A novel technique for analysing beat-to-beat dynamical changes of QT-RR distribution for arrhythmia prediction

Ventricular tachycardia (VT) leading to ventricular fibrillation (VF) is the major cause of sudden cardiac death (SCD) with subjects with or without any history of cardiac disease. Prediction of the initiation of ventricular fibrillation is crucial for both successful preventive measure and effective defibrillation therapy. A lot of studies have been done based on electrocardiogram (ECG) waveform analysis for VF detection but this field still needs more perfection. Both HRV and QTV related parameters were reported to be analysed for VT/VF detection and prediction with inconsistent results in different populations. In this study, we propose a novel time domain measurement tool to detect the pattern of dynamical changes of both RR and QT intervals in subjects having sustained VT/VF episodes form VFDB and AHA database (www.physionet.org). We also analyse the same pattern in some healthy subjects from Fantasia database and compare the distribution of patterns between healthy and VT/VF subjects. Our findings showed that the distribution of QT-RR dynamics are statistically significantly different (p<0.05) in healthy subjects from VT/VF in particular before the start of VF episode. Therefore, distribution of change in QT-RR dynamics may provide insight of the underlying instability before VF events and can be used for better prediction of arhythmogenesis.

Multi-lag HRV analysis discriminates disease progression of post-infarct people with no diabetes versus diabetes

Diabetes mellitus is associated with multi-organ system dysfunction including the cardiovascular and autonomic nervous system. Although it is well documented that post-infarct patients are at higher risk of sudden cardiac death, diabetes adds an additional risk associated with autonomic neuropathy. However it is not known how the presence of diabetes in post-infarct patients affects cardiac rhythm. The majority of HRV algorithms for determining cardiac inter-beat interval changes describe only beat-to-beat variation determined over the whole heart rate recording and therefore do not consider the ability of a heart beat to influence a train of succeeding beats nor whether or how the temporal dynamics of the inter-beat intervals changes. This study used Poincaré Plot derived features and incorporated increased lag intervals to compare post-infarct patients with no history of prior infarct with or without diabetes and found that for the nondiabetic post-infarct patients only increased lag of short term correlation (SD1) predicted mortality, whereas in the diabetic post-infarct group only long-term correlations (SD2) significantly predicted mortality at a follow-up period of eight years. Temporal dynamics measured as a complex correlation measure (CCM) was also a significant predictor of mortality only in the diabetic post-infarct cohort. This study highlights the different pathophysiological progression and risk profile associated with presence of diabetes in a post-infarct patient population at eight year follow-up.

Analysis of the impact of limitation of medical treatment orders during unplanned transfers from sub-acute care to emergency departments

BACKGROUND: The impact of limitation of medical treatment orders (LOMT) on patient outcomes following transfer from sub-acute care to the Emergency Department remains unclear.

METHODS: Retrospective medical record review of 431 adult in-patients who required ambulance transfer following clinical deterioration during a sub-acute care admission during 2010.

RESULTS: Common reasons for transfer were respiratory (18.9%) or neurological (19.0%) conditions; 35.7% (154/431) were transferred within one week of sub-acute care admission. LOMT orders were in place for 37.8% (n=163) patients who were older (p<0.001), with more comorbidities (p<0.005), specifically cardiac, renal and pulmonary disease than patients without LOMT. Patients with LOMT orders had more physiological abnormalities before transfer; tachypnoea (43.7% vs 28.6%), hypoxaemia (63.5% vs 48.4%) and severe hypoxaemia (27.6% vs 14.5%). There were no differences in rates of admission, cardiac arrest, Medical Emergency Team activation or ICU admission. For admitted patients, those with LOMT orders had significantly (p≤0.005) higher mortality: in-hospital (21.9% vs 11.3%); 30 days (23.9% vs 12.3%) and 60 days (28.2% vs 13.4%).

CONCLUSIONS: Patients with LOMT had higher levels of comorbidity and were more acutely ill during their sub-acute care admission. Once transferred those with a LOMT had similar rates of cardiac arrest, MET activation and unplanned ICU admission, but higher mortality.

