1) What was the relationship between RV-LV end diastolic area and all-cause mortality in your study? Were there any other variables associated with survival?

Pulmonary hypertension (PH) is often a life- threatening disease, and there is a turning point where right ventricular (RV) decomposition relates to a poor clinical outcome.¹ Recently, we have many more therapeutic options for the treatment of PH, so refining projections of prognosis are of practical importance.² High afterload by PH leads to RV hypertrophy and enlargement. RV remodeling affects both structure and function and is interrelated; however, the change in RV volume may affect left ventricle (LV) function through ventricular septal shift within the pericardium. The authors of this Expert Analysis article tested the hypothesis that remodeling effects on the RV and LV in patients with PH would have prognostic significance. 139 patients were studied with World Health Organization (WHO) group I precapillary PH. There were 72 deaths over five years. A simple measurement of RV and LV end-diastolic area traced from the 4-chamber view was used. Using a cutoff value of 0.93 of RV-LV end diastolic area ratio, patients with the ratios ≥0.93 had significantly higher all-cause mortality (hazard ratio (HR) 1.84; 95% confidence interval [CI], 1.14-2.96; P = .019). RV global strain was also significantly associated with survival using a cutoff of ≥-15% (HR 1.66; 95% CI, 1.03-2.67; P = .044). In univariate analysis, age, RV fractional area change (FAC), the grade of tricuspid regurgitation, RV global strain, and RV-LV end diastolic area ratio were associated with all-cause death over five years. However, only age and RV-LV end diastolic area ratio were most strongly associated with survival in multivariable analysis.

2) How would you apply the results of this study to your daily practice?

There are some indices to predict the outcome in PH patients, such as tricuspid annulus plane systolic excursion (TAPSE), RV fractional area change, and RV strain.^3-5 In the patient population, we saw that RV-LV end diastolic area ratio had the best correlation with pulmonary vascular resistance which was measured by right heart catheterization (RHC). The addition of the RV to LV end-diastolic area from the routine 4-chamber view can add prognostic significance. In simple terms, a large RV and a small LV appears to be worse than a large RV alone. If the ratio is more than equal to 0.93 in patients with pulmonary arterial hypertension, it may identify a higher risk patient who could potentially qualify for additional therapy.

3) How do you see the role of echocardiography in diagnosis and management of pulmonary arterial hypertension (PAH) compared to other modalities such as cardiac MRI and right heart catheterization?

Right heart catheterization is an important diagnostic tool in the management of patients with PAH and remains of significance. Echocardiography is the main complementary non-invasive test in daily practice and has great utility. The use of echocardiography on a frequent and repeated basis is more practical and without risk to the patient. Right heart catheterization at the time of the initial diagnosis and at a key point in the patient's progression is still considered important. The assessment of RV size and function adds to the measurement of pressures alone, with adverse RV remodeling heralding a poor prognosis. Cardiac magnetic resonance (CMR) imaging continues to be of great value in selected patients, and is considered the gold standard for RV volume assessment. However, it is often not practical to use CMR for routine follow up. Most recently, advances in three-dimensional (3D) echocardiography have also been an advantage to evaluate RV structure because of the complex geometry of the RV. 3D imaging can also acquire volume data which can be made throughout the cardiac cycle to assess pressure-volume relations in future applications.⁶ Presently, this study concluded that the simple 2D assessment of the 4-chamber view RV and LV end-diastolic area ratio is useful for daily practice, and adds important prognostic information.

References

1. Galie N, Corris PA, Frost A, et al. Updated treatment algorithm of pulmonary arterial hypertension. J Am Coll Cardiol 2013;62:D60-72.
2. Minai OA, Budev MM. Treating pulmonary arterial hypertension: cautious hope in a deadly disease. Cleve Clin J Med 2007;74:789-93, 797-800, 802 passim.
3. Fine NM, Chen L, Bastiansen PM, et al. Outcome prediction by quantitative right ventricular function assessment in 575 subjects evaluated for pulmonary hypertension. Circ Cardiovasc Imaging 2013;6:711-21.
4. Forfia PR, Fisher MR, Mathai SC, et al. Tricuspid annular displacement predicts survival in pulmonary hypertension. Am J Respir Crit Care Med 2006;174:1034-41.
5. Bossone E, Bodini BD, Mazza A, Allegra L. Pulmonary arterial hypertension: the key role of echocardiography. Chest 2005;127:1836-43.
6. Ryo K, Goda A, Onishi T, et al. Characterization of right ventricular remodeling in pulmonary hypertension associated with patient outcomes by 3-Dimensional wall motion tracking echocardiography. Circ Cardiovasc Imaging 2015;8:e003176.

Keywords: Cardiac Catheterization, Confidence Intervals, Echocardiography, Heart Ventricles, Hypertension, Hypertension, Pulmonary, Hypertrophy, Right Ventricular, Magnetic Resonance Spectroscopy, Pericardium, Prognosis, Tricuspid Valve Insufficiency, Vascular Resistance, Ventricular Function, Left

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