International Journal of Cardiology 171 (2014) 101–102

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Editorial

The obesity paradox in cardiac arrest patients Athanasios Chalkias 1, Theodoros Xanthos ⁎,1 National and Kapodistrian University of Athens, Medical School, MSc “Cardiopulmonary Resuscitation”, Athens, Greece

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Article history: Received 6 September 2013 Accepted 30 November 2013 Available online 6 December 2013 Keywords: Cardiac arrest Cardiopulmonary resuscitation Outcome Obesity paradox

a b s t r a c t Evidence from clinical cohorts indicates an obesity paradox in overweight and obese patients who seem to have a more favorable short-term and long-term prognosis than leaner patients. Although obese cardiac arrest victims are theoretically more difficult to be resuscitated due to difficulties in providing adequate chest compressions, ventilation, and oxygenation, research so far has shown that there is an obesity paradox in cardiac arrest. © 2013 Elsevier Ireland. Ltd All rights reserved.

1. Introduction Obesity has an epidemic development in industrialized countries; at least 1.1 billion adults are overweight and 312 million are obese, worldwide. A relationship between obesity and an increased mortality rate exists as overall death rates increase linearly with increasing adiposity [1]. In addition, obesity has been implicated as one of the major risk factors for cardiovascular disease and congestive heart failure [2]. In this issue of International Journal of Cardiology, Noheria et al. provide evidence that sudden cardiac death in middle-aged adults is distinguishable from older subjects by higher rates of obesity, suggesting a central role for the increased adiposity in the pathophysiology of cardiac arrest in this age group [3]. However, evidence from clinical cohorts indicates an obesity paradox in overweight and obese patients who seem to have a more favorable short-term and long-term prognosis than leaner patients [4,5]. In the last decades there have been growing evidence that moderately elevated body mass index (BMI) is not only associated with excess mortality, but it might be also protective in critically ill patients. Furthermore, high BMI was found to have a protective effect on mortality in patients with ST-segment elevation myocardial infarction, unstable angina and non-ST-segment elevation myocardial infarction,

⁎ Corresponding author at: National and Kapodistrian University of Athens, Medical School, MSc “Cardiopulmonary Resuscitation”, Hospital “Henry Dunant”, 107 Mesogion Av., 115 26 Athens, Greece. Tel.: +30 210 6972144; fax: +30 210 6972396. E-mail address: [email protected] (T. Xanthos). 1 The author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation. 0167-5273/$ – see front matter © 2013 Elsevier Ireland. Ltd All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.11.122

or both [6], as well as in patients with heart failure [7]. The increased BMI may confer protection against endotoxin and inflammatory cytokines by increasing the production of “buffering” lipoproteins. However, other studies question the existence of obesity paradox. Obesity causes hypertension, sleep apnea, and adiposity of the heart which, together with the structural vascular and cardiac adaptations that trigger ventricular hypertrophy and electrophysiological changes, increase the risk for heart failure, arrhythmias, and sudden cardiac death. In addition, although overweight and obese individuals are characterized by increased production of several cytokines which are implicated in the induction of endothelial cell proliferation and migration, aiding the vascular healing process, some of these cytokines have also been shown to cause endothelial cell dysfunction in pig coronary arteries [8]. Interestingly, although obese cardiac arrest victims are more difficult to be resuscitated due to difficulties in providing effective chest compressions and adequate ventilation-oxygenation, recent data suggest that an obesity paradox may also exist in such patients. Testori et al. investigated the direct effect of obesity on outcome after cardiac arrest and found that although BMI may have no direct influence on sixmonth survival, patients with moderately elevated BMI may have a better neurological prognosis [1]. Also, Bunch et al. described a lower long-term survival in patients of normal or low weight after witnessed out-of-hospital cardiac arrest due to ventricular fibrillation. Nevertheless, Bunch et al. reported that the success of biphasic defibrillation or the rate of return of spontaneous circulation (ROSC) was not influenced by body weight among survivors [9]. Of note, White et al. reported that body weight affects neither the defibrillation nor the resuscitation or survival in patients with out-of-hospital cardiac arrest treated with a biphasic waveform defibrillator [10], further complicating the obesitysurvival association in this clinical setting.

