EKG/ECG Interpretation Basics Nursing NCLEX | QRS Complex, P Wave, T Wave, PR Interval

Summary

In this video, Sarah from RegisterNurseRN.com explains the basics of EKG interpretation. She walks through the electrical conduction system of the heart, including how blood flows through the heart and how electrical signals control heartbeats. The video covers key concepts like depolarization, repolarization, and the PQRST complex. Sarah demonstrates how to analyze an EKG strip, including measurements, intervals, and identifying normal sinus rhythm. The tutorial also provides practical steps to assess rhythm and detect abnormalities such as heart blocks or arrhythmias, ensuring a comprehensive understanding of EKG basics.

Takeaways

• 😀 An EKG (electrocardiogram) assesses the electrical conduction system of the heart, which is responsible for controlling the heart's contractions and blood flow.
• 😀 Depolarization leads to contraction, and repolarization refers to the relaxation of heart cells. Understanding these processes is key to interpreting EKGs.
• 😀 The electrical conduction system starts in the SA node, which triggers atrial depolarization, and then the signal moves to the AV node, bundle of His, bundle branches, and Purkinje fibers to trigger ventricular depolarization.
• 😀 The PQRST complex represents the stages of electrical activity in the heart: P wave for atrial depolarization, QRS for ventricular depolarization, and T wave for ventricular repolarization.
• 😀 The EKG strip is made up of small boxes (0.04 seconds) and large boxes (0.20 seconds), which are used to measure the duration of parts of the PQRST complex.
• 😀 The P wave represents atrial depolarization (contraction). It should be round and less than 0.12 seconds in duration.
• 😀 The PR interval measures the time it takes for the electrical signal to travel from the atria to the AV node. A normal PR interval ranges from 0.12 to 0.20 seconds.
• 😀 The QRS complex represents ventricular depolarization (contraction). It should be less than 0.12 seconds in duration. If it's wider, it could indicate an abnormal rhythm.
• 😀 The ST segment follows the QRS complex and marks the completion of ventricular depolarization. It should be flat (isoelectric), without elevation or depression greater than 1 millimeter.
• 😀 The QT interval measures the time it takes for the ventricles to contract and then rest. It typically ranges from 0.35 to 0.44 seconds and can be affected by heart rate.

Q & A

What does EKG or ECG stand for, and what is its primary purpose?

EKG (or ECG) stands for electrocardiogram. Its primary purpose is to assess the electrical conduction system of the heart, which controls the contraction and relaxation of the heart muscles to pump blood throughout the body.

How does blood flow through the heart, and how is this related to the electrical conduction system?

Blood flows from the right atrium → tricuspid valve → right ventricle → pulmonic valve → pulmonary artery → lungs for oxygenation → pulmonary vein → left atrium → mitral valve → left ventricle → aortic valve → body. The electrical conduction system triggers the atria and ventricles to contract at the right times, ensuring smooth blood flow.

What is the difference between depolarization and repolarization in heart cells?

Depolarization is when a heart cell becomes more positive and contracts. Repolarization is when the cell returns to a negative state and relaxes. Depolarization corresponds to contraction, and repolarization corresponds to relaxation.

Which part of the heart is known as the pacemaker, and what is its normal firing rate?

The SA node (sinoatrial node) is known as the pacemaker of the heart. It normally fires at a rate of 60–100 beats per minute.

What role does the AV node play in the electrical conduction system?

The AV node acts as a gatekeeper, delaying the electrical signal slightly to allow the atria to fully empty their blood into the ventricles before ventricular contraction occurs.

What does the P wave represent on an EKG strip, and what are its normal characteristics?

The P wave represents atrial depolarization, which causes atrial contraction. It should be upright, round, and less than 0.12 seconds in duration (less than three small boxes).

How is the PR interval different from the PR segment, and what is its clinical significance?

The PR interval starts at the beginning of the P wave and ends at the beginning of the QRS complex. It represents the time for the electrical signal to travel from the atria to the AV node. A prolonged PR interval may indicate a heart block. The PR segment is the flat line after the P wave and before the QRS complex, showing AV node delay.

What does the QRS complex represent, and what is its normal duration?

The QRS complex represents ventricular depolarization, which leads to ventricular contraction. Its normal duration is ≤ 0.12 seconds (up to three small boxes).

How should the ST segment and T wave appear on a normal EKG, and what do they indicate?

The ST segment should be flat (isoelectric) and represents the completion of ventricular depolarization and the beginning of repolarization. The T wave follows the QRS complex, is upright and round, and represents ventricular repolarization (ventricular relaxation).

What is the QT interval, and why is it important?

The QT interval starts at the beginning of the QRS complex and ends at the end of the T wave. It represents the total time for ventricular depolarization and repolarization. Abnormal QT intervals can indicate an increased risk of ventricular dysrhythmias.

How do you calculate heart rate using a 6-second EKG strip?

Count the number of P waves or QRS complexes within 6 seconds (30 large squares) and multiply by 10. This gives the atrial or ventricular rate in beats per minute.

What criteria define a normal sinus rhythm?

A normal sinus rhythm has P waves present before each QRS, PR interval 0.12–0.20 seconds, QRS ≤ 0.12 seconds, ST segment flat, T wave upright, QT interval 0.35–0.44 seconds, and a regular atrial and ventricular rate of 60–100 bpm.