A more comprehensive explanation can be supported by the following two observations: (1) the normal preoperative scan and angiogram in most patients with “steal” and the normal follow-up angiograms available in some, and (2) pathologic examination of lung biopsy specimens in a number of these patients that have shown extensive pulmonary hypertensive changes in the small distal arteries*— changes not detectable by routine angiography. We speculate that these changes, like those in patients with congenital right-to-left shunts, are induced by the high flows and pressures to which the “open” vascular bed is exposed for months to years in patients with chronic thromboembolic pulmonary hypertension (C T-E PH). We further speculate that such hypertensive changes in the vascular bed that was “open” preoperatively may reduce flow to these zones postoperatively as pulmonary flow is diverted to the relatively normal microcirculation distal to endarterectomized segmental arteries. buy ventolin inhalers
A final potential explanation might exist, namely: that surgical disruption of the pulmonary vascular endothelium may induce a state of nonresponsive vasodilatation in the endarterectomized areas. Evidence for this hypothesis is primarily circumstantial.
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