venerdì 26 marzo 2010
Mechanical thrombectomy of the MCA
Figure 1: CT angiography of the head demonstrates a left MCA occlusion at the distal M1 area. There is visualization of distal vessels with filling by collaterals.
Figure 2, Figure 3, Figure 4, and Figure 5: CT perfusion images demonstrate increased transit time and poor flow in the left MCA territory. There is poor flow in the right posteroparietal region. There is generally preserved blood volume except for decreased volume in the left posterior watershed area. These findings are compatible with ischemia with some areas of infarct and fairly large area of preserved viability.
Diagnostic/therapeutic cerebral angiogram findings: Digital angiography confirms that the left M1 segment is occluded at its mid-portion (Figure 6). Subsequently, the Merci catheter is deployed in the region of the thrombus (Figure 7). Following Merci thrombectomy, there is recanalization of the left M1 segment of the middle cerebral artery (Figure 8).
Diagnosis: Mechanical thrombectomy of the MCA
Catheter-directed thrombectomy systems can be successfully applied towards salvaging areas of reversible ischemia detected on cerebral perfusion imaging.
The MERCI catheter thrombectomy technique involves insinuating the catheter’s coiled tip beyond the thrombus and then retracting the catheter, thereby extracting the clot material.
Until recent years, intravenous recombinant tissue plasminogen activator (TPA) administered within three hours following symptom onset was the only FDA approved treatment for acute stroke. However, mechanical thrombectomy has since emerged as an effective treatment option for acute cerebral ischemia. Indeed, satisfactory results have been achieved with mechanical thrombectomy in some patients that present beyond the time period for intravenous TPA administration has passed, up to about 8 hours. Specifically recanalization rates of nearly 70% have been reported using mechanical thrombectomy.
Various catheter-based devices and techniques have now been devised for mechanical thrombectomy in the cerebral arteries. Some of these include the use of a snare, the alligator retrieval system, the Phenox clot retriever, the Merci catheter, among others.
The Merci catheter thrombectomy technique consists of obtaining femoral artery access, guidewire insertion, and advancement of the catheter to the site of occlusion. Subsequently, the balloon is inflated and the coiled tip of the catheter is passed across the clot and engaged under angiography. The mesh helps trap thrombus material. Clot is retracted into the balloon guide catheter and out of the body. Finally, the balloon is deflated, thereby restoring blood flow.
The main complication of mechanical thrombectomy is intracranial hemorrhage, which occurs in an estimated 5 to 10% of patients.