The Role of the ECG in Diagnosis, Risk Estimation, and Catheterization Laboratory Activation in Patients with Acute Coronary Syndromes: A Consensus Document

Abstract

The electrocardiogram (ECG) is the most widely used imaging tool helping in diagnosis and initial management of patients presenting with symptoms compatible with acute coronary syndrome. Acute ischemia affects the configuration of the QRS complexes, the ST segments and the T waves. The ECG should be read along with the clinical assessment of the patient. ST segment elevation (and ST depression in leads V 1 -V 3 ) in patients with active symptoms usually indicates acute occlusion of an epicardial artery with ongoing transmural ischemia. These patients should be triaged for emergent reperfusion therapy per current guidelines. However, many patients have ST segment elevation secondary to nonischemic causes. ST depression in leads other than V 1 -V 3 usually are indicative of subendocardial ischemia secondary to subocclusion of the epicardial artery, distal embolization to small arteries or spasm supply/demand mismatch. ST depression may also be secondary to nonischemic etiologies, such as left ventricular hypertrophy, cardiomyopathies, etc. Knowing the clinical scenario, comparison to previous ECG and subsequent ECGs (in cases that there are changes in the quality or severity of symptoms) may add in the diagnosis and interpretation in difficult cases. This review addresses the different ECG patterns, typically seen in patients with active symptoms, after resolution of symptoms and the significance of such changes when seen in asymptomatic patients. Ann Noninvasive Electrocardiol 2014;19(5):412-425noninvasive techniques-electrocardiography; Acute coronary syndrome; ischemia; ST elevation; ST depression; myocardial infarctionThe electrical activity of the heart, as depicted by the surface electrocardiogram (ECG) is affected by ischemia, reperfusion and presence of necrosis or scar. Therefore, the ECG has remained the most widely utilized ancillary tool, along with focused history taking and physical examination,

2017 ISHNE-HRS expert consensus statement on ambulatory ECG and external cardiac monitoring/telemetry

“…Ambulatory ECG monitoring can be utilized to diagnose the etiology of chest pain (both atherosclerotic coronary artery disease and Prinzmetal's variant angina), identify episodes of atypical chest pain that do not have an apparent manifestation on the surface ECG, and assess the magnitude of "ischemic burden," the product of duration of ischemia and the magnitude of ST-segment depression. The majority of episodes of ambulatory ischemia in patients with coronary disease are asymptomatic, and therefore objective ECG monitoring, such as with the AECG, can be used to identify the severity of ischemia during daily activities (Birnbaum et al, 2014).…”

“…Ambulatory ECG monitoring has also been utilized to diagnose and manage patients with the rare syndrome of Prinzmetal's variant angina, but confirmation of adequate therapeutic prevention of vasospasm episodes has been primarily based on provocative testing in the cardiac catheterization laboratory (Bay es de Luna et al, 2014;Waters, Szlachcic, Theroux, Dauwe, & Mizgala, 1981).…”

Clinical Significance of Upsloping ST Depression on Resting Electrocardiogram

“…Later on, Nikus et al described a patient with acute myocardial infarction secondary to left circumflex subocclusion that presented with similar ECG pattern of upsloping ST depression . It has also been described that patients presenting with such an ECG pattern may progress to typical ST elevation myocardial infarction . Recently, a consensus document recommended that this pattern, if seen in a patient with suggestive ongoing symptoms and without tachycardia, should be considered as an indication for urgent reperfusion therapy by percutaneous coronary intervention …”

Acute Coronary Syndromes: Introduction and Pathophysiologic Classification

“…When ischemia is confi ned primarily to the subendocardium, the overall ST vector typically faces the inner ventricular layer and the ventricular cavity such that the surface ECG leads show ST depression [ 11 ]. This subendocardial ischemic pattern is a frequent fi nding during spontaneous episodes of rest angina such as appears during ischemic imbalance.…”