Postmortem Histologic Evaluation Research Articles

Fat embolism and acute hypotension during vertebroplasty: an experimental study in sheep.

An experimental study of cardiovascular complications that arise during vertebroplasty was conducted. To investigate the sequential occurrence of fat embolism and hypotension during vertebroplasty. Vertebroplasty, the augmentation of vertebrae with polymethylmethacrylate, is a technique for treating osteoporotic compression fractures and achieving prophylactic stabilization of osteoporotic vertebral bodies at risk of fracture. However, there is concern that fat embolism and acute hypotension could occur as in a variety of other orthopedic procedures. In six sheep, 6 mL of polymethylmethacrylate was injected unilaterally into L1. Transesophageal echocardiography monitored the pulmonary artery for echodense particles. Heart rate, arterial and venous pressures, and blood gas values were recorded before and for 25 minutes after injection. The lungs were subjected to postmortem histologic evaluation and compared with lung specimens from two sheep that had not undergone vertebroplasty. Injection of cement elicited a very rapid decrease in heart rate (within 2 +/- 1 seconds) and a rapid increase in venous pressure (within 3 +/- 1 seconds), which was followed by a fall in arterial pressure (within 5 +/- 2 seconds) (phase 1). Thereafter, showers of echogenic material appeared (within 6 +/- 1 seconds) and lasted for 138 +/- 36 seconds. A second more severe fall in arterial pressure was observed beginning at 18 +/- 2 seconds (phase 2). The injection resulted in an increase in partial pressure of carbon dioxide and a decrease in pH. The histology showed intravascular fat globules and bone marrow cells in lung tissue. The results suggest that immediately after cement injection, there was a reflex fall in heart rate and arterial pressure. The second fall in arterial pressure was a consequence of fat emboli passing through the heart and getting trapped in the lungs.

Feasibility of using a swine portal vein containing a metallic stent for creating a portacaval shunt.

We evaluated the feasibility of using a metallic stented portal vein as a conduit for portacaval shunt in pigs. A metallic self-expanding stent was placed in the portal vein of five pigs under combined ultrasound and fluoroscopic guidance via a percutaneous transhepatic approach. After 6 weeks, a portacaval shunt was performed using the stented portal vein as a conduit. A single angiogram followed immediately by sacrifice and histologic examination was performed on each pig at a varying time interval postshunt. One pig died 3 days after the shunt procedure because of a presumed surgical technical failure and a consequent thrombosed portal vein. Angiographic patency of the portacaval shunt was confirmed in the four remaining pigs. Postmortem histologic evaluation showed more complete endothelialization and subintimal organization in the more chronic stents. Thrombus occurred only in the stent of the pig that died. There was no significant luminal obstruction in the other four stents. Our results suggest that a stented portal vein can be used successfully as a conduit for portacaval shunt in pigs.

Noninvasive arterial occlusion using MRI-guided focused ultrasound

The purpose of this work was to test the hypothesis that reproducible and sustainable arterial occlusion can be induced by focused ultrasound energy deposition noninvasively within deep tissue. An MRI-compatible focused ultrasound transducer was used to sonicate a branch of the renal artery (diameter about 0.6 mm) in vivo (nine rabbits). An intravenous MRI contrast agent bolus was injected about 30 min and up to 7 days after the sonication. After follow-up, in vitro magnification x-ray angiograms were obtained and the kidneys were fixed in formaldehyde for histologic study. The ultrasound pulses resulted in complete cessation of blood flow, as shown by the gradient echo images. In seven of the nine rabbits, a wedge-shaped unenhanced area was seen at the part of the kidney that was perfused by the vessel after the contrast agent injection. This area extended laterally (outside of the sonicated volume) to the cortical surface of the kidney. The x-ray angiograms showed that the artery was completely occluded. Postmortem histologic evaluation showed an infarcted tissue volume corresponding to the wedge shape seen in the images. This study showed that appropriately focused ultrasound can be used to close arteries noninvasively. This finding has significant clinical potential.