What is an electrocardiogram (ECG)?

From the Guidelines

An electrocardiogram (ECG or EKG) is a crucial medical test for recording the electrical activity of the heart, and it should be performed as a standard of care in patients with suspected cardiac disease or dysfunction, as recommended by the American College of Cardiology and the American Heart Association 1.

Importance of ECG

The ECG is essential for diagnosing various heart conditions, including arrhythmias, heart attacks, electrolyte imbalances, and structural abnormalities. It works by placing electrodes on the skin that detect electrical changes resulting from cardiac muscle depolarization and repolarization during each heartbeat. A standard ECG uses 12 leads (10 electrodes) to provide different views of the heart's electrical activity.

Procedure and Interpretation

The test produces waveforms that represent different phases of the heartbeat: P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization). ECGs are interpreted by measuring intervals between waves, examining wave morphology, and analyzing the heart's rhythm and rate, providing valuable diagnostic information about cardiac function. For accurate results, patients should remain still during recording, avoid caffeine before the test, and inform their healthcare provider about medications they're taking as some can affect ECG readings.

Clinical Applications

ECGs are used in various clinical settings, including the diagnosis of cardiac arrhythmias, acute myocardial ischemic syndromes, and conduction disorders. They are also used to monitor patients treated with antiarrhythmic and other drugs, in the preoperative assessment of patients undergoing noncardiac surgery, and in screening individuals in high-risk occupations. According to the American Heart Association, the ECG is indispensable for the diagnosis and prompt initiation of therapy in patients with acute coronary syndromes and is the most accurate means of diagnosing intraventricular conduction disturbances and arrhythmias 1.

Key Points

• ECG is a standard of care in patients with suspected cardiac disease or dysfunction
• Essential for diagnosing heart conditions, including arrhythmias, heart attacks, and structural abnormalities
• Procedure is quick, non-invasive, and painless
• Accurate results require patients to remain still, avoid caffeine, and inform healthcare providers about medications
• ECGs are interpreted by measuring intervals, examining wave morphology, and analyzing heart rhythm and rate
• Used in various clinical settings, including diagnosis, monitoring, and screening.

From the Research

ECG and Myocardial Infarction

• The relationship between ECG signs and myocardial infarction has been studied extensively, with a focus on conduction disturbances and arrhythmias 2, 3, 4.
• Heart blocks may occur as complications of acute myocardial infarction (AMI) and are accompanied by increased in-hospital mortality, with a prevalence of 15.8% in one study 2.
• The development of heart blocks was more common among patients treated with thrombolytic therapy and was associated with a significantly lower left ventricular ejection fraction 2.

ECG Patterns and Occlusion Myocardial Infarction

• Recent studies have highlighted the importance of ECG patterns in identifying occlusion myocardial infarction, with a focus on distinguishing it from non-occlusion myocardial infarction (NOMI) 5.
• The emerging paradigm of occlusion myocardial infarction seeks to enhance diagnostic accuracy and prognostic effect in acute coronary syndrome care, with an emphasis on specific ECG patterns linked to acute coronary occlusion 5.
• The traditional STEMI/NSTEMI binary framework has limitations, and the new approach proposes a revised framework that could enhance triage accuracy and treatment strategies for acute coronary syndrome 5.

Arrhythmias and Conduction Disturbances

• Almost any rhythm disturbance can be associated with acute myocardial infarction, including bradyarrhythmias, supraventricular tachyarrhythmias, ventricular arrhythmias, and atrioventricular block 4.
• The occurrence of PR segment displacements on the admission ECG may predict the risk of developing supraventricular arrhythmias during hospitalization for myocardial infarction 3.
• Thrombolytic therapy may be related to some rhythm disturbances in patients with acute myocardial infarction, and the treatment of arrhythmias and conduction disturbances is an important aspect of acute coronary syndrome management 4.