A Medical Device Daily
A diagnostic test intended to identify patients who should receive heart defibrillators did not produce conclusive data, according to initial results from a clinical trial presented Tuesday at the annual scientific sessions of the American Heart Association (Dallas) in Orlando.
Cambridge Heart (Bedford, Massachusetts) and Medtronic (Minneapolis) sponsored the trial, called MASTER I. The trial monitored a group of patients who all had the devices.
According to Medtronic, the trial is among the most rigorous yet for a test made by Cambridge Heart. The test monitors variations in a portion of the heartbeat called the T-wave while a patient exercises.
Cambridge Heart has said its test can help doctors predict which patients with damaged and failing hearts were most likely to suffer the potentially fatal rhythm problems that can be corrected by a shock from an implanted defibrillator.
However, the preliminary results of the clinical trial indicated the test had little predictive value. Defibrillators have saved thousands of lives, Medtronic noted, but studies have shown that well over half the patients who undergo the risks of getting the implants, which cost as much as $35,000, never need a shock.
According to Cambridge Heart’s theory, a person with a normal T-wave would rarely require life-saving shocks from their defibrillators.
In the clinical trial, while the 575 patients with normal T-waves received somewhat fewer shocks, the difference was so small that it might be a matter of chance, Medtronic said. And so the Cambridge Heart test could not be relied on to separate which patients actually needed the defibrillators.
The company said the trial might be flawed because it used shocks from the devices as the measure of which patients suffered life-threatening heart irregularities.
Such devices are known to sometimes give shocks in response to non-lethal signals.
A second portion of the trial, MASTER 2, will compare the T-wave test’s performance as a predictor of seizures in patients who did not get defibrillators with the group that did get the implants.
In other news from the AHA conference this week:
• Medtronic also reported that new baseline data from what the company calls the largest study of U.S.-based heart failure (HF) patients in the outpatient setting demonstrates “significant underutilization of many guideline-indicated life-saving medical and device therapies.”
Data from the Registry to Improve the Use of Evidence-Based Heart Failure Therapies in the Outpatient Setting (IMPROVE HF) show substantial variances in the use of all guideline-recommended treatments for HF patients, according to Medtronic, the study’s sponsor.
According to the baseline results, the use of ACE inhibitors/ARBs (angiotensin II receptor blockers) and beta-blockers were relatively high in patients eligible for these therapies (80% and 86% of eligible patients, respectively). However, fewer patients received other life-saving treatments and devices for which they were eligible based on current medical guidelines. These included: aldosterone antagonists (36% of eligible patients); anticoagulation for atrial fibrillation (69% of eligible patients); cardiac resynchronization therapy (CRT), including both CRT-defibrillators (CRT-D) and CRT-pacemaker devices (39% of eligible patients); Implantable cardioverter defibrillator (ICD) therapy, including both ICD-only and CRT-D devices (51% of eligible patients); and HF education (61% of eligible patients).
• Data was presented from another Medtronic-sponsored study showing that the application of clinical practice modifications combined with advanced electronic technologies can improve the care of patients at risk for sudden cardiac arrest (SCA).
Recognition of at-risk patients improved from a baseline of 24% to 70% at regional clinics not using the process, and to 93% at the main clinic applying this process and technology, the company said.
The study was intended to compare the effect of specific clinical practice processes and tools on the ability of clinicians to recognize patients at risk for SCA, and apply the appropriate treatment guidelines for those patients.
According to the company, clinic staff was trained to use a new process to better identify at-risk patients, which included: a clinical decision support tool for Electronic Medical Record (EMR) systems that automatically identified patients at risk and continued tracking of those patients who did not immediately qualify for ICD therapy; a standardized patient education process and education video; and broad operational and workflow changes.
Medtronic said the clinical practice process included optimal medical treatment prior to an ICD, temporary and absolute exclusions for ICD therapy, and is based on AHA/American College of Cardiology (ACC; Washington) and the Centers for Medicare & Medicaid Services guidelines with practice-specific requirements. An independent review of medical charts for all patients visiting the main clinic (the group using the new process) and regional clinics (those that did not use the process) was conducted over a two-month period; patients were followed for six months, the company noted.
• Humacyte (Hillsborough, North Carolina) reported that data presented at the conference demonstrates the longevity and durability of acellular arterial bypass grafts.
Company scientists, working with researchers at East Carolina Heart Institute (Greenville, North Carolina), showed the potential for the naturally-derived vascular devices to provide a commercially viable solution for patients requiring vascular replacement or vascular access, Humacyte said.
In the studies, scientists began by seeding smooth muscle cells on a tubular biodegradable scaffold, which produced extracellular matrix (ECM) proteins in the shape of blood vessels, the company said. Following a two-month growth period, researchers removed the smooth muscle cells, leaving behind the intact ECM, thereby making them universally compatible. The removal of cells further provides the vessels with a significant shelf-life for off-the-shelf applications. The acellular grafts were surgically implanted in adult canines either as a carotid or coronary bypass grafts. The arterial bypass grafts were found to be functional for up to 12 months in the canine recipients. They remained clear of obstructions for the length of the study, and demonstrated no vessel narrowing, dilatation, or calcification.
Humacyte grows medical devices from human cells.