The power of optogenetics : Potential in cardiac experimental and clinical electrophysiology

Optogenetics is an emerging, interdisciplinary research area which combines genetic and optical technologies to steer and monitor specific biological processes. To this end, light-activated proteins, so-called optogenetic actuators, or fluorescent sensor proteins are genetically targeted to the cells of interest. Light activation can then be used to modulate or record cellular behaviour with high spatiotemporal precision. In cardiac research, optogenetic approaches have been used to unravel heterocellular electrotonic interactions, both in vitro and in situ. Pioneering optogenetic studies with potential relevance for clinical electrophysiology include light-controlled pacing experiments and optical defibrillation studies. However, despite successful implementation in mouse models, clinical applications are not feasible to date; these will require major advances in gene therapy and in optical techniques.

Implantable epicardial cardioverter-defibrillator-induced localized constrictive pericarditis

In the 1990s, epicardial implantable cardioverter-defibrillator (ICD) patches were frequently implanted to treat life-threatening ventricular arrhythmia. However, owing to the high rates of functional failure, the patch system has been replaced by transvenous ICD leads system. Although morphological abnormalities such as dense fibrosis around the patch are quite frequent, epicardial ICD patch-induced localized constrictive pericarditis is very rare. We encountered a patient who had severe heart failure due to constrictive pericarditis, 23 years after the implantation of epicardial ICD patches. The heart failure was treated after complete resection of the patches and dense fibrosis on the surface of both the right and the left ventricles. To our knowledge, this is the first report on the treatment of epicardial ICD patch-induced localized constrictive pericarditis.

Public Access Defibrillation: Is This Making Any Difference? Controversial Issues in Resuscitation from Cardiac Arrest

Public access defibrillation is particularly valuable in witnessed cardiac arrests that occur in public places. Bystander and police use of automated external defibrillators (AEDs) has increased over the past 15 years, resulting in improved survival with normal or near-normal neurologic function. There is great promise for increasing bystander use of defibrillators as the technology is applied to linking patients with shockable arrests to volunteers committed to bringing AEDs to the patients. There continues to be controversy as to the value of epinephrine, antiarrhythmic drugs, hypothermia, and mechanical chest compression in resuscitative efforts.

Interaction of defibrillation waveform with the time to defibrillation or the number of defibrillation attempts on survival from out-of-hospital cardiac arrest

AIM

Early biphasic defibrillation is effective in out-of-hospital cardiac arrest (OHCA) cases. In the resuscitation of patients with OHCA, it is not clear how the defibrillation waveform interacts with the time to defibrillation to influence patient survival. The second, and any subsequent, shocks need to be administered by an on-line physician in Japan. Thus, we investigated the interaction between the defibrillation waveform and time to or the number of defibrillation on resuscitation outcomes.

METHODS

This prospective observational study used data for all OHCAs that occurred between 2005 and 2014 in Japan. To investigate the interaction effect between the defibrillation waveform and the time to defibrillation or the number of defibrillations on the return to spontaneous circulation (ROSC), 1-month survival, and cerebral performance category (CPC) (1, 2), we assessed the modifying effects of the defibrillation waveform and the time to or the number of defibrillation on additive scale (i.e., the relative excessive risk due to interaction, RERI) and multiplicative scale (i.e., ratio of odds ratios (ORs)).

RESULTS

In total, 71,566 cases met the inclusion criteria. For the measure of interaction between the defibrillation waveform and the time to defibrillation, ratio of ORs for ROSC was 0.84 (0.75-0.94), implying that the effect of time to first defibrillation on ROSC was negatively modified by defibrillation waveform. For the interaction between the defibrillation waveform and the number of defibrillations, RERI and ratio of ORs for CPC (1, 2) was -0.25 (-0.47 to -0.06) and 0.79 (0.67-0.93), respectively. It is implied that the effect of number of defibrillation on CPC (1, 2) was negatively modified by defibrillation waveform.

