Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 144

Pseudoaneurysm is a myocardial rupture that has been sealed by pericardium, organized thrombus and fibrosis. Unlike a true LV aneurysm, the LV pseudoaneurysmal wall does not contain any myocardium. Note that thrombus is layered inside both the LV aneurysm and LV pseudoaneurysm. A pseudoaneurysm may also be seen after trauma or cardiac surgery (especially mitral surgery, at the posterobasal level) (Figure 2.7).

A pseudoaneurysm has a 40–50% risk of progressing to a full rupture, and thus warrants urgent surgical suturing. Rupture often occurs in the first week,¹⁵⁹ but rupture of chronic pseudoaneurysms, even small pseudoaneurysms, has been described.¹⁶⁰ Conversely, a true aneurysm does not rupture (it may, rarely, rupture in the first 2 weeks of MI, but does not rupture later on, once it is fully fibrosed).

The distinction between a true LV aneurysm and a pseudoaneurysm is made by echo: a pseudoaneurysm has a narrow neck with a neck-to-internal diameter ratio <0.5,¹⁶¹ although occasionally in large cases, it can be 0.5–1.¹⁵⁹ Doppler may also support the diagnosis of

pseudoaneurysm by showing a to-and-fro turbulent flow through the narrow neck, which corresponds to a murmur on exam. However, echo-Doppler does not always allow this distinction. MRI may be used in equivocal cases and shows loss of epicardial fat across the pseudoaneurysm.

Figure 2.7 LV aneurysm and LV pseudoaneurysm.

In comparison with the normal LV, note the bulging pocket seen in LV aneurysm and LV pseudoaneurysm. The aneurysmal wall consists of thin scarred myocardium ± clot, whereas the pseudoaneurysmal wall consists of adherent pericardium and clot (stars). The neck of the LV pseudoaneurysm is narrow; the neck/internal diameter ratio is <0.5 in pseudoaneurysm vs. >0.5, usually 0.8–1, in aneurysm (ratio of double arrows). The dyskinetic motion of the aneurysm is indicated by the horizontal arrows.

Left ventriculography is also highly accurate in distinguishing an aneurysm from a pseudoaneurysm.¹⁵⁹ In case of a pseudoaneurysm, it shows a pocket with a contrast stain that persists over multiple beats. Moreover, in contrast with a true aneurysm, the coronary arteries do not extend over the pseudoaneurysmal wall.