From the Guidelines
Pathologic Q waves on an ECG are defined as exaggerated or unexpected Q waves in atypical leads, which can be a result of various pathological disorders, including HCM, ARVC, infiltrative myocardial diseases, accessory pathways, and transmural myocardial infarction, as reported in the 2017 study by the Journal of the American College of Cardiology 1. To be considered pathological, Q waves should be evaluated using a Q/R ratio, which normalizes Q wave depth to the degree of proceeding R-wave voltage, as this approach decreases the false positive rate without compromising sensitivity for the detection of cardiomyopathy 1. Some key points to consider when evaluating pathologic Q waves include:
- They can be a result of lead misplacement, particularly a pseudo-septal infarct pattern with pathological Q waves in leads V1 to V2 due to high-lead placement relative to cardiac position 1
- Pathological Q waves have been reported in approximately 1% to 2% of all athletes, with higher rates in males and black athletes 1
- The previous definition of pathological Q waves as >3 mm in depth or >40 ms in duration in two or more leads (except III and aVR) is no longer recommended due to its high false positive rate 1
- A Q/R ratio is a more accurate and reliable method for detecting pathological Q waves, especially in asymptomatic athletes with physiological LVH or thin adolescent athletes who may have increased precordial voltages and deep lateral or inferior Q waves 1
From the Research
Definition of Pathologic Q Waves
- Pathologic Q waves are a type of abnormality seen on an electrocardiogram (ECG) that can indicate myocardial infarction (MI) or other heart conditions 2.
- The criteria for pathological Q waves after acute myocardial infarction (MI) have changed over the years, with different definitions used to diagnose Q-wave MI, including "classic" criteria, Thrombolysis In Myocardial Infarction criteria, and 2000 and 2007 consensus criteria 2.
Association with Infarct Size
- The association of Q waves with infarct size is strongest when using the classic Q-wave criteria 2.
- Patients with Q-wave MI had larger infarct size and lower left ventricular ejection fraction (LVEF) on baseline cardiac magnetic resonance (CMR) compared with patients with non-Q-wave MI 2.
Q-Wave Regression
- Q-wave regression is associated with the largest improvement of LVEF as assessed with CMR 2.
- Patients with Q-wave regression displayed significantly larger LVEF improvement in 24 months compared with both persistent Q-wave MI and non-Q-wave MI 2.