKD via AKD in a graded manner related to AKI severity and persistence. Postoperative cardiac dysfunction assessed 3 months postsurgery also significantly influenced CKD development, indicating a need for close follow-up of cardiac and renal function to improve patient outcomes.

Clinical Utility and Prognostic Value of Right Atrial Function in Pulmonary Hypertension

Background Although right atrial (RA) enlargement is an established marker for adverse outcomes, the prognostic importance of RA dysfunction independent of RA size in pulmonary arterial hypertension is not known. Methods and Results Study subjects with pulmonary arterial hypertension were prospectively enrolled from 2010 to 2014. RA function was measured using RA speckle-tracking longitudinal strain and strain rate (SR) during each phase of the cardiac cycle: (1) RA reservoir (peak longitudinal strain, peak systolic SR), (2) RA conduit (peak early diastolic SR), and (3) RA active contraction (peak active contraction strain, peak contraction SR). The primary outcome was a composite of time to hospitalization or death assessed on follow-up. A total of 63 subjects had complete echocardiographic data. Of these, 91% were females, and the mean age was 58±12 years. During the follow-up period (range: 1-58 months), 39 were hospitalized or had died. After multivariable adjustment for age, sex, and left atrial size, peak longitudinal strain, peak active contraction strain, and peak early diastolic SR were significantly associated with increased risk of the composite outcome ( P=0.0005, P=0.0167, and P=0.0054, respectively). Conclusions RA dysfunction independently predicts mortality and hospitalizations in patients with pulmonary arterial hypertension.

Adaptation to acute pulmonary hypertension in pigs

The extent of right ventricular compensation compared to the left ventricle is restricted and varies among individuals, which makes it difficult to define. While establishing a model of acute pulmonary hypertension in pigs we observed two different kinds of compensation in our animals. Looking deeper into the hemodynamic data we tried to delineate why some animals could compensate and others could not. Pulmonary hypertension (mean pressure 45 mmHg) was induced gradually by infusion of a stable thromboxane A₂ analogue U46619 in a porcine model (n = 22). Hemodynamic data (pressure‐volume loops, strain‐analysis of echocardiographic data and coronary flow measurements) were evaluated retrospectively for the short‐term right ventricular compensatory mechanisms and limits (Roehl et al. [2012] Acta Anaesthesiol. Scand., 56:449–58) 10 animals showed stable arterial blood pressures, whereas 12 pigs exhibited a significant drop of 16.4 ± 9.9 mmHg. Cardiac output and heart rate were comparable in both groups. In contrast, right ventricular contractility and coronary flow only rose in the stable group. The unchanging values in the decrease group correlated with an increasing ST‐segment depression and a loss of ventricular synchronism and resulted in a larger septum bulging to the right ventricle. Simultaneously, a reduced left‐ventricular end‐diastolic volume and a missing improvement in contractility in the posterior septal and inferior free wall of the left ventricle have been observed. Our findings suggest that right ventricular compensation during acute pulmonary hypertension is strongly dependent on the individual capability to increase coronary flow. The cause for inter‐individual variability could be the dimension and reactivity of the coronary system.

Pathophysiology of right ventricular failure in acute pulmonary embolism and chronic thromboembolic pulmonary hypertension: a pictorial essay for the interventional radiologist

Pulmonary embolus (PE) is the third most common cause of cardiovascular death with more than 600,000 cases occurring in the USA per year. About 45% of patients with acute PE will have acute right ventricular failure, and up to 3.8% of patients will develop chronic thromboembolic pulmonary hypertension (CTEPH) with progressive, severe, chronic heart failure. The right ventricle (RV) is constructed to accommodate a low-resistance afterload. Increases in afterload from acute massive and submassive PE and CTEPH may markedly compromise the RV function leading to hemodynamic collapse and death. The purpose of this educational manuscript is to instruct on the pathophysiology of RV failure in massive and submassive PE and CTEPH. It is important to understand the pathophysiology of these diseases as it provides the rationale for therapeutic intervention by the Interventional Radiologist. We review here the pathophysiology of right ventricular (RV) failure in acute massive and submassive PE and CTEPH.

