***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background — Few prospect i ve studies have examined quantitative cigarette consumption and smoking cessation on sudden cardiac death ( SCD ) risk with long-term follow-up . Methods and Results — We prospect ively examined the association between cigarette smoking and smoking cessation on the risk of SCD among 101 018 women participating in the Nurses ’ Health Study without known coronary heart disease , stroke , and cancer at baseline 1980 . During 30 years of follow-up , we identified 351 SCD events . Compared with never smokers , current smokers had a 2.44-fold ( 95 % CI , 1.80–3.31 ) increased risk of SCD after controlling for coronary risk factors . In multivariable analyses , quantity of cigarettes smoked daily ( P value for trend , < 0.0001 ) and smoking duration ( P value for trend , < 0.0001 ) were linearly associated with SCD risk among current smokers . Small-to-moderate amounts of cigarette consumption ( 1–14 per day ) were associated with a significant 1.84-fold ( 95 % CI , 1.16–2.92 ) increase in SCD risk and every 5 years of continued smoking was associated with an 8 % increase in SCD risk ( hazard ratio , 1.08 ; 95 % CI , 1.05–1.12 ; P<0.0001 ) . The SCD risk linearly decreased over time after quitting and was equivalent to that of a never smoker after 20 years of cessation ( P value for trend , < 0.0001 ) . Conclusions — In this large prospect i ve cohort of women without coronary heart disease at baseline , a strong dose – response relationship between cigarette smoking and SCD risk was observed , and smoking cessation significantly reduced and eventually eliminated excess SCD risk . This suggests efforts to prevent SCD among women should include aggressive strategies for smoking cessation BACKGROUND It is generally accepted that smoking increases blood pressure and inhibits muscle sympathetic nerve activity ( SNA ) . The decrease in muscle SNA with cigarette smoking might be secondary to baroreflex responses to the pressor effect of smoking , thus obscuring a sympathetic excitatory effect of smoking . We tested the hypothesis that smoking increases sympathetic outflow . METHODS AND RESULTS We examined the effects of sham smoking , cigarette smoking , and cigarette smoking in combination with nitroprusside on muscle ( baroreflex-dependent ) SNA in 10 healthy habitual smokers . The 3 sessions were performed in r and om order , each study on a separate day . In an additional study , we also investigated the effects of sham smoking and cigarette smoking on skin ( baroreflex-independent ) SNA in 9 subjects . Compared with sham smoking , cigarette smoking alone increased blood pressure and decreased muscle SNA . When the blood pressure increase in response to smoking was blunted by nitroprusside infusion , there was a striking increase in muscle SNA . Muscle SNA increased up to 3-fold the levels seen before smoking ( P<0.001 ) , accompanied by an increase in heart rate of up to 37+/-4 bpm . Cigarette smoking also induced a 102+/-22 % increase in skin SNA ( P=0.03 ) . CONCLUSIONS These data provide the first direct evidence that cigarette smoking increases sympathetic outflow ABSTRACT Acute changes in select physiological parameters associated with cardiovascular physiology ( systolic and diastolic blood pressure ( BP ) and heart rate ( HR ) ) , pulmonary function ( FVC , FEV1 , and exhaled CO and NO ) and adverse events were measured in 105 clinical ly confined subjects who were r and omized into groups that either completely or partially switched from  conventional cigarettes to e‐cigarettes  or completely discontinued using tobacco and nicotine products altogether . Use of the e‐cigarettes for five days under the various study conditions did not lead to higher BP or HR values , negative respiratory health outcomes or serious adverse health events . Reductions in BP and HR vital signs were observed in most of the participants that either ceased tobacco and nicotine products use altogether or switched completely to using e‐cigarettes . Pulmonary function tests showed small but non‐statistically significant improvements in FVC and FEV1 measurements in most use groups . Statistically significant ( p < 0.05 ) benefits associated with smoking reduction were also noted in exhaled CO and NO levels . All study products were well tolerated . The study findings suggest that there are potential cardiovascular and pulmonary function benefits when smokers switch to using e‐cigarette