Right atrial strain in predicting right ventricular-pulmonary artery uncoupling in adult valvular heart disease patients with pulmonary artery hypertension undergoing cardiac surgery: A prospective observational study

Right ventricular–pulmonary artery (RV-PA) coupling refers to the interplay between RV contractility and RV afterload. Normal RV-PA coupling is maintained only when the RV function and RV afterload, i.e., the pulmonary vascular resistance are appropriately matched. A normal RV-PA coupling leads to a more efficient energy transfer between the RV and PA, and optimizes myocardial work. RV-PA uncoupling occurs when RV contractility cannot increase to match increased RV afterload as in patients with pulmonary artery hypertension (PAH), resulting in RV dysfunction and failure. Identifying uncoupled RVs in patients with PAH may help determine which patients are at a greater risk of RV failure following cardiac surgery; thus, potentially serving as a risk-stratification marker.

RV-PA coupling is computed as the ratio of RV end-systolic elastance (contractility index) to PA elastance (arterial load index), measured invasively with right heart catheterization. Though it has high sensitivity and accuracy, it is technically difficult to perform and has limited bedside applicability. RV-PA coupling can be also assessed non-invasively with echocardiography. Amongst the various non-invasive surrogates for RV-PA coupling, the tricuspid annular plane systolic excursion (TAPSE)/pulmonary artery systolic pressure (PASP) ratio has emerged as the best parameter that identifies uncoupled RVs. A cutoff value of TAPSE/PASP of < 0.36 mm/mm Hg predicts RV-PA uncoupling in patients with left heart disease.

RA strain is a novel parameter that provides a measure of RV function. It includes reservoir strain (peak RA strain), which indicates atrial compliance during ventricular systole; and conduit and pump (contractile) strain during ventricular diastole.  It can easily be obtained by the apical 4-chamber view and is an angle as well as load independent parameter. Though RA strain has been used to predict RV dysfunction in patients with type I PAH, cardiomyopathies, atrial arrhythmias etc., its usefulness in predicting RV-PA uncoupling is yet unexplored in adult valvular heart disease patients with PAH undergoing cardiac surgery. We hypothesize that preoperative RA strain can be used to predict RV-PA uncoupling following cardiac surgery.