Abstract P20: Chest Compressions Can Cause Atrial and Ventricular Capture, during Both Sinus Rhythm and after Ventricular Fibrillation
Background: Ventricular capture (VC) by external mechanical forces has been described with precordial thumps and commotio cordis. The force required to electrically stimulate the heart during chest compressions (CCs) is not known.
Methods:In 6 pigs, CCs were delivered with a pneumatic piston at 4 different speeds (levels I-IV, with level IV similar to that of a commercial CC device) but constant maximal excursion of 2 inches and duty cycle of 300ms delivered every 2 s during 3 min of sinus rhythm (SR). Levels I and IV were then given after I min of ventricular fibrillation (VF) and then 5 min of VF. Electrograms and LV pressure were recorded. We defined VC as a QRS that was earlier, wider and of different morphology than SR closely following peak dP/dT generated by CC (45ms); atrial capture (AC) was earlier following the CCs.
Results: During SR, increasing compression speed significantly increased the number of VCs (Figure⇓, * marks VC) and ACs (VCs: level I 1.3±1.3, II: 3.1±6.8, III:7.7±10.1, IV:14.3±8.5, p=0.008) (atrial capture: I: 2.8±1.9, II:9.3±9.7, III 15.2±10, IV: 38±16, p=0.003). The mean number of VCs for levels I and IV were 10.5±12.8 and 14.3±8.5 (p=0.79) after 1 min of VF and 10.3±13 and 18±13 (p=0.17) after 5 min of VF. ACs for levels I and IV were 6±6 and 27±11 (p=0.007) after 1 min of VF and 3.5±7 and 13.2±5 after 5 min of VF (p=0.04). VCs were more frequent after 5 min than 1 min of VF for both levels of CC delivered(p<0.001).
Conclusion: CCs can stimulate both VCs and ACs, and the incidence of capture is increased when compression speeds are faster, at levels similar to clinically used devices.