Here is a Pacemaker ECG with no signs of PM malfunction: Beat A is an intrinsic beat (atrial fibrillation). Beat B is a pseudofusion beat. Beat C is a fully paced beat. Beat D is a fusion beat. Ventricular fusion is the electrical summation of an intrinsic beat of the heart and depolarization from a pacing stimulus. The morphology lies between a fully paced beat and a complete intrinsic beat.

This patient is a 50-year-old man. His brother was diagnosed with epilepsy and died during a seizure at the age of 21.

Parts of the following text I have taken over from Dawn`s explanation on Brugada pattern/Brugada syndrome:

Here is the ECG of a 3-year-old boy. Is there cause for concern? The ECG shows a sinus rhythm with significant sinus arrhythmia. The heart rate increases with inspiration and decreases with expiration, which is called respiratory sinus arrhythmia. The QRS-axis is between 60 and 90 degrees, which is physiological at this age. The negative T-waves in V1-V3 (V4) are also age-appropriately normal. Therefore, there is no reason for concern; the ECG is considered normal for the child's age.

Complex ECGs like this one have to be approached systematically. Firstly, we can see a normal sinus rhythm. A is the first beat of a wide complex tachycardia. This must be a ventricular tachycardia. Although there is a P-wave before the first beat of the tachycardia, it is not premature. Therefore, there is no SVT with aberrant conduction. The first beat of the tachycardia looks different from the subsequent beats because there is a fusion beat present. The VT conducts 1:1 back to the atria (a small negative P-wave can be seen at the end of the QRS complex in V1).