Negative expansion resistance (NER) phenomenon predicts hemodynamically non-significant coronary lesions

Revascularization decision for intermediate stenoses necessitates consideration of their hemodynamic impact. We report the use of distal coronary pressure (Pd) above proximal aortic pressure (Pa) during the early expansion period as a visual dichotomous marker (negative expansion resistance, NER) for rapid clinical decision-making. Simultaneous pressure and velocity signals were used to calculate instantaneous wave-free ratio (iFR), fractional flow reserve (FFR), hyperemic stenosis resistance (hSR), and to identify the NER. NER was defined as the Pd > Pa during the early-expansion period, which refers to early-decompression of coronary circulation marked by pressure decay (dP/dt < 0) coinciding the time-window of reduced ejection phase of systole to early diastole. Classification performance of NER was evaluated against iFR, FFR and hSR. Out of 475 lesions with mean diameter stenosis of 61% ± 16% from 388 patients with chronic coronary syndrome (CCS), 46%(217/475) exhibited the NER-phenomenon. Of these, 96% (209/217) had an iFR above 0.89(NPV = 0.96[95%CI 93-98] PPV = 0.47[95%CI 41-54]) indicating hemodynamically non-significant lesions. 94%(204/217) of the NER( +) lesions had an hSR below 0.80(NPV = 0.94 [95%CI 90-97] PPV = 0.36[95%CI 30-42]), and 88%(191/217) had an FFR above 0.80 (NPV = 0.88[95%CI 83-92] PPV = 0.53[95%CI 46-59]), indicating non-flow limiting lesions. Of 8 lesions with NER despite an abnormal iFR, only 1 had abnormal hSR, whereas 7 had normal hSR. Of 162 lesions with abnormal FFR, iFR identified 53 (33%) as 'normal' whereas NER was present in 26 (16%) of these cases.NER was associated with instantaneously stronger coronary decompression wave(8.0 ± 11.2 vs 5.5 ± 10.1 10.kW.m-2.s^-2 p:0.016) and higher flow acceleration(195 ± 204 vs 106 ± 182 cm.s^-2 p < 0.001). In conclusion, the NER, visually recognized by resting pressure tracings, rules out flow-limiting lesions in CCS with high certainty, offering a simple first-line evaluation for clinical decision-making, and warrants prospective clinical studies.