CONCLUSIONS

An increased number of defibrillations was associated with a decreased ROSC in the case of biphasic and monophasic defibrillation, while an increased number of defibrillations was related to an increased 1-month survival rate and CPC (1, 2) only in the case of biphasic defibrillation. When two or more defibrillations were performed, a biphasic waveform was more effective in terms of long-term survival than a monophasic waveform.

Automated external defibrillators in the hospital: A case of medical reversal

Automated external defibrillators (AEDs) emerged in the 1980s as an important innovation in pre-hospital emergency cardiac care (ECC). In the years since, the American Heart Association (AHA) and the International Liaison Committee for Resuscitation (ILCOR) have promoted AED technology for use in hospitals as well, resulting in the widespread purchase and use of AED-capable defibrillators. In-hospital use of AEDs now appears to have decreased survival from cardiac arrests. This article will look at the use of AEDs in hospitals as a case of "medical reversal." Medical reversal occurs when an accepted, widely used treatment is found to be ineffective or even harmful. This article will discuss the issue of AEDs in the hospital using a conceptual framework provided by recent work on medical reversal. It will go on to consider the implications of the reversal for in-hospital resuscitation programs and emergency medicine more generally.

Nocturnal phantom shock cessation with zolpidem

A 77 year old man with a biventricular ICD-pacemaker complained of painful, electric jolts disturbing him nightly from sleep. Extensive work-up including device interrogation revealed no defibrillations or arrhythmia, and he was subsequently diagnosed with phantom shocks (PS). His nightly PS symptoms terminated after starting zolpidem 10 mg each night. To date, literature review reveals fifteen articles reporting 163 phantom shock (PS) cases. PS affects 5-9% of ICD recipients. Risk factors include psychiatric disease, atrial fibrillation, NYHA functional status III or greater, prior shock storm, and intraoperative awareness during ICD placement, with defibrillation threshold testing. This report describes a successful PS intervention, and reviews the current knowledge available in the pathophysiology and treatment of PS.

Sensitivity and specificity of two different automated external defibrillators

AIM

The aim was to investigate the clinical performance of two different types of automated external defibrillators (AEDs).

METHODS

Three investigators reviewed 2938 rhythm analyses performed by AEDs in 240 consecutive patients (median age 72, q1-q3=62-83) who had suffered cardiac arrest between January 2011 and March 2015. Two different AEDs were used (AED A n=105, AED B n=135) in-hospital (n=91) and out-of-hospital (n=149).

RESULTS

Among 194 shockable rhythms, 17 (8.8%) were not recognized by AED A, while AED B recognized 100% (n=135) of shockable episodes (sensitivity 91.2 vs 100%, p<0.01). In AED A, 8 (47.1%) of these episodes were judged to be algorithm errors while 9 (52.9%) were caused by external artifacts. Among 1039 non-shockable rhythms, AED A recommended shock in 11 (1.0%), while AED B recommended shock in 63 (4.1%) of 1523 episodes (specificity 98.9 vs 95.9, p<0.001). In AED A, 2 (18.2%) of these episodes were judged to be algorithm errors (AED B, n=40, 63.5%), while 9 (81.8%) were caused by external artifacts (AED B, n=23, 36.5%).

CONCLUSIONS

There were significant differences in sensitivity and specificity between the two different AEDs. A higher sensitivity of AED B was associated with a lower specificity while a higher specificity of AED A was associated with a lower sensitivity. AED manufacturers should work to improve the algorithms. In addition, AED use should always be reviewed with a routine for giving feedback, and medical personnel should be aware of the specific strengths and shortcomings of the device they are using.

Ventricular fibrillation waveform measures combined with prior shock outcome predict defibrillation success during cardiopulmonary resuscitation

AIM

Amplitude Spectrum Area (AMSA) and Median Slope (MS) are ventricular fibrillation (VF) waveform measures that predict defibrillation shock success. Cardiopulmonary resuscitation (CPR) obscures electrocardiograms and must be paused for analysis. Studies suggest waveform measures better predict subsequent shock success when combined with prior shock success. We determined whether this relationship applies during CPR.

