CHICAGO – Regular assessment of a heart failure patient’s lung fluid volume using a device that measures electrical conduction through the chest – lung impedance – helped guide clinicians to make timely adjustments in a patient’s medications and thereby significantly reduce mortality and hospitalizations during an average 4 years of follow-up in a randomized, controlled study with 256 patients.
Monthly measurement of lung impedance and medication adjustments based on the information led to a 58% reduction in hospitalizations for acute heart failure during the first year of the study, compared with control patients, and a 56% reduction in heart failure hospitalizations, compared with controls, during the entire course of the study, the study’s two primary endpoints, Dr. Michael K. Shochat reported at the annual meeting of the American College of Cardiology.
The results also showed that performing regular lung impedance measurements and using the results to guide treatment led to a 43% reduction in all-cause mortality and a 62% drop in heart failure mortality during the average 4-year course of the study, said Dr. Shochat, a cardiologist at the Heart Institute of Hillel Yaffe Medical Center in Hadera, Israel. Concurrent with Dr. Shochat’s report at the meeting the results also appeared in an article published online (J Card Failure. 2016;doi:10.1016/j.cardfail.2016.03.015).
A key aspect of the study was that the clinicians who treated the enrolled patients who underwent lung impedance monitoring used this information to adjust medications the patients received. Overall, patients who underwent monitoring had more than twice the number of medication dose adjustments, compared with the control patients. These adjustments particularly focused on diuretic dosages, which changed three times as often in the monitored patients, compared with controls, Dr. Shochat reported. Changes in the dosages of beta-blockers and ACE inhibitors also showed marked increases in the monitored patients, compared with the controls.
The Non-Invasive Lung IMPEDANCE-Guided Preemptive Treatment in Chronic Heart Failure Patients (IMPEDANCE-HF) trial enrolled 256 patients at two centers in Israel during 2005-2014. Patients had New York Heart Association class II-IV heart failure and a left ventricular ejection fraction of 35% or less. The enrolled patients averaged 67 years of age, and 80% were men.
Clinicians measured lung impedance using a proprietary device that places external electrodes on opposite sides of the patient’s chest. Calculation of impedance used a formula that eliminated the noise from chest wall impedance and focused exclusively on lung impedance. Once the electrodes are placed collection of the impedance data takes about 1 minute, Dr. Shochat said. The study protocol called for impedance data to be collected monthly, and in practice it occurred about 11 times a year during the study.
The investigators calculated for each patient in the active arm of the study a “basal” lung impedance level that reflected their level of lung conductivity when their lungs were clear of excess fluid. Participating clinicians were instructed to intervene by altering medications when the impedance level dropped more than 18% below the basal level. Their goal was to prevent impedance from dropping to more than 24% below the basal level, which correlated with when heart failure patients usually required hospitalization for acute decompensation. The specifics of how to adjust medications to manage patients who showed these signs of fluid overload were left to the discretion of each attending physician.
MPEDANCE-HF was sponsored by the RSMM Company, which is developing the lung impedance measurement device used in the study. Dr. Shochat is a cofounder of RSMM and is a member of the company’s board of directors.
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