Can monitoring of intrathoracic impedance reduce morbidity and mortality in patients with chronic heart failure? Rationale and design of the Diagnostic Outcome Trial in Heart Failure (DOT‐HF)☆

Abstract

Background: Chronic heart failure is associated with frequent hospitalisations which are often due to volume-overload decompensation. Monitoring of intrathoracic impedance, measured from an implanted device, can detect increases in pulmonary fluid retention early and facilitate timely treatment interventions. Objective: The DOT-HF trial is designed to investigate if ambulatory monitoring of intrathoracic impedance together with other device-based diagnostic information can reduce morbidity and mortality in patients with chronic heart failure who are treated with cardiac resynchronization therapy (CRT) and/or an implantable defibrillator (ICD).Methods: Approximately 2400 patients will be randomised in a 1:1 fashion to a management strategy with access to the diagnostic information from the implantable device ("access arm"), or a "control arm", where this information is not made available. Study subjects fulfil standard indications for CRT and/or ICD as outlined in current guidelines. In the access arm, a fluid alert algorithm is used to give early warning of decreasing intrathoracic impedance indicating a high risk of an impending volume-overload decompensation. The primary endpoint of DOT-HF is the composite of all-cause mortality or heart failure hospitalisation. Secondary and exploratory endpoints include all-cause mortality, the impact on total health care utilization, quality of life and cost effectiveness. The study is expected to close recruitment during 2010 and to report in 2012.

Intrathoracic Impedance Monitoring, Audible Patient Alerts, and Outcome in Patients With Heart Failure

“…On the basis of the available data and the clinical evaluation, patients were managed according to standardized intervention algorithm. 14 …”

“…Patients in both arms who presented to study centers in the context of a clinical heart failure decompensation and patients in the access arm who had received a fluid alert of their device (see below) were treated according to a standardized intervention algorithm providing detailed recommendations concerning further diagnostic tests and treatment. 14 In patients allocated to the access arm, this included advice for a thorough review of the OptiVol and Cardiac Compass trends. Of note, only changes in intrathoracic impedance with OptiVol could generate an audible alert.…”

“…Although these devices have the capability to monitor diagnostic variables (Cardiac Compass), including intrathoracic impedance (OptiVol), 14 the device-based diagnostic information was available only in patients in the access arm (see below). They were at least 18 years of age, had chronic heart failure (New York Heart Association functional class II-IV) despite optimal medical therapy, and an impaired left ventricular ejection fraction (Յ35%) at the time of implantation.…”

“…14 Further exclusion criteria were a recent (Ͻ40 days) myocardial infarction, a life expectancy of Ͻ1 year, severe pulmonary or renal disease, use of inotropic drug therapy, complex and uncorrected congenital heart disease, and participation in another trial or disease management program in which remote monitoring or implanted technology was used.…”

“…14 On the basis of earlier work, 10 a fluid detection algorithm (OptiVol) was used in the access arm to alert the patient if a certain level of impedance drop occurred and subsequently to assess the patient according to a recommended algorithm. 14 …”