Validity of exponential exercise protocol and Q-T dispersion in detecting myocardial ischemia

Abstract

When a patient is going to perform an exercise test and unable to complete moderate levels of exercise or reach at least 85 to 90 perccn t of age predicted maximum heart rate, the level of exercise performed may be inadequate to test cardiac reserve. Thus, ischemic ECG changes may not be evoked and the test may be non-diagnostic. The disadvantages of Bruce protocol and others arc the relatively large increase in O consumption between stages and they may be too demanding for those with limited exercise capacity and too long for those with high exercise capacity. The potential advantage of the standardized exponential exercise protocol (STEEP) is that it is suitable for a wide rang of patients. QT & QTc dispersions are considered non-invasive parameters for detecting myocardial ischemia and ventricular arrhythmias. The increase in the QT & QTc dispersion with exercise test is a landmark for myocardial ischemia.

Our study aimed at evaluation of thc safcty, applicability, and validity of STEEP in IHD, as well as evaluation of thc QT dispersion as a parameter of ischemia during exercise protocols.

The study was conducted on 50 patients referred to the cardiology department in Minia university hospital for evaluation of chest pain of suspected myocardial ischemic origin. They were 40 males with a mean age of 47.27 ± 8.11 years, and 10 females with a mean age of 46.6±8.23 years.

All patients in the study were subjected to the following:

1. Full history taking and clinical examina lion 2. Resting 12-leads electrocardiograms 3. Plain X-ray of the chest & heart, postero-anterior and lateral views