Development and external validation of prediction models to predict implantable cardioverter-defibrillator efficacy in primary prevention of sudden cardiac death.

AIMS: This study was performed to develop and externally validate prediction models for appropriate implantable cardioverter-defibrillator (ICD) shock and mortality to identify subgroups with insufficient benefit from ICD implantation. METHODS AND RESULTS: We recruited patients scheduled for primary prevention ICD implantation and reduced left ventricular function. Bootstrapping-based Cox proportional hazards and Fine and Gray competing risk models with likely candidate predictors were developed for all-cause mortality and appropriate ICD shock, respectively. Between 2014 and 2018, we included 1441 consecutive patients in the development and 1450 patients in the validation cohort. During a median follow-up of 2.4 (IQR 2.1-2.8) years, 109 (7.6%) patients received appropriate ICD shock and 193 (13.4%) died in the development cohort. During a median follow-up of 2.7 (IQR 2.0-3.4) years, 105 (7.2%) received appropriate ICD shock and 223 (15.4%) died in the validation cohort. Selected predictors of appropriate ICD shock were gender, NSVT, ACE/ARB use, atrial fibrillation history, Aldosterone-antagonist use, Digoxin use, eGFR, (N)OAC use, and peripheral vascular disease. Selected predictors of all-cause mortality were age, diuretic use, sodium, NT-pro-BNP, and ACE/ARB use. C-statistic was 0.61 and 0.60 at respectively internal and external validation for appropriate ICD shock and 0.74 at both internal and external validation for mortality. CONCLUSION: Although this cohort study was specifically designed to develop prediction models, risk stratification still remains challenging and no large group with insufficient benefit of ICD implantation was found. However, the prediction models have some clinical utility as we present several scenarios where ICD implantation might be postponed.

Association of beta-blockers and first-registered heart rhythm in out-of-hospital cardiac arrest: real-world data from population-based cohorts across two European countries.

AIMS: Conflicting results have been reported regarding the effect of beta-blockers on first-registered heart rhythm in out-of-hospital cardiac arrest (OHCA). We aimed to establish whether the use of beta-blockers influences first-registered rhythm in OHCA. METHODS AND RESULTS: We included patients with OHCA of presumed cardiac cause from two large independent OHCA-registries from Denmark and the Netherlands. Beta-blocker use was defined as exposure to either non-selective beta-blockers, ß1-selective beta-blockers, or α-ß-dual-receptor blockers within 90 days prior to OHCA. We calculated odds ratios (ORs) for the association of beta-blockers with first-registered heart rhythm using multivariable logistic regression. We identified 23 834 OHCA-patients in Denmark and 1584 in the Netherlands: 7022 (29.5%) and 519 (32.8%) were treated with beta-blockers, respectively. Use of non-selective beta-blockers, but not ß1-selective blockers, was more often associated with non-shockable rhythm than no use of beta-blockers [Denmark: OR 1.93, 95% confidence interval (CI) 1.48-2.52; the Netherlands: OR 2.52, 95% CI 1.15-5.49]. Non-selective beta-blocker use was associated with higher proportion of pulseless electrical activity (PEA) than of shockable rhythm (OR 2.38, 95% CI 1.01-5.65); the association with asystole was of similar magnitude, although not statistically significant compared with shockable rhythm (OR 2.34, 95% CI 0.89-6.18; data on PEA and asystole were only available in the Netherlands). Use of α-ß-dual-receptor blockers was significantly associated with non-shockable rhythm in Denmark (OR 1.21; 95% CI 1.03-1.42) and not significantly in the Netherlands (OR 1.37; 95% CI 0.61-3.07). CONCLUSION: Non-selective beta-blockers, but not ß1-selective beta-blockers, are associated with non-shockable rhythm in OHCA.

The contribution of comorbidity and medication use to poor outcome from out-of-hospital cardiac arrest at home locations.