Interventions for nurses caring for a child who has an unexpected acute life threatening event (ALTE) in hospital

Introduction: Caring for a child who has an unexpected ALTE in hospital can be stressful. An ALTE may include a cardiac arrest, respiratory arrest or call for immediate assistance. An international survey of practice was conducted to identify any existing interventions to inform a PhD program of work aimed at reducing the stress from these events through preparation and support. Purpose: The purpose of the survey was threefold: (1) Describe ‘normal’ practice when it comes to preparing staff or providing psychological support after caring for a child who has had an ALTE. (2) Determine if there are any interventions to prepare clinical staff for potential psychological effects of caring for a child who has an ALTE. (3) Determine if there are any interventions to provide support for clinical staff after caring for a child who has an ALTE. Material - Methods: An 18 item semi structured questionnaire was designed for the study to allow respondent to describe practices within their institution and outline their opinions and professional experiences. Clinicians from selected children’s and adult hospitals in Australia, Canada, New Zealand, United Kingdom and the United States of America were contacted by telephone. Following consent they were given the option to complete the survey via the telephone, by post or online. Results: Of the 61 hospitals approached 44 (72%) clinicians responded. Eighteen (41%) respondents identified interventions in place to prepare nurses for an ALTE ranging from (but not limited to) ad hoc discussions during life support training through to structured simulation training. Thirty-six (82%) respondents identified that they had interventions in place to support nurses after an ALTE ranging from (but not limited to) debriefing through to structured case reviews. Conclusions: Interventions varied across institutions, with no outcome or evaluation data for the interventions published to date.

Sjuksköterskestudenters upplevelse av förberedelse inför hjärtstopp : En empirisk studie

Introduktion: Årligen drabbas cirka 15 000 personer av hjärtstopp i Sverige. Sjuksköterskanhar ett stort i ansvar i omvårdnaden vid hjärtstopp. Sjuksköterskeutbildningen strävar efter attförbereda studenterna inför omvårdnad vid hjärtstopp. Syfte: Att belysasjuksköterskestudenters upplevelse av förberedelse inför att utöva omvårdnad av patienter samband med hjärtstopp. Metod: Kvalitativ design med semistrukturerade intervjuer. Undersökningsgruppen bestämdes av bekvämlighetsurval. 16 sjuksköterskestudenter i termin 6 intervjuades och data analyserades med hjälp av innehållsanalys. Resultat: Resultatet avstudien visade på att informanterna kände en otrygghet i sig själva, och var osäkra inför attutföra hjärt- och lungräddning för första gången på grund av bristande erfarenhet samt för litekunskap. Informanterna upplevde dock trygghet när de hade erfarna kollegor runt omkring sigsamt när de hade upplevt en riktig hjärtstoppssituation själva. Slutsats: Utifrån studiens resultatbedöms att sjuksköterskestudenter inte känner sig trygga i sig själva och i sin förmåga att utföraadekvat S-HLR, samt inte upplever sig vara förberedda inför att hantera en hjärtstoppssituation.

The importance of physical fitness in the performance of adequate cardiopulmonary resuscitation

The aim of the present investigation was to evaluate the influence of the physical fitness of a cardiopulmonary resuscitation (CPR) provider on the performance of and physiologic response to CPR. To this end, comparisons were made of sedentary and physically active subjects in terms of CPR performance and physiologic variables. Two study groups were established: group P (n = 14), composed of sedentary, professional CPR rescuers (mean [± SD]; age, 34 ± 6 years; V̇O2max, 32.5 ± 5.5 mL/kg/min), and group Ex (n = 14), composed of physically active, nonexperienced subjects (age, 34 ± 6 years; V̇O2max, 44.5 ± 8.5 mL/kg/min). Each subject was required to perform an 18-min CPR session, which involved manual external cardiac compressions (ECCs) on an electronic teaching mannequin following accepted standard CPR guidelines. Subjects' gas exchange parameters and heart rates (HRs) were monitored throughout the trial. Variables indicating the adequacy of the ECCs (ECC depth and the percentage of incorrect compressions and hand placements) also were determined. Overall CPR performance was similar in both groups. The indicators of ECC adequacy fell within accepted limits (ie, an ECC depth between 38 and 51 mm). However, fatigue prevented four subjects from group P from completing the trial. In contrast, the physiologic responses to CPR differed between groups. The indicators of the intensity of effort during the trial, such as HR or percentage of maximum oxygen uptake (V̇O2max) were higher in group P subjects than group Ex subjects, respectively (HRs at the end of the trial, 139 ± 22 vs 115 ± 17 beats/min, p < 0.01; percentage of V̇O2max after 12 min of CPR, 46.7 ± 9.7% vs 37.2 ± 10.4%, p < 0,05). These results suggest that a certain level of physical fitness may be beneficial to CPR providers to ensure the adequacy of chest compressions performed during relatively long periods of cardiac arrest.

