In inferior leads suggest an inferior myocardial infarction and Q waves in precordial and lateral leads are due to myocardial infarctions in those areas.
Q waves on the EKG are highly suggestive of prior or silent and potentially unrecognized myocardial infarctions and associated with larger infarct size is assessed on cardiac magnetic resonance imaging.
Detection of Q waves is clinically important because their emergence carries prognostic value of future cardiovascular disease burden.
Q waves have a duration of 30 ms or greater and an amplitude of 1 mm or greater or QS complex in 2 contiguous leads.
Isolated Q waves, where Q waves in a contiguous lead are absent, may represent an incidental finding of limited prognostic value.
However, the study of primary care patients with any Q wave with isolated, lenient or strict definition was associated with increased long-term mortality risk compared with no Q waves (Polcwiartek C).