Julien Guihaire

Non-invasive indices of right ventricular function are markers of ventricular–arterial coupling rather than ventricular contractility: insights from a porcine model of chronic pressure overload

AIMS To investigate the physiological correlates of indices of RV function in a model of chronic pressure overload. METHODS AND RESULTS Chronic pulmonary hypertension (PH) was induced in piglets by ligation of the left pulmonary artery (PA) followed by weekly embolization of right lower lobe arteries for 5 weeks (the PH group, n = 11). These animals were compared with sham-operated animals (controls, n = 6). At 6 weeks, a subgroup of five PH pigs underwent surgical reperfusion of the left lung and four others were followed until 12 weeks without treatment. Right ventricular function was assessed using echocardiography and conductance catheter measurements. At 6 weeks, mean PA pressure was higher in PH group compared with controls (35 ± 9 vs. 14 ± 2 mmHg, P < 0.01). Although RV elastance (Ees) increased at 6 weeks in the PH group (0.55 ± 0.09 vs. 0.38 ± 0.05 mmHg/mL, P < 0.001), ventricular-arterial coupling measured by the ratio of Ees on PA elastance (Ea) was decreased (0.68 ± 0.17 vs. 1.18 ± 0.18, P < 0.001). There was a strong direct relationship between Ees/Ea and indices of RV function, while relationship between Ees and indices of RV function was moderate. Changes in indices of RV function with time and after left lung reperfusion were associated with changes in Ees/Ea. CONCLUSION Usual indices of RV function are associated with ventricular-arterial coupling rather than with ventricular contractility in a model of chronic pressure overload.

Septal Curvature Is Marker of Hemodynamic, Anatomical, and Electromechanical Ventricular Interdependence in Patients with Pulmonary Arterial Hypertension

The objective of this study was to determine the factors independently associated with septal curvature in patients with pulmonary arterial hypertension (PAH).

Experimental models of right heart failure: a window for translational research in pulmonary hypertension.

The right ventricle (RV) faces major changes in loading conditions associated with cardiovascular and pulmonary vascular disorders. Despite major pharmacological advances since the last decade, pulmonary arterial hypertension remains a deadly disease mainly secondary to the development of right ventricular failure (RVF). Several experimental models of RVF have been developed over the past three decades providing a particular insight in RV pathophysiology. Mechanisms involved in the transition from RV adaptive hypertrophy to maladaptive remodeling and failure in conditions of chronic RV pressure or volume overload are of a great interest but not yet completely understood. Further investigations are needed to find new therapeutic approaches for RVF. Current animal models and emerging concepts of translational RV research will be detailed in this review.

Advancing knowledge of right ventricular pathophysiology in chronic pressure overload: Insights from experimental studies.

The right ventricle (RV) has to face major changes in loading conditions due to cardiovascular diseases and pulmonary vascular disorders. Clinical experience supports evidence that the RV better compensates for volume than for pressure overload, and for chronic than for acute changes. For a long time, right ventricular (RV) pathophysiology has been restricted to patterns extrapolated from left heart studies. However, the two ventricles are anatomically, haemodynamically and functionally distinct. RV metabolic properties may also result in a different behaviour in response to pathological conditions compared with the left ventricle. In this review, current knowledge of RV pathophysiology is reported in the setting of chronic pressure overload, including recent experimental findings and emerging concepts. After a time-varying compensated period with preserved cardiac output despite overload conditions, RV failure finally occurs, leading to death. The underlying mechanisms involved in the transition from compensatory hypertrophy to maladaptive remodelling are not completely understood.

Pulmonary microvascular lesions regress in reperfused chronic thromboembolic pulmonary hypertension