INTRODUCTION: Out-of-hospital cardiac arrest (OHCA) at home is associated with lower rates of shockable initial rhythm and survival than OHCA in a public location. We determined whether medical history and medication use explain the association between OHCA location and presence of shockable initial rhythm and survival rate. METHODS: Data from ARREST, an OHCA registry in the Netherlands, were used (January 2009-December 2012). We assessed if OHCA location remained associated with a) presence of shockable initial rhythm and b) survival when taking medical history, medication use, resuscitation characteristics and demographics into account in a multivariable regression analysis. The relative contributions of the above mentioned variables to variance in both outcome measures was estimated using the Nagelkerke test. RESULTS: We included 1404 patients (1034 [73.6%] home OHCA, 370 [26.4%] public OHCA). OHCA location remained significantly associated with shockable initial rhythm (home 42.7%, public 78.1%; P < 0.01) and survival to hospital discharge (home 14.0%, public 45.7%; P < 0.01). Adding resuscitation characteristics to models of shockable initial rhythm and survival rate resulted in an increase in explained variance (13.0%-23.6%), whereas adding medical history or medication use to these models resulted in only a limited increase in explained variance (medical history to 27.6%, medication use to 30.0%). CONCLUSIONS: Comorbidity and medication use do not substantially contribute in explaining the poor outcome from out-of-hospital cardiac arrest occurring at home. Even when adjusted for medical history, medication use, resuscitation characteristics, and demographics, a large gap of unexplained variance in shockable initial rhythm and survival remains.

Occurrence of shockable rhythm in out-of-hospital cardiac arrest over time: A report from the COSTA group.

BACKGROUND: Prior research suggests that the proportion of a shockable initial rhythm in out-of-hospital cardiac arrest (OHCA) declined during the last decades. This study aims to investigate if this decline is still ongoing and explore the relationship between location of OHCA and proportion of a shockable initial rhythm as initial rhythm. METHODS: We calculated the proportion of patients with a shockable initial rhythm between 2006-2015 using pooled data from the COSTA-group (Copenhagen, Oslo, Stockholm, Amsterdam). Analyses were stratified according to location of OHCA (residential vs. public). RESULTS: A total of 19,054 OHCA cases were included. Overall, the total proportion of cases with a shockable initial rhythm decreased from 42% to 37% (P < 0.01) from 2006 to 2015. When stratified according to location, the proportion of cases with a shockable initial rhythm decreased for OHCAs at a residential location (34% to 27%; P = 0.03), while the proportion of a shockable initial rhythm was stable among OHCAs in public locations (59%-57%; P = 0.2). During the last years of the study period (2011-2015), the overall proportion of a shockable initial rhythm remained stable (38%-37%; P = 0.45); this was observed for both residential and public OHCA. CONCLUSION: We found a decline in the proportion of patients with a shockable initial rhythm in OHCAs at a residential location; this decline levelled off during the second half of the study period (2011-2015). In public locations, we observed no decline in shockable initial rhythm over time.

Ventricular fibrillation waveform characteristics in out-of-hospital cardiac arrest and cardiovascular medication use.

BACKGROUND: Ventricular fibrillation (VF) waveform analyses are considered a reliable proxy for OHCA characteristics in out-of-hospital cardiac arrest (OHCA), but patient characteristics such as cardiovascular medication use might also be associated with changes in VF waveform measures. OBJECTIVES: To assess associations between cardiovascular medication use and amplitude spectrum area (AMSA) of VF, while correcting for the presence of cardiovascular disease (CVD), CVD risk factors, and OHCA characteristics. METHODS: We included 990 VF patients from an OHCA registry in the Netherlands, with available information on medical history and cardiovascular medication use. Associations between cardiovascular medication use and AMSA were tested in a multivariate linear regression model, adjusting for CVD, CVD risk factors, and OHCA characteristics. Model performance was shown using R-square and R-change. We also calculated whether medication use was associated with faster dissolution of AMSA to lower values with increasing time delay. RESULTS: In the multivariate analysis, when corrected for CVD, CVD risk factors and OHCA characteristics, only potassium-sparing agents were associated with a lower AMSA when compared to patients using other cardiovascular medications (OR 0.46 [95% CI 0.10-0.81]; P < 0.012). The decrease in AMSA with increasing EMS-call-to-ECG delay was the same for patients with and without cardiovascular medication use (all P > 0.05). Only a small part of the variance in AMSA could be explained by medication use (R-square 0.003- 0.026). Adding OHCA characteristics to the model resulted in the largest R square change (0.09-0.15). CONCLUSIONS: It is unlikely that there is a strong and clinically relevant independent pharmacologic effect of cardiovascular medication use on AMSA. In OHCA, AMSA might be used as patient management tool without considering cardiovascular medication use.

