left ventricular pseudoaneurysm
Left ventricular pseudoaneurysms are false aneurysms that result from contained myocardial rupture, and are a rare complication of myocardial infarction (MI). They should not be confused with left ventricular aneurysms, which are true aneurysms containing all the layers (endocardium, myocardium, and epicardium).
Left ventricular pseudoaneurysm formation typically results in the early period following myocardial infarction, and is consequent to rupture of the myocardial free wall (most frequent 3-7 days post-MI) . The cardiac rupture is contained by adherent pericardium or scar tissue.
Myocardial rupture is usually rapidly fatal, however, in this scenario, it fortuitously becomes limited by a pericardial adhesion. Thus, the pseudoaneurysm wall consists only of the epicardium, pericardium and hematoma. In contrast, a left ventricular aneurysm has a wall of scarred myocardium and endocardium.
Other associations include:
- mitral valve surgery
- bacterial endocarditis
- previous chest trauma
Tends to be situated in the posterior and lateral wall segments.
Chest radiographs may show left ventricular outpouching, usually located posterolaterally. The pseudo-aneurysm can calcify after many years.
The increase in size on follow-up radiographs suggests the diagnosis of pseudoaneurysm rather than a left ventricular aneurysm.
Echocardiography typically shows the pseudoaneurysm as a saccular outpouching which originates from a sharp discontinuity of the left ventricular endocardial border. Compared to true aneurysms, pseudoaneurysms have a characteristically narrow neck; the end-systolic orifice diameter to maximal aneurysmal diameter is typically < 0.5, with aliasing and bidirectional flow visualized by color flow and spectral Doppler. The pericardial space may also demonstrate spontaneous echo contrast and echogenic thrombus . In the case of pseudoaneurysms post-myocardial infarction, adjacent myocardium in the affected vascular distribution will often be dyskinetic, echogenic and thin (<30% wall thickness, as compared to adjacent segments). Adjacent, unaffected segments often demonstrate compensatory hyperkinesis.
Cardiac CT-gated scan allows for the measurement of an aneurysm in many axes. Often shows a narrow neck: the neck of an aneurysm tends to be smaller than the aneurysm body with a ratio of the breach in the wall to the maximal diameter of the pseudoaneurysm of <50% (with most being 25-50% ).
MRI usually shows a dyskinetic segment with focal bulging of the pericardium. Mural thrombus is also frequently seen. In some cases, delayed enhancement of the pseudoaneurysm may be seen .
Treatment and prognosis
Approximately 25% (range 19-32%) of patients are at risk of fatal ventricular rupture, and about 30-45% of left ventricular pseudoaneurysms will eventually rupture. Most ruptures will occur in the early postoperative period .