Overview
This lecture covers normal and abnormal heart rhythms, focusing on cardiac arrhythmias, their causes, and how they affect heart function.
Normal Heart Rhythm and EKG Waves
- Normal heart rhythm means the heart's electrical impulses follow the expected pattern.
- The P-wave on an EKG shows atrial depolarization (sodium ions rushing in).
- The QRS complex shows ventricular depolarization.
- The T-wave shows ventricular repolarization (potassium ions rushing in).
- Depolarization is when the heart muscle becomes more positive; repolarization brings it back to negative.
Types of Cardiac Arrhythmias
- Arrhythmia is when the heart's normal rhythm is disrupted, affecting the efficiency of heartbeats.
- Common arrhythmias include ectopic focus, extrasystole, bradycardia, tachycardia, fibrillation, and heart block.
Arrhythmia Types and Characteristics
- Ectopic Focus: An area outside the SA node takes over pacing, often because it's depolarizing faster.
- Extrasystole: An extra heartbeat occurs when another site fires after the SA node; usually harmless.
- Bradycardia: Heart rate less than 60 bpm; normal in athletes but may indicate disease or hypothyroidism.
- Tachycardia: Heart rate over 100 bpm; can be caused by stress, caffeine, nicotine, drugs, potassium deficiency, anemia, or hyperthyroidism; dangerous if persistent.
- Fibrillation: Uncoordinated, rapid twitching of heart muscle, usually the ventricles; life-threatening if not corrected.
- Heart Block (AV block): Damage to the AV node prevents signals from reaching the ventricles, causing life-threatening loss of coordinated pumping.
Key Terms & Definitions
- Arrhythmia — Abnormal heart rhythm.
- Depolarization — Process where sodium ions enter heart cells, making them more positive.
- Repolarization — Process where potassium ions re-enter, restoring cells to a negative state.
- Ectopic Focus — Non-SA node area that sets the heart's pace.
- Extrasystole — Premature or extra heartbeat.
- Bradycardia — Abnormally slow heart rate (<60 bpm).
- Tachycardia — Abnormally fast heart rate (>100 bpm).
- Fibrillation — Disorganized electrical activity causing ineffective heart contractions.
- Heart Block — Failure in conduction between atria and ventricles, often at the AV node.
Action Items / Next Steps
- Review EKG waveforms and correlate with electrical events in the heart.
- Study causes and effects of different arrhythmias.