No additional reduction of mortality or heart failure events with intrathoracic impedance measurements in a context of telemonitoring with structural biofeedback

Abstract

Our aim was to test if intra-thoracic impedance (ITI) measurements would improve short-term clinical outcome (i.e. all-cause mortality and heart failure hospitalizations) in patients with cardiac resynchronization therapy (CRT) who were followed in a telemonitoring program with structural biofeedback. Methods: CRT patients (n=200; age= 70 +/-14y) were included in a telemonitoring program at Ziekenhuis Oost-Limburg Genk, which comprised daily transmissions through a wireless system installed at their homes. All patients were followed for potential lead/device problems, episodes of anti-tachycardia pacing, device shocks, occurrence of arrhytmias, a decline in biventricular pacing percentage and/or a sudden drop in physical activity. Patients with missed transmissions were contacted by phone. Devices with ITI measurement ability were implanted in 108 patients. Those provided extra alerts when pre-specified ITI tresholds were crossed during at least 7 days. Heart failure nurses checked all telemonitoring alerts at daily time intervals. For clinically relevant alerts, as defined by protocol, direct biofeedback was provided to the patient by means of a structured questionnaire. Dependent on the outcome of the questionnaire, emphasis was placed on heart failure education with or without the advice of one of the following actions:(1) doubling of the dose of diuretics during 3 days after which the patient was contacted again;(2) contacting the general practitioner of the patient;(3) planning a visit at the multidisciplinary CRT clinic of Ziekenhuis Oost-Limburg. Heart-failure hospitalization and mortality data were collected for all patients by searching the electronic health records of the hospital. Results: During 250 patient-years of follow-up, there were 401 clinically relevant telemonitoring alerts. Forty-eight percent of these (n=194) were because of ITI treshold crossings. Those alerts led to an intervention in 43% of the cases. Mean follow-up was 13 +/-16 months, during which 22 patients (11%) died, 23 (12%) were admitted for heart failure, while 159 (79%) had an event-free survival. Time to death (P=0.211) and time to first heart failure admission (P=0.679) were similar between patients with and without ITI measurements. Annualizd mortality was 8% versus 10% respectively, which was also comparable among groups (P=0.206). Conclusion: In the setting of a structured heart failure follow-up clinic, ITI measurements in the context of an intensive telemonitoring program with structural biofeedback for CRT patients, did not result in an additional reduction of all-cause mortality and/or heart failure hospitalizations.