EXPRESS: Surfing the Right Ventricular Pressure Waveform: Methods to assess Global, Systolic and Diastolic RV Function from a Clinical Right Heart Catheterization

Longitudinal Validation of Right Ventricular Pressure Monitoring for the Assessment of Right Ventricular Systolic Dysfunction in a Large Animal Ischemic Model

Right ventricular (RV) dysfunction is a major cause of morbidity and mortality in intensive care and cardiac surgery. Early detection of RV dysfunction may be facilitated by continuous monitoring of RV waveform obtained from a pulmonary artery catheter. The objective is to evaluate the extent to which RV pressure monitoring can detect changes in RV systolic performance assess by RV end-systolic elastance (E_es) following the development of an acute RV ischemic in a porcine model.

HYPOTHESIS

RV pressure monitoring can detect changes in RV systolic performance assess by RV E_es following the development of an acute RV ischemic model.

METHODS AND MODELS

Acute ischemic RV dysfunction was induced by progressive embolization of microsphere in the right coronary artery to mimic RV dysfunction clinically experienced during cardiopulmonary bypass separation caused by air microemboli. RV hemodynamic performance was assessed using RV pressure waveform-derived parameters and RV E_es obtained using a conductance catheter during inferior vena cava occlusions.

RESULTS

Acute ischemia resulted in a significant reduction in RV E_es from 0.26 mm Hg/mL (interquartile range, 0.16-0.32 mm Hg/mL) to 0.14 mm Hg/mL (0.11-0.19 mm Hg/mL; p < 0.010), cardiac output from 6.3 L/min (5.7-7 L/min) to 4.5 (3.9-5.2 L/min; p = 0.007), mean systemic arterial pressure from 72 mm Hg (66-74 mm Hg) to 51 mm Hg (46-56 mm Hg; p < 0.001), and mixed venous oxygen saturation from 65% (57-72%) to 41% (35-45%; p < 0.001). Linear mixed-effect model analysis was used to assess the relationship between E_es and RV pressure-derived parameters. The reduction in RV E_es best correlated with a reduction in RV maximum first derivative of pressure during isovolumetric contraction (dP/dt_max) and single-beat RV E_es. Adjusting RV dP/dt_max for heart rate resulted in an improved surrogate of RV E_es.

INTERPRETATION AND CONCLUSIONS

Stepwise decreases in RV E_es during acute ischemic RV dysfunction were accurately tracked by RV dP/dt_max derived from the RV pressure waveform.

Pressure-based beat-to-beat right ventricular ejection fraction and Tau from continuous measured ventricular pressures in COVID-19 ARDS patients

We evaluated pressure-based right ventricular ejection fraction (RVEF) and diastolic isovolumetric relaxation time constant (Tau) from continuously (up to 30 days) invasive measured right ventricular pressures in mechanically ventilated patients with severe COVID-19 acute respiratory distress syndrome (ARDS). We retrospectively calculated beat-to-beat ejection fraction from right ventricular pressures and dp/dt maximum and minimum in 39 patients treated between October 1st, 2020 and June 30th, 2021. After performing a stepwise logistic regression with survival as a dependent variable, we divided the patients into survivors and nonsurvivors based on their 60-day mortality. Independent outcome variables were the values of RVEF and Tau over time after insertion of the right ventricular probe along with right ventricular systolic and diastolic pressures (RVSP) and the estimated pulmonary artery diastolic pressure (ePAD). RVEF increased significantly over time in the survivors (estimate: 0.354; 95% confidence interval, CI: 0.18-0.53; p < 0.001) but remained unchanged in the nonsurvivors. Tau increased significantly in the nonsurvivors (estimate: 0.001; 95% CI: 0.0004-0.0018; p < 0.002) but not in the survivors. On the last measurement day, RVSP and ePAD were significantly lower while RVEF was significantly higher in the survivors compared to the nonsurvivors. In COVID-19 ARDS patient's, calculation of beat-to-beat RVEF and Tau from continuously invasive measured right ventricular pressures seems to unravel contrary trends in RVEF with an increase in the surviving and a decrease in the nonsurviving patients. Tau remained unchanged in the surviving but increased in the nonsurviving patients over time.

