Chapter 37 Electrocardiography

Anatomy of the Heart Four chambers Deoxygenated blood Oxygenated blood Two upper chambers known as atria Two lower chambers known as ventricles Deoxygenated blood Oxygenated blood

Anatomy of the Heart Coronary arteries Watch the animation

Electrical Conduction System of the Heart Sinoatrial (SA) node Atrioventricular (AV) node Bundle of His and Purkinje fibers

Electrical Conduction System of the Heart Systole and diastole Impulses can be recorded on ECG paper or displayed on oscilloscope

The Cardiac Cycle and the ECG Cycle Baseline or isoelectric line Positive deflection Negative deflection Each cardiac cycle takes about 0.8 second

The Cardiac Cycle and the ECG Cycle P, QRS, and T waves

Calculation of Heart Rate On ECG graph paper: Every fifth line is darker than other lines Time is measured on horizontal line Voltage is measured on the vertical line

Types of Electrocardiographs Single-channel ECG >> Multichannel ECG Automatic ECG machines (see Procedure 37-1 in the text)

Types of Electrocardiographs ECG telephone transmissions Facsimile electrocardiograph Interpretive electrocardiograph

ECG Equipment Electrocardiograph paper Black or dark blue Wax or plastic coated Heat and pressure sensitive Heat of stylus can be adjusted to obtain a sharp tracing

ECG Equipment Electrolyte Help pick up electrical current produced by contraction and relaxation of heart In form of gel, lotion, paste, or pre-saturated pads

ECG Equipment Sensors or electrodes Disposable sensors Detect electrical impulses on body surface from the myocardium and relay them through cables

ECG Equipment Lead wires Caring for equipment Once self-adhesive sensors are placed, lead wires from the ECG machine are attached Caring for equipment

Lead Coding 12 leads recorded using 10 lead wires Necessary for identification and mounting purposes Newer ECGs automatically mark (code) each lead

The Electrocardiograph and Lead Placement 12 leads record heart’s electrical activity Allows for 3D interpretation of activity Amplification of electrical activity

The Electrocardiograph and Lead Placement Galvanometer changes voltage into mechanical motion Stylus records motion

The Electrocardiograph and Lead Placement Types of leads Standard limb or bipolar leads Augmented leads Chest leads, precordial leads, or V leads Placement of electrodes

Standardization of the Electrocardiograph Value of recording depends on accuracy Universal measurements One millivolt of cardiac electrical activity will deflect stylus exactly 10 mm high (discuss the Critical Thinking Box)

Standard Resting Electrocardiography Performing 12-lead electrocardiogram (see Procedure 37-1 in the text)

Standard Resting Electrocardiography Watch the video (see Procedure 37-1 in the text)

Mounting the ECG Tracing Commercially prepared mounting forms Mount completed tracing after provider has reviewed entire recording Identify patient, date, age, blood pressure, height and weight, and cardiac medications (see Procedure 37-1 in the text)

Interference or Artifacts Somatic tremor artifacts Alternating current (AC) interference Wandering baseline artifacts Interrupted baseline artifacts (discuss the Critical Thinking Box)

Cardiac Conditions and Diseases Myocardial infarctions (heart attack) Primary cause of death in U.S. Offer patient health tips as part of patient education Behaviors to adopt for a healthy heart

Cardiac Arrhythmias Watch the video

Cardiac Arrhythmias Atrial arrhythmias Premature atrial contractions (PAC) Paroxysmal atrial tachycardia (PAT) Atrial fibrillation

Cardiac Arrhythmias Ventricular arrhythmias Premature ventricular contractions (PVCs) Ventricular tachycardia Ventricular fibrillation

Defibrillation Electrical device that applies countershocks to heart through electrodes or pads placed on chest wall (AED) Can convert cardiac arrhythmia into normal sinus rhythm

Holter Monitor Portable ambulatory electrocardiograph Portable continuous recording of cardiac activity for a 24-hour period Noninvasive test Helps diagnose cardiac arrhythmias by correlating them with patient’s symptoms (see Procedure 37-2 in the text)

Holter Monitor Medical assistant’s role Preparing patient Instructing patient Applying and removing monitor (discuss the Critical Thinking Box)

Holter Monitor Patient activity diary Record all activities, emotional states, and time of their occurrence Record chest pain and other symptoms and time of their occurrence

Holter Monitor Removing the Holter Monitor Patient returns to office Tape is analyzed by scanner or computer Written report sent to physician

Other Diagnostic Tests Treadmill stress test Diagnose heart disorders and probable cause of patient’s chest pain Assess patient’s cardiac ability following cardiac surgery Noninvasive test Patient exercises on treadmill at varying rates of speed

Other Diagnostic Tests Loop ECG Thallium stress test Echocardiography/ultrasonography

Cardiac Procedures Coronary angioplasty with and without stent Balloon inflated inside coronary artery with or without stent Keeps artery open Coronary artery atherectomy Cutting away of plaque in blocked coronary artery

Other Cardiac Diagnostic Tests Coronary artery bypass Vein transplanted into blocked coronary artery(ies) Blood supply reestablished to myocardium Cardiac computerized tomography and cardiac magnetic resonance