Intestinal ischemia whether resulting from emboli, thrombosis or strangulation obstruction continues to be a serious and potentially fatal condition. We have pioneered the use of Superconducting Quantum Interference Device (SQUID) magnetometers for biomagnetic recordings of gastrointestinal smooth muscle activity in vitro, and in both animal and human subjects. This non-invasive, non-contact measurement of biomagnetic currents in smooth muscle demonstrates the feasibility of using SQUIDs to investigate human intestinal smooth muscle physiology. SQUIDs have unique fundamental advantages over cutaneous electrode recordings of intestinal electrical activity because magnetic fields readily penetrate layers of fat while electrical fields do not and cutaneous electrode recordings of human small bowel can not be routinely obtained. SQUIDs represent a striking new diagnostic device that has no equivalent except for invasive surgery and placement of electrodes onto the bowel surface. Hypothesis 1: Mesenteric ischemia causes uncoupling and arrhythmias of intestinal smooth muscle detectable in externally recorded magnetic fields. We will develop models to explain the arrhythmias, uncoupling and the effects of intervening tissue on the externally recording magnetic fields. Advanced analysis techniques to discriminate ischemic bowel from normal signals will be developed base upon our knowledge of smooth muscle behavior during ischemia. We will characterize for the fist time the magnetic currents in recordings taken during and after surgical exploration. Hypothesis w: Mesenteric ischemia causes sustained polarization of affected smooth muscle cells resulting in injury currents detectable in the externally recorded magnetic fields. Injury currents have been previously demonstrated to occur and be detectable magnetically in cardiac animal and human studies to detect this phenomenon. The new multichanel SQUID specifically designed for study of human intestinal magnetic fields developed and built as part of a SBIR grant will be available for use and will give us an extraordinary opportunity for the first time to explore smooth muscle pathophysiology during intestinal ischemia-one of the most deadly diseases known to man.
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