Right Ventricular Myocardial Fibrosis Research Articles

Abstract 17226: Role of BMPR2 Mutation in the Development of RV Failure in Rat Experimental Pulmonary Hypertension

Introduction: BMPR2 mutations are the major genetic risk factor for pulmonary arterial hypertension (PAH) and are associated with increased disease severity and worse survival. Although worsening disease severity and prognosis in BMPR2 mutation carriers has been explained by more severe pulmonary vascular disease (PVD), recent reports suggest that BMPR2 mutations affect right ventricular (RV) myocardium and its function independently of PAH. However, mechanism of dysfunctional RV in BMPR2 mutations carriers are unknown.[Hypothesis]Rats with Bmpr2 mutation have impaired RV function independently of PVD compared to wild-type (WT) rats. Methods: Bmpr2 mutant rats were generated by CRISPR/Cas9 genome editing. Monocrotaline (MCT)-PH model was generated in mutant rats and WT littermates and changes in RV function over time with disease progression were assessed by echocardiography and catheterization in rats with (n=23) or without tadalafil treatment (n=88) Results: In untreated setting, there were no significant differences in RV systolic pressure (RVSP) and RV function between the two groups on 21 days after MCT, whereas RV-fractional area change (FAC) and cardiac index (CI), assessed at later disease stage (23 to 25 days), were significantly lower in Bmpr2 mutant rats than in WT (RV-FAC: WT 41.0±8.3 vs Bmpr2 mutant 27.5±11.5%, p<.0001; CI: 413.2±114.0 vs 263.0±92.9ml/min/kg, p<.0001) at comparable RVSP (64.5±11.6 vs 66.7±8.0mmHg) but higher total pulmonary resistance index (TPRI: 0.16±0.06 vs 0.27±0.09mmHg/ml/min/kg, p<.0001). In rats with tadalafil treatment, Bmpr2 mutant rats had significantly lower RV-FAC (34.4±8.2 vs 23.6±5.4%, p<.05) and more severe RV myocardial fibrosis compared to WT littermates despite no significant differences in RVSP (75.4±8.7 vs 71.0±8.2mmHg) and TPRI (0.19±0.06 vs 0.22±0.08mmHg/ml/min/kg) on 30 days after MCT. Conclusion: In untreated setting, RV dysfunction in Bmpr2 mutant was associated with increased afterload due to exacerbation of vascular lesions; rats treated with PDE5i and with prolonged survival had reduced RV function at comparable afterload, indicating the importance of managing RV function under treatment of PAH.

Evaluation of right ventricular diastolic function, systolic function, and circulating galectin-3 concentrations in dogs with pulmonary stenosis.

Cardiovascular diseases with increased right ventricular (RV) afterload induce RV diastolic and systolic dysfunction, and myocardial fibrosis in humans. Studies in dogs with pulmonary stenosis (PS) evaluating RV diastolic function and markers of myocardial fibrosis are lacking. Dogs with PS have echocardiographic evidence of RV diastolic and systolic dysfunction and increased serum concentrations of galectin-3 (Gal-3), a surrogate biomarker for myocardial fibrosis. Forty client-owned dogs (10 controls, 30 with PS). Prospective study. All dogs had systemic blood pressure measurement, serum biochemical analysis, echocardiography, and measurement of serum Gal-3 concentration performed. Variables of RV diastolic function were obtained in 39/40 dogs. Trans-tricuspid flow velocity in early diastole to trans-tricuspid flow velocity in late diastole ratios (RV E/A) were lower (P < .001) in dogs with PS (median, 0.94; range, 0.62-2.04) compared to controls (1.78; 1.17-2.35). Trans-tricuspid flow velocity in early diastole to tricuspid annular myocardial velocity in early diastole ratios (RV E/e') were higher (P < .001) in dogs with PS (11.55; 4.69-28) compared to control (6.21; 5.16-7.21). Variables of RV systolic function were lower in dogs with PS (P = <.001). Serum Gal-3 concentration was higher (P = .002) in dogs with PS (285.1 pg/mL; 94.71-406.97) compared to control dogs (162.83 pg/mL; 52.3-232.82). Dogs with PS have RV diastolic and systolic dysfunction, and increased Gal-3 concentrations. These findings suggest the presence of RV myocardial fibrosis in dogs with PS, which could impact clinical management.

Association of FOXO3A with right ventricular myocardial fibrosis and its detection by speckle-tracking echocardiography in pulmonary hypertension.

