Electrocardiographic prediction of the success of cardiac resuscitation

Objectives: To identify a method for predicting the success or failure of a defibrillatory shock such as to avoid potentially detrimental interruption s of cardiopulmonary resuscitation (CPR), Such a method would also guide mo re optimal programming of automated external defibrillators, Design: Prospective, observational animal study. Setting: Medical research laboratory in a university-affiliated research and educational foundation. Subjects: Domestic pigs, Interventions: Ventricular fibrillation (VF) was electrically induced in 66 domestic pigs, After an interval of between 3 and 5 mins of untreated VF, precordial compression was begun. Electrocardiographic lead 2 was monitored and artifacts produced during precordial compression were removed by digit al filtering. Measurements and Main Results: In the derivation study, electrical defibril lation restored spontaneous circulation in 30 of the 66 animals. Successful ly resuscitated animals had significantly greater coronary perfusion pressu re, maximum VF amplitude, mean VF amplitude, and dominant VF frequency, No animals were resuscitated if the coronary perfusion pressure was <8 mm Hg, maximum amplitude was <0.48 mV, mean amplitude was <0.25 mV, or dominant fr equency <9.9 Hz independently of the duration of untreated VF, When mean am plitude and dominant frequency were combined, the predictability was furthe r improved. In an additional validation study of 14 animals, consecutive de fibrillations were uniformly unsuccessful if the combination of mean amplit ude and dominant frequency did not exceed the threshold values obtained in derivation study. Conclusion: Mean VF amplitude alone or in combination with dominant frequen cy of VF was expressed as a numerical score. It served as an objective noni nvasive measurement on a par with that of coronary perfusion pressure for p redicting the success of defibrillation, As such, it minimizes the detrimen t of repetitively interrupting mechanical interventions during CPR for elec trical defibrillation when an electrical shock predictably fails to restore an effective rhythm.