Chapter 37

1. Chapter 37 Electrocardiography

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

3. Anatomy of the Heart • Coronary arteries • Click here to see an animation

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

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

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

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

8. 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

9. Types of Electrocardiographs • Single-channel ECG >> • Multichannel ECG • Automatic ECG machines

10. Types of Electrocardiographs • ECG telephone transmissions • Facsimile electrocardiograph • Interpretive electrocardiograph

11. 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

12. 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

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

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

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

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

17. The Electrocardiographand Lead Placement • Galvanometer changes voltage into mechanical motion • Stylus records motion

18. The Electrocardiographand Lead Placement • Types of leads • Standard limb or bipolar leads • Augmented leads • Chest leads, precordial leads, or V leads • Placement of electrodes

19. 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

20. Standard Resting Electrocardiography • Performing 12-lead electrocardiogram

21. Standard Resting Electrocardiography Click Here to play the video

22. 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

23. Interference or Artifacts • Somatic tremor artifacts • Alternating current (AC) interference • Wandering baseline artifacts • Interrupted baseline artifacts

24. 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

25. Cardiac Arrhythmias Click Here to play the video

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

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

28. 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

29. 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

30. Holter Monitor • Medical assistant’s role • Preparing patient • Instructing patient • Applying and removing monitor

31. 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

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

33. 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

34. Other Diagnostic Tests • Loop ECG • Thallium stress test • Echocardiography/ultrasonography

35. 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

36. 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