Mechanical complications of myocardial infarction

What it is

Ischemic necrosis after myocardial infarction can rupture the structures of the heart. These mechanical complications sit alongside the other complications of STEMI: arrhythmias (AF, VF, bradycardia, AV block), pump dysfunction and heart failure, pericarditis and Dressler syndrome, and left ventricular thrombus. The mechanical group covers RVD, VSD, papillary muscle rupture and left ventricular free wall rupture, with left ventricular aneurysm and pseudoaneurysm as later complications. Arrhythmias and heart failure may occur at any time after acute MI, and reinfarction may occur at any time as well, with the risk increasing over time.

How it presents

Each has its own timing and its own bedside picture.

• Papillary muscle rupture: reported as 3-5 days post-MI in one source and as usually occurring 2-7 days after myocardial infarction in another. Ischemic necrosis ruptures the papillary muscle and produces severe acute mitral regurgitation, with a new holosystolic blowing murmur over the 5th ICS on the midclavicular line, dyspnea, cough, bilateral crackles and hypotension. Anterolateral papillary muscle rupture follows occlusion of the LAD and/or LCx, which give it a double supply. Acute pulmonary edema and cardiogenic shock follow.
• Ventricular septal rupture: 3-7 days post-MI. Ischemic necrosis produces septal rupture and a left-to-right shunt, with a harsh holosystolic murmur at the left sternal border, biventricular failure and hypotension.
• Free wall rupture: 5-14 days post-MI. Myocardial rupture leads to pericardial tamponade and obstructive shock, with sudden hypotension, distant heart sounds, pulsus paradoxus and PEA arrest. Electrical alternans may be seen.
• Left ventricular aneurysm: weeks to months. Thin, scarred myocardium forms a dyskinetic segment, with persistent ST elevations in the leads of the prior infarction, heart failure and thromboembolism.
• Right ventricular infarction: early, in the acute MI. RCA occlusion impairs preload and gives hypotension, JVD, clear lungs and Kussmaul's sign.