SOCIAL REPRESENTATIONS OF BASICS LIFE SUPPORT

Victims of cardiac arrest need immediate Basic Life Support, in order to preserve as much as possible, the flow of blood to the brain and heart and other vital organs, it is essential to gain time pending differentiated help, performing simple acts and practical (BLS) to save lives. Learn how to perform RPC is an interactive process that requires knowledge and skills, but at the same time an act of solidarity, social responsibility, civic consciousness, and a duty of citizenship. Because no one revives alone, it requires a coordinated work of a team, all citizens must join forces in a single goal: Save Lives, the massification of the BLS (RPC, 2014). We conducted an exploratory study that aimed to identify the social representations of basic life support in the general population. We used the technique of free association of words through a short questionnaire, we obtained a sample of 45 participants. The results show that participants were mostly female and 27 that fashion of age was in the age group 40 to 59 years. With regard to social representations, we find an organized structure follows the core: help, help to revive, and save is giving life, are in fact structural and consensual elements in basic life support. In more peripheral elements we find extremely important elements, which can be worked in a way so that the core is more efficient such as to act coordinately as a team in face of an accident, it can thus be successful in practice. The social representation of basic life support does not differ from that referred in the literature on the subject, but it is common knowledge that these skills can only be acquired if they are systematically trained, because they obey an algorithm that if it is not settled theoretical and instrumentally it is not effective in practice.

Cardiac channel molecular autopsy: insights from 173 consecutive cases of autopsy-negative sudden unexplained death referred for postmortem genetic testing

OBJECTIVE To perform long QT syndrome and catecholaminergic polymorphic ventricular tachycardia cardiac channel postmortem genetic testing (molecular autopsy) for a large cohort of cases of autopsy-negative sudden unexplained death (SUD). METHODS From September 1, 1998, through October 31, 2010, 173 cases of SUD (106 males; mean ± SD age, 18.4 ± 12.9 years; age range, 1-69 years; 89% white) were referred by medical examiners or coroners for a cardiac channel molecular autopsy. Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing, a comprehensive mutational analysis of the long QT syndrome susceptibility genes (KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2) and a targeted analysis of the catecholaminergic polymorphic ventricular tachycardia type 1-associated gene (RYR2) were conducted. RESULTS Overall, 45 putative pathogenic mutations absent in 400 to 700 controls were identified in 45 autopsy-negative SUD cases (26.0%). Females had a higher yield (26/67 [38.8%]) than males (19/106 [17.9%]; P<.005). Among SUD cases with exercise-induced death, the yield trended higher among the 1- to 10-year-olds (8/12 [66.7%]) compared with the 11- to 20-year-olds (4/27 [14.8%]; P=.002). In contrast, for those who died during a period of sleep, the 11- to 20-year-olds had a higher yield (9/25 [36.0%]) than the 1- to 10-year-olds (1/24 [4.2%]; P=.01). CONCLUSION Cardiac channel molecular autopsy should be considered in the evaluation of autopsy-negative SUD. Several interesting genotype-phenotype observations may provide insight into the expected yields of postmortem genetic testing for SUD and assist in selecting cases with the greatest potential for mutation discovery and directing genetic testing efforts.