Right ventricular-pulmonary artery coupling in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension occurs in a proportion of patients with prior acute pulmonary embolism and is characterised by breathlessness, persistently raised pulmonary pressures and right heart failure. Surgical pulmonary endarterectomy (PEA) offers significant prognostic and symptomatic benefits for patients with proximal disease distribution. For those with inoperable disease, management options include balloon pulmonary angioplasty (BPA) and medical therapy. Current clinical practice relies on the evaluation of pulmonary haemodynamics to assess disease severity, timing of and response to treatment. However, pulmonary haemodynamics correlate poorly with patient symptoms, which are influenced by right ventricular tolerance of the increased afterload. How best to manage symptomatic patients with chronic thromboembolic pulmonary disease (CTEPD) in the absence of pulmonary hypertension is not resolved.Right ventricular-pulmonary artery coupling (RV-PAC) describes the energy transfer within the whole cardiopulmonary unit. Thus, it can identify the earliest signs of decompensation even before pulmonary hypertension is overt. Invasive measurement of coupling using pressure volume loop technology is well established in research settings. The development of efficient and less invasive measurement methods has revived interest in coupling as a viable clinical tool. Significant improvement in RV-PAC has been demonstrated after both PEA and BPA. Further studies are required to understand its clinical utility and prognostic value, in particular, its potential to guide management in patients with CTEPD. Finally, given the reported differences in coupling between sexes in pulmonary arterial hypertension, further work is required to understand the applicability of proposed thresholds for decoupling in therapeutic decision making.

Elucidating tricuspid Doppler signal interpolation and its implication for assessing pulmonary hypertension

Doppler echocardiography plays a central role in the assessment of pulmonary hypertension (PAH). We aim to improve quality assessment of systolic pulmonary arterial pressure (SPAP) by applying a cubic polynomial interpolation to digitized tricuspid regurgitation (TR) waveforms. Patients with PAH and advanced lung disease were divided into three cohorts: a derivation cohort (n = 44), a validation cohort (n = 71), an outlier cohort (n = 26), and a non-PAH cohort (n = 44). We digitized TR waveforms and analyzed normalized duration, skewness, kurtosis, and first and second derivatives of pressure. Cubic polynomial interpolation was applied to three physiology-driven phases: the isovolumic phase, ejection phase, and "shoulder" point phase. Coefficients of determination and a Bland-Altman analysis was used to assess bias between methods. The cubic polynomial interpolation of the TR waveform correlated strongly with expert read right ventricular systolic pressure (RVSP) with R 2 > 0.910 in the validation cohort. The biases when compared to invasive SPAP measured within 24 h were 6.03 [4.33; 7.73], -2.94 [1.47; 4.41], and -3.11 [-4.52; -1.71] mmHg, for isovolumic, ejection, and shoulder point interpolations, respectively. In the outlier cohort with more than 30% difference between echocardiographic estimates and invasive SPAP, cubic polynomial interpolation significantly reduced underestimation of RVSP. Cubic polynomial interpolation of the TR waveform based on isovolumic or early ejection phase may improve RVSP estimates.

The Right Ventricular-Pulmonary Arterial Coupling and Diastolic Function Response to Therapy in Pulmonary Arterial Hypertension

BACKGROUND

Multiparametric risk assessment is used in pulmonary arterial hypertension (PAH) to target therapy. However, this strategy is imperfect as most patients remain in intermediate or high risk after initial treatment with low risk being the goal. Metrics of right ventricular (RV) adaptation are promising tools that may help refine our therapeutic strategy.

RESEARCH QUESTION

Does RV adaptation predict therapeutic response over time?

STUDY DESIGN AND METHODS

We evaluated 52 incident treatment naïve patients with advanced PAH by catheterization and cardiac imaging longitudinally at baseline, follow-up 1 (∼3 mo.) and follow-up 2 (∼18 mo.). All patients were placed on goal-directed therapy with parenteral treprostinil and/or combination therapy with treatment escalation if functional class I-II was not achieved. Therapeutic response was evaluated at follow-up 1 as non-responders (died) or responders and again at follow-up 2 as super-responders (low risk) or partial-responders (high/intermediate risk). Multiparametric risk was based on a simplified ERS/ESC guideline score. RV adaptation was evaluated with the single-beat coupling ratio (Ees/Ea) and diastolic function with diastolic elastance (Eed). Data are expressed as mean±SD or odds ratio [95%CI].

