Impact of continuous intracardiac ST-segment monitoring on mid-term outcomes of ICD-implanted patients with coronary artery disease. Early results of a prospective comparison with conventional ICD outcomes.

BACKGROUND: Although myocardial ischaemia monitored by some implantable cardioverter-defibrillators (ICDs) might improve patient care, the clinical usefulness of this technology has not yet been validated. OBJECTIVE: To investigate the potential impact of ICD-based ischaemia monitoring on clinical care and patient management of ICD recipients. DESIGN: Prospective, controlled, non-randomised study. SETTING: Single-centre, university hospital. PATIENTS: Consecutive patients with known coronary artery disease, followed up for at least 6 months. INTERVENTIONS: Patients implanted with either an ICD providing continuous intracardiac ST monitoring (n=53; ST group) or with an ICD without this capability (n=50). MAIN OUTCOME MEASURES: Major cardiovascular events, appropriateness of ST-shift episodes and unscheduled device-related visits. RESULTS: During follow-up (15.4±8.4 months), one patient experienced ST-shift events confirmed by angiography to be related to myocardial ischaemia. Myocardial infarction was a rare event and occurred in one patient (ST group) who had an ST-elevation myocardial infarction 3 weeks after the implant, but at this time the algorithm had not yet been activated. In the ST group, seven patients had one or more episodes of false-positive ST events (median 9, range 1-90). The programmable features of the device helped overcome the problem in six patients. Among patients with a remote monitoring system, unscheduled outpatient visits were significantly increased in the ST group (17 vs 4; p=0.032). CONCLUSIONS: Although, this study was underpowered by the small number of acute ischaemic events, ICD-based ST monitoring failed to provide a benefit over ICDs without this capability and increased unscheduled evaluations in patients with remote follow-up. The sensitivity and specificity of the algorithm still require validation.