Myocardial fibrosis can result in right ventricular (RV) dysfunction, a critical factor in poor clinical outcomes and high mortality rates among patients with pulmonary hypertension (PH). Decreased RV myocardial strain rates have been reported in PH patients. The expression of FOXO3A may play a crucial role in myocardial fibrosis; however, the relationship between myocardial fibrosis, speckle-tracking echocardiography (STE), and the transcription factor FOXO3A remains unclear. This study aimed to explore the relationship between the molecular mechanisms of myocardial fibrosis and noninvasive ultrasound evaluation indices to provide a reliable molecular foundation for the early diagnosis of right heart dysfunction in clinical settings. A progressive right heart failure (RHF) rat model was established through subcutaneous injections of monocrotaline. Rats were divided into baseline, 2-week, 4-week, and 6-week groups based on the disease course. RV structure, function, and myocardial strain were assessed via echocardiography. Myocardial fibrosis severity was determined using PSR staining. The correlation between myocardial strain and RV myocardial fibrosis was analyzed. FOXO3A, collagen I, collagen III, and BNP expressions were tested using western blotting. As the disease progressed, the right ventricle significantly expanded, and the RV fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), RV global longitudinal strain (RVLS global), and RV free wall longitudinal strain (RVLS FW) gradually declined. However, the reductions in RVLS global and RVLS FW occurred earlier than that of RVFAC, TAPSE. Significant correlations were observed between RVLS global, RVLS FW, and collagen deposition. FOXO3A expression gradually decreased with disease progression, while BNP, collagen I, and collagen III expressions gradually increased. Decreases in RVLS global and RVLS FW in RHF rats occurred earlier than RVFAC and were associated with RV myocardial fibrosis. Furthermore, FOXO3A may have a protective role in the process of RV myocardial fibrosis.

Female rats are less prone to clinical heart failure than male rats in a juvenile rat model of right ventricular pressure load.

Sex is increasingly emerging as determinant of right ventricular (RV) adaptation to abnormal loading conditions. It is unknown, however, whether sex-related differences already occur in childhood. Therefore, this study aimed to assess sex differences in a juvenile model of early RV pressure load by pulmonary artery banding (PAB) during transition from pre to postpuberty. Rat pups (n = 57, 3 wk old, 30-45 g) were subjected to PAB or sham surgery. Animals were euthanized either before or after puberty (4 and 8 wk postsurgery, respectively). Male PAB rats demonstrated failure to thrive already after 4 wk, whereas females did not. After 8 wk, female PAB rats showed less clinical symptoms of RV failure than male PAB rats. RV pressure-volume analysis demonstrated increased end-systolic elastance after 4 wk in females only, and a trend toward preserved end-diastolic elastance in female PAB rats compared with males (P = 0.055). Histology showed significantly less RV myocardial fibrosis in female compared with male PAB rats 8 wk after surgery. Myosin heavy chain 7-to-6 ratio switch and calcineurin signaling were less pronounced in female PAB rats compared with males. In this juvenile rat model of RV pressure load, female rats appeared to be less prone to clinical heart failure compared with males. This was driven by increased RV contractility before puberty, and better preservation of diastolic function with less RV myocardial fibrosis after puberty. These findings show that RV adaptation to increased loading differs between sexes already before the introduction of pubertal hormones.NEW & NOTEWORTHY In this study, we describe sex differences in our unique weanling rat model of increased RV pressure load by pulmonary artery banding. We are the first to assess temporal sex-related differences in RV adaptation during pubertal development. Female rats show superior RV function and less diastolic dysfunction and fibrosis compared with male rats. These differences are already present before puberty, indicating that the differences in RV adaptation are not only determined by sex hormones.

3-Dimensional Versus 2-Dimensional STE for Right Ventricular Myocardial Fibrosis in Patients With End-Stage Heart Failure

