Quantification of ventricular repolarization heterogeneity during moxifloxacin administration using V-index

Drug-induced alterations of ventricular heterogeneity must be limited to avoid induction of lethal ventricular arrhythmias. In here, a new parameter called V-index, able to measure the standard deviation of myocites´ repolarization times, was evaluated after moxifloxacin administration. 24-h Holter ECGs of 68 healthy subjects enrolled for a thorough QT study were retrospectively analyzed. The placebo and active-comparator (moxifloxacin) arms were considered. The standard QT interval (Fridericia´s correction) was included as well, for a direct comparison. V-index and QT increased along with the drug´s serum concentration and were statistically different from values in the placebo arm (p<;0.05). Peak values were reached 5 hours after administration (QT_c: 428.77 ± 25.17 ms at 5h vs 418.08 ± 23.37 ms at 0h; V-index: 31.67 ± 11.01 ms at 5h vs 27.72 ± 7.59 at 0h) and both were statistically different from predose (p<;0.05). Interestingly, V-index displayed a larger percent variation (27.72% ± 34.06% vs 2.93% ± 2.81%; p<;0.05).