Steven C. Brooks

Ventricular Tachyarrhythmias after Cardiac Arrest in Public versus at Home

BACKGROUNDnThe incidence of ventricular fibrillation or pulseless ventricular tachycardia as the first recorded rhythm after out-of-hospital cardiac arrest has unexpectedly declined. The success of bystander-deployed automated external defibrillators (AEDs) in public settings suggests that this may be the more common initial rhythm when out-of-hospital cardiac arrest occurs in public. We conducted a study to determine whether the location of the arrest, the type of arrhythmia, and the probability of survival are associated.nnnMETHODSnBetween 2005 and 2007, we conducted a prospective cohort study of out-of-hospital cardiac arrest in adults in 10 North American communities. We assessed the frequencies of ventricular fibrillation or pulseless ventricular tachycardia and of survival to hospital discharge for arrests at home as compared with arrests in public.nnnRESULTSnOf 12,930 evaluated out-of-hospital cardiac arrests, 2042 occurred in public and 9564 at home. For cardiac arrests at home, the incidence of ventricular fibrillation or pulseless ventricular tachycardia was 25% when the arrest was witnessed by emergency-medical-services (EMS) personnel, 35% when it was witnessed by a bystander, and 36% when a bystander applied an AED. For cardiac arrests in public, the corresponding rates were 38%, 60%, and 79%. The adjusted odds ratio for initial ventricular fibrillation or pulseless ventricular tachycardia in public versus at home was 2.28 (95% confidence interval [CI], 1.96 to 2.66; P < 0.001) for bystander-witnessed arrests and 4.48 (95% CI, 2.23 to 8.97; P<0.001) for arrests in which bystanders applied AEDs. The rate of survival to hospital discharge was 34% for arrests in public settings with AEDs applied by bystanders versus 12% for arrests at home (adjusted odds ratio, 2.49; 95% CI, 1.03 to 5.99; P = 0.04).nnnCONCLUSIONSnRegardless of whether out-of-hospital cardiac arrests are witnessed by EMS personnel or bystanders and whether AEDs are applied by bystanders, the proportion of arrests with initial ventricular fibrillation or pulseless ventricular tachycardia is much greater in public settings than at home. The incremental value of resuscitation strategies, such as the ready availability of an AED, may be related to the place where the arrest occurs.

Out-of-Hospital Cardiac Arrest Frequency and Survival: Evidence for Temporal Variability

AIMnSome cardiac phenomena demonstrate temporal variability. We evaluated temporal variability in out-of-hospital cardiac arrest (OHCA) frequency and outcome.nnnMETHODSnProspective cohort study (the Resuscitation Outcomes Consortium) of all OHCA of presumed cardiac cause who were treated by emergency medical services within 9 US and Canadian sites between 12/1/2005 and 02/28/2007. In each site, Emergency Medical System records were collected and analyzed. Outcomes were individually verified by trained data abstractors.nnnRESULTSnThere were 9667 included patients. Median age was 68 (IQR 24) years, 66.7% were male and 8.3% survived to hospital discharge. The frequency of cardiac arrest varied significantly across time blocks (p<0.001). Compared to the 0001-0600 hourly time block, the odds ratios and 95% CIs for the occurrence of OHCA were 2.02 (1.90, 2.15) in the 0601-1200 block, 2.01 (1.89, 2.15) in the 1201-1800 block, and 1.73 (1.62, 1.85) in the 1801-2400 block. The frequency of all OHCA varied significantly by day of week (p=0.03) and month of year (p<0.001) with the highest frequencies on Saturday and during December. Survival to hospital discharge was lowest when the OHCA occurred during the 0001-0600 time block (7.3%) and highest during the 1201-1800 time block (9.6%). Survival was highest for OHCAs occurring on Mondays (10.0%) and lowest for those on Wednesdays (6.8%) (p=0.02).nnnCONCLUSIONnThere is temporal variability in OHCA frequency and outcome. Underlying patient, EMS system and environmental factors need to be explored to offer further insight into these observed patterns.

