The Effect of Adenosine A₁ Receptor Antagonism on Return of Spontaneous Circulation andShort-Term Survival in Prolonged Ventricular Fibrillation

Abstract

Background. Endogenous adenosine (ADO) is cardioprotective during ischemia andits myocardial concentration increases during untreated ventricular fibrillation (VF). We have previously shown that ADO A₁ receptor (ADOA₁R) antagonism hastens the time-dependent decay in VF waveform morphology during the circulatory phase of cardiac arrest. Objective. To determine the effect of ADOA₁R antagonism on ROSC andshort-term survival in prolonged VF. Methods. Thirty-six swine were assigned by block randomization to one of three groups: a group that received only vehicle (control), an ADOA₁R antagonist pretreatment group (pre), anda group that was given ADOA₁R antagonist during resuscitation (during). The animals were instrumented under anesthesia, andADOA₁R antagonist or vehicle, per group assignment, was infused 5 minutes prior to VF induction. At minute 8 of untreated VF, chest compression with ventilation was initiated anda standard drug cocktail, with ADOA₁R antagonist or vehicle, was given. The first rescue shock (150 J biphasic) was delivered after 11 minutes of VF. Proportions with 95% confidence intervals (CIs) were calculated for the two outcome measures. Results. The baseline characteristics andchemistry values for the three groups were mathematically the same. The during group had a greater proportion of female animals (seven of 12) in comparison with the control group (two of 12) (p = 0.03). ADOA₁R antagonism hastened the decay of VF as previously demonstrated, but the rate of ROSC was the same for all groups: control = seven of 12, pre = six of 12, andduring = seven of 12. There were also no differences in short-term survival: control = four of 12, pre = five of 12, andduring = seven of 12. Conclusions. In this study, ADOA₁R antagonism had no effect on outcome whether given before induction of VF or upon resuscitation after 8 minutes of untreated VF. The role of endogenous ADO in prolonged VF remains unclear.

Key words:

• cardiology
• arrhythmias, clinical electrophysiology, drugs
• treatment
• CPR andemergency cardiac care
• diagnostic testing
• electrocardiology
• electrophysiology
• basic science research
• animal models of human disease