Pathological Q Waves on EKG

Definition and Characteristics

Pathological Q waves are defined as a Q/R ratio ≥ 0.25 or Q waves ≥ 40 ms in duration in two or more contiguous leads (except III and aVR), according to the American College of Cardiology 3, 4
The American College of Cardiology states that pathological Q waves appear as any Q wave ≥ 0.02 sec or QS complex in leads V2–V3 1
The American College of Cardiology and Circulation define pathological Q waves as Q wave ≥ 0.03 sec and ≥ 0.1 mV deep or QS complex in leads I, II, aVL, aVF or V1–V6 in any two leads of a contiguous lead grouping 1, 2

The American College of Cardiology notes that pathological Q waves can also be seen in hypertrophic cardiomyopathy (HCM) 3, 5
The American College of Cardiology states that pathological Q waves can also be seen in arrhythmogenic right ventricular cardiomyopathy (ARVC) 3, 5
The American College of Cardiology notes that pathological Q waves can also be seen in infiltrative myocardial diseases 3
The American College of Cardiology states that pathological Q waves can also be seen in accessory pathways 3
The American College of Cardiology notes that myocardial fibrosis in the absence of coronary artery disease can also cause pathological Q waves 1

The American College of Cardiology recommends that an ECG with abnormal Q waves should be carefully examined for the possibility of an accessory pathway 4
The American College of Cardiology states that if pathological Q waves are isolated to leads V1-V2, the ECG should be repeated with careful attention to lead placement, as high lead placement can cause a pseudo-septal infarct pattern 3, 4
The American College of Cardiology recommends that persistence of pathological Q waves in two or more contiguous leads warrants further investigation with echocardiography to exclude cardiomyopathy 4
The American College of Cardiology suggests that in patients ≥30 years with suspicion of prior myocardial infarction or risk factors for coronary artery disease, stress testing may be warranted 4

The American College of Cardiology notes that not all Q waves are pathological - normal septal Q waves are small (<0.03 sec and <25% of the R-wave amplitude) in leads I, aVL, aVF, and V4–V6 6
The American College of Cardiology states that a QS complex in lead V1 is normal 6
The American College of Cardiology notes that a Q wave <0.03 sec and <25% of the R wave amplitude in lead III is normal if the frontal QRS axis is between 30° and 0° 6
The American College of Cardiology states that a Q wave may also be normal in aVL if the frontal QRS axis is between 60° and 90° 6
The American College of Cardiology warns that lead misplacement can cause pseudo-infarct patterns, particularly high placement of precordial leads causing Q waves in V1-V2 3