Cardiologist Dr. John Boehmer spends many of his days assisting individuals who have heart disease, a condition affecting approximately 5.7 million US adults, according to the American Heart Association.

John Boehmer

The patients often require mechanical blood pumps, transplants, and remotemonitoring devices. Boehmer has tested a new sensor system intended to keep heart failure patients going, without the need for advanced therapies.

An international team of investigators, including researchers from the Penn State College of Medicine, led by Boehmer, uploaded software to the existing defibrillator implants of approximately 900 heart failure patients. The sensor technology from Marlborough, MA-based Boston Scientific, called HeartLogic, predicts heart failure events by detecting signs that indicate a patient's worsening condition.

The Hardware

Hospitalization — and re-hospitalization — rates caused by heart failure conditions remain high. Statistics from the Centers for Disease Control and Prevention (CDC) show that heart failure costs the nation an estimated $30.7 billion each year, including the expense of healthcare services, medications to treat heart failure, and missed days of work.

The HeartLogic™ Heart Failure Diagnostic Service aims to prevent hospitalizations by proactively providing warnings to patients. The HeartLogic system contains the standard hardware found in an implantable cardioverter defibrillator (ICD): electric leads, a pulse generator, and an accelerometer that sits in a titanium case on the chest. With leads attached to the right atrium, right ventricle, and left ventricle, the battery-powered device sends stabilizing electrical signals to better coordinate the contractions of the heart.

In the study, the uploaded software converted market-release CRT defibrillators into research devices.

Remote Monitoring Options

The ENERGEN ICD from Boston Scientific. (Credit: Boston Scientific)

Device makers have been using the data routinely collected by an ICD or pacemaker to try to determine a patient's condition. Many heart monitoring technologies detect thoracic impedance, or the measurement of the resistance to electrical activity in the chest, as well as find patterns in heart rate and activity.

The FDA-approved CardioMEMS™ HF System — a wireless pulmonary artery pressure sensor from the St. Paul, MN-based St. Jude Medical — measures hemodynamics, or the pressures within the circulating bloodstream. Products such as ReDS™ technology from Sensible Medical, headquartered in Netanya, Israel, use dielectric signals to estimate wetness of the lungs, an important indicator of heart disease.

HeartLogic takes the added step of monitoring respiration and heart reverberations, while also combining the parameters to derive a composite, heart-specific score or baseline. HeartLogic's accelerometer signal can be filtered to detect vibrations in the audible frequency range that represent heart sounds. The accelerometer was always there; the software to pick up the heart resonances was not.

The HeartLogic technology also monitors the change in electrical impedance that occurs during a patient's breathing cycle. When a patient breathes, more air exists between the heart's lead electrodes and the chest's ICD, increasing impedance.

Using the impedance detected between the HeartLogic's lead and pulse generator, the system additionally examines how the hemodynamics and lung conditions are impacting breathing rates, thoracic impedance, heart rate, and activity. To Boehmer, the technology aims to answer a next-level question: Is the patient struggling in any way that can be manifested by heart rate, respiration, activity decreases, or change in heart sound?

“I think it's going to be an intriguing evolution and series of investigation that's going to tell us which signals are the most important to look at and which ones do we have to optimize in order to get the best outcomes for our patients,” said Boehmer.

The CardioMEMS™ HF System. (Credit: St. Jude Medical)

Going to Trial

The updated sensor system was tested on 900 heart failure patients requiring ICDs. The group had low left ventricular ejection fraction (LVEF), the measurement of how much blood is being pumped from the heart's main pumping chamber with each contraction.

The trial's data demonstrated that the HeartLogic alert had a low rate of “unexplained alerts,” or notifications not followed by a heart failure event, of 1.47 per patient per year. Additionally, the study's data showed that notifications could successfully warn clinicians of an associated heart failure event with a 34-day median alert range — a significant amount of time, according to Boehmer.

“That gives you a big window of time to do something,” said Boehmer. “The concept here is we want to spend our time working with people who are at risk. If you're doing fine, why bring you in to see us?”

In November of 2016, Boston Scientific announced results from the clinical trial, evaluating the performance of the HeartLogic™ Heart Failure Diagnostic Service.

Next, Boehmer will lead more trials to determine the best way to treat a HeartLogic score. A future pilot study will test the system's safety and physician acceptance, monitoring how doctors respond to the system's notifications. Boehmer says the upcoming trials will be necessary to move the technology forward and make the system an essential part of heart failure treatment.

“We have too many hospitalizations on an annual basis,” said Boehmer. “This is a way to try and get ahead of that, and try to treat patients before they become ill.”

This article was written by Billy Hurley, Associate Editor, NASA Tech Briefs. To submit comments and questions, email This email address is being protected from spambots. You need JavaScript enabled to view it..

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This article first appeared in the March, 2017 issue of Sensor Technology Magazine.

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