products . This further reinforces the potential that e‐cigarettes offer smokers seeking an alternative to conventional tobacco products . HIGHLIGHTSSwitching to e‐cigarettes led to small improvements in cardiovascular and pulmonary function . Reductions in vital signs were observed in most subjects that switched to using e‐cigarettes . Use of e‐cigarettes for 5 days did not lead to negative respiratory health outcomes .Physiological changes associated with smoking reduction were noted in exhaled breath . Short‐term use of e‐cigarettes did not result in any serious adverse effects OBJECTIVES We investigated the acute and chronic combined effect of cigarette smoking and caffeine intake on aortic stiffness and wave reflections . BACKGROUND We have shown that smoking and caffeine separately increase arterial stiffness . Aortic stiffness and wave reflections are important determinants of the efficient performance of the cardiovascular system and prognosticators of cardiovascular risk . METHODS The acute effects of smoking ( one cigarette ) , caffeine ( 200 mg , equivalent to 2 cups of coffee ) , and smoking plus caffeine were studied in 24 healthy subjects according to a r and omized , placebo- and sham procedure-controlled crossover design . The chronic effect of smoking and caffeine was studied in a population study that enrolled 160 healthy subjects . RESULTS Acute study : there was a significant interaction between caffeine and smoking with regard to pulse-wave velocity ( p < 0.01 ) and augmentation index ( p < 0.05 ) . When smoking followed caffeine intake , pulse-wave velocity and augmentation index increased further by 0.52 m/s and 13.4 % , respectively , reaching a total of 0.85 m/s and 17.4 % , 0.17 m/s and 9.2 % in excess of the mere sum of caffeine effect ( 0.33 m/s and 4 % ) alone and smoking effect alone ( 0.35 m/s and 4.2 % ) . Population study : there was a significant interaction of chronic coffee consumption and smoking regarding pulse-wave velocity ( p < 0.05 ) and augmentation index ( p = 0.001 ) . CONCLUSIONS The present study shows , for the first time , that when smoking and caffeine intake are combined , they interact and exert a synergistic , unfavorable effect on aortic stiffness and wave reflections on both an acute and chronic basis Abstract We present prospect i ve blood pressure ( BP ) and hear rate ( HR ) changes in smokers invited to switch to e-cigarettes in the ECLAT study . BP and HR changes were compared among ( 1 ) different study groups ( users of high , low , and zero nicotine products ) and ( 2 ) pooled continuous smoking phenotype classification ( same phenotype from week 12 to -52 ) , with participants classified as quitters ( completely quit smoking ) , reducers ( ≥50 % reduction in smoking consumption ) and failures ( < 50 % or no reduction in smoking consumption ) . Additionally , the latter comparison was repeated in a subgroup of participants with elevated BP at baseline . No significant changes were observed among study groups for systolic BP , diastolic BP , and HR . In 145 subjects with a continuous smoking phenotype , we observed lower systolic BP at week 52 compared to baseline but no effect of smoking phenotype classification . When the same analysis was repeated in 66 subjects with elevated BP at baseline , a substantial reduction in systolic BP was observed at week 52 compared to baseline ( 132.4 ± 12.0 vs. 141.2 ± 10.5 mmHg , p < 0.001 ) , with a significant effect found for smoking phenotype classification . After adjusting for weight change , gender and age , reduction in systolic BP from baseline at week 52 remains associated significantly with both smoking reduction and smoking abstinence . In conclusion , smokers who reduce or quit smoking by switching to e-cigarettes  may lower their systolic BP in the long term , and this reduction is apparent in smokers with elevated BP . The current study adds to the evidence that quitting smoking with the use of e-cigarettes does not lead to higher BP values , and this is independently observed whether e-cigarettes are regularly used or not Background Electronic cigarettes have been developed and marketed in recent years as smoking substitutes . However , no studies have evaluated their effects on the cardiovascular system . The purpose of this study was to examine the immediate effects of electronic cigarette use on left ventricular ( LV ) function , compared to the well-documented acute adverse effects of smoking . Methods Echocardiographic