Jennifer Blackwood

Impact of Changes in Resuscitation Practice on Survival and Neurological Outcome After Out-of-Hospital Cardiac Arrest Resulting From Nonshockable Arrhythmias

Background— Out-of-hospital cardiac arrest (OHCA) claims millions of lives worldwide each year. OHCA survival from shockable arrhythmias (ventricular fibrillation/ tachycardia) improved in several communities after implementation of American Heart Association resuscitation guidelines that eliminated “stacked” shocks and emphasized chest compressions. “Nonshockable” rhythms are now the predominant presentation of OHCA; the benefit of such treatments on nonshockable rhythms is uncertain. Methods and Results— We studied 3960 patients with nontraumatic OHCA from nonshockable initial rhythms treated by prehospital providers in King County, Washington, over a 10-year period. Outcomes during a 5-year intervention period after adoption of new resuscitation guidelines were compared with the previous 5-year historical control period. The primary outcome was 1-year survival. Patient demographics and resuscitation characteristics were similar between the control (n=1774) and intervention (n=2186) groups, among whom 471 of 1774 patients (27%) versus 742 of 2186 patients (34%), respectively, achieved return of spontaneous circulation; 82 (4.6%) versus 149 (6.8%) were discharged from hospital, 60 (3.4%) versus 112 (5.1%) with favorable neurological outcome; 73 (4.1%) versus 135 (6.2%) survived 1 month; and 48 (2.7%) versus 106 patients (4.9%) survived 1 year (all P⩽0.005). After adjustment for potential confounders, the intervention period was associated with an improved odds of 1.50 (95% confidence interval, 1.29–1.74) for return of spontaneous circulation, 1.53 (95% confidence interval, 1.14–2.05) for hospital survival, 1.56 (95% confidence interval, 1.11–2.18) for favorable neurological status, 1.54 (95% confidence interval, 1.14–2.10) for 1-month survival, and 1.85 (95% confidence interval, 1.29–2.66) for 1-year survival. Conclusion— Outcomes from OHCA resulting from nonshockable rhythms, although poor by comparison with shockable rhythm presentations, improved significantly after implementation of resuscitation guideline changes, suggesting their potential to benefit all presentations of OHCA.

Course of quantitative ventricular fibrillation waveform measure and outcome following out-of-hospital cardiac arrest

BACKGROUND Quantitative measures of the ventricular fibrillation waveform at the outset of resuscitation are associated with survival. However, little is known about the course of these measures during resuscitation and how this course is related to outcome. OBJECTIVE The purpose of this study was to determine how waveform measures change over the course of resuscitation and whether these changes might be used to guide resuscitation. METHODS We evaluated 390 persons treated by emergency providers following out-of-hospital ventricular fibrillation arrest. We assessed the ventricular fibrillation waveform using the amplitude spectrum area (AMSA) from the defibrillators continuous electrocardiogram measured before each of the first three shocks. We used logistic regression to evaluate the relationship of AMSA and the change in AMSA with favorable neurologic survival as determined by the Cerebral Performance Category at hospital discharge 1-2. RESULTS Of the 390 patients who received an initial shock, 273 required a second shock and 210 required a third shock. The mean (standard deviation) for AMSA was 9.64 (0.52) for the 873 total shock cycles. AMSA₁ measured before the first shock was strongly associated with favorable neurologic survival (odds ratio [OR] 3.40, 95% confidence interval [CI] [2.48, 4.66] for 1 SD change). We observed a similar relationship for second-shock AMSA₂ (OR 3.53, 95% CI [2.42, 5.14]) and third-shock AMSA₃ (OR 3.10, 95% CI [2.03, 4.73]). The median change in AMSA was 0.24 for ΔAMSA₁₋₂ and 0.21 for ΔAMSA₂₋₃. A positive median change in AMSA between shocks was associated with favorable neurologic survival (OR 1.44, 95% CI [1.16, 1.80] for ΔAMSA₁₋₂ and OR 1.31, 95% CI [1.01, 1.71] for ΔAMSA₂₋₃). CONCLUSION Given their prognostic and dynamic qualities, quantitative waveform measures may provide an effective real-time strategy to guide individual treatment and improve survival.

Cardiopulmonary resuscitation duty cycle in out-of-hospital cardiac arrest.

