OptiLink HF: Remote Intrathoracic Impedance Monitoring Doesn't Improve Survival

Marlene Busko

September 03, 2015

LONDON, UK — Patients with heart failure who had a device that alerted physicians when it detected that fluid in the chest was above a certain threshold did not have fewer CV hospitalizations or improved survival during a mean follow-up of 23 months compared with other patients who received standard care, in a new study[x].

"This telemedicine approach was not superior to regular clinical practice to avoid death or cardiovascular hospitalization," Dr Michael Böhm (Universitätskliniken des Saarlandes, Homburg/Saar, Germany) summarized, presenting these findings from the Optimization of Heart Failure Management using OptiVol Fluid Status Monitoring and CareLink (OptiLink HF) study in a press briefing prior to a hot-line session at the European Society of Cardiology (ESC) 2015 Congress.

Dr Michael Böhm

In 24% of cases, the alerts were not transferred to the physician because the patients were offline—in the hospital, on vacation, or not plugged in, Böhm told heartwire from Medscape. On the other hand, in 15% of cases when the alert was transmitted to the physician, the physician did not take any action (such as giving advice or arranging an office or hospital visit). "So we have to work on this," he said.

"One of the messages of this study is that telemonitoring depends on multiple factors, and the effectiveness of successful transmission of the signal depends on adherence of patients and physicians," he said. "I talked to some physicians, and they are used to treating signs and symptoms, such as swollen ankles and shortness of breath. When the patients said they didn't have this, many said 'Okay, everything is fine.' "

Dr Karl Swedberg

Similarly, the assigned discussant at the hot-line session, Dr Karl Swedberg (University of Gothenberg, Sweden), stressed the importance of looking for symptoms when designing future trials of telemedicine-guided interventions in heart failure. He suggested that this trial was neutral partly because, "importantly, the end point was wrong," since it was based on impedance numbers. In future trials, "composite clinical end points should be explored where functional status and symptoms are included, in order to allow important treatment effects to be evaluated properly."

Telemedicine Guided, Inaudible Alerts for Fluid Retention

"In decompensated heart failure, fluid overload in the lungs occurs hours, days, and potentially weeks before signs and symptoms of heart failure develop," Böhm said.

This study aimed to determine whether early detection of fluid retention—using a system that transmits an inaudible alert to the physician when the patient's pulmonary fluid rises above a "fluid threshold crossing"—would reduce mortality and cardiovascular hospitalization in patients with chronic HF.

From 2008 to 2012, the researchers enrolled 1002 patients who had new or replacement Medtronic implantable cardiac defibrillators (ICDs) or cardiac resynchronization therapy defibrillators (CRT-Ds) that could also monitor impedance (fluid accumulation in the chest) in 37 centers in Germany[2]. The patients all had NYHA class 2 or 3 chronic HF and a left ventricular ejection fraction (LVEF) ≤35%, in accordance with SCD-HeFT and ESC guidelines in 2008 for implanting these devices.

The patients also had to be at high risk of cardiac decompensation—that is, they had been hospitalized for HF within the past 12 months or they had had an increase in diuretic treatment, BNP, or NT-pro BNP within the past 30 days. Patients with renal failure, chronic obstructive pulmonary disease, or other factors that affect impedance were excluded.

After they received their ICDs or CRT-Ds, patients were randomized to have the chest-fluid–monitoring capability switched "on" (in 505 patients) or "off" (497 patients).

The patients had a mean age of 66; 80% were male, and they had similar baseline characteristics. During follow-up, 59 patients in the intervention arm and 63 patients in the control arm died.

There were 1748 "fluid threshold crossings" that occurred in 80% of the 505 patients in the intervention group. However, the alerts were transmitted to the physicians in only 1324 (76%) cases.

In only 37% of the times when a physician contacted a patient about an alert, the patients reported having worsening HF symptoms. Physicians changed the patient's medication in only 47% of the times they had received alerts.

There was no significant between-group difference in the primary composite end point or its components.

Primary End Point, Intervention Arm vs Controls

End point Intervention (n=505), n (%) Control (n=497), n (%) HR (95%CI) P
Composite end point* 227 (45.0) 239 (48.1) 0.87 (0.72– 1.04) 0.13
All-cause death 59 (6.2) 63 (8.5) 0.89 (0.62–1.282 0.52
CV hospitalization 214 (42.4) 221(44.5) 0.89 (0.73–1.08) 0.22
*Composite end point=all-cause death or CV hospitalization

These outcomes were also not significantly different across subgroups (age <65 vs >65; gender; ischemic vs nonischemic CVD; NYHA class 2 vs 3; history or no history of AF; and CRT-D vs ICD).

This study is telling physicians only that something is wrong, and it's very hard to help these patients since they already have a device and optimal medical therapy, ESC spokesperson Dr Lars Køber (Copenhagen University Hospital of Rigshospitalet, Denmark) told heartwire . The study raises two important questions to be addressed in future research, he said. First, "Is the signal [(alert)] important?" Second, "What should the [patient-management] algorithm be for how physicians should react?"

The study was funded by Medtronic Bakken Research Center. Böhm and coauthors received grant support from Medtronic.

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