Noninvasive biomagnetic detection of intestinal slow wave dysrhythmias in chronic mesenteric ischemia

Abstract

Chronic mesenteric ischemia (CMI) is a challenging clinical problem that is difficult to diagnose noninvasively. Diagnosis early in the disease process would enable life-saving early surgical intervention. Previous studies established that superconducting quantum interference device (SQUID) magnetometers detect the slow wave changes in the magnetoenterogram (MENG) noninvasively following induction of mesenteric ischemia in animal models. The purpose of this study was to assess functional physiological changes in the intestinal slow wave MENG of patients with chronic mesenteric ischemia. Pre- and postoperative studies were conducted on CMI patients using MENG and intraoperative recordings using invasive serosal electromyograms (EMG). Our preoperative MENG recordings showed that patients with CMI exhibited a significant decrease in intestinal slow wave frequency from 8.9 ± 0.3 cpm preprandial to 7.4 ± 0.1 cpm postprandial (P < 0.01) that was not observed in postoperative recordings (9.3 ± 0.2 cpm preprandial and 9.4 ± 0.4 cpm postprandial, P = 0.86). Intraoperative recording detected multiple frequencies from the ischemic portion of jejunum before revascularization, whereas normal serosal intestinal slow wave frequencies were observed after revascularization. The preoperative MENG data also showed signals with multiple frequencies suggestive of uncoupling and intestinal ischemia similar to intraoperative serosal EMG. Our results showed that multichannel MENG can identify intestinal slow wave dysrhythmias in CMI patients.

Trial registration: ClinicalTrials.gov NCT00179036.

Keywords: magnetoenterogram; mesenteric ischemia; slow wave.

Fig. 1.

A and B: spatial distribution of the filtered magnetoenterogram (MENG) signals during baseline period and its corresponding power spectra. C and D: second-order blind identification (SOBI)-MENG components and its corresponding power spectra. E and F: reconstructed SOBI-MENG components and its power spectra showing how the SOBI-MENG components are distributed around the sensor array. The SOBI components used in the reconstruction are marked with *.

Fig. 2.

Reconstructed SOBI-MENG components (A and B) and corresponding power spectra (C and D) during pre- and postprandial period in a chronic mesenteric ischemia (CMI) patient before and after revascularization. Patient suffering from ischemia showed a decrease in the postprandial slow wave frequency. Similar changes were not observed after revascularization.

Fig. 3.

Intestinal slow wave frequency (mean ± SE) determined by SOBI-MENG components in CMI patients pre- and postrevascularization. *Dominant frequencies of SOBI-MENG components show a statistically significant postprandial decrease before revascularization. No statistically significant change between pre- and postprandial frequency was observed after revascularization.

Fig. 4.

Percent power distributed (PPD) in brady-, normo-, and tachyenteric frequency ranges for MENG recordings in CMI patients pre- and postprandial period, both before and after revascularization. *Statistically significant postprandial PPD changes.

Fig. 5.

Baseline recording using superconducting quantum interference device (SQUID) and serosal electrodes in a CMI patient and its corresponding power spectra: typical tracings recorded using SQUID (reconstructed SOBI-MENG components corresponding to the jejunal segment, 4 days before revascularization/17 wk after revascularization) (A), and serosal recording (EMG) from the ischemic jejunum just before/after surgical intervention (B). C and D: power spectra corresponding to reconstructed SOBI-MENG and EMG components.