THE INTRACARDIAC ECG: A NEW APPROACH TO THE ASSESSMENT OF ELECTRICAL CARDIAC ACTIVITY BY AN IMPLANTABLE PACING DEVICE
F. Zanon, G. Gasparini, E. Baracca, G. Pastore, A. Corrado, P. China, A. Barbetta, F. Di Gregorio
1. Cardiology Dept., Santa Maria della Misericordia H., Rovigo, Italy; 2. Cardiology Dept., Dell'Angelo H., Mestre-Venezia, Italy; 3. Clinical Research Unit, Medico Spa, Rubano, Italy
Introduction: The intracardiac ECG (iECG) is a multipolar signal derived by the electrode set of a dual-chamber pacemaker. Its main waveform properties were assessed in this study.
Methods: Recordings were performed in 20 patients on implantation, using the Eos DR stimulator (Medico) connected with bipolar atrial and ventricular leads.
Results: The iECG featured all the surface ECG components (iP, iQRS, iT waves). The iQRS morphology was affected by the ventricular activation pattern, allowing prompt discrimination of sinus and ectopic beats. Consistently, the paced iQRS waveform was sensitive to the stimulation site. Surface QRS and iQRS duration were linearly correlated (slope = 0.98, R2 = 0.89, P < 0.001) and the two signals exhibited similar time-course. In the presence of RBBB, the iQRS started at the Q-wave onset, while the standard right ventricular electrogram (VEGM) was delayed (Fig. 1). The long-lasting iQRS signal favoured an appropriate recognition of ventricular activity even in fusion or pseudofusion beats (Fig. 2), preventing false-alarms of capture failure.
Conclusions: The iECG tracing provides valuable information on cardiac activity and is equivalent to a surface ECG lead.
Figure 1. EKG on admission: sinus rhythm. Prolonged P wave (100 ms). First degree atrioventricular block (PQ 230 ms). Right bundle branch block (QRS interval 200 ms). Left anterior fascicular block.
Figure 2. EKG on day 2nd: sinus rhythm. First degree atrioventricular block (PQ 210 ms). Right bundle branch block (pre-existing). AV nodal reentrant tachycardia and stroke
