Transient Lung‐Volume Reduction Improves First‐Shock Cardioversion Success by Reducing Transthoracic Impedance in Patients With Persistent Atrial Fibrillation

Background Transthoracic impedance (TTI) is an important determinant of the efficacy of direct‐current cardioversion (DCCV), as increased impedance may reduce myocardial current delivery. Because lung volume influences thoracic electrical properties, transient lung‐volume reduction (TLVR) may represent a simple strategy for acutely lowering TTI and improving cardioversion efficacy. This study evaluated the effect of a standardized TLVR maneuver on TTI and first‐shock cardioversion success in patients with persistent atrial fibrillation (AF). Methods This prospective, randomized study included 116 patients with persistent AF scheduled for first‐time radiofrequency ablation. Patients were randomized 1:1 to conventional mechanical ventilation (standard CV group, n = 58) or a standardized TLVR maneuver immediately before cardioversion (TLVR CV group, n = 58). Baseline TTI was measured before the intervention, and post‐TLVR TTI was additionally measured in the TLVR group. All patients underwent anterior–posterior cardioversion with an initial 200 J shock. First‐shock success was defined as maintenance of sinus rhythm for at least 1 min. Multivariable linear and hierarchical logistic regression analyses were performed to investigate determinants of impedance reduction and first‐shock success. Results First‐shock cardioversion success was significantly higher in the TLVR CV group than in the standard CV group (53.4% vs. 29.3%, p = 0.008), whereas cumulative success after up to three shocks was similar (96.6% vs. 91.4%, p = 0.242). The impedance reduction rate was significantly higher among patients with successful first‐shock cardioversion (9.09% vs. 5.00%, p < 0.001). In multivariable linear regression, TLVR independently increased the impedance reduction rate by 1.75 percentage points ( B = 1.751, p = 0.001), while a higher Body Roundness Index was associated with a lower reduction ( β = −0.468, p < 0.001). In the mechanistic logistic regression model, each 1% increase in impedance reduction was associated with a 2.23‐fold higher likelihood of first‐shock success (OR = 2.226, p < 0.001). Model explanatory power increased from 56.3% to 74.9% after the incorporation of impedance reduction. Conclusion A standardized TLVR maneuver immediately before cardioversion was associated with greater TTI reduction and an approximately twofold increase in first‐shock cardioversion success in patients with persistent AF. The impedance reduction rate emerged as a strong independent predictor of successful initial cardioversion, supporting a potential physiological mechanism linking acute lung‐volume reduction to improved electrical cardioversion efficacy.