ECG Indications and Monitoring PDF

INDICATIONS of ECG: Detect arrhythmias, as evidenced by abnormal wave deflections Monitor ECG changes during an exercise test Monitor rhythm changes during the recovery phase after a myocardial infarction (MI)...

INDICATIONS of ECG: Detect arrhythmias, as evidenced by abnormal wave deflections Monitor ECG changes during an exercise test Monitor rhythm changes during the recovery phase after a myocardial infarction (MI) Assess the extent of MI or ischemia, as indicated by abnormal S-T wave, interval times, and amplitudes Detect pericarditis, shown by S-T segment changes or shortened P-R interval Assess the function of heart valves Assess the extent of congenital heart disease Determine electrolyte imbalances, as evidenced by short or prolonged Q-T interval Evaluate and monitor the effect of drugs, such as digitalis antiarrhythmic, or vasodilating agents Evaluate and monitor cardiac pacemaker function Determine hypertrophy of the chamber of the heart or heart hypertrophy, as evidenced by P or R wave deflections ECG monitoring system Hardwire – permits continuous observation of one or more patients from more than one area of the unit; Connects electrodes directly to cardiac monitor; Limits mobility (patient is tethered to a monitor); Provides a continuous cardiac rate and rhythm display; Transmit the ECG tracing to a console at the nurses’ station; Has alarms; has attachments that can track pulse oximetry, BP, hemodynamic status and other values Telemetry monitoring – Allows mobility (patient carries a small, battery-powered transmitter that send electrical signal to another location for display on a monitor); useful for detecting arrhythmias during rest, sleep, exercise, and stressful situations; Monitors only heart rate and rhythm Other variations of taking ECG (This module focuses on taking the 12-lead ECG, which is most commonly used in the clinical area) Exercise ECG or Stress Test: evaluates heart action during physical stress - when oxygen demand increases- and thus provides important diagnostic information that can’t be obtained from a resting ECG alone. In this test, the ECG and BP readings are taken while the patient walks on a treadmill or pedals a stationary bike and his response to a constant or an increasing workload is observed. Holter monitor or ambulatory ECG is the continuous recording of heart activity as the patient follows his normal routine, usually for 24hrs or about 100,000 cardiac cycles. The patient wears a small cassette tape recorder connected to chest electrodes and keeps a diary of activities and associated symptoms. At the end of the recording period, the tape is analyzed, and a report is printed, permitting correlation of cardiac irregularities with the patient’s activities. Integrating systems of informatics: ECG Smart Phone Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 1  The 12-lead ECG is a diagnostic test that helps identify pathologic conditions, especially angina and acute myocardial infarction (MI). It gives a more complete view of the heart’s electrical activity than a rhythm strip and can be used to assess left ventricular function. Patients with other conditions that affect the heart’s electrical system may also benefit from a 12-lead ECG 12-lead ECG – records information on 12 different views of the heart using a series of electrodes placed on the patient’s limbs and chest. Six limb leads (I, II, III, AVR, AVL, AVF) provide information about the frontal plane of the heart Six precordial leads (V1, V2, V3, V4, V5, V6) provide information about the horizontal plane of the heart Standard limb leads Lead I: positive electrode on the left arm; Negative electrode on the right arm; Positive deflection; Helpful in monitoring atrial rhythms Lead II: positive electrode on the left leg; Negative electrode on the right arm; Positive, high-voltage deflection resulting in tall P, R, and T waves; Useful for identifying P waves, detecting sinus node and atrial arrythmias and monitoring the inferior wall of the left ventricle Lead III: positive electrode on the left leg; Negative electrode on the left arm; Positive deflection; useful for monitoring atrial rhythms and the inferior wall of the left ventricle th Image source: ECG Interpretation made incredibly easy (5 ed.). (2011). Wolters Kluwer, Lippincott Williams and Wilkins, USA. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 2  Augmented unipolar lead: Augmented vector – r (right); l (left); f (foot) Lead AVR – positive electrode on the right arm; Negative deflection Lead AVL – positive electrode on the left arm; usually a positive deflection Lead AVF – positive electrode on the left leg; Positive deflection; useful for monitoring the inferior wall of the left ventricles Precordial leads: 6 leads placed in sequence across the chest Lead V1 – Right side of the sternum at the fourth intercostal (ICS) space; Biphasic (positive and negative deflections) with QRS complex and T wave mostly negative; Useful for monitoring ventricular arrythmias, ST segment changes, and P-wave changes; useful for differentiating tachycardias (ventricular versus supraventricular) and bundle-branch blocks Lead V2 – Left of the sternum at the 4th IC; Negative deflection with a small amount of positive deflection; Useful for detecting ST-segment elevation Lead V3 – Between V2 and V4, at the 5th ICS; Biphasic (positive and negative deflections); Useful for detecting ST-segment elevation Lead V4 – 5th ICS at the midclavicular line; Positive deflection; Useful for detecting ST-segment and T-wave changes Lead V5 – 5th ICS at the anterior axillary line; Positive deflection; Useful for detecting ST-segment and T-wave changes Lead V6 (equivalent to MCL6) – 5th ICS at the midaxillary line; Positive deflection Sample 12-lead ECG Sample ECG Rhythm strip or Lead II waveform Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 3  The Lead II waveform, known