Heart Rate Variability of a Heart Reviving from Extracorporeal Circulation

Heart rate variability (HRV), analyzed by non-linear methods confer prognostic values. HRV of a heart reviving from extracorporeal circulation (EC) has not been elaborated. We applied Multi-scale entropy (MSE) and Detrended fluctuation analysis (DFA) to study the HRV of patients receiving open-heart surgeries needing EC, during which the heart is standstill. Thirty-four patients were enrolled. ECG was recorded continuously. The analyses were categorized by clinical outcomes. HRV of those without major cardiovascular events (No-MACE) significantly decreased in complexity (4.92 ± 2.80 to 2.94 ± 1.87, p < 0.001). Those who suffered post-op MACEs got no changes in all studies of HRV, including MSE and DFA. We postulated that, the decrease of HRV complexity of a heart recovering from EC-induced standstill is probably a vagal-predominant process, implying less stress during the surgery. The absence of such decrement, perhaps a more adrenergic-driven phenomenon, might suggest some unresolved stress. This MSE-derived HRV parameter may be applied in further study of patients recovering from cardiac arrests.