Identifying Target Heart Rate In Patients With Ischemic Heart Disease Without An Exercise Stress Test

Abstract

Increasingly, patients enroll in cardiac rehabilitation without an exercise stress test, yet there are few evidence-based recommendations for establishing a target heart rate (HR) in this situation among patients with heart disease. PURPOSE In patients with ischemic heart disease, identify and compare the % of measured HR reserve when target HR is prescribed using resting HR plus 20 and at 65% of HR reserve calculated using a population-specific maximum HR prediction equation. METHODS We queried the Henry Ford Preventive Cardiology Outcomes (PRECO) database for patients with a history of myocardial infarction or revascularization procedure; preserved left ventricular function; age= 40–80 yr; sinus rhythm; and a graded treadmill test with a respiratory exchange ratio ≥1.10. Beginning May 2001, consecutive tests of 50 patients prescribed beta-adrenergic blockade (BB) therapy and 46 without BB were included. Percent measured HR reserve associated with resting HR plus 20 was calculated. HR at a moderate exercise intensity (65% HR reserve) was calculated using a predicted maximum HR [HRmax=164–0.72×Age (with BB) or HRmax=200–0.92×Age (no BB)]. RESULTS Mean % measured HR reserve based on resting HR plus 20 was 45±30% (mean±SD) and 31±12% for the BB and no BB patients, respectively. Mean % measured HR reserve using predicted maximum HR was 75±46% and 68±21% for the BB and no BB patients, respectively. Resting HR plus 20 resulted in a target HR that was < 40 % of measured HR reserve in 58% (29/50) of the patients on BB and 83% (38/46) of those without BB. Other results are shown in Table.TableCONCLUSIONS Among patients with ischemic heart disease: 1) A target HR based on resting HR plus 20 results in a suboptimal exercise intensity (< 40 % HR reserve) in over half of the patients, independent of the presence of BB therapy. 2) Target HR calculated at a moderate exercise intensity (65% HR reserve), using a population-specific maximum HR prediction equation, results in an exercise intensity that is within 50–85% measured HR reserve in 58% of the patients on BB and 72% the patients without BB.