The potential of electrocardiographic markers to tune cardiac device therapy

Abstract

In this thesis an effort was made to translate basic research into clinical practice to improve cardiac device therapy. We showed the electrocardiogram (ECG) is everything but obsolete or outdated and is of great value as a simple non-invasive tool in identifying individuals that can benefit from implantable cardioverter-defibrillator (ICD) and/or cardiac resynchronization therapy (CRT) implantation. Furthermore, in-device monitoring via the electrogram (EGM) can further tune cardiac device therapy. Heart failure is a prevalent and severe disease in which progressive decrease of pump function of the heart occurs. The lifetime risk for developing heart failure has been reported to range from 20-33%. It renders a poor prognosis; only half of the patients are still alive 5 years after first symptoms occur. Although cardiac implantable electronic devices have caused improvement not only in survival but also in quality of life in patients with heart failure, we have to remain critical towards the evidence. Effort should be made to improve risk stratification to identify those patients that do benefit. This way, guidelines could provide more patient-tailored recommendations. In this thesis, we show that the ECG is an easily applicable and non-invasive tool that can be used for this purpose. In animal studies as well as the large European multicenter clinical trial EUTrigTreat we show that beat-to-beat variability of repolarization is a promising parameter that can be used to improve risk stratification for ventricular arrhythmias and therefore the benefit of ICDs. In the national multicenter Markers and Response to CRT (MARC) study we show that the vectorcardiogram derived from the ECG gives a more objective and accurate impression of the electrical substrate favorable to CRT response. Furthermore, technological advancements will enable 24/7 in-device monitoring of these electrocardiographic markers to further tune cardiac device therapy such as the monitoring of beat-to-beat variations of repolarization derived from the right ventricular electrogram to initiate temporary accelerated pacing and prevent ventricular arrhythmias.