What are the causes of a new pansystolic murmur following myocordial infarction?

The development of a new systolic murmur following myocardial infarction often may be catastrophic due to the hemodynamic instability that usually accompanies this murmur. The etiologies include:

Rupture and/or dysfunction of a left papillary muscle causing severe mitral regurgitation

Rupture of the interventricular septum

Right ventricular infarction and tricuspid regurgitation

False aneurysm and rupture of the external wall

What is the clinical presentation of right ventricular infarction?

Right ventricular (RV) infarction is observed in 29-36% of patients presenting with acute inferoposterior or true posterior myocardial infarction. Isolated RV infarctions are rare. Ischemia or infarction of the RV may lead a range of disorders, from minimal hemodynamic abnormalities to its most severe presentations, which include jugular venous distention, clear lung fields and hypotension, a positive Kussmaul’s sign, and RV third and fourth sounds.

How is RV infarction diagnosed and what is its recommended management?

The electrocardiogram (ECG) demonstrates the features of acute inferior myocardial infarction (direct posterior or lateral infarction also may be present) and ST elevation in leads V4R-V6R. Hemodynamic evaluations with a pulmonary artery catheter usually demonstrate an elevated right atrial or RV end-diastolic pressure, a normal or minimally elevated pulmonary artery pressure, and usually normal or low pulmonary capillary wedge pressure.

The mainstay of therapy is fluid administration in order to maintain a wedge pressure of 18-20 mmHg. Inotropic support may be needed and, rarely, intra-aortic balloon pump insertion is indicated in patients with refractory hypotension. Vasodilator drugs should be strictly avoided.

What is the difference between true and false aneurysms that develop after myocardial infarction?

A true ventricular aneurysm is a circumscribed noncontractile outpouching of the left ventricle and develops in 8-14% of patients who survive myocardial infarction. The wall of the true aneurysm usually is composed of fibrous tissue as well as necrotic and viable myocardium. In contrast, a psuedoaneurysm results from rupture of the left ventricle free wall and is concealed by the adjacent pericardium. The wall of the pseudoaneurysm is composed of fibrous tissue and no myocardial elements. Rupture is frequent with pseudoaneurysms but rarely seen in true aneurysms.

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