Abstract-Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. Yet, the mechanisms of VF remain elusive. Pixel-by-pixel spectral analysis of optical signals was carried out in video imaging experiments using a potentiometric dye in the Langendorff-perfused guinea pig heart. Dominant frequencies (peak with maximal power) were distributed throughout the ventricles in clearly demarcated domains. The fastest domain (25 to 32 Hz) was always on the anterior left ventricular (LV) wall and was shown to result from persistent rotor activity. Intermittent block and breakage of wavefronts at specific locations in the periphery of such rotors were responsible for the domain organization. Patch-clamping of ventricular myocytes from the LV and the right ventricle (RV) demonstrated an LV-to-RV drop in the amplitude of the outward component of the background rectifier current (I B ). Computer simulations suggested that rotor stability in LV resulted from relatively small rectification of I B (presumably I K1 ), whereas instability, termination, and wavebreaks in RV were a consequence of strong rectification. This study provides new evidence in the isolated guinea pig heart that a persistent high-frequency rotor in the LV maintains VF, and that spatially distributed gradients in I K1 density represent a robust ionic mechanism for rotor stabilization and wavefront fragmentation.

No abstract

Objective Current chest compression(CC) guidelines for an infant recommend a two finger(TF) technique with lone rescuer and a two thumb(TT) with two rescuers, and for a child either a One hand(OH) or Two hand(TH) technique with one or two rescuers. The effect of a 30:2 compression:ventilation ratio(C:V) using these techniques on CC quality and rescuer fatigue is unknown. We hypothesized that during lone rescuer CC, TT in infant and TH in child achieves better compression depth(CD) without additional rescuer fatigue compared with TF and OH respectively. Design Randomized observational study. Setting University affiliated pediatric hospital. Subjects Adult healthcare providers certified in BLS or Pediatric Advanced Life Support. Interventions Laerdal™ Baby ALS Trainer and Resusci Junior manikin were modified to digitally record compression depth(CD), compression pressure(CP) and compression rate(CR). Sixteen subjects were randomized to each of the four techniques to perform 5 minutes lone rescuer 30:2 C:V CPR. Rescuer heart rate(HR) and respiratory rate(RR) were recorded continuously and the recovery time(RT) interval for HR/RR to return to baseline was determined. Subjects were blinded to data recording. Groups were compared using two-sample, two-sided t-tests. Measurements and Main Results Two-thumb technique generated significantly higher CD and peak CP compared to TF (p<0.001); there was no significant difference between OH vs. TH. TF showed decay of CD and CP over time compared to TT. CR(per minute) and actual compressions delivered were not significantly different between groups. No significant difference of fatigue and recovery time were observed, except TT group had greater increase in the rescuer’s HR(bpm) from baseline compared to TF group, p=0.04. Conclusions Two-thumb compression provides higher CD and CP compared to TF without any evidence of decay in quality and additional rescuer fatigue over 5 minutes. There was no significant difference in child CC quality or rescuer fatigue between OH and TH. Two-thumb technique is preferred for infant CC and our data supports the current guidelines for child chest compression.

No abstract