RESULTS

Nine patients (17%) were non-responders. PAH-directed therapy improved ERS low risk from 1 (2%) at baseline to 23 (55%) at follow-up 2. Ees/Ea at presentation was non-significantly higher in responders (0.9±0.4) versus non-responders (0.6±0.4, p=0.09) but was unable to predict super-responder status at follow-up 2 (odds ratio 1.40 [0.28-7.0], p=0.84). Baseline RVEF and change in Eed successfully predicted super-responder status at follow-up 2 (odds ratio 1.15 [1.0-1.27], p=0.009 and 0.29 [0.86-0.96], p=0.04, respectively).

INTERPRETATION

In patients with advanced PAH, RV-PA coupling could not discriminate irreversible RV failure (non-responders) at presentation but showed a late trend to improvement by follow-up 2. Early change in Eed and baseline RVEF were the best predictors of therapeutic response.

Current Understanding of the Right Ventricle Structure and Function in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a disease resulting in increased right ventricular (RV) afterload and RV remodeling. PAH results in altered RV structure and function at different scales from organ-level hemodynamics to tissue-level biomechanical properties, fiber-level architecture, and cardiomyocyte-level contractility. Biomechanical analysis of RV pathophysiology has drawn significant attention over the past years and recent work has found a close link between RV biomechanics and physiological function. Building upon previously developed techniques, biomechanical studies have employed multi-scale analysis frameworks to investigate the underlying mechanisms of RV remodeling in PAH and effects of potential therapeutic interventions on these mechanisms. In this review, we discuss the current understanding of RV structure and function in PAH, highlighting the findings from recent studies on the biomechanics of RV remodeling at organ, tissue, fiber, and cellular levels. Recent progress in understanding the underlying mechanisms of RV remodeling in PAH, and effects of potential therapeutics, will be highlighted from a biomechanical perspective. The clinical relevance of RV biomechanics in PAH will be discussed, followed by addressing the current knowledge gaps and providing suggested directions for future research.

A novel non-invasive and echocardiography-derived method for quantification of right ventricular pressure-volume loops

AIMS

We sought to assess the feasibility of constructing right ventricular (RV) pressure-volume (PV) loops solely by echocardiography.

METHODS AND RESULTS

We performed RV conductance and pressure wire (PW) catheterization with simultaneous echocardiography in 35 patients with pulmonary hypertension. To generate echocardiographic PV loops, a reference RV pressure curve was constructed using pooled PW data from the first 20 patients (initial cohort). Individual pressure curves were then generated by adjusting the reference curve according to RV isovolumic and ejection phase duration and estimated RV systolic pressure. The pressure curves were synchronized with echocardiographic volume curves. We validated the reference curve in the remaining 15 patients (validation cohort). Methods were compared with correlation and Bland-Altman analysis. In the initial cohort, echocardiographic and conductance-derived PV loop parameters were significantly correlated {rho = 0.8053 [end-systolic elastance (Ees)], 0.8261 [Ees/arterial elastance (Ea)], and 0.697 (stroke work); all P < 0.001}, with low bias [-0.016 mmHg/mL (Ees), 0.1225 (Ees/Ea), and -39.0 mmHg mL (stroke work)] and acceptable limits of agreement. Echocardiographic and PW-derived Ees were also tightly correlated, with low bias (-0.009 mmHg/mL) and small limits of agreement. Echocardiographic and conductance-derived Ees, Ees/Ea, and stroke work were also tightly correlated in the validation cohort (rho = 0.9014, 0.9812, and 0.9491, respectively; all P < 0.001), with low bias (0.0173 mmHg/mL, 0.0153, and 255.1 mmHg mL, respectively) and acceptable limits.

CONCLUSION

The novel echocardiographic method is an acceptable alternative to invasively measured PV loops to assess contractility, RV-arterial coupling, and RV myocardial work. Further validation is warranted.

Right ventricular load and contractility in HIV-associated pulmonary hypertension

Background

People living with human immunodeficiency virus (PLWH) are at risk of developing pulmonary hypertension (PH) and right ventricular (RV) dysfunction, but understanding of the relationship of RV function to afterload (RV-PA coupling) is limited. We evaluated the clinical and hemodynamic characteristics of human immunodeficiency virus (HIV)-associated PH.

Methods

We performed a retrospective review of patients with a diagnosis of HIV undergoing right heart catheterization (RHC) from 2000–2016 in a tertiary care center. Inclusion criteria were diagnosis of HIV, age ≥ 18 years and availability of RHC data. PH was classified as either pulmonary arterial hypertension (PAH; mean pulmonary arterial pressure [mPAP] ≥ 25mmHg with pulmonary artery wedge pressure [PAWP] ≤ 15mmHg) or pulmonary venous hypertension (PVH; mPAP ≥ 25mmHg with PAWP > 15). We collected demographics, CD4 cell count, HIV viral load, RHC and echocardiographic data. The single beat method was used to calculate RV-PA coupling from RHC.

