Embolism

Embolism is by far the most common cause of acute arm ischaemia, accounting for 74–100% of cases.

In the lower extremities, controversy exists regarding the ratio between arterial embolism and thrombosis, with diferent studies giving numbers ranging from 4:1 to 1:9.

The heart is invariably the most common origin of peripheral arterial emboli, and is responsible for 58–93% of cases. However, the pattern of the underlying heart disease has changed recently as the incidence of rheumatic valvular disease has decreased significantly

Cardiac Sources of Emboli

Nowadays, the most common sources of arterial emboli of cardiac origin are:

atrial ibrillation due to atherosclerotic heart disease, accounting for 32–75% of cases, followed by

myocardial infarction with mural thrombi formation, which is responsible for 21–32% of peripheral emboli.

Less common cardiac sources of emboli are:

idiopathic dilated cardiomyopathy

prosthetic valves

rheumatic mitral valve disease

intracavitary cardiac tumours (mainly myxomas)

paradoxical embolization through an intracardiac defect, usually a patent foramen ovale

fungal or bacterial endocarditis.

Noncardiac Sources

Noncardiac sources of emboli are being identiied with increasing frequency, at the expense of undetermined causes, the frequency of which has steadily decreased due to improvements in diagnostic methods. Noncardiac sources of emboli are nowadays found in 5–12% of patients, while in 9–12% the source of the emboli remains unknown.

Aneurysms are the most common noncardiac source of peripheral embolism, accounting for about 5% of distal emboli.

Ulcerated atherosclerotic plaques follow in order of frequency, carrying the risk of distal embolism from white thrombi adherent on their surface. Such emboli are usually sizeable, capable of obstructing major peripheral arteries.

A distinct variant of peripheral embolization due to an atherosclerotic plaque is atheroembolism, in which a portion of the plaque breaks of and undergoes embolization to peripheral arteries. Such emboli may evolve in three clinical forms:

1. The asymptomatic form, not diagnosed during the subject’s lifetime and only recognized in autopsy studies.

2. A benign form such as blue toe syndrome or cutaneous livedo, with a spontaneous mild prognosis.

3. A difuse multisystemic form with a very poor prognosis.

Cryptogenic Emboli

Despite complete diagnostic work-up, including complex investigations, the precise source of the emboli cannot be identiied in 5–12% of cases. Such emboli are called cryptogenic and represent either the limited sensitivity of current diagnostic modalities or, in some cases, confusion with local thrombosis in situ.

Дата добавления: 2014-12-23