title: Noninvasive Determination of HV Interval Using Magnetocardiography.
abstract: BACKGROUND
  The His-ventricular (HV) interval is an important index of atrioventricular conduction, but at present can be reliably measured only during an invasive electrophysiology (EP) study. Magnetocardiography (MCG) is a noninvasive measurement of weak magnetic fields generated by the heart. We compared HV interval noninvasively assessed using MCG with the corresponding values measured directly in an EP study.
  
  
  METHODS
  MCG was measured using a 37-channel system inside a magnetically shielded room in patients who had previously undergone an EP study. His-bundle potential was identified in the PR segment after signal averaging. Magnetic field maps representing the spatial distribution of ramp-like signals in the PR segment generated at various instants of time were used to identify His-bundle signals in cases where the deflection representing the His was ambiguous.
  
  
  RESULTS
  The study included 23 patients (14 male, nine female) with a wide range of HV intervals measured during EP study (49 ± 17 ms, range 35-120 ms). In 21 (91%) subjects, discernible His-bundle signals are observed in the PR segment of MCG traces. HV intervals measured between the two methods showed a correlation (r2= 0.87, P < 0.0001) with a mean difference of 5.4 ± 3.2 ms.
  
  
  CONCLUSIONS
  With the use of new criteria to identify the His-bundle deflection in signal-averaged MCG signals, we report a high success rate in noninvasive HV interval measurement and a good agreement with those from EP study. The results encourage the use of MCG as a noninvasive method for measurement of the HV interval.
authors.affiliation: Magnetoencephalography Laboratory, SQUIDs and Applications Section, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.
authors.forename: Sengottuvel
authors.initials: S
authors.lastname: Senthilnathan
authors.affiliation: Department of Cardiology, Jawaharlal Institute for Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: Raja J
authors.initials: RJ
authors.lastname: Selvaraj
authors.affiliation: Magnetoencephalography Laboratory, SQUIDs and Applications Section, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Patel
authors.affiliation: Department of Cardiology, Jawaharlal Institute for Postgraduate Medical Education and Research, Puducherry, India.
authors.forename: Santhosh
authors.initials: S
authors.lastname: Satheesh
authors.affiliation: Magnetoencephalography Laboratory, SQUIDs and Applications Section, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.
authors.forename: Gireesan
authors.initials: G
authors.lastname: Katholil
authors.affiliation: Magnetoencephalography Laboratory, SQUIDs and Applications Section, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.
authors.forename: Madhukar P
authors.initials: MP
authors.lastname: Janawadkar
authors.affiliation: Magnetoencephalography Laboratory, SQUIDs and Applications Section, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.
authors.forename: Thimmakudy S
authors.initials: TS
authors.lastname: Radhakrishnan
mesh_terms: D000328:Adult; D000465:Algorithms; D001283:Atrioventricular Node / Q000503:physiopathology*; D002036:Bundle of His / Q000502:physiology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006801:Humans; D053798:Magnetocardiography / Q000295:instrumentation*; D008297:Male; D009431:Neural Conduction; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: HV duration; His-bundle magnetic field; MFM; SAMCG