BackgroundLongitudinal strain of the right ventricular (RV) free wall (RVFWLS) assessed by 2-dimensional (2D) speckle-tracking echocardiography (STE) has been recently demonstrated to correlate with the extent of RV myocardial fibrosis (MF). However, the value of 3-dimensional (3D) STE–derived strain parameters in predicting RV MF has not been investigated in patients with end-stage heart failure (HF). ObjectivesThis study aimed to determine which RV strain parameter assessed by 2D-STE and 3D-STE was the most reliable parameter for predicting RV MF in patients with end-stage HF against histological confirmation of MF. MethodsA total of 105 consecutive patients with end-stage HF undergoing heart transplantation were enrolled in our study. The conventional RV function parameters, 2D-RVFWLS, and 3D-RVFWLS were obtained in these patients. The degree of MF was quantified by Masson trichrome staining in RV myocardial samples. The study population was divided into 3 groups according to the degree of MF on histology. ResultsPatients with severe MF had lower 3D-RVFWLS, 2D-RVFWLS, and conventional parameters of RV function compared with those with mild and moderate MF. RV MF strongly correlated with 3D-RVFWLS (r = −0.72; p < 0.001), modestly with 2D-RVFWLS (r = −0.53; p < 0.001), and weakly with conventional RV function parameters (r = −0.21 to −0.49; p < 0.01). 3D-RVFWLS correlated best with the degree of MF (r = −0.72 vs. −0.21 to −0.53; p < 0.05) compared with 2D-RVFWLS and conventional RV function parameters. 3D-RVFWLS had the highest accuracy for detecting severe MF (area under the receiver-operating characteristic curve: 0.90 vs. 0.24–0.80; p < 0.05) compared with 2D-RVFWLS and conventional RV parameters. The model with 3D-RVFWLS (R2 = 0.63; p < 0.001) was better in predicting the degree of RV MF than that with 2D-RVFWLS (R2 = 0.54; p < 0.001). Conclusions3D-RVFWLS may be the most robust echocardiographic measure for predicting the extent of RV MF in patients with end-stage HF.

Persistent end-diastolic forward flow after pulmonary valve replacement in patients with repaired tetralogy of Fallot.

The clinical significance of persistent end-diastolic forward flow (EDFF) after pulmonary valve replacement (PVR) remains unclear in patients with repaired tetralogy of Fallot. This study aimed to identify the characteristics of these patients and the impact of persistent EDFF on outcomes. Of 46 consecutive patients who underwent PVR for moderate to severe pulmonary regurgitation between 2003 and 2019, 23 (50%) did not show EDFF before PVR [group (-)]. In the remaining 23 patients with EDFF before PVR, EDFF was diminished after PVR in 13 (28%) [group (+, -)] and persisted in 10 (22%) [group (+, +)]. The following variables were compared between these 3 groups: (i) preoperative right ventricular (RV) and right atrial volumes measured by magnetic resonance imaging, haemodynamic parameters measured by cardiac catheterization and the degree of RV myocardial fibrosis measured by RV biopsy obtained at PVR and (ii) the post-PVR course, development of atrial arrhythmia and need for intervention. A high RV end-diastolic pressure, a greater right atrial volume index and a greater RV end-systolic volume index before PVR and a high degree of RV fibrosis were significantly associated with persistent EDFF 1 year after PVR. Persistent EDFF was a significant risk factor for postoperative atrial tachyarrhythmia, and catheter ablation and pacemaker implantation were required more frequently in these patients. Persistent EDFF after PVR could predict a worse prognosis, especially an increased risk of arrhythmia. Close follow-up is required in patients with persistent EDFF for early detection of arrhythmia and prompt reintervention if necessary. Institutional review board of Osaka University Hospital, number 16105.

Diffuse right ventricular fibrosis in heart failure with preserved ejection fraction and pulmonary hypertension

AimsWhile right ventricular (RV) dysfunction is associated with worse prognosis in co‐morbid pulmonary hypertension and heart failure with preserved ejection fraction (PH‐HFpEF), the mechanisms driving RV dysfunction are unclear. We evaluated the extent and clinical correlates of diffuse RV myocardial fibrosis in PH‐HFpEF, as measured by cardiovascular magnetic resonance‐derived extracellular volume (ECV).Methods and resultsWe prospectively enrolled participants with PH‐HFpEF (n = 14), pulmonary arterial hypertension (PAH; n = 13), and controls (n = 8). All participants underwent high‐resolution cardiovascular magnetic resonance, and case subjects (PH‐HFpEF and PAH) additionally underwent right heart catheterization. T1 mapping was performed using high‐resolution modified look‐locker inversion recovery with a 1 × 1 mm2 in‐plane resolution. RV free wall T1 values were quantified, and ECV was calculated. Participants with PH‐HFpEF were older and carried higher rates of hypertension and obstructive sleep apnoea than those with PAH. While RV ECV was similar between PH‐HFpEF and PAH (33.1 ± 8.0 vs. 34.0 ± 4.5%; P = 0.57), total pulmonary resistance was lower in PH‐HFpEF compared with PAH [PH‐HFpEF: 5.68 WU (4.70, 7.66 WU) vs. PAH: 8.59 WU (8.14, 12.57 WU); P = 0.01]. RV ECV in PH‐HFpEF was associated with worse indices of RV structure (RV end‐diastolic volume: r = 0.67, P = 0.01) and RV function (RV free wall strain: r = 0.59, P = 0.03) but was not associated with RV afterload (total pulmonary resistance: r = 0.08, P = 0.79). Conversely, there was a strong correlation between RV ECV and RV afterload in PAH (r = 0.57, P = 0.04).ConclusionsDiffuse RV fibrosis, as measured by ECV, is present in PH‐HFpEF and is associated with adverse RV structural and functional remodelling but not degree of pulmonary vasculopathy. In PH‐HFpEF, diffuse RV fibrosis may occur out of proportion to the degree of RV afterload.

