Effects of short-acting and long-acting loop diuretics on heart rate variability in patients with chronic compensated congestive heart failure.

BACKGROUND: We investigated the effects of a short-acting loop diuretic (furosemide) and a long-acting loop diuretic (azosemide) on heart rate variability, fluid balance, and neurohormonal responses in patients with mild to moderate chronic congestive heart failure. METHODS: Nineteen patients with mild to moderate chronic congestive heart failure received furosemide (40 to 60 mg/day) or azosemide (60 to 90 mg/day) for 5 days in a crossover manner. We performed time-domain and frequency-domain analyses of 24-hour Holter electrocardiographic recordings to assess heart rate variability. RESULTS: The 24-hour urinary sodium excretion was similar during the furosemide and azosemide treatment periods but was significantly greater in the first 2 hours after drug administration during furosemide treatment. Plasma renin activity and the hematocrit level increased and high-frequency power significantly decreased 2 hours after the administration of furosemide only. The standard deviation of all normal R-R intervals and the root mean square of successive differences in the R-R interval were lower with furosemide than with azosemide (P <.05). CONCLUSIONS: Furosemide, a short-acting loop diuretic, has a greater influence on heart rate variability and fluid balance than azosemide, a long-acting loop diuretic, in patients with mild to moderate chronic congestive heart failure.