Classification of pulmonary occlusive disease
| Type | Description | Operable? |
| 1 | Major vessel clot | Yes |
| Readily visible on opening pulmonary arteries | ||
| 20% of cases | ||
| 2 | Only thickened intima can be seen | Yes |
| Endarterectomy plane initially raised in the main, lobar or segmental vessels | ||
| ∼70% of cases | ||
| 3 | Distal disease | Yes |
| Confined to segmental and subsegmental branches | ||
| ∼10% of cases | ||
| 4 | Intrinsic small-vessel disease | No |
| Secondary thrombi may occur from stasis |
Data from [27].