Right Ventricular Function in Left Heart Disease

Right ventricular (RV) function is an independent prognostic factor for short- and long-term outcomes in cardiac surgical patients. Patients with mitral valve (MV) disease are at increased risk of RV dysfunction before and after MV operations. Yet RV function is not part of criteria for decision making or risk stratification in this setting. The role of MV disease in the development of pulmonary hypertension (PHTN) and the ultimate impact of PHTN on RV function have been well described. Nonetheless, there are other mechanisms by which MV disease and MV surgery affect RV performance. Research suggests that PHTN may not be the most important determinant of RV dysfunction. Both RV dysfunction and PHTN have independent prognostic significance. This review explores the unique anatomic and functional features of the RV and the pathophysiologic and prognostic implications of RV dysfunction in patients with MV disease in the perioperative period.

Local Motion Intensity Clustering (LMIC) Model for Segmentation of Right Ventricle in Cardiac MRI Images

Analysis of the morphology and function of the right ventricle (RV) can be used for the prediction and diagnosis of cardiovascular disease. Accurate description of the structure and function of heart can be provided by analyzing cardiac magnetic resonance imaging (MRI) images. Noise interference and intensity inhomogeneity of MRI images can be addressed by using a local intensity clustering (LIC) model. However, the segmentation of the RV in MRI images still remains a challenge mainly due to its ill-defined borders. To address such a challenge, an algorithm for segmenting the RV based on a local motion intensity clustering (LMIC) model is proposed in this paper. The LMIC model combines the LIC model with the motion intensity information, due to cardiac motion and blood flow. The motion intensity is calculated by using the Lucas Kanade optical flow method and utilized in the LMIC model as an energy parameter. Because the motion intensity of the RV region is stronger than other areas, the RV can be accurately segmented by this approach. Experimental results demonstrate that the LMIC model is able to address the challenge of the ill-defined RV borders in cardiac MRI images and improved RV segmentation accuracy over existing methods.

Interventional Therapies in Pulmonary Hypertension

Despite advances in drug therapy, pulmonary hypertension-particularly arterial hypertension (PAH)-remains a fatal disease. Untreatable right heart failure (RHF) from PAH eventually ensues and remains a significant cause of death in these patients. Lowering pulmonary input impedance with different PAH-specific drugs is the obvious therapeutic target in RHF due to chronically increased afterload. However, potential clinical gain can also be expected from attempts to unload the right heart and increase systemic output. Atrial septostomy, Potts anastomosis, and pulmonary artery denervation are interventional procedures serving this purpose. Percutaneous balloon pulmonary angioplasty, another interventional therapy, has re-emerged in the last few years as a clear alternative for the management of patients with distal, inoperable, chronic thromboembolic pulmonary hypertension. The current review discusses the physiological background, experimental evidence, and potential clinical and hemodynamic benefits of all these interventional therapies regarding their use in the setting of RHF due to severe pulmonary hypertension.

Remodeling of ventricular repolarization in experimental right ventricular hypertrophy

BACKGROUND

To understand electrophysiological mechanisms that underlie the progression of compensated right ventricular hypertrophy (RVH) to heart failure, the purpose of the study was to evaluate remodeling of ventricular repolarization in connection with hemodynamic abnormalities and vulnerability of the heart ventricles to arrhythmias in RVH rats with pulmonary arterial hypertension (PAH) and heart failure.

METHODS

PAH followed by heart failure was induced by monocrotaline in adult female Wistar rats. Unipolar epicardial electrograms and cardiac hemodynamic parameters were recorded in situ. Vulnerability to ventricular arrhythmias was measured as the threshold dose of aconitine required to produce sustained ventricular tachycardia. Histological examination of the heart ventricles was performed. Activation-recovery intervals (ARIs) and ARI dispersions were used as indices of durations and heterogeneity of repolarization respectively to assess ventricular repolarization.

RESULTS AND CONCLUSIONS

The development of compensated RVH was characterized by the dramatic prolongation of repolarization against the less expressed increase in repolarization heterogeneity, whereas the dramatic increase in repolarization heterogeneity against the less expressed but inhomogeneous prolongation of repolarization occurred in the progression of compensated RVH to heart failure. These changes increased vulnerability of the failing heart but not the compensated heart to aconitine-induced ventricular arrhythmias.

