According to the Get with the Guidelines (GWTG)-Resuscitation registry, overall survival after in-hospital cardiac arrest (IHCA) has improved significantly during the past decade [1] [2] . Survival to discharge rates increased from 13.7% in 2000 to 22.3% in 2009. The most important explanations for the apparent improvement are advances in the management of acute myocardial infarction and heart failure that may have led to a decline in the proportion of IHCA of which the initial rhythm is ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) [1] - [4] . Therefore, a good outcome is associated with cardiac morbidity, the event being witnessed, and the patient being monitored [3] - [8] . However, the patient outcome after IHCA in general ward remains poor with only 3% - 14% of patients undergoing cardiopulmonary resuscitation (CPR) being able to survive and be discharged [3] [9] [10] . Previous reports indicated that patients with cardiac arrest in critical care areas had a better outcome than those in general wards because of different policies, manpower, disease entities, staff training and experience in response to emergency situations [5] - [11] . Established outcome predictors for patients with IHCA such as adequate monitoring may not be easily applied to those in the general wards. To our knowledge, few studies have focused on factors influencing outcome of patients with IHCA in general wards [9] [10] . The goal of this study was to report the outcomes of adult patients with IHCA in the general wards of an Asian medical center in comparison to those in western countries.

We describe the outcomes of CPR for patients with IHCA in general wards. The overall patient survival was 5.1%, while 1.1% of all patients showed favorable neurological outcomes. The findings of the current study demonstrated several previously unreported factors that had significant impact on the survival of patients with IHCA in the pre-arrest setting. For instance, a reduced chance of ROSC was noted in the presence of a CCI ≥ 9. Moreover, the probability of successful resuscitation and survival to discharge decreased as the CCI score increased. Furthermore, cardiac comorbidity before admission was independently associated with a low possibility of ROSC. Finally, a deteriorated disease course was independently associated with an unfavorable patient survival.

According to the national registry of cardiopulmonary resuscitation (NRCPR), patients who underwent CPR in general inpatient area had a 14% probability of survival to discharge [3] . The majority of studies report better outcomes for patient with IHCA occurring in critical care areas than those encountered in wards [3] [5] [6] [11] . The possible explanations included the monitored and witnessed status of the patients, immediate availability of personnel and medications for conducting effective ACLS, and the nature of patients in a critical care setting. For instance, patients with cardiac morbidity in the coronary care unit are likely to develop cardiac arrests secondary to readily reversible dysrhythmias that may contribute to a relatively good prognosis. The data from NRCPR showed that 77.7% of overall patients were being monitored without specifically referring to patients in the general wards [3] . By contrast, in our general ward population, only 16% of patients were being monitored before arrest, even though 54.6% of patients had abnormal vital signs according to the definition of deteriorated disease courses. The inherent limitations of general wards and inadequate monitoring, therefore, may be a contributor to unfavorable patient outcome.

Cardiac arrest occurs in a heterogeneous group of patients commonly hospitalized for serious comorbidities. Indeed, the data of GWTG-Resuscitation registry showed that the absence of renal insufficiency, hepatic insufficiency, sepsis, and malignancy prior to the arrest were associated with favorable neurological survival [5] . In this study, CCI and the total number of comorbidities before admission were used as the indices of severity to evaluate the correlation between comorbidities before admission and patient outcome. However, the present study demonstrated no significant association between patient survival and the two indices with the exception of a reduced probability of ROSC in the presence of a CCI ≥ 9. On the other hand, stratification of the data with a more detailed CCI showed a trend indicative of an association of decreased probability of successful resuscitation and discharge survival with an elevated CCI. Although a high CCI was not a significant discharge outcome predictor in this study, all 36 patients with a CCI ≥ 9 did not survive to hospital discharge. The very low survival

VF = ventricular fibrillation; VT = ventricular tachycardia.

rate may account for its lack of significance as a predictor. Although data from NRCPR suggested that nine pre- existing conditions and the mean number of pre-existing conditions were significantly related to the discharge mortality risk strata [3] , there was no significant relationship between patient survival and the total number of comorbidities before admission in our study. CCI, which is constructed by assigning a weight to each comor- bidity according to the magnitude of the relative risk associated with each condition [14] [15] , has not been pre- viously reported as an outcome predictor of IHCA. In comparison with the assessment of risk associated with a specific disease or the total number of comorbidities, CCI is a more reliable indicator for outcome prediction after IHCA in the pre-arrest setting.

The NRCPR study and that by de Vos et al. revealed that patients with cardiac morbidity had a nearly two- fold increase in survival rate compared with those with non-cardiac morbidity [3] [16] . However, the results of the current study shows that cardiac morbidity was significantly associated with a poorer ROSC rate, contrary to those of previous studies that demonstrated significant association of cardiac morbidity with a higher probability of ROSC and survival rate. In addition to the event locations and inadequate monitoring, another difference of our study from previous reports is the lower prevalence of coronary artery disease at admission (14.8%) in our study population. Previous studies have reported higher prevalence of ischemic heart disease in western countries. Ballew et al. demonstrated that 43% of the study population had coronary artery disease and 31% had a previous myocardial infarction [17] . Herlitz et al. also revealed that 42% of men and 25% of women with IHCA had a previous history of myocardial infarction [18] . The relatively low frequency of ischemic heart disease in this study is comparable to that of an out-of-hospital cardiac arrest study in Japan [19] . Accordingly, it also accounted for the very low incidence (3.9%) of VT/VF as the first documented rhythm in this study. Taken together, it may account for our finding that cardiac morbidity was not a positive predictor for ROSC or survival to hospital discharge in the general wards. On the other hand, according to the data of NRCPR, another significant factor associated with a decreased survival of adult patients with IHCA is resuscitation system errors that has been reported to occur most frequently (up to 40.4%) in non-ICU inpatient areas [20] . In general wards, a lack of manpower, inadequate patient monitorings, late discovery of arrests, or delayed response of the CPR team could occur especially at midnight shift, thereby missing the chance of timely treatment of reversible rhythms such as VT/VF.

Previous reports indicated that the majority (i.e., approximately 50% to 84%) of patients had identifiable serious physiological abnormalities within eight hours preceding IHCA [13] [21] [22] . In our study, 54.6% of patients had abnormal vital signs according to the definition of deteriorated disease course. We also identified five pre-arrest conditions indicative of an extremely poor prognosis with 100% mortality after IHCA episodes in this study. For these high risk patients, placing DNR discussions is of paramount importance in such deterioration conditions. Patients who are unlikely to benefit from CPR should be identified on or during hospital admission and the possibility of DNR orders should be discussed to avoid inappropriate treatment and potential patient suffering.

This study had its limitations. First, our study suffered from the shortcomings of the setting of a single institute and its retrospective nature including inadequate documentation at the time of CPR and incomplete or missing patient records. Second, the sample size of our survival group was relatively small. Finally, the long period covered in this study may have introduced significant confounders that influenced the outcomes.

The overall survival for patients with IHCA in general wards remained poor. Reduced chance of ROSC was noted in the presence of a CCI ≥ 9 as well as the presence of metastatic malignancy and cardiac comorbidity before admission. Moreover, the probability of successful resuscitation and survival to discharge also decreased as CCI score increased. Furthermore, a deteriorated disease course was independently associated with an unfavorable patient survival.

CTK participated in the design of the study and drafted the manuscript. HHC, SCH, CFL, FCC, and CMS participated in the coordination of the study and data collection. CJL, HYC and HHC performed the statistical analysis and interpretation of statistical data. JWL and HYC conceived the study, participated in its design and coordination, and helped draft the manuscript. All authors read and approved the final manuscript.