Long-term cigarette smoking is associated with increased myocardial perfusion heterogeneity assessed by positron emission tomography

Effects of smoking on coronary microcirculatory function: a twin study

BACKGROUND

In asymptomatic smokers, coronary microcirculatory dysfunction, assessed by coronary flow reserve (CFR), is an early indicator of cardiovascular risk. Inflammation and oxidative stress may be the mechanisms through which smoking affects the microvasculature.

OBJECTIVES

The purpose of this study was to determine the relationship between smoking and CFR, taking into account potential shared genetic effects.

METHODS

We examined 360 male middle aged twins (288 non-smokers and 72 smokers), including 46 twin pairs discordant for current smoking. Coronary flow reserve (CFR) in response to adenosine was measured with positron emission tomography [N(13)] ammonia and quantitation of coronary blood flow at rest and after adenosine stress. Inflammation was assessed by measuring interleukin-6 and C-reactive protein, and oxidative stress was determined by measuring plasma hydroperoxides, glutathione (GSH), the oxidized form of GSH, GSSG, and the ratio of GSH to GSSG.

RESULTS

CFR was significantly lower in smokers compared to nonsmokers (2.25 vs. 2.75, p<0.01). This relationship persisted after accounting for known cardiovascular disease risk factors, and was marginally affected by adjusting for inflammatory and oxidative stress biomarkers. In addition, in smoking-discordant twin pairs, CFR in the smoking twin was significantly lower than in the non-smoking co-twin (2.25 vs. 2.67, p=0.03) even after adjustment for cardiovascular risk factors.

CONCLUSIONS

Our results demonstrate the adverse effects of smoking in the early phases of cardiovascular disease. Mechanisms other than peripherally measured inflammation and oxidative stress are involved.

Haemodynamic reactions to acute psychological stress and smoking status in a large community sample

Exaggerated haemodynamic reactions to acute psychological stress have been implicated in a number of adverse health outcomes. This study examined, in a large community sample, the cross-sectional associations between haemodynamic reactivity and self-reported smoking status. Blood pressure and heart rate were measured at rest and in response to a 3-minute arithmetic stress task. Participants were classified as current, ex-, or non-smokers by their response to a simple prompt. Smokers had significantly smaller SBP and DBP reactions to acute stress than ex- and non-smokers; current and ex-smokers had lower HR reactivity. These effects remained significant following adjustment for a host of variables likely to be associated with reactivity and/or smoking. Although the act of smoking acutely increases haemodynamic activity, the present findings contribute to a growing body of literature showing that smokers have blunted reactivity to mental stress. They also support the hypothesis that blunted reactivity may be characteristic of a range of dependencies. The present results also suggest that smoking status needs to be considered in the design and analysis of stress reactivity studies.

Oxidative stress and accelerated vascular aging: implications for cigarette smoking

Cigarette smoking is the major cause of preventable morbidity and mortality in the United States and constitutes a major risk factor for atherosclerotic vascular disease, including coronary artery disease and stroke. Increasing evidence supports the hypothesis that oxidative stress and inflammation provide the pathophysiological link between cigarette smoking and CAD. Previous studies have shown that cigarette smoke activates leukocytes to release reactive oxygen and nitrogen species (ROS/RNS) and secrete pro-inflammatory cytokines, increases the adherence of monocytes to the endothelium and elicits airway inflammation. Here we present an overview of the direct effects of water-soluble cigarette smoke constituents on endothelial function, vascular ROS production and inflammatory gene expression. The potential pathogenetic role of peroxynitrite formation, and downstream mechanisms including poly(ADP-ribose) polymerase (PARP) activation in cardiovascular complications in smokers are also discussed.

Coronary risk factors and myocardial perfusion in asymptomatic adults: the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVES

The purpose of this study was to determine the cross-sectional relation between myocardial perfusion and coronary heart disease (CHD) risk factors among adults with no clinical CHD.

BACKGROUND

Clinical studies suggest that myocardial perfusion is often abnormal in individuals without CHD but with risk factors. Epidemiologic study in asymptomatic populations is lacking.

METHODS

Two hundred twenty-two men and women, ages 45 to 84 years and free of a CHD diagnosis, in the University of Minnesota field center of the Multi-Ethnic Study of Atherosclerosis (MESA) had myocardial blood flow (MBF) determined using cardiac magnetic resonance imaging at rest and during adenosine-induced hyperemia. Perfusion reserve (PR) was calculated as the ratio of hyperemic to rest MBF.

RESULTS

Both resting and hyperemic MBF were lower in men than in women, even after considering age and menopause. Hyperemic MBF was also significantly lower in subjects who were older, and in those with higher blood pressure, higher fasting glucose, and lower low-density lipoprotein cholesterol. After adjusting for age, gender, and race, reduced PR was independently associated with hypertension, higher diastolic blood pressure, and higher total and low-density lipoprotein cholesterol, but was not associated with cigarette smoking, obesity, physical activity, or diabetes. Moreover, hyperemic MBF and PR were correlated strongly and inversely with estimated 10-year CHD risk based on Framingham equations (p for trends: <0.0001).

