The effect of residential exercise training on baroreflex control of heart rate and sympathetic nerve activity in patients with acute myocardial infarction.
OBJECTIVE
Exercise training has been shown to favorably affect the prognosis after acute myocardial infarction (AMI), but the mechanisms of such favorable effects remain speculative. The aim of this study was to determine whether exercise training improves baroreflex control of heart rate and muscle sympathetic nerve activity (MSNA) in patients with AMI.


METHODS
Prospective randomized clinical study.


METHODS
Thirty patients with an uncomplicated AMI were randomized into trained or untrained groups. Arterial BP, heart rate, and MSNA were measured at rest, and during baroreceptor stimulation (phenylephrine infusion) and baroreceptor deactivation (nitroprusside infusion). These measurements were performed at baseline and after 4 weeks of exercise training.


RESULTS
Peak oxygen uptake increased significantly (12.3 +/- 10.7% [mean +/- SD]) with exercise training. Resting MSNA reduced from 34 +/- 12 to 27 +/- 8 bursts/min in the trained group but not in the untrained group. Arterial baroreflex sensitivity (BRS) [from 8.9 +/- 3.0 to 10.3 +/- 3.0 ms/mm Hg, p < 0.05] and MSNA response to baroreceptor stimulation (change of integrated MSNA from - 47 +/- 23 to - 70 +/- 21%, p < 0.01) improved significantly in the trained group, but not in the untrained group. Despite baroreceptor deactivation improving MSNA response in both groups, there was no significant difference between the two groups.


CONCLUSIONS
Exercise training increased arterial BRS and decreased sympathetic nerve traffic after AMI, which indicate that the sympathoinhibitory effect of exercise training may, at least in part, contribute to the beneficial effect of exercise training in patients with AMI.
Mimura
Jun
J
CCU, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi City, Osaka, Japan. mimuraj@takii.kmu.ac.jp
Yuasa
Fumio
F
Yuyama
Reisuke
R
Kawamura
Akihiro
A
Iwasaki
Masayoshi
M
Sugiura
Tetsuro
T
Iwasaka
Toshiji
T
D017704:Baroreflex / Q000502:physiology*; D005081:Exercise Therapy; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology / Q000628:therapy*; D013564:Sympathetic Nervous System / Q000502:physiology*