Detection of transient regional myocardial ischemia using body surface Delta map in patients referred for myocardial perfusion imaging--a pilot study.

Background: The diagnosis of transient regional myocardial ischemia (TRMI) in patients presenting with stable chest pain is a challenge. Exercise Tolerance Test (ETT) is no longer recommended in most cases due to its flaws. Alternative tests are more expensive and less readily available. The BSM Delta map is an intuitive color display of digitally subtracted ST-segment shift derived from two 80-electrode BSM recordings at baseline and at peak stress, and has shown promise as a tool for detection of TRMI.

Objectives: The purpose of this pilot study was to assess the feasibility of BSM Delta map as a tool to detect TRMI using dobutamine stress ECG gated single-photon emission computed tomography myocardial perfusion imaging (MPI) as a reference.

Method: Forty consecutive patients were recruited who were referred for MPI with a history of angina-like symptoms. The BSM Delta map was derived from two 80-electrode body surface mapping system recordings carried out simultaneously with MPI at (a) baseline and (b) peak dobutamine stress. Standard 12-lead ECGs were also recorded at the same time points.

Results: The mean patient age was 68±7.1years, and 52% (21/40) were female. Using MPI as the reference the sensitivity of BSM Delta map was 82% (9/11) and specificity was 86% (25/29) (95% CI 0.688-0.992), positive likelihood ratio 5.93 (95% CI 2.29-15), negative likelihood ratio 0.21 (95% CI 0.06-0.75). The sensitive of the 12-lead ECG was 36% (4/11) and specificity was 76% (22/29) (95% CI 0.356-0.767), positive likelihood ratio 1.51 (95% CI 0.55-4.15), negative likelihood ratio 0.84 (95% CI 0.51-1.37). BSM Delta map is more sensitive and specific (McNemar's chi-square test p=0.03 (95% CI, 0.448-0.924). The PPV and NPV for BSM Delta map were 69% (9/13) and 93% (25/27) respectively, compared with 36% (4/11) and 76% (22/29) for 12-lead ECG.

Conclusion: This pilot study confirms the feasibility of using Delta map in this context and suggests that it has promising diagnostic accuracy and is superior to the 12-lead ECG. It could potentially represent a clinically suitable screening tool for TRMI in patients presenting with stable chest pain, since it is near patient and requires little specialist training for acquisition and interpretation. A larger clinical study is now required.