Transfer of essential AED information to treating hospital (TREAT).

BACKGROUND: Defibrillation in out-of-hospital cardiac arrest (OHCA) is increasingly performed by using an Automated External Defibrillator (AED). Therefore presence of a shockable rhythm is recurrently only documented by the AED. However, AED-information is rarely available to the treating physician. PURPOSE: To determine (1) how often a shockable rhythm was recorded only in the AED; (2) if so, how often information that a shockable rhythm had been present reached the physician. METHODS: Data on OHCA patients with (presumed) cardiac cause with an AED connected in the years 2012-2014 (Study period 1) and 2016 (Study period 2) in the Amsterdam Resuscitation Study (ARREST) database were collected. We determined how often only the AED had defibrillated. In these patients, we retrospectively analyzed EMS run sheets and hospital discharge letters to determine if a shockable rhythm and/or AED use was correctly noted. In Study period 2, we prospectively contacted the physicians to study whether AED defibrillation was known. RESULTS: In Study period 1, of 2840 OHCA CPR attempts with (presumed) cardiac cause, 1521 (54%) patients had a shockable rhythm, with 356 patients (13%) receiving AED defibrillation only. Of these patients, 11 hospital discharge letters (4%) contained no information about a shockable rhythm. In Study period 2, 125/1128 patients (11%) received AED defibrillation only; of these, in two cases the shockable rhythm was unknown by the physician. CONCLUSION: In 11-13% of OHCAs, a shockable rhythm is only seen on the AED-ECG. Adequate transfer to the physician of vital AED-information is essential but not always accomplished.

Resuscitation for out-of-hospital cardiac arrest in adults with congenital heart disease.

AIMS: Adult congenital heart disease (ACHD) patients are at increased risk of sudden cardiac death and out-of-hospital cardiac arrest (OHCA). Currently, insufficient data exist on outcome, causes and circumstances of OHCA of ACHD patients resuscitated for OHCA. We investigate these parameters in ACHD patients in comparison to OHCA in the general population. METHODS AND RESULTS: We identified ACHD patients with OHCA by linking data from a Dutch nationwide registry of ACHD patients (CONCOR, n = 15,727), and ARREST, a cohort of OHCA cases (n = 17,868). 62 ACHD patients with OHCA were identified. Ventricular septal defect (n = 11), bicuspid aortic valve (n = 10) and atrial septal defect (n = 8) were the most common diagnoses. We included OHCA cases from the general population as controls. ACHD patients were younger than controls (n = 11,624) at the time of OHCA (47 (SD ±â€¯17) years vs. 66 (SD ±â€¯15) years, respectively, p < 0.001), and more often had a shockable initial rhythm (67% vs 40%, respectively, p < 0.001). A cardiac cause of OHCA was identified in 76% of ACHD patients, with only 7% due to myocardial infarction or ischemia. Survival was better in ACHD patients than in controls (44% vs. 19%, p < 0.001), but this difference disappeared after correction for age, gender, witnessed arrest, bystander resuscitation, public location and shockable rhythm. CONCLUSIONS: OHCA in ACHD patients occurs at young age, is rarely caused by ischemia and occurs mainly in patients with simple congenital defects. Risk stratification efforts should therefore not be restricted to ACHD patients with severe congenital defects.

Different defibrillation strategies in survivors after out-of-hospital cardiac arrest.