Clinical Predictors of Right Ventricular Myocardial Fibrosis in Patients With Repaired Tetralogy of Fallot.

This study aimed to identify the clinical predictors of the degree of right ventricular (RV) myocardial fibrosis in patients with repaired tetralogy of Fallot (TOF) with special focus on the RV pressure load.Methods and Results:From April 2004 to March 2017, 30 patients with repaired TOF underwent pulmonary valve replacement and concomitant RV myocardial biopsy. The stroke volume ratio (RV stroke volume/left ventricular stroke volume), RV end-diastolic volume index, and right-to-left ventricular systolic pressure ratio were evaluated with respect to their prognostic value for the degree of RV myocardial fibrosis. Significant positive linear correlations were detected between the stroke volume ratio and the degree of RV myocardial fibrosis (P=0.003, r=0.52). Patients with a right-to-left ventricular systolic pressure ratio >0.45 showed a significantly greater degree of RV myocardial fibrosis under an equivalent stroke volume ratio. Under conditions of RV volume overload, a right-to-left ventricular systolic pressure ratio >0.45 was a predisposing factor for progression of RV myocardial fibrosis in patients with repaired TOF.

1574P - Differential regulation of profibrotic genes responsible for cardiotoxicity after experimental anticancer treatments

Transcriptomic analysis of the myocardial samples aimed to search genes responsible for myocardial fibrosis and development of heart failure induced by anticancer therapy under experimental setting. Domestic pigs (38 ± 3 kg) received 3 cycles of cytostatic treatment of human dose with either doxorubicin (DOX, n = 6) or liposomal encapsulation of doxorubicin-citrat complex (Myocet® MYO, n = 9), or epirubicin (EPI, n = 9) or physiologic saline (Controls, CO, n = 6). Left (LV) and right ventricular (RV) ejection fraction (EF) was assessed after the application of the last dose by cardiac magnetic resonance imaging. LV and RV myocardial fibrosis was quantified by picrosorius-red staining. mRNAs of myocardial samples from the LV and RV were isolated. The gene expression profile was analyzed by next generation sequencing (NGS) followed by post-hoc RT-PCR of selected genes. Five, 6 and 2 animals survived the treatment in DOX, MYO and EPI groups, respectively, thus EPI was excluded from the functional analysis. Both MYO and DOX resulted in decrease of LV EF (56.4 ± 5.6% vs 41.9 ± 13.5%, p < 0.05) and RV EF (42.1 ± 2.8% vs 28.9 ± 8.9%, p < 0.05) in MYO vs DOX, resp., with a trend towards less myocardial fibrosis in MYO-treated animals. The cardiac muscle contraction gene myozenin was significantly (p < 0.05) down-regulated in group DOX as compared to group MYO (0.12 ± 0.09 vs 1.13 ± 0.06 log fold changes /LFC/). EMILIN and SERPINH1 genes (both are involved in biosynthetic pathway of collagen and elastin) were significantly overexpressed in LV and RV samples of both DOX and MYO groups. Besides activations of tumor-repressors, both DOX and MYO treatments led to up-regulation of several proto-oncogenes, such as JUNB (LV: 1.68 ± 0.3 and 1.65 ± 0.23; RV:1.71 ± 0.13 and 1.98 ± 0.93 LFC, resp.) or BCL3 (LV: 2.97 ± 0.34 and 2.96 ± 0.79; RV: 6.34 ± 0.61 and 4.81 ± 1.01 LFC, resp.). Myocet® proved to be less cardiotoxic as compared with DOX, resulting in better cardiac function and less fibrosis. However, both cytostatic treatments led to overexpression of collagen-associated genes and proto-oncogenes, which might explain the development of myocardial fibrosis and secondary malignancies.

