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Response by Pibarot et al to Letter Regarding Article, "Echocardiographic Results of Transcatheter Versus Surgical Aortic Valve Replacement in Low-Risk Patients: The PARTNER 3 Trial".

Circulation. 2020;142:e314–e315. DOI: 10.1161/CIRCULATIONAHA.120.050172 e314 Philippe Pibarot, DVM, PhD Michael J. Mack, MD Martin B. Leon, MD Rebecca T. Hahn, MD For the PARTNER 3 Investigators In Response: We thank Loardi and Zanobini, Pollari et al, and Useini and Strauch for their interest in and comments regarding our article reporting echocardiographic data of the PARTNER 3 trial (Placement of Aortic Transcatheter Valves).1 There is a growing body of evidence suggesting that, as opposed to transcatheter aortic valve replacement (TAVR), surgical aortic valve replacement (SAVR) is associated with a deterioration in right ventricular (RV) function, which may contribute to the worse clinical outcomes observed with SAVR versus TAVR in the population with low surgical risk of the PARTNER 3 trial. Consistent with these results, an analysis of the PARTNER 2A trial also revealed that worsening of RV function occurs 3-fold more frequently after SAVR versus TAVR in the intermediate-risk population and is associated with a 2.87-fold increase in mortality.2 As discussed in our article, the causes of the deterioration of RV function and of tricuspid regurgitation after SAVR are likely multifactorial, including potential detrimental effects of pericardiectomy and of cardiopulmonary bypass. We disagree with the concept suggested in some previous studies that the deterioration in RV longitudinal systolic function and thus of tricuspid annulus plane excursion observed after SAVR does not indicate a true deterioration in RV function and has no functional or clinical consequences. The marked deterioration of tricuspid annulus plane excursion that occurred from baseline to 30 days in the SAVR arm of the PARTNER 3 trial was paralleled by a worsening of tricuspid regurgitation and was strongly and independently associated with worse clinical outcomes, substantiating the clinical relevance of this finding. Valvulo-arterial impedance (Zva) is not solely a measure of bioprosthetic valve function but also integrates left ventricular (LV) outflow and arterial hemodynamics. Hence, Zva has the advantage of providing a more comprehensive assessment of the effect of aortic valve replacement (AVR) on the overall performance of the ventriculo-valvulo-arterial system. This measure reflects the overall energy cost (expressed in mm Hg) per milliliter of blood (indexed to body size) ejected by the heart. The results of the PARTNER 3 trial suggest that TAVR is associated with greater reduction in Zva and thus in LV energy cost compared with SAVR. However, Zva has limitations, including the fact that it is, as are all other echocardiographic measures of valve function, flow-dependent, and it is subject to measurement variability given that its formula includes 3 echocardiographic measures. The fact that the change in stroke volume does not parallel the change in LV ejection fraction after AVR is not surprising. Besides LV systolic function, several other factors may contribute to the increase in LV stroke volume after AVR, including the regression of LV concentric hypertrophy or remodeling, improvement in LV diastolic function and filling, and regression of mitral regurgitation and tricuspid regurgitation.3 These factors may have contributed to the higher increase in stroke volume observed © 2020 American Heart Association, Inc. RESPONSE TO LETTER TO THE EDITOR