title: Feasibility of his bundle pacing as an alternative pacing site: measurement of his refractoriness.
abstract: BACKGROUND
  Direct pacing of the His bundle has been proposed for permanent pacing to maintain physiological synchrony of ventricular activation. Measurement of His bundle refractoriness may be useful in predicting suitability of this technique in an individual. We sought to determine whether this could be measured consistently in patients, defining a normal range.
  
  
  METHODS
  His bundle pacing was performed in 20 consecutive patients (mean age 44.6 +/- 19.5, 5 male) undergoing electrophysiology study. Incremental and extrastimulus testing were performed from the His region to determine effective and functional refractory periods of the His bundle.
  
  
  RESULTS
  Consistent His capture was possible in 18 of 20 (90%) patients studied. Extrastimulus testing from the His region at a drive cycle length of 600 msec was successful in all of these patients. With loss of His capture, QRS duration prolonged 32%, and stimulus to atrial electrogram interval prolonged 49.6 +/-16.3 msec. The effective refractory periods at drive cycle lengths 600, 500, and 400 msec were 407 +/- 70 msec, 320 +/- 39 msec, and 336 +/- 54 msec, respectively. Corresponding functional refractory periods were 414 +/- 62, 371 +/- 52, and 329 +/- 32. Consistent capture with incremental His pacing was possible in 50% of patients, and 1:1 His capture was lost at mean cycle length 408 +/-93 msec.
  
  
  CONCLUSIONS
  His refractory periods can be determined consistently in unselected individuals undergoing electrophysiological studies. Measurement of HERP and HFRP may prove useful in assessing the suitability of the His bundle for permanent pacing.
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Lorne J
authors.initials: LJ
authors.lastname: Gula
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Trim
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Krahn
authors.forename: Allan C
authors.initials: AC
authors.lastname: Skanes
authors.forename: Raymond
authors.initials: R
authors.lastname: Yee
authors.forename: George J
authors.initials: GJ
authors.lastname: Klein
mesh_terms: D000328:Adult; D002036:Bundle of His / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D005240:Feasibility Studies; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged
references.citation: J Am Coll Cardiol. 1994 Jul;24(1):225-32
references.pmid: 8006270
references.citation: Pacing Clin Electrophysiol. 1999 Sep;22(9):1372-7
references.pmid: 10527019
references.citation: Circulation. 1985 May;71(5):1010-6
references.pmid: 3986971
references.citation: Lancet. 1997 Oct 25;350(9086):1210-6
references.pmid: 9652562
references.citation: Pacing Clin Electrophysiol. 1999 Dec;22(12):1777-81
references.pmid: 10642131
references.citation: Am Heart J. 1988 Jul;116(1 Pt 1):16-22
references.pmid: 3394616
references.citation: J Am Coll Cardiol. 1997 Mar 15;29(4):744-9
references.pmid: 9091519
references.citation: J Am Coll Cardiol. 2003 Apr 2;41(7):1218-26
references.pmid: 12679225
references.citation: JAMA. 2002 Dec 25;288(24):3115-23
references.pmid: 12495391
references.citation: Circulation. 2000 Aug 15;102(7):736-41
references.pmid: 10942740
references.citation: Circ Res. 1983 Jul;53(1):72-85
references.pmid: 6861298
references.citation: Circulation. 2000 Feb 29;101(8):869-77
references.pmid: 10694526
references.citation: Circulation. 1996 Sep 1;94(5):1027-35
references.pmid: 8790042
references.citation: N Engl J Med. 2002 Jun 13;346(24):1854-62
references.pmid: 12063369
references.citation: Rev Esp Cardiol. 2001 Dec;54(12):1385-93
references.pmid: 11754807
references.citation: Am J Cardiol. 1964 Oct;14:494-503
references.pmid: 14215060
references.citation: J Am Coll Cardiol. 2001 Jul;38(1):167-72
references.pmid: 11451268
references.citation: J Am Coll Cardiol. 1993 Apr;21(5):1124-31
references.pmid: 8459065