Osmosis from Elsevier - Electrocardiogram (ECG) - Normal sinus rhythm (NSR): Clinical Nursing Care
An electrocardiogram (ECG) is a routine diagnostic test that uses electrodes placed on the skin to capture the heart's electrical activity. It is commonly known as a 12-lead ECG, involving 10 electrodes that provide 12 different views of the heart's electrical impulses. The test is crucial for assessing the heart's conduction system, which includes the SA node, AV node, and the His-Purkinje system, ensuring coordinated heart contractions. The ECG waveform includes the P-wave, QRS complex, and T-wave, each representing different phases of the heart's electrical cycle. Proper electrode placement and artifact elimination are essential for accurate results. In nursing care, it's important to explain the procedure to the patient, ensure their comfort, and check for any interfering factors like pacemakers or medications. After the test, electrodes should be removed carefully to ensure patient safety.
Key Points:
- ECG uses 10 electrodes to provide 12 views of heart activity.
- The heart's conduction system includes SA node, AV node, and His-Purkinje fibers.
- ECG waveform consists of P-wave, QRS complex, and T-wave.
- Proper electrode placement and artifact elimination are crucial for accuracy.
- Nurses should ensure patient comfort and check for interfering factors.
Details:
1. 📖 Introduction to ECG: What and How
1.1. What is an ECG?
1.2. Understanding the 12-Lead ECG System
2. 💡 Heart's Electrical Journey: Electrophysiology Explained
- The cardiac conduction system consists of myocardia cells capable of generating and transmitting electrical impulses, known as action potentials.
- Key features of these cells include automaticity (ability to generate impulses autonomously), conductivity (ability to carry impulses to other cells), and contractility (ability to contract and shorten fiber length, causing contraction).
- The electrical impulses originate from the Sinoatrial (SA) node, located at the junction of the superior vena cava and right atrium, which acts as the heart's pacemaker with impulses generated at 60 to 100 beats per minute.
- The impulse travels through the atrial muscle, causing depolarization and subsequent contraction, pushing blood from atria to ventricles.
- The impulse reaches the Atrioventricular (AV) node, where conduction velocity slows, allowing atrial contraction and ventricular filling.
- The depolarization wave travels through the ventricular conduction system, including the bundle of His, left and right bundle branches, and Purkinje fibers, ensuring coordinated heart contraction.
- The system's rapid conduction supports synchronized contraction, crucial for blood ejection into pulmonary and systemic circulations.
- Ventricular repolarization prepares the heart for the next cycle, allowing relaxation and blood filling.
3. 🔍 ECG Tracings and Waveforms: Decoding the Heartbeat
- The ECG tracing assesses the heart's conduction system by showing the movement of the depolarization wave during each heartbeat.
- A typical ECG waveform includes a P-wave (atrial depolarization), a QRS complex (ventricular depolarization), and a T-wave (ventricular repolarization).
- The U-wave may appear after the T-wave, indicating late ventricular repolarization.
- The PR interval measures the time for an impulse to travel from the SA node to the Purkinje fiber network, representing atrial to ventricular depolarization.
- The PR segment represents the time required for the impulse to travel through the AV node to the Purkinje fibers.
- The QT interval spans from the QRS complex to the end of the T-wave, indicating the entire process from ventricular depolarization through repolarization.
- The ST segment, within the QT interval, represents the time between the end of the QRS complex (J point) and the end of the T-wave, indicating ventricular repolarization.
4. 📊 Interpreting ECG: Normal Results and Measurements
- The ECG paper is divided into large squares containing 25 smaller squares; each small square represents 0.04 seconds horizontally and 0.1 mV vertically.
- Heart rate is calculated by counting QRS complexes in six seconds and multiplying by 10.
- Heart rhythm regularity is assessed by checking the distance between peaks of consecutive P waves and R waves; a ratio of 1 indicates regular rhythm.
- A P wave should be present, regular in timing and shape, with one for each QRS complex.
- PR interval should consistently be between 0.12 to 0.20 seconds (3 to 5 small boxes).
- QRS duration should be less than 0.1 seconds (2.5 small boxes).
- ST segment should not be elevated or depressed more than one small box.
- T-wave should be asymmetric, with height less than 5 mm in precordial leads and less than 10 mm in limb leads.
- QT interval should be less than or equal to half of a cardiac cycle.
5. 🩺 Nursing Care: Preparing for an ECG Test
- An ECG test measures the heart's electrical activity to diagnose heart conditions. It is a routine, non-invasive, and painless procedure.
- Before the test, verify the patient's safety, ensure they can follow instructions, and check for any pacemaker devices or heart-affecting medications.
- Prepare the patient's skin by cleaning, drying, and shaving excess chest hair to ensure electrode adhesion and accurate readings.
- Accurate electrode placement is crucial: RA lead on right arm/shoulder, LA on left arm/shoulder, RL on right leg, LL on left leg, V1-V6 on specific chest points.
- Check all connections to prevent artifacts that could distort results.
- Position the patient semi-reclined, instruct them to stay still and breathe normally during the test.
- Post-test, remove electrodes carefully, check patient comfort, and provide necessary post-test care instructions.