Lifting the smoke-screen: the enigma of better outcome in smokers after myocardial infarction

beta-carotene attenuates the paradoxical effect of tobacco smoke on the mortality of rats after experimental myocardial infarction

The objective of this study was to investigate the effects of exposure to tobacco smoke (ETS) in rats that were or were not supplemented with dietary beta-carotene (BC), on ventricular remodeling and survival after myocardial infarction (MI). Rats (n = 189) were allocated to 4 groups: the control group, n = 45; group BC administered 500 mg/kg diet, n = 49, BC supplemented rats; group ETS, n = 55, rats exposed to tobacco smoke; and group BC+ETS, n = 40. Wistar rats weighing 100 g were administered one of the treatments until they weighed 200 to 250 g (approximately 5 wk). The ETS rats were exposed to cigarette smoke for 30 min 4 times/d, in a chamber connected to a smoking device. After reaching a weight of 200-250 g, rats were subjected to experimental MI (coronary artery occlusion) and mortality rates were determined over the next 105 d. In addition, echocardiographic, isolated heart, morphometrical, and biochemical studies were performed. Mortality data were tested using Kaplan-Meyer curves and other data by 2-way ANOVA. Survival rates were greater in the ETS group (58.2%) than in the control (33.3%) (P = 0.001) and BC+ETS rats (30.0%) (P = 0.007). The groups did not differ in the other comparisons. Left ventricular end-diastolic diameter normalized to body weight was greater and maximal systolic pressures were lower in the ETS groups than in non-ETS groups. Previous exposure to tobacco smoke induced a process of cardiac remodeling after MI. There is a paradoxical protector effect with tobacco smoke exposure, characterized by lower mortality, which is offset by BC supplementation.

Depression and smoking in coronary heart disease

OBJECTIVE

This review examines the relationship between depression and smoking in coronary heart disease (CHD). It summarizes relevant findings from general population and smoking cessation studies and discusses the few studies that have investigated whether smoking confounds, mediates, or moderates the effect of depression on cardiac morbidity and mortality.

METHODS

Qualitative review of research literature.

RESULTS

Although many studies of the prognostic importance of depression in CHD have adjusted for smoking, there is no convincing evidence that smoking actually confounds the relationship between depression and CHD. There is also no evidence that smoking moderates this relationship. There is, however, limited evidence that smoking may partially mediate the effect of depression on morbidity and mortality in CHD.

CONCLUSION

We need more research on the relationship between depression and smoking in CHD to develop a more complete model of the mechanisms linking depression to cardiac morbidity and mortality.

Case fatality after an acute cardiac event: the effect of smoking and alcohol consumption

The objective of this study was to use a population-based register of acute cardiac events to investigate the association between survival after an acute event and history of smoking and alcohol consumption. The population was all residents of the Lower Hunter Region of Australia aged 25 to 69 years who suffered myocardial infarction or sudden cardiac death between 1986 and 1994. Among 10,170 events, 2504 resulted in death within 28 days. After adjusting for sex, age and medical history, current smokers had a similar risk of dying after an acute cardiac event to never-smokers [odds ratio (OR)=1.10, 95% confidence interval (CI) 0.94-1.29]. People who consumed more than 8 alcoholic drinks per day on more than 2 days per week (OR=1.93, 95% CI 1.39-2.69) and former moderate to heavy drinkers (OR=4.59, 95% CI 3.65-5.76) were more likely to die than people who were nondrinkers. The results of this large community study, suggesting no effect of smoking on case fatality and an increased risk of death after an acute cardiac event for heavy drinkers and former moderate to heavy drinkers, highlight the importance of a population view of case fatality. These results can also shed some light on reasons for the paradoxical results from clinical trials.

Current smokers develop more posterior myocardial infarctions probably due to increased tendency to thrombosis

This investigation was carried out to determine whether smokers developed smaller infarcts as assessed by peak enzyme levels and also to what extent smoking could modify infarct localization. The study included 753 patients, of whom 351 had no history of previous coronary heart disease (CHD) (angina pectoris and/or myocardial infarction (MI)). The investigation was designed as an exposed (smoking) versus non-exposed (non-smoking) cohort study. Outcome was infarct size, posterior versus non-posterior MI and non-Q-wave versus Q-wave infarcts. In the total cohort of patients, 312 (41%) were smokers, the corresponding number in the restricted cohort of patients without a previous CHD (CHD-0-pts) was 169 (48%). Smokers were younger than non-smokers, and more of them were males. It was found that infarct size was similar in smokers and in non-smokers (crude and adjusted effects). Crude effects showed that smokers developed significantly more posterior infarcts than non-smokers; odds ratio (OR) for developing a posterior MI was 1.95 (2p < 0.001) (all patients) and 2.34 (2P < 0.001) (CHD-0-pts), respectively. After adjusting for confounders (logistic regression model), OR in the two groups was 1.24 (2p = 0.256) and 1.95 (2p = 0.01), respectively. The study shows that current smokers were younger, and indicates that in those without a previous CHD, significantly more of them developed a posterior MI.

