Complications of Myocardial Infarction
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Complications of Myocardial Infarction
recurrent chest pain
if post-MI angina occurs (20-30%), patients often get PTCA or CABG
recurrent MI (5-20%) within first six weeks
cardiac arrhythmias and conduction defects (brady- and tachyarrhythmias)
extremely common w/ MI, major source of mortality before patient reaches hospital
Mechanisms
anatomic interruption of perfusion to structures of conduction pathway
accumulation of local metabolic factors and abnormal transcellular ion concentrations due to membrane leaks
autonomic stimulation
administration of potentially arrythmogenic drugs
Types
Ventricular Fibrillation
During first 48 hours probably related to electrical instability
After first 48 hours probably related to LV dysfunction
Supraventricular Arrythmias
Sinus bradycardia (excessive vagal stimulation or SA nodal ischemia)
Sinus tachycardia (pain, anxiety, CHF, drugs, volume depletion)
Atrial premature beats and atrial fibrillation (atrial ischemia or distension secondary to LV failure)
Conduction Blocks
May result from ischemia or increased vagal tone
right ventricular infarction
1/3 of those with MI of LV inferior wall will also get RV infact b/c both are supplied by right coronary artery (usually)
will get signs of right sided heart failure including JVD, profound hypotension (LV becomes underfilled)
mechanical complications, including:
papillary muscle rupture
can be rapidly fatal because of severe mitral regurgitation
ventricular free wall rupture
may occur within first 2 weeks of MI
more common in women and those with a hx of hypertension
results in cardiac tamponade, pseudoaneurysm (if rupture is incomplete and plugged with a thrombus)
ventricular septal rupture
develop left to right shunt
precipitates CHF by volume overload of pulmonary capillaries
ventricular aneurysm (VSD)
usually occurs weeks to months after MI as wall progressively weakens, but not peforated by phagocytic clearance of necrotic tissue
get localized outward bugle when ventricle contracts
rupture and tamponade do not develop
complications include thrombus formation, ventricular arrhythmias, heart failure
get persistent ST segment elevation (weeks after Q wave MI)
“pump” failure
impaired ventricular contractility and increased myocardial stiffness both lead to symptoms of heart failure
signs and symptoms include dyspnea, pulmonary rales, S3
treatment includes diuresis and vasodilator therapy
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