Relation between prognosis and myocardial perfusion imaging from the difference of end-point criterion for exercise stress testing: a sub-analysis of the J-ACCESS study.

Background: The presence and severity of coronary artery disease may be underestimated in patients who do not reach significant end-points of stress testing during myocardial perfusion imaging. We examined how the effect of the level of exercise may affect the ability of the quantitative gated single-photon emission computed tomography (SPECT) imaging to predict the future cardiac events (cardiac death, non-fatal myocardial infarction and severe heart failure).
Method: Of the 4629 consecutively registered patients for J-ACCESS (Japanese-assessment of cardiac event and survival study by quantitative gated SPECT), 2821 patients who underwent the exercise test were selected, and divided into two groups, which reached a target heart rate (group; n=925) or not (n=1896). Leg fatigue was the most common reason for stopping the exercise test in non-reaching groups, we conducted a study comparing group with leg fatigue group (group II).
Results: During a 3-year follow-up period, total of 25 cardiac events (2.7%) occurred in group I and total of 73 events (3.9%) occurred in group II. The incidence of cardiac death was slightly but significantly higher in group II (P.04). A summed stress score (SSS) was able to separate the high-risk from low-risk patients in group II. The maximal heart rate was not an independent predictor for cardiac events. In Cox multivariate regression analysis, higher age (70 years), history of DM, EDV at rest and LVEF at rest were predictor of cardiac major events (cardiac death, myocardial infarction, heart failure), and higher age (70 years), ESV at rest were independent predictor of cardiac hard events (cardiac death, myocardial infarction) in group II.
Conclusion: Exercise SPECT imaging provides the useful prognostic information in patients who do not reach a significant end-point due to the leg fatigue. In such patients, those with normal SSS score and normal resting ESV have also a most favorable prognosis.
(Copyright 2010 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)