BACKGROUND Pulmonary microvascular disease (PMD) develops in both occluded and non-occluded territories in patients with chronic thromboembolic pulmonary hypertension (CTEPH) and may cause persistent pulmonary hypertension after pulmonary endarterectomy. Endothelin-1 (ET-1) and interleukin-6 (IL-6) are potential PMD severity biomarkers, but it remains unknown whether they are related to occluded or non-occluded territories. We assessed PMD and ET-1/IL-6 gene expression profiles in occluded and non-occluded territories with and without chronic lung reperfusion in an animal CTEPH model. METHODS Chronic PH was induced in 10 piglets by left pulmonary artery (PA) ligation followed by weekly embolization of right lower lobe arteries with enbucrilate tissue adhesive for 5 weeks. At Week 6, 5 of 10 animals underwent left PA reperfusion. At Week 12, animals with and without reperfusion were compared with sham animals (n = 5). Hemodynamics, lung morphometry and ET-1/IL-6 gene expression profiles were assessed in the left lung (LL, occluded territories) and right upper lobe (RUL, non-occluded territories). RESULTS At Week 12, mean PA pressure remained elevated without reperfusion (29.0 ± 2.8 vs 27.0 ± 1.1 mm Hg, p = 0.502), but decreased after reperfusion (30.0 ± 1.5 vs 20.5 ± 1.7 mm Hg, p = 0.013). Distal media thickness in the LL and RUL PAs and systemic vasculature to the LL were significantly lower in the reperfused and sham groups compared with the non-reperfused group. PMD progression was related to ET-1 and IL-6 gene expression in the RUL and to the ET-A/ET-B gene expression ratio in the LL. CONCLUSIONS PMD regressed in occluded and non-occluded territories after lung reperfusion. Changes in ET-1 and IL-6 gene expression were associated with PMD in non-occluded territories.

Right ventricular reserve in a piglet model of chronic pulmonary hypertension

Right ventricular (RV) response to exercise or pharmacological stress is not well documented in pulmonary hypertension (PH). We investigated the relationship between RV reserve and ventricular–arterial coupling. Surgical ligation of the left pulmonary artery was performed in 13 Large White piglets (PH group), thereafter weekly embolisations of the right lower lobe were performed for 5 weeks. A control group of six piglets underwent sham procedures. Right heart catheterisation and echocardiography were performed at week 6. Pressure–volume loops were recorded before and after dobutamine infusion. Induction of experimental PH resulted in a higher mean±sd pulmonary artery pressure (34±9 versus 14±2 mmHg; p<0.01) and in a lower ventricular–arterial coupling efficiency (0.66±0.18 versus 1.24±0.17; p<0.01) compared with controls at 6 weeks. Dobutamine-induced relative changes in RV stroke volume index (SVI) and end-systolic elastance were lower in the PH group (mean±sd 47±5% versus 20±5%, p<0.01, and 81±37% versus 32±14%, p<0.01, respectively). Change in SVI was strongly associated with resting ventricular–arterial coupling (R2=0.74; p<0.01). RV reserve was associated with ventricular–arterial coupling in a porcine model of chronic pressure overload. Dobutamine testing in right ventricular pressure overload: a potentially useful method to assess contractile reserve http://ow.ly/E9NMK

Right ventricular plasticity in a porcine model of chronic pressure overload.

BACKGROUND Ventricular-arterial coupling is a measure of the relationship between ventricular contractility and afterload. We sought to determine the relationship between ventricular-arterial coupling and right ventricular (RV) remodeling in a novel porcine model of progressive pulmonary hypertension (PH). METHODS Chronic PH was induced in pigs by ligation of the left pulmonary artery (PA) followed by 5 weekly injections of cyanoacrylate to progressively obstruct the right lower lobe arteries (PH group, n = 10). At 6 weeks, 5 PH animals underwent reperfusion of the left lung through conduit anastomosis to decrease RV afterload, whereas 5 other animals received no treatment. Five sham-operated piglets were used as controls. RV function was assessed using echocardiography and conductance catheterization. RV gene expression of beta-myosin heavy chain (β-MHC) and B-type natriuretic peptide (BNP) were quantified by polymerase chain reaction. RESULTS At 6 weeks, compared with controls, the PH group had higher mean PA pressure (32 ± 6 vs 14 ± 2 mm Hg, p < 0.01). The increase in RV elastance was insufficient to compensate for the increase in pulmonary arterial elastance in the PH group and altered ventricular-arterial coupling occurred (0.65 ± 0.16 vs 1.28 ± 0.14, p < 0.01). The degree of ventricular-arterial uncoupling was related to RV enlargement and systolic dysfunction. Ventricular-arterial uncoupling and increased RV mass index were associated with up-regulation of β-MHC and BNP expression. CONCLUSIONS Ventricular-arterial coupling is closely associated with ventricular remodeling and systolic function as well as contractile and BNP gene expression. Dynamic changes in myosin expression may determine RV work efficiency in PH.

