Possible vagal effect of lidocaine: Investigation by HR spectral analysis

The mechanisms related to the onset and the offset of atrial fibrillation require a deeper understanding, in particular to enable the assessment of pharmacological interventions. Lidocaine has been known to have no or at most very little effect on the autonomic nervous system. The use of lidocaine in treatment of atrial arrhythmias is not at all established. Nevertheless we have shown in a recent study in dogs the efficacy of i.v. lidocaine in converting vagally-mediated atrial fibrillation back to sinus rhythm In order to study the effect of lidocaine on the autonomic cardiac control in humans, we performed spectral analysis of HR fluctuations in 19 healthy volunteers, who received a bolus of i.v. lidocaine 1.4 mg/kg, and in IS patients suffering from acute inferior myocardial infarction (1MI) and 13 patients suffering from acute anterior myocardial infarction (AMI), who received therapeutic doses of lidocaine by i.v. infusion 4 mg/min. HR variability and respiratory pattern were monitored. Integrating the HR power spectrum over predetermined frequency band, we focused mainly on the respiratory frequency band, known to predominantly reflect parasympathetic control. The administration of lidocaine resulted in an overall increase in mean HR: for the healthy controls an increase of 5.5±2.2%, for the IMJ an increase of 9.4∗3.5%, and for the AMI an increase of 8.1±2.9%. Simultaneously, following the administration of lidocaine, we observed a decrease in the power of respiratory fluctuations: for the healthy controls a decrease of 38.4± 12.5%, for the 1M1 a decrease of 46.3±32.9%. and for the AMI a decrease of 33.9∗16.2% (p<0.01 for all results). These findings consistently indicate that lidocaine has a significant para-sympatholytic effect on the human heart, in healthy volunteers as well as in patients in the acute phase of myocardial infarction..