We compared the effects of Heat-not-Burn cigarette (HNBC) to those of tobacco cigarette (Tcig), on myocardial, coronary and arterial function as well as on oxidative stress and platelet activation in 75 smokers. In the acute study, 50 smokers were randomised into smoking a single Tcig or a HNBC and after 60 min were crossed-over to the alternate smoking. For chronic phase, 50 smokers were switched to HNBC and were compared with an external group of 25 Tcig smokers before and after 1 month. Exhaled carbon monoxide (CO), pulse wave velocity (PWV), malondialdehyde (MDA) and thromboxane B2 (TxB2) were assessed in the acute and chronic study. Global longitudinal strain (GLS), myocardial work index (GWI), wasted myocardial work (GWW), coronary flow reserve (CFR), total arterial compliance (TAC) and flow-mediated dilation (FMD) were assessed in the chronic study. Acute HNBC smoking caused a smaller increase of PWV than Tcig (change 1.1 vs 0.54 m/s, p < 0.05) without change in CO and biomarkers in contrast to Tcig. Compared to Tcig, switching to HNBC for 1-month improved CO, FMD, CFR, TAC, GLS, GWW, MDA, TxB2 (differences 10.42 ppm, 4.3%, 0.98, 1.8 mL/mmHg, 2.35%, 19.72 mmHg%, 0.38 nmol/L and 45 pg/mL respectively, p < 0.05). HNBCs exert a less detrimental effect on vascular and cardiac function than tobacco cigarettes. Trial registration Registered on https://clinicaltrials.gov/ (NCT03452124, 02/03/2018).
Smoking constitutes a major modifiable risk factor for cardiovascular disease [
More than 5600 chemical components have been identified in traditional tobacco cigarettes, many of which harmfully affect the cardiovascular system [
The aim of this study was to investigate the effects of HNBC on endothelial function, arterial stiffness, myocardial deformation, oxidative stress, and platelet activation both in an acute context and after 1 month of switching to HNBC smoking, in comparison with traditional tobacco cigarette.
The mean age of the 50 participants was 48 ± 5 years, 53% were female, and reported smoking 27 ± 9 cigarettes per day per individual with a smoking history of 38 ± 18 pack-years. Tobacco smokers, used as controls, had a mean age of 46 ± 14 years, 53% were female and reported smoking 26 ± 8 cigarettes per day per individual with a smoking history of 37 ± 19 pack-years. All subjects had similar baseline characteristics in terms of arterial stiffness, myocardial deformation, oxidative stress, and platelet activation status (Table 1).
Table 1 Characteristics of the study cohort.
Intervention N = 50 Control N = 25 p-value Age (years) 48 ± 9 46 ± 11 0.7 Sex (female) 27 (53%) 14 (53%) 0.6 SBP (mmHg) 125 ± 15 121 ± 13 0.7 DBP (mmHg) 79 ± 10 76 ± 10 0.6 Heart rate (bpm) 66 ± 9 67 ± 8 0.8 BMI (kg/m2) 27.2 ± 5.1 27.3 ± 5.2 0.9 CO (ppm) 14.9 ± 7.4 15.8 ± 4.9 0.7 Pack-years 38 ± 18 37 ± 19 0.3 LDL-cholesterol (mg/dl) 114 ± 22 118 ± 19 0.5 CRP-hs (mg/dl) 1.8 ± 0.4 1.9 ± 0.5 0.4
SBP systolic blood pressure, DBP diastolic blood pressure, BMI body mass index, BP blood pressure, CO exhaled carbon monoxide, CRP-hs C-reactive protein highly sensitive, values are mean ± SD.
During the chronic study, only 3 of the 50 (6%) participants reported simultaneous use of IQOS with traditional cigarettes (< 5 per day). The remaining 47 participants successfully refrained from traditional cigarette smoking and used HNBC exclusively during the 1-month follow-up period (17 ± 6 heets per day per individual). No side-effects were reported. In the control group, smokers used 28 ± 8 Tcig per day per individual during one month.
