Patients with heart failure are at a high risk of
Patients with heart failure are at a high risk of mortality and morbidity. Medical expenses associated with heart failure are increasing, and approaches aimed at early heart failure detection and reduction of the hospitalization rate are yet to be developed. Patients with CIEDs also develop heart failure, and it has been expected that utilization of RM will help effectively manage this problem. One of the applications of the RM technology is monitoring of weight and blood pressure. As shown in Fig. 3, the Boston Scientific׳s LATITUDE device is capable of such monitoring on a daily basis using a wireless weight scale and a manometer. Intrathoracic impedance monitoring is also available in RM systems from several manufacturers. Yu et al.  showed that intrathoracic impedance, measured between the right ventricular lead and the CIED case, inversely correlates with pulmonary capillary wedge pressure and net fluid overload. Some other studies also reported on the usefulness of this parameter [7–9]. In this regard, the CIED made by Medtronic supplies the OptiVol index, which is calculated according to the accumulated difference between the daily and reference impedance. CareLink, the corresponding RM system, can send an alert when this index exceeds a preset value. Although the OptiVol index has limitations in sensitivity and specificity, it can be used as a parameter to detect worsening of heart failure . As an example, Fig. 4 shows a shift in the OptiVol index of a patient with heart failure, which correlates with the shift in the level of blood rosmarinic acid natriuretic peptide and the patient׳s symptoms. The first of the 3 OptiVol index peaks was associated with an elevation of the brain natriuretic peptide level and a symptom of dyspnea on effort. Additional prescription of a diuretic prevented further worsening of dyspnea on effort, and the OptiVol index decreased. As shown in Fig. 5, St. Jude Medical׳s Merlin.net and Biotronik׳s Home Monitoring also monitor intrathoracic impedance. Studies are ongoing to find a more informative index that, in combination with intrathoracic impedance and other parameters, will allow detecting heart failure with better sensitivity and specificity.
Acceptance and safety A number of papers confirmed the safety, feasibility, and cost-effectiveness of the RM technology [11–14]. Lazarus reported that, according to the AWARE trial , the broad application of a monitoring system strongly supported its capability to improve the care of cardiac device recipients, enhance their safety, and optimize the allocation of health resources. Specifically, 3,003,763 transmissions from 11,624 recipients of PPMs, ICDs, and CRT-Ds worldwide were analyzed. The vast majority (86%) of events were disease-related. The mean interval between the last follow-up and the occurrence of events notified by the RM system was 26 days, which represents a putative temporal gain of 154 and 64 days in patients usually followed at 6- and 3-month intervals, respectively. The appropriate follow-up interval for patients with RM systems is an important parameter that directly affects the burden on the device clinic. The REFORM trial described by Hindricks et al.  studied 155 ICD recipients with MADIT II indications who were randomly assigned either 3- or 12-month follow-up intervals in the period between 3 and 27 months after implantation. The authors compared the burden of scheduled and unscheduled ICD follow-up visits, quality of life (using the SF-36), and clinical outcomes. Compared with the 3-month follow-up interval, the 12-month interval resulted in only a minor increase in the number of unscheduled follow-ups (0.64 vs. 0.27 per patient-year; P=0.03). Furthermore, no significant differences were found in mortality, hospitalization rate, and hospitalization length during the 2-year observation period, although more patients were lost to follow-up in the 12-month group (10 vs. 3; P=0.04). The SF-36 scores favored the 12-month interval in the “social functioning” and “mental health” domains. Thus, it appears that the extension of the 3-month in-office follow-up interval to 12 months under automatic daily RM reduced the ICD follow-up burden during 27 months after implantation without compromising the patients׳ safety.