Alpha1-syntrophin mutations identified in sudden infant death syndrome cause an increase in late cardiac sodium current.

BACKGROUND Sudden infant death syndrome (SIDS) is a leading cause of death during the first 6 months after birth. About 5% to 10% of SIDS may stem from cardiac channelopathies such as long-QT syndrome. We recently implicated mutations in alpha1-syntrophin (SNTA1) as a novel cause of long-QT syndrome, whereby mutant SNTA1 released inhibition of associated neuronal nitric oxide synthase by the plasma membrane Ca-ATPase PMCA4b, causing increased peak and late sodium current (I(Na)) via S-nitrosylation of the cardiac sodium channel. This study determined the prevalence and functional properties of SIDS-associated SNTA1 mutations. METHODS AND RESULTS Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing of SNTA1's open reading frame, 6 rare (absent in 800 reference alleles) missense mutations (G54R, P56S, T262P, S287R, T372M, and G460S) were identified in 8 (approximately 3%) of 292 SIDS cases. These mutations were engineered using polymerase chain reaction-based overlap extension and were coexpressed heterologously with SCN5A, neuronal nitric oxide synthase, and PMCA4b in HEK293 cells. I(Na) was recorded using the whole-cell method. A significant 1.4- to 1.5-fold increase in peak I(Na) and 2.3- to 2.7-fold increase in late I(Na) compared with controls was evident for S287R-, T372M-, and G460S-SNTA1 and was reversed by a neuronal nitric oxide synthase inhibitor. These 3 mutations also caused a significant depolarizing shift in channel inactivation, thereby increasing the overlap of the activation and inactivation curves to increase window current. CONCLUSIONS Abnormal biophysical phenotypes implicate mutations in SNTA1 as a novel pathogenic mechanism for the subset of channelopathic SIDS. Functional studies are essential to distinguish pathogenic perturbations in channel interacting proteins such as alpha1-syntrophin from similarly rare but innocuous ones.

Feasibility of post mortem cardiac proton density weighted fast field echo imaging in two cases of sudden death

OBJECTIVE The aim of this work is to investigate and compare cardiac proton density (PD) weighted fast field echo (FFE) post-mortem magnetic resonance (PMMR) imaging with standard cardiac PMMR imaging (T1-weighted and T2-weighted turbo spin-echo (TSE)), postmortem CT (PMCT) as well as autopsy. MATERIALS AND METHODS Two human cadavers sequentially underwent cardiac PMCT and PMMR imaging (PD-weighted FFE, T1-weighted and T2-weighted TSE) and autopsy. The cardiac PMMR images were compared to each other as well as to PMCT and autopsy findings. RESULTS For the first case, cardiac PMMR exhibited a focal region of low signal in PD-weighted FFE and T2-weighted TSE images, surrounded by a signal intense rim in the T2-weighted images. T1-weighted TSE and PMCT did not appear to identify any focal abnormality. Macroscopic inspection identified a blood clot; histology confirmed this to be a thrombus with an adhering myocardial infarction. In the second case, a myocardial rupture with heart tamponade was identified in all PMMR images, located at the anterior wall of the left ventricle; PMCT excluded additional ruptures. In PD-weighted FFE and T2-weighted TSE images, it occurred hypo-intense, while resulting in small clustered hyper-intense spots in T1-weighted TSE. Autopsy confirmed the PMMR and PMCT findings. CONCLUSIONS Presented initial results have shown PD-weighted FFE to be a valuable imaging sequence in addition to traditional T2-weighted TSE imaging for blood clots and myocardial haemorrhage with clearer contrast between affected and healthy myocardium.

