© 2005 The European Society of Cardiology. Published by Elsevier Ltd. All rights reserved.
Rate-responsive pacing regulated by cardiac haemodynamics
aUnitą Operativa di Cardiologia, Ospedale Umberto I via Circonvallazione, 50, 30174 Mestre, Venezia, Italy; bUnitą Operativa di Cardiologia, Spedali Civili, P.le Ospedali Civili, 1 25100 Brescia, Italy; cUnitą Operativa di Cardiologia, Ospedale S. Luigi - S. Currņ, via Fleming, 24 95100 Catania, Italy; dUnitą Operativa di Cardiologia, Ospedale Maggiore della Caritą, Corso Mazzini, 18 28100 Novara, Italy; eUnitą di Ricerca Clinica, Medico SpA, via Pitagora, 15 35030 Rubano, Padova, Italy
AIMS: 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 Sophņs 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 µg/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 (r2 > 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.
Key Words: rate-responsive pacing, haemodynamic sensors, trans-valvular impedance
*Corresponding author. Tel.: +39 041 2607201; fax: +39 041 2607235. E-mail: addresses: g_gasparini2000{at}yahoo.it (G. Gasparini), antonio.curnis{at}libero.it (A. Curnis), michele.gulizia{at}tin.it (M. Gulizia), occhetta{at}r-j.it (E. Occhetta), digregorio{at}medicoweb.com (F. Di Gregorio).