Smoking status and outcome after primary coronary angioplasty for acute myocardial infarction

BACKGROUND

Because of the increased propensity of intracoronary thrombi to form in cigarette smokers, percutaneous transluminal angioplasty (PTCA) for acute myocardial infarction (AMI) may be less effective in smokers. We sought to determine the impact of smoking status on outcome after PTCA for AMI.

METHODS

Patients enrolled in the GUSTO IIb Angioplasty Substudy were randomly assigned to receive PTCA or tissue-plasminogen activator (tPA) for AMI. The interaction of smoking status (nonsmokers = 344, former smokers = 294, current smokers = 490) and treatment strategy with the occurrence of death, nonfatal reinfarction, or nonfatal, disabling stroke at 30 days was analyzed. Procedural success (residual stenosis <50% and Thrombolysis in Myocardial Infarction [TIMI] flow grade 3) was also analyzed for patients who underwent PTCA (n = 444).

RESULTS

Among patients who underwent PTCA, nonsmokers had worse percent stenosis of the culprit lesion before reperfusion (P =.03) and more often had TIMI flow grade 0 (P <.05). Procedural success was more common in smokers (65.6%) than in former smokers (53.3%) and nonsmokers (52. 4%; P =.02), reflecting a higher rate of postprocedure TIMI 3 flow. PTCA was associated with a better 30-day outcome than tPA for current smokers (odds ratio [95% confidence interval] = 0.41 [0.19 to 0.88]), with a similar trend for former smokers (0.73 [0.34 to 1. 58]) and nonsmokers (0.77 [0.42 to 1.40]). At 6 months, smokers randomly assigned to PTCA also had fewer deaths and reinfarction (0. 58 [0.31 to 1.07]).

CONCLUSIONS

Although smoking status affects angiographic variables before and after PTCA for AMI, PTCA is associated with a better 30-day outcome than tPA regardless of smoking status and should be considered when readily available.

Admission clinical and electrocardiographic characteristics predicting an increased risk for early reinfarction after thrombolytic therapy

BACKGROUND

This study assessed the ability of clinical and electrocardiographic variables routinely obtained on admission to identify patients with acute myocardial infarction treated with thrombolytic therapy at risk of early reinfarction.

METHODS AND RESULTS

The study included 2602 patients who received thrombolytic therapy for acute myocardial infarction. Baseline demographic variables and admission clinical and electrocardiographic variables were compared between patients with and without reinfarction. Multivariable logistic regression technique was used and included recurrent infarction as the dependent variable, and baseline demographic, clinical, and electrocardiographic variables as independent variables. History of hypertension (odds ratio [OR] 1.52, 95% confidence interval [CI] 1.00 to 2.31) and diabetes mellitus (OR 1.59, 95% CI 1.00 to 2.53) were associated with a higher risk, and current smoking was associated with a lower risk (OR [no versus yes] 1.64, 95% CI 1.05 to 2.58) of early hospital reinfarction. Distortion of the terminal portion of the QRS complex (OR 1.86, 95% CI 1.20 to 2.87) and absence of abnormal Q waves on admission (OR 1.54, 95% CI 0.98 to 2.43) were associated with increased risk of early reinfarction.

CONCLUSIONS

A simple electrocardiographic sign is a reliable predictor of early reinfarction among patients who receive thrombolytic therapy for acute myocardial infarction.

Smokers undergoing percutaneous coronary revascularization present with fewer narrowings in the target coronary artery

Among patients undergoing percutaneous coronary revascularization, cigarette smoking remained associated with fewer lesions in the target artery even after adjusting for age, extent of coronary artery disease, diabetes mellitus, and hypertension. These findings support the hypothesis that smokers have less active, yet more active, coronary artery disease.

Is preconditioning by nicotine responsible for the better prognosis in smokers with acute myocardial infarction?

Cigarette smoking is a well-known risk factor for acute myocardial infarction and sudden death. However, a history of smoking consistently has been associated with better hospital outcome in patients with acute myocardial infarction. The mechanism for the better outcome in smokers is not clear. It has been suggested that nicotine may have a "preconditioning-like" effect. This study assesses whether nicotine attenuates myocardial infarct size. Anesthetized rabbits were randomized to receive infusion of nicotine 80 micrograms/kg (n = 13), or saline (n = 12) over 10 min. Twenty minutes after termination of infusion all rabbits underwent 30 min of coronary artery occlusion and 4 h of reperfusion. Risk zone was assessed by blue dye and infarct size by tetrazolium staining. Nicotine did not affect regional myocardial blood flow 15 min after treatment, during occlusion or during reperfusion. Heart rate and mean systemic blood pressure were similar between the groups. Nicotine serum levels during occlusion were 9.5-22.0 ng/ml in the treated group, which are comparable to levels found in human smokers. No differences were found in the risk zone of nicotine compared to control rabbits (26 +/- 2% vs. 23 +/- 2% of the left ventricle, respectively), or infarct size (31 +/- 5% vs. 37 +/- 4% of risk zone). Since no effect on infarct size was found, a third group receiving higher dose of nicotine, 320 micrograms/kg (n = 6), was added. Infarct size was not different from the control group (39 +/- 6% of risk zone). Nicotine, given intravenously before ischemic insult, does not protect the myocardium. A "preconditioning-like" effect of nicotine is probably not the mechanism of reduced mortality in smoking patients with myocardial infarction.