Assessment of heart rate variability after calcium antagonist and beta-blocker therapy in patients with essential hypertension

Objective: Antihypertensive agents of different classes may have profound e ffects on heart rate variability (HRV). HRV changes in patients with essent ial hypertension were evaluated after pharmacological treatment by time dom ain (TD) analysis on 24-hour electrocardiographic (ECG) recordings. Design and Patients: In this randomised block single-blind trial, 45 patien ts with essential hypertension were randomly assigned to either atenolol, a cardioselective beta-blocker, carvedilol, a beta-blocker with vasodilator properties, or lacidipine, a long-acting dihydropyridine calcium antagonist , and underwent simultaneous 24-hour ECG and ambulatory blood pressure moni toring before and after 8 weeks' treatment. TD measures were calculated. Results: During treatment with atenolol and carvedilol, the 24-hour average normal RR [mean normal to normal intervals (NN)] was significantly increas ed (p < 0.0001 and p < 0.0002, respectively). Measures of tonic vagal activ ity were increased significantly only with atenolol: increase of 64.3% for the percentage of differences >50 msec between adjacent NN intervals and in crease of 45.2% for root mean square successive differences. By contrast, s tandard deviations (SD) of all NN over a 24-hour period and SD of means of 5-minute blocks of NN related to total and diurnal HRV were significantly i ncreased by lacidipine (13.4 and 18.9%, respectively) and decreased by carv edilol (-12.0% and -22.0%, respectively) but not significantly modified by atenolol. Modifications in TD parameters were unrelated to the degree of 24 -hour blood pressure reduction. Conclusions: HRV, assessed by TD, is modified differently according to the specific type of antihypertensive monotherapy used. These modifications cou ld have prognostic importance. TD measures of HRV may be a practical and po werful instrument for the evaluation of the effect of antihypertensive drug s.