as the rhythm strip, depicts the heart’s rhythm more clearly than any other waveform. In lead II, the normal P wave doesn’t exceed 2.5mm (0.25 mV) in height or last longer than 0.11 second. The PR interval, which includes the P wave and PR segment, persists for 0.12 to 0.2 second for cardiac rates over 60 beats/minute. The QT interval varies with the cardiac rate and lasts 0.4 o 0.52 second for rates above 60; R wave voltage in the V1 through V6 leads doesn’t exceed 27 mm. The total QRS interval lasts 0.06 to 0.1 second. The ECG Grid The horizontal axis of ECG strip represents time each small block equals 0.04 seconds 5 small blocks form a large block, which equals 0.2 seconds (0.4 sec X 5 = 0.2 sec) 5 large blocks equal 1 second (5 X 0.2) to measure or calculate heart rate (in beats per minute), use a 6 seconds strip, which consists of 30 large blocks The vertical axis measures amplitude in millimeters (mm) or electrical voltage in millivolts (mV) each small box represents 1mm or 0.1mV; each large block represents 5mm or 0.5mV Paper speed - 25mm/sec standard To determine the amplitude of ECG component (wave, segment or interval), count the number of small boxes from the baseline to the highest (in a positive wave) or lowest (in a negative wave) point of the wave, segment, or interval on a standard 12-lead ECG 6 seconds strip = 30 large boxes Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 4  Each PQRST is one heartbeat The cardiac cycle is depicted as series of waveforms, PQRST waves. U wave is late repolarization and NOT usually seen ECG waveforms reflect the direction of electrical flow in relation to positive (+) electrode -current flowing toward + electrode produces an upward (positive) waveform -current flowing away from the + electrode produces a downward (negative) waveform -current flowing perpendicular to a + pole produces a biphasic (both + & -) waveform -absence of electrical activity is represented by a straight line called the isoelectric line or baseline – a line from which waves and complexes takes off ECG Complex P wave Atrial depolarization PR segment Conduction delay through AV nodes; used as baseline to evaluate ST segment elevation or depression PR interval Atrial depolarization + conduction delay through AV node QRS Ventricular depolarization ST segment Isoelectric; ventricles still depolarized QT interval Ventricular depolarization + ventricular repolarization; mechanical contraction of ventricles T wave Ventricular repolarization nd Image source: G&A Clinical pocket guide for medical and allied health professionals (2 ed). (2009). G7A Notes Publishing Company, Philippines. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 5  Normal cardiac parameters: Normal sinus rhythm Between 60-100 bpm Sinus bradycardia Less than 60 bpm Sinus tachycardia Over 100 bpm QRS width Between 0.8 and 0.12 sec P-R interval Between 0.12 and 0.20 sec Q-T junction 0.30 - 0.40 sec Atrial rate, inherent 60-100 bpm Junction rate, inherent 40-60 bpm Ventricular rate, inherent 20-40 bpm The illustration shows the sequence of depolarization and repolarization of the heart related to the deflection waves on an ECG tracing Image source: https://slideplayer.com/slide/7857444/ Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 6  P wave – represents atrial depolarization or conduction of an electrical impulse through the atria. Location: precedes the QRS complex; With normal deflection and configuration, electrical impulses most likely originate in the SA node PR interval – represents the time required for the sinus impulse to travel to the AV node & into the purkinje fibers. This interval is measured from beginning of P wave to beginning of QRS complex. If no Q-wave is seen, the beginning of R wave is used. PR interval is normally 0.12 – 0.20 seconds. Greater than 20 indicate a delay in the conduction from the SA node to the ventricles QRS complex represents ventricular depolarization and contraction. QRS includes 3 separate waves, Q-the 1st negative deflection, R-positive or upright deflection: S-1st negative deflection after R wave -not all QRS have 3 waves, nonetheless it’s called QRS complex -normal duration is 0.08 -0.10 seconds ->0.10 indicates delay in transmitting the impulse through the ventricular conduction system ST segment – signifies the beginning of ventricular repolarization. ST segment, the period from the end of the QRS complex to the beginning of the T wave, should be isoelectric. An abnormal ST segment is displaced (elevated or depressed), from the isoelectric line T wave – represents ventricular repolarization. Normally has smooth, rounded shape that is usually less than 10mm tall. It usually points in the same direction as QRS complex. Abnormalities may indicate myocardial ischemia or injury, or electrolyte imbalances QT interval – measured from beginning of QRS complex to end of T wave -represents total time of ventricular depolarization and repolarization. Duration varies with gender, age, HR, usually 0.30-0.40 seconds long. -prolonged QT indicates a prolonged relative refractory period and a greater risk of dysrhythmias. Shortened may results from medications or electrolyte imbalance -U wave is not normally seen. It is thought to signify repolarization of the terminal purkinje fibers. If present, U wave follows the same direction as the T wave. Most commonly seen in hypokalemia Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 7  Older adult ECGs: Always keep the patient’s age in mind when interpreting an ECG. An older adult’s ECG may include increased PR, QRS, and QT intervals; decreased amplitude of the QRS complex; and a shift of the QRS axis to the left. Watch the video presentation with file name: Module 5 ECG Introduction th Image source: ECG Interpretation made incredibly easy (5 ed.). (2011). Wolters Kluwer, Lippincott Williams and Wilkins, USA. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. 8