Reprint requests to Cardiology Section, University of Illinois Hospital PO Box 6998, Chicago, IL 60680 (Dr. Rosen).
THE specialized cardiac conduction system consists of sinus node, atrioventricular node, His bundle, and the bundle-branch system. Impulse formation is normally initiated in the sinus node, while the other structures are necessary for conduction of the impulse from atrium to ventricles and for distribution of the impulse in an orderly fashion to the ventricles. Activation of the specialized conduction system is not seen directly on the surface electrocardiogram, which only shows activity of atrial muscle (P wave) and ventricular muscle (QRS complex). Abnormalities of the specialized conduction system are inferred from the surface cardiogram; eg, atrioventricular block, which produces abnormal conduction patterns between P waves and QRS complexes, and bundle-branch blocks, which produces a disordered QRS.
Techniques are now available that allow a more direct look at the function of the specialized conduction system.1-4 The most important of these is the catheter recording of His bundle electrograms. With catheterization of
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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