Left Ventricular Velocity of Propagation: A Useful Non-Invasive Measurement When Assessing Hemodynamic Alterations in Pulmonary Arterial Hypertension

Background

Left ventricular (LV) velocity of propagation (Vp) has been shown to be inversely related to the LV relaxation time constant. We sought to examine Vp from a group of chronic pulmonary hypertension (cPH) patients and compare these values to Vp obtained in normal individuals and patients with known LV diastolic dysfunction (LVDD).

Methods

Echo-Doppler data and Vp measurements were retrospectively collected from all patients. The studied population was divided into four groups. Group I comprised of 15 patients with normal LV diastole, group II included 27 patients with stage 1 LVDD, group III was made up of 27 patients with stage 2 LVDD, and group IV included 66 patients with cPH.

Results

In the cPH population studied, patients had smaller end-diastolic LV cavities with the highest Vp values but their early mitral inflow to Vp ratios were not different from healthy controls. In addition, Vp values and pulmonary wedge capillary pressures were significantly associated in patients with LV dysfunction or pulmonary hypertension (P < 0.01).

Conclusions

LVVp might be a useful non-invasive measurement to be routinely obtained in cPH patients as it probably not only reflects the compressive forces being exerted on the LV, known to increase Vp, but also might be quite useful for the non-invasive assessment of pulmonary capillary wedge pressures in these patients.

Impaired right and left ventricular mechanics in adults with pulmonary hypertension and congenital shunts

AIMS

To assess left ventricle mechanics in Eisenmenger physiology patients with congenital shunts, and their relationship with the right ventricle, and to consider the clinical usefulness of this information.

METHODS

The study involved 28 patients with pulmonary artery hypertension (PAH) and congenital shunt, matched with 28 healthy participants. Standard echocardiography and pulsed wave tissue Doppler imaging were employed to analyze systolic and diastolic ventricular function, the myocardial performance index (MPI) of ventricles, and the strain and strain rate along the left ventricle lateral wall, septum, and right ventricle free wall.

RESULTS

The left ventricle ejection fraction was similar in the two groups. However, despite normal standard left ventricle measures, patients presented parameters of defective myocardial mechanics: mitral peak systolic velocity (S') (cm/s) (8.6 (7.6-10.9) vs. 10.7 (8.6-12.5); P = 0.002) was higher, whereas left ventricle-MPI was lower (0.54 ± 01 vs. 0.32 ± 0.07, P < 0.001). Right ventricle-MPI and right ventricle global strain were correlated significantly with left ventricle-MPI and left ventricle global strain (r = 0.74, P < 0.001; r = 0.442, P < 0.001, respectively). Clinically, the six-minute walking test results were correlated negatively with left ventricle-MPI (r = -0.69, P < 0.001), whereas the functional class was positively correlated (r = 0.36, P < 0.001). In conclusion, left ventricle mechanics and geometry are impaired in Eisenmenger syndrome patients, although conventional evaluation is in the normal range. Our results highlight the significance of ventricular interdependence in PAH and provide a useful tool for improving the clinical management of these patients.

Endoglin selectively modulates transient receptor potential channel expression in left and right heart failure

INTRODUCTION

Transient receptor potential (TRP) channels are broadly expressed cation channels that mediate diverse physiological stimuli and include canonical (TRPC), melastatin (TRPM), and vanilloid (TRPV) subtypes. Recent studies have implicated a role for TRPC6 channels as an important component of signaling via the cytokine, transforming growth factor beta 1 (TGFβ1) in right (RV) or left ventricular (LV) failure. Endoglin (Eng) is a transmembrane glycoprotein that promotes TRPC6 expression and TGFβ1 activity. No studies have defined biventricular expression of all TRP channel family members in heart failure.

HYPOTHESIS

We hypothesized that heart failure is associated with distinct patterns of TRP channel expression in the LV and RV.

METHODS

Paired viable LV and RV free wall tissue was obtained from human subjects with end-stage heart failure (n=12) referred for cardiac transplantation or biventricular assist device implantation. Paired LV and RV samples from human subjects without heart failure served as controls (n=3). To explore a functional role for Eng as a regulator of TRP expression in response to RV or LV pressure overload, wild-type (Eng+/+) and Eng haploinsufficient (Eng+/-) mice were exposed to thoracic aortic (TAC) or pulmonary arterial (PAC) constriction for 8weeks. Biventricular tissue was analyzed by real-time polymerase chain reaction.