METHODS

AMSA and MS were calculated from 5-second pre-shock segments with and without CPR, and compared to logistic models combining each measure with prior return of organized rhythm (ROR).

RESULTS

VF segments from 692 patients were analyzed during CPR before 1372 shocks and without CPR before 1283 shocks. Combining waveform measures with prior ROR increased areas under receiver operating characteristic curves for AMSA/MS with CPR (0.66/0.68 to 0.73/0.74, p<0.001) and without CPR (0.71/0.72 to 0.76/0.76, p<0.001).

CONCLUSIONS

Prior ROR improves prediction of shock success during CPR, and may enable waveform measure calculation without chest compression pauses.

Cardiopulmonary resuscitation by trained responders versus lay persons and outcomes of out-of-hospital cardiac arrest: A community observational study

OBJECTIVES

The study aims to compare bystander processes of care (cardiopulmonary resuscitation (CPR) and defibrillation) and outcomes for witnessed presumed cardiac etiology in OHCA patients in whom initial resuscitation was provided by dedicated trained responder (TR) versus lay person (LP) bystanders.

METHODS

Data on witnessed and presumed cardiac OHCA in adults (15 years or older) from 2011 to 2015 in a metropolitan city with 10 million persons were collected, excluding cases in which the information on TRs, bystander CPR, defibrillation, and clinical outcomes was unknown. Exposure variables were TRs who were legally designated with CPR education and response and LPs who were bystanders who witnessed the OHCA by chance. The primary/secondary/tertiary outcomes were a good cerebral performance category (CPC) of 1 or 2, survival to discharge, and bystander defibrillation. A multivariable logistic regression analysis was used to calculate the adjusted odds ratio (AOR) with 95% confidence intervals (CIs), adjusting for potential confounders.

RESULTS

Of 20,984 OHCA events, 6475 cases were ultimately analyzed. The TR group constituted 6.4% of the cases, and the patients showed significantly better survival and a good CPC. From the multivariable logistic regression analysis of the outcomes, by comparing the TR group with the LP group, the AOR (95% CIs) was 1.49 (1.04-2.15) for a good CPC, 1.59 (1.20-2.11) for survival to discharge, and 10.02 (7.04-14.26) for bystander defibrillation.

CONCLUSION

The TR group witnessed a relatively low proportion of OHCA but was associated with better survival outcomes and good neurological recovery through higher CPR rates and defibrillation of adults older than 15 years with witnessed OHCA in a metropolitan city.

Double sequential defibrillation therapy for out-of-hospital cardiac arrests: The London experience

BACKGROUND

Despite advances in treatment for out-of-hospital cardiac arrest (OHCA), a subgroup of patients remain in refractory ventricular fibrillation (RVF) during resuscitation. Recent evidence suggests that double sequential defibrillation (DSD), where two shocks are delivered to the patient in quick succession, may provide an effective therapy for RVF. This study describes the characteristics and survival outcomes of OHCA patients treated by ambulance clinicians using a local DSD protocol in an attempt to resolve RVF.

METHODS

This is a retrospective, observational analysis of patients who received DSD by the London Ambulance Service from 1st July 2015 to 31st December 2016. A comparator group of patients who received more than six consecutive standard shocks (not DSD) for persistent VF was also identified. Outcomes included pre-hospital return of spontaneous circulation (ROSC), ROSC sustained to hospital, and survival to hospital discharge. DSD patients who survived to hospital discharge are reported in further detail.

RESULTS

During the 18-month study period, 45 patients were treated with DSD: a third obtained a pre-hospital ROSC and 7% survived to hospital discharge. We observed similar ROSC and survival rates amongst those who received standard defibrillation only.

CONCLUSION

Our observational study did not find any clear benefit of DSD use by EMS in the treatment of RVF. However, we find that 3 patients, who were treated with DSD following unsuccessful single shocks, had their VF terminated. Prospective randomised clinical trials are urgently needed to investigate the potential value of DSD in the pre-hospital setting.

