Electrocardiography, Dr. D. Penney

Figure 22. Third-degree (complete) heart (AV) block. There is no relationship between P waves and QRS complexes: QRS rate is slower than P wave rate. Impulses originate at SA node (P waves) and also below the site of block in ventricles (idioventricular rhythm). Atria and ventricles depolarize independently, QRS complexes are less frequent; regular at 20 to 40/min but wide and abnormal in shape.


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