RESULTS

Compared to nonfailing human LV and RV samples, mRNA levels of TRPC1, 3, 4, 6, and TRPV-2 were increased and TRPM2, 3, and 8 were decreased in failing LV and RV samples. TRPC1 and 6 levels were higher in failing RV compared to failing LV samples. After TAC, murine LV levels of TPRC1 and 6 were increased in both Eng+/+ and Eng+/- mice compared to sham controls. LV levels of TRPC4, TRPM3 and 7, TRPV2 and 4 were increased in Eng+/+, not in Eng+/- mice after TAC. After PAC, all TRP channel family members were increased in the RV, but not LV, of Eng+/+ compared to sham controls. In contrast to Eng+/+, PAC did not increase RV or LV levels of TRP channels in Eng+/- mice.

CONCLUSIONS

This is the first study to demonstrate that TRP channels exhibit distinct profiles of expression in the LV and RV of patients with heart failure and in murine models of univentricular pressure overload. We further introduce that the TGFβ1 coreceptor Eng selectively regulates expression of multiple TRP channels in the setting of LV or RV pressure overload.

Impaired Left Ventricular Longitudinal Function in Idiopathic Pulmonary Arterial Hypertension Children

Background: Pulmonary arterial hypertension is associated with right ventricular dilation and failure. As a result, left ventricular geometry is affected by shifting of the interventricular septum towards the left ventricle.

Aim of the study: The aim of the study was to assess the effect of chronic right ventricular pressure overload on left ventricular longitudinal function and synchronicity in idiopathic pulmonary arterial hypertension children, using speckle-tracking echocardiography.

Material and methods: We prospectively evaluated 13 children (5 with idiopathic pulmonary arterial hypertension and 8 sex- and age-matched controls) using conventional and speckle-tracking echocardiography and clinical status (WHO functional class). Left ventricular longitudinal strain curve was generated for 17 segments and global left ventricular longitudinal peak systolic strain was calculated. Dyssynchrony index of the left ventricle was determined calculating the standard deviation of time to peak-systolic strain for 12 left ventricular, 6 basal and 6 midventricular segments, from short axis views.

Results: Strain imaging showed significantly decreased global left ventricular longitudinal strain and increased dyssynchrony index in idiopathic pulmonary arterial hypertension patients as compared with controls (−16.80 ± 2.94 vs. −21.50 ± 1.60, p = 0.003, and 53.80 ± 16.72 vs. 22.25 ± 6.18, p=0.0001, respectively). There was a significant correlation between left ventricular longitudinal strain, dyssynchrony index and right ventricular fractional area changes (r = −0.66, p = 0.013, and r = −0.72, p = 0.005, respectively), right ventricular myocardial performance index (r = 0.86, p = 0.0001, and r = 0.93, p = 0.000, respectively), and LV eccentricity index (r = 0.82, p=0.001, and r = 0.93, p = 0.000, respectively) in the study population as a whole.

Conclusions: Left ventricular longitudinal systolic strain and synchronicity are impaired in idiopathic pulmonary arterial hypertension children with normal left ventricular ejection fraction.

Prognostic value of TAPSE after therapy optimisation in patients with pulmonary arterial hypertension is independent of the haemodynamic effects of therapy

Objective

To evaluate the prognostic significance of right ventricular function assessed by echocardiography after start or escalation of targeted therapy in patients with pulmonary arterial hypertension.

Methods

Study design: longitudinal study. Setting: tertiary referral centre for pulmonary hypertension. Patients: 81 consecutive patients with pulmonary arterial hypertension (33 naive and 48 prevalent). Interventions: right heart catheterisation and echocardiography performed prior to starting or escalating targeted therapy and repeated in 55 patients after 4–12 months of therapy. Main outcome measure: survival after follow-up examinations.