Automated external defibrillator and operator performance in out-of-hospital cardiac arrest

AIM

An increasing number of failing automated external defibrillators (AEDs) is reported: AEDs not giving a shock or other malfunction. We assessed to what extent AEDs are 'failing' and whether this had a device-related or operator-related cause.

METHODS

We studied analysis periods from AEDs used between January 2012 and December 2014. For each analysis period we assessed the correctness of the (no)-shock advice (sensitivity/specificity) and reasons for an incorrect (no)-shock advice. If no shock was delivered after a shock advice, we assessed the reason for no-shock delivery.

RESULTS

We analyzed 1114 AED recordings with 3310 analysis periods (1091 shock advices; 2219 no-shock advices). Sensitivity for coarse ventricular fibrillation was 99% and specificity for non-shockable rhythm detection 98%. The AED gave an incorrect shock advice in 4% (44/1091) of all shock advices, due to device-related (n=15) and operator-related errors (n=28) (one unknown). Of these 44 shock advices, only 2 shocks caused a rhythm change. One percent (26/2219) of all no-shock advices was incorrect due to device-related (n=20) and operator-related errors (n=6). In 5% (59/1091) of all shock advices, no shock was delivered: operator failed to deliver shock (n=33), AED was removed (n=17), operator pushed 'off' button (n=8) and other (n=1). Of the 1073 analysis periods with a shockable rhythm, 67 (6%) did not receive an AED shock.

CONCLUSION

Errors associated with AED use are rare (4%) and when occurring are in 72% caused by the operator or circumstances of use. Fully automatic AEDs may prevent the majority of these errors.

Fatal monomorphic ventricular tachycardia in a semi-urban setting in Cameroon: a case report

Background

Ventricular tachycardia is a life threatening cardiac arrhythmia. It needs management with defibrillation, without which, immediate death may occur.

Case presentation

A 66 year old black African patient with a 2 year history of hypertension was admitted to the emergency department of the Buea Regional hospital, a semi-urban setting in Cameroon, after presenting with syncope while in church. The wife described a similar episode 2 weeks prior without any further evaluation. Upon arrival at the emergency, patient had regained consciousness but lethargic, tachypneic and diaphoretic. The blood pressure was 85/61 mmHg; the pulse was 219/min, weak and thready. He had cold extremities. A 12 lead electrocardiogram performed showed a sustained monomorphic ventricular tachycardia at 230/min. He was administered six tablets of amiodarone, oxygen by nasal cannula and intravenous fluids. No electrical cardioversion was attempted due to the non availability of a defibrillator. Outcome was fatal with death of the patient 30 min after his arrival to the emergency.

Conclusion

Our health facilities should be well equipped for resuscitative measures by adopting Advanced Cardiac Life Support as cardiovascular diseases are becoming more frequent in our settings.

Features of hospital and emergency medical service in out-of-hospital cardiac arrest patients with shockable rhythm

OBJECTIVE

Predicting the outcome of out-of-hospital cardiac arrest (OHCA) patients is crucial. We examined hospital characteristics and parameters of emergency medical service (including scene time interval and direct ambulance delivery to intensive heart hospitals) as survival or outcome predictors.

STUDY DESIGN

Data from 546 consecutive OHCA shockable patients treated between January 2012 and December 2015 in Taoyuan City (Taiwan, ROC) were collected. In addition to demographic data, location of arrest, initial rhythm, availability of a hospital with or without 24/7 percutaneous coronary intervention (PCI), emergency medical service (EMS) time, provision of cardiopulmonary resuscitation by a bystander, presence of a witness at collapse, and level of life support were analysed.

RESULTS

Multivariate analysis showed that hospitalisation with immediate PCI availability was an independent predictor (OR: 4.32; 95% CI: 1.27-14.70) solely for the outcome of survival until discharge. The presence of a witness while collapsing (OR: 3.52; 95% CI: 1.03-11.98), EMS response time (OR: 0.83; 95% CI: 0.70-0.98), and scene time interval (STI; OR: 0.89; 95% CI: 0.81-0.99) were valuable for predicting the neurological outcome.