During the acute study, PWV was increased after HBNC and Tcig smoking compared to baseline (Table 2, p = 0.04 and p = 0.005 respectively). However, Tcig smoking resulted in a greater increase of PWV than HNBC puffing (mean change 1.11 m/s; 95% CI 0.35–1.18, p = 0.005 vs 0.54 m/s; 95% CI 0.05–1.04, p = 0.03 respectively, difference = 0.57 m/s; 95% CI 0.005–1.131, p = 0.04) (Table 2, Fig. 1A, Supplementary Fig. 1). Furthermore, compared to baseline, Tcig smoking caused an increase in brachial systolic blood pressure and heart rate (p = 0.03 and p = 0.02, respectively) while HNBC puffing showed no significant changes on the above indices (p = 0.14 and p = 0.77) (Supplementary Fig. 2).
Table 2 Comparative acute effects of heat-not-burn cigarettes versus tobacco cigarette on arterial stiffness, oxidative stress, platelet activation, and exposure to CO in the acute study (n = 50).
Baseline Sham HNBC TCig PWV (m/s) 9.7 ± 1.3 9.9 ± 1.7 10.2 ± 1.7† 10.8 ± 2.4*† cSBP (mmHg) 121 ± 16 120 ± 15 119 ± 17.6 120 ± 17 Heart rate (bpm) 66 ± 9 66 ± 9 66 ± 8 70 ± 10*† SBP (mmHg) 125 ± 15 125 ± 16 128 ± 19 130 ± 19*† DBP (mmHg) 79 ± 10 78 ± 10 80 ± 11 82 ± 10 MDA (nmol/l) 1.34 ± 0.72 1.35 ± 0.83 1.28 ± 0.95 2.56 ± 0.85*† PC (nmol/mg protein) 15.7 ± 5.8 14.5 ± 4.9 12.8 ± 5.2 13.9 ± 5.6 TxB2 (ng/ml) 378 ± 103 375 ± 105 362 ± 113 398 ± 105*† CO (ppm) 14.9 ± 7.4 14.4 ± 3.8 14.1 ± 7.3 17.5 ± 7.8*†
*p < 0.05 of the overall model by ANOVA for the within subject effects of the tobacco products.
Graph: Figure 1 Acute effects of heat-not-burn puffing versus tobacco cigarette smoking. Comparison between the acute effects of heat-not-burn versus tobacco cigarette smoking on (A) arterial stiffness, (B) oxidative stress burden, and (C) platelet activation status. HBNC showed a smaller increase of PWV than tobacco cigarette. All biomarkers are impaired following Tcig smoking, in contrast with HNBC puffing. PWV carotid-femoral pulse wave velocity, HNBC heat-not-burn cigarette, MDA malondialdehyde, Tcig tobacco cigarette, TxB2 thromboxane B2, SE Standard Error.
In the acute setting, Tcig caused a significant MDA increase, in contrast with the lack of increase of MDA levels after HNBC puffing (baseline: 1.34 ± 0.72 vs Tcig: 2.56 ± 0.85, p = 0.03, vs HNBC: 1.28 ± 0.95 nmol/L, p = 0.55) (Table 2, Fig. 1B, Supplementary Fig. 3). Thus, MDA levels were found lower after HBNC than after Tcig (p = 0.02). Additionally, the MDA increase caused by Tcig was significantly correlated with the respective increase in PWV (r = 0.825, p < 0.001).
PC levels were unchanged during the acute phase of the study (p for the overall model, p = 0.54, Table 2).
Compared to baseline, acute Tcig smoking significantly increased TxB2 concentration; TxB2 levels did not change significantly following HNBC puffing (baseline: 378 ± 103 vs Tcig: 398 ± 105, p = 0.02, vs HNBC: 362 ± 113 pg/ml, p = 0.16). Thus, TXB2 levels were found lower after HBNC than after Tcig (p = 0.005) (Table 2, Fig. 1C, Supplementary Fig. 4).
In the acute phase, compared to baseline, exhaled CO levels were significantly elevated after Tcig smoking but were not affected by HNBC puffing (CO base: 14.9 ± 7.4 vs CO Tcig: 17.5 ± 7.8, p < 0.001, vs CO HNBC: 14.2 ± 7.3 ppm, p = 0.1) Thus, CO levels were found lower after HBNC than after Tcig (p < 0.001) (Table 2).
