Magnetocardiographic Noninvasive Imaging of the Right Atrium Stretchability due to Short-term Overload during Respiratory Maneuvers

摘要

Magnetocardiography (MCG) as an integrative imaging method is useful for assessment of cardiopulmonary interactions related to the functional right atrium (RA) hemo-dynamic overload (FRAO) that occurs during the Valsalva and inspiratory breath holding (IBH) maneuvers. The purpose of this study was to determine changes in a distribution pattern of an instantaneous summary magnetic field (ISMF) generated during the depolarization phase of the atria (P wave of the PQRST magnetocardiocycle) in subjects with FRAO. MCG examinations were carried out at rest and during the maneuvers with the use of the 9-channel MCG system "MAC-SCAN-09" working in an unshielded space. The investigated group included 30 healthy males, aged 15-35 years, all performing IBH test and ten of them the Valsalva maneuver. We assessed on the ISMF map at the Ppeak point of time of the P wave during the maneuvers: 1) a direction of the null isoline (NI) curving along the transversal axis (TA) of the ISMF map; 2) a delta increment in the right atrium "stretchability vector" (RASV) length. Our study revealed that during FRAO in both maneuvers there was a general, with individual manifestations, trend for: 1) the NI to curve downward and rightward along the TA of the ISMF to the area of the RA mm. pectinati projection on the ISMF map; 2) the positive delta increment in the RASV length. Our study showed that MCG provided a novel integrative approach to qualitative and quantitative assessment as well as imaging of the RA myocardium property to stretch and generate magnetic fields in response to the stretch caused by its functional short-term overload. The MCG method gives an excellent opportunity to noninvasively research the effect of a short-term load on function of the stretch-activated channels and ionic currents that are involved in mechanoelectrical feedback mechanism in the intact human heart.