Abstract
BackgroundThe acute coronary syndrome diagnosis includes different classifications of myocardial infarction, which have been shown to differ in their pathology, as well as their early and late prognosis. These differences may relate to the underlying extent of infarction and/or residual myocardial ischemia. The study aim was to compare scar and ischemia mass between acute non-ST elevation myocardial infarction (NSTEMI), ST-elevation MI with Q-wave formation (Q-STEMI) and ST-elevation MI without Q-wave formation (Non-Q STEMI) in-vivo, using cardiovascular magnetic resonance (CMR).Methods and resultsThis was a prospective cohort study of twenty five consecutive patients with NSTEMI, 25 patients with thrombolysed Q-STEMI and 25 patients with thrombolysed Non-Q STEMI. Myocardial function (cine imaging), ischemia (adenosine stress first pass myocardial perfusion) and scar (late gadolinium enhancement) were assessed by CMR 2–6 days after presentation and before any invasive revascularisation procedure. All subjects gave written informed consent and ethical committee approval was obtained. Scar mass was highest in Q-STEMI, followed by Non-Q STEMI and NSTEMI (24.1%, 15.2% and 3.8% of LV mass, respectively; p < 0.0001). Ischemia mass showed the reverse trend and was lowest in Q-STEMI, followed by Non-Q STEMI and NSTEMI (6.9%, 14.7% and 19.9% of LV mass, respectively; p = 0.012). The combined mass of scar and ischemia was similar between the three groups (p = 0.17). The ratio of scar to ischemia was 3.5, 1.0 and 0.2 for Q-STEMI, Non-Q STEMI and NSTEMI, respectively.ConclusionPrior to revascularisation, the ratio of scar to ischemia differs between NSTEMI, Non-Q STEMI and Q-STEMI, whilst the combined scar and ischemia mass is similar between these three types of MI. These results provide in-vivo confirmation of the diverse pathophysiology of different types of acute myocardial infarction and may explain their divergent early and late prognosis.
Highlights
The acute coronary syndrome diagnosis includes different classifications of myocardial infarction, which have been shown to differ in their pathology, as well as their early and late prognosis
Q-waves on an electrocardiogram develop in approximately two thirds of ST-elevation myocardial infarction (STEMI), largely dependent on infarct size, but Q-wave development is rare after nonST elevation myocardial infarction (NSTEMI) [7,8,9,10]
Biomarkers of myocardial damage were significantly lower in the NSTEMI compared with the Non-Q STEMI and Q-STEMI groups (Table 2)
Summary
The acute coronary syndrome diagnosis includes different classifications of myocardial infarction, which have been shown to differ in their pathology, as well as their early and late prognosis These differences may relate to the underlying extent of infarction and/or residual myocardial ischemia. Whether myocardium supplied by the infarct-related artery remains at risk of further ischemia following acute myocardial infarction (MI) depends largely on the presence of a flow-limiting lesion in the culprit vessel. The combined mass of scar and ischemia represents the total myocardium at risk and should be similar between different types of MI. These basic concepts have not been fully studied in-vivo. Similar comparisons between STEMI and NSTEMI have not been undertaken and quantitative comparisons of scar and ischemia mass are not available
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