From the Research
Q wave abnormalities following a septal myocardial infarction typically persist indefinitely in most patients, but may partially regress or disappear over months to years in approximately 30% of patients, particularly with successful early reperfusion therapy. These pathological Q waves generally develop within hours to days after the infarction and become permanent markers of the myocardial damage. Unlike other ECG changes such as ST-segment elevation or T-wave inversions that may resolve over time, Q waves represent the electrical signature of scarred myocardial tissue that has lost its ability to conduct electrical impulses normally. The persistence of these Q waves occurs because the infarcted septal tissue undergoes necrosis and is eventually replaced by non-conductive scar tissue. This permanent structural change in the myocardium creates a fixed electrical pattern on the ECG.
Some key points to consider include:
- The development of Q waves is associated with the size of the infarct, with larger infarcts more likely to result in persistent Q waves 1.
- Early reperfusion therapy, such as primary percutaneous coronary intervention (PCI), can limit the extent of myocardial damage and increase the likelihood of Q wave regression 1.
- Q wave regression is associated with improved left ventricular ejection fraction (LVEF) and reduced infarct size, as measured by cardiac magnetic resonance (CMR) imaging 1.
- The classic ECG criteria for Q wave MI show the strongest correlation with infarct size, as measured by CMR 1.
In terms of prognosis, the presence of Q waves is associated with a higher risk of mortality and morbidity, particularly in patients with anterior MI 2. However, Q wave regression is associated with improved outcomes, including reduced mortality and improved LVEF 1.
Overall, while Q wave abnormalities typically persist indefinitely, there is evidence to suggest that early reperfusion therapy and smaller infarct size may be associated with Q wave regression and improved outcomes. The most recent and highest quality study, published in 2013, suggests that Q wave regression is associated with improved LVEF and reduced infarct size, and that the classic ECG criteria for Q wave MI show the strongest correlation with infarct size 1.