Results

11 patients died and 7 were lost to follow-up during the first year; 8 patients underwent first follow-up evaluation beyond 1 year. 55 patients were re-evaluated after therapy; during the subsequent follow-up period of 25 months, 9 patients died, 7 worsened from WHO I/II to III/IV and 15 remained in WHO III/IV despite therapy. A baseline tricuspid annular plane systolic excursion (TAPSE) ≥15 mm was associated with a lower risk of death (HR=0.32; 95% CI 0.12 to 0.83, p=0.012). Attaining a TAPSE≥15 mm after therapy was associated with a significantly lower risk of death or clinical worsening (HR=0.2; 95% CI 0.1 to 0.6, p=0.002) and a lower risk of death which approached statistical significance (HR=0.3; 95% CI 0.2 to 1.1, p=0.075). Per cent changes in TAPSE were loosely related to changes in pulmonary vascular resistances after therapy (R=0.37).

Conclusions

In patients with pulmonary arterial hypertension, the evaluation of right ventricular function by TAPSE after targeted therapy is useful to predict subsequent prognosis, regardless of the haemodynamic effects of therapy.

Right Bundle Branch Block and Electromechanical Coupling of the Right Ventricle: An Echocardiographic Study

Background:

A growing body of evidence suggests that the presence of a right bundle branch block (RBBB) is a negative prognostic indicator in patients with and without preexisting heart disease. Even though electromechanical activation of the right ventricle (RV) in patients with RBBB and pulmonary hypertension (PH) has been investigated; a direct comparison of the presence of RBBB, on the duration of RV mechanical systole using echocardiography has not been studied.

Materials and Methods:

In this retrospective study, we analyzed the echocardiograms of 40 patients by measuring the magnitude and timing of tricuspid annulus plane systolic excursion (TAPSE) and tricuspid annulus systolic velocity (TA S’). Patients were selected to form four groups of ten patients based on the presence or absence of RBBB and PH to determine if RBBB has any effect on the time-to-peak of TAPSE or TA S’, which for our purposes serves as a measure of duration of RV mechanical systole.

Results:

Our results demonstrate that RBBB leads to a measurable prolongation of TAPSE and TA S’ in patients without PH. Time-to-peak of TAPSE or TA S’ was not significantly prolonged in patients with PH.

Conclusions:

The results of this pilot study show that RV mechanical systole is prolonged in patients with RBBB, and the addition of PH attenuates this change. Additional prospective studies are now required to elucidate further the electrical and mechanical dyssynchrony that occurs as a result of RBBB, and how these new echocardiographic measurements can be applied clinically to risk stratify patients with RBBB and PH.

Evaluation of right atrial function using right atrial speckle tracking analysis in patients with pulmonary artery hypertension

BACKGROUND

In patients with pulmonary artery hypertension (PAH), right ventricular pressure overload eventually causes right heart failure (RHF), leading to a poor prognosis. Right atrial (RA) overload and RA dysfunction occur in patients with PAH-complicated RHF.

OBJECTIVES

We evaluated RA function using right atrial longitudinal strain (RALS) by two-dimensional speckle tracking echocardiography (2D-STE) and investigated the association between RALS and the severity of RHF in patients with pulmonary artery hypertension (PAH) noninvasively.

METHODS

We performed 2D-STE in 56 PAH patients and 20 normal control subjects. The peak global RALS and peak global RA longitudinal strain rate (RALSR) were analyzed by 2D-STE. Simultaneous right heart catheterization was performed to determine the right atrial pressure (RAP) and cardiac index (CI).

RESULTS

Peak global RALS (34.6 ± 14.1 vs. 58.3 ± 9.9%, p < 0.0001) and peak global RALSR (2.5 ± 1.3 vs. 3.1 ± 1.2 s(-1), p < 0.0001) were significantly lower in PAH patients compared with normal controls. There was a significant negative correlation between peak global RALS and RAP (r = -0.8037, p < 0.0001). There was a significant positive correlation between peak global RALS and CI (r = 0.8179, p < 0.0001). Peak global RALSR was also correlated with RAP (r = -0.7308, p < 0.0001) and CI (r = 0.7596, p < 0.0001).

CONCLUSIONS

RALS and RALSR by 2D-STE were useful for noninvasive evaluation of RA dysfunction and the severity of RHF in patients with PAH.

Impaired Global Right Ventricular Longitudinal Strain Predicts Long-Term Adverse Outcomes in Patients with Pulmonary Arterial Hypertension

Background

New 2-dimensional strain echocardiography enables quantification of right ventricular (RV) mechanics by assessing global longitudinal strain of RV (GLSRV) in patients with pulmonary arterial hypertension (PAH). However, the prognostic significance of impaired GLSRV is unclear in these patients.

