How does smoking harm the heart?

Smoking and prognosis after acute myocardial infarction in the thrombolytic era (Israeli Thrombolytic National Survey)

OBJECTIVES

This study sought to compare the relation between smoking and the 30-day and 6-month outcome after acute myocardial infarction in an Israeli nationwide survey.

BACKGROUND

Studies before and during the thrombolytic era reported similar or lower early mortality after acute myocardial infarction in smokers than in nonsmokers. This finding is intriguing and may be misleading because numerous epidemiologic studies have clearly shown that smoking is an independent risk factor for atherosclerosis, myocardial infarction and death.

METHODS

The study cohort comprised 999 consecutive patients with an acute myocardial infarction from a prospective nationwide survey conducted during January and February 1994 in all coronary care units operating in Israel. The prognosis of 367 patients (37%) who were smokers (current smokers and those who smoked up to 1 month before admission) was compared with that of 632 nonsmokers (past smokers or those who never smoked).

RESULTS

Smokers were on average 10 years younger and were more frequently men and patients with a family history of coronary heart disease and inferior infarction and less frequently patients with a previous infarction or a history of angina, hypertension and diabetes than nonsmokers. Smokers also had a lower incidence of congestive heart failure on admission or during the hospital period. Thrombolytic therapy (49% vs. 40%, p < 0.01) and aspirin (89% vs. 80%, p < 0.001) were administered more frequently in smokers than nonsmokers. The crude 30-day (6.0% vs. 15.7%) and cumulative 6-month (7.9% vs. 21.5%) mortality rates were significantly lower (p < 0.0001 for both) in smokers than nonsmokers, respectively. However, after adjustment for age, baseline characteristics, thrombolytic therapy and invasive coronary procedures, the lower 30-day (odds ratio [OR] 0.75, 95% confidence interval [CI] 0.43 to 1.29, p = 0.30) and 6-month (hazard ratio 0.84, 95% CI 0.54 to 1.30, p = 0.42) mortality rates in smokers and nonsmokers were not significantly different. The model had a power of 0.80 for OR 0.50, with alpha 0.1.

CONCLUSIONS

In our nationwide survey, the seemingly better prognosis of smokers early after acute myocardial infarction was no longer evident after adjustment for baseline and clinical variables and may be explained by their younger age and a more favorable risk profile. Smokers develop acute myocardial infarction a decade earlier than nonsmokers. Efforts to lower the prevalence of smoking should continue.

Effect of reperfusion modality on outcome in nonsmokers and smokers with acute myocardial infarction (a Primary Angioplasty in Myocardial Infarction [PAMI] substudy). PAMI Investigators

We analyzed the 395 patients randomized into the Primary Angioplasty in Myocardial Infarction (PAMI) trial to receive tissue plasminogen activator (tPA) or to undergo primary percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI). Of these, 168 were current smokers and 128 had never smoked. Univariate analyses of baseline characteristics and outcome, including death, recurrent AMI, and recurrent ischemia, were done by chi-square analysis. Multivariate stratified analysis was then performed controlling for age and gender, which were found to be confounders of outcome. The combined in-hospital outcomes of death, recurrent AMI, and recurrent ischemia were similar for smokers and nonsmokers (p = 0.12). When stratified according to treatment modality, non-smokers treated with PTCA had a lower frequency of death and nonfatal recurrent AMI (7% vs 18%; p = 0.05), in-hospital ischemia (11% vs 33%; p = 0.004), or the combined event (13% vs 40%; p = 0.001). At 6 months, nonsmokers treated with PTCA continued to have a lower incidence of death or nonfatal recurrent AMI (11% vs 24%; p = 0.07) compared with tPA. Conversely, in smokers, the treatment strategy did not significantly affect hospital outcomes: recurrent ischemia (12% vs 23%; p = 0.07), death and recurrent AMI (6% vs 8%; p = 0.55), or the combined event (15% vs 25%; p = 0.12). The statistical significance of these associations was maintained when multivariate analysis controlling for age and gender was used. Thus, nonsmokers presenting with AMI had a significantly better outcome when treated with primary angioplasty; these differences were not seen in smokers.

Significance of smoking in patients receiving thrombolytic therapy for acute myocardial infarction. Experience gleaned from the International Tissue Plasminogen Activator/Streptokinase Mortality Trial

BACKGROUND

Despite the fact that smoking is a well-established risk factor for the development of coronary artery disease, some investigators have noted that hospital mortality after acute myocardial infarction is lower in patients who smoke than in nonsmoking patients. To evaluate the association of smoking with mortality during hospitalization after thrombolytic therapy and 6 months afterward, we analyzed the results of the International Tissue Plasminogen Activator/Streptokinase Mortality Trial.