Results

Sixty-two PLWH with a clinical likelihood for PH underwent RHC. Thirty-two (52%) met PH criteria (15 with PAH, 17 with PVH). Average time from diagnosis of HIV to diagnosis of PH was 11 years. Eleven of 15 individuals with PAH were on antiretroviral therapy (ART) while all 17 patients with PVH were on ART. Compared to PLWH without PH, those with PH had an increased likelihood of having a detectable HIV viral load and lower CD4 cell counts. PLWH with PAH or PVH had increased RV afterload with normal RV contractility, and preserved RV-PA coupling.

Conclusion

PLWH with PH (PAH or PVH) were more likely to have a detectable HIV viral load and lower CD4 count at the time of RHC. PLWH with PAH or PVH had increased RV afterload, normal RV contractility, with preserved RV-PA coupling suggestive of an early onset, mild, and compensated form of PH. These results should be confirmed in larger studies.

Mechanics of right ventricular dysfunction in pulmonary arterial hypertension and heart failure with preserved ejection fraction

Right ventricular (RV) dysfunction is the most important determinant of survival in patients with pulmonary hypertension (PH). The manifestations of RV dysfunction not only include changes in global RV systolic function but also abnormalities in the pattern of contraction and synchrony. The effects of PH on the right ventricle have been mainly studied in patients with pulmonary arterial hypertension (PAH). However, with the demographic shift towards an aging population, heart failure with preserved ejection fraction (HFpEF) has become an important etiology of PH in recent years. There are significant differences in RV mechanics, function and adaptation between patients with PAH and HFpEF (with or without PH), which are related to different patterns of remodeling and dysfunction. Due to the unique features of the RV chamber, its connection with the main pulmonary artery and the pulmonary circulation, an understanding of the mechanics of RV function and its clinical significance is mandatory for both entities. In this review, we describe the mechanics of the pressure overloaded right ventricle. We review the different mechanical components of RV dysfunction and ventricular dyssynchrony, followed by insights via analysis of pressure-volume loop, energetics and novel blood flow patterns, such as vortex imaging. We conduct an in-depth comparison of prevalence and characteristics of RV dysfunction in HFpEF and PAH, and summarize key outcome studies. Finally, we provide a perspective on needed and expected future work in the field of RV mechanics.

Right ventricular function correlates of right atrial strain in pulmonary hypertension: a combined cardiac magnetic resonance and conductance catheter study

The functional relevance of right atrial (RA) function in pulmonary hypertension (PH) remains incompletely understood. The purpose of this study was to explore the correlation of cardiac magnetic resonance (CMR) feature tracking-derived RA phasic function with invasively measured pressure-volume (P-V) loop-derived right ventricular (RV) end-diastolic elastance ( Eed) and RV-arterial coupling [ratio of end-systolic elastance to arterial elastance ( Ees/ Ea)]. In 54 patients with severe PH, CMR was performed within 24 h of diagnostic right heart catheterization and P-V measurements. RA phasic function was assessed by CMR imaging of RA reservoir, passive, and active strain. The association of RA phasic function with indexes of RV function was evaluated by Spearman’s rank correlation and linear regression analyses. Median [interquartile range] RA reservoir strain, passive strain, and active strain were 19.5% [11.0–24.5], 7.0% [4.0–12.0], and 13.0% [7.0–18.5], respectively. Ees/ Ea was 0.73 [0.48–1.08], and Eed was 0.14 mmHg/mL [0.05–0.22]. RV diastolic impairment [RV end-diastolic pressure (EDP) and Eed] was correlated with RA phasic function, but Ea and Ees were not. In addition, RA phasic function was correlated with inferior vena cava diameter. In multivariate linear regression analysis, adjusting for key P-V loop indexes, Eed and EDP remained significantly associated with RA phasic function. We conclude that RA phasic function is altered in relation to impaired diastolic function of the chronically overloaded right ventricle and contributes to backward venous flow and systemic congestion. These results call for more attention to RA function in the management of patients with PH.

NEW & NOTEWORTHY There is growing awareness of the importance of the right atrial (RA)-right ventricular (RV) axis in pulmonary hypertension (PH). Our results uncover alterations in RA phasic function that are related to depressed RV lusitropic function and contribute to backward venous return and systemic congestion in chronic RV overload. Assessment of RA function should be part of the management and follow-up of patients with PH.

