Use of noninvasive tools in primary pulmonary hypertension to assess the correlation of right ventricular function with functional capacity and to predict outcome

Correlation Between Right Ventricular Echocardiography Measurements and Functional Capacity in Patients With Pulmonary Arterial Hypertension

BACKGROUND

Accelerometry is an emerging option for real-time evaluation of functional capacity in patients with pulmonary arterial hypertension (PAH). This prospective pilot study assesses the relationship between functional capacity by accelerometry and right ventricular measurements on echocardiography for this high-risk cohort.

METHODS

Patients with PAH were prospectively enrolled and underwent 6-Minute Walk Test and cardiopulmonary exercise testing. They were given a Fitbit, which collected steps and sedentary time per day. Echocardiographic data included right ventricular global longitudinal, free wall, and septal strain; tricuspid regurgitant peak velocity; tricuspid annular plane systolic excursion; tricuspid annular plane systolic velocity; right ventricular myocardial performance index; and pulmonary artery acceleration time. Pairwise correlations were performed.

RESULTS

The final analysis included 22 patients aged 13 to 59 years. Tricuspid regurgitant peak velocity had a negative correlation with 6-Minute Walk Test (r = -0.58, P = .02), peak oxygen consumption on exercise testing (r = -0.56, P = .03), and average daily steps on accelerometry (r = -0.59, P = .03), but a positive correlation with median sedentary time on accelerometry (r = 0.64, P = .02). Pulmonary artery acceleration time positively correlated with peak oxygen consumption on exercise testing (r = 0.64, P = .002). There was no correlation between right ventricular strain measurements and functional capacity testing.

CONCLUSION

In this pilot study, tricuspid regurgitant jet and pulmonary artery acceleration time were the echocardiographic variables that correlated most with accelerometry data. With further echocardiographic validation, accelerometry can be a useful, noninvasive, and cost-effective tool to monitor disease progression in patients with PAH.

Atrial volume and function during exercise in health and disease

BACKGROUND

Although atrial function has prognostic significance in many cardiovascular conditions, changes during exercise have not previously been assessed. The aim of this study was to evaluate left atrial (LA) and right atrial (RA) volume and function during incremental exercise, both in normal individuals, healthy athletes, and in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

Fifteen healthy non-athletes, 15 athletes and 15 CTEPH patients underwent multi-slice real-time cardiovascular magnetic resonance imaging at rest and during supine bicycle exercise with simultaneous invasive hemodynamic measurements.

RESULTS

At rest, athletes had larger indexed maximal RA and LA volumes (iRAVmax, iLAVmax) than CTEPH patients and non-athletes, the latter two groups having similar values. CTEPH patients had lower RA and LA emptying functions (EmF) at rest. During exercise, RA volumes (maximum and minimum) increased in CTEPH patients, whilst decreasing in athletes and non-athletes (P < 0.001). The exercise-induced change in iLAVmax was similar between groups, but iLAVmin did not decrease in CTEPH patients. Thus exercise-induced increases in RAEmF and LAEmF, as seen in normal physiology, were significantly impaired in CTEPH patients. At peak exercise, RA volumes (maximum and minimum) and EmF correlated strongly with RA pressure (R = 0.70; P = 0.005; R = 0.83; P < 0.001; R = -0.87; P < 0.001). On multivariate analysis, peak exercise RAEmF and iLAVmin were independent predictors of VO2peak in CTEPH patients and together explained 72% of the variance in VO2peak (ß =0.581 and ß = -0.515, respectively).

CONCLUSIONS

In normal physiology, RAEmF and LAEmF increase with exercise, whereas CTEPH patients have impaired LAEmF and RAEmF, which becomes more apparent during exercise. Therefore, the changes in atrial volumes and function during exercise enable a far better distinction between physiological and pathological atrial remodeling than resting measures of volumes which are prone to confounding factors (e.g. endurance training). Peak exercise RAEmF is a good marker of poor functional state in CTEPH patients.