Socioeconomic status and incidence of sudden cardiac arrest

Background: Low socioeconomic status is associated with poor cardiovascular health. We evaluated the association between socioeconomic status and the incidence of sudden cardiac arrest, a condition that accounts for a substantial proportion of cardiovascular-related deaths, in seven large North American urban populations. Methods: Using a population-based registry, we collected data on out-of-hospital sudden cardiac arrests occurring at home or at a residential institution from Apr. 1, 2006, to Mar. 31, 2007. We limited the analysis to cardiac arrests in seven metropolitan areas in the United States (Dallas, Texas; Pittsburgh, Pennsylvania; Portland, Oregon; and Seattle–King County, Washington) and Canada (Ottawa and Toronto, Ontario; and Vancouver, British Columbia). Each incident was linked to a census tract; tracts were classified into quartiles of median household income. Results: A total of 9235 sudden cardiac arrests were included in the analysis. For all sites combined, the incidence of sudden cardiac arrestin the lowest socioeconomic quartile was nearly double that in the highest quartile (incidence rate ratio [IRR] 1.9, 95% confidence interval [CI] 1.8–2.0). This disparity was greater among people less than 65 years old (IRR 2.7, 95% CI 2.5–3.0) than among those 65 or older (IRR 1.3, 95% CI 1.2–1.4). After adjustment for study site and for population age structure of each census tract, the disparity across socioeconomic quartiles for all ages combined was greater in the United States (IRR 2.0, 95% CI 1.9–2.2) than in Canada (IRR 1.8, 95% CI 1.6–2.0) (p < 0.001 for interaction). Interpretation: The incidence of sudden cardiac arrest at home or at a residential institution was higher in poorer neighbourhoods of the US and Canadian sites studied, although the association was attenuated in Canada. The disparity across socioeconomic quartiles was greatest among people younger than 65. The association between socioeconomic status and incidence of sudden cardiac arrest merits consideration in the development of strategies to improve survival from sudden cardiac arrest, and possibly to identify opportunities for prevention.

Implementation of therapeutic hypothermia guidelines for post-cardiac arrest syndrome at a glacial pace: Seeking guidance from the knowledge translation literature

The 2005 International Liaison Committee on Resuscitation (ILCOR) Consensus on Science and Treatment Recommendations document represents the most extensive and rigorous systematic review of the resuscitation literature to date and included evidence-based recommendations for post-resuscitation care. A new recommendation for the induction of mild therapeutic hypothermia for comatose cardiac arrest survivors was included in this document. Accordingly, constituent national member associations of ILCOR, including the American Heart Association, incorporated the recommendation for therapeutic hypothermia into their respective guidelines. Despite these endorsements there is a concern that therapeutic hypothermia is not being used in practice. Data from a number of surveys in Europe and the United States suggest that rates of use among physicians may be as low as 30-40%. Despite the cost and effort associated with the production of these guidelines and the potential impact on patient care, current efforts in implementing the guideline have not achieved widespread success. This commentary explores the issue of underutilization of the American Heart Association guidelines for therapeutic hypothermia and looks to the knowledge translation literature to inform a new approach to implementation. We will review the underlying phenomenon of research implementation into practice, specific barriers to guideline implementation and interventions that may improve therapeutic hypothermia uptake.

Predictors of adopting therapeutic hypothermia for post-cardiac arrest patients among Canadian emergency and critical care physicians

