Prevalence of atrial fibrillation and its association with INOCA endotypes: insights from the INOCA-IT registry

Abstract Background Although atrial fibrillation (AF) is a common arrhythmia with known adverse cardiovascular implications, its relationship with ischemia and non-obstructive coronary arteries (INOCA)—and with specific INOCA endotypes—has not been systematically investigated. Objective To evaluate whether atrial fibrillation is associated with a particular INOCA endotype and to explore clinical and physiological correlates within the INOCA population. Methods Within the INOCA-IT Registry (RF-2019-12369486), a cross-sectional analysis was conducted to determine the prevalence of AF among enrolled patients and to assess the distribution of all predefined INOCA endotypes according to AF status. Clinical characteristics and invasive hemodynamic indices were compared between patients with and without AF. Univariable and multivariable logistic regression analyses were performed to identify independent predictors of AF. Results Among 213 enrolled patients, 19 (8.9%) had a history of AF. Compared with patients without AF, those with AF were older (67.8±11.3 vs Non-AF 60.2±11.1years, p<0.01), had higher prevalence of diabetes mellitus (31.6% vs. Non-AF 13.9%, p=0.042), dyslipidaemia (89.5% vs. Non-AF 68.6%, p=0.057), and previous transient ischemic attack (15.8% vs. 4.1%, p=0.028), while they were less frequently smokers (21.1% vs. Non-AF 42.8%, p=0.066). No significant differences were observed in the distribution of vasospastic angina (VSA, p=0.155), coronary microvascular dysfunction (CMD, p=0.636), or non-cardiac pain endotypes (p=562), although microvascular spasm was present only among patients without AF (p=0.028). When CMD was stratified by the index of microvascular resistance (IMR) using a cutoff of 25, all AF patients with CMD exhibited high resistance endotype (IMR ≥ 25) (100% vs. 0%, p=0.08). Moreover, mean IMR values were significantly higher in AF patients compared with those without AF (29.7±32.4 vs Non-AF 21.0±13.2, p=0.024). IMR was identified as a predictor of AF both in univariable (p=0.035) and multivariable logistic regression (p=0.073). Conclusions In patients with INOCA, atrial fibrillation was associated with older age, a higher burden of metabolic and cerebrovascular comorbidities, and increased coronary microvascular resistance. These findings suggest a potential mechanistic link between atrial remodelling and coronary microvascular dysfunction, highlighting the need for further studies.For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.