BACKGROUND: In the last decade, there has been a rapid increase in the dissemination of automated external defibrillators (AEDs) for prehospital defibrillation of out-of-hospital cardiac arrest patients. The aim of this study was to study the association between different defibrillation strategies on survival rates over time in Copenhagen, Stockholm, Western Sweden and Amsterdam, and the hypothesis was that non-EMS defibrillation increased over time and was associated with increased survival. METHODS: We performed a retrospective analysis of four prospectively collected cohorts of out-of-hospital cardiac arrest patients between 2008 and 2013. Emergency medical service (EMS)-witnessed arrests were excluded. RESULTS: A total of 22 453 out-of-hospital cardiac arrest patients with known survival status were identified, of whom 2957 (13%) survived at least 30 days postresuscitation. Of all survivors with a known defibrillation status, 2289 (81%) were defibrillated, 1349 (59%) were defibrillated by EMS, 454 (20%) were defibrillated by a first responder AED and 429 (19%) were defibrillated by an onsite AED and 57 (2%) were unknown. The percentage of survivors defibrillated by first responder AEDs (from 13% in 2008 to 26% in 2013, p<0.001 for trend) and onsite AEDs (from 14% in 2008 to 30% in 2013, p<0.001 for trend) increased. The increased use of these non-EMS AEDs was associated with the increase in survival rate of patients with a shockable initial rhythm. CONCLUSION: Survivors of out-of-hospital cardiac arrest are increasingly defibrillated by non-EMS AEDs. This increase is primarily due to a large increase in the use of onsite AEDs as well as an increase in first-responder defibrillation over time. Non-EMS defibrillation accounted for at least part of the increase in survival rate of patients with a shockable initial rhythm.

Predictive value of amplitude spectrum area of ventricular fibrillation waveform in patients with acute or previous myocardial infarction in out-of-hospital cardiac arrest.

BACKGROUND: Amplitude spectrum area (AMSA) of ventricular fibrillation (VF) has been associated with survival from out-of-hospital cardiac arrest (OHCA). Ischemic heart disease has been shown to change AMSA. We studied whether the association between AMSA and survival changes with acute ST-elevation myocardial infarction (STEMI) as cause of the OHCA and/or previous MI. METHODS: Multivariate logistic regression with log-transformed AMSA of first artifact-free VF segment was used to assess the association between AMSA and survival, according to presence of STEMI or previous MI, adjusting for resuscitation characteristics, medication use and comorbidities. RESULTS: Of 716 VF-patients included from an OHCA-registry in the Netherlands, 328 (46%) had STEMI as cause of OHCA. Previous MI was present in 186 (26%) patients. Survival was 66%; neither previous MI (P=0.11) nor STEMI (P=0.78) altered survival. AMSA was a predictor of survival (ORadj: 1.52, 95%-CI: 1.28-1.82). STEMI was associated with lower AMSA (8.4mV-Hz [3.7-16.5] vs. 12.3mV-Hz [5.6-23.0]; P<0.001), but previous MI was not (9.5mV-Hz [3.9-18.0] vs 10.6mV-Hz [4.6-19.3]; P=0.27). When predicting survival, there was no interaction between previous MI and AMSA (P=0.14). STEMI and AMSA had a significant interaction (P=0.002), whereby AMSA was no longer a predictor of survival (ORadj: 1.03, 95%-CI: 0.77-1.37) in STEMI-patients. In patients without STEMI, higher AMSA was associated with higher survival rates (ORadj: 1.80, 95%-CI: 1.39-2.35). CONCLUSIONS: The prognostic value of AMSA is altered by the presence of STEMI: while AMSA has strong predictive value in patients without STEMI, AMSA is not a predictor of survival in STEMI-patients.

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.

Conduction disorders in bradyasystolic out-of-hospital cardiac arrest.

