13th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 1998

January 24-31, 1998
Marilleva, Trento, Italy

S-9

Management of detection problems using advanced sensing programming

Leandro Chiodi, Antonio Fazi, Michele Maltese*, Stefano Zanoni*, Rossano Vergassola.
Dipartimento di Cardiologia, Osp. S.M. Annunziata, Florence, * Seda S.p.A., Trezzano s/N (MI), Italy

Introduction

The implantable cardioverter defibrillator (ICD) has proven to be useful in preventing sudden cardiac death and it is currently used in treating patients with malignant ventricular arrhythmias^1-3.

All new generation devices include particular algorithms capable to detect and treat ventricular tachycardias (VT) and ventricular fibrillation (VF). The critical point, concerning the efficacy of such electric therapy, is represented by the correct sensing of ventricular events. In all devices sensing-detection failures may become manifest as: fault or delay in detecting VT or VF (undersensing); false detection of VT/VF (oversensing) with delivery of inappropriate therapy (eg, ATP instead of shock or vice-versa); errors in bradycardia detection (eg, inappropriate pacing or failure of pacing).

There are several reports of sensing-detection anomalies⁴ in the literature, including under- and over-sensing, resulting in inappropriate therapies or delay in delivering shock.

Such problems^5,6 could cause physical and psychological discomfort to the patient and may adversely affect some potentially life-threatening arrhythmias. Failure in detecting ventricular arrhythmias may result, in the worst case, in the death of the patient.

Sensing and detection failures are not the sole causes of inappropriate shock delivery. Other causes could be related to electromagnetic interferences (by external fields), or to the sensing lead (fracture, dislodgement, fibrosis).

The new generation of ICDs offers a long-term intra-cardiac electrogram memory with cycle length data and markers that are useful in supporting the analysis of sensed events. This improvement allows the physician to evaluate both incidence and cause of inappropriate delivery of the therapy. In Biotronik Phylax ICDs some pre-settled Automatic Sensing Adjustment programs are included and there is also the possibility to modify most of the parameters of the Sensing Input Stage. By changing the input stage program, the physician has the possibility to solve some of those problems.