Effects of burst stimulation during ventricular fibrillation on cardiac function after defibrillation

The Effects of Shock from Defibrillation Threshold Testing on Cardiac Systolic and Diastolic Function

BACKGROUND

Inappropriate implantable cardioverter defibrillator (ICD) shocks are associated with increased overall mortality. However, it remains unclear whether shocks from defibrillation threshold (DFT) testing directly impair cardiac function.

METHODS

DFT testing was performed in 34 patients who underwent ICD/cardiac resynchronization therapy with a defibrillator implantation/generator exchange. Heart rate and cardiac function, including left ventricular (LV) systolic pressure, LV end-diastolic pressure, peak positive and negative dp/dt ( + dp/dt and -dp/dt, respectively) of LV pressure, and the tau index, were assessed with a Mikro-Cath™ diagnostic pressure catheter (CD Leycom, Zoetermeer, the Netherlands). These parameters were measured before and 1 minute, 3 minutes, 5 minutes, 10 minutes, and 15 minutes after DFT testing.

RESULTS

Peak positive dp/dt increased over baseline at each interval (976 ± 229 mm Hg/s vs 1,039 ± 258, 1,049 ± 245, 1,042 ± 247, 1,037 ± 259, and 1,034 ± 254 mm Hg/s, respectively; P < 0.01). Furthermore, peak negative dp/dt (-1,140 ± 397 mm Hg/s vs -1,185 ± 447, 1,193 ± 435, -1,195 ± 434, -1,189 ± 449, and -1,186 ± 459 mm Hg/s, respectively; P < 0.01) and the tau index (65.1 ± 18.5 vs 62.5 ± 16.8*, 62.4 ± 15.9(**) , 63.0 ± 16.8*, and 62.8 ± 18.7*, respectively; *P < 0.05, (**) P < 0.01) decreased compared to those at baseline at each interval.

CONCLUSION

Shock after DFT testing improved LV systolic and diastolic function immediately, especially in patients with preserved LV ejection fraction.

Electrical therapy for post defibrillatory pulseless electrical activity

BACKGROUND

Defibrillation may convert ventricular fibrillation (VF) only to reveal profound mechanical dysfunction. Survival following this dysfunction, known as pulseless electrical activity (PEA) and electromechanical dissociation (EMD), is uncommon. We sought to evaluate an electrical therapy for primary post shock PEA following short duration VF.

METHODS AND RESULTS

Forty-eight episodes of VF, lasting 110 +/- 25 s, were induced in 16 anesthetized dogs. Following defibrillation, 35 episodes met PEA criteria (ABP < or = 36 mmHg diastolic and pulse pressure < or = 14 mmHg in the first 20 s post shock). These post defibrillation PEA episodes were either Not Treated (NT) or Treated (T) with packets of 4-20 monophasic 0.2 ms 50-100 Hz pulses of 20-60 V applied across the tip and coil of an integrated bipolar transvenous defibrillation lead positioned in the right ventricle. The therapeutic endpoint was return of spontaneous circulation (ROSC; self-sustained ABP > or = 60 mmHg diastolic and/or > or = 100 mmHg systolic) for over 2 min. In the Not Treated group, only 4 of 19 (21%) episodes spontaneously recovered to ROSC in 123 +/- 49 s while in the Treated group, 11 of 16 (69%) of the PEA episodes achieved ROSC in 102 +/- 92 s.

CONCLUSIONS

Electrical therapy increased the likelihood of ROSC in primary post defibrillation PEA three-fold (P < 0.01). Recovery occurred in the absence of thoracic compression, mechanical ventilation, or adjunctive drug therapy.