Right Ventricle Functional Assessment: Have New Techniques Supplanted the Old Faithful Conductance Catheter?

Perioperative Right Ventricular Dysfunction and Abnormalities of the Tricuspid Valve Apparatus in Patients Undergoing Cardiac Surgery

Right ventricular (RV) dysfunction frequently occurs after cardiac surgery and is linked to adverse postoperative outcomes, including mortality, reintubation, stroke, and prolonged ICU stays. While various criteria using echocardiography and hemodynamic parameters have been proposed, a consensus remains elusive. Distinctive RV anatomical features include its thin wall, which presents a triangular shape in a lateral view and a crescent shape in a cross-sectional view. Principal causes of RV dysfunction after cardiac surgery encompass ischemic reperfusion injury, prolonged ischemic time, choice of cardioplegia and its administration, cardiopulmonary bypass weaning characteristics, and preoperative risk factors. Post-left ventricular assist device (LVAD) implantation RV dysfunction is common but often transient, with a favorable prognosis upon resolution. There is an ongoing debate regarding the benefits of concomitant surgical repair of the RV in the presence of regurgitation. According to the literature, the gold standard techniques for assessing RV function are cardiac magnetic resonance imaging and hemodynamic assessment using thermodilution. Echocardiography is widely favored for perioperative RV function evaluation due to its accessibility, reproducibility, non-invasiveness, and cost-effectiveness. Although other techniques exist for RV function assessment, they are less common in clinical practice. Clinical management strategies focus on early detection and include intravenous drugs (inotropes and vasodilators), inhalation drugs (pulmonary vasodilators), ventilator strategies, volume management, and mechanical support. Bridging research gaps in this field is crucial to improving clinical outcomes associated with RV dysfunction in the near future.

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.

Right ventricular pressure-volume loop shape and systolic pressure change in pulmonary hypertension

Right ventricular (RV) function determines outcome in pulmonary arterial hypertension (PAH). RV pressure-volume loops, the gold standard for measuring RV function, are difficult to analyze. Our aim was to investigate whether simple assessments of RV pressure-volume loop morphology and RV systolic pressure differential reflect PAH severity and RV function. We analyzed multibeat RV pressure-volume loops (obtained by conductance catheterization with preload reduction) in 77 patients with PAH and 15 patients without pulmonary hypertension in two centers. Patients were categorized according to their pressure-volume loop shape (triangular, quadratic, trapezoid, or notched). RV systolic pressure differential was defined as end-systolic minus beginning-systolic pressure (ESP - BSP), augmentation index as ESP - BSP/pulse pressure, pulmonary arterial capacitance (PAC) as stroke volume/pulse pressure, and RV-arterial coupling as end-systolic/arterial elastance (Ees/Ea). Trapezoid and notched pressure-volume loops were associated with the highest afterload (Ea), augmentation index, pulmonary vascular resistance (PVR), mean pulmonary arterial pressure, stroke work, B-type natriuretic peptide, and the lowest Ees/Ea and PAC. Multivariate linear regression identified Ea, PVR, and stroke work as the main determinants of ESP - BSP. ESP - BSP also significantly correlated with multibeat Ees/Ea (Spearman's ρ: -0.518, P < 0.001). A separate retrospective analysis of 113 patients with PAH showed that ESP - BSP obtained by routine right heart catheterization significantly correlated with a noninvasive surrogate of RV-arterial coupling (tricuspid annular plane systolic excursion/pulmonary arterial systolic pressure ratio; ρ: -0.376, P < 0.001). In conclusion, pressure-volume loop shape and RV systolic pressure differential predominately depend on afterload and PAH severity and reflect RV-arterial coupling in PAH.

Levels of agreement between cardiac magnetic resonance and conductance catheter measurements of right ventricular volumes after pulmonary artery banding

BACKGROUND

Pressure-volume analysis is the gold standard for quantifying pump function of the right ventricle (RV); however, volume measurements based on a conductive catheter may be imprecise. The reference method for volume assessment is cardiac magnetic resonance (CMR).

PURPOSE

To determine the levels of agreement between RV volume measurements obtained by cine CMR, phase-contrast CMR (PC CMR), and a conductance catheter in an animal model.

MATERIAL AND METHODS

CMR was performed in 20 sheep three months after pulmonary artery banding. Ejection fraction (EF), end-diastolic (EDV), end-systolic (ESV), and stroke volumes (SV) were obtained by cine CMR and conductance catheter.

RESULTS

Statistically significant differences between cine CMR and conductance catheter derived volume measurements were found for EDV (P < 0.001), ESV (P < 0.05), and SV (P < 0.05). Bland-Altman analysis showed very poor agreement between the two methods: EDV, bias 36.27 mL, agreement of limits 1.96-70.57 mL; ESV, bias 15.33 mL, agreement of limits -6.89-37.55 mL; and SV, bias 20.69 mL, agreement of limits 8.01-49.10 mL. Good agreement was found for SV between cine CMR and PC CMR (bias -7.0 mL, agreement of limits -24.01-9.98 mL), while SV derived from PC CMR measurements showed poor agreement with conductance catheter (bias 27.76 mL, agreement of limits -3.84-59.26 mL).

CONCLUSION

Poor agreement between the conductance catheter and CMR RV volume measurements was found. PC CMR and cine CMR measurements of SV agreed well.

Assessing Right Ventricular Function in the Perioperative Setting, Part II: What About Catheters?

