title: Non invasive hemodynamic monitorization for AV interval optimization in patients with ventricular resynchronization therapy.
abstract: OBJECTIVE
  In patients (pts) with dilated cardiomyopathy and intraventricular conduction disturbances, resynchronization therapy improves cardiac function and functional capacity. Determination of the optimal AV interval is essential to optimize the therapy results and various methods have been used in daily practice to obtain such an interval. The aim of this work is to assess optimal AV determined by impedance cardiography and compare it to the interval previously obtained by transmitral flow Doppler echocardiography.
  
  
  METHODS
  Seven pts were evaluated, five men, mean age of 61 +/- 10 years, with dilated cardiomyopathy, intra-ventricular conduction disturbances and heart failure, New York Heart Association functional class III or IV. Four pts had ischemic cardiomyopathy and three idiopathic. All pts had an implanted cardioverter-defibrillator with cardiac resynchronization.
  
  
  METHODS
  The optimal AV delay was estimated by transmitral flow pulsed Doppler using the method previously described by Ritter. Subsequently, cardiac output (CO) was determined by impedance cardiography. CO was estimated for different AV delays, beginning with 80 ms until occurrence of fusion QRS. The optimal AV delay was defined as the value corresponding to the highest measured CO. The ideal AV interval was compared between the two methods used.
  
  
  RESULTS
  The AV delay determined by echocardiography varied between 120 and 170 ms (134 +/- 17 ms). The optimum AV delay based on CO estimation varied between 110 and 190 ms (137 +/- 26 ms). There was a correlation between the delays determined by the two methods (r = 0.844; p = 0.017).
  
  
  CONCLUSIONS
  In pts undergoing ventricular resynchronization therapy, AV delay optimization based on CO determined by impedance cardiography is comparable to that measured by transmitral flow pulsed Doppler. However, impedance cardiography seems a more objective and simpler technique.
authors.affiliation: Serviço de Cardiologia do Hospital São Bernardo, Setúbal. jferreirasantos@netvisão.pt
authors.forename: José Ferreira
authors.initials: JF
authors.lastname: Santos
authors.forename: Leonor
authors.initials: L
authors.lastname: Parreira
authors.forename: João
authors.initials: J
authors.lastname: Madeira
authors.forename: Nuno
authors.initials: N
authors.lastname: Fonseca
authors.forename: Luís Neves
authors.initials: LN
authors.lastname: Soares
authors.forename: Lopes
authors.initials: L
authors.lastname: Inês
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000150:complications; D002307:Cardiography, Impedance; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015150:Echocardiography, Doppler; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D018754:Ventricular Dysfunction / Q000150:complications