[Effects of air pollution on cardiovascular events in cardiac intensive care units]

Many environmental factors influence the occurrence of cardiovascular events. Among these, air pollution is certainly the most harmful, due to its dual composition and effects. Air pollution is both particulate and gaseous, and can vary in concentration and composition according to its source and type of emission. Moreover, clinical effects are not only observed at long-term but also at short-term, following rapid deterioration in air quality. Air pollution must therefore be seen both as a risk factor for atherosclerotic disease, and as a trigger for cardiovascular events. These acute effects are essentially mediated by an increased risk of acute coronary syndromes and heart failure. The effects of air pollution on admissions for ventricular arrhythmias and arterial hypertension are also possible. The cardiotoxicity of pollution is mainly mediated by sympatho-vagal imbalance, by the initiation and amplification of an oxidative, inflammatory and pro-aggregatory cascade, and by endothelial dysfunction and activation of metalloproteinases. Although now well established, the consequences of air pollution on acute cardiovascular events require further investigation. Environmental cardiology is an emerging discipline whose current vision still fails to integrate qualitative aspects, such as the oxidative potential of particulate matter, and the joint effects of multiple environmental exposures.

Impact of vessel morphology on computed tomography derived fractional flow reserve (FFRCT) in normal coronary artery disease: a novel marker for the predictor of FFRCT changes

Background

Computed tomography (CT) derived fractional flow reserve (FFRCT) decreases continuously from the proximal to the distal segments of the vessel even in normal coronary arteries. It has been empirically proved that the degree of FFRCT decline varies based on vessel morphology even in the same vessel length.

Purpose

To investigate the vessel morphological factors that influence FFRCT in normal coronary arteries.

Methods

A total of 1402 outpatients with suspected CAD who underwent CT angiography (CTA) with FFRCT analysis between January 2017 and October 2021 were evaluated. Among them, 234 consecutive patients who underwent both CT angiography including FFRCT and invasive coronary angiography, resulting in <20% stenosis in right coronary artery (RCA) were evaluated. RCA vessels from ostium to just proximal site of the posterior descending branch were analysed and divided into two groups according to distal FFRCT: FFRCT >0.80 (n=219) and FFRCT ≤0.80 (n=15). FFRCT was measured at proximal and distal segments of the RCA. Vessel morphology (vessel length, lumen diameter and volume, and plaque volume) and left ventricular mass were assessed. The ratio of lumen volume and vessel length was defined as the V/L ratio.

Results

Whereas vessel length was almost the same between FFRCT >0.80 and ≤0.80 (>0.80 vs. ≤0.80, 115.9±17.3 vs. 119.6±28.7 mm), lumen volume (1135.2±369.3 vs. 906.2±362.6 mm3, p<0.05) and V/L ratio (9.8±2.6 vs. 7.5±2.3, p<0.01) were significantly higher in FFRCT >0.80. Distal FFRCT correlated with plaque-related parameters [low-attenuation plaque, intermediate-attenuation plaque, and calcified plaque (CP)] and vessel-related parameters (proximal and distal vessel diameter, vessel length, lumen volume, and V/L ratio). Among all vessel-related parameters, V/L ratio showed the highest correlation with distal FFRCT (r=0.44, p<0.0001) (Figure 1). Multivariable analysis showed that CP volume was the strongest predictor of distal FFRCT (β-coefficient = −0.38, p<0.0001), followed by V/L ratio (β-coefficient = 0.95, p=0.007). V/L ratio was the strongest predictor of a distal FFRCT ≤0.80 (cut-off 8.2, AUC 0.73, sensitivity 66.7%, specificity 69.3%, 95% CI 0.60–0.86) (Figure 2).

Conclusions

Our study findings suggest that the V/L ratio can be a measure to predict subclinical coronary perfusion disturbance.

Funding Acknowledgement

Type of funding sources: None.

Effects of left ventricular mass index on computed tomography derived fractional flow reserve in significant obstructive coronary artery disease

Background

In significant obstructive coronary artery disease (SOCAD), a mismatched assessment of the severity of coronary artery stenosis may occur between invasive coronary angiography and computed tomography (CT) derived fractional flow reserve (FFRCT). The exact mechanisms of unexpected underestimation of FFRCT remain unknown.

