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A retrospective analysis of ECG event loop recorders, diagnostic yield versus duration
Abstract
S224
Electrophysiology - basic (267–291) 267 A novel kinetic model based on the Albers-Post scheme that mimics the behaviour of the Na+, K+-ATPase in situ A. Garcia 1,∗ , H. Rasmussen 1 , R. Clarke 2 1 Kolling
Institute of Medical Research, University of Sydney, Australia 2 School of Chemistry, University of Sydney, Australia Glutathionylation of the 1 subunit of the Na+, K+-ATPase is a relatively recently reported posttranslational modification that regulates activity via intracellular oxidant signalling pathways. The determination of which partial reactions of the overall ATPase reaction cycle are modified has important ramifications regarding structure, interactions between the ATPase and its surrounding lipid membrane environment and functional aspects, especially under pathophysiological conditions. In this study we incorporate glutathionylation into a current kinetic model of the ATPase determined from the study of partial reactions in the pig kidney enzyme. We use voltage clamped cardiomyocyte and protein immunoblotting data to determine the probable sites of glutathionylation within the enzyme cycle. Using the nomenclature of the Albers-Post scheme results from K+ activated transients indicate that both E2P and the E1K states of the ATPase cycle are highly susceptible to glutathionylation. Results are corroborated by protein immunoblotting experiments on purified pig kidney enzyme. The kinetic model with glutathionylation incorporated faithfully replicates a series of K+ activated transient experiments in cardiomyocytes and experiments altering intracellular oxidant status by including superoxide dismutase in the patch pipette. The incorporation of glutathionylation into the ATPase cycle is the first ever kinetic model that has the ability to reproduce voltage clamped cardiomyocyte experimental data. This novel model offers the possibility of redefining the origin of several experimental observations such as K+ activated transients, apparent changes to intracellular Na+ affinities and the ATPase response to changes in intracellular redox balance. http://dx.doi.org/10.1016/j.hlc.2015.06.268 268 A retrospective analysis of ECG event loop recorders, diagnostic yield versus duration L. Cleave ∗ , J. Hill, W. Vollbon Princess Alexandra Hospital, Australia Background: ECG Event loop recordings (EELR) are used to diagnose symptomatic arrhythmias, however few Australian data exist regarding optimal test duration. We compared the diagnostic yields of 1, 2, 3 and 4-week durations of EELR at an Australian Tertiary Referral Centre. Methods: Data were analysed from 238 EELR for positive (symptom-arrhythmia correlation), negative or incidental findings between January 2012 and March 2014
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Results: Of 238 total tests, 139 (58.4%) were performed over 1 week or less, 88 (36.9%) over 2 weeks, 5 (2.1%) over 3 weeks and 6 (2.6%) over 4 weeks. Results of 10 tests (4.2%) were excluded due to technical issues. 15 tests (6.6%) revealed incidental findings. Of the 81 positive tests (35.5%), mean time to positivity was 1.06 ± 0.23 weeks. Of 135 analysable tests over 1 week or less, 45 were positive (33.3%), 79 were negative (58.5%) and 11 produced incidental findings (8.2%). Of 93 analysable 2-, 3- and 4-week tests, 36 were positive (38.7%), of which 21 tests were deemed positive at 1 week (58%), 4 in the second week (11%) and one in the fourth week (3%). In 10 EELR >1 week, timing of positivity could not be determined.
Conclusions: The diagnostic yield is highest in the first week of EELR then decreases sharply thereafter. Incidental findings occur in a small fraction of EELR, but again mostly in the first week. EELR exceeding 2 week duration have minimal value. These findings have important relevance to resource utilisation. http://dx.doi.org/10.1016/j.hlc.2015.06.269 269 An unusual case of transient conduction disturbance N. Whitehead ∗ , M. Barlow Department of Cardiovascular Medicine, John Hunter Hospital, Hunter New England Local Health District, Australia A previously fit and well 25-year-old man presented to hospital with syncope and recurrent presyncope over 48 hours. Heart rate was 27bpm, but examination was otherwise unremarkable. ECG demonstrated complete heart block with narrow and normal QRS complex. 600microg of atropine resulted in transient sinus tachycardia with first degree heart block (400msec) and intermittent second degree heart block followed by recurrence of complete heart block. During transfer to a tertiary hospital he experienced ventricular pauses of up to 11 seconds duration. A temporary pacemaker was placed. He remained pacing dependent for 16 hours. Subsequently his conduction improved and ECGs revealed only first degree heart block which progressively improved from a PR interval of 400msec, to 180msec over 5 days. There was no history of medications, illicit drug use, unusual ingestion, autoimmune disease, or overseas travel. Past ECGs were normal. Investigations including electrolytes, troponins, inflammatory markers, echocardiogram, and cardiac MRI were unremarkable. After discussion with the patient, a decision was made for monitoring. The pacing lead was removed and an implantable loop recorder was placed. After nine months of follow-up he has had no further syncope and the loop recorder has not detected any episodes of signifi-