CONCLUSIONS

Coronary vasoreactivity is reduced in asymptomatic individuals with a greater coronary risk factor burden. Our study results imply that changes in coronary vascular reactivity, in response to risk factors, may be detected in adults without symptomatic CHD.

Sodium pertechnetate (Na99mTcO4) biodistribution in mice exposed to cigarette smoke

BACKGROUND: The biological effects of cigarette smoke are not fully known. To improve our understanding of the action of various chemical agents, we investigated the biodistribution of sodium pertechnetate (Na99mTcO4) in mice exposed to cigarette smoke. METHODS: Fifteen BALB/c male mice were exposed to the smoke of nine whole commercial cigarettes per day, 3 times/day, for up to 10 days to whole body exposure in a chamber. A control group of 5 BALB/c male mice was sham-smoked. One day later, the exposed and control groups of mice received (7.4 MBq/0.3 ml) of Na99mTcO4 before being killed at 30 min. Bones, brain, heart, intestine, kidney, liver, lungs, muscle, pancreas, spleen, stomach, testis and thyroid were weighed and these organs and blood radioactivity recorded with a gamma counter. The percentage per gram of tissue of injected dose (%ID/g) was determined for each organ. RESULTS: Cigarette smoke significantly decreased (p < 0.05) the %ID/g in red blood cells, bone, kidney, lung, spleen, stomach, testis and thyroid of the exposed mice. CONCLUSION: The toxic effects of cigarette smoke reduced the Na99mTcO4 biodistribution.

Increased thrombolysis in myocardial infarction frame count in patients with myocardial infarction and normal coronary arteriogram: a possible link between slow coronary flow and myocardial infarction

BACKGROUND

Thrombolysis in myocardial infarction (TIMI) frame count is a simple clinical tool for assessing quantitative indexes of coronary blood flow. This technique counts the number of cineangiographic frames from initial contrast opacification of the proximal coronary artery to opacification of distal arterial landmarks. We hypothesized that patients with normal coronary artery (NCA) and myocardial infarction (MI) might have impaired coronary flow. Accordingly, we assessed the TIMI frame counts of patients with NCA and MI and compared to patients with NCA and without MI.

MATERIALS AND METHOD

This retrospective study included consecutive patients with MI and who were found to have normal coronary angiograms performed between 1999 and 2003. Fifty patients (group I) with NCA and MI were enrolled in the study. Fifty consecutive patients with NCA and without MI were also enrolled in the study as control group (group II). Mean time interval between MI and coronary angiography was 6 +/- 2 days.

RESULTS

There were statistically significant differences between groups I and II in respect to gender (11 females (22%) versus 22 females (44%), p = 0.003, respectively) and smoking status (62% (31/50) versus 38% (19/50), p = 0.02). Comparison of TIMI frame counts between two groups revealed that group I patients had significantly higher TIMI frame counts than group two patients for all three coronary arteries (LAD: 40 +/- 12 versus 23 +/- 7, Cx: 47 +/- 14 versus 27 +/- 7, RCA: 36 +/- 10 versus 26 +/- 10, respectively, p < 0.001 for all). Smokers were significantly younger when compared to non-smokers (44 +/- 5 years versus 51 +/- 9 years, p = 0.008, respectively). TIMI frame counts of smokers did not significantly differ from those of non-smokers in group I patients. There were statistically significant differences between smokers and non-smokers in group II patients regarding TIMI frame counts for all three coronary arteries (LAD: 29 +/- 7 versus 18 +/- 3, LCX: 34 +/- 10 versus 22 +/- 4, RCA: 34+ /- 13 versus 20 +/- 4, respectively, p < 0.001 for all).

CONCLUSION

We have shown that patients with MI and NCA have higher TIMI frame counts for all coronary arteries when compared to patients without MI and NCA. Absence of difference between smokers and non-smoker in the myocardial infarction group in respect to TIMI frame count, has suggested that smoking does not lead to further increase of TIMI frame counts. On the other hand, in patients without MI and with NCA, smokers have higher TIMI frame counts than non-smokers have.

The endothelium: dysfunction and beyond

Since its anatomic discovery in the 19th century, the endothelium was considered to fulfill no other purpose than that of a physical barrier between blood and tissue, until Furchgott and colleagues defined endothelium-dependent vasoreactivity in the late 1970s. Henceforth, a functional paradigm defined the balance between endothelium-derived relaxing factors and endothelium-derived contracting factors as the hallmark of endothelial cell integrity. As a consequence, any reflection of a deviation from this state was defined as endothelial dysfunction, most notably the impairment of vasorelaxation in response to pharmacologic stimuli such as acetylcholine or nonpharmacologic stimuli such as shear stress and cold pressor. Within the coronary artery tree these alterations have been recognized before the development of obstructive coronary artery disease, affecting the microcirculation before the epicardial conduit vessel. Furthermore, recent clinical trials outlined the prognostic significance of these changes, whereby impairment of increase in coronary blood flow in response to endothelium-dependent stimuli seemed to be of utmost importance. Thus it is intriguing to speculate on the evolving role of myocardial perfusion imaging in combination with pharmacologic and nonpharmacologic stimuli for the noninvasive assessment of coronary endothelial dysfunction in patients at risk for future adverse events. At a minimum, this review aims to put endothelial dysfunction into an imaging perspective beyond the scope of the conventional approach.

