Can transventricular intracardiac impedance measurement discriminate haemodynamically unstable ventricular arrhythmias in human?

Aims To measure changes in transventricular impedance during arrhythmias. Methods and results Patients were studied during electrophysiotogical studies. A quadrapolar catheter was positioned at the right ventricular apex (RVA) and a decapotar catheter within the coronary sinus (CS). Transventricutar impedance was measured by injecting a subthreshold biphasic rectangular pulse of 600 LA 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 ventricutar 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. Transventricutar impedance felt significantly during unstable arrhythmias and may be useful as a sensor capable of haemodynamic discrimination.