RV Longitudinal Deformation Correlates With Myocardial Fibrosis in Patients With End-Stage Heart Failure

ObjectivesThis study was performed to determine the accuracy of right ventricular (RV) longitudinal strain (LS) in predicting myocardial fibrosis in patients with severe heart failure (HF) undergoing heart transplantation. BackgroundRVLS plays a key role in the evaluation of its systolic performance and clinical outcome in patients with refractory HF. MethodsWe studied 27 patients with severe systolic HF (ejection fraction ≤25% and New York Heart Association functional class III to IV, despite full medical therapy and cardiac resynchronization therapy) using echocardiography before heart transplantation. RV free wall LS, right atrial LS, sphericity index (SI), and tricuspid annular plane systolic excursion (TAPSE) were all measured. Upon removal of the heart, from the myocardial histologic analysis, the ratio of the fibrotic to the total sample area determined the extent of fibrosis (%). ResultsRV myocardial fibrosis correlated with RV free wall LS (r = 0.80; p < 0.0001), SI (r = 0.42; p = 0.01) and VO2 max (r = –0.41; p = 0.03), with a poor correlation with TAPSE (r = –0.34; p = 0.05) and right atrial LS (r = –0.37; p = 0.03). Stepwise multivariate analysis showed that RV free wall LS (β = 0.701, p < 0.0001) was independently associated with RV fibrosis (overall model R2 = 0.64, p < 0.0001). RV free wall LS was the main determinant of myocardial fibrosis. In the subgroup of patients with severe RV fibrosis, RV free wall LS had the highest diagnostic accuracy for detecting severe myocardial fibrosis (area under the curve = 0.87; 95% confidence interval: 0.80 to 0.94). ConclusionsIn late-stage HF patients, the right ventricle is enlarged, with reduced systolic function due to significant myocardial fibrosis. RV free wall myocardial deformation is the most accurate functional measure that correlates with the extent of RV myocardial fibrosis and functional capacity.

Magnetic Resonance Assessment of Prevalence and Correlates of Right Ventricular Abnormalities in Isolated Left Ventricular Noncompaction

The aim of the present study was to evaluate the prevalence and correlates of right ventricular (RV) noncompaction (RVNC), RV systolic dysfunction, and RV myocardial fibrosis in patients with isolated left ventricular (LV) noncompaction (LVNC). For this purpose, cine and contrast-enhanced cardiac magnetic resonance imaging (MRI) was used. A total of 56 consecutive patients with isolated LVNC were included in the study. The diagnosis of isolated LVNC was based on the presence of standard cardiac MRI and clinical criteria. For each patient, cine and contrast-enhanced cardiac MR images were analyzed to evaluate the prevalence and correlates of RVNC, RV dysfunction, and late gadolinium enhancement (a surrogate of myocardial fibrosis) involving the RV. Mean age of the patient population was 45 ± 19 years; 35 patients (63%) were men. RVNC was observed in 5 patients (9%). Impaired RV systolic function was observed in 9 patients (16%). Late gadolinium enhancement was not observed in any RV segment. No association was found between wall motion abnormalities and noncompaction at RV segmental level (φ coefficient 0.041, p = 0.26). At multivariate analysis, LV ejection fraction was the only variable independently related to RV ejection fraction (β = 0.62, p <0.001). In conclusion, RV systolic dysfunction is present in a non-negligible proportion of patients with isolated LVNC; LV systolic function is the only variable independently related to RV systolic function.

Inhibition of the Ca2+-sensing receptor rescues pulmonary hypertension in rats and mice

A recent study from our group demonstrated that the Ca(2+)-sensing receptor (CaSR) was upregulated, and the extracellular Ca(2+)-induced increase in cytosolic Ca(2+) concentration ([Ca(2+)]cyt) was enhanced in pulmonary arterial smooth muscle cells from patients with idiopathic pulmonary arterial hypertension and animals with experimental pulmonary hypertension (PH). However, it is unclear whether CaSR antagonists (for example, NPS2143) rescue the development of experimental PH. We tested the rescue effects of NPS2143 in rats with monocrotaline (MCT)-induced PH and mice with chronic hypoxia-induced PH. For the NPS2143 treatment group, rats and mice were i.p. injected with NPS2143 once per day from days 14 to 24. Four weeks after MCT injection or exposure to normobaric hypoxia, the right ventricular (RV) systolic pressure, right heart hypertrophy (RV/LV+S ratio) and RV myocardial fibrosis were rescued or nearly restored to normal levels by NPS2143 treatment. The rescue effects of NPS2143 on experimental PH further support a critical role for the CaSR in the PH mechanism. Therefore, NPS2143 may be a promising potential treatment for pulmonary arterial hypertension.