Cardiovascular Division (Clinical) Michelle Albert, MD Elliott Antman, MD Donald S. Baim, MD Joshua Beckman, MD Gavin Blake, MD Charles M. Blatt, MD Eugene Braunwald, MD Christopher Cannon, MD Ming Hui Chen, MD Michael Chin, MD, PhD Mark Creager, MD Victor Dzau, MD Elazer Edelman, MD, PhD Andrew Eisenhauer, MD Laurence Epstein, MD James Fang, MD Mark Feinberg, MD Jonas Galper, MD, PhD Peter Ganz, MD J. Michael Gaziano, MD Marie Gerhard-Hermen, MD Robert Giugliano, MD Michael Givertz, MD Samuel Z. Goldhaber, MD Thomas B. Graboys, MD Howard Hartley, MD Carolyn Ho, MD Mukesh Jain, MD John Jarcho, MD Paula Johnson, MD Ralph Kelly, MD Scott Kinlay, MD Jamil Kirdar, MD James Kirshenbaum, MD Gideon Koren, MD Richard Kuntz, MD Raymond Kwong, MD Michael J. Landzberg, MD Richard Lee, MD Eldrin Lewis, MD James Liao, MD Peter Libby, MD (Division Chief) Leonard Lilly, MD Bernard Lown, MD William Maisel, MD Thomas Michel, MD, PhD David Morrow, MD Karen Moulton, MD Gilbert Mudge, MD Anju Nohria, MD Patrick O’Gara, MD Marc A. Pfeffer, MD, PhD (Editor) Jorge Plutzky, MD Jeffrey Popma, MD Shmuel Ravid, MD Frederic Resnic, MD Paul Ridker, MD Thomas Rocco, MD Campbell Rogers, MD Maria Rupnick, MD, PhD Arthur Sasahara, MD S. Dinakar Satti, MD Jay Schneider, MD Christine Seidman, MD Andrew Selwyn, MD Daniel Simon, MD Laurence Sloss, MD Kyoko Soejima, MD Regina Sohn, MD Scott Solomon, MD Lynne Stevenson, MD William Stevenson, MD Peter Stone, MD Michael Sweeney, MD Frederick Welt, MD Justina Wu, MD Brigham and Women’s Hospital Fax: (617) 732-5291Website: www.heartdoc.org The editorial content of Cardiology Rounds is determined solely by the Cardiovascular Division of Brigham and Women’s Hospital. This publication is made possible by an educational grant. A Teaching Hospital of HARVARD MEDICAL SCHOOL In the last issue of Cardiology Rounds, the value of exercise electrocardiography as a diagnostic tool for coronary artery disease was questioned because the results of this com- monly performed test may be inaccurate due to verification bias. 1,2 The issue also related how the currently accepted gold standard – coronary angiography – may also have severe inherent limitations because it is very often performed based on the outcome of exercise testing and may underestimate the burden of disease. 3 The true value of exercise electro- cardiography is in its ability to assess prognosis with markers such as exercise capacity, 4,5 heart rate response during 6 and after exercise 7,8 and the Duke Treadmill Score. 9,10 In terms of heart rate response, it has been observed in fit subjects that in the first few minutes after exercise, there is an initial steep fall in heart rate lasting about 30 seconds, followed by a shallower fall. 11 In patients with heart failure, however, there is never a steep fall. Instead, they have a shallow fall throughout recovery. It has been concluded therefore that heart rate recovery after exercise, particularly during the first 30 seconds, is closely related to vagal reactivation. 11 Because autonomic imbalances are associated with mortal- ity, 12,13 and because of the associations between exercise heart rate responses and autonomic nervous system function, it was hypothesized that measures of heart rate response in the exercise lab would be an independent predictor of mortality. 14 With this hypothesis in mind, physicians at the Cleveland Clinic followed 2,428 patients referred for exercise nuclear testing to discern if an attenuated heart rate recovery, as a manifestation of vagal tone, would be independently predictive of increased risk of mortality. 14 The results of their find- ings are outlined in Part 2 of this review on exercise testing. Heart rate recovery In the early 1990s, 2,428 patients were referred for exercise nuclear testing at the Cleveland Clinic for evaluation of known or suspected coronary disease. 14 All of the subjects were potential first-time candidates for coronary angiography. Heart rate recovery was defined as the difference in heart rate at peak exercise and that measured one minute later. It should be noted that all sub- jects underwent a cool-down period during recovery; that is, after peak exercise had been achieved, they walked slowly at a shallow grade for two minutes before stopping exercise alto- gether. Based on maximization of a log rank chi square statistic, an abnormal heart rate recovery was defined as a value of ≤ 12 beats per minute (bpm). Thus, a person achieving a peak heart rate of 160 beats per minute (bpm) would have to get his/her heart rate below 148 bpm by one minute later in order to be considered to have a normal heart rate recovery. Exercise Testing Part 2: The Value of Heart Rate Recovery BY MICHAEL S. LAUER, MD, FACC, FAHA June/July 2002 Volume 6, Issue 6 ™ Available on the Internet www.cardiologyrounds.org Available on the Internet www.cardiologyrounds.org