Pulmonary artery acceleration time (PAAT) forms a valuable echocardiographic parameter in deriving mean pulmonary artery pressure (MPAP). The formulae involving MPAP and PAAT were derived in western population. The present study aims to derive a formula for MPAP calculation from PAAT and to compare its accuracy with previous formulae in Indian population.
Preoperative echocardiography was performed in 22 adult cardiac surgery patients undergoing CABG and/or Mitral Valve replacements. PAAT,PAAT/Right ventricular ejection time (RVET), PAAT corrected for HR, were compared with MPAP measured from PA catheter using regression analysis. Similarly pulmonary vascular resistance (PVR in Woods unit) derived from PA catheter and from PAAT were compared. The new formula to calculate MPAP and PVRI from PAAT in msec was derived and compared for accuracy and reproducibility with the existing formula.
Mean PAAT, PVRI and MPAP were 82.77, 7.41 and 35.68 respectively. PAAT, HR corrected PAAT and PAAT/RVET correlated well with MPAP (R2 = 0.69, 0.68 and 0.47 respectively, p< 0.0001). When PAAT was used to derive MPAP (62.4 - 0.3 PAAT), it compared well with earlier formula of Mahanetal. (79-0.45PAAT) (cronbach’s alpha=0.93).[Figure 1] The cut-off value of PAAT and HR corrected PAAT for diagnosing PAH was 74 and 99 respectively with 92% sensitivity and 100% specificity. Similarly PVRI derived from echo parameters and PA catheter correlated well with each other (r=0.8, p<0.001) and the new formula derived (14.9-0.09 PAAT) correlated well with the older formula given by Levy et al.(9-0.07 PAAT)(cronbach’s alpha=0.75). The inter- and intra-observer variability was not significant.
Formula derived from present study predicts PAH with better sensitivity and specificity in Indian population than the older formula.