CONCLUSIONS

Direct ambulance delivery to intensive heart hospitals that had 24/7 PCI availability was associated with a higher probability of surviving until discharge in OHCA patients with shockable rhythms. Similarly, a witnessed collapse was correlated with being discharged alive from hospital and recovering with good cerebral performance. In addition, longer response time and scene time interval indicated poorer survival and neurological outcome.

Survival in ventricular fibrillation with emphasis on the number of defibrillations in relation to other factors at resuscitation

INTRODUCTION

Mortality after out of hospital cardiac arrest (OHCA) is high and a shockable rhythm is a key predictor of survival. A concomitant need for repeated shocks appears to be associated with less favorable outcome.

AIM

To, among patients found in ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) describe: (a) factors associated with 30-day survival with emphasis on the number of defibrillatory shocks delivered; (b) the distribution of and the characteristics of patients in relation to the number of defibrillatory shocks that were delivered.

METHODS

Patients who were reported to The Swedish Register for Cardiopulmonary Resuscitation (SRCR) between January 1 1990 and December 31 2015 and who were found in VF/pVT took part in the survey.

RESULTS

In all there were 19,519 patients found in VF/pVT. The 30-day survival decreased with an increasing number of shocks among all patients regardless of witnessed status and regardless of time period in the survey. In a multivariate analysis there were 12 factors that were associated with the chance of 30-day survival one of which was the number of shocks that was delivered. For each shock that was added the chance of survival decreased. Factors associated with an increased 30-day survival included CPR before arrival of EMS, female sex, cardiac etiology and year of OHCA (increasing survival over years). Factors associated with a decreased chance of 30-day survival included: increasing age, OHCA at home, the use of adrenaline and intubation and an increased delay to CPR, defibrillation and EMS arrival.

CONCLUSION

Among patients found in VF/pVT, 7.5% required more than 10 shocks. For each shock that was added the chance of 30-day survival decreased. There was an increase in 30-day survival over time regardless of the number of shocks. On top of the number of defibrillations, eleven further factors were associated with 30-day survival.

Novel CPR system that predicts return of spontaneous circulation from amplitude spectral area before electric shock in ventricular fibrillation

AIM

Amplitude spectral area (AMSA), an index for analysing ventricular fibrillation (VF) waveforms, is thought to predict the return of spontaneous circulation (ROSC) after electric shocks, but its validity is unconfirmed. We developed an equation to predict ROSC, where the change in AMSA (ΔAMSA) is added to AMSA measured immediately before the first shock (AMSA1). We examine the validity of this equation by comparing it with the conventional AMSA1-only equation.

METHOD

We retrospectively investigated 285 VF patients given prehospital electric shocks by emergency medical services. ΔAMSA was calculated by subtracting AMSA1 from last AMSA immediately before the last prehospital electric shock. Multivariate logistic regression analysis was performed using post-shock ROSC as a dependent variable.

RESULTS

Analysis data were subjected to receiver operating characteristic curve analysis, goodness-of-fit testing using a likelihood ratio test, and the bootstrap method. AMSA1 (odds ratio (OR) 1.151, 95% confidence interval (CI) 1.086-1.220) and ΔAMSA (OR 1.289, 95% CI 1.156-1.438) were independent factors influencing ROSC induction by electric shock. Area under the curve (AUC) for predicting ROSC was 0.851 for AMSA1-only and 0.891 for AMSA1+ΔAMSA. Compared with the AMSA1-only equation, the AMSA1+ΔAMSA equation had significantly better goodness-of-fit (likelihood ratio test P<0.001) and showed good fit in the bootstrap method.

CONCLUSIONS

Post-shock ROSC was accurately predicted by adding ΔAMSA to AMSA1. AMSA-based ROSC prediction enables application of electric shock to only those patients with high probability of ROSC, instead of interrupting chest compressions and delivering unnecessary shocks to patients with low probability of ROSC.

