title: Accuracy of estimating exercise prescription intensity in patients with left ventricular systolic dysfunction.
abstract: OBJECTIVE
  Exercise prescription in patients with left ventricular systolic dysfunction (LVSD) is difficult. Exercising beyond ventilatory threshold (VT) can have negative physiologic effects; therefore, exercise prescribed above VT may be detrimental. A majority of cardiac rehabilitation programs use the Karvonen/heart rate reserve (HRR) method, rating of perceived exertion (RPE), and/or a percentage of oxygen consumption to prescribe exercise intensity. The purpose of this study was to determine if these methods correlate with an exercise intensity below VT in LVSD patients.
  
  
  METHODS
  The authors studied 52 patients (37 males, 15 females; age 52 +/- 13 years; left ventricular ejection fraction 27% +/- 8%) who underwent a symptom-limited cardiopulmonary exercise test and reached VT to determine functional capacity and exercise prescription.
  
  
  RESULTS
  Peak heart rate (HR) as well as HRR derived minimum (60%), midpoint (70%), and maximum (80%) HR were highly correlated (P < 0.001) with HR at VT. Using these three different HR cutoff formulas from HRR, 15% to 62% of patients were prescribed exercise outside the range of VT-HR +/- 10%. The midpoint (70% HRR) best predicted exercise HR in the VT-HR +/- 10% range (73% of patients). Mean oxygen consumption at VT was 83 +/- 9% of peak oxygen consumption. There was no correlation (P < 0.16) between RPE and VT.
  
  
  CONCLUSIONS
  The Karvonen/HRR method failed to estimate HR-VT +/- 10% in a large percentage of patients with LVSD. There was no correlation between RPE and VT. Based on these data, exercise training intensity should ideally be prescribed based on the HR identified at VT using cardiopulmonary exercise testing in patients with LVSD.
authors.affiliation: Division of Cardiology, Department of Medicine, Northwestern University Medical School, Northwestern Memorial Hospital, Chicago, Illinois, USA. tstrzelc@nmh.org
authors.forename: T A
authors.initials: TA
authors.lastname: Strzelczyk
authors.forename: R J
authors.initials: RJ
authors.lastname: Quigg
authors.forename: P B
authors.initials: PB
authors.lastname: Pfeifer
authors.forename: M A
authors.initials: MA
authors.lastname: Parker
authors.forename: P
authors.initials: P
authors.lastname: Greenland
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005081:Exercise Therapy / Q000379:methods* / Q000592:standards; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology / Q000534:rehabilitation*