Sequential changes of magnetocardiogram in rat models of experimental myocardial infarction

Kim, Mi Sung; Park, Young Sun; Kwon, Sun Gil; Ji, Jeong Hoon; Shin, Jong Sung; Oh, Kwang Sik; Yang, Yong Mo; Youn, Tae Jin; Kim, Dong Woon; Cho, Myeong Chan; Lee, Yong Ho; Kwon, Hyukchan

Abstract

BACKGROUND
Magnetocardiogram (MCG), which records the changes of magnetic fields generated by the heart's electrical activity, theoritically can provide unique data for clinical application. To date, MCG has been investigated only at a single time point after myocardial infarction (MI) with severe left ventricular dysfunction in rats. The purpose of the present study was to investigate sequential changes of MCG after MI and to evaluate effects of infarct size on MCG.
METHODS
Acute MI were induced by the permanent ligation of left coronary artery in 22 rats. Magnetic fields were recorded just above a rat with Nb Superconducting Quantum Interference Device (SQUID) gradiometer inside a magnetically shielded room. MCG was measured before and immediately after surgery and it was subsequently recorded at the time points of 1, 4 and 6 hours postoperatively. MCG was also measured at 1, 3, 7 and 21 days after surgery.
RESULTS
Elevation of ST segment and appearance of pathological Q wave on the MCG were evident immediately after the ligation of coronary artery and persisted to 6 hours after MI. On MCG, ST segment was depressed and T wave was inverted from 1 day after MI. In rats with small- and moderate-sized MI (infarct size< 30%), ST depression returned to near the isoelectric level and Q wave disappeared from 7 days after MI. However, ST depression and Q wave were still present in rats with larger infarct (infarct size > or = 30%).
CONCLUSION
Evolutional changes of MCG were well-recognized up to 21 days after MI. Furthermore, the infarct size can be expressed by the extent of Q wave and ST segment depression on MCG. Taken together, these data indicate that MCG is a helpful modality for the diagnosis, evaluation of infarct size and follow up after MI.