Echocardiography versus Magnetic Resonance Imaging Quantification and Novel Algorithm for Isolated Severe Tricuspid Regurgitation

Transthoracic echocardiography (TTE) is the first-line tool to evaluate isolated tricuspid regurgitation (TR), but has limitations, and its TR quantification compared with magnetic resonance imaging (MRI) has been studied infrequently. We compared isolated severe TR quantification by TTE against MRI, and developed a novel TTE-based algorithm. Isolated TR patients graded severe by TTE and undergoing MRI 2007/01-2019/06 were studied. TTE and MRI measurements were analyzed by correlation, area under receiver-operative characteristics curve (AUC), and classification and regression tree algorithm of TTE parameters to best identify MRI-derived severe TR (regurgitant volume ≥45mL and/or fraction ≥50%). A total of 108/262 (41%) graded as severe TR by TTE also had severe TR by MRI. There were moderate correlations between TTE and MRI in quantification of TR severity and right atrial size (Pearson r=0.428-0.645), but none to modest correlations between them in right ventricle quantification. Key TTE parameters to identify MRI-derived severe TR in the decision tree regression algorithm were right atrial volume indexed ≥47 mL/m2, then effective regurgitant orifice area ≥0.45 cm2, and especially if right ventricle free wall strain ≥-9.5%. This novel algorithm has AUC 0.76 and 79% agreement to detect severe TR by MRI, higher than the American Society of Echocardiography criteria with AUC 0.68 and 66% agreement (P=0.006 and P