Diagnostic and Prognostic Implications of Exercise Treadmill and Rest First-Pass Radionuclide Angiography in Patients With Pulmonary Hypertension

PURPOSE

Pulmonary hypertension (PH) is characterized by abnormally increased pulmonary vascular pressure, leading to deteriorated right ventricular function and premature death. Pulmonary mean transit time (PMTT) and biventricular function response to exercise in first-pass radionuclide angiography (FP-RNA) may provide early detection and timely disease monitoring of PH. This study aimed to investigate the diagnostic and prognostic values of this imaging modality in PH patients.

METHODS

Left and right ventricular ejection fraction (LVEF/RVEF) and PMTT at rest and immediately after exercise treadmill test were measured by FP-RNA in 77 consecutive patients with clinical presentations suggestive of PH (aged 46 ± 15 years, 33 men), mostly with symptoms of unexplained progressive dyspnea. These parameters, along with other clinical variables, were correlated with right-sided heart catheterization data and clinical outcomes.

RESULTS

Fifty patients (64.9%) were diagnosed as having definite PH. Besides higher N-terminal pro-B-type natriuretic peptide levels, right atrial pressure, and pulmonary vascular resistance, PH patients had significantly longer PMTT, lower LVEF after exercise and rest, and lower poststress RVEF (all P < 0.05), compared with non-PH subjects. Moreover, PH patients exhibited stress-induced right ventricular dysfunction and stationary poststress PMTT. Poststress PMTT and echocardiography had comparable diagnostic utility (area under the curve, 0.80 vs 0.84, respectively). Eighteen patients died during a median follow-up period of 380 days. Failure of exercise treadmill test, lower peak heart rate response, and stress/rest LVEF ratio of less than 90% using exercise treadmill FP-RNA were independent predictors of mortality in PH patients.

CONCLUSIONS

Exercise treadmill and rest FP-RNA provided diagnostic value and had prognostic implications in patients with PH.

Comparison of echocardiographic parameters to assess right ventricular function in pulmonary hypertension

Although measurement of right ventricular ejection fraction (RVEF) may be relevant for evaluation of therapeutic efficacy and/or prognosis in patients with pulmonary hypertension, RVEF obtained by echocardiography has limited accuracy. In contrast, radionuclide and/or magnetic resonance imaging can measure RVEF more reliably. In this study, we investigated the relationship between RVEF measured by radionuclide angiography and the echocardiographic parameters that are recommended by the American Society of Echocardiography as representative of right heart function. There were 23 study participants with pulmonary hypertension who underwent radionuclide angiography and 2-dimensional and Doppler echocardiography (n = 30 measurements). RVEF measured by radionuclide angiography correlated with right ventricular Tei index (RV Tei index) measured by Doppler echocardiography (r = -0.601, P < 0.0005). Receiver operating characteristic curve analysis showed that an RV Tei index cut-off value of 0.371 was the best of predictor of RVEF ≤35% (area under the curve = 0.768, sensitivity = 0.857, selectivity = 0.667). Multiple regression analysis showed that RVEF was correlated with the RV Tei index, and this association was independent of other echocardiographic right ventricular function parameters (r = -0.644, P < 0.005). The RV Tei index measured by Doppler echocardiography may be an acceptable surrogate marker of RVEF in patients with pulmonary hypertension.

Non-invasive determination by cardiovascular magnetic resonance of right ventricular-vascular coupling in children and adolescents with pulmonary hypertension

BACKGROUND

Pediatric pulmonary hypertension (PH) remains a disease with high morbidity and mortality in children. Understanding ventricular-vascular coupling, a measure of how well matched the ventricular and vascular function are, may elucidate pathway leading to right heart failure. Ventricular vascular coupling ratio (VVCR), comprised of effective elastance (Ea, index of arterial load) and right ventricular maximal end-systolic elastance (Ees, index of contractility), is conventionally determined by catheterization. Here, we apply a non-invasive approach to determining VVCR in pediatric subjects with PH.

METHODS

This retrospective study included PH subjects who had a cardiovascular magnetic resonance (CMR) study within 14 days of cardiac catheterization. PH was defined as mean pulmonary artery pressure (mPAP) ≥ 25 mmHg on prior or current catheterization. A non-invasive measure of VVCR was derived from CMR-only (VVCRm) and compared to VVCR estimated by catheterization-derived single beat estimation (VVCRs). Indexed pulmonary vascular resistance (PVRi) and pulmonary vascular reactivity were determined during the catheterization procedure. Pearson correlation coefficients were calculated between PVRi and VVCRm. Receiver operating characteristic (ROC) curve analysis determined the diagnostic value of VVCRm in predicting vascular reactivity.

