Vagal enhancement as evidence of residual ischemia after inferior myocardial infarction.
BACKGROUND
Acute inferior myocardial infarction (MI) often induces transient sinus bradycardia through vagal enhancement, known as Bezold-Jarisch reflex, which is explained by preferential distribution of vagal nerve in the inferior wall. We examined vagal activity in relation to the occurrence of residual ischemia in patients with old inferior MI and assessed its diagnostic usefulness.


METHODS
Exercise myocardial scintigraphy was performed in 15 patients with old inferior MI, 19 angina pectoris (AP) patients with inferior ischemia but no MI, and 32 control subjects who had no evidence of cardiac disease. We analyzed the connection of residual ischemia in old MI with ST-segment response to exercise and with vagal activity as determined by coefficient of component variance of high frequency (CCV(HF)).


RESULTS
Exercise-induced percentage change in CCV(HF) was higher in patients with old MI and residual ischemia (18.8 +/- 13.5%) and AP (5.5 +/- 9.7%) than old MI but no residual ischemia (-24.1 +/- 4.9%) or control (-22.8 +/- 4.5%, P = 0.006). Percentage change in CCV(HF) > -5% had a good diagnostic value for the detection of residual ischemia in patients with old inferior MI with sensitivity of 83%, specificity of 89%, accuracy of 87%, and positive likelihood ratio of 7.50, which was higher than that of ST-segment depression (67%, 50%, 56%, and 1.33).


CONCLUSIONS
Vagal enhancement was associated with residual ischemia in old inferior MI as well as inferior AP. Measurement of CCV(HF) is useful in improving the diagnostic reliability of exercise electrocardiography in patients with old inferior MI.
Kawasaki
Tatsuya
T
Department of Cardiology, Matsushita Memorial Hospital, Osaka, Japan. js-k@wf6.so-net.ne.jp
Akakabe
Yoshiki
Y
Yamano
Michiyo
M
Miki
Shigeyuki
S
Kamitani
Tadaaki
T
Kuribayashi
Toshiro
T
Matsubara
Hiroaki
H
Sugihara
Hiroki
H
D000368:Aged; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000503:physiopathology; D017682:Myocardial Stunning / Q000175:diagnosis* / Q000503:physiopathology*; D012008:Recurrence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014630:Vagus Nerve / Q000503:physiopathology*