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.