[Hemodynamic effects of mexiletine]

The haemodynamic changes caused by intravenous mexiletine were studied in 12 patients. Initially the drug was given rapidly at the rate of 3 mg/kg/min for 10 minutes and then slowly at a rate of 0,06 mg/kg/min for 30 minutes. The plasma Mexiletine level measured after 20 minutes was used to divide the series of patients into two groups: in Group A the level was over 0,7 g/ml (0,961 +/- 0,109 microgram/ml) whilst in Group B the level was only 0,547 +/- 0,101 microgram/ml. The mean aortic pressure, heart rate and left ventricular end diastolic volume did not vary significantly in the two groups. The left ventricular end diastolic pressure rose, and the cardiac index and the ejection fraction fell in Group A. The indices of left ventricular contractility fell in all patients of the start of the injection. This depression only persisted to the end of the injection in Group A. Mexiteline did not cause significant changes in post extrasystolic potentialisation in the 5 cases in which this phenomenon was studied.