The Right Heart in Congenital Heart Disease, Mechanisms and Recent Advances

In patients with congenital heart disease, the right heart may support the pulmonary or the systemic circulation. Several congenital heart diseases primarily affect the right heart including Tetralogy of Fallot, transposition of great arteries, septal defects leading to pulmonary vascular disease, Ebstein anomaly and arrhythmogenic right ventricular cardiomyopathy. In these patients, right ventricular dysfunction leads to considerable morbidity and mortality. In this paper, our objective is to review the mechanisms and management of right heart failure associated with congenital heart disease. We will outline pearls and pitfalls in the management of congenital heart disease affecting the right heart and highlight recent advances in the field.

Load Adaptability in Patients With Pulmonary Arterial Hypertension

Right ventricular (RV) adaptation to pressure overload is a major prognostic factor in patients with pulmonary arterial hypertension (PAH). The objectives were first to define the relation between RV adaptation and load using allometric modeling, then to compare the prognostic value of different indices of load adaptability in PAH. Both a derivation (n = 85) and a validation cohort (n = 200) were included. Load adaptability was assessed using 3 approaches: (1) surrogates of ventriculo-arterial coupling (e.g., RV area change/end-systolic area), (2) simple ratio of function and load (e.g., tricuspid annular plane systolic excursion/right ventricular systolic pressure), and (3) indices assessing the proportionality of adaptation using allometric pressure-function or size modeling. Proportional hazard modeling was used to compare the hazard ratio for the outcome of death or lung transplantation. The mean age of the derivation cohort was 44 ± 11 years, with 80% female and 74% in New York Heart Association class III or IV. Mean pulmonary vascular resistance index (PVRI) was 24 ± 11 with a wide distribution (1.6 to 57.5 WU/m2). Allometric relations were observed between PVRI and RV fractional area change (R2 = 0.53, p < 0.001) and RV end-systolic area indexed to body surface area right ventricular end-systolic area index (RVESAI) (R2 = 0.29, p < 0.001), allowing the derivation of simple ratiometric load-specific indices of RV adaptation. In right heart parameters, RVESAI was the strongest predictor of outcomes (hazard ratio per SD = 1.93, 95% confidence interval 1.37 to 2.75, p < 0.001). Although RVESAI/PVRI0.35 provided small incremental discrimination on multivariate modeling, none of the load-adaptability indices provided stronger discrimination of outcome than simple RV adaptation metrics in either the derivation or the validation cohort. In conclusion, allometric modeling enables quantification of the proportionality of RV load adaptation but offers small incremental prognostic value to RV end-systolic dimension in PAH.

Chronic Thromboembolic Pulmonary Hypertension and Assessment of Right Ventricular Function in the Piglet.

An original piglet model of Chronic Thromboembolic Pulmonary Hypertension (CTEPH) associated with chronic Right Ventricular (RV) dysfunction is described. Pulmonary Hypertension (PH) was induced in 3-week-old piglets by a progressive obstruction of the pulmonary vascular bed. A ligation of the left Pulmonary Artery (PA) was performed first through a mini-thoracotomy. Second, weekly embolizations of the right lower pulmonary lobe were done under fluoroscopic guidance with n-butyl-2-cyanoacrylate during 5 weeks. Mean Pulmonary Arterial Pressure (mPAP) measured by ritght heart catheterism, increased progressively, as well as Right Atrial pressure and Pulmonary Vascular Resistances (PVR) after 5 weeks compared to sham animals. Right Ventricular (RV) structural and functional remodeling were assessed by transthoracic echocardiography (RV diameters, RV wall thickness, RV systolic function). RV elastance and RV-pulmonary coupling were assessed by Pressure-Volume Loops (PVL) analysis with conductance method. Histologic study of the lung and the right ventricle were also performed. Molecular analyses on RV fresh tissues could be performed through repeated transcutaneous endomyocardial biopsies. Pulmonary microvascular disease in obstructed and unobstructed territories was studied from lung biopsies using molecular analyses and pathology. Furthermore, the reliability and the reproducibility was associated with a range of PH severity in animals. Most aspects of the human CTEPH disease were reproduced in this model, which allows new perspectives for the understanding of the underlying mechanisms (mitochondria, inflammation) and new therapeutic approaches (targeted, cellular or gene therapies) of the overloaded right ventricle but also pulmonary microvascular disease.