title: Relationship between impaired chronotropic response, cardiac output during exercise, and exercise tolerance in patients with chronic heart failure.
abstract: The present study was undertaken to investigate the relationship between the extent of impaired chronotropic response and cardiac output during exercise, and exercise tolerance in patients with chronic heart failure. The subjects consisted of 24 patients (mean 60.1 +/- 14.0 years) who had mild chronotropic incompetence. Cardiopulmonary exercise testing was performed in all patients, and heart rate (HR), anaerobic threshold (AT), maximum oxygen uptake (peak VO2), slope of the regression line relating the ventilatory equivalent to carbon dioxide output (VE/VCO2 slope), and exercise time were measured. Cardiac output (CO) was measured by a thoracic bioimpedance method and cardiac index (CI) was calculated. Plasma norepinephrine (NE) was measured at rest and immediately after the exercise test. The changes in HR, NE, and CI from the resting state to immediately after exercise were calculated as deltaHR, deltaNE, and deltaCI, respectively. The deltaNE was converted to a logarithmic scale and deltaHR/log deltaNE was used as a parameter of HR response to sympathetic nerve stimulation. The results were as follows: HR and NE in the resting state had no correlation with AT and with peak VO2. DeltaHR/log deltaNE correlated positively with both AT and peak VO2, and negatively with the VE/CO2 slope. DeltaHR/log deltaNE correlated positively with peak CI, %deltaCI, and deltaCI/exercise time. The data suggest that one of the mechanisms of low exercise tolerance in chronic heart failure patients was due to an inadequate increase in CO response against exercise caused by an impaired HR response to increased NE.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki, Japan.
authors.forename: Hisanori
authors.initials: H
authors.lastname: Samejima
authors.forename: Kazuto
authors.initials: K
authors.lastname: Omiya
authors.forename: Masato
authors.initials: M
authors.lastname: Uno
authors.forename: Kohji
authors.initials: K
authors.lastname: Inoue
authors.forename: Masachika
authors.initials: M
authors.lastname: Tamura
authors.forename: Kae
authors.initials: K
authors.lastname: Itoh
authors.forename: Kengo
authors.initials: K
authors.lastname: Suzuki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Akashi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Seki
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Suzuki
authors.forename: Naohiko
authors.initials: N
authors.lastname: Osada
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Tanabe
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Miyake
authors.forename: Haruki
authors.initials: H
authors.lastname: Itoh
mesh_terms: D000328:Adult; D000368:Aged; D002302:Cardiac Output; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology