myocardial infarction leads to impairment of ventricular function because
The heart cannot effectively pump as a result of the infraction.
Myocardial infarction
Stroke is also a risk, either as a result of clots transmitted from the heart during PCI, as a result of bleeding following anticoagulation or as a result of disturbances in the heart's ability to pump effectively as a result of the infarction. 
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Myocardial infarction [SEP] Complications
Complications may occur immediately following the myocardial infarction or may take time to develop. Disturbances of heart rhythms, including atrial fibrillation, ventricular tachycardia and fibrillation and heart block can arise as a result of ischemia, cardiac scarring, and infarct location. Stroke is also a risk, either as a result of clots transmitted from the heart during PCI, as a result of bleeding following anticoagulation or as a result of disturbances in the heart's ability to pump effectively as a result of the infarction. Regurgitation of blood through the mitral valve is possible, particularly if the infarction causes dysfunction of the papillary muscle.