Page 130 - Advanced echocardiography in characterization and management of patients with secondary mitral regurgitation

Chapter six. Right ventricular - pulmonary artery coupling
risk stratification of patients with secondary MR. Patients with a lower TAPSE/PASP (indicating RV-PA uncoupling) may be considered to have more advanced disease as the RV is not able to further increase its contractility (TAPSE) to cope with the increased afterload (PASP). In such patients RV function might recover less from the afterload reduction following correction of the MR. In this regard, in our study a TAPSE/PASP <0.35 was independently associated with worse outcomes in patients with secondary MR. However, future prospective studies are warranted to investigate whether the selection of candidates for valvular interventions would be improved by considering this measure of RV-PA uncoupling. Nonetheless, the present study confirms the importance of assessing RV function in HF patients with secondary MR and has demonstrated that correcting for RV afterload when evaluating RV performance (e.g. with the TAPSE/ PASP ratio) provides greater prognostic utility than considering RV performance alone (e.g. TAPSE). The prognostic utility of TAPSE/PASP ratio is even confirmed in patients with significant secondary tricuspid regurgitation (TR) (31).
Study limitations
The single center and retrospective nature of this study limits the generalizability of the results. Data on BNP or NT-proBNP were not systematically acquired in our centre. A recent study by Karam et al. (32) also evaluated RV-PA coupling in patients with secondary MR undergoing transcatheter mitral valve repair (TMVR). Although the results are similar, our study evaluated the prognostic value of RV-PA coupling in all patients with SMR and not only the patients requiring intervention. Pressure-volume loops derived from right heart catheterization are the gold standard to measure ventricular and arterial elastances and RV-PA coupling (33), and there are inherent limitations to the use of non-invasive measures of contractility and total (pulsatile and resistive) afterload. Although the evaluation of RV function with TAPSE might be considered a limitation of the current study, TAPSE is a robust and recommended parameter to assess longitudinal RV function (21). In addition, the pulsatile component of afterload contributes only ~23% to total afterload in normal patients and those with arterial PH (34) supporting the use of PASP for this analysis. Finally correcting TAPSE for PASP as an index of RV-PA coupling had been demonstrated to be the best echocardiographic indicator of RV-PA coupling against invasive measurements (11, 12).
Conclusions
In the present large-scale study of HF patients with significant secondary MR treated medically and with mitral valve interventions, RV-PA uncoupling as assessed by the TAPSE/PASP ratio was independently associated with long-term all-cause mortality and had incremental prognostic utility compared with TAPSE alone.
128