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This study was designed to assess the interference by closed-chest cardiopulmonary resuscitation (CPR) on the ventricular fibrillation (VF) ECG signal in a porcine model of cardiac arrest and to elucidate which variable of VF spectral analysis reflects best myocardial blood flow and resuscitation success during CPR. Fourteen domestic pigs were allocated to receive either 0.4 U/kg vasopressin (n = 7) or 10 ml saline (n = 7) after 4 min of VF and 3 min of CPR. Using radiolabeled microspheres, myocardial blood flow was determined during CPR before, and 90 s and 5 min after, drug administration. Using spectral analysis of VF, the median frequency, dominant frequency, edge frequency and amplitude of VF were determined simultaneously and before the first defibrillation attempt. Using filters in order to specify frequency ranges, stepwise elimination of mechanical artifacts resulting from CPR revealed that at a frequency bandpass of 4.3-35 Hz, median fibrillation frequency has a sensitivity, specificity, positive and negative predictive value of 100% to differentiate between resuscitated and non-resuscitated animals. The best correlation between myocardial blood flow and fibrillation frequency was found at a median frequency range of 4.3-35 Hz. We conclude that spectral analysis of VF can provide reliable information relating to successful resuscitation. In this model after elimination of oscillations due to mechanical CPR, median fibrillation frequency best reflects the probability of resuscitation success.

Objective: This study was designed to assess whether median frequency of ventricular fibrillation (VF) correlates with myocardial blood flow and defibrillation success during cardiopulmonary resuscitation (CPR) after epinephrine or vasopressin administration., Methods and Results: After 4 min of VF and 3 min of CPR, 14 pigs received 0.045 mg/kg epinephrine or 0.4 U/kg vasopressin. Using radio-labeled microspheres, median myocardial blood flow during CPR before, and 90 s and 5 min after drug administration (DA) was 15.5 (12.6, 23.1; 25th percentile, 75th percentile), 26.4 (18.5, 29.1), 16.9 (14.9, 19.1) mL min-1 100 g-1, respectively, in the epinephrine, and 16.9 (15.4, 18.9), 48.1 (36.9, 68.9) (P < 0.05 vs. before DA), 52.3 (38.5, 65.0) mL min-1 100 g-1, respectively, in the vasopressin group. Using spectral analysis of VF, median frequency of VF was 11.0 (10.7, 11.8), 11.3 (9.6, 13.1), 10.2, (8.8, 11.4) Hz, respectively, in the epinephrine, and 10.1 (10.0, 10.5), 11.7 (11.1, 14.2) (P < 0.05 vs. before DA), 13.2 (11.5, 13.9) Hz, respectively, in the vasopressin group at the same points in time. Median frequency correlates significantly with myocardial blood flow in the epinephrine (n = 21); rs = 0.772; P < 0.001) and in the vasopressin group (n = 21; rs = 0.905; P < 0.001). Median fibrillation frequency before the first defibrillation was 13.0 (12.2, 13.2) Hz in resuscitated (n = 8) and 9.2 (8.3, 10.2) Hz (n = 6) in non-resuscitated animals (P < 0.01)., Conclusions: We conclude that median frequency of VF reflects myocardial blood flow and the chance of successful defibrillation during closed-chest CPR after vasopressor treatment in a porcine model of VF.