METHODS AND RESULTS

Patients were divided into three groups: nonsmokers (those who never smoked), ex-smokers, and active smokers. Multivariate and univariate comparisons were made with respect to baseline characteristics and clinical outcome. There were 2,366 nonsmokers, 2,244 ex-smokers, and 3,649 active smokers. The baseline characteristics of nonsmoking patients differed significantly from the ex-smokers and active smokers. The nonsmoking group included more women than the ex-smokers or active smokers (45% versus 10.6% and 17.6%, respectively), was older (67 +/- 10 years versus 64 +/- 10 years and 58 +/- 11 years), had a higher rate of diabetes mellitus (16.3% versus 11.1% and 7.5%), and had a worse Killip class at admission. Nonsmoking patients and ex-smokers experienced more in-hospital reinfarction than active smokers (4.7% and 5% versus 2.7%, p < 0.0001, respectively). Nonsmokers experienced more in-hospital shock than the ex-smokers or active smokers (9.2% versus 6.4% and 5.8%, p < 0.0001), stroke (1.9% versus 1.8% and 0.8%, p < 0.0001), and bleeding (7.2% versus 6.5% and 4.4%, p < 0.0001). They also experienced a higher in-hospital and 6-month mortality (12.8% and 17.6%) than ex-smokers (8.2% and 12.1%) or active smokers (5.4% and 7.8%) (p < 0.0001). A multivariate analysis accounting for all baseline characteristics demonstrated a significant association between nonsmoking and increased hospital mortality, with an odds ratio of 1.42 (confidence limits, 1.15-1.72). Among active smokers, there was a nonsignificant trend for mortality rates to decrease with increasing numbers of cigarettes smoked per day.

CONCLUSIONS

This retrospective analysis indicates that smokers receiving thrombolytic therapy after acute myocardial infarction have significantly better hospital and 6-month outcome than nonsmokers or ex-smokers. However, smokers sustained their infarction at a significantly earlier age than nonsmokers, and strenuous efforts should continue to be made to decrease the incidence of new and continued smoking.

Gender differences in platelet count and its association with cigarette smoking in a large cohort in Israel

Cigarette smoking has an effect on platelet function and aggregation although the sensitivity of platelet count in reflecting this phenomenon is not known. The association of platelet count with smoking habits was examined in a cohort of 5017 Israeli industrial workers aged 20-64 years. Males had a significantly lower age-adjusted mean platelet count than females (225,600 vs 247,800/microliters; p less than 0.001). Female smokers had lower platelet counts than non-smokers (231,000 for heavy vs 252,000 for never smokers) with a strong dose-response relationship (p less than 0.0001), whereas among males platelet count was slightly higher in smokers (224,000 for non-smokers vs 227,000 for heavy smokers; p = 0.243). The difference in platelet count between the sexes remained almost identical after controlling for smoking status and hematocrit. In multiple regression analysis, the negative association between smoking and platelet count in women remained highly significant (p less than 0.001) after controlling for ethnic origin, alcohol consumption, body mass, hematocrit, cholesterol and HDL-cholesterol, whereas for males the slight positive association was not significant. The reduced platelet count observed in males compared with females and in female smokers, suggests that platelet count may reflect sex differences in hemostasis and the effects of smoking on the hemostatic system. This may have implications for the mechanisms underlying the pathogenesis of ischemic heart disease and should be explored further.

The risk of myocardial infarction after quitting smoking in men under 55 years of age

We assessed the effect of quitting cigarette smoking on the incidence of nonfatal myocardial infarction in men under the age of 55 in a case-control study of 1873 men with first episodes of myocardial infarction and 2775 controls. For "current" smokers (men who had smoked in the previous year) as compared with those who had never smoked, the estimated relative risk of myocardial infarction, adjusted for age, was 2.9 (95 per cent confidence interval, 2.4 to 3.4). Among exsmokers (those who had last smoked at least one year previously), the relative-risk estimate declined to a value close to unity for those who had abstained for at least two years; the estimate was 2.0 (1.1 to 3.8) for men who had abstained for 12 to 23 months, and the estimates were about 1.0 for men who had abstained for longer intervals. The results were unchanged by allowance for multiple potential confounding factors. A similar pattern was apparent among exsmokers who had smoked heavily for many years; among those predisposed to a myocardial infarction because of family history, hypertension, or other risk factors; and among those with no apparent predisposition. The results suggest that the risk of myocardial infarction in cigarette smokers decreases within a few years of quitting to a level similar to that in men who have never smoked.

Italian multicenter study on reversible cerebral ischemic attacks: III--Influence of age and risk factors on cerebrovascular atherosclerosis

The influence of age and other risk factors (history of hypertension and diabetes, cigarette smoking, dyslipidemia) on cerebral atherosclerosis was studied in 462 patients with RIA who had cerebral angiography. The degree of atherosclerosis was quantified using extracranial and intracranial cerebrovascular scores (ECS, ICS) based on the number and severity of the lesion in 11 extracranial and 21 intracranial arterial segments. Thirty-six percent of the patients under age 45 had a normal angiogram compared with 17% of the patients over 45. In the subgroup of patients with abnormal angiogram the mean ECS and ICS vascular scores were not significantly different in the two age groups. Cigarette smoking was the only risk factor to show a strong association with the extracranial score, and it was independent of the effect of age and other risk factors.