title: Impaired chronotropic and vasodilator reserves limit exercise capacity in patients with heart failure and a preserved ejection fraction.
abstract: BACKGROUND
  Nearly half of patients with heart failure have a preserved ejection fraction (HFpEF). Symptoms of exercise intolerance and dyspnea are most often attributed to diastolic dysfunction; however, impaired systolic and/or arterial vasodilator reserve under stress could also play an important role.
  
  
  RESULTS
  Patients with HFpEF (n=17) and control subjects without heart failure (n=19) generally matched for age, gender, hypertension, diabetes mellitus, obesity, and the presence of left ventricular hypertrophy underwent maximal-effort upright cycle ergometry with radionuclide ventriculography to determine rest and exercise cardiovascular function. Resting cardiovascular function was similar between the 2 groups. Both had limited exercise capacity, but this was more profoundly reduced in HFpEF patients (exercise duration 180+/-71 versus 455+/-184 seconds; peak oxygen consumption 9.0+/-3.4 versus 14.4+/-3.4 mL x kg(-1) x min(-1); both P<0.001). At matched low-level workload, HFpEF subjects displayed approximately 40% less of an increase in heart rate and cardiac output and less systemic vasodilation (all P<0.05) despite a similar rise in end-diastolic volume, stroke volume, and contractility. Heart rate recovery after exercise was also significantly delayed in HFpEF patients. Exercise capacity correlated with the change in cardiac output, heart rate, and vascular resistance but not end-diastolic volume or stroke volume. Lung blood volume and plasma norepinephrine levels rose similarly with exercise in both groups.
  
  
  CONCLUSIONS
  HFpEF patients have reduced chronotropic, vasodilator, and cardiac output reserve during exercise compared with matched subjects with hypertensive cardiac hypertrophy. These limitations cannot be ascribed to diastolic abnormalities per se and may provide novel therapeutic targets for interventions to improve exercise capacity in this disorder.
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21205, USA.
authors.forename: Barry A
authors.initials: BA
authors.lastname: Borlaug
authors.forename: Vojtech
authors.initials: V
authors.lastname: Melenovsky
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Russell
authors.forename: Kristy
authors.initials: K
authors.lastname: Kessler
authors.forename: Karel
authors.initials: K
authors.lastname: Pacak
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Becker
authors.forename: David A
authors.initials: DA
authors.lastname: Kass
mesh_terms: D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology; D001810:Blood Volume; D002302:Cardiac Output; D002303:Cardiac Output, Low / Q000503:physiopathology*; D004837:Epinephrine / Q000097:blood; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010807:Physical Endurance; D011652:Pulmonary Circulation; D013318:Stroke Volume; D014664:Vasodilation
chemical_list: D009638:Norepinephrine; D004837:Epinephrine