title: Pronounced HR variability after exercise in inferior ischemia: evidence that the cardioinhibitory vagal reflex is invoked by exercise-induced inferior ischemia.
abstract: Potent cardioinhibitory vagal reflex resulting in bradycardia and hypotension has been observed under particular conditions of transmural inferior ischemia and its reperfusion, such as those observed with acute infarction. However, whether exercise-induced ischemia with ST depressions that is subendocardial and that might be recurrently experienced in daily activities can evoke this reflex remains unknown. In patients with exercise-induced ST depressions due to either inferior [right coronary artery stenosis (RCA), n = 52] or anterior ischemia [left anterior descending artery stenosis (LAD), n = 51], we evaluated post exercise vagal activity (from 0 to 6 min) by the time constant of heart rate (HR) decay and HR variability by 30-s averages of the absolute values of successive RR interval differences (DeltaRR). Exercise parameters were similar between groups. The time constant was slightly but significantly shorter in RCA than LAD patients (79 +/- 24 vs. 93 +/- 29 s, P < 0.01). More significantly, DeltaRR early after exercise (0.5-2.5 min) was approximately twofold greater in RCA than LAD patients (from +76 to +118%, P < 0.001), indicating pronounced vagal activity stimulated by inferior ischemia. Revascularization prolonged the time constant (P < 0.05) and attenuated recovery DeltaRR in RCA patients (P < 0.05, n = 10) but did not change both parameters in LAD patients (n = 12). As well as acute inferior infarction, exercise-induced inferior subendocardial ischemia, which might recurrently occur in daily activities, activates the cardioinhibitory reflex. These new findings must be taken into account in interpreting vagal activity in patients with coronary artery disease.
authors.affiliation: Department of Medicine, National Cardiovascular Center, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tahara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takaki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Taguchi
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Suyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kurita
authors.forename: Wataru
authors.initials: W
authors.lastname: Shimizu
authors.forename: Shunichi
authors.initials: S
authors.lastname: Miyazaki
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.forename: Kenji
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology* / Q000628:therapy; D009204:Myocardial Revascularization; D009433:Neural Inhibition / Q000502:physiology; D012018:Reflex / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*