Differential stress-induced ischemic electrocardiographic changes in acute versus stable coronary syndromes with severely reduced fractional flow reserve (≤0.60)

Background: Fractional flow reserve (FFR) is widely used to guide percutaneous coronary intervention (PCI) as a surrogate of inducible myocardial ischemia (IMI). However, the relationship between very low FFR, electrically manifest ischemia, and subsequent symptomatic benefit remains incompletely understood. Methods: We investigated stress-induced ischemic electrocardiographic changes in 79 patients with FFR ≤ 0.60, comparing acute coronary syndrome (ACS) and stable coronary artery disease (CAD), and its association with post-PCI symptom improvement. IMI was defined by ischemic ST-segment changes during adenosine stress testing. Pressure-derived physiologic indices, including the instantaneous wave-free ratio (iFR) and resting Pd/Pa, were measured, and angina-related symptoms were assessed using the Seattle Angina Questionnaire. Results: < 0.001). Despite similar angiographic severity and mean FFR values, iFR and resting Pd/Pa were significantly lower in ACS. In multivariate analyses, ACS and lower iFR or resting Pd/Pa independently predicted IMI. Although angina symptoms improved overall after PCI, the greatest improvement occurred in patients with ACS or IMI. Conclusions: At extremely low FFR values (≤0.60), substantial discordance exists between pressure-derived physiology and IMI, which is closely related to clinical presentation and symptomatic benefit after PCI.