Congenital complete heart block with RR interval of 1280 msec (ventricular rate: 47/min) and PP interval of 960 msec (atrial rate of 62.5/min). The four criteria four diagnosis of complete heart block are satisfied: regular PP interval, regular RR interval, PP interval less than RR interval and varying PR interval. QRS is narrow, indicating supra Hisian location of the complete heart block, with a junctional focus capturing the ventricle. Such a situation in a young boy indicates congenital complete heart block. An exercise test is useful in assessing the response of the heart rate to exercise (below).
In stage 1 of exercise, the PP interval has shortened to 600 msec (atrial rate: 100/min) and RR interval is 1000 msec (ventricular rate: 60/min). There is progressive change in atrial and ventricular rates with exercise, though the response is blunted compared to sinus rhythm with regular conduction. (Please observe the raw rhythm strip at the bottom of the tracing). The peak exercise recording is given below.
Peak exercise tracing in congenital complete heart block with PP interval 400 msec (atrial rate: 150/min) and RR interval of 720 msec (ventricular rate: 83/min). (Please observe the raw rhythm strip at the bottom of the tracing).