There was a significant interaction between changes of FMD, CFR, TAC, central SBP and smoking status (HNBC or Tcig) at 1 month (F = 5.6, p = 0.01; F = 7.1, p = 0.001; F = 6.8, p = 0.001, and F = 5.4, p = 0.03, respectively).
FMD and CFR were both significantly elevated within 1 month of switching to HNBC compared to tobacco smokers (difference in FMD = 4.3%; 95% CI 1.23–7.51, p = 0.009; difference in CFR = 0.98; 95% CI 0.23–1.80, p = 0.02) (Table 3, Figs. 2A,B and 3, Supplementary Figs. 5, 6).
Table 3 Arterial elasticity, myocardial deformation, endothelial function, and ventricular-arterial coupling progression after 1 month of switching from tobacco cigarette smoking to heat-not-burn product puffing (n = 50) compared to tobacco cigarette smokers (n = 25).
Group Baseline One month p-value Body weight (kg) HNBC 76.9 ± 2.4 77.1 ± 1.9 0.7 Tcig 80.9 ± 3.4 80.5 ± 3.5 0.8 PWV (m/s) HNBC 9.7 ± 1.3 10.1 ± 1.5 0.3 Tcig 9.7 ± 1.6 10.2 ± 2.3 0.4 Central SBP (mmHg) HNBC 121 ± 16 112 ± 17* 0.02 Tcig 121 ± 16 123 ± 15 0.3 TAC (ml/mmHg) HNBC 19.1 ± 4.2 20.9 ± 5.2* 0.03 Tcig 17.6 ± 8.4 17.5 ± 7.6 0.2 Heart rate (bpm) HNBC 66 ± 9 65 ± 8 0.4 Tcig 67 ± 8 68 ± 8 0.8 SBP (mmHg) HNBC 125 ± 15 126 ± 16 0.9 Tcig 121 ± 13 122 ± 13 0.9 DBP (mmHg) HNBC 79 ± 10 78 ± 9 0.7 Tcig 76 ± 10 76 ± 10 0.9 GLS (%) HNBC − 19.9 ± 2.3 − 20.9 ± 2.5* 0.002 Tcig − 19.7 ± 1.3 − 20 ± 0.7 0.3 FMD (%) HNBC 7.8 ± 4.3 12.1 ± 4.2* 0.01 Tcig 7.9 ± 3.9 8.3 ± 3.5 0.6 CFR HNBC 2.4 ± 0.6 3.5 ± 0.8* < 0.001 Tcig 2.5 ± 0.2 2.6 ± 0.2 0.2 PWV/GLS HNBC − 0.5 ± 0.1 − 0.48 ± 0.08* < 0.001 Tcig − 0.49 ± 0.1 − 0.51 ± 0.1 0.4 GWI (mmHg%) HNBC 1949 ± 315 1828 ± 320* 0.01 Tcig 1954 ± 290 1986 ± 290 0.1 GCW (mmHg%) HNBC 2214 ± 339 2156 ± 385 0.1 Tcig 2202 ± 379 2180 ± 356 0.3 GWW (mmHg%) HNBC 80 ± 55 65 ± 37* < 0.001 Tcig 74 ± 33 78 ± 42 0.09 GWE (%) HNBC 95.8 ± 2.3 96.4 ± 1.8 0.1 Tcig 95.5 ± 2 95 ± 2 0.5
*p < 0.05 for interaction with group, derived from post hoc analysis by ANOVA. HNBC heat-not-burn cigarette, TCig tobacco cigarette, CFR coronary flow reserve, PWV carotid-femoral pulse wave velocity, FMD flow-mediated dilation, GCW constructive myocardial work, GLS global longitudinal strain, GWE myocardial work efficiency, GWI global myocardial work index, GWW wasted myocardial work, values are mean±SD.
Graph: Figure 2 Progression of coronary flow reserve, flow mediated dilation, and myocardial work within 1 month of follow-up. Replacement of Tcig smoking with HNBC puffing for 1-month results in coronary and peripheral endothelial function improvement, along with wasted myocardial work reduction. CFR coronary flow reserve, FMD flow-mediated dilation, GWW global wasted work, SE Standard Error.
