Wednesday, March 6, 2013

Periodic limb movements in sleep, heart abnormalities, and hemodialysis

Periodic limb movements in sleep (PLMS) are repetitive, small leg jerks that occur during sleep, usually without any memory of it happening. However, PLMS can fragment sleep and have been linked to increased cardiovascular risk factors. Restless legs syndrome (RLS) is linked to PLMS - most RLS patients have PLMS. RLS and PLMS are common in hemodialysis patients. And hemodialysis itself is linked to cardiovascular disease. This study sought to determine if patients with RLS and PLMS on hemodialysis had a deterioration in heart structure and function compared to those RLS patients without PLMS.

Researchers used a cutoff value for the PLMS that puts them in the moderate to severe amount - this is most likely to be clinically significant. Results showed that resting heart rate and blood pressure (BP) were similar in those with and without PLMS. The minimum systolic BP (referring to the 120 in "120 over 80" for example) was higher in the PLMS group. Also, the percent reduction of BP during sleep, compared to being awake, was 50% smaller in the PLMS group. This means that those with PLMS did not experience as much a dip in BP during sleep - something that could lead to high blood pressure in the daytime. The mass of the left side of the heart was greater in PLMS group, but both groups had hearts that could pump out the same amount of blood per beat.

The authors concluded that PLMS can alter the structure of the heart, but not necessarily its function. They feel that PLMS do this by raising blood pressure during sleep. The heart gets larger when it has to pump against a higher blood pressure, which can lead to the results obtained in this study. Of note, the RLS itself was not associated with the heart structure changes.

What does this mean? It means that patients with RLS on hemodialysis may need to be studied for PLMS. More studies will be needed though to find out if treating PLMS improves results.

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