Effect of rates of perfusion on dominant frequency and defibrillation energy in isolated fibrillating hearts

This study assessed the influence of rates of reperfusion on excitability o f the myocardium using dominant frequency (DF) rin Hz) of VF and the relati onship of DF to the minimum defibrillation energy (MDE) (in J). Our hypothe sis was that increasing flow during reperfusion increases DF that raises MD E. Initially, six Langendorff perfused swine hearts were serially fibrillat ed and perfusion arrested for 4 minutes followed by reperfusion and defibri llation to establish reproducibility of the model. The epicardial ECG was a nalyzed for DF, In subsequent studies (n = 8) no flow VF was followed by 1- minute reperfusion at normal flow or 10% flow (low flow) and shocked with i ncreasing energy via epicardial pads until defibrillation. The DF at onset of no flow VF was 9.5 +/- 1.4 and decreased to 3.6 +/- 1.4 after 4 minutes, Reperfusion at normal flow increased the DF of VF compared to low flow aft er 1 minute (10.8 +/- 1.1 vs 4.5 +/- 1.1 Hz, P = 0.0002) and was associated with increased defibrillation energy requirements (13.5 +/- 5.0 vs 7.3 +/- 6.2 J, P = 0.047). In summary, defibrillation energy requirements are lowe r when myocardial excitability is reduced during low flow reperfusion.