examinations were performed in 36 healthy heavy smokers ( SM , age 36 ± 5 years ) before and after smoking 1 cigarette and in 40 electronic cigarette users ( ECIG , age 35 ± 5 years ) before and after using the device with “ medium-strength ” nicotine concentration ( 11 mg/ml ) for 7 minutes . Mitral flow diastolic velocities ( E , A ) , their ratio ( E/A ) , deceleration time ( DT ) , isovolumetric relaxation time ( IVRT ) and corrected-to-heart rate IVRT ( IVRTc ) were measured . Mitral annulus systolic ( Sm ) , and diastolic ( Em , Am ) velocities were estimated . Myocardial performance index was calculated from Doppler flow ( MPI ) and tissue Doppler ( MPIt ) . Longitudinal deformation measurements of global strain ( GS ) , systolic ( SRs ) and diastolic ( SRe , SRa ) strain rate were also performed . Results Baseline measurements were similar in both groups . In SM , IVRT and IVRTc were prolonged , Em and SRe were decreased , and both MPI and MPIt were elevated after smoking . In ECIG , no differences were observed after device use . Comparing after-use measurements , ECIG had higher Em ( P = 0.032 ) and SRe ( P = 0.022 ) , and lower IVRTc ( P = 0.011 ) , MPI ( P = 0.001 ) and MPIt ( P = 0.019 ) . The observed differences were significant even after adjusting for changes in heart rate and blood pressure . Conclusions Although acute smoking causes a delay in myocardial relaxation , electronic cigarette use has no immediate effects . Electronic cigarettes ’ role in tobacco harm reduction should be studied intensively in order to determine whether switching to electronic cigarette use may have long-term beneficial effects on smokers ’ health . Trial registration Current Controlled Trials IS RCT We aim ed to determine whether smoking status affects the recurrence of atrial fibrillation or atrial flutter in patients after cardioversion .  The clinical data of patients undergoing cardioversion for atrial flutter from January 1 , 2000 to December 31 , 2005 were prospect ively collected . Arrhythmia recurrences were detected by retrospective review of comprehensive medical records and were determined using electrocardiography . The smoking history was prospect ively collected through a st and ardized clinical form and subsequently categorized as lifetime nonsmoker , exsmoker , or current smoker . Univariate and multivariate associations with end points for clinical and lifestyle variables were assessed with Cox proportional hazards models . Women who were current smokers at cardioversion had a greater risk of atrial arrhythmia recurrence than did nonsmokers ( hazard ratio 1.71 , 95 % confidence interval 1.10 to 2.67 , p = 0.02 ) . The increased risk of arrhythmia recurrence in female smokers was not seen in male smokers . Compared to lifetime nonsmokers , the mortality hazard ratio among men was 1.18 ( 95 % confidence interval 0.88 to 1.58 ; p = 0.28 ) in exsmokers and 1.93 ( 95 % confidence interval 1.20 to 3.11 ; p = 0.007 ) in current smokers . The risk of death after cardioversion was not increased in women . In conclusion , smoking is an independent predictor of atrial arrhythmia recurrence after cardioversion in women ; however , an increased mortality risk , but not arrhythmia recurrence risk , was seen in men Objectives To measure the short-term effects of an electronic nicotine delivery device ( “ e cigarette ” , ENDD ) on desire to smoke , withdrawal symptoms , acceptability , pharmacokinetic properties and adverse effects . Design Single blind r and omised repeated measures cross-over trial of the Ruyan V8 ENDD . Setting University research centre in Auckl and , New Zeal and . Participants 40 adult dependent smokers of 10 or more cigarettes per day . Interventions Participants were r and omised to use ENDDs containing 16 mg nicotine or 0 mg capsules , Nicorette nicotine inhalator or their usual cigarette on each of four study days 3 days apart , with overnight smoking abstinence before use of each product 
    Output:
    
Acute EC vaping increased HR and BP less than acute TC smoking .
Nicotine but not non-nicotine constituents in EC aerosol were responsible for the sympathoexcitatory effects .
The results of chronic EC vaping studies were consistent with a chronic sympathoexcitatory effect as estimated by HRV , but this did not translate into chronic increases in HR or BP .
Electronic cigarettes are sympathoexcitatory .
Cardiac sympathoexcitatory effects are less when vaping using the earlier generation ECs than when smoking TCs .