Future cardiac events in patients with ischemic ECG changes during adenosine infusion as a myocardial stress agent and normal cardiac scan

BACKGROUND: We sought to determine the prognostic importance of adenosine-induced ischemic ECG changes in patients with normal single-photon emission computed tomography myocardial perfusion images (MPI). PATIENTS AND METHODS: We carried out a retrospective analysis of 765 patients undergoing adenosine MPI between January 2013 and January 2015. Patients with baseline ECG abnormalities and/or abnormal scan were excluded. RESULTS: Overall, 67 (8.7%) patients had ischemic ECG changes during adenosine infusion in the form of ST depression of 1 mm or more. Of these, 29 [43% (3.8% of all patients)] had normal MPI (positive ECG group). An age-matched and sex-matched group of 108 patients with normal MPI without ECG changes served as control participants (negative ECG group). During a mean follow-up duration of 33.3±6.1 months, patients in the positive ECG group did not have significantly more adverse cardiac events than those in the negative ECG group. One (0.9%) patient in the negative ECG group had a nonfatal myocardial infarction (0.7% annual event rate after a negative MPI). Also in this group, two (1.8%) patients admitted with a diagnosis of CAD where they have been ruled out by angiography. A fourth case in this, in the negative ECG group, was admitted because of heart failure that proved to be secondary to a pulmonary cause and not CAD. A case only in the positive ECG group was admitted as a CAD that was ruled out by coronary angiography. CONCLUSION: Patients with normal myocardial perfusion scintigraphy in whom ST-segment depression develops during adenosine stress test appear to have no increased risk for future cardiac events compared with similar patients without ECG evidence of ischemia.