Irbesartan reduces QT dispersion in hypertensive individuals

Angiotensin type 1 receptor antagonists have direct effects on the autonomi c nervous system and myocardium. Because of this, we hypothesized that irbe sartan would reduce QT dispersion to a greater degree than amlodipine, a hi ghly selective vasodilator. To test this, we gathered electrocardiographic (ECG) data from a multinational, multicenter, randomized, double-blind para llel group study that compared the antihypertensive efficacy of irbesartan and amlodipine in elderly subjects with mild to moderate hypertension. Subj ects were treated for 6 months with either drug, Hydrochlorothiazide and at enolol were added after 12 weeks if blood pressure (BP) remained uncontroll ed. ECGs were obtained before randomization and at 6 months. A total of 188 subjects (118 with baseline ECGs) were randomized. We analyzed 104 subject s who had complete ECGs at baseline and after 6 months of treatment. Baseli ne characteristics between treatments were similar, apart from a slight imb alance in diastolic BP (irbesartan [n=53] versus amlodipine [n=51], 99.2 [S D 3.6] versus 100.8 [3.8] mm Hg; P=0.03), There were no significant differe nces in BP normalization (diastolic BP <90 mm Hg) between treatments at 6 m onths (irbesartan versus amlodipine, 80% Versus 88%; P=0.378). We found a s ignificant reduction in QT indexes in the irbesartan group (QTc dispersion mean, -11.4 [34.5] milliseconds, P=0.02; QTc max, -12.8 [35.5] milliseconds , P=0.01), and QTc dispersion did not correlate with the change in BP. The reduction in QT indexes with amlodipine (QTc dispersion, -9.7 [35.4] millis econds, P=0.06; QTc max, -8.6 [33.2] milliseconds, P=0.07) did not quite re ach statistical significance, but there was a correlation between the chang e in QT indexes and changes in systolic BP, In conclusion, irbesartan impro ved QT dispersion, and this effect may be important in preventing sudden ca rdiac death in at-risk hypertensive subjects.