In the absence of specifically designed pacemakers, the use of DDD pacemakers in the biventricular mode requires certain precautions, such as anti-PMT mode activation, disabling automatic sensitivity, and lengthening the postventricular atrial refractory period (PVARP), or mode switch to DVIR.

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To evaluate whether there is a relationship between the viscoelastic properties of the rectum and its surface, barium enema and rectal accommodation studies were performed under standard conditions in 46 subjects (25 adults, 21 children) with chronic idiopathic constipation. In adults, a significant correlation was found between rectal surface at barium enema and the minimum radius of rectal distention with a balloon necessary to higher wall tension changes (r = 0.68; P less than 0.01). In both adults (r = 0.48; P less than 0.05) and children (r = 0.57; P less than 0.01), negative correlations were found between the surface of the rectum and its elasticity. It is concluded that rectal accommodation studies produce data comparable to those of radiologic examinations and may therefore be used repetitively, and without fear of radiation, as follow-up studies on constipated patients.

An animal model was proposed to clarify the difference in occurrence of enterocolitis in congenital aganglionosis. When gaseous distention of the colon was localized to the rectosigmoid area, enterocolitis never occurred. On the contrary, when it involved the left colon, enterocolitis occurred in 13 of 15 patients. Intestinal blood flow rates were simultaneously measured in the left colon and rectum of six dogs by using labeled microspheres and expressed in function of the intraluminal pressure. Results show that for elevated values of intraluminal pressure, blood flow was significantly lower in the left colon than in the rectum. These results may explain why ischemia and necrosis occurred more frequently in the left colon than in the rectum.

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