Hypertension, cardiac hypertrophy, and sudden death in mice lacking natriuretic peptide receptor A

Natriuretic peptides, produced in the heart, bind to the natriuretic peptide receptor A (NPRA) and cause vasodilation and natriuresis important in the regulation of blood pressure. We here report that mice lacking a functional Npr1 gene coding for NPRA have elevated blood pressures and hearts exhibiting marked hypertrophy with interstitial fibrosis resembling that seen in human hypertensive heart disease. Echocardiographic evaluation of the mice demonstrated a compensated state of systemic hypertension in which cardiac hypertrophy and dilatation are evident but with no reduction in ventricular performance. Nevertheless, sudden death, with morphologic evidence indicative in some animals of congestive heart failure and in others of aortic dissection, occurred in all 15 male mice lacking Npr1 before 6 months of age, and in one of 16 females in our study. Thus complete absence of NPRA causes hypertension in mice and leads to cardiac hypertrophy and, particularly in males, lethal vascular events similar to those seen in untreated human hypertensive patients.

Adenosine-induced flow arrest to facilitate intracranial aneurysm clip ligation: dose-response data and safety profile.

BACKGROUND: Adenosine-induced transient flow arrest has been used to facilitate clip ligation of intracranial aneurysms. However, the starting dose that is most likely to produce an adequate duration of profound hypotension remains unclear. We reviewed our experience to determine the dose-response relationship and apparent perioperative safety profile of adenosine in intracranial aneurysm patients. METHODS: This case series describes 24 aneurysm clip ligation procedures performed under an anesthetic consisting of remifentanil, low-dose volatile anesthetic, and propofol in which adenosine was used. The report focuses on the doses administered; duration of systolic blood pressure <60 mm Hg (SBP(<60 mm Hg)); and any cardiovascular, neurologic, or pulmonary complications observed in the perioperative period. RESULTS: A median dose of 0.34 mg/kg ideal body weight (range: 0.29-0.44 mg/kg) resulted in a SBP(<60 mm Hg) for a median of 57 seconds (range: 26-105 seconds). There was a linear relationship between the log-transformed dose of adenosine and the duration of a SBP(<60 mm Hg) (R(2) = 0.38). Two patients developed transient, hemodynamically stable atrial fibrillation, 2 had postoperative troponin levels >0.03 ng/mL without any evidence of cardiac dysfunction, and 3 had postoperative neurologic changes. CONCLUSIONS: For intracranial aneurysms in which temporary occlusion is impractical or difficult, adenosine is capable of providing brief periods of profound systemic hypotension with low perioperative morbidity. On the basis of these data, a dose of 0.3 to 0.4 mg/kg ideal body weight may be the recommended starting dose to achieve approximately 45 seconds of profound systemic hypotension during a remifentanil/low-dose volatile anesthetic with propofol induced burst suppression.

The cardiac responses of the scallop Pecten maximus (L.) to respiratory stress

Heart activity of Pecten maximus (L.) has been recorded during various forms of experimentally induced respiratory stress. There was considerable variation in the responses of individual scallops but bradycardia generally occurred in response to all forms of respiratory stress, with the rate of fall in heart rate dependent upon the severity of hypoxia. When oxygen tension declined slowly in a closed respirometer there was regulation of both heart rate and oxygen consumption. The critical tension, Pc, for oxygen consumption lay between 70 and 80 mm Hg, and corresponded with a slight regulatory upswing of the heart rate, whereas the Pc for heart rate was much lower at 20–30 mm Hg. Sudden transfer to deoxygenated water for 3 h resulted in very rapid bradycardia and there was a rapid recovery and initial overshoot of the normal rate on return to well-oxygenated sea water. Aerial exposure for 3 h produced more gradual bradycardia followed by gradual recovery on return to sea water. The results of this work are compared in some detail with previous work on other species of bivalve from different geographical areas and habitats, and the mechanisms controlling cardiac and respiratory regulation are discussed. It is concluded that there are few clear-cut general differences between littoral and sublittoral species in their behavioural and physiological adaptations to hypoxia; the main distinguishing feature of littoral-adapted species is their ability to control air-gaping. Changes in heart activity generally indicate variations in metabolic rate, the speed at which the metabolic rate may be altered reflecting the degree of adaptation to the littoral environment.

Elevated intracardiac angiotensin II leads to cardiac hypertrophy and mechanical dysfunction in normotensive mice

Introduction
Angiotensin II (Ang II) is known to induce cardiac growth and modulate myocardial contractility. It has been reported that elevated levels of endogenous Ang II contribute to the development of cardiac hypertrophy in hypertensives. However, the long-term functional effects of cardiac exposure to Ang II in normotensives is unclear.

