Downstream Imaging Studies Do Not Significantly Improve Outcome in Most Patients with Chest Pain Who Did Not Reach Their Target Heart Rate on a Stress ECHO Study

Abstract

Echocardiographic stress tests are often used to evaluate patients who complain of chest pain. However, some patients fail to reach the target heart rate required for the test to be conclusive (usually defined as 85% of the predicted maximal heart rate based on the patient’s age) and are often sent for additional imaging tests, such as myocardial perfusion imaging (MPI) or cardiac computed tomography angiography (CTA). Few studies have evaluated the effectiveness of these additional tests in patients who present with chest pain but did not meet the heart rate requirements for a stress test. The primary objective of the study was to evaluate the efficacy of additional imaging tests for patients who experience chest pain during daily activities but are unable to reach the target heart rate currently required for an echocardiographic stress test. The study group included 415 consecutive patients who underwent a stress echocardiogram, did not achieve their target heart rate, and did not demonstrate abnormal changes during the test. The control group consisted of 415 consecutive patients who did reach their target heart rate and demonstrated no signs of ischemia. Demographic and clinical data, medication use, imaging test results (MPI, CTA, and/or coronary catheterization) and documented cardiac events that occurred during 1 year of follow-up were obtained from the electronic medical records. Of the 415 patients in the study group, 73 (17.6%) were referred to another imaging test within 12 months. Of these 73 patients, 59 underwent MPI and 14 underwent cardiac CTA. In 12 of these patients (16.4%) the test was considered to be abnormal, but only 7 patients (1.7%) subsequently underwent a percutaneous intervention (PCI). In the control group, 28 (6.7%) patients were referred for another imaging test. Of these 28 patients, 14 underwent MPI and 14 underwent cardiac CTA. None of these tests were found to be abnormal, but two patients (0.5%) underwent a PCI (p = 0.2 between groups). There were no deaths during the study period and no patients underwent bypass surgery. The majority of the patients who underwent PCI had additional clinical risk factors (diabetes, hypertension, and/or known coronary artery disease), had taken a beta blocker within 24 h prior to the test, and/or did not reach a heart rate above 78% of their target heart rate. Our study suggests that in most patients with chest pain who do not show ischemic changes on a stress echocardiogram, additional imaging studies can be safely deferred, even if the required target heart rate was not reached. However, in patients with diabetes and/or known coronary disease, those who took a beta blocker 24 h prior to the test, or those who did not achieve a heart rate above 78% of the current target heart rate, additional imaging studies should be considered.