Right ventricular myocardial performance index (RV MPI)
The index of RV myocardial performance, also known as Tei index, is a marker of both systolic and diastolic RV function and it is calculated by dividing the total isovolumic time (isovolumic contraction plus isovolumic relaxation) to the ejection time [19]. It can be measured using either pulsed-wave Doppler or tissue Doppler, the cut-offs proposed for abnormal RV MPI being >0.43 using pulsed Doppler method and >0.54 using tissue Doppler method [16]. The advantage of RV MPI is that it bypasses the limitations of the complex RV geometry, as it is derived from time intervals only [18]; however, irregular rhythms make MPI difficult to calculate [19].
Vizzardi et al. assessed the prognostic value of RV MPI (calculated with the pulsed Doppler method) in a cohort of patients with HF and reduced LVEF, who were prospectively followed for 5 years for a combined endpoint of cardiac death and readmissions for HF. The authors found that a RV MPI>0.38 was an independent predictor of adverse outcome [30]. In a study by Field et al., each 0.1-unit increase in RV MPI (assessed by pulsed Doppler) was associated with a 16% increased risk of MACE (defined as death, cardiac transplantation or ventricular assist device placement) in patients with advanced HF referred for cardiac resynchronization therapy (CRT) [31]. To our knowledge, no studies evaluated the prognostic role of TDI-derived RV MPI in HF, although some authors suggest that tissue Doppler MPI is superior to pulsed Doppler MPI because it has the advantage of recording all the time intervals in the same cardiac cycle [32].