AIMS: Bradyasystolic heart rhythms are often recorded in out-of-hospital cardiac arrest (OHCA). Atrioventricular (AV) conduction disorders might lead to OHCA, but the prevalence of AV-conduction disorders and other bradyasystolic rhythms in OHCA is unknown. These patients might benefit from pre-hospital pacing. We aimed to determine the prevalence of different types of bradyasystolic heart rhythms in OHCA, including third degree AV-block, and document survival rates. METHODS: We used data from the ARREST-registry of OHCA in the Netherlands. Patients with bradyasystolic OHCA in 2006-2012 were included. ECGs were classified according to the presence of P-waves and QRS complexes in five rhythm groups. Differences in survival to discharge in relation to resuscitation characteristics, rhythm and pacing were tested using Chi-Square test and multivariate regression analysis. RESULTS: We included 2333 patients with a bradyasystolic rhythm; 371 patients (16%) presented with a third degree AV-block. In total 45 patients (1.9%, 95%-CI 1.4-2.5%) survived. A third degree AV-block (adjusted OR 0.86, 95%-CI 0.38-1.96) or pacing (adjusted OR 0.89, 95%-CI 0.21-3.78) was not associated with survival. Pacing was initiated in 110 patients (4.7%), after a long delay (median 18.7min). The strongest association with survival was found for the presence of a bradycardia (vs. asystole) (adjusted OR 4.20, 95%-CI 1.79-9.83), bystander witnessed (OR 4.13, 95%-CI 1.45-11.8) and EMS witnessed collapse (OR 5.18, 95%-CI 2.77-9.67). CONCLUSION: In bradyasystolic OHCA, 16% of all patients present with third degree AV-block, but survival for these and other bradyasystolic patients remains poor. Pacing is seldom initiated, often delayed, and rarely beneficial.

Minimizing pre- and post-shock pauses during the use of an automatic external defibrillator by two different voice prompt protocols. A randomized controlled trial of a bundle of measures.

BACKGROUND: Previous large retrospective analyses have found an association between duration of peri-shock pauses in cardiopulmonary resuscitation (CPR) and survival. In a randomized trial, we tested whether shortening these pauses improves survival after out-of-hospital cardiac arrest (OHCA). METHODS: Patients with OHCA between May 2006 and January 2014 with shockable initial rhythm, treated by first responders, were randomized to two automated external defibrillator (AED) treatment protocols. In the control protocol AEDs performed post-shock analysis and prompted rescuers to a pulse check (Guidelines 2000). In the experimental protocol a 15s period of CPR during and after charging of the AED was added to the voice prompts and CPR was resumed immediately after defibrillation (modification of the Guidelines 2005). Survival was assessed at hospital admission and discharge. RESULTS: Of 1174 OHCA patients, 456 met the inclusion criteria: 227 were randomly assigned to the experimental protocol and 229 to the control protocol. The experimental group experienced shorter pre-shock pauses (6 [5-11]s vs. 20 [18-23]s; P<0.001), and shorter post-shock pauses (7 [6-9]s vs. 27 [16-34]s; P<0.001). Similar proportions of patients survived to hospital admission (experimental: 62% vs. CONTROL: 65%; RR [95%CI] 0.96 [0.83-1.10], P=0.51), and hospital discharge (experimental: 42% vs. CONTROL: 38%; RR [95%CI] 1.09 [0.87-1.37], P=0.46). CONCLUSION: In patients with OHCA and shockable initial rhythms, treatment with AEDs with the experimental protocol shortened pre-shock and post-shock CPR pauses, and increased overall CPR time, but did not improve survival to hospital admission or discharge. CLINICAL TRIAL REGISTRATION: http://www.isrctn.com unique identifier: ISRCTN72257677.

Causes for the declining proportion of ventricular fibrillation in out-of-hospital cardiac arrest.

AIMS: The reported proportion of ventricular fibrillation (VF) in out-of-hospital cardiac arrest (OHCA) has declined worldwide. VF decline may be caused by less VF at collapse and/or faster dissolution of VF into asystole. We aimed to determine the causes of VF decline by comparing VF proportions in relation to delay from emergency medical services (EMS) call to initial ECG (call-to-ECG delay), and VF dissolution rates between two study periods. METHODS: Data from the AmsteRdam REsuscitation STudies (ARREST), an ongoing OHCA registry in the Netherlands, were used. We studied cardiac OHCA in the study periods 1995-1997 (n=917) and 2006-2012 (n=5695). Cases with available ECG and information on call-to-ECG delay were included. We tested whether initial VF proportion and VF dissolution rates differed between both study periods using logistic regression. RESULTS: Despite a 15% VF decline between the periods, VF proportion around EMS call remained high in 2006-2012 (64%). The odds ratio (OR) for VF proportion in 2006-2012 vs. 1995-1997 was 0.52 (95%-CI 0.45-0.60, P<0.001), with similar rates of VF dissolution in both periods (P=0.83). VF decline was higher for unwitnessed collapse (OR 0.41, 95%-CI 0.28-0.58) and collapse at home (OR 0.50, 95%-CI 0.42-0.59), but not for categories of bystander CPR, age or sex. CONCLUSION: VF proportion early after collapse remains high. VF decline is explained by the occurrence of less initial VF, rather than faster dissolving VF. An increase in unwitnessed OHCA and collapse at home contributes to the observed VF decline.