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But what happens in younger individuals? In a recent large multicenter registry study, Srinivasan et al. reported that childhood obesity was associated with a lower rate of survival to hospital discharge after in-hospital cardiac arrest, while the outcomes of children who were underweight were at least as good as those of children with normal weights [11]. The authors concluded that the aforementioned outcome was associated with the anatomic and physiologic effects of obesity on cardiopulmonary resuscitation, the much higher defibrillation doses, and the plasma concentrations of highly water-soluble CPR medications which may was substantially higher in obese children and therefore potentially toxic. These findings are supported by other studies demonstrating that childhood obesity is generally associated with increased morbidity and mortality rates [12]. However, these results cannot be extrapolated to adults. Today, the truth behind the obesity paradox remains unknown and further studies are necessary in order to clear the foggy landscape around it. Considering that sudden cardiac arrest rates increase with age, as well as that middle-aged adults may comprise a significant proportion of cardiac arrest cases in the community, the need for a clinical and investigational focus on sudden cardiac death prediction and prevention in different age groups is imperative. Other issues that have to be clarified are the effect of obesity on survival rates with respect to the etiology of cardiac arrest and the effect of post-resuscitation targeted temperature management on obese patients with ROSC. Only high quality research will further help identify a clearer understanding of the underlying mechanisms and impact of the obesity paradox in cardiac arrest patients. Acknowledgments Nothing to acknowledge.

References [1] Testori C, Sterz F, Losert H, et al. Cardiac arrest survivors with moderate elevated body mass index may have a better neurological outcome: a cohort study. Resuscitation 2011;82:869–73. [2] Kenchaiah S, Evans JC, Levy D, et al. Obesity and the risk of heart failure. N Engl J Med 2002;347:305–13. [3] Noheria A, Teodorescu C, Uy-Evanado A, et al. Distinctive profile of sudden cardiac arrest in middle-aged vs. older adults: a community-based study. Int J Cardiol 2013;168:3495–9. [4] Lavie CJ, Milani RV, Ventura HO. Obesity and cardiovascular disease: risk factor, paradox, and impact of weight loss. J Am Coll Cardiol 2009;53:1925–32. [5] Romero-Corral A, Montori VM, Somers VK, et al. Association of bodyweight with total mortality and with cardiovascular events in coronary artery disease: a systematic review of cohort studies. Lancet 2006;368:666–78. [6] Diercks DB, Roe MT, Mulgund J, et al. The obesity paradox in non-ST-segment elevation acute coronary syndromes: results from the can rapid risk stratification of unstable angina patients suppress adverse outcomes with early implementation of the American College of Cardiology/American Heart Association Guidelines Quality Improvement Initiative. Am Heart J 2006;152:140–8. [7] Fonarow GC, Srikanthan P, Costanzo MR, Cintron GB, Lopatin M. ADHERE Scientific Advisory Committee and Investigators: an obesity paradox in acute heart failure: analysis of body mass index and in hospital mortality for 108,927 patients in the Acute Decompensated Heart Failure National Registry. Am Heart J 2007;153:74–81. [8] Davenport DL, Xenos ES, Hosokawa P, Radford J, Henderson WG, Endean ED. The influence of body mass index obesity status on vascular surgery 30-day morbidity and mortality. J Vasc Surg 2009;49:140–7 [147.e1; discussion 147]. [9] Bunch TJ, White RD, Lopez-Jimenez F, Thomas RJ. Association of body weight with total mortality and with ICD shocks among survivors of ventricular fibrillation in out-of-hospital cardiac arrest. Resuscitation 2008;77:351–5. [10] White RD, Blackwell TH, Russell JK, Jorgenson DB. Body weight does not affect defibrillation, resuscitation, or survival in patients with out-of-hospital cardiac arrest treated with a nonescalating biphasic waveform defibrillator. Crit Care Med 2004;32:S387–92. [11] Srinivasan V, Nadkarni VM, Helfaer MA, Carey SM, Berg RA, American Heart Association National Registry of Cardiopulmonary Resuscitation Investigators. Childhood obesity and survival after in-hospital pediatric cardiopulmonary resuscitation. Pediatrics 2010;125:e481–8. [12] Weiss R, Dziura J, Burgert TS, et al. Obesity and the metabolic syndrome in children and adolescents. N Engl J Med 2004;350:2362–74.

The obesity paradox in cardiac arrest patients.

Evidence from clinical cohorts indicates an obesity paradox in overweight and obese patients who seem to have a more favorable short-term and long-ter...
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