Dopamine and dobutamine have different effects on heart rate variability in patients with congestive heart failure.

BACKGROUND

Autonomic dysfunction plays an important role in the pathogenesis, treatment and prognosis of congestive heart failure (CHF). Sympathomimetic amines have been widely used in the treatment of CHF, but reports on their autonomic effects in CHF are rare. This study was designed to evaluate the effects of dopamine and dobutamine on cardiac autonomic function as assessed by heart rate variability (HRV).

METHODS

Twenty patients with symptomatic CHF (systolic dysfunction) were enrolled. After recording one-hour baseline electrocardiographs (ECGs), patients were randomly selected for either dopamine (4 micrograms/kg/minute, Group A) or dobutamine (4 micrograms/kg/minute, Group B) treatment for three days. On the third day, a 24-hour ambulatory ECG was recorded and a tilt-table test was performed. Only furosemide and nitrates were allowed for adjunctive therapy. HRV was measured before and after treatment in both time and frequency domains. Frequency-domain HRV was also measured during head-up tilt.

RESULTS

After treatment, all patients improved [New York Heart Association fraction (NYHA Fc) 3.7 to 2.0]. Group A patients had higher post-treatment 24-hour HRV than those in Group B. SDNN (standard deviation of the average normal RR intervals in the entire ECG recording), SDANN (standard deviation of the average normal RR intervals for all five minute segments of an entire ECG recording) and SDNN indices in Group A were significantly higher than in Group B (90 +/- 33 ms vs 41 +/- 12 ms, 78 +/- 32 ms vs 36 +/- 11 ms, and 37 +/- 19 ms vs 16 +/- 7 ms, respectively, all p < 0.05). rMSSD (the square root of the mean of the squared differences between adjacent normal RR intervals over the entire ECG recording) and pNN50 (percentage of differences between adjacent normal RR intervals that are greater than 50 ms computed over the entire ECG recording) were also higher in Group A patients, with borderline significance. All measurements of total frequency and low-frequency and high-frequency components tended to be higher in Group A than Group B, but this was only significant for total frequency amplitude (22.9 +/- 13.4 ms vs 10.9 +/- 6.1 ms, p < 0.05). Dopamine but not dobutamine treatment seems to restore the depressed circadian change in frequency-domain HRV classically seen in patients with CHF. The HRV change during head-up tilting did not differ between the two groups. Three patients in Group B showed non-sustained ventricular tachycardia on ambulatory ECG during the treatment period.

CONCLUSIONS

Dopamine and dobutamine have comparable therapeutic effects in patients with CHF, but low-dose dopamine more favorably affects cardiac autonomic function.