Purpose

The aims of this study are (1) to clarify the mechanisms of underestimation on FFRCT; and (2) to identify the predictive factors of FFRCT underestimation above the value of 0.80 in SOCAD vessels.

Methods

A total of 1160 outpatients who underwent CT angiography (CTA) with FFRCT analysis for suspected coronary artery disease (CAD) between January 2017 and June 2020 were evaluated. Among them, 141 consecutive patients who had both CTA coupled to FFRCT analysis and invasive angiogram showing >75% coronary stenosis were included for analysis. Vessels were divided into two groups according to FFRCT at the distal vessel: FFRCT >0.80 (n=12) and FFRCT ≤0.80 (n=153). Vessel-related parameters, including vessel morphology (vessel length and lumen volume) and plaque components (non-calcified plaque volume and calcified plaque volume) and left ventricular (LV) myocardial-related parameters, including LV wall thickness at each site of the myocardium, and LV mass were evaluated semi-automatically.

Results

Vessel morphology and plaque components did not differ between FFRCT >0.80 and ≤0.80, whereas LV wall thickness (average; 10.7±2.7 vs. 8.4±1.6 mm, and maximal; 13.5±3.0 vs. 10.6±1.8 mm, all p value <0.001), LV mass (136.4±38.4 vs. 98.8±26.8 g, p<0.001), and LV mass index (73.8±22.6 vs. 51.8±12.2 g/m2, p<0.001) were significantly higher in FFRCT >0.80. Next, we investigated the parameters that correlated with FFRCT. Of all, vessel morphology and plaque components were not related to FFRCT, whereas maximal LV wall thickness, r=0.24, p=0.01; LV mass, r=0.19. p=0.04; and LV mass index, r=0.30, p=0.001) correlated with FFRCT. In the vessels showing FFRCT >0.80, only LV mass (r=0.84, p=0.005) and LV mass index (r=0.67, p=0.047) correlated with FFRCT. (Figure 1). LV mass index was the strongest predictor of a distal FFRCT of >0.80 with the area under curve (AUC) 0.81, 95% CI 0.62 – 1.00, P<0.0001 and an optimal cut-off value of 66.5 g/m2 sensitivity 77.8%, specificity 89.6% (Figure 2).

Conclusions

FFRCT is affected not by vessel-related parameters but LV myocardial-related parameters in SOCAD. The presence of an excessive LV mass is a major predictor of underestimation of FFRCT in SOCAD vessels. LV myocardial-related parameters should be considered when interpreting numerical values of FFRCT to avoid the possibility of overlooked SOCAD.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

Impact of vascular morphology and plaque characteristics on computed tomography derived fractional flow reserve in early stage coronary artery disease

Background

FFRCT gradually decreases from the proximal to the distal part of a vessel and reach the pathological threshold for significant ischemia even in the absence of obstructive coronary artery disease (CAD). The exact mechanisms of such gradual FFRCT decline remain unknown.

Purpose

The aims of this study are (1) to clarify the mechanisms of the gradual decline of computed tomography (CT) derived fractional flow reserve (FFRCT); and (2) to identify the predictive factors of an FFRCT decline below the pathological value of 0.80 in no apparent CAD vessels.

Methods

A total of 1058 outpatients with suspected CAD and who underwent CT angiography (CTA) with FFRCT analysis between January 2017 and December 2019 were evaluated. Among them, 150 consecutive patients who had both a CTA coupled to an FFRCT analysis and an invasive angiogram showing <25% coronary stenosis were included for analysis. Vessels were divided into two groups according to FFRCT at the distal vessel: FFRCT >0.80 (n=317) and FFRCT ≤0.80 (n=114). ΔFFRCT was defined as the magnitude of the change in FFRCT from the proximal to the distal vessel. Plaque characterization and vessel morphology measurements were performed semi-automatically. Vessel constituents were characterized based on Hounsfield units (HU) into lumen volume (<−50 HU), non-calcified plaque (NCP) (−50–150 HU), and calcified plaque (>150 HU).