BACKGROUND Duty cycle is the portion of time spent in compression relative to total time of the compression-decompression cycle. Guidelines recommend a 50% duty cycle based largely on animal investigation. We undertook a descriptive evaluation of duty cycle in human resuscitation, and whether duty cycle correlates with other CPR measures. METHODS We calculated the duty cycle, compression depth, and compression rate during EMS resuscitation of 164 patients with out-of-hospital ventricular fibrillation cardiac arrest. We captured force recordings from a chest accelerometer to measure ten-second CPR epochs that preceded rhythm analysis. Duty cycle was calculated using two methods. Effective compression time (ECT) is the time from beginning to end of compression divided by total period for that compression-decompression cycle. Area duty cycle (ADC) is the ratio of area under the force curve divided by total area of one compression-decompression cycle. We evaluated the compression depth and compression rate according to duty cycle quartiles. RESULTS There were 369 ten-second epochs among 164 patients. The median duty cycle was 38.8% (SD=5.5%) using ECT and 32.2% (SD=4.3%) using ADC. A relatively shorter compression phase (lower duty cycle) was associated with greater compression depth (test for trend <0.05 for ECT and ADC) and slower compression rate (test for trend <0.05 for ADC). Sixty-one of 164 patients (37%) survived to hospital discharge. CONCLUSIONS Duty cycle was below the 50% recommended guideline, and was associated with compression depth and rate. These findings provider rationale to incorporate duty cycle into research aimed at understanding optimal CPR metrics.

Strategy to Address Private Location Cardiac Arrest: A Public Safety Survey

Abstract Objective: Most cardiac arrests occur in the private setting where response is often delayed and outcomes are poor. We surveyed public safety personnel to determine if they would volunteer to respond into private locations and/or be equipped with a personal automated external defibrillator (AED) as part of a vetted responder program that would use smart geospatial technology. Methods: We conducted an anonymized survey among personnel from fire-based emergency medical services (EMS) and search and rescue organizations from Washington State. The goal of the survey was to evaluate whether there was interest among cardiopulmonary resuscitation (CPR)-trained, public safety personnel to respond with or without an AED to private-residence cardiac arrest outside of working hours using a smartphone platform. We used a 5-point Likert scale to assess responses. Results: Overall the response rate was 73.7% (527/715). Two-thirds of respondents were between the ages of 30–59 with a similar proportion certified as a firefighter–emergency medical technician (EMT). Most were male (80%). As a vetted volunteer responder, the majority would “almost always” or “often” respond to private (79.7%) or public locations (85.2%) outside of work hours. The majority (54.1%) would store the AED in their vehicle while 38% would plan to keep the AED on their person. A total of 83% were “definitely’ or “probably interested” in participating in the program. Conclusion: The results of this survey indicate that public safety personnel are willing to respond to suspected cardiac arrest during off-hours using geospatial smart technology to private locations with or without an AED.

Ventricular fibrillation waveform measures and the etiology of cardiac arrest.

BACKGROUND Early determination of the acute etiology of cardiac arrest could help guide resuscitation or post-resuscitation care. In experimental studies, quantitative measures of the ventricular fibrillation waveform distinguish ischemic from non-ischemic etiology. METHODS We investigated whether waveform measures distinguished arrest etiology among adults treated by EMS for out-of-hospital ventricular fibrillation between January 1, 2006-December 31, 2014. Etiology was classified using hospital information into three exclusive groups: acute coronary syndrome (ACS) with ST elevation myocardial infarction (STEMI), ACS without ST elevation (non-STEMI), or non-ischemic arrest. Waveform measures included amplitude spectrum area (AMSA), centroid frequency (CF), mean frequency (MF), and median slope (MS) assessed during CPR-free epochs immediately prior to the initial and second shock. Waveform measures prior to the initial shock and the changes between first and second shock were compared by etiology group. We a priori chose a significance level of 0.01 due to multiple comparisons. RESULTS Of the 430 patients, 35% (n=150) were classified as STEMI, 29% (n=123) as non-STEMI, and 37% (n=157) with non-ischemic arrest. We did not observe differences by etiology in any of the waveform measures prior to shock 1 (Kruskal-Wallis Test) (p=0.28 for AMSA, p=0.07 for CF, p=0.63 for MF, and p=0.39 for MS). We also did not observe differences for change in waveform between shock 1 and 2, or when the two acute ischemia groups (STEMI and non-STEMI) were combined and compared to the non-ischemic group. CONCLUSION This clinical investigation suggests that waveform measures may not be useful in distinguishing cardiac arrest etiology.

