Mechanical Complications

The mechanical complications of STEMI are:

Mitral regurgitation

Mitral regurgitation is the commonest mechanical complication of STEMI. Patients develop signs of acute cardiac failure (associated with both pulmonary oedema and hypotension). The underlying pathological causes of acute mitral regurgitation in this setting are chordal rupture, papillary muscle infarction and rupture, or functional regurgitation due to dilatation of the mitral valve ring associated with left ventricular dilatation. Clinical signs of sudden haemodynamic deterioration associated with a new murmur are suggestive of mitral regurgitation. Echocardiography confirms the diagnosis and distinguishes mitral regurgitation from ventricular septal rupture. Definitive treatment of this complication requires urgent surgery and reperfusion of the infarct related coronary artery. In the meantime, treatment is aimed at controlling pulmonary oedema and supporting the circulation.

Ventricular septal rupture

Ventricular septal rupture is a complication that occurs most commonly with anterior or posterior AMI. The clinical presentation is similar to mitral regurgitation with haemodynamic compromise and a pan-systolic murmur. Echocardiography is required to distinguish between these two conditions. Definitive treatment requires urgent surgery to repair the defect, with interim measures to support the circulation, and reperfusion of the infarct related coronary artery.

Cardiac rupture and tamponade

Echocardiagram demonstrating large pericardial blood collection (LV = left ventricle, RV = right ventricle, LA = left atrium, RA = right atrium, * = blood in pericardium).

Acute cardiac wall rupture is a cause of sudden death following AMI, and is more common in the elderly. In subacute cardiac rupture the pericardium contains the blood loss from myocardial rupture and a tamponade develops. There is sudden haemodynamic deterioration with signs of a cardiac tamponade: hypotension, distended neck veins and muffled heart sounds.
Diagnosis is confirmed by echocardiography and, whilst pericardiocentesis may temporarily improve the haemodynamic state, definitive management requires urgent surgery.