The significance of early post-exercise ST segment normalization.

Background: The persistence of ST segment depression in recovery signifies a strongly positive exercise treadmill test (ETT). However, it is unclear if early recovery of ST segments portends a similar prognosis. We sought to determine if persistence of ST depression into recovery correlates with ischemic burden based on myocardial perfusion imaging (MPI).

Methods: This was a retrospective analysis of 853 consecutive patients referred for exercise MPI at a tertiary academic center over a 24-month period. Patients were stratified into three groups based on the results of the ETT: normal (negative ETT), persistence (positive ETT with >1mm ST segment depression at 1minute in recovery) and early normalization (positive ETT with <1mm ST segment depression at 1minute in recovery). Summed stress scores (SSSs) were calculated then for each patient, while the coronary anatomy was reported for the subset of patients who received coronary angiograms.

Results: A total of 513 patients had a negative ETT, 235 patients met criteria for early normalization, while 105 patients met criteria for persistence. The persistence group had a significantly greater SSS (8.48±7.77) than both the early normalization (4.34±4.98, p<0.001) and normal (4.47±5.31, p<0.001) groups. The SSSs of the early normalization and normal groups were not statistically different and met the prespecified non-inferiority margin (mean difference 0.12, -0.66=lower 95% CI, p<0.001). Among the 87 patients who underwent an angiogram, significant three-vessel or left main disease was seen in 39.3% of the persistence group compared with 5.9% of normal and 7.4% of early normalization groups.

Conclusion: Among patients with an electrically positive ETT, recovery of ST segment depression within 1minute was associated with a lower SSS than patients with persistence of ST depression beyond 1minute. Furthermore, early ST segment recovery conferred a similar SSS to patients with a negative ETT. These results suggest that among patients evaluated for chest pain with a positive ETT, early recovery of the ST segment during recovery is associated with a significantly less ischemic burden on subsequent MPI and thus may represent a false positive finding in exercise treadmill testing.