ecg

ECG / EKG

Electrocardiogram, a test that records the electrical activity of the heart.

SA node

Sinoatrial node, the natural pacemaker of the heart.

AV node

Atrioventricular node, a relay station for electrical signals between the atria and ventricles.

Bundle of His

A bundle of electrical fibers that conducts impulses from the AV node to the ventricles.

Left bundle branch

The pathway that conducts electrical signals to the left ventricle.

Right bundle branch

The pathway that conducts electrical signals to the right ventricle.

Purkinje fibres

Fibres that transmit electrical signals to the ventricular muscles causing them to contract synchronously.

Atrium (Plural: Atria)

The upper chambers of the heart (left and right atrium).

Ventricle (Plural: Ventricles)

The lower chambers of the heart (left and right ventricle).

P wave

The first small wave on an ECG representing atrial electrical activity and contraction.

QRS complex

A large complex waveform on an ECG representing ventricular depolarization and contraction.

Q wave

The first downward deflection in the QRS complex.

R wave

The peak upward wave of the QRS complex.

S wave

The downward wave following the R wave in the QRS complex.

T wave

A rounded wave following the QRS complex, representing ventricular repolarization.

U wave

A small wave following the T wave, which may become prominent in hypokalemia.

PR interval

The time interval from the start of the P wave to the start of the Q wave, indicating conduction time from the SA node to the AV node.

QRS duration

The width of the QRS complex representing the time taken for ventricular depolarization.

QT interval

The time period from the start of the QRS to the end of the T wave, representing the duration of ventricular electrical activity.

ST segment

The flat section of the ECG from the end of the QRS complex to the start of the T wave, indicative of myocardial ischemia if elevated or depressed.

ST elevation

Indicates acute myocardial infarction.

ST depression

Indicates myocardial ischemia.

Sinus rhythm

A normal heart rhythm originating from the SA node.

Sinus tachycardia

A sinus rhythm with a heart rate exceeding 100 beats per minute.

Sinus bradycardia

A sinus rhythm with a heart rate less than 60 beats per minute.

Arrhythmia

An irregular heartbeat caused by abnormal electrical activity.

AF / Atrial Fibrillation

Atrial fibrillation, characterized by irregular P waves and an absolute irregular rhythm.

Atrial Flutter

A pattern of rapid atrial depolarization resembling sawtooth waves.

PVC

Premature Ventricular Contraction, where the ventricles contract prematurely, seen as wide and bizarre QRS.

PAC

Premature Atrial Contraction, where the atria contract prematurely.

Heart block

A condition where electrical signals are slowed or interrupted as they pass through the heart.

1st degree heart block

A first-degree heart block characterized by a prolonged PR interval.

2nd degree heart block

A second-degree heart block where some atrial signals do not reach the ventricles.

3rd degree heart block

A third-degree heart block (complete block) where the atria and ventricles beat independently.

Asystole

Cardiac arrest with no electrical activity; a flatline on the ECG.

VF / Ventricular Fibrillation

A chaotic electrical activity that prevents effective pumping of blood; requires immediate defibrillation.

VT / Ventricular Tachycardia

A rapid succession of wide QRS complexes indicating a potentially dangerous heart rhythm.

Defibrillation

An electrical shock used to terminate ventricular fibrillation or tachycardia.

Cardiac cycle

The sequence of events in one complete heartbeat including contraction and relaxation of the atria and ventricles.

Polarisation

The resting electrical state of myocardial cells.

Depolarisation

The process of electrical activation leading to myocardial contraction.

Repolarisation

The restoration of the resting state of myocardial cells following contraction.

Ischemia

Insufficient blood supply to the heart muscle, indicated by ST segment changes.

Myocardial Infarction (MI)

Heart muscle death due to prolonged ischemia, typically evidenced by ST elevation or pathological Q waves.