BackgroundSmokers have been shown to have lower mortality after acute coronary syndrome than non-smokers. This has been attributed to the younger age, lower co-morbidity, more aggressive treatment and lower risk profile of the smoker. Some studies, however, have used multivariate analyses to show a residual survival benefit for smokers; that is, the "smoker's paradox". The aim of this study was, therefore, to perform a systematic review of the literature and evidence surrounding the existence of the "smoker's paradox".MethodsRelevant studies published by September 2010 were identified through literature searches using EMBASE (from 1980), MEDLINE (from 1963) and the Cochrane Central Register of Controlled Trials, with a combination of text words and subject headings used. English-language original articles were included if they presented data on hospitalised patients with defined acute coronary syndrome, reported at least in-hospital mortality, had a clear definition of smoking status (including ex-smokers), presented crude and adjusted mortality data with effect estimates, and had a study sample of > 100 smokers and > 100 non-smokers. Two investigators independently reviewed all titles and abstracts in order to identify potentially relevant articles, with any discrepancies resolved by repeated review and discussion.ResultsA total of 978 citations were identified, with 18 citations from 17 studies included thereafter. Six studies (one observational study, three registries and two randomised controlled trials on thrombolytic treatment) observed a "smoker's paradox". Between the 1980s and 1990s these studies enrolled patients with acute myocardial infarction (AMI) according to criteria similar to the World Health Organisation criteria from 1979. Among the remaining 11 studies not supporting the existence of the paradox, five studies represented patients undergoing contemporary management.ConclusionThe "smoker's paradox" was observed in some studies of AMI patients in the pre-thrombolytic and thrombolytic era, whereas no studies of a contemporary population with acute coronary syndrome have found evidence for such a paradox.

BackgroundThe term non-specific chest pain (NSCP) is applied to hospitalized patients in order to designate that they neither have an acute coronary syndrome (ACS) nor display evidence of a coronary ischemia. The number of NSCP patients is increasing and comprehensive guidelines specifying their optimal management have not yet been introduced. The objective of this review was to explore the prevalence and prognosis of NSCP versus ACS among patients recruited in consecutive series hospitalized for chest pain suspected to be ACS.MethodsThis is a systematic literature search where three databases were searched from 1990 to 14 November 2011. In addition, one database was searched for Epub ahead of print per 24 March 2012. Three inclusion criteria were applied: 1. documentation of an unselected consecutive series of patients admitted for chest pain, where this review is based upon two groups of patients defined as follows: a) 'ACS/high-risk' and b) NSCP; 2. at least 100 cases with NSCP; and 3. follow-up of hospital readmissions and mortality for at least six months.ResultsA total of 2,204 citations were screened after removal of duplicates. Out of 80 full text articles assessed for eligibility 12 studies were included, comprising 24,829 patients (inter-study range 250 to 13,762), with 11,008 (44%) categorized as NSCP and 13,821 (56%) as 'ACS/high-risk'. The mean one-year total mortality rate among patients with NSCP in nine studies was 3.2% (inter-study range 1.4% to 8.1%), with the highest mortality among patients with pre-existing coronary heart disease (CHD). The mean one-year mortality rate among 'ACS/high-risk' patients was 18.0% (inter-study range 14.0% to 19.9%) in four studies with available data. In six studies the mean one-year readmission rate for patients with NSCP was 17.5% (inter-study range 2.5% to 40%).ConclusionsPatients with NSCP represent a large, heterogeneous and important group. Due to co-existing CHD in nearly 40% of these patients, their prognosis is not necessarily benign. Although their average one-year mortality rate was almost six times lower than those with 'ACS/high-risk', the subset with concomitant CHD had a relatively poor prognosis when compared with NSCP patients without evidence of CHD.

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