Can someone explain to me narrow and wide complex tacycardia? How are they identified on the ECG, the causes of either?
Less than 3 small boxes in an ecg paper is suggestive of narrow complex tachycardias which occur definitely because of supraventricular causes, can be AVNRT, AVRT , atrial tachycardias. Narrow complex means there’s no conduction anomaly in the ventricles indirectly implying the cause is either in the nodes or the bundle branches or atria.
Greater than 3 small boxes in the ecg is wide complex tachycardias implying conduction anomalies in the ventricles as such, can be VTs or VF even WPW also can be wide if there’s the delta wave in qrs.