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Atrial Arrhythmias ECG 31
1. Normal sinus rhythm
2. Premature ventricular contraction
3. Atrioventricular nodal reentry tachycardia (AVNRT)
Note the premature ventricular contraction (PVC) that triggers the AVNRT in this ECG. If a premature atrial contraction (PAC) or premature ventricular contraction (PVC) occurs at the right time, the normal conduction pathway will still be refractory, so the action potential will conduct through the slower AV nodal pathway with the shorter refractory period instead. After this action potential reaches the ventricles or atrium, it will conduct back through the normal AV nodal conduction pathway since it will no longer be refractory and a reentrant circuit will be created. See the ECG strip below which shows a PVC initiating AVNRT:
