CORRESPONDENCE: LETTER TO THE EDITOR
Value of a High Exercise Workload to Rule Out Myocardial Ischemia
Alberto Bouzas-Mosquera, MD*,
Jesús Peteiro, MD, PhD and
Nemesio Álvarez-García, MD
* Department of Cardiology, Hospital Universitario A Coruña, As Xubias, 84, 15006 A Coruña, Spain (Email: aboumos{at}canalejo.org).
We read with great interest the paper by Bourque et al. (1) regarding the value of a high exercise workload to rule out significant myocardial ischemia. In that study, only 2 (0.4%) of 473 patients reaching  10 metabolic equivalents (METs) and 85% of maximum age-predicted heart rate (MAPHR) had 10% left ventricular ischemia on myocardial perfusion imaging. Furthermore, of the 430 patients reaching 10 METs and 85% MAPHR without exercise-induced ST-segment depression, none had significant myocardial ischemia. These results suggest that the information provided by cardiac imaging in these patients is questionable.
Our group previously assessed the prevalence and prognostic value of myocardial ischemia on exercise echocardiography in a population of 1,433 patients with known or suspected coronary artery disease achieving a high exercise workload (defined as 10 METs in men and 8 METs in women) (2). Of them, in 437 (30%) patients, new or worsening wall motion abnormalities developed during exercise. Over a follow-up of 2.3 ± 1.5 years, 201 (14%) patients underwent coronary revascularization and 57 (4%) patients had a hard cardiac event. Furthermore, exercise echocardiography was shown to provide incremental value for predicting hard cardiac events in these patients.
It might be argued that, in this study, 19% of the patients failed to achieve >85% of MAPHR, and ST-segment changes during the tests developed in 14% of the patients. Thus, we further explored whether the findings obtained by Bourque et al. (1) would replicate in a population of patients fulfilling the criteria used in their study. We recently evaluated 4,004 patients with interpretable electrocardiograms undergoing treadmill exercise echocardiography in whom chest pain or ischemic electrocardiographic changes during exercise did not develop (3). Applying the criteria used in the study by Bourque et al. (1) to this population would yield 2,005 patients who achieved both 10 METs and >85% of MAPHR. Of them, new or worsening wall motion abnormalities developed in 301 (15%) patients, 187 (9.3%) patients had ischemia involving at least 3 myocardial segments, and 138 (6.9%) patients underwent coronary revascularization. Thus, these results do not suggest that a high exercise workload may confidently rule out myocardial ischemia or significant coronary artery disease in our patients. It is important to point out that images were acquired at peak exercise, which enhanced the sensitivity of the tests (4).
Although patients achieving a high exercise workload undoubtedly have a better prognosis, a correct diagnosis is still desirable, even when coronary revascularization is not deemed necessary. It would be interesting to validate the results obtained by Bourque et al. (1) at other institutions, with different noninvasive imaging modalities, and using cardiac events or coronary angiography results as end points.
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1. Bourque JM, Holland BH, Watson DD, Beller GA. Achieving an exercise workload of 10 metabolic equivalents predicts a very low risk of inducible ischemia: does myocardial perfusion imaging have a role? J Am Coll Cardiol 2009;54:538-545.[Abstract/Free Full Text]2. Peteiro J, Monserrat L, Bouzas B, Mariñas J, Castro-Beiras A. Risk stratification by treadmill exercise echocardiography in patients with excellent exercise capacity Echocardiography 2007;24:385-392.[CrossRef][Web of Science][Medline] 3. Bouzas-Mosquera A, Peteiro J, Alvarez-García N, et al. Prediction of mortality and major cardiac events by exercise echocardiography in patients with normal exercise electrocardiographic testing J Am Coll Cardiol 2009;53:1981-1990.[Abstract/Free Full Text] 4. Peteiro J, Garrido I, Monserrat L, Aldama G, Calvino R, Castro-Beiras A. Comparison of peak and postexercise treadmill echocardiography with the use of continuous harmonic imaging acquisition J Am Soc Echocardiogr 2004;17:1044-1049.[CrossRef][Web of Science][Medline]
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