title: Electrocardiogram during tachycardia in patients with anterograde conduction over a Mahaim fiber: old criteria revisited.
abstract: OBJECTIVE
  The aim of this study was to prospectively evaluate the sensitivity, specificity, and positive and negative predictive values of previously described ECG criteria to identify preexcited tachycardia due to decrementally conducting accessory pathways (QRS axis between 0 and -75 degrees , QRS width < or = 0.15 seconds, an R wave in lead I, an rS pattern in lead V(1), RS > 1 QRS transition > V(4), and cycle length between 220 and 450 ms).
  
  
  BACKGROUND
  Preexcited tachycardia associated with decrementally conducting right-sided accessory pathways usually shows a rather "narrow" QRS complex and can be difficult to differentiate from supraventricular tachycardia (SVT) with left bundle branch block (LBBB) aberrant conduction.
  
  
  METHODS
  We analyzed three groups of patients: 32 patients with an atriofascicular pathway (group I); 8 patients with long (n = 3) or short (n = 5) decrementally conducting right-sided AV pathway (group II); and a control group that consisted of 35 patients with SVT and LBBB (group III).
  
  
  RESULTS
  Presence of all six criteria had 87.5% sensitivity in group I and a 0% sensitivity in group II. There were four false negatives in group I. The negative predictive value was 82.5%, with six false positives in group III (five patients with an aberrant LBBB-shaped tachycardia with ventriculoatrial conduction over an accessory AV pathway). The criterion cycle length was not helpful.
  
  
  CONCLUSIONS
  Criteria for identifying a tachycardia with anterograde conduction over a Mahaim fiber are helpful only in atriofascicular pathways, with a sensitivity of 87.5% and a negative predictive value of 82.5%. The major cause of false positives was a tachycardia with aberrant LBBB conduction and ventriculoatrial conduction over an accessory AV pathway.
authors.affiliation: Biocor Instituto, Nova Lima, Brazil. eduardosternick@aol.com
authors.forename: Eduardo Back
authors.initials: EB
authors.lastname: Sternick
authors.forename: Fernando E S
authors.initials: FE
authors.lastname: Cruz
authors.forename: Carl
authors.initials: C
authors.lastname: Timmermans
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Sosa
authors.forename: Luz-Maria
authors.initials: LM
authors.lastname: Rodriguez
authors.forename: Luiz M
authors.initials: LM
authors.lastname: Gerken
authors.forename: Márcio L
authors.initials: ML
authors.lastname: Fagundes
authors.forename: Maurício I
authors.initials: MI
authors.lastname: Scanavacca
authors.forename: Hein J J
authors.initials: HJ
authors.lastname: Wellens
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011227:Pre-Excitation, Mahaim-Type / Q000175:diagnosis / Q000503:physiopathology*; D011446:Prospective Studies; D013612:Tachycardia, Ectopic Atrial / Q000175:diagnosis / Q000503:physiopathology*