Graph: Figure 3 Coronary flow of left anterior descending artery at rest (left panel) and after adenosine infusion (right panel) for calculation of coronary flow reserve. Coronary flow of left anterior descending artery at rest (left panel) and after adenosine infusion (right panel) for calculation of coronary flow reserve at baseline (A) and after switching to HNBC for one month (B). The coronary flow reserve increased from 2.5 to 3.1 after 1 month of switching from tobacco cigarette to HNBC.
Central SBP was significantly reduced in the HNBC group than in tobacco smoking group (difference = 10.4 mmHg-1; 95% CI 3.05–17.88, p = 0.02). TAC was significantly increased in the HNBC group than in tobacco smoking group (difference = 1.8 mL/mmHg; 95% CI 0.3–3.5, p = 0.04). Compared to baseline, PWV, HR, brachial SBP and DBP values were not reduced after 1 month of using HNBC (p > 0.05, Table 3, Supplementary Fig. 7). Compared to baseline, no significant changes were observed in all vascular markers within 1 month in the control group of tobacco smokers (p > 0.05, Table 3).
There was a significant interaction between changes of GLS, PWV/GLS, GWI, GWW, GWE, and smoking status at 1 month (HNBC or Tcig) (p < 0.05 for all comparisons).
GLS was improved in the HNBC compared to the control group at follow-up (difference = 2.35%; 95% CI 0.23–4.48, p = 0.03) (Table 3, Supplementary Fig. 8).
PWV/GLS ratio, as a marker of ventricular-arterial interaction, was found to be improved within 1 month of switching to HNBC compared to conventional tobacco smoking (p = 0.03) (Table 3).
Moreover, GWI and GWW were both reduced within one month of HNBC use compared to conventional tobacco use (difference in GWI = 152 mmHg%; 95% CI 81.74–224.05, p = 0.001; difference in GWW = 19.72 mmHg%; 95% CI 4.35–35.08 p = 0.014) (Table 3, Fig. 2C). The increase in TAC was significantly correlated with the decrease in GWI (r = 0.344, p = 0.03). Compared to baseline, all myocardial deformation indices did not change significantly in the control group of tobacco smokers at 1 month (p > 0.05).
There was a significant interaction between changes of MDA, PC, TXB2 and smoking status (HNBC or Tcig) at 1 month (F = 7, p = 0.01; F = 4.8, p = 0.04; and F = 6.8, p = 0.01 respectively).
MDA and PC concentration significantly decreased in subjects switching to HNBC compared to tobacco smokers (difference MDA = 0.38 nmol/l; 95% CI 0.10–0.66, p = 0.009; PC = 7.73 nmol/mg protein; 95% CI 0.19–15.28, p = 0.04) (Table 4, Supplementary Fig. 9). Additionally, replacement of Tcig by HNBC caused a TxB2 reduction than tobacco smoking (difference = 45 pg/ml; 95% CI 5.28–86.31, p = 0.03) (Table 2, Supplementary Fig. 10). None of the aforementioned parameters changed in the control group at 1 month compared to baseline (p > 0.05 Table 4).
Table 4 Progression of exposure to CO, oxidative stress burden, and platelet activation after 1 month of switching from tobacco cigarette smoking to heat-not-burn product puffing.
Group Baseline Follow-up p-value CO (ppm) HNBC 14.9 ± 7.4 6.7 ± 6.4* < 0.001 Tcig 15.8 ± 4.9 17.4 ± 4.8 0.3 MDA (nmol/l) HNBC 1.34 ± 0.72 1.11 ± 0.95* 0.01 Control 1.43 ± 0.9 1.45 ± 0.83 0.3 PC (nmol/mg protein) HNBC 15.7 ± 5.8 9 ± 4.4* 0.04 Control 16.1 ± 8.8 17.2 ± 3.3 0.3 TxB2 (pg/ml) HNBC 378 ± 103 323 ± 137* 0.01 Control 417 ± 24 407 ± 16 0.4
*p < 0.05 for interaction with group, derived from post hoc analysis by ANOVA. CO carbon monoxide, MDA malondialdehyde, PC protein carbonyls, TxB2 thromboxane B2 values are mean ± SD.
