Background
Definition
- Hemorrhagic transformation (HT) refers to hemorrhagic infarction that occurs after venous thrombosis or arterial thrombosis and embolism.
- The radiographic definition of HT is generally classified by the European Cooperative Acute Stroke Study (ECASS). On CT scans, the severity of HT is divided into two stages: hemorrhagic infarction (HI) and parenchymal hemorrhage (PH) with or without mass effect. Each stage is divided into two subtypes.
| Types of HT |
Mass effect |
Definition |
| Hemorrhagic infarction-1 (HI-1) |
Absence of mass effect |
Small petechial bleeding along the margins of the infarcted area |
| Hemorrhagic infarction-2 (HI-2) |
Absence of mass effect |
Confluent petechial bleeding within the infarcted area |
| Parenchymal hemorrhage-1 (PH-1) |
Mildmass effect |
Hematoma in <30% of the infarcted area |
| Parenchymal hemorrhage-2 (PH-2) |
Definite mass effect |
Hematoma in more than 30% of the infarcted area |
Epidemiology
- Large parenchymal hematomas and symptomatic intracerebral hemorrhage (sICH) are the most feared, tend to have a high mortality rate, and appear in up to 6% of patients after intravenous thrombolysis.
- Factors associated with hemorrhagic transformation
- old age, male, obese, febrile, hyperglycemia, hypertensive, high NIHSS score ≥ 22, large or embolic territorial strokes, atrial fibrillation, heart failure, renal impairment, previous stroke, diabetes.
Pathophysiology
Radiopathology
- Petechial HT also known as “red softening” due to (a) insufficient perfusion from adjacent collateral vessels or (b) reperfusion of infarcted tissues with weakened vessels (extravasation).
- (A) explains why HT occurs in patients with permanently occluded vessels
- (B) explains why the proportion of patients with HT is higher in those who receive reperfusion therapy than in those who do not receive reperfusion therapy.
(A) no HT (no bleeding regardless of reperfusion); (B) early HT (definite bleeding usually 6–24 h after stroke); (C) delayed HT (definite bleeding usually more than 24 h after ischemic stroke). The figure shows the relationship between HT probability and reperfusion (R) after ischemic stroke. The radiologic features differ from those of petechial hemorrhagic infarction and parenchymal hemorrhage. Petechial hemorrhagic infarction usually appears as tiny punctate regions in the hemorrhage and is often not individually resolved. In parenchymal hematomas or hemorrhage, radiological features on both CT and MRI, which combine the features of ischemic infarction and cerebral hemorrhage, overlap. HT, hemorrhagic transformation; ROS, reactive oxygen species.
Mechanism of HT from Ischemic Stroke
- The blood–brain barrier (BBB) is a physiological barrier between the brain parenchyma and brain circulation that nourishes brain tissue, filters various substances from the brain to the blood, and protects the brain.