Making sense of the paediatric ECG: rate and rhythm

A fit, well, asymptomatic 6-year-old girl was referred to clinic for a murmur. Her ECG is shown in figure 1. Figure 1 Patient’s ECG. ### Rate, rhythm and PR interval The median heart rate for a 6-year-old girl is 89 bpm (range 68–115 bpm (2nd–98th centile)).1 Here, the ventricular rate is 5–6 large squares (50-60 bpm), signifying bradycardia. The atrial rate is faster (three large squares, 100 bpm). Some P waves are obscured within T waves or QRS complexes. The P waves are not related in the normal way to the QRS complexes. Therefore, the PR interval cannot be calculated. ### Complete heart block (CHB) The atrial and ventricular rates are different, with a complete lack of relationship (dissociation) between atrial and ventricular depolarisation. In this case, the escape rhythm originates from the His Bundle resulting in …