Incidence and survival outcome according to heart rhythm during resuscitation attempt in out-of-hospital cardiac arrest patients with presumed cardiac etiology

BACKGROUND

Knowledge about heart rhythm conversion from non-shockable to shockable rhythm during resuscitation attempt after out-of-hospital cardiac arrest (OHCA) and following chance of survival is limited and inconsistent.

METHODS

We studied 13,860 patients with presumed cardiac-caused OHCA not witnessed by the emergency medical services from the Danish Cardiac Arrest Register (2005-2012). Patients were stratified according to rhythm: shockable, converted shockable (based on receipt of subsequent defibrillation) and sustained non-shockable rhythm. Multiple logistic regression was used to identify predictors of rhythm conversion and to compute 30-day survival chances.

RESULTS

Twenty-five percent of patients who received pre-hospital defibrillation by ambulance personnel were initially found in non-shockable rhythms. Younger age, males, witnessed arrest, shorter response time, and heart disease were significantly associated with conversion to shockable rhythm, while psychiatric- and chronic obstructive pulmonary disease were significantly associated with sustained non-shockable rhythm. Compared to sustained non-shockable rhythms, converted shockable rhythms and initial shockable rhythms were significantly associated with increased 30-day survival (Adjusted odds ratio (OR) 2.6, 95% confidence interval (CI): 1.8-3.8; and OR 16.4, 95% CI 12.7-21.2, respectively). From 2005 to 2012, 30-day survival chances increased significantly for all three groups: shockable rhythms, from 16.3% (CI: 14.2%-18.7%) to 35.7% (CI: 32.5%-38.9%); converted rhythms, from 2.1% (CI: 1.6%-2.9%) to 5.8% (CI: 4.4%-7.6%); and sustained non-shockable rhythms, from 0.6% (CI: 0.5%-0.8%) to 1.8% (CI: 1.4%-2.2%).

CONCLUSION

Converting to shockable rhythm during resuscitation attempt was common and associated with nearly a three-fold higher odds of 30-day survival compared to sustained non-shockable rhythms.

[Implementation of regularly performed resuscitation training at a hyperbaric treatment center]

BACKGROUND

Medical emergency situations and even cardiac arrest can occur during treatment of patients in therapeutic hyperbaric chambers just as in other clinical departments; therefore, high quality structured management should be implemented for dealing with emergencies in this special working area. To ensure this the emergency medical treatment should not only be performed according to the current state of medical knowledge but needs to take the special features of the hyperbaric environment including safety aspects into account.

METHOD

This article presents a description of the implementation and effects of routine emergency and resuscitation training at a center for hyperbaric medicine.

RESULTS

By simulation of emergencies in a hyperbaric chamber it rapidly became clear that the treatment of medical emergencies and cardiac arrest under hyperbaric conditions has some special features and due to safety aspects cannot always be performed according to current medical guidelines. At the time of this simulation in a real life working environment, previously unknown structural and logistic problems became obvious whereby the solutions contributed to a significant improvement of structural and process quality and could potentially also improve the outcome quality. Furthermore, a positive and lasting learning effect in the fields of quality of resuscitation measures, organization of the workplace, communication skills, logistics and safety aspects was detectable by analyzing participant performance over a period of 4 years. On the part of the participating staff a positive feedback and high acceptance of emergency simulator training was confirmed.

CONCLUSION

Through annual compulsory emergency training of the complete staff of the hyperbaric unit at the actual workplace, a structural and confident approach to dealing with emergencies and resuscitation situations was observed. By the use of on-site simulator training even in specialized hospital units, deficits and tentativeness regarding logistics, course of action, organization and communication in emergency situations can be minimized to provide optimum patient care in a real life emergency situation by focusing on the medical measures.

Unmanned aerial vehicles (drones) in out-of-hospital-cardiac-arrest

Background

The use of an automated external defibrillator (AED) prior to EMS arrival can increase 30-day survival in out-of-hospital cardiac arrest (OHCA) significantly. Drones or unmanned aerial vehicles (UAV) can fly with high velocity and potentially transport devices such as AEDs to the site of OHCAs. The aim of this explorative study was to investigate the feasibility of a drone system in decreasing response time and delivering an AED.

