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Myocardial Infarction and Functional Outcome Assessment in Pigs
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The effect of the Q wave infarct on left ventricular electromechanical function
Christine A O'Sullivan1, Ihab S Ramzy, Alison Duncan
1Cardiac Department, Royal Brompton Hospital and National Heart and Lung Institute, Imperial College School of Science, Medicine and Technology, Sydney Street, London, UK.
International Journal of Cardiology
|November 7, 2003
Summary
Q wave myocardial infarction (MI) causes significant left ventricular (LV) dysfunction and dimension changes. Non-Q wave MI primarily affects long-axis function, suggesting potentially reversible myocardial issues.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Cardiovascular Imaging
Background:
- Anterior myocardial infarction (MI) can be classified by the presence (Q wave MI) or absence (non-Q wave MI) of Q waves on an electrocardiogram.
- These classifications may reflect different underlying electrical and mechanical sequelae in the left ventricle (LV).
Purpose of the Study:
- To compare the left ventricular (LV) electrical and mechanical dysfunction between patients with Q wave anterior myocardial infarction (MI) and non-Q wave anterior MI.
- To elucidate the specific functional deficits associated with each type of anterior MI.
Main Methods:
- Utilized electrocardiography (ECG) and echocardiography to assess 54 patients with old anterior MI (39 Q wave, 15 non-Q wave) and 21 healthy controls.
- Analyzed resting LV minor and long axis function, including dimensions, fractional shortening, and timing of systolic and diastolic motion.
- Correlated ECG findings (Q waves) with echocardiographic evidence of myocardial scarring and regional wall motion abnormalities.
Main Results:
- Q wave MI was associated with a significantly higher prevalence of septal Q waves (84%) compared to non-Q wave MI (46%) and normals (10%).
- Q wave MI patients exhibited increased LV dimensions and reduced fractional shortening, alongside impaired LV long axis motion and delayed shortening/lengthening.
- Non-Q wave MI patients showed normal LV minor axis dimensions and fractional shortening but significant disturbances in LV long axis function, particularly affecting anteroseptal and lateral walls, with delayed long axis shortening and lengthening onset.
Conclusions:
- Q wave MI leads to significant increases in LV dimensions and reduced systolic function (fractional shortening).
- Non-Q wave MI, despite anterior wall hypokinesis, presents with preserved LV minor axis function but notable long axis systolic and diastolic disturbances.
- The absence of conduction abnormalities in non-Q wave MI suggests intrinsic myocardial dysfunction that may hold potential for reversibility.
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