Importance of alpha 1-sympathetic activity for diurnal change in ischemic threshold in patients with stable angina

Circadian variation in coronary flow velocity reserve and its relation to α1-sympathetic activity in humans

BACKGROUND

The circadian change in coronary microvascular function has not been directly assessed in human beings. Recent advances in transthoracic Doppler echocardiography (TTDE) provide noninvasive, physiological assessment of coronary flow velocity reserve (CFVR).

METHODS

This study consisted of 20 young healthy subjects (24 ± 2 years, 20 men) who underwent CFVR examinations at 3 different times; early morning (6AM), late morning (11AM) and late evening (10PM). The flow velocity in the distal portion of the left anterior descending coronary artery was measured with TTDE at baseline and during adenosine infusion to calculate CFVR. These examinations were repeated with the intake of α1-blocker (prazosin 1mg) on the other day.

RESULTS

CFVR showed a circadian variation with an increase from the early morning to the late morning, following a decrease to the late evening thereafter (4.4 ± 0.9 at 6AM; 5.2 ± 1.3 at 11AM; 4.2 ± 1.1 at 10PM, p<0.001). In the study with α1-blocker, CFVR was comparable between the early morning and the late morning, whereas CFVR in the late evening was lower than those in other 2 time points (5.0 ± 1.1 at 6AM; 4.9 ± 0.9 at 11AM; 4.3 ± 0.9 at 10PM, p<0.001).

CONCLUSIONS

This study demonstrates that CFVR has a circadian variation in humans, with an increase from the late evening to the late morning. Adding α1-blocker ameliorated CFVR only in the early morning, indicating that α1-sympathetic activity plays a heterogeneous and important role in the circadian change of CFVR in humans.

Efficacy and safety of molsidomine once-a-day in patients with stable angina pectoris

BACKGROUND

The objective of this study was to compare the efficacy and tolerability of molsidomine prolonged-release 16 mg once-a-day (o.a.d.) with 8 mg twice-a-day (b.i.d.) and placebo in patients with stable angina pectoris.

METHODS

After a run-in placebo period of 7 days, the two formulations were compared acutely and then chronically (2 weeks) using cycloergometric tests and a randomized, multicenter, double-blind, double-dummy, crossover design in 533 patients. The quality of life was assessed using the frequency of anginal crises and nitrate sublingual tablets consumption.

RESULTS

Both formulations significantly improved exercise test parameters compared with placebo, being it after acute drug intake or after a 2-week treatment period and independently of spontaneous diurnal variation in exercise tolerance. Noninferiority of molsidomine 16 mg compared with 8 mg was demonstrated with a statistically significant superiority of the 16-mg formulation from 14 to 24 h postintake. Both treatments reduced incidence of anginal attacks and use of sublingual isosorbide dinitrate tablets. Tolerability of active drugs was satisfactory, the incidence of drug-related headache being not significantly different from placebo. Only hypotension was significantly more frequent with molsidomine 16 mg than with placebo, pretrial diastolic blood pressure being significantly lower in these patients than in those who did not develop hypotension during the study.

CONCLUSIONS

Both molsidomine formulations were effective in controlling patients' angina, did not induce any habituation and were well tolerated. However, the once-daily 16-mg formulation tended to provide better 24-h protection against myocardial ischemia than the 8-mg b.i.d. formulation.