Vibration exposure, smoking, and vascular dysfunction

OBJECTIVES

Vibration white finger (VWF), also known as "occupational Raynaud's phenomenon", is marked by arterial hyperresponsiveness and vasoconstriction during cold stimulation. The impact of tobacco use, and by extension stopping smoking, on the long term course of the disease has been inconclusively characterised. The objectives of this study included assessment of the impact of tobacco use on symptoms and on objective tests in shipyard workers exposed to vibration, and in gauging the natural history of the disorder after stopping exposure and changing smoking patterns.

METHODS

In a cross sectional investigation, 601 current and former users of pneumatic tools were evaluated subjectively for cold related vascular symptoms, and tested by cold challenge plethysmography. There was follow up and subsequent testing of 199 members of the severely effected subgroup of smokers and non-smokers, many of whom had stopped smoking in the interval between tests. Effects of smoking and stopping smoking on symptoms and plethsymographic results were assessed.

RESULTS

Symptoms and measured abnormal vascular responses related to cold were more severe in smokers than in non-smokers. Follow up of 199 severely effected members of the cohort, all removed from exposure for 2 years, indicated that smokers were almost twice as likely to have more severe vasospasm (test finger/control finger systolic blood pressure% (FSBP%) <30) than were non-smokers (-32.2% v 17.4%). 53 Subjects who stopped smoking during the interval between tests improved, and were indistinguishable from non-smokers similarly exposed to vibration. Additional physiological benefits of stopping smoking were still apparent at further follow up examination, 1 year later. Improvements evident on plethysmography were not accompanied by improvements in symptoms, which were unaffected by smoking.

CONCLUSIONS

Smoking seems to delay physiological improvement in response to cold challenge in workers with VWF, after the end of exposure to vibration. Symptoms were less likely to improve over time than digital blood pressure, and were less affected by smoking.

Generalized linear least squares method for fast generation of myocardial blood flow parametric images with N-13 ammonia PET

In this paper, we developed and tested strategies for estimating myocardial blood flow (MBF) and generating MBF parametric images using positron emission tomography (PET), N-13 ammonia, and the generalized linear least square (GLLS) method. GLLS was generalized to the general linear compartment model, modified for the correction of spillover, validated using simulated N-13 ammonia data, and examined using PET data from several patient studies. In comparison to the standard model-fitting procedure, the GLLS method provided similar accuracy and superior computational speed.

Coronary vasomotion in patients with syndrome X: evaluation with positron emission tomography and parametric myocardial perfusion imaging

The aim of this study was to elucidate further the causative mechanism of abnormal coronary vasomotion in patients with syndrome X. In patients with syndrome X, defined as angina pectoris and documented myocardial ischaemia during stress testing with normal findings at coronary angiography, abnormal coronary vasomotion of either the micro- or the macrocirculation has been suggested as the causative mechanism. Accordingly, we evaluated endothelial function, vasodilator reserve, and perfusion heterogeneity in these patients. Twenty-five patients with syndrome X (definitely normal coronary arteriogram, group A), 15 patients with minimal coronary artery disease (group B) and 21 healthy volunteers underwent [13N]ammonia positron emission tomography at rest, during cold pressor stimulation (endothelial function) and during dipyridamole stress testing (vasodilator reserve). Heterogeneity of myocardial perfusion was analysed by parametric polar mapping using a 480-segment model. In both patient groups, resting perfusion was increased compared to the normal subjects: group A, 127+/-31 ml.min-1.100 g-1; group B, 124+/-30 ml.min-1.100 g-1 normal subjects, 105+/-21 ml.min-1.100 g-1 (groups A and B vs normals, P<0.05). These differences were abolished after correction for rate-pressure product. During cold pressor stimulation, the perfusion responses (ratio of cold pressor perfusion to resting perfusion) were similar among the patients and the control subjects (group A, 1.20+/-0.23; group B, 1.24+/-0.22; normal subjects, 1.23+/-0.14). Likewise, during dipyridamole stress testing, perfusion responses were similar among the three groups (group A, 2.71+/-0.67; group B, 2.77+/-1.29; normal subjects, 2. 91+/-1.04). In group A the heterogeneity of resting perfusion, expressed as coefficient of variation, was significantly different from the volunteers (20.1+/-4.5 vs 17.0+/-3.0, P<0.05). In group B (coefficient of variation 19.4+/-3.9) the difference from normal volunteers was not significant. In this study, patients with syndrome X and patients with minimal coronary artery disease showed normal perfusion responses during cold pressor stimulation and dipyridamole stress testing. Our findings therefore suggest that endothelial dysfunction and impaired vasodilator reserve are of no major pathophysiological relevance in patients with syndrome X. Rather, other mechanisms such as increased sympathetic tone and focal release of vasoactive substances may play a role in the pathogenesis of syndrome X.