title: The effect of conduction velocity slowing in left ventricular midwall on the QRS complex morphology: A simulation study.
abstract: Midwall fibrosis is a frequent finding in different types of left ventricular hypertrophy. Fibrosis presents a local conduction block that can create a substrate for ventricular arrhythmias and lead to the continuous generation of reentry. Having also impact on the sequence of ventricular activation it can modify the shape of QRS complex. In this study we simulated the effects of slowed conduction velocity in the midwall in the left ventricle and in its anteroseptal region on the QRS morphology using a computer model.
  
  
  METHODS
  The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids; the left ventricular wall is represented by five layers. The impulse propagation velocity was decreased by 50% in one and two midwall layers, respectively, in the whole left ventricle and in LV anterior region. The effects of slowed conduction velocity on the QRS complex of the 12-lead electrocardiogram are presented as 12-lead electrocardiograms and corresponding values of ECG criteria for left ventricular hypertrophy (ECG-LVH criteria): Gubner criterion, Sokolow-Lyon index (SLI) and Cornell voltage.
  
  
  RESULTS
  All simulated situations led to increased R wave amplitude in the lead I and of S wave in the lead III, showing a leftward shift of the electrical axis and increased values of ECG-LVH criteria based on limb leads alone or in combination with precordial leads (Gubner criterion, Cornell voltage). The slowed conduction velocity in the whole LV influenced the QRS complex voltage in precordial leads, having an impact on the SLI and Cornell voltage. The changes were pronounced if two layers were involved.
  
  
  CONCLUSIONS
  Using computer modeling we showed that the midwall slowing in conduction velocity modified the QRS complex morphology. The QRS complex changes were consistent with ECG-LVH criteria, i.e. QRS patterns usually interpreted as the effect of left ventricular hypertrophy (the increased left ventricular mass).
authors.affiliation: International Laser Center, Bratislava, Slovakia; Institute of Pathological Physiology, Medical Faculty, Comenius University, Bratislava, Slovakia. Electronic address: bacharova@ilc.sk.
authors.forename: Ljuba
authors.initials: L
authors.lastname: Bacharova
authors.affiliation: Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava, Slovak Republic.
authors.forename: Vavrinec
authors.initials: V
authors.lastname: Szathmary
authors.affiliation: Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovak Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Svehlikova
authors.affiliation: International Laser Center, Bratislava, Slovakia.
authors.forename: Anton
authors.initials: A
authors.lastname: Mateasik
authors.affiliation: Institute of Pathological Physiology, Medical Faculty, Comenius University, Bratislava, Slovakia.
authors.forename: Julia
authors.initials: J
authors.lastname: Gyhagen
authors.affiliation: Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovak Republic.
authors.forename: Milan
authors.initials: M
authors.lastname: Tysler
mesh_terms: D003198:Computer Simulation; D004562:Electrocardiography / Q000379:methods*; D056966:Excitation Contraction Coupling / Q000502:physiology*; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D009431:Neural Conduction / Q000502:physiology*; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: Conduction velocity; Left ventricular hypertrophy; Midwall; QRS complex