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Ep Defined | Getting Started | Working in the EP Lab
Right Atrium | Right Ventricle | Left Atrium | Left Ventricule | Cardiac Conduction | Cardiac Cell Properties | Action Potential | Sympathetic or Not | Med Page
Electrograms Defined | Recording Modes | Electrode Spacing | Filters | EGM Interpretation | Arrhythmia Analysis
The Physical Lab | Tools of the Trade
Setting Up | Catheter Placement | Baseline Measurement | SNRT | Conduction Study | Arrhythmia Induction | Pacing Protocols | Ablation | Tilt Table | Secrets to Success
Bradycardia | Atrial Tach | Atrial Flutter | Atrial Fibrillation | AVNRT | AVRT | Ventricular Tachycardia
Surface ECG's | Intracardiac Questions | Med Challenge | Advanced

Cardiac Disrhythmias - Bradycardias

Bradycardia - any rhythm that occurs at a rate slower than the normal range for the cardiac tissue involved.

Sinus Rhythm occurs in most people at rates of 60-100 beats per minute. Rates that originate from the sinus node slower than 60bpm are considered bradycardia. A slower rate may not be physiologically abnormal. An example of a bradycardia that is considered normal is the resting heart rate of a well conditioned athelete. Exercise and training have increased the strength of the heart muscle so that each time it contracts, it pumps out a volume of blood that exceeds the pumping capacity of an average person's heart. This volume, referred to as cardiac output, is one of the factors that determine how fast a persons heart rate will go. If the amount of blood that is pumped with each contraction of the heart is higher than normal, then the heart can beat at a slower rate and still provide sufficient oxygin supply to the body.

          Other slow rhythms, like the one displayed above, are due to defects in the cardiac concution system. The rhythm shown is an example of complete, or 3rd degree heart block. There is no association between the smaller P waves that represent contraction of the upper chambers of the heart and the larger QRS complexes that indicate contraction of the larger ventricles that comprise the two lower chambers of the heart. This rhythm is due to a block in the AV node that is the primary conduit of electrical activity between the atria and the ventricles.

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