Behavior of cardiac variables in animals exposed to cigarette smoke

Abstract

Among health hazards caused by smoking, cardiovascular changes stand out. Smoking influences the prevalence of infarction through several mechanisms, such as endothelial dysfunction, greater oxidation of LDL-cholesterol, a reduction in HDL-cholesterol, an increase in the levels of adhesion molecules and fibrinogen, an increase in platelet aggregation, and an increase in the prevalence of vascular spasm 1,2 . English et al 3 were the first to report a close relation between smoking and mortality due to ischemic heart disease, and they were followed by other authors who stressed that association 4,5 . The proposed mechanisms, by which the constituents of cigarette smoke (carbon monoxide, nicotine, tar, and the substances contained in vapor) may cause myocardial infarction, are as follows: thrombosis, formation of atherosclerotic plaque, platelet aggregation, vasoconstriction, hypoxia, and arrhythmia induction 6 . Although the association between the smoking habit and coronary heart disease is universally accepted, little is known about the morphofunctional effects of smoking directly on the heart. Thus, the objective of this study was to assess the behavior of the variables related to myocardial mechanical function and also to in situ heart function of the animals exposed to cigarette smoke. MethodsThe study comprised 51 male Wistar rats weighing between 200 and 250 g divided into 2 groups as follows: control group (C) -formed by 28 animals, receiving the diet routinely used in our laboratory adjusted according to the daily ingestion observed in group S during smoke exposure; and smoking group (S) -formed by 23 animals receiving the unrestricted diet routinely used in our laboratory for 3 months and exposed to tobacco smoke in the last 30 days.The method used was that proposed by Simani et al 7 and implemented by Wang et al 8 to expose the animals to cigarette smoke in a modified incubator. The rats, 5 each time, were placed in the clear chamber connected to the smoking device. Smoke puffs were drawn from a cigarette Objective -To assess the behavior of cardiac variables in animals exposed to cigarette smoke. (C= 3.39 ± 0.4 mm and S= 3.71 ± 0.51 mm, P=0.02). A significant reduction was observed in systolic shortening fraction (C= 56.7 ± 4.2% and S= 53.5 ± 5.3%, P=0.02) and in ejection fraction (C= 0.92 ± 0.02 and S= 0.89 ± 0.04, P=0.01). Methods - Conclusion -The rats exposed to cigarette smoke had a reduction in left ventricular systolic function, although their myocardial function was preserved.

Padrão de remodelação e função ventricular em ratos expostos à fumaça do cigarro

“…To expose the animals to cigarette smoke, we used a method standardized in our laboratory [8][9][10][11][12][13] . During the first week, the smoke was released at a rate of 5 cigarettes, twice a day in the afternoon with resting intervals of 10 minutes.…”

“…Recently, various studies reported that the exposure to cigarette smoke causes cardiac remodeling in rats, damaging their ventricular function [8][9][10][11][12][13][14][15] . Nevertheless, the importance of the cardiac remodeling pattern, in this model, is not known.…”

Tobacco smoke‐induced left ventricular remodelling is not associated with metalloproteinase‐2 or ‐9 activation

“…The ETS rats were exposed to cigarette smoke in a chamber (dimensions 95×80×65cm) connected to a smoking device based on a model published by Wang et al [12] and adapted by Paiva et al [8]. The smoke was drawn out of filtered commercial cigarettes (composition per unit: 1.1mg of nicotine; 14mg of tar; and 15mg of carbon monoxide) with a vacuum pump and was exhausted into the smoking chamber.…”

Influência da taurina na remodelação cardíaca induzida pela exposição à fumaça do cigarro

“…Simani et al (32) , adaptado por Wang et al (33) e padronizado em nosso laboratório por Paiva et al (34) . Os 18 ratos, em caixas individuais, foram colocados na câmara transparente, com Sony Co e as medidas das estruturas cardíacas foram medidas de acordo com as recomendações da American Society of Echocardiography (35) .…”

“…Diversos estudos experimentais mostraram que a exposição ao fumo levou à alteração de variáveis morfológicas e funcionais cardíacas, representadas por aumento do átrio esquerdo e da cavidade ventricular, hipertrofia miocárdica, bem como redução nos índices de ejeção do ventrículo esquerdo, como porcentagem de encurtamento, fração de variação da área e fração de ejeção (34,61) .…”