Key result
Intravenous lidocaine reached maximal myocardial drug content faster than mexiletine (2.4 vs 5.5 minutes, p<0.001) and demonstrated more rapid subsequent efflux from the myocardium.
Why the study?
How do lidocaine and mexiletine differ in short-term myocardial uptake and redistribution in patients with ischemic heart disease, and what is the effect of pacing?
How do lidocaine and mexiletine differ in short-term myocardial uptake and redistribution in patients with ischemic heart disease, and what is the effect of pacing?
Coronary sinus pacing increases maximal myocardial drug content of lidocaine and mexiletine, with lidocaine showing faster uptake and efflux compared to mexiletine in patients with ischemic heart disease.
Answers are grounded in this paper and cite their sources.
These kinetic differences are hypothesis-generating for acute antiarrhythmic selection in ischemic disease; prospective outcome trials needed before clinical adoption.
Determination of short-term myocardial drug uptake and subsequent redistribution was performed in 27 patients with ischemic heart disease for the antiarrhythmic agents lidocaine and mexiletine, using frequent simultaneous measurements of drug concentration in aortic and coronary sinus blood, combined with measurement of coronary sinus blood flow after intravenous bolus injection of the drug. Maximal myocardial drug content per unit resting coronary sinus blood flow (MDC:F) was significantly greater in patients in whom coronary sinus pacing at 100 beat/min was performed during the initial period of drug uptake. Maximal myocardial drug content occurred after 2.4 +/- 0.2 (SEM) for lidocaine and after 5.5 +/- 0.6 min for mexiletine (p less than .001), and pacing did not affect time to maximum myocardial drug content. In nonpaced, but not paced, patients maximal MDC:F was greater in the lidocaine group than that in the mexiletine group. The subsequent efflux of lidocaine from the myocardium was more rapid that that of mexiletine in both paced and nonpaced groups.
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Horowitz et al. (1986) studied Ischemic heart disease (n=27). Lidocaine vs. Mexiletine was evaluated on Time to maximal myocardial drug content (p=<0.001). Intravenous lidocaine reached maximal myocardial drug content faster than mexiletine (2.4 vs 5.5 minutes, p<0.001) and demonstrated more rapid subsequent efflux from the myocardium.
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