Myocardial micro-alternation index (MMI) does not associate with the ischemic response in coronary artery disease patients

ECG dispersion mapping (ECG-DM) was one of non-invasive parameters to observe micro-electrical changes in the ECG signal. This was assessed using the Myocardial Micro-alternation Index (MMI), whose reflect abnormalities in the myocardium at a metabolic level, indicating ischemia, based on small-invasive test. Until now there has been no study that specifically examines the ischemic response to MMI in the coronary artery disease (CAD) population. Finding ischemic with treadmill test still frequently performed in our daily practice due to lack availability and feasibility of imaging test, and somehow the specificity of the test is moderately-high and similar with imaging test.

Aim to determine the association between Myocardial Micro-alternation Index (MMI) and the ischemic response in CAD patients.

This was a cross-sectional observational study done in Tertiary General Hospital. Subjects included were 18-79 years old patients who were hospitalized with CAD in 6 months to 2 years prior, either because of acute coronary syndrome or underwent elective revascularization procedures (primary coronary intervention/PCI or coronary artery bypass graft/CABG). All patients were assessed for ECG dispersion mapping with 3-minute recordings. The ECG dispersion mapping was analyzed by the system and reported as MMI. Ischemic response was obtained for treadmill test results with maximal test or symptom limited protocol. Positive or suggestive ischemic response was defined by ST-depression more than 0.05 mv if downslope or horizontal, or 0.1mv if upsloping, in minimal two leads and in three consecutive beats.

Among 68 patients included in this study, two was excluded due to inability to perform exercise test. Form 66 patients, 58 (87.9%) were men and the mean age was 57 ± 10.2 years. The median of MMI was 18 (1-61)%. Twenty-four patients (36.4%) had a positive or suggestive ischemic response, while the rest was negative. The median of MMI in positive ischemic was 18 (1-52)% and in the negative ischemic response was 18 (14-61)%. The Mann-Whitney analysis showed that there were no associations between MMI and ischemic response (p 0.707).

There are no associations between Myocardial micro-alternans index with ischemic response in patients with chronic stable coronary artery disease patients. The utility of MMI to predict ischemia might need imaging test to confirm.

ECG Positive Ischemic Response