Staff Report

Medtronic (Minneapolis) revealed the results of a new study which found that atrial fibrillation (AF) and bradycardia – two common heart rhythm disorders – occurred at higher than expected, and clinically significant, rates in patients with end-stage renal disease (ESRD) undergoing hemodialysis. Moreover, these rhythm disorders appeared to correlate with patients' dialysis cycles, occurring immediately before, during and after their dialysis sessions. The irregular heartbeats were found in the Monitoring in Dialysis (MiD) Study using the Medtronic Reveal XT Insertable Cardiac Monitor (ICM). The data were presented at Kidney Week 2014: the American Society of Nephrology 47th Annual Meeting.

"It has been known that patients with end-stage renal disease are at significant risk for cardiac arrhythmias and sudden death. While it has been assumed that fluid and electrolyte imbalances are key contributors to the development of arrhythmias, other factors, including ventricular hypertrophy and cardiac fibrosis, also may exacerbate the underlying risk," said study co-author James Tumlin, professor, Renal Division at the University of Tennessee College of Medicine. "The data presented today underscore the high prevalence of arrhythmias in ESRD patients, as demonstrated by this technology, and suggest a need for intensive monitoring."

The MiD Study monitored arrhythmias in 50 hemodialysis ESRD patients at eight sites during a six-month period using the Reveal XT ICM, a cardiac monitoring device inserted under the skin of the chest that tracks the heart's activity for up to three years. The preliminary analysis found that:

• Heart arrhythmias were strongly associated with the hemodialysis schedule: Patients' risk for cardiac rhythm problems peaked during the 12-hour interval beginning with each session, decreased for the next 12 hours, and then gradually increased during the remainder of the interdialytic interval (the interval between dialysis sessions).

• Atrial fibrillation is commonly experienced by these patients: In the study, 52% of patients experienced AF. A total of 1,640 AF episodes of six minutes or longer were detected in 22 of 50 patients, and the rate of AF events was nearly four times higher in the 12 hours following dialysis.

• Bradycardia (slow heart rates) occurred more frequently than ventricular tachycardia (abnormal and dangerous rapid or chaotic heart rhythms): In the study, 19 of 50 patients had at least one bradycardia episode (with a rate of 26 bradycardia events per patient month); there were only two sustained ventricular arrhythmia episodes during the follow-up. To date, five patients have received pacemakers following the detection of their bradycardia.

ESRD is the final stage of kidney failure, when the kidneys lose the ability to filter wastes and extra fluids from the body. Because ESRD is permanent, patients require a transplant or ongoing dialysis treatment, where a machine acts as the kidney filter.

"The Reveal XT device used in the MiD study is a long-term monitor that offers a new approach to managing patients on hemodialysis by identifying clinically-significant abnormal heart rhythms – when they occur – so that patients can receive appropriate treatment," said Nina Goodheart, VP/GM of the Diagnostics and Monitoring Business at Medtronic. "Effective cardiac monitoring can lead to better patient outcomes, and may lead to even more efficient delivery of care with economic benefits."

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