Complete heart block – narrow QRS

Complete heart block – narrow QRS

Complete heart block - narrow QRS
Complete heart block – narrow QRS

The tracing shows regular QRS complexes with a ventricular rate 42/min, regular P waves with an atrial rate 115/min, QRS width of 80 msec and varying PR interval, indicating complete heart block with narrow QRS. Complete heart block with narrow QRS occurs in congenital complete heart block and complete heart block associated with inferior wall myocardial infarction. The narrow QRS indicates that the block is above the His bundle or supra Hisian. In congenital complete heart block, the ventricular rate is about 60/min and it can be missed in a routine clinical examination as the rate is near normal. A phenomenon which can sometimes be seen in complete heart block is ventriculophasic sinus arrhythmia. In ventriculophasic sinus arrhythmia, a PP interval enclosing a QRS is shorter than one which does not enclose a QRS. This is supposed to be due to the shortening of the sinus cycle length by the mechanical effect of the ventricular contraction.

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