title: Rate-responsive pacing regulated by cardiac haemodynamics.
abstract: OBJECTIVE
  Trans-valvular impedance (TVI) recording has been proposed for the assessment of cardiac haemodynamics, assuming an inverse relationship between TVI and ventricular volume. We checked whether the TVI sensor can drive the rate-responsive function of a cardiac pacemaker following changes in the inotropic regulation of the heart.
  
  
  METHODS
  An external DDD-R pacemaker (Ext Sophos by Medico, Padova, Italy) equipped with the TVI detecting system was tested in 30 patients on the implantation of conventional pacing leads for dual-chamber pacing. Pacing rate regulation was based on the relationship between the stroke volume and the end-diastolic volume, inferred from TVI data. After sensor calibration in basal conditions, beta-adrenergic stimulation was induced by i.v. administration of 2 microg/ml/min isoprenaline (isoproterenol) (IPN). The actual cardiac rate, the TVI waveform, the end-diastolic and systolic TVI in each cardiac cycle and the TVI-indicated rate were stored in memory as a function of time and down-loaded at the end of the session.
  
  
  RESULTS
  All patients with intrinsic atrial activity (28/30) showed a positive chronotropic response to IPN, coupled with a significant increase in end-diastolic TVI and a four-times larger increase in end-systolic TVI. The TVI inotropic index mirrored the sinus rate time-course, with a linear correlation between the two parameters (r(2)>0.7 in 25/28 cases). As a result, the TVI-indicated rate closely reproduced the sinus rate.
  
  
  CONCLUSIONS
  The study confirms the reliability of the haemodynamic information derived from TVI and supports its application in the regulation of rate-responsive pacing.
authors.affiliation: Unità Operativa di Cardiologia, Ospedale Umberto I, via Circonvallazione, 50, 30174 Mestre, Venezia, Italy. g_gasparini2000@yahoo.it
authors.forename: Gianni
authors.initials: G
authors.lastname: Gasparini
authors.forename: Antonio
authors.initials: A
authors.lastname: Curnis
authors.forename: Michele
authors.initials: M
authors.lastname: Gulizia
authors.forename: Eraldo
authors.initials: E
authors.lastname: Occhetta
authors.forename: Andrea
authors.initials: A
authors.lastname: Corrado
authors.forename: Luca
authors.initials: L
authors.lastname: Bontempi
authors.forename: Giosuè
authors.initials: G
authors.lastname: Mascioli
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Maura Francese
authors.forename: Miriam
authors.initials: M
authors.lastname: Bortnik
authors.forename: Andrea
authors.initials: A
authors.lastname: Magnani
authors.forename: Franco
authors.initials: F
authors.lastname: Di Gregorio
authors.forename: Alberto
authors.initials: A
authors.lastname: Barbetta
authors.forename: Antonio
authors.initials: A
authors.lastname: Raviele
mesh_terms: D002304:Cardiac Pacing, Artificial; D002307:Cardiography, Impedance; D002316:Cardiotonic Agents / Q000494:pharmacology; D006439:Hemodynamics; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D016014:Linear Models; D009200:Myocardial Contraction; D013318:Stroke Volume
chemical_list: D002316:Cardiotonic Agents; D007545:Isoproterenol