Review Question - QID 212425

This patient is presenting with decreased exercise tolerance after a myocardial infarction with normal troponins and an ECG demonstrating a ventricular aneurysm suggesting an expected clinical course after a myocardial infarction. Collagen deposition and scar formation are expected to occur 2-8 weeks after a new myocardial infarction.

A myocardial infarction occurs when ischemia leads to necrosis of the cardiac myocytes. The initial damage that occurs to the heart leads to a cascade of cellular changes in the remodeling process. Collagen deposition and scar formation is the ultimate/final part of the remodeling process and typically occurs 2-8 weeks after a myocardial infarction. Since collagen lacks the contractile properties of a myocyte, an aneurysm can occur at the location of the scar. This can present with a hypokinetic or dilation on echocardiography and with ECG changes.

Figure A demonstrates the expected waveforms that could be seen in a ventricular wall aneurysm. Note that there can be changes (typically in the precordial leads) which may demonstrate Q- and T-waves with a decreased amplitude. ST elevation can be seen; however, in the setting of this patient's normal troponins (and the absence of hyperacute T-waves seen in a new myocardial infarction) it is likely that these changes reflect scar formation with an aneurysm present rather than a new infarction.

Incorrect Answers:
Answer 1: Coagulation necrosis and marginal contraction band necrosis occur 12-24 hours after a myocardial infarction.

Answer 3: Early coagulation necrosis and edema occur 4-12 hours after a new myocardial infarction.

Answer 4: Granulation tissue and neovascularization occur 10-14 days after a new myocardial infarction.

Answer 5: Macrophage phagocytosis of dead cells occurs 5-10 days after a new myocardial infarction.

Bullet Summary:
Collagen deposition and scar formation occurs 2-8 weeks after a myocardial infarction and can lead to aneurysm formation.