Long-term survival after resuscitation from cardiac arrest: Cause for optimism and continued efforts
Article Outline
See related article on page 826.
Out-of-hospital cardiac arrest is an immense public health challenge. Although advances in primary prevention have produced some declines in the incidence of cardiac arrest, hundreds of thousands of persons die prematurely each year from sudden cardiac death.1 With the right set of circumstances, a substantial portion of cardiac arrest victims can be successfully resuscitated.2, 3 Consequently, in many communities, considerable resources are being directed toward strengthening the links in the chain of survival and thus improving the odds of successful resuscitation.4
The revealing study by Engdahl et al in this issue of the Journal may provide a glimpse of the consequences of enhanced resuscitation and the possibilities for future improvements in long-term survival. The investigators found that long-term survival after successful resuscitation from cardiac arrest did not differ between the 2 time periods, 1980 to 1991 and 1991 to 1998, in the community of Göteborg, Sweden. On the surface, the result may be considered disappointing; however, several findings of the study deserve comment.
First, although the investigation focused on long-term survival, an even broader perspective offers the best gauge of progress. As the authors report, successful short-term survival (defined as survival to discharge from the hospital) appeared to increase substantially during the latter period (10.3% vs 7.3%). One could hypothesize that these “additional” short-term survivors would not enjoy the same long-term survival. Improvements in prehospital and hospital care could transiently salvage additional lives after cardiac arrest. These additional short-term lives saved, persons who would have died during the earlier period, represent “hearts too sick to live,”5 and they would succumb relatively quickly after discharge from the hospital. However, the results of Göteborg study suggest that, on average, the “additional” survivors of the latter period enjoyed a similar long-term survival. Thus, from a public health perspective, hundreds of person-years were gained during the latter period, which is a cause for optimism.
Second, in terms of long-term survival, advances have occurred in the care of heart disease in the last 2 decades that could benefit survivors of cardiac arrest. Appropriate therapies such as revascularization, implantable cardioverter defibrillators, or pharmacological treatments (lipid lowering, β-blockers, angiotensin-converting enzyme inhibitors, amiodarone, and antiplatelet and anticoagulation therapies) may prevent mortality in groups of persons who survive cardiac arrest. Much of this knowledge came to light in the 1990s. Indeed, several factors associated with better prognosis in this or other studies of long-term survivors demonstrated a favorable temporal trend. However, plenty of opportunities appear to exist to improve care. One would expect that in Göteborg and other communities treatment with proven effective therapies will continue to increase in the future, improving the odds of long-term survival. Thus, there is a need for continued efforts.
Third, all prognostic factors except 1 in this cohort either improved or remained the same. Moreover, several factors associated with lower risk of cardiac arrest or heart disease mortality in other settings also demonstrated a temporal improvement in the Göteborg cohort. The notable and lone exception was the cerebral performance score, which was significantly poorer during the latter period. Why might this be? One explanation is that the survivors during the latter period had more pre-existing clinical morbidity, such as stroke, before the arrest, that would result in a poorer cerebral score after resuscitation. This circumstance, however, was not obvious in the Göteborg cohort. Alternatively, as aforementioned, short-term survival improved in the latter period; perhaps the “additional” survivors contributed to the lower cerebral performance score. Whatever the cause, consideration should be given to how brain and heart function can be preserved after resuscitation. Some evidence suggests that cooling early after resuscitation may improve neurological outcome.6 Other treatments that improve circulation during resuscitation or protect the brain after resuscitation may also contribute to better cerebral function. Again, this points to the need for continued efforts.
The investigators are to be commended for their efforts that combine demographic, emergency medical service, and clinical factors in addressing an important question, although some limitations should be noted. As the authors comment, persons in this cohort included survivors of arrests caused by cardiac and noncardiac disease, although the focus of the study was heart disease. One assumes that mortality was assessed uniformly and completely, although these details are not reported. The study had limited power in detecting clinically important temporal changes in survival. Finally, Göteborg is a single community, although the reported experiences are likely to be representative of other communities. These limitations not withstanding, the study by Engdahl et al provides some interesting results that shed light on this challenging research field. The findings give cause for optimism, yet highlight the need for continued efforts in the care of victims of cardiac arrest.
References
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- . Cardiac resuscitation. N Engl J Med. 2001;344:1304–1313
- Outcomes of rapid defibrillation by security officers after cardiac arrest in casinos. N Engl J Med. 2000;343:1206–1209
- Improving survival from sudden cardiac arrest (the “chain of survival” concept. A statement for health professionals from the Advanced Cardiac Life Support Subcommittee and the Emergency Cardiac Care Committee, American Heart Association). Circulation. 1991;83:1832–1847
- Cummins RO. Quoted by: Eisenberg MS. Life in the balance: emergency medicine and the quest to reverse sudden death. New York: Oxford; 1997. p. 251
- . Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med. 2002;346:549–556
PII: S0002-8703(03)00073-5
doi:10.1016/S0002-8703(03)00073-5
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