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Membrane dysfunction in Andersen‐Tawil syndrome assessed by velocity recovery cycles
Author(s) -
Tan S. Veronica,
Z'Graggen Werner J.,
BoËrio Delphine,
Rayan Dipa L. Raja,
Howard Robin,
Hanna Michael G.,
Bostock Hugh
Publication year - 2012
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.23293
Subject(s) - stimulation , medicine , refractory period , anesthesia , depolarization , channelopathy , cardiology
Andersen‐Tawil syndrome (ATS) due to Kir2.1mutations typically manifests as periodic paralysis, cardiac arrhythmias and developmental abnormalities but is often difficult to diagnose clinically. This study was undertaken to determine whether sarcolemmal dysfunction could be identified with muscle velocity recovery cycles (MVRCs). Methods: Eleven genetically confirmed ATS patients and 20 normal controls were studied. MVRCs were recorded with 1, 2, and 5 conditioning stimuli and with single conditioning stimuli during intermittent repetitive stimulation at 20 Hz, in addition to the long exercise test. Results: ATS patients had longer relative refractory periods ( P < 0.0001) and less early supernormality, consistent with membrane depolarization. Patients had reduced enhancement of late supernormality with 5 conditioning stimuli ( P < 0.0001), and less latency reduction during repetitive stimulation ( P < 0.001). Patients were separated completely from controls by combining MVRC and repetitive stimulation. Conclusions: MVRCs combined with repetitive stimulation differentiated ATS patients from controls more effectively than the conventional long‐exercise test. Muscle Nerve 46: 193–203, 2012