Role of the ECG in initial acute coronary syndrome triage: primary PCI regardless presence of ST elevation or of non-ST elevation

Abstract

The major initial triaging decision in acute coronary syndrome (ACS) is whether or not percutaneous coronary intervention (PCI) is the primary treatment. Current guidelines recommend primary PCI in ST-elevation ACS (STEACS) and initial antithrombotic therapy in non-ST-elevation ACS (NSTEACS). This review probes the question whether this decision can indeed be based on the ECG. Genesis of STE/NSTE ECGs depends on the coronary anatomy, collateral circulation and site of the culprit lesion. Other causes than ischaemia may also result in ST-segment changes. It has been demonstrated that the area at risk cannot reliably be estimated by the magnitude of the ST change, that complete as well as incomplete occlusions can cause STE as well as NSTE ECGs, and that STE and NSTE patterns cannot differentiate between transmural and non-transmural ischaemia. Furthermore, unstable angina can occur with STE and NSTE ECGs. We conclude that the ECG can be used to assist in detecting ischaemia, but that electrocardiographic STE and NSTE patterns are not uniquely related to distinctly different pathophysiological mechanisms. Hence, in ACS, primary PCI might be considered regardless of the nature of the ST deviation, and it should be done with the shortest possible delay, because 'time is muscle'.

Fig. 1

STE and NSTE acute coronary syndrome (STEACS and NSTEACS) are syndromes without a sharp contrast: properties overlap and differences are gradual. Prevalence: NSTEACS occurs slightly more often than STEACS [44]; multivessel disease: NSTEACS patients have slightly more often multivessel disease [44]; infarct-related artery occluded: this occurs more often in STEACS patients but also in a considerable percentage of NSTEACS patients [, –31]; transmural infarction: this occurs more often in STEACS patients but also in a considerable percentage of NSTEACS patients [12]; ECG after 3 min of balloon occlusion: in elective PCI, only a slight majority of ECGs after 3 min of complete occlusion shows ST elevation [17]