Cardiac tetralogy includes ventricular premature tetralogy and supraventricular pre-systolic tetralogy. 1. Premature ventricular tetralogy is characterized by three sinus beats followed by a ventricular pre-systole. The ECG of ventricular tetralogy of fallot is typically characterized by the early appearance of QRS wave clusters with a wide aberration, a time limit of >0.12 seconds, and the absence of associated P-waves prior to the clusters, which are compensated for by a complete intermittent interval. 2. Supraventricular pre-systolic tetrad refers to the appearance of a supraventricular pre-systole after three sinus beats. The electrocardiogram of supraventricular pre-systole is characterized by early retrograde P waves and triggered QRS wave clusters with normal morphology. If you have frequent tetralogy of Fallot and have obvious symptoms, you should go to the hospital and follow the doctor’s instructions for prompt treatment.