Comorbidity and favorable neurologic outcome after out-of-hospital cardiac arrest in patients of 70 years and older.

INTRODUCTION: Advanced age is reported to be associated with lower survival after out-of-hospital cardiac arrest (OHCA). We aimed to establish survival rate and neurological outcome at hospital discharge after OHCA in older patients and evaluated whether pre-OHCA comorbidity was associated with favorable neurologic outcome. METHODS: From a prospective registry of all cardiopulmonary resuscitation (CPR) attempts after OHCA, we established survival in 1332 patients aged ≥ 70 years in whom resuscitation with non-traumatic etiology was attempted in 2009-2011. Pre-OHCA factors (age, gender, residing in long-term care institution, Charlson Comorbidity Index [CCI] score) and resuscitation parameters (initial rhythm, bystander witnessed, bystander CPR and time to defibrillator connection) with survival at hospital discharge with favorable neurologic outcome were regressed in the 851 patients of whom CCI was known. RESULTS: We found a 12% survival to discharge rate in patients aged ≥ 70 years (70-79 years: 16%; ≥ 80 years: 8%, p=0.001). Among surviving patients, 90% survived with favorable neurologic outcome. In a model with only pre-OHCA factors age was significantly associated with outcome (age OR 0.94, 95%CI 0.91-0.98), p = 0.003). High CCI score (≥ 4) was not statistically significant when associated with survival (7% vs. 12%, OR 0.53, 95%CI (0.25-1.13), p = 0.10). When adjusted for resuscitation parameters, OR for high CCI was 0.71 (95% CI 0.28-1.80, p = 0.47), also none of the other pre-OHCA factors remained statistically significant. CONCLUSION: In the Netherlands, the survival rate in older patients was 12%; the great majority survived with favorable neurologic outcome. Resuscitation-related factors and not comorbidity determine outcome after OHCA in older patients.

Improved survival after out-of-hospital cardiac arrest and use of automated external defibrillators.

BACKGROUND: In recent years, a wider use of automated external defibrillators (AEDs) to treat out-of-hospital cardiac arrest was advocated in The Netherlands. We aimed to establish whether survival with favorable neurologic outcome after out-of-hospital cardiac arrest has significantly increased, and, if so, whether this is attributable to AED use. METHODS AND RESULTS: We performed a population-based cohort study, including patients with out-of-hospital cardiac arrest from cardiac causes between 2006 and 2012, excluding emergency medical service-witnessed arrests. We determined survival status at each stage (to emergency department, to admission, and to discharge) and examined temporal trends using logistic regression analysis with year of resuscitation as an independent variable. By adding each covariable subsequently to the regression model, we investigated their impact on the odds ratio of year of resuscitation. Analyses were performed according to initial rhythm (shockable versus nonshockable) and AED use. Rates of survival with favorable neurologic outcome after out-of-hospital cardiac arrest increased significantly (N=6133, 16.2% to 19.7%; P for trend=0.021), although solely in patients presenting with a shockable initial rhythm (N=2823; 29.1% to 41.4%; P for trend<0.001). In this group, survival increased at each stage but was strongest in the prehospital phase (odds ratio, 1.11 [95% CI, 1.06-1.16]). Rates of AED use almost tripled during the study period (21.4% to 59.3%; P for trend <0.001), thereby decreasing time from emergency call to defibrillation-device connection (median, 9.9 to 8.0 minutes; P<0.001). AED use statistically explained increased survival with favorable neurologic outcome by decreasing the odds ratio of year of resuscitation to a nonsignificant 1.04. CONCLUSIONS: Increased AED use is associated with increased survival in patients with a shockable initial rhythm. We recommend continuous efforts to introduce or extend AED programs.

