Understanding EKG Intervals and Segments 1

Understanding EKG Intervals and Segments 2

The Basics of EKG

An electrocardiogram (EKG) is a test that measures the electrical activity of the heart. It is a valuable tool in diagnosing and monitoring heart conditions. The EKG waveform consists of several intervals and segments, each representing a different phase of the cardiac cycle. Understanding these intervals and segments is crucial for interpreting EKG results accurately.

P Wave

The P wave is the first deflection on the EKG waveform and represents atrial depolarization. It indicates the initiation of the electrical impulse in the atria, which leads to atrial contraction. The P wave should be upright and usually lasts around 0.06 to 0.12 seconds in duration. Unearth further specifics about the topic with this external source. EKG practice test, broaden your understanding of the subject.

PR Interval

The PR interval begins at the end of the P wave and ends at the beginning of the QRS complex. It represents the time it takes for the electrical impulse to travel from the atria to the ventricles. The PR interval normally lasts between 0.12 to 0.20 seconds. Prolongation of the PR interval may indicate an AV conduction delay or blockage.

QRS Complex

The QRS complex is the largest deflection on the EKG waveform and represents ventricular depolarization. It consists of three distinct waves: Q, R, and S. The Q wave is the first negative deflection after the PR interval, the R wave is the first positive deflection after the Q wave, and the S wave is the first negative deflection after the R wave. The QRS complex normally lasts for approximately 0.06 to 0.10 seconds.

ST Segment

The ST segment is the interval between the end of the QRS complex and the beginning of the T wave. It represents the early part of ventricular repolarization. Normally, the ST segment is isoelectric (at the same level as the baseline). Deviations from the baseline can indicate myocardial ischemia or injury.

T Wave

The T wave follows the ST segment and represents ventricular repolarization. It is typically a positive deflection on the EKG waveform. The duration and morphology of the T wave can provide valuable information about the heart’s electrical activity and potential abnormalities.

QT Interval

The QT interval begins at the beginning of the QRS complex and ends at the end of the T wave. It represents the duration of ventricular depolarization and repolarization. The QT interval varies depending on the heart rate, so it is often corrected for rate using formulas such as the Bazett’s formula. Prolongation of the QT interval can predispose individuals to life-threatening arrhythmias, such as Torsades de Pointes.

U Wave

The U wave is a small, rounded deflection that may follow the T wave. Its exact physiological significance is not fully understood, but it is thought to represent repolarization of the Purkinje fibers or delayed repolarization of the ventricles. The presence of U waves can be normal, but it can also indicate electrolyte imbalances or other cardiac abnormalities. Dive deeper into the topic and uncover extra information within this expertly chosen external source. https://nurseonline.co.il/ekg-practice-test/, explore new details and perspectives about the subject covered in the article.


Understanding EKG intervals and segments is essential for accurate interpretation of EKG results. Each interval and segment provides important information about the electrical activity of the heart and potential abnormalities. By analyzing these components, healthcare professionals can diagnose and monitor various heart conditions, ensuring appropriate and timely treatment.

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