Impaired right ventricular lusitropy is associated with ventilatory inefficiency in pulmonary arterial hypertension

Cardiopulmonary exercise testing (CPET) is an important tool for assessing functional capacity and prognosis in pulmonary arterial hypertension (PAH). However, the associations of CPET parameters with the adaptation of right ventricular (RV) function to afterload remain incompletely understood.In this study, 37 patients with PAH (idiopathic in 31 cases) underwent single-beat pressure-volume loop measurements of RV end-systolic elastance (Ees), arterial elastance (Ea) and diastolic elastance (Eed). Pulmonary arterial stiffness was assessed by magnetic resonance imaging. The results were correlated to CPET variables. The predictive relevance of RV function parameters for clinically relevant ventilatory inefficiency, defined as minute ventilation/carbon dioxide production (V' _E/V' _CO2 ) slope >48, was evaluated using logistic regression analysis.The median (interquartile range) of the V' _E/V' _CO2 slope was 42 (32-52) and the V' _E/V' _CO2 nadir was 40 (31-44). The mean±sd of peak end-tidal carbon dioxide tension (P _ETCO2 ) was 23±8 mmHg. Ea, Eed and parameters reflecting pulmonary arterial stiffness (capacitance and distensibility) correlated with the V' _E/V' _CO2 slope, V' _E/V' _CO2 nadir, P _ETCO2 and peak oxygen pulse. RV Ees and RV-arterial coupling as assessed by the Ees/Ea ratio showed no correlations with CPET parameters. Ea (univariate OR 7.28, 95% CI 1.20-44.04) and Eed (univariate OR 2.21, 95% CI 0.93-5.26) were significantly associated with ventilatory inefficiency (p<0.10).Our data suggest that impaired RV lusitropy and increased afterload are associated with ventilatory inefficiency in PAH.

Validation of the Tricuspid Annular Plane Systolic Excursion/Systolic Pulmonary Artery Pressure Ratio for the Assessment of Right Ventricular-Arterial Coupling in Severe Pulmonary Hypertension

BACKGROUND

The ratios of tricuspid annular plane systolic excursion (TAPSE)/echocardiographically measured systolic pulmonary artery pressure (PASP), fractional area change/invasively measured mean pulmonary artery pressure, right ventricular (RV) area change/end-systolic area, TAPSE/pulmonary artery acceleration time, and stroke volume/end-systolic area have been proposed as surrogates of RV-arterial coupling. The relationship of these surrogates with the gold standard measure of RV-arterial coupling (invasive pressure-volume loop-derived end-systolic/arterial elastance [Ees/Ea] ratio) and RV diastolic stiffness (end-diastolic elastance) in pulmonary hypertension remains incompletely understood. We evaluated the relationship of these surrogates with invasive pressure-volume loop-derived Ees/Ea and end-diastolic elastance in pulmonary hypertension.

METHODS

We performed right heart echocardiography and cardiac magnetic resonance imaging 1 day before invasive measurement of pulmonary hemodynamics and single-beat RV pressure-volume loops in 52 patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. The relationships of the proposed surrogates with Ees/Ea and end-diastolic elastance were evaluated by Spearman correlation, multivariate logistic regression, and receiver operating characteristic analyses. Associations with prognosis were evaluated by Kaplan-Meier analysis.

RESULTS

TAPSE/PASP, fractional area change/mean pulmonary artery pressure, RV area change/end-systolic area, and stroke volume/end-systolic area but not TAPSE/pulmonary artery acceleration time were correlated with Ees/Ea and end-diastolic elastance. Of the surrogates, only TAPSE/PASP emerged as an independent predictor of Ees/Ea (multivariate odds ratio: 18.6; 95% CI, 0.8-96.1; P=0.08). In receiver operating characteristic analysis, a TAPSE/PASP cutoff of 0.31 mm/mm Hg (sensitivity: 87.5% and specificity: 75.9%) discriminated RV-arterial uncoupling (Ees/Ea <0.805). Patients with TAPSE/PASP <0.31 mm/mm Hg had a significantly worse prognosis than those with higher TAPSE/PASP.

CONCLUSIONS

Echocardiographically determined TAPSE/PASP is a straightforward noninvasive measure of RV-arterial coupling and is affected by RV diastolic stiffness in severe pulmonary hypertension.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03403868.