At follow-up, the measured decrease in plasma MDA levels was significantly positively correlated with the increase in FMD (r = 0.51, p = 0.03).
There was a significant interaction between changes of CO and smoking status (HNBC or Tcig) at 1 month (F = 8.5, p = 0.001). Compared to baseline, CO measurements were reduced after switching to HNBC (p < 0.001), while remaining unchanged in controls subjects (p = 0.2) (difference in CO between groups: 10.42 ppm; 95% CI 3.07–17.76, p = 0.007) (Table 4).
In the acute crossover phase of this study, it was demonstrated that a single HNBC puffing resulted in a smaller increase of pulse wave velocity compared to tobacco cigarette smoking and was not associated with further impairment of oxidative stress and platelet activation or increased exposure to CO, compared to baseline. Conversely, acute smoking of a tobacco cigarette had detrimental effects on the examined markers of vascular function, oxidative stress, and platelet activation. Furthermore, in the chronic phase of this study, switching from Tcig to HNBC for 1 month was associated with improvement in endothelial function, coronary flow reserve, arterial compliance, and myocardial work, as well as with reduction of oxidative stress burden, platelet activation, and exposure to CO. These changes were not evident in the parallel control group of subjects who continued smoking tobacco cigarettes for a month. Interestingly, the reduction in oxidative stress burden after switching to HNBC was associated with the respective improvement of endothelial function, while the increase in arterial compliance was associated with the concomitant reduction of myocardial work.
Arterial elasticity is impaired in the context of both acute and chronic smoking, as assessed by carotid to femoral PWV [
Augmentation of oxidative stress is a key pathophysiological mediator of cardiovascular harm caused by acute and chronic smoking [
Increased platelet activation plays a significant role in promoting atherosclerosis and thrombotic complications, and is enhanced by Tcig smoking [
Exhaled CO levels constitute a widely used marker of acute smoking status [
Endothelial dysfunction is a prominent end-point of the pathophysiological cascades activated by Tcig smoking [
Novel markers of ventricular arterial-interaction incorporate measurements of afterload in the investigation of myocardial function using speckle tracking echocardiography; the shortcomings of ejection fraction assessment and the diagnostic pitfalls arising from the load-dependent nature of global longitudinal strain estimation are overcome. Thus, a non-invasive and more clinically feasible method of myocardial work estimation is provided by constructing longitudinal myocardial strain-pressure curves using speckle tracking imaging [
In an elegant study by Frati et al. [
Our study was an acute independent, randomised, cross-over trial followed by a chronic case control follow-up study.
According to our initial Study design, (ClinicalTrials.gov, NCT03452124) the primary outcome for the acute study was the effect of HNBC in comparison to Tcig on PWV, while primary outcome for the chronic study was the effect of use of HNBC for one month in comparison to Tcig smoking for the same period on LV deformation. The study was approved by the Attikon University Hospital scientific ethics committee (Approval number: 2874/06-12-17), funded by the Hellenic Society of Lipidology of Atherosclerosis and Vascular Disease. The study was conducted according to the Declaration of Helsinki and written informed consent was provided by the participants. Our study was registered on https://clinicaltrials.gov/, NCT03452124, 02/03/2018.
Out of 95 screened smokers attending the Attikon University Hospital smoking cessation unit, 50 current smokers (age: 48 ± 5 years, 53% female, 27 ± 9 cigarettes/day, 29 ± 9 pack-years) and 25 controls smokers (age: 46 ± 14 years, 53% female, 26 ± 8 cigarettes/day, 30 ± 8 pack-years) with no intention to quit smoking were included in our study (Fig. 4). Smoking status was verified by way of self-reported smoking burden per day and exhaled carbon monoxide (eCO) concentration measurement [parts per million (ppm), Bedfont Scientific, Maidstone, Kent UK] (exclusion criteria: < 5 cigarettes per day end exhaled CO < 10 ppm). Exclusion criteria included history of cardiovascular disease, hepatic or renal failure, active neoplasia, alcohol abuse, psychiatric illness, pregnancy, breastfeeding, cigar smoking, or the presence of any additional risk factor for cardiovascular disease (dyslipidaemia: total cholesterol > 200 mg/dl or the use of cholesterol-lowering agents; hypertension: blood pressure > 140/90 mmHg or use of anti-hypertensive drugs; diabetes mellitus: fasting plasma glucose > 125 mg/dl or use of antidiabetic drugs).
