The effect of biometric and cardiovascular parameters on the orientation of cardiac magnetic field maps

Abstract

It has been shown in a number of studies that the orientation of cardiac magnetic field maps (MFM) is affected by pathological changes resulting from coronary artery disease (CAD). Aim of this work was to examine whether specific biometric or cardiovascular parameters confound MFM orientation. We studied 102 patients who had suffered acute ST elevation myocardial infarction (STEMI) and 39 age-matched healthy controls. MFM orientation was determined on the basis of 180s magnetocardiograms obtained at rest. The percent deviations from normal orientation (devOR) during the QT interval were calculated. The distribution of devOR was compared with respect to age, gender, body-mass index (BMI), RR interval, blood pressure and electrical heart axis while taking disease state into account. Group differences were tested statistically using non-parametric measures and regression analysis, as appropriate, with p<0.05 considered significant. devOR differed significantly between healthy and STEMI subjects (4±7% vs. 34±18%, p<0.001). Regression analysis showed no dependency of devOR on age, BMI, RR interval or systolic/diastolic blood pressure in either group. As expected, females had a lower BMI but had no differences with respect to age, blood pressure or RR interval values. Overall, there was a tendency for devOR values to decrease from left to right electrical heart axis orientation (p=0.048). This was not apparent in the subgroups. MFM orientation was not affected by gender, biometric or basic cardiovascular parameters except for electrical heart axis. The latter should be considered when evaluating MFM orientation values. The overall independence of biometric and cardiovascular measures facilitates the usage of MFM orientation in the diagnostics of CAD.