Therapeutic hypothermia improves outcomes in resuscitated cardiac arrest patients, but prior application rates are less than 30%. We sought to evaluate self-reported physician adoption, predictors of adoption, and barriers to use among Canadian emergency and critical care physicians. A web-based modified Dillman questionnaire asked all physicians on the membership lists of the Canadian Association of Emergency Physicians and the Canadian Critical Care Forum physicians to report their experience with therapeutic hypothermia using the Pathman framework of changing physician behaviour. We used logistic regression to explore the association between physician and practice variables and the adoption of therapeutic hypothermia. We surveyed 1264 physicians; 39% responded. Most (78%) were emergency physicians, 54% worked at tertiary care hospitals, 62% treated >10 arrests annually and 50% had standardized cooling protocols. Most respondents were aware of therapeutic hypothermia (99%) and agreed that it is beneficial (91%), but only two-thirds (68%) had used it in clinical practice. Predictors for adopting therapeutic hypothermia included critical care field of practice (OR 6.3, 95% CI 2.5-16.0), availability of a cooling protocol (OR 5.6, CI 3.1-10.0), being <10 years post-residency (OR 2.0, CI 1.2-3.3), and treating >10 cardiac arrests annually (OR 2.6, CI 1.6-4.1). Common barriers included: lack of awareness of recommended practice (31%), perceptions of poor prognosis (25%), too much work required to cool (20%) and staffing shortages (20%). Therapeutic hypothermia after cardiac arrest has not been universally adopted. Adoption might be improved through protocol implementation, education about benefits and prognosis, and strategies to make administration easier.

Development of a data dictionary for the Strategies for Post Arrest Resuscitation Care (SPARC) network for post cardiac arrest research.

BACKGROUNDnThe widely accepted Utstein style has standardized data collection and analysis in resuscitation and post resuscitation research. However, collection of many of these variables poses significant practical challenges. In addition, several important variables in post resuscitation research are missing.nnnOBJECTIVEnOur aim was to develop a comprehensive data dictionary and web-based data collection tool as part of the Strategies for Post Arrest Resuscitation Care (SPARC) Network project, which implemented a knowledge translation program for post cardiac arrest therapeutic hypothermia in 37 Ontario hospitals.nnnMETHODSnA list of data variables was generated based on the current Utstein style, previous studies and expert opinion within our group of investigators. We developed a data dictionary by creating clear definitions and establishing abstraction instructions for each variable. The data dictionary was integrated into a web-based collection form allowing for interactive data entry. Two blinded investigators piloted the data collection tool, by performing a retrospective chart review.nnnRESULTSnA total of 454 variables were included of which 400 were Utstein, 2 were adapted from existing studies and 52 were added to address missing elements. Kappa statistics for two outcome variables, survival to discharge and induction of therapeutic hypothermia were 0.86 and 0.64, respectively.nnnCONCLUSIONnThis is the first attempt in the literature to develop a data dictionary as part of a standardized, pragmatic data collection tool for post cardiac arrest research patients. In addition, our dataset defined important variables that were previously missing. This data collection tool can serve as a reference for future trials in post cardiac arrest care.

Novel biomarkers in diagnosing cardiac ischemia in the emergency department: A systematic review

BACKGROUNDnNovel biomarkers of myocardial ischemia and inflammatory processes have the potential to improve diagnostic accuracy of acute coronary syndrome (ACS) within a shorter time interval after symptom onset.nnnOBJECTIVEnThe objective was to review the recent literature and evaluate the evidence for use of novel biomarkers in diagnosing ACS in patients presenting with chest pain or symptoms suggestive of cardiac ischemia to the emergency department or chest pain unit.nnnMETHODSnA literature search was performed in MEDLINE, EMBASE, Cochrane DSR, ACP Journal Club, DARE, CCTR, CMR, HTA, and NHSEED for studies from 2004 to 2010. We used the inclusion criteria: (1) human subjects, (2) peer-reviewed articles, (3) enrolled patients with ACS, acute myocardial infarction or undifferentiated signs and symptoms suggestive of ACS, and (4) English language or translated manuscripts. Two reviewers conducted a hierarchical selection and assessment using a scale developed by the International Liaison Committee on Resuscitation.nnnRESULTSnOut of a total 3194 citations, 58 articles evaluating 37 novel biomarkers were included for final review. Forty-one studies did not support the use of their respective biomarkers. Seventeen studies supported the use of 5 biomarkers, particularly when combined with cardiac-specific troponin: heart fatty acid-binding protein, ischemia-modified albumin, B-type natriuretic peptide, copeptin, and matrix metalloproteinase-9.nnnCONCLUSIONnIn patients presenting to the emergency department with chest pain or symptoms suggestive of cardiac ischemia, there is inadequate evidence to suggest the routine testing of novel biomarkers in isolation. However, several novel biomarkers have the potential to improve the sensitivity of diagnosing ACS when combined with cardiac-specific troponin.