Methods

Comprehensive echocardiography was performed in 51 consecutive PAH patients without atrial fibrillation (40 females, 48 ± 14 years old) with long-term follow-up. GLSRV was measured with off-line with velocity vector imaging (VVI, Siemens Medical System, Mountain View, CA, USA).

Results

GLSRV showed significant correlation with RV fractional area change (r = -0.606, p < 0.001), tricuspid annular plane systolic excursion (r = -0.579, p < 0.001), and RV Tei index (r = 0.590, p < 0.001). It showed significant correlations with pulmonary vascular resistance (r = 0.469, p = 0.001) and B-natriuretic peptide concentration (r = 0.351, p = 0.012). During a clinical followup time (45 ± 15 months), 20 patients experienced one or more adverse events (12 death, 2 lung transplantation, and 15 heart failure hospitalization). After multivariate analysis, age [hazard ratio (HR) = 2.343, p = 0.040] and GLSRV (HR = 2.122, p = 0.040) were associated with adverse clinical events. Age (HR = 3.200, p = 0.016) and GLSRV (HR = 2.090, p = 0.042) were also significant predictors of death. Impaired GLSRV (≥ -15.5%) was associated with lower event-free survival (HR = 4.906, p = 0.001) and increased mortality (HR = 8.842, p = 0.005).

Conclusion

GLSRV by VVI showed significant correlations with conventional echocardiographic parameters indicating RV systolic function. Lower GLSRV (≥ -15.5%) was significantly associated with presence of adverse clinical events and deaths in PAH patients.

Importance of End-Diastolic Rather than End-Systolic Right Atrial Size in Chronic Pulmonary Hypertension

BACKGROUND

Right atrial (RA) enlargement has been associated with worse clinical outcomes in chronic pulmonary hypertension (cPH) patients. Even though current guidelines only recommend measurement of RA dimensions at the end of ventricular systole in these patients, there is paucity of information regarding the potential utility of RA dimensions obtained at the end of ventricular diastole.

METHODS

In this retrospective study, standard echocardiographic data were collected from 80 studies. The population studied was divided into Group I that consisted of 35 patients (52 ± 10 years) without PH while Group II included 45 patients (56 ± 14 years; P = 0.2) with cPH. RA measurements were obtained not only at the end of ventricular systole, but also at the end of ventricular diastole to determine which RA measurement was more indicative of abnormal right ventricular afterload.

RESULTS

Even though all RA measurements were abnormal, RA area (>8.4 cm(2) ) measured at the end of ventricular diastole was the most useful RA variable to identify cPH patients with elevated pulmonary pressures (P < 0.0001) and with an abnormal pulmonary vascular resistance (P = 0.001).

CONCLUSIONS

Based on these results, it appears that isolated RA measurements made at the end of ventricular systole are insufficient to fully explain the hemodynamic load of cPH. Additional studies are now required to determine whether sequential monitoring of the composite change in RA dimensions that occur throughout the cardiac cycle over time correlates better with response to vasodilator therapy and overall clinical outcomes.

The need to recognize the pulmonary circulation and the right ventricle as an integrated functional unit: facts and hypotheses (2013 Grover Conference series)

For many patients with severe pulmonary arterial hypertension, heart failure-and, in particular, right heart failure-is the final chapter of their chronic illness. Targeted therapy for pulmonary hypertension is effective only if the right ventricular ejection fraction is maintained or improved. Because improvement of right heart function and reversal of right heart failure are treatment goals, it is important to investigate the cellular and molecular mechanisms that cause right heart failure. Here, we propose that right ventricular capillary rarefaction is an important hallmark of right heart failure and consider that the "sick lung circulation" and the pressure-overloaded right ventricle constitute a functional unit.

Adaptive capacity of the right ventricle: why does it fail?

Only in recent years has the right ventricle (RV) function become appreciated to be equally important to the left ventricle (LV) function to maintain cardiac output. Right ventricular failure is, irrespectively of the etiology, associated with impaired exercise tolerance and poor survival. Since the anatomy and physiology of the RV is distinctly different than that of the LV, its adaptive mechanisms and the pathways involved are different as well. RV hypertrophy is an important mechanism of the RV to preserve cardiac output. This review summarizes the current knowledge on the right ventricle and its response to pathologic situations. We will focus on the adaptive capacity of the right ventricle and the molecular pathways involved, and we will discuss potential therapeutic interventions.

