Based on GWTG-R and American Hospital Association data, we estimated that approximately 200,000 hospitalized patients are treated for cardiac arrest in the US annually. These estimates suggest that a similar number of Americans receive attempted resuscitation each year from cardiac arrest in-hospital (~200,000/year) and out-of-hospital (~175,000/year) (2
). This is consistent with prior reports estimating the annual incidence of sudden arrhythmic death between 184,000 and 462,000 (1
). Because 21% of adults survive (and often with good neurologic outcome) to hospital discharge following resuscitation for IHCA compared with <8% following resuscitation for out-of-hospital (OHCA), the absolute number of Americans who survive cardiac arrests each year is much higher following IHCA than OHCA (2
). Collectively, our findings support that nearly 400,000 treated cardiac arrests occur in and outside of the hospital. Estimating this national average is important for understanding the burden of cardiac arrest and further underscores the need for sustained serious efforts to address this disease.
There is a paucity of data regarding the incidence of IHCAs in hospitalized patients. A few reports have estimated treated IHCA event rates (3
) and these studies varied substantially in terms of inclusion criteria and study populations. Some studies report the event rate for adult patients in a specific age range (e.g. elderly) or hospital location (e.g. non-ICU setting) (4
) Other reports vary in terms of cumulative event rate at a group of hospitals compared with event rate at individual facilities (3
). The definitions for treated IHCA and event rate also varied widely (5
). Such heterogeneity makes comparisons across studies challenging. Further work is needed to better understand the wide variation in the reported incidence and outcomes of both IHCA and OHCA.(1
In this GWTG-R study, the standardized Utstein-style cardiac arrest data reporting guidelines were used, including consistent definitions and uniform data collection. Our estimates of event rate reflect US registry data from adult patients, in ICU and non-ICU settings, and estimates of event rate that account for individual hospital bed-days (metric commonly used in hospital epidemiology (13
It is important to contextualize our estimate of ~200,000 annual treated IHCA in the US and consider what the parameters should be for the national treated arrest rate. It is unrealistic for the national IHCA rate to be zero, as some arrests are not preventable. Inevitably, as hospitals provide care for critically ill patients, some of the ~200,000 IHCA are expected and consistent with the end of the cycle of life. From a policy standpoint, it is important to understand the IHCA event rate in terms of arrests that are not inevitable but that are preventable.
These potentially avoidable arrests may represent a significant proportion of total estimated IHCA as prior work suggests that approximately 100,000 preventable in-hospital deaths occur annually in the US (24
). An expert panel, medical chart review (of cases from a district general hospital with house staff) demonstrated that 62% of IHCA were potentially preventable (3
). These cases were primarily due to diagnostic errors, delays in responding to abnormal hemodynamic parameters, delays in activating medical personnel, and lack of adherence to resuscitation guidelines/policies. Similarly, other reports using retrospective chart review have illustrated clinical deterioration at least eight hours prior to arrest in up to 84% of hospitalized patients (25
). Variability in do-not-resuscitate (DNR) policies also likely represents differences in preventable IHCA rates as a hospitals’ approach to end of life care may impact which terminally ill patients receive aggressive resuscitation measures compared with comfort care (3
). Overall, to better understand the magnitude of the US IHCA event rate, future work is needed to determine the etiology of arrests (e.g. medical error, differences in DNR policies) that impact the proportion of preventable arrests that can be reduced to improve morbidity and mortality in hospitalized patients. This may also provide insight into some of the variability in IHCA arrest outcomes attributed to arrest time of day/day of the week, (29
) time to defibrillation, (10
) or potentially modifiable process measures.
To evaluate the IHCA event rate over time, we restricted our analysis to the subset of hospitals (n=150) that contributed data every year of the study period, 2003–2007—this excluded hospitals joining GWTG-R after 2003 or those who joined and then discontinued data entry after 2003. The mean event rate (0.92/1000) for this subset was the same as the larger cohort (n=433) and the event rate in this subset was noted to increase annually.
The increase in IHCA event rates is likely multi-factorial and may reflect differences in reporting and classification or an actual increase in arrest events. Although GWTG-R has strict and structured data collection guidelines, there may be differences in data reporting in this subset of hospitals. These hospitals could also be increasingly providing care for sicker patients, changing their strategies for treating critically ill patients, or changing their policies for end of life care (e.g. DNR status, neurologic prognostication, withdrawal of care).
Our finding may also reflect that there have been few recommendations for how to optimally reduce IHCA rates over the past decade. Most of the recent AHA Emergency Cardiovascular Care Cardiopulmonary Resuscitation guidelines (2010)-and those issued during the study time period (2005) focus on treatment strategies for cardiac arrest rather than best practices for prevention of in-hospital cardiac arrest (30
). In addition, two approaches, implementing rapid response teams and improving early identification of patients with do not resuscitate status, have not been shown reduce IHCA rates (8
). Future studies are certainly needed to better understand the factors contributing to IHCA event rates over time.