Effect of Selective Aortic Arch Perfusion on Median Frequency and Peak Amplitude of Ventricular Fibrillation in a Canine Model

Abstract

Study objective: To determine whether the computer-derived measures of median frequency or peak amplitude of ventricular fibrillation (VF), obtained by fast Fourier transform of the VF waveform, change during selective aortic arch perfusion in a canine model of cardiac arrest. Methods: Eight mongrel dogs (including 4 control animals) were sedated, intubated, catheterized, and instrumented to record the electrocardiogram (digitally at 100 Hz, filtered with a finite impulse response filter at 2 Hz), right atrial pressure, and aortic pressure during resuscitation in a model of VF-induced cardiac arrest. After 10 minutes of VF-induced arrest, cardiopulmonary resuscitation (CPR) with a mechanical chest compression device was initiated. Beginning 2 minutes later, the 4 study animals received, every 2 minutes, 45 seconds of selective aortic arch perfusion (SAAP) with autologous blood infusions under high pressure. Defibrillation was attempted after 3 minutes of CPR and every minute thereafter. Both study and control groups received standard-dose epinephrine (.01 mg/kg) every 3 minutes by means of an intraaortic catheter. The median frequency, peak amplitude, and coronary perfusion pressure (CPP) during the 5-second period just before defibrillation were obtained with the use of computer algorithms. Results: All SAAP animals and 1 control animal were resuscitated. Baseline measures of median frequency (8.4±1.5 versus 6.6±1.0 Hz) and peak amplitude (.18±.05 versus .36±.13 mV) were not different between the SAAP and control groups, respectively, at the start of CPR. SAAP infusion resulted in significant increases in the SAAP group compared with the control group: median frequency, 9.6±.4 versus 7.3±1.4 Hz; peak amplitude, .74±.21 versus .39±.15 mV; and CPP, 40.5±7.1 versus 18.0±15.0 mm Hg, respectively. Median frequency correlated with CPP ( r 2 =.67). Peak amplitude did not correlate with CPP ( r 2 =.06). Conclusion: Median frequency and peak amplitude increase with SAAP during cardiac arrest in a canine model. This method of resuscitation was reliable in allowing restoration of a stable perfusing rhythm after defibrillation. Changes in measures of peak amplitude and median frequency may reflect interventions that enhance the likelihood of successful defibrillation and may thereby offer a noninvasive means of monitoring interventions during cardiac arrest. [Barton C, Manning JE, Batson N: Effect of selective aortic arch perfusion on median frequency and peak amplitude of ventricular fibrillation in a canine model. Ann Emerg Med May 1996;27:610-616.]