Which type of clots does alteplase seem to dissolve more effectively?

Alteplase is a tissue plasminogen activator (tPA) that specifically enhances the conversion of plasminogen to plasmin, which is crucial in the breakdown of fibrin in clots. This mechanism of action makes alteplase particularly effective for dissolving newer clots, as these clots are rich in fibrin and more susceptible to the effects of thrombolytic therapy.

Newer clots typically consist of a higher percentage of plasmatic components and exhibit a more fragile structure compared to older ones. As time progresses, clots can become more organized and harder, making them less responsive to the thrombolytic effects of alteplase. Thus, it's the recent formation of these clots and their active fibrin presence that allows alteplase to effectively break them down.

On the other hand, while thromboembolic clots (which include both older and newer types) might be amenable to treatment, it is primarily the newer clots that respond better to alteplase. Chronic clots or older clots are generally denser and have a different composition, which makes them less amenable to rapid dissolution by thrombolytics.