Robert S Dieter

Postcarotid Endarterectomy Hyperperfusion or Reperfusion Syndrome

Background and Purpose— Hyperperfusion syndrome (HS) after carotid endarterectomy (CEA) has been related to impaired cerebrovascular autoregulation in a chronically hypoperfused hemisphere. Our aim was to provide new insight into the pathophysiology of the HS using magnetic resonance imaging (MRI) studies with diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). Methods— Five out of 388 consecutive patients presented 2 to 7 days after CEA, partial seizures (n=5), focal deficits (n=5), and intracerebral hemorrhage (n=3). In 4 patients, using sequential examinations, we identified vasogenic or cytotoxic edema by DWI; we assessed relative interhemispheric difference (RID) of cerebral blood flow (CBF) by PWI; and we measured middle cerebral artery mean flow velocities (MCA Vm) by transcranial Doppler (TCD). Results— None of the patients presented pathological DWI hyperintensities, consistent with the absence of acute ischemia or cytotoxic edema. In 2 patients, we found an MRI pattern of reversible vasogenic edema similar to that observed in the posterior leukoencephalopathy syndrome. Middle cerebral artery (MCA) mean flow velocities (Vm) were not abnormally increased at any time. PWI documented a 20% to 44% RID of CBF in favor of the ipsilateral to CEA hemisphere. Conclusions— HS can occur in the presence of moderate relative hyperperfusion of the ipsilateral hemisphere. MCA Vm values may not accurately reflect RID of CBF over the cortical convexity. We suggest that the hemodynamic pathogenetic mechanisms of the HS are more complicated than hitherto believed and that they may be more accurately described by the term “reperfusion syndrome.”

Use of Gadolinium-Based Angiography for Renal Artery Stenting in a Patient With Renal Insufficiency A Case Report

The number of percutaneous diagnostic and interventional procedures performed continues to increase. Despite the use of various methods to reduce the incidence of contrast-induced nephropathy, the development of renal failure remains a significant problem with iodinatedbased contrast agents. Patients with a baseline renal insufficiency are at considerably higher risk of permanent renal deterioration following exposure to iodinated contrast. The authors report a successful case of percutaneous stenting of the renal artery using a gadolinium-based contrast agent in a high-risk patient with renal insufficiency.

Acute aortic syndromes: aortic dissections, penetrating aortic ulcers and intramural aortic hematomas

Acute aortic syndromes, including dissections, intramural hematomas and penetrating aortic ulcers, are a catastrophic clinical entity that are relatively uncommon. A high index of clinical suspicion along with proper imaging modalities are critical in making a prompt and accurate diagnosis for immediate management and to improve survival of the patient.

Visceral Arterial Obstructive Disease

The gastrointestinal tract makes up a large portion of the intracavitary abdominal organs. The arterial and venous supply of the lower esophagus, stomach, duodenum, small bowel, and colon seldom cause major ischemic problems. However, major ischemic problems are cause for significant concern when they occur on an acute basis. The chronic vascular obstructive process is much less dramatic and may go unnoticed until profound effects (e.g., weight loss and abdominal pain) take place. The liver, pancreas, and spleen may also have occlusive vascular disease on both arterial and venous bases. We concentrate in this chapter on the gastrointestinal tract and to a lesser degree on the liver and pancreas.