S224
Electrophysiology - basic (267–291) 267 A novel kinetic model based on the Albers-Post scheme that mimics the behaviour of the Na+, K+-ATPase in situ A. Garcia 1,∗ , H. Rasmussen 1 , R. Clarke 2 1 Kolling
Institute of Medical Research, University of Sydney, Australia 2 School of Chemistry, University of Sydney, Australia Glutathionylation of the 1 subunit of the Na+, K+-ATPase is a relatively recently reported posttranslational modification that regulates activity via intracellular oxidant signalling pathways. The determination of which partial reactions of the overall ATPase reaction cycle are modified has important ramifications regarding structure, interactions between the ATPase and its surrounding lipid membrane environment and functional aspects, especially under pathophysiological conditions. In this study we incorporate glutathionylation into a current kinetic model of the ATPase determined from the study of partial reactions in the pig kidney enzyme. We use voltage clamped cardiomyocyte and protein immunoblotting data to determine the probable sites of glutathionylation within the enzyme cycle. Using the nomenclature of the Albers-Post scheme results from K+ activated transients indicate that both E2P and the E1K states of the ATPase cycle are highly susceptible to glutathionylation. Results are corroborated by protein immunoblotting experiments on purified pig kidney enzyme. The kinetic model with glutathionylation incorporated faithfully replicates a series of K+ activated transient experiments in cardiomyocytes and experiments altering intracellular oxidant status by including superoxide dismutase in the patch pipette. The incorporation of glutathionylation into the ATPase cycle is the first ever kinetic model that has the ability to reproduce voltage clamped cardiomyocyte experimental data. This novel model offers the possibility of redefining the origin of several experimental observations such as K+ activated transients, apparent changes to intracellular Na+ affinities and the ATPase response to changes in intracellular redox balance. http://dx.doi.org/10.1016/j.hlc.2015.06.268 268 A retrospective analysis of ECG event loop recorders, diagnostic yield versus duration L. Cleave ∗ , J. Hill, W. Vollbon Princess Alexandra Hospital, Australia Background: ECG Event loop recordings (EELR) are used to diagnose symptomatic arrhythmias, however few Australian data exist regarding optimal test duration. We compared the diagnostic yields of 1, 2, 3 and 4-week durations of EELR at an Australian Tertiary Referral Centre. Methods: Data were analysed from 238 EELR for positive (symptom-arrhythmia correlation), negative or incidental findings between January 2012 and March 2014
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
Results: Of 238 total tests, 139 (58.4%) were performed over 1 week or less, 88 (36.9%) over 2 weeks, 5 (2.1%) over 3 weeks and 6 (2.6%) over 4 weeks. Results of 10 tests (4.2%) were excluded due to technical issues. 15 tests (6.6%) revealed incidental findings. Of the 81 positive tests (35.5%), mean time to positivity was 1.06 ± 0.23 weeks. Of 135 analysable tests over 1 week or less, 45 were positive (33.3%), 79 were negative (58.5%) and 11 produced incidental findings (8.2%). Of 93 analysable 2-, 3- and 4-week tests, 36 were positive (38.7%), of which 21 tests were deemed positive at 1 week (58%), 4 in the second week (11%) and one in the fourth week (3%). In 10 EELR >1 week, timing of positivity could not be determined.
Conclusions: The diagnostic yield is highest in the first week of EELR then decreases sharply thereafter. Incidental findings occur in a small fraction of EELR, but again mostly in the first week. EELR exceeding 2 week duration have minimal value. These findings have important relevance to resource utilisation. http://dx.doi.org/10.1016/j.hlc.2015.06.269 269 An unusual case of transient conduction disturbance N. Whitehead ∗ , M. Barlow Department of Cardiovascular Medicine, John Hunter Hospital, Hunter New England Local Health District, Australia A previously fit and well 25-year-old man presented to hospital with syncope and recurrent presyncope over 48 hours. Heart rate was 27bpm, but examination was otherwise unremarkable. ECG demonstrated complete heart block with narrow and normal QRS complex. 600microg of atropine resulted in transient sinus tachycardia with first degree heart block (400msec) and intermittent second degree heart block followed by recurrence of complete heart block. During transfer to a tertiary hospital he experienced ventricular pauses of up to 11 seconds duration. A temporary pacemaker was placed. He remained pacing dependent for 16 hours. Subsequently his conduction improved and ECGs revealed only first degree heart block which progressively improved from a PR interval of 400msec, to 180msec over 5 days. There was no history of medications, illicit drug use, unusual ingestion, autoimmune disease, or overseas travel. Past ECGs were normal. Investigations including electrolytes, troponins, inflammatory markers, echocardiogram, and cardiac MRI were unremarkable. After discussion with the patient, a decision was made for monitoring. The pacing lead was removed and an implantable loop recorder was placed. After nine months of follow-up he has had no further syncope and the loop recorder has not detected any episodes of signifi-