Resting Pd/Pa correlates with fractional flow reserve but not angiographic severity in calcified coronary arteries

OBJECTIVE Study the effect of coronary artery calcium (CAC) on resting coronary physiological indices. BACKGROUND Prior studies found no correlation between angiographic stenosis and fractional flow reserve (FFR) in heavily calcified arteries. METHODS Two hundred consecutive patients undergoing whole-cycle resting Pd/Pa and FFR evaluation of a single lesion of intermediate severity (40-80%) had CAC quantified based upon radiopacities at the site of the stenosis, where 0 = none or mild calcium, 1 = moderate calcium, and 2 = severe calcium. RESULTS Mean age was 61 ± 11 years and 34% were female. The mean degree of stenosis, FFR, and resting Pd/Pa were 60 ± 12%, 0.83 ± 0.08, and 0.93 ± 0.05, respectively. Resting Pd/Pa correlated with degree of angiographic diameter stenosis (DS) as determined by quantitative coronary angiography (QCA) or visual estimation in arteries with calcium score of 0 or 1, but there was no correlation in severely calcified arteries. The diagnostic accuracy of DS ≥70% by QCA to predict hemodynamic significance was 68% with calcium scores of 0/1, but only 43% with calcium score = 2. Resting Pd/Pa was highly correlated with FFR irrespective of the degree of CAC (R2 = 0.68, p