Interventional and surgical therapeutic strategies for pulmonary arterial hypertension: Beyond palliative treatments

Despite significant advances in pharmacological treatments, pulmonary arterial hypertension remains an incurable disease with an unreasonably high morbidity and mortality. Although specific pharmacotherapies have shifted the survival curves of patients and improved exercise endurance as well as quality of life, it is also true that these pharmacological interventions are not always accessible (particularly in developing countries) and, perhaps most importantly, not all patients respond similarly to these drugs. Furthermore, many patients will continue to deteriorate and will eventually require an additional, non-pharmacological, intervention. In this review we analyze the role of atrial septostomy and Potts anastomosis in the management of patients with pulmonary arterial hypertension, we summarize the current worldwide clinical experience (case reports and case series), and discuss why these interventional/surgical strategies might have a therapeutic role beyond that of a "bridge" to transplantation.

Atrial Septostomy: A Contemporary Review

Pulmonary arterial hypertension (PAH) is a rare disease, but it boasts significant morbidity and mortality. Although remarkable achievements have been made in the medical treatment of PAH, there is a role for invasive or surgical procedures in patients with progressive disease despite optimal medical therapy or with no access to such therapy. Atrial septostomy creates a right-to-left intracardiac shunt to decompress the overloaded right ventricle. Despite significant advances to validate and improve this palliative procedure, as well as recent reports of improved outcomes, it is only slowly being adopted. This article aims to detail the history, indications, contraindications, procedural techniques, and outcomes of atrial septostomy. We will also shed light on some of the newer interventions, inspired by the same physiological concept, that are being evaluated as potential palliative modalities in patients with PAH.

Right ventricular segmentation in cardiac MRI with moving mesh correspondences

This study investigates automatic propagation of the right ventricle (RV) endocardial and epicardial boundaries in 4D (3D+time) magnetic resonance imaging (MRI) sequences. Based on a moving mesh (or grid generation) framework, the proposed algorithm detects the endocardium and epicardium within each cardiac phase via point-to-point correspondences. The proposed method has the following advantages over prior RV segmentation works: (1) it removes the need for a time-consuming, manually built training set; (2) it does not make prior assumptions as to the intensity distributions or shape; (3) it provides a sequence of corresponding points over time, a comprehensive input that can be very useful in cardiac applications other than segmentation, e.g., regional wall motion analysis; and (4) it is more flexible for congenital heart disease where the RV undergoes high variations in shape. Furthermore, the proposed method allows comprehensive RV volumetric analysis over the complete cardiac cycle as well as automatic detections of end-systolic and end-diastolic phases because it provides a segmentation for each time step. Evaluated quantitatively over the 48-subject data set of the MICCAI 2012 RV segmentation challenge, the proposed method yielded an average Dice score of 0.84±0.11 for the epicardium and 0.79±0.17 for the endocardium. Further, quantitative evaluations of the proposed approach in comparisons to manual contours over 23 infant hypoplastic left heart syndrome patients yielded a Dice score of 0.82±0.14, which demonstrates the robustness of the algorithm.

Pulmonary arterial hypertension: the key role of echocardiography

Echocardiography is a key screening tool in the diagnostic algorithm of pulmonary arterial hypertension (PAH). It provides an estimate of right ventricular function and pulmonary artery pressure, either at rest or during exercise, and is useful in ruling out secondary causes of pulmonary hypertension (PH) such as left heart disease or congenital heart disease. Several studies have showed that echocardiography is insufficiently precise as single tool for the ultimate diagnosis of PH respect to the right heart catheterization, considered the gold standard technique. Echocardiography is valuable in assessing prognosis and treatment options, monitoring the efficacy of specific therapeutic interventions, and detecting the preclinical stages of disease. The ideal imaging modality for accurate noninvasive assessment of the right heart should be accurate and precise, not influenced by loading conditions, routinely practicable and easily repeatable. For all such reasons and considering that PAH is a rare and severe condition, a complete noninvasive assessment of right heart function requires a deep knowledge of the disease and a multimodality approach.