Methods

Data of Global Positioning System (GPS) coordinates from historical OHCA in Stockholm County was used in a model using a Geographic Information System (GIS) to find suitable placements and visualize response times for the use of an AED equipped drone. Two different geographical models, urban and rural, were calculated using a multi-criteria evaluation (MCE) model. Test-flights with an AED were performed on these locations in rural areas.

Results

In total, based on 3,165 retrospective OHCAs in Stockholm County between 2006–2013, twenty locations were identified for the potential placement of a drone.

In a GIS-simulated model of urban OHCA, the drone arrived before EMS in 32 % of cases, and the mean amount of time saved was 1.5 min. In rural OHCA the drone arrived before EMS in 93 % of cases with a mean amount of time saved of 19 min. In these rural locations during (n = 13) test flights, latch-release of the AED from low altitude (3–4 m) or landing the drone on flat ground were the safest ways to deliver an AED to the bystander and were superior to parachute release.

Discussion

The difference in response time for EMS between urban and rural areas is substantial, as is the possible amount of time saved using this UAV-system. However, yet another technical device needs to fit into the chain of survival. We know nothing of how productive or even counterproductive this system might be in clinical reality.

Conclusions

To use drones in rural areas to deliver an AED in OHCA may be safe and feasible. Suitable placement of drone systems can be designed by using GIS models. The use of an AED equipped drone may have the potential to reduce time to defibrillation in OHCA.

Short ECG segments predict defibrillation outcome using quantitative waveform measures

AIM

Quantitative waveform measures of the ventricular fibrillation (VF) electrocardiogram (ECG) predict defibrillation outcome. Calculation requires an ECG epoch without chest compression artifact. However, pauses in CPR can adversely affect survival. Thus the potential use of waveform measures is limited by the need to pause CPR. We sought to characterize the relationship between the length of the CPR-free epoch and the ability to predict outcome.

METHODS

We conducted a retrospective investigation using the CPR-free ECG prior to first shock among out-of-hospital VF cardiac arrest patients in a large metropolitan region (n=442). Amplitude Spectrum Area (AMSA) and Median Slope (MS) were calculated using ECG epochs ranging from 5s to 0.2s. The relative ability of the measures to predict return of organized rhythm (ROR) and neurologically-intact survival was evaluated at different epoch lengths by calculating the area under the receiver operating characteristic curve (AUC) using the 5-s epoch as the referent group.

RESULTS

Compared to the 5-s epoch, AMSA performance declined significantly only after reducing epoch length to 0.2s for ROR (AUC 0.77-0.74, p=0.03) and with epochs of ≤0.6s for neurologically-intact survival (AUC 0.72-0.70, p=0.04). MS performance declined significantly with epochs of ≤0.8s for ROR (AUC 0.78-0.77, p=0.04) and with epochs ≤1.6s for neurologically-intact survival (AUC 0.72-0.71, p=0.04).

CONCLUSION

Waveform measures predict defibrillation outcome using very brief ECG epochs, a quality that may enable their use in current resuscitation algorithms designed to limit CPR interruption.

Age-specific differences in prognostic significance of rhythm conversion from initial non-shockable to shockable rhythm and subsequent shock delivery in out-of-hospital cardiac arrest

BACKGROUND

Early rhythm conversion from an initial non-shockable to a shockable rhythm and subsequent shock delivery in patients with out-of-hospital cardiac arrest (OHCA) has been associated with favourable neurological outcome (Cerebral Performance Category score 1 or 2; CPC 1-2). We hypothesized that the prognostic significance of rhythm conversion and subsequent shock delivery differs by age and time from initiation of cardiopulmonary resuscitation (CPR) by emergency medical service (EMS) providers to first defibrillation (shock delivery time).

