Relationship between atrial fibrillation and blunted hyperemic myocardial blood flow in patients with hypertrophic cardiomyopathy.

Atrial fibrillation (AF) and coronary microvascular dysfunction (CMD) are common in hypertrophic cardiomyopathy (HCM), but whether they are associated is unclear. We assessed the relationship between AF and CMD in HCM. Methods and Results: Global hyperemic myocardial blood flow (hMBF) was measured in 95 HCM patients (16 with, 79 without paroxysmal or chronic AF) by N-13 ammonia positron emission tomography (PET) after dipyridamole infusion. AF patients were older (50.5 ± 13.4 vs. 38.7 ± 14.9 years, P < .0005), had larger left atrial diameter (49.8 ± 7.4 vs 38.6 ± 5.7 mm, P < .00001), and left ventricular end-systolic diameter (30.4 ± 6.7 vs 25.5 ± 5.3 mm, P < .005) compared with those in stable sinus rhythm. In patients with AF, hMBF was significantly lower (1.23 ± 0.44 vs 1.87 ± 0.90 mL/min/g, P < 0.0001). In multivariate logistic regression analysis, hMBF, left atrial diameter, and age were independently associated with AF (P < .05 for all). Conclusions: HCM patients with paroxysmal or chronic AF have lower hMBF than those in stable sinus rhythm. The association between CMD and AF is independent of other known predictors of AF, suggesting a causal link between these two features.