Which parameters on magnetic resonance imaging determine Q waves on the electrocardiogram?

Area of Science:

• Cardiology
• Medical Imaging
• Pathophysiology

Background:

• Q-wave myocardial infarctions (MIs) often show nontransmural scarring, while non-Q-wave MIs can exhibit transmural scars.
• The underlying pathophysiology of Q waves in myocardial infarction remains incompletely understood.
• Magnetic resonance imaging (MRI) is crucial for assessing cardiac function, viability, and scar tissue post-MI.

Purpose of the Study:

• To investigate the relationship between electrocardiogram (ECG) Q waves and cardiac scar characteristics determined by MRI.
• To identify MRI-derived parameters that best predict the presence of Q waves in patients with coronary artery disease and prior MI.

Main Methods:

• Sixty-nine patients with coronary artery disease and history of MI underwent a comprehensive MRI protocol.
• The protocol included resting MRI, dobutamine stress MRI, and contrast-enhanced MRI to assess function, viability, and scar.
• Key parameters analyzed were left ventricular ejection fraction, volumes, wall thickness, contractile reserve, scar transmurality, spatial extent, total scar score, and quantified scar percentage.

Main Results:

• Q waves were present in 57% of the patients.
• Univariate analysis revealed transmurality, spatial extent, total scar score, and quantified scar percentage as predictors of Q waves.
• Multivariate analysis identified quantified percent left ventricular scar tissue as the strongest predictor (90% sensitivity/specificity at 17% cut-off).

Conclusions:

• Quantified percent scar tissue on contrast-enhanced MRI is the most accurate predictor of Q waves on ECG.
• Spatial extent of infarction emerged as the next best predictor when scar percentage was excluded.
• These findings enhance the understanding of the pathophysiologic basis of Q waves in myocardial infarction using advanced imaging techniques.