The T Wave is a component of the electrocardiogram (ECG) that reflects ventricular repolarization. It is a diagnostic waveform used in clinical cardiology and acute care. It is most commonly assessed on a standard 12-lead ECG and on continuous telemetry monitoring. Changes in the T Wave can signal electrolyte abnormalities, myocardial ischemia, or repolarization disorders.

The ST Segment is a portion of the electrocardiogram (ECG) tracing between the QRS complex and the T wave. It represents a phase when the ventricles are uniformly depolarized. It is a diagnostic concept used in cardiology and emergency medicine rather than an anatomic structure. It is most commonly assessed on a 12-lead ECG when evaluating chest pain, ischemia, and acute coronary syndromes.

The QRS Complex is the main spike on an electrocardiogram (ECG), also called an EKG. It represents ventricular depolarization, the electrical activation that precedes ventricular contraction. It is a diagnostic concept used in cardiology and acute care to interpret rhythm, conduction, and myocardial disease. It is commonly assessed on 12-lead ECGs, telemetry, and ambulatory monitors.

PR Interval is an electrocardiogram (ECG) measurement that reflects atrial-to-ventricular conduction time. It spans from the start of the P wave to the start of the QRS complex on the ECG tracing. It is a physiology and diagnostic-test concept used to assess the cardiac conduction system, especially atrioventricular (AV) conduction. It is commonly reviewed in routine 12-lead ECG interpretation, bradycardia evaluation, and suspected heart block.

QT Interval is an electrocardiogram (ECG) measurement that reflects ventricular depolarization plus repolarization. It is read on a diagnostic test, not a symptom or a disease by itself. It is used most often in cardiology, emergency care, and perioperative medicine to assess arrhythmia risk. It is commonly discussed when evaluating medications, electrolytes, syncope, and inherited channelopathies.

Cardiac Repolarization is the electrical “resetting” phase of heart muscle cells after they activate. It is a core concept in cardiac electrophysiology and ECG (electrocardiogram) interpretation. It is most commonly discussed when evaluating ST-segment and T-wave findings and the QT interval. It is clinically relevant in arrhythmias, ischemia, electrolyte disorders, and drug safety.

Cardiac Depolarization is the electrical activation of heart muscle that initiates contraction. It is a core physiology concept in cardiac electrophysiology and the cardiac conduction system. It is most commonly discussed when interpreting an electrocardiogram (ECG/EKG) and cardiac monitoring. It also underpins how arrhythmias form and how therapies like pacing and cardioversion work.

Purkinje Fibers are specialized cardiac conduction cells that rapidly deliver electrical impulses through the ventricles. They are part of cardiac anatomy and physiology, specifically the His–Purkinje conduction system. They are most commonly discussed when interpreting electrocardiograms (ECGs), evaluating arrhythmias, and planning electrophysiology (EP) procedures. They help explain how coordinated ventricular contraction is achieved in normal rhythm and how certain conduction disorders occur.

The Bundle of His is a short tract of specialized cardiac conduction tissue that carries electrical impulses from the atrioventricular (AV) node to the ventricles. It is part of cardiac anatomy and physiology, specifically the cardiac conduction system. Clinically, it is discussed in arrhythmias, atrioventricular block, bundle branch block, and pacing strategies. It is commonly referenced when interpreting the electrocardiogram (ECG) and during electrophysiology (EP) procedures.

AV Node is a small cluster of specialized cardiac conduction tissue that electrically connects the atria to the ventricles. It is part of cardiac anatomy and physiology within the heart’s conduction system. It is commonly discussed in electrocardiography (ECG), arrhythmias, and atrioventricular (AV) conduction blocks. It is also a key target in electrophysiology (EP) testing and some catheter ablation strategies.