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.

Systems approach to the study of stretch and arrhythmias in right ventricular failure induced in rats by monocrotaline

We demonstrate the synergistic benefits of using multiple technologies to investigate complex multi-scale biological responses. The combination of reductionist and integrative methodologies can reveal novel insights into mechanisms of action by tracking changes of in vivo phenomena to alterations in protein activity (or vice versa). We have applied this approach to electrical and mechanical remodelling in right ventricular failure caused by monocrotaline-induced pulmonary artery hypertension in rats. We show arrhythmogenic T-wave alternans in the ECG of conscious heart failure animals. Optical mapping of isolated hearts revealed discordant action potential duration (APD) alternans. Potential causes of the arrhythmic substrate; structural remodelling and/or steep APD restitution and dispersion were observed, with specific remodelling of the Right Ventricular Outflow Tract. At the myocyte level, [Ca(2+)]i transient alternans were observed together with decreased activity, gene and protein expression of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA). Computer simulations of the electrical and structural remodelling suggest both contribute to a less stable substrate. Echocardiography was used to estimate increased wall stress in failure, in vivo. Stretch of intact and skinned single myocytes revealed no effect on the Frank-Starling mechanism in failing myocytes. In isolated hearts acute stretch-induced arrhythmias occurred in all preparations. Significant shortening of the early APD was seen in control but not failing hearts. These observations may be linked to changes in the gene expression of candidate mechanosensitive ion channels (MSCs) TREK-1 and TRPC1/6. Computer simulations incorporating MSCs and changes in ion channels with failure, based on altered gene expression, largely reproduced experimental observations.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Perioperative management in patients with pulmonary hypertension

Patients with pulmonary hypertension (PH) are being encountered more commonly in the perioperative period and this trend is likely to increase as improvements in the recognition, management, and treatment of the disease continue to occur. Management of these patients is challenging due to their tenuous hemodynamic status. Recent advances in the understanding of the patho-physiology, risk factors, monitoring, and treatment of the disease provide an opportunity to reduce the morbidity and mortality associated with PH in the peri-operative period. Management of these patients requires a multi-disciplinary approach and meticulous care that is best provided in centers with vast experience in PH.

In this review, we provide a detailed discussion about oerioperative strategies in PH patients, and give evidence-based recommendations, when applicable.

Reducing endoglin activity limits calcineurin and TRPC-6 expression and improves survival in a mouse model of right ventricular pressure overload

BACKGROUND

Right ventricular (RV) failure is a major cause of mortality worldwide and is often a consequence of RV pressure overload (RVPO). Endoglin is a coreceptor for the profibrogenic cytokine, transforming growth factor beta 1 (TGF-β1). TGF-β1 signaling by the canonical transient receptor protein channel 6 (TRPC-6) was recently reported to stimulate calcineurin-mediated myofibroblast transformation, a critical component of cardiac fibrosis. We hypothesized that reduced activity of the TGF-β1 coreceptor, endoglin, limits RV calcineurin expression and improves survival in RVPO.

METHODS AND RESULTS

We first demonstrate that endoglin is required for TGF-β1-mediated calcineurin/TRPC-6 expression and up-regulation of alpha-smooth muscle antigen (α-SMA), a marker of myofibroblast transformation, in human RV fibroblasts. Using endoglin haploinsufficient mice (Eng(+/-)) we show that reduced endoglin activity preserves RV function, limits RV fibrosis, and attenuates activation of the calcineurin/TRPC-6/α-SMA pathway in a model of angio-obliterative pulmonary hypertension. Next, using Eng(+/-) mice or a neutralizing antibody (Ab) against endoglin (N-Eng) in wild-type mice, we show that reduced endoglin activity improves survival and attenuates RV fibrosis in models of RVPO induced by pulmonary artery constriction. To explore the utility of targeting endoglin, we observed a reversal of RV fibrosis and calcineurin levels in wild-type mice treated with a N-Eng Ab, compared to an immunoglobulin G control.

CONCLUSION

These data establish endoglin as a regulator of TGF-β1 signaling by calcineurin and TRPC-6 in the RV and identify it as a potential therapeutic target to limit RV fibrosis and improve survival in RVPO, a common cause of death in cardiac and pulmonary disease.