A recently developed transgenic mouse (TG1306/1R), in which cardiac-specific overproduction of Ang II produces primary hypertrophy, provides a new experimental model for investigation of this phenotype. The aim of the present study was to use this model to investigate whether there is a functional deficit in primary hypertrophy that may predispose to cardiac failure and sudden death. We hypothesised that primary cardiac hypertrophy is associated with mechanical dysfunction in the basal state.

Methods
Normotensive heterozygous TG1306/1R mice harbouring multiple copies of a cardiac-specific rat angiotensinogen gene were studied at age 30—40 weeks and compared with age-matched wild-type littermates. Left ventricular function was measured ex vivo in bicarbonate buffer-perfused, Langendorffmounted hearts ( at a perfusion pressure of 80 mmHg, 37°C) using a fluid-filled PVC balloon interfaced to a pressure transducer and digital data acquisition system.

Results
There was no difference in the mean (±SEM) intrinsic heart rate of TG1306/1R and wild-type control mice (357.4±11.8 vs. 367.5±20.9 bpm, n=9 & 7). Under standardised end-diastolic pressure conditions, TG1306/1R hearts exhibited a significant reduction in peak developed pressure (132.2±9.4 vs. 161.5±3.1 mmHg, n=9 & 7, p<0.05) and maximum rate of pressure development (3566.7±323.7 vs. 4486.3±109.4 mmHg, n=9 & 7, p<0.05). TG1306/1R mice show a significant correlation between incidence of arrhythmia and increasing heart size (Spearman's correlation coefficient 0.61).

Conclusion
These data demonstrate that chronic in vivo exposure to elevated levels of intra-cardiac Ang II is associated with significant contractile abnormalities evident in the ex vivo intact heart. Our findings suggest that endogenous overproduction of cardiac Ang II, independent of changes in blood pressure, is sufficient to induce ventricular remodelling that culminates in impaired cardiac function which may precede failure.

Undergraduate nursing students' performance in recognising and responding to sudden patient deterioration in high psychological fidelity simulated environments: an Australian multi-centre study

Objectives
This paper reports the quantitative findings of the first phase of a larger program of ongoing research: Feedback Incorporating Review and Simulation Techniques to Act on Clinical Trends (FIRST2ACTTM). It specifically aims to identify the characteristics that may predict primary outcome measures of clinical performance, teamwork and situation awareness in the management of deteriorating patients.

Design
Mixed-method multi-centre study.

Setting
High fidelity simulated acute clinical environment in three Australian universities.

Participants
A convenience sample of 97 final year nursing students enrolled in an undergraduate Bachelor of Nursing or combined Bachelor of Nursing degree were included in the study.

Method
In groups of three, participants proceeded through three phases: (i) pre-briefing and completion of a multi-choice question test, (ii) three video-recorded simulated clinical scenarios where actors substituted real patients with deteriorating conditions, and (iii) post-scenario debriefing. Clinical performance, teamwork and situation awareness were evaluated, using a validated standard checklist (OSCE), Team Emergency Assessment Measure (TEAM) score sheet and Situation Awareness Global Assessment Technique (SAGAT). A Modified Angoff technique was used to establish cut points for clinical performance.

Results
Student teams engaged in 97 simulation experiences across the three scenarios and achieved a level of clinical performance consistent with the experts' identified pass level point in only 9 (1%) of the simulation experiences. Knowledge was significantly associated with overall teamwork (p = .034), overall situation awareness (p = .05) and clinical performance in two of the three scenarios (p = .032 cardiac and p = .006 shock). Situation awareness scores of scenario team leaders were low overall, with an average total score of 41%.

Conclusions
Final year undergraduate nursing students may have difficulty recognising and responding appropriately to patient deterioration. Improving pre-requisite knowledge, rehearsal of first response and team management strategies need to be a key component of undergraduate nursing students' education and ought to specifically address clinical performance, teamwork and situation awareness.