The marked potentiation of rtPA induced pulmonary thrombolysis by increased flow per se, is likely explained by an increase in rtPA delivery to thrombi in partially obstructed vascular units. It is also possible that the increase in cardiac output which occurred with hydralazine and with an open A-V fistula washed out, and thus, diluted clotting factors in the vicinity of the thrombus. Such an effect would tend to prevent or minimize the deposition of fibrin on the surface of the clot and allow unimpeded rtPA-induced thrombolysis. This mechanism has been invoked to explain how pretreatment with heparin enhances rtPA-in-duced thrombolysis. buy ventolin inhalers
Other studies have reported results suggesting that flow may be important in affecting thrombolysis. For example, Tendera et al described factors influencing the probability of reperfusion with intracoronary ostial infusion of streptokinase or urokinase in patients with acute myocardial infarction. The strongest predictor of reperfusion was site of occlusion (p = 0.0004). Arteries with proximal occlusion recanalized 74 percent of the time vs 38 percent for distal occlusion. The authors speculated that the higher probability of proximal thrombolysis may be related to local availability of the thrombolytic agent and/or plasminogen. In a distal occlusion, a “cul-de-sac” phenomenon and/or run-off through proximal branches may prevent penetration of the thrombolytic agent to the clot.