Myocardial Substrate in Secondary Ventricular Fibrillation: Insights from Quantitative Waveform Measures

Abstract Background. Some patients presenting with nonshockable cardiac arrest rhythms will subsequently manifest ventricular fibrillation. Their prognosis remains poor despite transition to a shockable rhythm. Quantitative waveform measures assess the electrophysiologic status of the fibrillating heart and predict outcome. Objective. To use waveform measures to compare those who presented initially with ventricular fibrillation (primary group) with those who manifested ventricular fibrillation after initially presenting with a nonshockable arrest rhythm (secondary group). Methods. We conducted an observational study using a convenience sample to compare waveform measures of amplitude spectrum area (AMSA), cardioversion output predictor (COP), and detrended fluctuation analysis (DFA) prior to initial shock between the primary (n = 178) and secondary (n = 28) groups. We produced a primary group matched to the secondary group based on the average waveform values to evaluate the observed versus expected outcomes in the secondary group. Results. Survival was 42% in the primary group and 0% in the secondary group. There was a trend toward more favorable waveform values in the primary compared with the secondary group (9.48 versus 9.29, p = 0.10 for AMSA; 13.75 versus 14.12, p = 0.003 for COP; and 0.36 versus 0.44, p = 0.09 for DFA). The restricted, matched primary group experienced a survival of 37%, compared with 0% for the secondary group. Conclusions. Taken together, the findings suggest that the electrophysiologic status of the heart may be suitable for resuscitation in at least some secondary ventricular fibrillation cases and that other pathophysiology may contribute substantially to the poor prognosis. Alternately, waveform measures may not predict clinical outcomes in secondary ventricular fibrillation.

Rhythm profiles and survival after out-of-hospital ventricular fibrillation cardiac arrest

OBJECTIVE Treatment: protocols for cardiac arrest rely upon rhythm analyses performed at two-minute intervals, neglecting possible rhythm changes during the intervening period of CPR. Our objective was to describe rhythm profiles (patterns of rhythm transitions during two-minute CPR cycles) following attempted defibrillation and to assess their relationship to survival. METHODS The study included out-of-hospital cardiac arrest cases presenting with ventricular fibrillation from 2011 to 2015. The rhythm sequence was annotated during two-minute CPR cycles after the first and second shocks of each case, and the rhythm profile of each sequence was classified. We calculated absolute survival differences among rhythm profiles with the same rhythm at the two-minute check. RESULTS Of 569 rhythm sequences after the first shock, 46% included a rhythm transition. Overall survival was 47%, and survival proportion varied by rhythm at the two-minute check: ventricular fibrillation (46%), organized (58%) and asystole (20%). Survival was similar between profiles which ended with an organized rhythm at the two-minute check. Likewise, survival was similar between profiles with asystole at the two-minute check. However, in patients with ventricular fibrillation at the two-minute check, survival was twice as high in those with a transient organized rhythm (69%) compared to constant ventricular fibrillation (32%) or transient asystole (28%). CONCLUSION Rhythm transitions are common after attempted defibrillation. Among patients with ventricular fibrillation at the subsequent two-minute check, transient organized rhythm during the preceding two-minute CPR cycle was associated with favorable survival, suggesting distinct physiologies that could serve as the basis for different treatment strategies.

Availability and Accuracy of EMS Information about Chronic Health and Medications in Cardiac Arrest

Introduction Field information available to emergency medical services (EMS) about a patient’s chronic health conditions or medication therapies could help direct patient care or be used to investigate outcome disparities. However, little is known about the field availability or accuracy of information of chronic health conditions or chronic medication treatments in emergent circumstances, especially when the patient cannot serve as an information resource. We evaluated the prehospital availability and accuracy of specific chronic health conditions and medication treatments among out-of-hospital cardiac arrest (OHCA) patients. Methods The investigation was a retrospective cohort study of adult persons suffering ventricular fibrillation OHCA treated by EMS in a large metropolitan county from January 1, 2007, to December 31, 2013. The study was designed to determine the availability and accuracy of EMS ascertainment of selected chronic health conditions and medication treatments. We evaluated chronic health conditions of “any heart disease,” congestive heart failure (CHF), and diabetes and medication treatments of beta blockers and loop diuretics using two distinct sources: 1) EMS report, and 2) hospital record specific to the OHCA event. Because hospital information was considered the gold standard, we restricted the primary analysis to those who were admitted to hospital. Results Of the 1,496 initially eligible patients, 387 could not be resuscitated and were pronounced dead in the field, one patient was left alive at scene due to Physician’s Orders for Life-sustaining Treatment (POLST) orders, 125 expired in the emergency department (n=125), and 983 were admitted to hospital. A total of 832 of 1,496 (55.6%) had both sources of data for comparison and comprised the primary analytic group. Using the hospital record as the gold standard, EMS ascertainment had a sensitivity of 0.79 (304/384) and a specificity of 0.88 (218/248) for any prior heart disease; sensitivity 0.45 (47/105) and specificity 0.87 (477/516) for CHF; sensitivity 0.71 (143/201) and specificity 0.98 (416/424) for diabetes; sensitivity 0.70 (118/169) and specificity 0.94 (273/290) for beta blockers; sensitivity 0.70 (62/89) and specificity 0.97 (358/370) for loop diuretics. Conclusion In this cohort of OHCA, information about selected chronic health conditions and medication treatments based on EMS ascertainment was available for many patients, generally revealing moderate sensitivity and greater specificity.