Waves

Electrocardiography (ECG/EKG)

A method that measures the electrical activity of the heart.

P wave

Represents atrial depolarization.

QRS complex

Indicates ventricular depolarization, where atrial repolarization is hidden.

T wave

Represents ventricular repolarization.

P–R interval

Time taken for an impulse to travel from atria to ventricles.

S–T segment

Indicates that the entire ventricular myocardium is depolarized.

Q–T interval

Represents the total time for ventricular depolarization and repolarization.

Atrial Depolarization Begins

when the sinoatrial (SA) node signals the atria to contract, initiating the heart's electrical conduction.

Atrial Depolarization Complete

impulse reaches the AV node, atria finish contracting and the ventricles to fill with blood, AV node delay: A brief pause allows ventricles to fill completely.

ECG Atrial Depolarization Begins

Start of the P wave

ECG Atrial Depolarization Complete

End of the P wave (flat PR segment).

Ventricular Depolarization Begins at the Apex

Depolarization spreads from the apex upward through the ventricles, causing ventricular contraction. Atrial repolarization occurs simultaneously but is hidden by the large QRS complex.

ECG Ventricular Depolarization Begins at the Apex

 QRS complex

Ventricular Depolarization Complete

The ventricles are now fully depolarized and contracting, pumping blood out to the aorta and pulmonary trunk.

ECG ventricular depolarization complete

End of the S wave, beginning of the ST segment (flat line).

Ventricular Repolarization

The ventricles repolarize (reset electrically) as K⁺ exits the cells. Allows the ventricles to relax after contraction.

ECG Ventricular Repolarization

T wave (broad, upward wave).

Ventricular Repolarization Complete

the completion of the T wave, indicating that the ventricles have fully repolarized and are preparing for the next cycle.

ECG Ventricular Repolarization Complete

End of the T wave → back to baseline.

Normal Sinus Rhythm (NSR)

a normal heartbeat rhythm originating from the sinus node, typically at a rate of 60 to 100 beats per minute.

what waves are present in the normal sinus rhythm and there functions

P wave: Present and upright before every QRS complex, PR interval: Normal (0.12–0.20 seconds), QRS complex: Normal and narrow (<0.12 seconds). 

junctional Rhythm

AV node (takes over when the sinoatrial node fails), resulting in absent or inverted P waves. slow rhythm (40–60 bpm)

Second-Degree Heart Block

signals from the atria fail to reach the ventricles, leading to dropped beats. It is characterized by an intermittent failure of conduction through the AV node.

Ventricular Fibrillation (V-Fib)

disorganized electrical activity in the ventricles, leading to ineffective pumping of blood. It can result in cardiac arrest if not treated immediately.