Abstract Body: Background: Asphyxia can be a common cause of cardiac arrest in infants, in which survival rates remain low even for in-hospital arrests. Amplitude spectrum area (AMSA) is a numerical value based on the sum of weighted frequencies in ECGs. The greater the AMSA value, the greater probability of ventricular fibrillation (VF) reversal. During the decompensation phase of asphyxia, it is not known how compensatory hemodynamic mechanisms impact subsequent episodes of VF.

Hypothesis: We hypothesized that the level of hemodynamic compensation during asphyxia will correlate directly with AMSA level during subsequent VF.

Methods: In 4-week-old infant piglets, we induced cardiac arrest via asphyxia for 9 minutes. If the animals were not in VF by that point, a 3-second transthoracic shock was administered to induce VF. During the asphyxial phase, each animal was classified with one of 3 types of compensatory hemodynamic response based on peak mean arterial pressure (MAP) relative to baseline: hypo, normal, and hyper. AMSA measures were computed for artifact-free ECG at the 9-minute mark. ANOVA was used to compare mean AMSA value by response category.

Results: We used 34 animals (16 females, 18 males) that were approximately 4 weeks old. They had a combined average AMSA of 3.875 mV-Hz, weight of 10.62 kg, and MAP of 77.29 mmHg. The hyper responders (7) had an average AMSA of 4.5 mV-Hz and were 28.6% female. Normal responders (10) had had an average AMSA of 4.22 mV-Hz and were 60% female. Lastly, hypo responders (17) had an average AMSA of 3.47 mV-Hz and were 47.06% female. AMSA values differed between groups (p = 0.045).

Conclusions: Hyper responders had higher AMSA values compared to both normal and hypo responders. Future study could examine the mechanisms behind this action.