Last Updated: 2007-08-22 16:14:25 -0400 (Reuters Health)

NEW YORK (Reuters Health) – In patients with ischemic heart disease, prolonged exercise-induced myocardial ischemia may be relatively innocuous, according to findings published in the July issue of the European Heart Journal.

Current guidelines suggest that exercise training intensity in patients with ischemic heart disease should remain below the threshold for myocardial ischemia, the authors explain, but this may prevent some patients from deriving the benefits of more intense exercise.

Dr. Peter Bogaty and colleagues from Laval University, Ste-Foy, Quebec, Canada evaluated the consequences of intense and prolonged exercise training above the threshold for myocardial ischemia versus training at current guidelines in 22 patients with ischemic heart disease.

Mean ST-segment depression ranged from 1.0 to 2.1 mm during the ischemic training sessions, the authors report, and only isolated premature ventricular contractions were observed during exercise.

None of the patients in the ischemic or control groups experienced elevations of cardiac troponin T, the report indicates, and there were no differences in the occurrence of supraventricular and ventricular arrhythmias on 24-hour Holter monitoring before and after 3 sessions (6 weeks) of 60 minutes of endurance training.

Ventricular function did not change significantly after at least 6 weeks of training, the researchers note, and there were only minimal changes in exercise tests.

"To our knowledge," the investigators say, "this is the first reported study demonstrating that, in patients with stable ischemic heart disease, prolonged and repeated exercise, which induces myocardial ischemia under controlled conditions, is not deleterious and can be well tolerated."

"This study encouragingly suggests that ischemic exercise training can be safely investigated in an appropriate environment to determine whether it may confer greater cardioprotective and physiological benefits than more standard less-intensive exercise programs in patients with coronary artery disease," Dr. Bogaty and colleagues conclude.

"The authors are to be congratulated in performing a careful study that achieved the ambitious objective of allocating patients to two exercise training regimes," write Dr. Michael S. Marber and associates from King’s College London, UK in a related editorial.

"Unfortunately, despite heroic efforts, the predicted benefits of prolonged ischemia were not apparent," the editorial concludes. "Thankfully, neither were the risks. However, neither risk nor benefit can be adequately assessed without a larger equally well-controlled follow-on study."

Eur Heart J 2007;28:1559-1565,1543-1544.