ELECTROPHYSIOLOGY
Can transventricular intracardiac impedance measurement discriminate haemodynamically unstable ventricular arrhythmias in human?
1 Department of Cardiology, Castle Hill Hospital, East Yorkshire, UK; 2 Biotronik UK; 3 Biotronik GmbH & Co KG, Erlangen, Germany
Aims To measure changes in transventricular impedance during arrhythmias.
Methods and results Patients were studied during electrophysiological studies. A quadrapolar catheter was positioned at the right ventricular apex (RVA) and a decapolar catheter within the coronary sinus (CS). Transventricular impedance was measured by injecting a subthreshold biphasic rectangular pulse of 600 µ A between poles 1 of the CS catheter and pole 1 of the RVA catheter and the voltage measured between CS pole 10 and RVA catheter pole 4. Stroke impedance (SZ), surface ECG, intracardiac electrogram (IEGM), and invasive femoral artery blood pressure (FAP) were recorded. Twenty-eight patients were analysed, 5 with inducible, haemodynamically unstable ventricular tachycardia (VT) (HUSVT), 5 with stable VT (HSVT). During HUSVT, the SZ value reduced to 22% (range 0.15–0.32 P < 0.001) in comparison with sinus rhythm. For HSVT, the SZ value reduced to 58% (range 0.33–0.88) P < 0.01, significantly different from HUSVT (P < 0.01). There was a good correlation between reduction of SZ and arterial pulse pressure (PP) during arrhythmias (r = 0.95).
Conclusion Changes in SZ strongly correlated with PP amplitude. Transventricular impedance fell significantly during unstable arrhythmias and may be useful as a sensor capable of haemodynamic discrimination.
Key Words: Transventricular intracardiac impedance, Ventricular tachycardia, Haemodynamic stability
* Corresponding author: Princess Alexandra Hospital, Ipswich Road, Woolloongabba, Brisbane, QLD 4012, Australia. Tel: +00617 32402537; fax: +00617 32407630. E-mail address: gerald_kaye{at}health.qld.gov.au