New ST-depression: an under-recognized high-risk category of 'complete' ST-resolution after reperfusion therapy

In the transition from fibrinolysis to primary PCI, the HERO trials help refine STEMI ECG interpretation and Q wave analysis potentially alters future management

Electrocardiogram sub-studies from the Hirulog Early Reperfusion/Occlusion 1 and 2 trials, which tested bivalirudin as an adjunctive anticoagulant to fibrinolysis in ST-elevation myocardial infarction, have contributed to the literature. The concept of using the presence of infarct lead Q waves to determine reperfusion benefit has subsequently been explored in multiple primary percutaneous coronary intervention studies. The angiographic findings before percutaneous coronary intervention combine with the baseline electrocardiogram to accurately diagnose ST-elevation myocardial infarction and evaluate its potential territory. This review discusses the relative merits of the presence of infarct lead Q waves versus time duration from symptom onset using observational data from cohorts of patients from multiple clinical trials. The presence of infarct lead Q waves at presentation has been repeatedly shown to be superior to time duration from symptom onset in determining prognosis, despite that continuous variable (time duration) statistically should be more powerful than dichotomous variable (Q wave). If quantitative or semi-quantitative measurement of Q waves correlates well with irreversible myocardial injury in vivo (a research goal of many cardiac magnetic resonance imaging studies), Q waves measurements by mirroring ST-elevation myocardial infarction evolution better than the current metric of time duration of symptoms will impact future ST-elevation myocardial infarction reperfusion management. Newer methodology will more quickly capture and transmit electrocardiogram information including infarct lead Q waves potentially before first medical contact, and help differentiate new evolving Q waves of the ongoing ST-elevation myocardial infarction from old changes. Q waves as the new metric in ST-elevation myocardial infarction reperfusion should be tested in upcoming trials.

Simplifying electrocardiographic assessment in STEMI reperfusion management: Pros and cons

Current guidelines on STEMI reperfusion management do not incorporate further electrocardiographic details over the presence of significant ST elevation. Fibrinolysis is considered an alternative therapy to primary PCI if there is a long PCI-related delay, but the 2 therapies should not be combined. Meanwhile, reperfusion for ischemic stroke has evolved on mechanistic understanding - reperfusion benefit being greatest in the patient with small "core" infarct and large ischemic "penumbra". Fibrinolysis is not regarded as an alternative to mechanical thrombectomy, and the 2 therapies can be combined. In this article describing how reperfusion regimes have evolved along different paths for STEMI and for ischemic stroke, a new concept is made that in STEMI infarct lead Q waves can be the counterpart of the "core" and ST elevation the "penumbra". Suggestions to modify STEMI treatment algorithms are made, exploring further the relative role of (pre-hospital) fibrinolysis versus PCI particularly in younger patients presenting at the onset of their STEMI (no Q waves). In contrast, some patients particularly the older ones with more evolved STEMI (large Q waves present) may be much more suited for PCI despite expecting a long delay. The article finishes by describing potential future alterations in the method of reperfusion. Despite primary PCI being the well-established therapy, there are rooms for further research to optimize STEMI outcomes.