Derivation and Validation of Pd/Pa for the Assessment of Residual Ischemia Post Intervention - A Prospective All Comer Registry

Background:
Post intervention residual ischemia, as identified by FFR, has been shown to be frequent and is associated with long term outcomes. Resting non hyperemic indices including Pd/Pa have not been validated in this setting.

Methods:
The diagnostic accuracy and comparative performance of Pd/Pa in identifying ischemic FFR (<0.80) pre and post PCI were evaluated. Three patient subsets were analyzed. In the first model (Reference Pre PCI) comprising of 1255 patients and 1560 vessels, the accuracy of pre PCI Pd/Pa against FFR was computed. In model 2 (Derivation post PCI) comprising of 574 patient and 655 vessels evaluated the diagnostic accuracy of Post PCI Pd/Pa against post PCI FFR was studied. Model 3 (Prospective Validation Cohort) comprising of 230 patients (264 vessels) evaluated the diagnostic performance of Pd/Pa against FFR.

Results:
Median Pd/Pa and FFR were a) 0.90(IQR 0.90,0.98) and 0.80(IQR 0.71-0.88) in the reference pre PCI model b) 0.96(IQR 0.93-1.00) and 0.87(IQR 0.77-0.90) in Model 2 and 0.94(IQR 0.89-0.97) and 0.84(IQR 0.77-0.90) in Model 3, respectively. There was a significant linear correlation between Pd/Pa and FFR in all three models (p<0.0001).Using ROC analysis, the area under curve for Pd/Pa to predict FFR<0.80 was a) 0.87 in the pre PCI model b) 0.85 in the post PCI derivation cohort and c) 0.91 in the post PCI validation cohort (all p<0.0001 and p<0.05 for comparisons of c vs a and c vs b).

Conclusions:
Pd/Pa has excellent diagnostic accuracy for identifying residual ischemia post intervention which is comparable to its diagnostic performance for predicting ischemic FFR pre PCI. The predictive threshold depends on various factors including the index artery. Using a hybrid strategy , adenosine can be avoided in over 75% lesions post PCI.