RESULTS

Seventeen subjects (3 months-23 years; mean 11.3 ± 7.4 years) were identified between January 2009-August 2013 for inclusion with equal gender distributions. Mean mPAP was 35 mmHg ± 15 and PVRi was 8.5 Woods unit x m2 ± 7.8. VVCRm (range 0.43-2.82) increased with increasing severity as defined by PVRi (p < 0.001), and was highly correlated with PVRi (r = 0.92, 95 % CI 0.79-0.97, p < 0.0001). Regression of VVCRm and PVRi demonstrated differing lines when separated by reactivity. VVCRm was significantly correlated with VVCRs (r = 0.79, CI 0.48-0.99, p <0.0001). ROC curve analysis showed high accuracy of VVCRm in determining vascular reactivity (VVCR = 0.85 had a sensitivity of 100 % and a specificity of 80 %) with an area under the curve of 0.89 (p = 0.008).

CONCLUSION

Measurement of VVCRm in pediatrics is feasible. Pulmonary vascular non-reactivity may be contribute to ventricular-vascular decoupling in severe PH. Therapeutic intervention to maintain a low vascular afterload in reactive patients may preserve right ventricular functional reserve and delay the onset of RV-PA decoupling. Use of VVCRm may have significant prognostic implication.

The normal impact of age and gender on right heart structure and function

BACKGROUND

As the proportion of elderly population increases rapidly, it might be difficult to differentiate physiological changes in cardiac function due to age from the pathophysiological ones. In addition, cardiac function variations with gender are well established. The right ventricular (RV) plays an important role in the overall cardiac function, but reference values varying with age and gender are lacking.

MATERIAL AND METHODS

We studied 255 healthy individuals from a general population register, mean age of 58 ± 19 (range 22-89) years, 125 were females. We used 2D and M-mode echocardiography to measure RV inflow tract (RVIT) and RV outflow tract (RVOT) dimensions and fractional shortening (fs). Spectral Doppler echocardiography was also used.

RESULTS

We found a modest decrease in RVIT dimensions (P < 0.05), but increase in RVOT dimensions with advancing age (P < 0.05). A small decrease in RVOT fs with age was also found (P < 0.05). Estimated pulmonary pressures and pulmonary vascular resistance increased (P < 0.001) as did RVOT wall thickness (P < 0.001), but RV diastolic function was not altered (P < 0.001) with age. Despite correction for the BSA, males showed larger RVIT dimensions (P < 0.001 for both), but RVOT end-diastolic dimension was larger in females (P < 0.05). RVIT and RVOT fractional shortening were increased in females (P < 0.01 for both).

CONCLUSION

In a cohort of normal individuals, age has significant impact on RV structure and function, inlet area falls and outflow tract dimensions increase and fractional shortening also increase in females. In addition, RVOT wall thickness significantly increases and Doppler markers of pulmonary vascular resistance show a consistent rise. The age-related changes should carefully be considered when commenting on normality and when using absolute values.

Late gadolinium enhancement cardiovascular magnetic resonance predicts clinical worsening in patients with pulmonary hypertension

BACKGROUND

Late gadolinium enhancement (LGE) occurs at the right ventricular (RV) insertion point (RVIP) in patients with pulmonary hypertension (PH) and has been shown to correlate with cardiovascular magnetic resonance (CMR) derived RV indices. However, the prognostic role of RVIP-LGE and other CMR-derived parameters of RV function are not well established. Our aim was to evaluate the predictive value of contrast-enhanced CMR in patients with PH.

METHODS

RV size, ejection fraction (RVEF), and the presence of RVIP-LGE were determined in 58 patients with PH referred for CMR. All patients underwent right heart catheterization, exercise testing, and N-terminal pro-brain natriuretic peptide (NT-proBNP) evaluation; results of which were included in the final analysis if performed within 4 months of the CMR study. Patients were followed for the primary endpoint of time to clinical worsening (death, decompensated right ventricular heart failure, initiation of prostacyclin, or lung transplantation).

