ABSTRACT
Background
Pulmonary acceleration time (PAT) forms a valuable echocardiographic parameter in deriving the mean pulmonary artery pressure (MPAP). The present study aims to derive and validate a formula relating MPAP and PAT in an Indian population.
Materials and methods
Preoperative echocardiography was performed in 22 adult cardiac surgery patients undergoing coronary artery bypass grafting (CABG) and/or mitral valve replacement. The PAT, PAT/right ventricular ejection time (RVET), PAT corrected for heart rate [(HR) HRcPAT], and tricuspid regurgitation (TR) peak velocity were correlated with MPAP measured from pulmonary artery (PA) catheter, and a new formula relating MPAP and PAT was derived and subsequently validated in another cohort of 21 patients.
Results
The PAT, HRcPAT, and PAT/RVET correlated well (r2 = 0.69, 0.68 and 0.47 respectively, p < 0.0001), while TR velocity correlated poorly with MPAP (r2 = 0.20, p = 0.046). The cutoff values of PAT and HRcPAT for diagnosing pulmonary artery hypertension (PAH) (MPAP = 25 mm Hg) were 74 and 99 respectively, with 92% sensitivity and 100% specificity. The derived formula (MPAP = 62.4 - 0.3 PAT) correlated well with the standard formula (79-0.45 PAT) on applying in the validation cohort (Bland—Altman plot, bias <10%). In subgroup analysis, patients with severe PAH (MPAP = 50 mm Hg) showed better correlation than patients with less than severe PAH (r2 = 0.633, p =0.038 a nd r2 = 0.46, p = 0.108 respectively). Similarly, the formula for deriving pulmonary vascular resistance index (PVRI) from PAT [(PVRI = 14.9-0.09 pulmonary artery acceleration time (PAAT)] correlated well with the existing formula (PVRI = 9 - 0.07 PAAT). The inter- and intraobserver variabilities were not significant.
Conclusion
The indexed formula is better in predicting MPAP from PAT in Indian population, particularly in patients with severe PAH (MPAP = 50 mm Hg) and the cutoffs of PAT and HRcPAT in predicting PAH (MPAP = 25 mm Hg) in an Indian population are 74 and 99 msec respectively.
How to cite this article
Munirathinam GK, Kumar A, Ganesan R, Puri GD. Derivation and Validation of Formula relating Pulmonary Acceleration Time and Mean Pulmonary Artery Pressure in Indian Population. J Perioper Echocardiogr 2017;5(1):3-11.