title: Impaired chronotropic response to exercise in acute myocardial infarction patients with type 2 diabetes mellitus.
abstract: This study was undertaken in acute myocardial infarction (AMI) patients with non-insulin-dependent diabetes mellitus (type 2 DM) to investigate their impaired chronotropic response to exercise. Seventy-one AMI subjects entered the study, 30 with type 2 DM and 41 age- and body mass index-matched non-DM (control) patients. One month after the onset of AMI, these patients underwent cardiopulmonary exercise testing on a treadmill under a ramp protocol. Anaerobic threshold (AT) and peak oxygen uptake (peak VO2) were determined as indicators of exercise capacity. Plasma norepinephrine (NE) concentration was measured in blood samples obtained at 2 time points: during pre-exercise rest and immediately after peak exercise. The change in NE concentration during exercise, as an index of sympathetic nervous activity, was calculated as a percentage: deltaNE = [(NE during exercise) - (resting value)]/(resting value) x 100. The change in heart rate (HR) during exercise was calculated as a simple difference: deltaHR = [(peak HR) - (rest HR)]. Index of chronotropic response to exercise was then quantified as the deltaHR/deltaNE during exercise. No significant intergroup differences in ejection fraction at rest or HR at peak exercise were observed. However, VO2 at AT, peak VO2, deltaHR, and deltaHR/deltaNE were significantly lower in the type 2 DM group than in the non-DM group. DeltaHR correlated with VO2 at AT (r = 0.49, P<0.001) and with peak VO2 (r = 0.53, P<0.001) in all subjects. Also, deltaHR/deltaNE correlated with VO2 at AT (r = 0.42, P<0.001) and with peak VO2 (r = 0.44, P<0.001) in all subjects. AMI patients with type 2 DM had impaired cardiopulmonary responses to maximal and submaximal exercise testing and impaired chronotropic response to exercise, even though their cardiac function at rest was similar to that of non-DM AMI patients. The data suggest that one mechanism of impaired cardiopulmonary response to exercise in AMI patients with type 2 DM groups is an impaired chronotropic response.
authors.affiliation: Department of Rehabilitation Medicine, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Izawa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Tanabe
authors.forename: Kazuto
authors.initials: K
authors.lastname: Omiya
authors.forename: Sumio
authors.initials: S
authors.lastname: Yamada
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Ishiguro
authors.forename: Maiko
authors.initials: M
authors.lastname: Yagi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Hirano
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kasahara
authors.forename: Naohiko
authors.initials: N
authors.lastname: Osada
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Miyake
authors.forename: Masahiro
authors.initials: M
authors.lastname: Murayama
mesh_terms: D000368:Aged; D015992:Body Mass Index; D006328:Cardiac Catheterization; D002302:Cardiac Output; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000503:physiopathology; D005080:Exercise Test; D017079:Exercise Tolerance; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D016555:Matched-Pair Analysis; D008875:Middle Aged; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000209:etiology / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology