Right Ventricular Outflow Tract Velocity Time Interval: An Invaluable Yet Forgotten Echocardiographic Variable.

BACKGROUND

Echocardiographic examination of the right ventricular outflow tract (RVOT) has been invaluable in examining pulmonary artery (PA) flows and RV hemodynamics in response to increasing afterload. Currently, the TAPSE/PASP ratio is the preferred noninvasive variable for this assessment.

METHODS

Our main aim was to determine the specific relationship that might exist between RVOT VTI Doppler measurements and TAPSE/PASP ratios across a wide range of different left ventricular (LV) ejection fractions and PASP values.

RESULTS

Our study is the first to provide cutoff values for RVOT VTI according to the prevailing PA-RV hemodynamics. With TAPSE values >2 cm, normal RVOT VTI values should be >13 cm. However, when PASP or PVR are used in the metric analysis, RVOT VTI values >15 cm are, if PASP values <35 mmHg or PVR is <1.6 WU. Most interestingly, we found no correlation between RVOT VTI and the TAPSE/PASP ratio. Instead, the RVOT VTI/PVR ratio was very useful and appears as a potentially echocardiographic alternative to assess RV-PA coupling.

DISCUSSION

Even when both TAPSE and RVOT VTI, as well as PASP and PVR, convey somewhat similar information, significant anatomical and functional differences exist between these variables. These differences might explain why the RVOT VTI/PVR ratio might be more useful than TAPSE/PASP, particularly given the limitations of using TAPSE in certain clinical scenarios and the more reliable hemodynamic data provided by PVR. Regardless, additional studies are now needed to provide prospective comparisons between both ratios.