Anesthetic Preconditioning Decreases Arrhythmias and Improves Regional Conduction in Isolated Hearts

Objective: Anesthetic preconditioning (APC) is known to protect the heart against necrosis and contractile dysfunction, but protection against arrhythmias has not been well characterized. The authors hypothesized that APC alters the dispersion of electrophysiologic parameters to reduce arrhythmias after global (G) or regional (R) ischemia.

Design: Prospective vehicle-controlled study.

Setting: A university research laboratory.

Subjects: Langendorff rat hearts (n = 66).

Interventions: The authors examined the occurrence of arrhythmias, their mean duration, and the magnitude-squared coherence (MSC) of spectral components that provide a quantitative measure of rhythm organization at multiple sites in the heart, expressed as a function of time. Six groups received 0.5 minimum alveolar concentration (MAC) (APC-G, 0.5; APC-R, 0.5, respectively; 0.17 ± 0.01 mmol/L and 0.18 ± 0.05 mmol/L) or 1 MAC of isoflurane (APC-G 1.0; APC-R 1.0, respectively, 0.28 ± 0.02 mmol/L and 0.31 ± 0.05 mmol/L) before 30 minutes of global (ISC-G) or regional ischemia (ISC-R). Another group (SHAM) was neither subjected to ischemia nor isoflurane.

Measurements and Main Results: Electrodes were placed on the right atrium, the base, and the apex of the right ventricle. The incidence of ventricular fibrillation (VF) was as follows: ISC-G, 100%; APC-G 0.5, 50%; APC-G 1.0, 40%; ISC-R, 100%; APC-R 0.5, 50%; APC-R 1.0, 50% compared with SHAM 0%. Isoflurane-treated hearts showed delayed onset and decreased duration of arrhythmias on reperfusion. Untreated hearts showed low levels of MSC during reperfusion. In contrast, the isoflurane-treated hearts exhibited moderate-to-high levels of MSC during reperfusion.

Conclusion: APC reduces the incidence of arrhythmia after global and regional ischemia. In addition, the temporal synchrony of conduction is increased, suggesting a more organ-ized pattern of excitation.

Key Words: cardioprotection, myocardial ischemia, arrhythmias, preconditioning, anesthetics