Electrocardiograph ECG – waves and segments P- wave QRS – wave T- wave PR - interval QRS - interval QT- interval PQ – segment ST – segment SA node must depolarize Ventricular Depolarization QT intervial tells us about the action potential of the myocyte
Disorders Most problems caused by disjunction of electrical system Arrhythmia – abnormal cardiac rhythm 1. Heart Block (varies in degrees) – failure in conduction system 2. Atrial flutter – extra beats of the atrial muscle 3. Premature ventricular contractions (PVC’s) – extra beat 4. Ventricular fibrillation – electrical signals arrive at ventricular myocytes at different times 5. Myocardial infarction 6. Long QT 7. Electrolyte disturbances
• Heart Block – electrical signal disrupted between atria and ventricles i. First degree ii. Second degree iii. Third degree (complete) Disorders
Electrocardiograph • Nodal Rhythm – no SA node input , AV node pacemaker – 50 bpm Which wave is missing?
• Atrial Flutter: rapid heart beat (tachycardia) 250-300 bpm 2:1 QRS usually present (QRS max out at 250 bpm) • Atrial Fibrillation: rapid heart beat (tachycardia) 300-500 bpm Disorders
• PVC’s (extrasystole) – usually originate in left ventricle i. Inverted, misshapen QRS wave Disorders
• Ventricular fibrillation– erratic firing of ventricular myocytes, unsynchronized contraction Disorders
• Myocardial Infarction (MI) i. ST elevation ii. T- wave inversion Disorders
• Long QT syndrome i. Ion channel mutations (K + , Ca 2+ , Na + ) ii. Leads to ventricular tachycardia, and death Disorders Longer to repolarize Na or Ca stays on K doesn’t turn on
• Changes in Plasma K + : most relevant electrolyte disturbance Disorders Hyperkalemia leads to death
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- Spring '17
- Cardiac electrophysiology, Sinoatrial node, ventricular tachycardia, Ventricular fibrillation, Cardiac Myocyte