Category	ECG findings		Comment
A (normal or normal variant ECG reading)	Sinus bradycardia, arrhythmia, or tachycardia		These ECGs do not require further workup unless clinical symptoms, physical examination, or history suggests cardiac involvement.
	Right ventricular conduction delay or incomplete right bundle branch block without right ventricular hypertrophy or right axis deviation
	Isolated intraventricular conduction delay
	Right axis deviation in patients 8 years or younger
	Early repolarization
	Nonspecific ST-T wave changes
	Juvenile T-wave pattern
	QTc ≥ 0.45 seconds by computer, but normal by hand calculation
	Borderline QTc of 0.44 to 0.45 seconds

B (abnormal readings that have a low likelihood of correlating with cardiac disease)	Isolated atrial enlargement, especially right atrial enlargement; this usually will not need further evaluation		Patients with these findings may need to be seen by a cardiologist. The prescribing physician should correlate the ECG reading with the history, physical examination, and symptoms, and discuss the reading with a cardiologist to assess the need for a referral. ADHD medication usually does not need to be stopped with these findings; if there is a question about stopping medication, discussion with a cardiologist is recommended.
	Biventricular hypertrophy with only mild midprecordial voltages of 45 or 50 mm; this may need further evaluation
	Ectopic atrial rhythms; right atrial, left atrial, wandering atrial pacemaker at normal rates
		Low right atrial rhythms are common, usually are normal variants, and will rarely need further evaluation; other ectopic atrial rhythms are less common and may need further evaluation

	First-degree atrioventricular block


C (abnormal readings that may correlate with the presence of cardiac disease)	Left or right ventricular hypertrophy		As with category B readings, the prescribing physician should correlate the ECG reading with the history, physical examination, and any symptoms the patient might have, and discuss the findings with a cardiologist to assess the need for a cardiology office visit. It is likely that a patient with this reading will need to be seen by a cardiologist; however, a cardiology office visit with examination and further testing or evaluation may not result in a diagnosis of cardiac disease. In fact, many of these patients have a small likelihood of having significant cardiac pathology that would result in a change in the plan of treatment of their ADHD. Therefore, it is not necessary in most cases to immediately stop the medication, but discussion with a cardiologist is recommended.
	Wolff-Parkinson-White syndrome
	Left axis deviation
	Right axis deviation, especially in patients older than 8 years
	Right atrial enlargement and right axis deviation
	Right ventricular conduction delay and right axis deviation
	Second- and third-degree atrioventricular block
	Right bundle branch block, left bundle branch block, intra-ventricular conduction delay > 0.12 seconds in patients olderthan 12 years (> 1.10 seconds in patients younger than 8 years)
	Prolonged QTc > 0.46 seconds
		The prescribing physician should ask about medication that might prolong QTc, which could cause mild QTc prolongation
	Abnormal T waves with inversion V₅, V₆; bizarre T-wave morphology, especially notched or biphasic, or flat and/or ST-segment depression suggesting ischemia or inflammation
	Atrial, junctional, or ventricular tachyarrhythmias, including frequent premature atrial contractions or premature ventricular contractions