Graph: Figure 4 Flow chart of the study population. HNBC heat-not-burn cigarette, TCig tobacco cigarette.
Our study included an acute and a chronic phase. The acute phase of the study entailed an initial sham smoking session of inhaling on a non-lighted cigarette for 7 min, simulating the mean duration of a traditional cigarette smoking. In the acute phase, the participants were thereafter randomised into either a tobacco cigarette (Tcig) smoking session, using a single mainstream Tcig [Marlboro Red, Papastratos-Philip Morris International (PMI), Athens, Greece], or a single HEETS stick (PMI, amber flavour) puffing session (HNBC) using a commercially available HNBC (IQOS, PMI). Randomization was performed by an attending research nurse using a table of random numbers as reproduced from the online randomization software
Graph: Figure 5 Acute phase protocol. Following an initial sham smoking session, subjects were randomised to either a heat-not-burn or traditional cigarette smoking session; following a washout period of 60 min, they were crossed-over to the alternative smoking session. Each session was followed by a vascular stiffness examination and blood-sampling for oxidative stress and platelet activation assessment. Exam examination, HNBC heat-not-burn cigarette, TCig tobacco cigarette.
For the chronic phase, all participants of the acute phase, were instructed to replace Tcig smoking with HNBC puffing for 1 month and were compared with an external group of 25 Tcig smokers, with no intention to quit smoking, (2:1 ratio) before and after 1 month.
Exhaled CO, arterial elasticity and blood sampling for oxidative stress and platelet activation, which were assessed at baseline, after each smoking session of the acute phase and at the chronic phase. Endothelial function, coronary flow reserve and myocardial deformation were assessed at baseline and after 1 month, in the chronic study. Arterial elasticity, myocardial, endothelial function examinations were executed by a single, blinded-to-treatment and to values of measured biomarkers, operator. In the acute study the time elapsed between smoking (Tcig or HNBC) and assessment of vascular markers was approximately 10 min. For the chronic study, participants were instructed to abstain from smoking (Tcig or HNBC) in the morning before the vascular and echocardiography assessment. HNBC adherence was assessed by asking the participants to answer a questionnaire regarding the daily use of HNBC sticks as well as by measurement of the exhaled CO in each participant during a clinic visit at days 15 and 30 of the chronic study. The HNBC sticks were provided to the participants by the investigators at baseline and at day 15 during a clinic visit and after the participant had returned the empty boxes of the used HNBC sticks.
Brachial artery FMD was ultrasonically assessed in line with published methodology recommendations [
CFR was measured by transthoracic Doppler echocardiography, analysing colour-guided pulse-wave Doppler signals derived from long axis apical projections. The maximal velocity end velocity–time integral in the distal left anterior descending artery were recorded at rest and following intravenous adenosine administration, according to published methodology [
Carotid-to-femoral PWV was estimated according to a previous published methodology (Complior, Alam Medical, Vincennes, France) [
In the acute and chronic study assessment of vascular markers (FMD, PWV and PP) was performed in a random order.
Myocardial deformation was assessed by way of 2-dimensional strain measurement, with speckle-tracking analysis by dedicated software (Echopac 203, GE Horten Norway). LV apical 2-, 3-, and 4-chamber views at ≥ 50 frames per second frame rate were acquired and the global longitudinal strain (GLS) was calculated from the respective apical views, applying previously published methodology [
Myocardial work (MW) was estimated by combining echo-derived left ventricular (LV) strain with brachial blood pressure to construct LV strain-pressure curves non-invasively, following recently published methodology [
A commercially available spectrophotometry kit (Oxford Biomedical Research, Rochester Hills, Mich, colorimetric assay for lipid peroxidation; measurement range 1–20 nmol/l) was used to determine plasma MDA levels. Plasma PC levels were measured by spectrophotometrical assessment of 2,4-dinitrophenylhydrazine PC derivatives, as previously published [
In the chronic study two-dimensional echocardiography preceded the coronary flow reserve assessment, after completion of vascular studies.
