All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor ----------------------------------------------------------- NOTE: You can make the print bigger with the font button on your browser! (It's usually a big "A") ----------------------------------------------------------- BioZ-type Monitoring Update June 8, 2006 - As noted in past mailings, there is a non- invasive way to estimate heart function and risk for coming heart failure episodes. It is called bio-impedance and its main manufacturer is Cardiodynamics, called BioZ. A CHFer is connected by leads (like EKG sticky leads) to a device that sends an alternating current across the chest to measure fluid-related electrical resistance, called impedance. Based on how the readings change over time, some heart function measures can be measured and others estimated. Researchers' early report on the PREDICT trial is in the June 6, 2006 issue of the Journal of the American College of Cardiology. The information gained using this method is not as accurate as cath but is non-invasive. It is meant to be used in addition to exams and other test results, not as a stand-alone, sure-fire way to measure heart function. In another trial named PREVENT, researchers did bio- impedance monitoring outpatient every two weeks for 26 weeks in 212 patients with chronic HF. They were mostly in class 2 or class 3, with either ischemic or non-ischemic CHF, and EF averaged 27%. During the trial, patients were managed by the judgment of their usual doctors, who did not know the bio- impedance results. Of 2,316 office visits, 77 (3.3%) resulted in an acute event within two weeks. The events, which happened within an average of 6 days after testing, were the study's primary end point, including death or a hospitalization or emergency department visit for worsening HF that led to increased therapy. Independent predictors of decompensation included functional heart class, heart rate, systolic blood pressure, and a patient's own ideas of how he was doing! Three things that bio-impedance measures were also independent predictors of decompensation - midsection fluid content, hemodynamic velocity index, and LV ejection time. Please note that these measurements are directly taken, not estimated from the test's results. The PREVENT researchers said something else interesting - that these measurements taken at study start did NOT predict who would get worse. It may be the TREND that is most valuable for predicting who will or will not get worse over time. ====================================== Some ICDs can also detect changes in electrical signals in the midsection (intrathoracic impedance). These are the changes described above that may signal fluid collecting in the lungs. A recent small study suggests that an ICD's warning of this - although not always accurate - could be used to reduce hospital admissions for heart failure. This info was presented at this year's Heart Rhythm Society 2006 Scientific Sessions. Researchers studied 54 consecutive patients with newly implanted BiV pacer/ICDs every 3 months for about a year. A control group got a device without the extra capability. The other half of the patients got a Medtronic InSync Sentry device with thoracic-impedance-monitoring ability. The two patient groups were alike in most ways, including age, EF, QRS length on EKG, ischemic vs non- ischemic cardiomyopathy, heart class, and heart failure hospital admissions. Patients with impedance-monitoring ICDs were told to see their doctor whenever the device sounded a warning of increasing fluid buildup. That happened 18 times, including 4 in which the alarm was not right. One patient needed hospitalization after ignoring the ICD's alarm for 13 days. This looks promising IF the technology can be improved and made widely available for all CHFers who get implanted devices. Sources: J Am Coll Cardiol 2006; 47:2245-2252. Title: Utility of impedance cardiography for the identification of short-term risk of clinical decompensation in stable patients with chronic heart failure. Authors: Packer M, Abraham WT, Mehra MR, et al. Source: Heart Rhythm Society 2006 Scientific Sessions; May 19, 2006; Boston, MA Abstract AB48-4. Title: Case-control study about the usefulness of intrathoracic fluids accumulation monitoring in the management of heart failure patients. Authors: Maines M, Catazariti D, Cemin C, et al.