Implantable cardioverter-defibrillators have reduced the incidence of resuscitation for out-of-hospital cardiac arrest caused by lethal arrhythmias.

BACKGROUND: Over the last decades, a gradual decrease in ventricular fibrillation (VF) as initial recorded rhythm during resuscitation for out-of-hospital cardiac arrest (OHCA) has been noted. We sought to establish the contribution of implantable cardioverter-defibrillator (ICD) therapy to this decline. METHODS AND RESULTS: Using a prospective database of all OHCA resuscitation in the province North Holland in the Netherlands (Amsterdam Resuscitation Studies [ARREST]), we collected data on all patients in whom resuscitation for OHCA was attempted in 2005-2008. VF OHCA incidence (per 100 000 inhabitants per year) was compared with VF OHCA incidence data during 1995-1997, collected in a similar way. We also collected ICD interrogations of all ICD patients from North Holland and identified all appropriate ICD shocks in 2005-2008; we calculated the number of prevented VF OHCA episodes, considering that only part of the appropriate shocks would result in avoided resuscitation. VF OHCA incidence decreased from 21.1/100 000 in 1995-1997 to 17.4/100 000 in 2005-2008 (P<0.001). Non-VF OHCA increased from 12.2/100 000 to 19.4/100 000 (P<0.001). VF as presenting rhythm declined from 63% to 47%. In 2005-2008, 1972 ICD patients received 977 shocks. Of these shocks, 339 were caused by a life-threatening arrhythmia. We estimate that these 339 shocks have prevented 81 (minimum, 39; maximum, 152) cases of VF OHCA, corresponding with 33% (minimum, 16%; maximum, 63%) of the observed decline in VF OHCA incidence. CONCLUSIONS: The incidence of VF OHCA decreased over the last 10 years in North Holland. ICD therapy explained a decrease of 1.2/100 000 inhabitants per year, corresponding with 33% of the observed decline in VF OHCA.

The effect of extrinsic motivation on cycle time trial performance.

PURPOSE: Athletes occasionally follow pacing patterns that seem unreasonably aggressive compared with those of prerace performances, potentially because of the motivation provided by competition. This study evaluated the effect of extrinsic motivation on cyclists' time trial performance. METHODS: Well-trained recreational cyclists (N=7) completed four 1500-m laboratory time trials including a practice trial, two self-paced trials, and a trial where a monetary reward was offered. Time, total power output, power output attributable to aerobic and anaerobic metabolic sources, VO2, and HR were measured. RESULTS: The time required for the second, third, and last (extrinsically motivated) time trials was 133.1 +/- 2.1, 134.1 +/- 3.4, and 133.6 +/- 3.0 s, respectively, and was not different (P>0.05). There were no differences for total (396 +/- 19, 397 +/- 23, and 401 +/- 17 W), aerobic (253 +/- 12, 254 +/- 10, and 246 +/- 13 W), and anaerobic (143 +/- 14, 143 +/- 21, and 155 +/- 11 W) power output. The highest VO2 was not different over consecutive time trials (3.76 +/- 0.19, 3.73 +/- 0.16, and 3.71 +/- 0.22 L x min(-1)). When ranked by performance, without reference to the extrinsic motivation (131.9 +/- 2.4, 133.4 +/- 2.4, and 135.4 +/- 2.5 s), there was a significant difference for the first 100 m and from 100 to 300 m in power output, with a larger total power (560 +/- 102, 491 +/- 82, and 493 +/- 93; and 571 +/- 94, 513 +/- 41, and 484 +/- 88 W) and power attributable to anaerobic sources (446 +/- 100, 384 +/- 80, and 324 +/- 43; and 381 +/- 87, 383 +/- 90, and 289 +/- 91 W) for the fastest trial. CONCLUSION: Extrinsic motivation did not change the time trial performance, suggesting that 1500-m performance is extremely stable and not readily changeable with simple external motivation. The results suggest that spontaneous improvement in performance for time trials of this duration is attributable to greater early power output, which is primarily attributable to anaerobic metabolic sources.