A commercially available ELISA kit was used to measure blood levels of Thromboxane B2 (Thromboxane B2 EIA Kit Cayman Ann Arbor MI USA) with an assay range 1.6–1000 pg/ml.
We used the software STATA v.11 and SPSS v.22 in order to procced to data analysis. We used Shapiro–Wilk test to examine if values had normal distribution, and Levene test for evaluating data homoscedasticity, as it was previously published [
For the acute study, we planned a study of a continuous response variable from matched pairs of study subjects (HNBC and Tcig users). In a pilot study of ten smokers randomised to HNBC or Tcig and then crossed-over to the alternate smoking (Tcig or HNBC) the difference in the PWV of matched pairs after HNBC and Tcig smoking was normally distributed with standard deviation 1.3 and the true difference in the mean PWV of the matched pairs after HBNC and Tcig smoking was 0.54 m/s. Thus, we needed to study 47 pairs of subjects to be able to reject the null hypothesis that this response difference in PWV after HNBC and Tcig is zero with probability (power) 0.8. The Type I error probability associated with this test of this null hypothesis is 0.05.
For the chronic study, we planned a study of a continuous response variable from independent control (Tcig smokers) and experimental subjects (HNBC users) with 0.5 control(s) per experimental subject. In a pilot study of 10 HNBC and 5 Tcig smokers the response for the GLS within each subject group was normally distributed with a standard deviation of 3.1% and the true difference of GLS means between the HNBC and Tcig smokers was 2.3%. Thus, we needed to study at least 50 experimental and 25 control subjects to be able to reject the null hypothesis that the population means of the HNBC and Tcig smoking groups are equal with a probability (power) of 0.8. The Type I error probability associated with this test for this null hypothesis is 0.05, as previously published [
It was approved by the Attikon University Hospital scientific ethics committee (Approval number: 2874/06-12-17), registered on https://clinicaltrials.gov/ (NCT03452124, 25/02/2018). The study was conducted according to the Declaration of Helsinki and written informed consent was provided by the participants.
Our study was a single centre study. Its design does not permit to explore definite causative associations among changes in oxidative stress, vascular and myocardial function markers. We should also acknowledge as a study limitation the lack of measurement of cotinine blood or urine levels to appraise for the actual number of products smoked by our study participants and to clarify whether differences in circulating nicotine levels in addition to differences in CO production after HNBC and Tcig smoking mediate the observed differences of cardiovascular markers in our study. Long term follow-up is needed to assess whether the observed improvement in vascular and myocardial function, after switching to HBNC, is associated with reduced cardiovascular events. Cluster analysis using unsupervised machine learning techniques to identify subgroups of participants with favourable or unfavourable responses to HNBC use for the measured vascular, cardiac and biochemical markers was not performed.
Acute HNBC puffing showed a less detriment effect on arterial elasticity compared to Tcig and did not cause a further augmentation of oxidative stress burden, platelet activation, and exposure to CO compared to baseline, in contrast to acute smoking of tobacco cigarette. Switching from Tcig to HNBC for one month resulted in improved endothelial function, oxidative stress burden as well as in reduction of platelet activity and exposure to CO, while caused an improvement in coronary flow reserve and myocardial work efficiency compared with tobacco smoking.
I.I. contributed to the study design, data analysis and writing of the manuscript. D.V. contributed to data analysis and writing of the manuscript. G.K. contributed to patient recruitment, and randomization. Ka.K. contributed to patient recruitment and study design. Ko.K. performed echocardiographic studies and respective data analysis. M.T. and I.A. performed the bio markers measurement and analysis. D.A. and J.P. critically reviewed the manuscript and contributed to the scientific analysis of the results. All authors discussed the results and contributed to the final manuscript.
The study was funded by Special Account for research Grants (11645) of the National and Kapodistrian University of Athens without any direct or indirect support from Tobacco Company.
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. Anonymised data are only available upon request from the authors.
The authors declare no competing interests.
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By Ignatios Ikonomidis; Dimitrios Vlastos; Gavriela Kostelli; Kallirhoe Kourea; Konstantinos Katogiannis; Maria Tsoumani; John Parissis; Ioanna Andreadou and Dimitrios Alexopoulos
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