Patient safety in emergency medical services: executive summary and recommendations from the Niagara Summit

Emergency medical services (EMS) personnel care for patients in challenging and dynamic environments that may contribute to an increased risk for adverse events. However, little is known about the risks to patient safety in the EMS setting. To address this knowledge gap, we conducted a systematic review of the literature, including nonrandomized, noncontrolled studies, conducted qualitative interviews of key informants, and, with the assistance of a pan-Canadian advisory board, hosted a 1-day summit of 52 experts in the field of EMS patient safety. The intent of the summit was to review available research, discuss the issues affecting prehospital patient safety, and discuss interventions that might improve the safety of the EMS industry. The primary objective was to define the strategic goals for improving patient safety in EMS. Participants represented all geographic regions of Canada and included administrators, educators, physicians, researchers, and patient safety experts. Data were collected through electronic voting and qualitative analysis of the discussions. The group reached consensus on nine recommendations to increase awareness, reduce adverse events, and suggest research and educational directions in EMS patient safety: increasing awareness of patient safety principles, improving adverse event reporting through creating nonpunitive reporting systems, supporting paramedic clinical decision making through improved research and education, policy changes, using flexible algorithms, adopting patient safety strategies from other disciplines, increasing funding for research in patient safety, salary support for paramedic researchers, and access to graduate training in prehospital research.

Neural and Hypotensive Effects of Angiotensin II Receptor Blockade

Angiotensin II participates in the neural regulation of the heart and circulation at both central and peripheral sites. To explore the role of endogenous angiotensin II in blood pressure regulation, we conducted a randomized double-blind crossover trial in nine young healthy men (aged 33+/-3 [mean+/-SE] years) studied in the absence of salt restriction, comparing the effect of 1 week treatment with the angiotensin II receptor antagonist losartan (100 mg daily) against placebo with respect to the following variables, recorded during supine rest: intra-arterial blood pressure (BP), heart rate (HR), forearm vascular resistance and norepinephrine appearance rate, total body norepinephrine spillover, variability of BP and HR (spectral analysis), and baroreflex sensitivity for HR (gain of the transfer function from systolic BP to HR). Blood pressure was 119+/-7/66+/-4 mm Hg (systolic BP/diastolic BP) after 1 week of placebo and 112+/-6/61+/-3 mm Hg after 1 week of losartan (P<.05). Forearm vascular resistance tended to fall, from 42.3+/-6.9 U on placebo to 32.8+/-5.0 U with losartan treatment (P=.07). Losartan had no effect on HR (60+/-3 on placebo versus 59+/-2 beats per minute with losartan), total body norepinephrine spillover (3.0+/-0.8 versus 3.3+/-1.2 nmol/min), forearm norepinephrine appearance rate (3.8+/-1.1 versus 5.3+/-1.1 pmol/100 mL forearm tissue per minute), power in the high- or low-frequency components of the HR variability and BP variability spectra or on baroreflex sensitivity for HR. Endogenous angiotensin II contributes to the maintenance of supine BP in normal subjects, studied in the absence of sodium restriction. The fall in BP caused by losartan is accompanied by a resetting of the baroreflex regulation of HR and sympathetic outflow, but baroreflex sensitivity for heart rate is not altered. Therefore, the reduction in BP observed after short-term angiotensin type 1 receptor antagonism may be achieved through a direct effect on vascular tone rather than through a primary reduction in sympathetic outflow.

Caffeine abstinence augments the systolic blood pressure response to adenosine in humans

Blood pressure and heart rate responses to adenosine infusion (35, 70, and 140 microg/kg/min, intravenously) were studied in 7 healthy men after 6, 30, 78, 150, and 318 hours of abstinence from regular caffeine use. The finding that caffeine abstinence augmented the systolic pressor response (from -1 +/- 2 mm Hg at 6 hours to +9 +/- 2 mm Hg at 318 hours; p = 0.01) but not the tachycardic response to adenosine has implications for current clinical and research applications of this purine.