An-depth assessment of right ventricular function is important in a many perioperative settings. After exploring 2-dimensional echo-based evaluation, other proposed monitoring modalities are discussed. Pressure-based methods of right ventricular appraisal is discussed. Flow-based assessment is reviewed. An overview of the state of current right ventricular 3-dimensional echocardiography and its potential to construct clinical pressure-volume loops in conjunction with pressure measurements is provided. An overview of right ventricular assessment modalities that do not rely on 2-dimensional echocardiography is discussed. Tailored selection of monitoring modalities can be of great benefit for the perioperative physician. Integrating modalities offers optimal estimations of right ventricular function.

Right ventricular function in pulmonary (arterial) hypertension

The right ventricle (RV) is the main determinant of prognosis in pulmonary hypertension. Adaptation and maladaptation of the RV are of crucial importance. In the course of disease, RV contractility increases through changes in muscle properties and muscle hypertrophy. At a certain point, the point of "uncoupling," the afterload exceeds contractility, and maladaptation as well as dilation occurs to maintain stroke volume (SV). To understand the adaptational processes and to further develop targeted medication directly affecting load-independent contractility, an accurate and precise assessment of contractility and RV-pulmonary artery (PA) coupling should be performed. In this review, we shed light on existing methods to assess RV function, including the gold standard measurement of contractility and RV-PA coupling, and we evaluate existing surrogates of RV-PA coupling.

The utility of transthoracic echocardiographic measures of right ventricular systolic function in a lung resection cohort

Right ventricular (RV) dysfunction occurs following lung resection and is associated with post-operative complications and long-term functional morbidity. Accurate peri-operative assessment of RV function would have utility in this population. The difficulties of transthoracic echocardiographic (TTE) assessment of RV function may be compounded following lung resection surgery, and no parameters have been validated in this patient group. This study compares conventional TTE methods for assessing RV systolic function to a reference method in a lung resection population. Right ventricular index of myocardial performance (RIMP), fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE) and S′ wave velocity at the tricuspid annulus (S′), along with speckle tracked global and free wall longitudinal strain (RV-GPLS and RV-FWPLS respectively) are compared with RV ejection fraction obtained by cardiovascular magnetic resonance (RVEF_CMR). Twenty-seven patients undergoing lung resection underwent contemporaneous CMR and TTE imaging; pre-operatively, on post-operative day two and at 2 months. Ability of each of the parameters to predict RV dysfunction (RVEF_CMR <45%) was assessed using the area under the receiver operating characteristic curve (AUROCC). RIMP, FAC and S′ demonstrated no predictive value for poor RV function (AUROCC <0.61, P > 0.05). TAPSE performed marginally better with an AUROCC of 0.65 (P = 0.04). RV-GPLS and RV-FWPLS demonstrated good predictive ability with AUROCC’s of 0.74 and 0.76 respectively (P < 0.01 for both). This study demonstrates that the conventional TTE parameters of RV systolic function are inadequate following lung resection. Longitudinal strain performs better and offers some ability to determine poor RV function in this challenging population.

Three-Dimensional Echocardiography for the Assessment of Right Ventriculo-Arterial Coupling

BACKGROUND

The analysis of right ventriculo-arterial coupling (RVAC) from pressure-volume loops is not routinely performed. RVAC may be approached by the combination of right heart catheterization (RHC) pressure data and cardiac magnetic resonance (CMR)-derived right ventricular (RV) volumetric data. RV pressure and volume measurements by Doppler and three-dimensional echocardiography (3DE) allows another way to approach RVAC.

METHODS

Ninety patients suspected of having pulmonary hypertension underwent RHC, 3DE, and CMR (RHC mean pulmonary artery pressure [mPAP] 37.9 ± 11.3 mm Hg; range, 15-66 mm Hg). Three-dimensional (3D) echocardiography was performed in 30 normal patients (echocardiographic mPAP 18.4 ± 3.1 mm Hg). Pulmonary artery (PA) effective elastance (Ea), RV maximal end-systolic elastance (Emax), and RVAC (PA Ea/RV Emax) were calculated from RHC combined with CMR and from 3DE using simplified formulas including mPAP, stroke volume, and end-systolic volume.

RESULTS

Three-dimensional echocardiographic and RHC-CMR measures for PA Ea (3DE, 1.27 ± 0.94; RHC-CMR, 0.71 ± 0.52; r = 0.806, P < .001), RV Emax (3DE, 0.72 ± 0.37; RHC-CMR, 0.38 ± 0.19; r = 0.798, P < .001), and RVAC (3DE, 2.01 ± 1.28; RHC-CMR, 2.32 ± 1.77; r = 0.826, P < .001) were well correlated despite a systematic overestimation of 3DE elastance parameters. Among the whole population, 3D echocardiographic PA Ea and 3D echocardiographic RVAC but not 3D echocardiographic RV Emax were significantly lower in patients with mPAP < 25 mm Hg (n = 41) than in others (n = 79). Among the 90 patients who underwent RHC, 3D echocardiographic PA Ea and 3D echocardiographic RVAC but not 3D echocardiographic RV Emax increased significantly with increasing levels of pulmonary vascular resistance.

CONCLUSIONS

Three-dimensional echocardiography-derived PA Ea, RV Emax, and RVAC correlated well with the reference RHC-CMR measurements. Ea and RVAC but not Emax were significantly different between patients with different levels of afterload, suggesting failure of the right ventricle to maintain coupling in severe pulmonary hypertension.