RESULTS

Overall, 40/58 (69%) of patients had RVIP-LGE. Patients with RVIP- LGE had larger right ventricular volume index, lower RVEF, and higher mean pulmonary artery pressure (mPAP), all p < 0.05. During the follow-up period of 10.2 ± 6.3 months, 19 patients reached the primary endpoint. In a univariate analysis, RVIP-LGE was a predictor for adverse outcomes (p = 0.026). In a multivariate analysis, CMR-derived RVEF was an independent predictor of clinical worsening (p = 0.036) along with well-established prognostic parameters such as exercise capacity (p = 0.010) and mPAP (p = 0.001).

CONCLUSIONS

The presence of RVIP-LGE in patients with PH is a marker for more advanced disease and poor prognosis. In addition, this study reveals for the first time that CMR-derived RVEF is an independent non-invasive imaging predictor of adverse outcomes in this patient population.

Measuring the heart in pulmonary arterial hypertension (PAH): implications for trial study size

PURPOSE

To calculate the sample size for a theoretical pulmonary arterial hypertension (PAH) randomized controlled trial (RCT) by using cardiovascular magnetic resonance (CMR) imaging to determine the repeatability of measures between two scans.

MATERIALS AND METHODS

Two same-day examinations from 10 PAH patients were analyzed manually and semiautomatically. Study size was calculated from the standard deviation (SD) of repeatability. Different approaches to right-ventricle (RV) mass were investigated, agreement between methods tested and interobserver reproducibility measured by Bland-Altman analysis to explore how the PAH heart might be best measured.

RESULTS

Repeatability was good for almost all manually-measured indices but poor for semiautomated measurement of RV mass and left-ventricle (LV) end-diastolic volume (EDV). Thus, for an RCT (power, 80%; significance level, 5%) analyzing "outcome" indices (RVEDV, LVEDV, RV ejection fraction, and RV mass; anticipated change: 10 mL, 10 mL, 3%, and 10 g, respectively) manually, 34 patients are required compared to 78 if analysis is semiautomated. RV mass was repeatable if the interventricular septum was divided between ventricles or if wholly apportioned to the LV. Limits of agreement between manual and semiautomated analyses were unsatisfactory for RV measures and interobserver reproducibility was worse for semiautomated than manual analysis.

CONCLUSION

Manual is more robust than semiautomated analysis and at present should be favored in RCTs in PAH as it leads to lower sample size requirements.

Impact of right ventricular contrast attenuation on the accuracy of right ventricular function analysis at cardiac multi-detector-row CT

PURPOSE

To investigate the impact of right ventricle (RV) contrast attenuation on the accuracy of RV function analysis at cardiac CT performed for coronary imaging.

MATERIALS AND METHODS

We analyzed multi-phase cardiac dual-source CT studies of 40 consecutive patients (mean age 60.9+/-12.3 years; 13 women) with normal valve function. Function analyses of both the right and left ventricle (RV and LV) were performed using dedicated post processing software and stroke volumes (SV) were computed for each ventricle. The accuracy of the RV-SV measurements was determined based upon comparison to LV-SV measurement. The level of contrast attenuation of the RV was recorded at three separate regions of interest-below the pulmonary valve, mid-ventricular, and inferior RV. The accuracy of RV function assessment was correlated with the level of attenuation using regression analyses.

RESULTS

There was a statistically significant correlation between the accuracy of RV function assessment and the level of RV attenuation in the inferior RV (adjusted R(2)=73.1%, p<0.0001). When compared to LV-SV measurements, in studies with low RV attenuation (<175 HUs, n=19) the mean deviation of RV-SV from LV-SV was 29.0+/-10.8 ml (42.1+/-13.9%). In studies with high RV attenuation (> or =175 HUs, n=21) the mean deviation of RV-SV from LV-SV was significantly lower 6.9+/-10.5 ml (9.9+/-16.0%).

CONCLUSION

The accuracy of RV function analysis is dependent on the level of contrast medium attenuation achieved in the inferior RV. There should be at least intermediate attenuation (>175 HUs) to enable accurate functional analysis. At low attenuation levels RV function parameters are prone to underestimation.