METHODS

We analysed 430,443 OHCA patients with an initial non-shockable rhythm using a prospective Japanese Utstein-style database from 2011 to 2014. The primary endpoint was 1-month CPC 1-2.

RESULTS

Multivariate logistic regression revealed that rhythm conversion and subsequent shock delivery is positively associated with 1-month CPC 1-2: the adjusted odds ratio was 6.09 (95% confidence interval: 3.65-9.75) for shock delivery time <10min and 3.34 (2.58-4.27) for 10-19min in patients aged 18-64 years, and 3.16 (1.45-6.09) for <10min and 2.17 (1.51-3.03) for 10-19min in patients aged 65-74 years. However, it is negatively associated with 1-month CPC 1-2 for shock delivery time of 20-59min in patients aged 75-84 years (0.55; 0.27-0.98) and ≥85 years (0.17; 0.03-0.53).

CONCLUSIONS

Early rhythm conversion from an initial non-shockable to a shockable rhythm and subsequent shock delivery is associated with increased odds of 1-month CPC 1-2 in OHCA patients aged 18-74 years but not in those aged ≥75 years.

Use of double sequential external defibrillation for refractory ventricular fibrillation during out-of-hospital cardiac arrest

INTRODUCTION

Survival from out of hospital cardiac arrest (OHCA) is highest in victims with shockable rhythms when early CPR and rapid defibrillation are provided. However, a subset of individuals present with ventricular fibrillation (VF) that does not respond to defibrillation (refractory VF). One intervention that may be a possible option in refractory VF is double sequential external defibrillation (DSD). The objective of this case series was to describe the outcome of prehospital victims with refractory VF treated with DSD in the out-of-hospital setting.

METHODS

This evaluation is a retrospective chart review of VF patients treated with DSD in the prehospital setting from August 1st, 2010 through June 30th, 2014. Patients were excluded if less than 17 years of age. The outcomes we evaluated were the number of patients with return of spontaneous circulation, conversion from VF, survival-to-hospital discharge, and Cerebral Performance Category score.

RESULTS

Total of 2428 OHCA events were reviewed with twelve patients treated with DSD. Median DSD and prehospital resuscitation times were 27min (IQR 22-33) and 32 (IQR 24-38), respectively. Of the 12 patients treated, return of spontaneous circulation was achieved in three patients, nine patients were converted out of ventricular fibrillation, three patients survived to hospital discharge, and two patients (2/12, 17%) were discharged with Cerebral Performance Category scores of 1 (good cerebral performance).

CONCLUSIONS

Double sequential defibrillation may be another tool to improve neurologically intact survival from OHCA. Further studies are needed to demonstrate direct benefits to patient outcomes.

Computational rabbit models to investigate the initiation, perpetuation, and termination of ventricular arrhythmia

Current understanding of cardiac electrophysiology has been greatly aided by computational work performed using rabbit ventricular models. This article reviews the contributions of multiscale models of rabbit ventricles in understanding cardiac arrhythmia mechanisms. This review will provide an overview of multiscale modeling of the rabbit ventricles. It will then highlight works that provide insights into the role of the conduction system, complex geometric structures, and heterogeneous cellular electrophysiology in diseased and healthy rabbit hearts to the initiation and maintenance of ventricular arrhythmia. Finally, it will provide an overview on the contributions of rabbit ventricular modeling on understanding the mechanisms underlying shock-induced defibrillation.

Management of Patients With Cardiovascular Implantable Electronic Devices in Dental, Oral, and Maxillofacial Surgery

The prevalence of cardiovascular implantable electronic devices as life-prolonging and life-saving devices has evolved from a treatment of last resort to a first-line therapy for an increasing number of patients. As these devices become more and more popular in the general population, dental providers utilizing instruments and medications should be aware of dental equipment and medications that may affect these devices and understand the management of patients with these devices. This review article will discuss the various types and indications for pacemakers and implantable cardioverter-defibrillators, common drugs and instruments affecting these devices, and management of patients with these devices implanted for cardiac dysrhythmias.