HFSA: Fluid status should be added to monitoring regimen of HF patients
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| ICD/CRT-D data is transmitted through home monitor to physician's office. Image Source: Medtronic |
William T. Abraham, MD, director of cardiovascular medicine at Ohio State University Medical Center in Columbus, who presented the trial, noted that worsening heart failure resulting in hospitalizations, emergency department visits and unscheduled office visits remains a “clinical and economic challenge.”
The ACC/AHA Performance Measures and the Centers for Medicare & Medicaid Services Measures currently recommend self-monitoring of daily weights for assessing the clinical status of ambulatory heart failure patients. In fact, this “gold-standard” is a Class I recommendation in the 2009 ACC/AHA Heart Guidelines, and also is included in the HFSA Guidelines, issued in 2006.
However, Abraham pointed out that new diagnostic tools, such as fluid status monitoring via implantable devices, may offer additional tools for remote or outpatient and in-clinic patient monitoring.
Also, he noted that there are limitations to daily weight monitoring. “Most studies demonstrate low sensitivity of daily weight monitoring in predicting episodes of worsening heart failure,” Abraham said.
Even the 2009 ACC/AHA guidelines acknowledged its limitation: “Changes in body weight may be less reliable during long periods of follow-up, because many patients may gain non-fluid weight and others may lose skeletal muscle mass and body fat as heart failure progresses due to the development of cardiac cachexia.”
FAST (Fluid Accumulation Status Trial) was designed to prospectively compare the relative sensitivity and unexplained detection rate of changes in daily weights versus intrathoracic impedance changes (with Medtronic’s OptiVol Fluid Status Monitoring) in a group of currently or previously symptomatic heart failure patients.
Researchers downloaded impedance software into existing CRT-D and ICD devices: InSync Marquis (models 7274, 7279, 7289) and Marquis (model 7277), both of which are manufactured and distributed by the Minneapolis-based Medtronic.
They measured daily impedance values stored by the device and retrieved at scheduled follow-up (one month, three months and six months post-download and every six months thereafter until study closure) via telemetry. Also, each patient received a diary and instructions to record daily weights using personal in-home scales.
All patients enrolled had an ejection fraction of less than 35 percent, and had an implant for at least 30 days.
Of the 156 subjects enrolled in 18 centers with a median of 537 days of follow-up, Abraham reported that there were 417 incidents of fluid index threshold crossings in 116 subjects (2.08/subject/year), and 890 incidents of weight changes of three pounds in one day or five pounds in three days in 94 patients (4.43/subject/year).
Overall, there were 65 adjudicated heart failure events in 31 subjects (0.32 events/subject/year), with 48 detected by fluid index threshold crossing and 13 detected by weight change.
Abraham noted that of the 65 adjudicated heart failure events, 62 percent were detected by intrathoracic impedance monitoring, but not by daily weight monitoring; and conversely, 8 percent were detected by weight but not by intrathoracic impedance monitoring. Also, fluid monitoring had an unexplained detection rate of 1.9 events per patient per year as compared with 4.3 events per patient per year with weight monitoring.
Based on their findings, Abraham concluded that patient compliance to daily weight monitoring is poor (less 76 percent), “even in the setting of a clinical trial.” Also, he said that fluid monitoring is a more accurate predictor of worsening heart failure compared to daily weight monitoring, as the adjusted sensitivity was more than three times higher for fluid index and the adjusted unexplained detection rate more than two times higher for daily weights.
Lynne W. Stevenson, MD, from Brigham and Women's Hospital in Boston, in her invited commentary, noted that the well-designed trial is tackling the important problem of managing heart failure patients in their homes, adding that the vast majority of changes made to the therapy in this patient population is typically based on variations in home weight.
Stevenson noted that FAST used a higher-than-typical threshold of three pounds in a day, as opposed to the traditional two pounds in a day.
"What is the right measurement?” Stevenson questioned. “In [FAST], intrathoracic impedance detected 74 percent of events, but it also detected 369 other events. [Establishing] gold standards of physiologic changes are very difficult to interpret in patients because spontaneous changes, which are not followed by [adverse] events also occur.”
Stevenson also expressed concern about too many excess alerts from “nonevents” having the potential to blunt the system of response. “It might be difficult to know when to intervene,” she said.
Weight fluctuations, according to Stevenson, “are not the right signal for chronic outpatient surveillance, [but] it's not time to throw them away yet. They clearly have helped us. Perhaps we have to be more concerned, however, that the patient who feels bad with a stable weight may yet be deteriorating, and in a patient whose diuretics are not decreasing a weight gain may in fact signal gained fat and not fluid."
“Unfortunately, one out of every three Medicare dollars is going to treat patients with heart failure, so we don’t have much time to get it right,” she concluded.
Minneapolis-based Medtronic provided funding for the FAST trial.