Effects of the I-kr-blocker almokalant and predictors of conversion of chronic atrial tachyarrhythmias to sinus rhythm. A prospective study

Purpose: To assess the efficacy of the I-kr-blocker almokalant attempting t o convert chronic atrial tachyarrhythmias, and to find predictors of conver sion, to sinus rhythm. Methods: The electrophysiological effects of a 6-hour infusion of almokalan t, to a total dose of 25 +/- 4 mg, were assessed by ECG and transesophageal atrial electrograms (TAE) in 100 consecutive patients with atrial fibrilla tion / flutter (n = 95 / 5) of 8 +/- 12 months' duration (range 1 to 99 mon ths). Results: The conversion rate was 32%. The time to conversion was 3.5 +/- 2. 2 hours. During infusion increases in QT(top) (292 +/- 35 to 335 +/- 44 ms, p < 0.001, after 30 minutes), QT (387 +/- 40 to 446 +/- 60 ms, p < 0.001), corrected QT (425 +/- 30 to 487 +/- 44 ms, p < 0.001), and QT dispersion ( 21 +/- 12 to 29 +/- 31 ms, p = 0.02), were paralleled by decreases in T wav e amplitude (0.31 +/- 0.19 to 0.23 +/- 0.16 mV, p < 0.001), and atrial rate (425 +/- 78 to 284 +/- 44 beats per minute (bpm) on ECG, and 396 +/- 72 to 309 +/- 44 bpm on TAE), with no differences between converters to sinus rh ythm and non-converters. Patients with aberrantly conducted beats, and T wa ve variation, also increased. Calcium antagonists were more common among co nverters. A decreasing T wave amplitude predicted conversion. Four patients developed torsades de pointes. Conclusions: This study demonstrates class III action of almokalant, with a conversion rate of 32% of long-standing, chronic atrial tachyarrhytmias. A n early decrease in T wave amplitude was associated with conversion to sinu s rhythm.