Results

FFRCT decreased continuously from the proximal to distal across the three major vessels in both FFRCT>0.80 and FFRCT ≤0.80 groups (Figure 1). Compared to FFRCT>0.80 group, NCP volume was significantly higher in all three major vessels in FFRCT ≤0.80 group (210.2±83.6 mm3 vs. 140.9±139.3 mm3 for the RCA, p=0.01; 177.5±150.2 mm3 vs. 133.2±112.2 mm3 for the LAD, p=0.04; 127.6±91.5 mm3 vs. 58.7±57.7 mm3 for the LCX, p<0.01). Next, we investigated the vessel parameters that correlated with ΔFFRCT. ΔFFRCT was correlated with lumen volume in FFRCT>0.80 group (r=−0.24, p<0.0001), whereas ΔFFRCT was correlated with NCP volume in FFRCT ≤0.80 group (r=0.42, p<0.001) (Figure 2). An NCP volume above 44.8 mm3 was the strongest predictor of distal FFRCT of ≤0.80 (area under the curve 0.69, p<0.0001, sensitivity 95%, specificity 39%).

Conclusions

FFRCT is affected by vascular morphology and plaque characteristics even in the early stage of coronary artery disease. Our study highlights that subclinical coronary artery disease strongly influences FFRCT by effects unrelated to coronary stenosis. The presence of NCP is a major predictor of the gradual decrease of FFRCT toward pathological values. Anatomical findings as vessel morphology and plaque characteristics should be taken into consideration when interpreting numerical values of FFRCT to avoid unnecessary referrals for invasive coronary angiography or percutaneous coronary intervention.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

P854Physiological patterns of coronary artery disease

Background

Randomised controlled trials have confirmed the clinical benefit of invasive functional assessment to guide clinical decision making about myocardial revascularisation in patients with stable coronary artery disease. Treatment decision is based on one FFR value which provides a vessel-level metric as a surrogate of myocardial ischaemia. Also, the distribution of epicardial conductance can be evaluated using an FFR pullback manoeuvre.

Purpose

The objective of the present study is to characterise the physiological patterns of CAD using motorised coronary pressure pullbacks during continuous hyperaemia in patients with stable coronary artery disease.

Methods

Prospective, multicentre study of patients undergoing clinically-indicated coronary angiography. A pullback device, adapted to grip the coronary pressure wire, was set at a speed of 1 mm/sec. The pattern of CAD was adjudicated by visual inspection of the FFR pullback curves as focal, diffuse, or a combination of both mechanisms. Also, a quantitative classification of the physiological pattern of CAD was performed based on (1) the functional contribution of the epicardial lesion in relation to the total vessel FFR (Δlesion FFR/Δvessel FFR) and (2) the length (mm) of epicardial coronary segments with FFR drops in relation to the total vessel length. The combination of these two ratios, namely, lesion-related pressure drops (%FFR-lesion), and the extent of functional disease, resulted in the functional outcomes index (FOI), a metric that represents the pattern of CAD (i.e. focality or diffuseness) based on coronary physiology. Agreement on CAD patterns and between observers was assessed using Fleiss' Kappa. Analysis of variance (ANOVA) was used to compared quantitative variables. Correlation between variables was assessed by the Pearson moment coefficient.

Results

One hundred and fifty-eight vessels were included; 984,813 FFR values were used to generate the FFR pullback curves. Using motorised FFR pullbacks, 34% of the vessel disease patterns (i.e. focal, diffuse or combined) were reclassified compared to conventional angiography. The mean contribution of the angiographic lesions to the distal FFR (%FFR-lesion) was 61.7±25% whereas vessel length with the physiological disease was 59.8±21% of the total vessel length. The mean FOI was 0.61±0.17, and differentiated focal from diffuse CAD in terms of %FFR-lesion (p<0.001) and physiological extent of CAD (p<0.001).

Conclusion

Coronary angiography was inaccurate to assess the patterns of CAD. The inclusion of the functional component reclassified 34% of the vessel disease patterns (i.e. focal, diffuse or combined). A new metric, the FOI, based on the functional impact of anatomical lesions and the extent of physiological disease, discriminated focal from diffuse CAD. Further clinical trials are required to evaluate the usefulness of FOI for clinical decision making and outcomes.

P809Effects of air temperature and pollution on Takotsubo cardiomyopathy

Background

Air temperature and pollution are the main environmental factors influencing cardiovascular mortality and risk of myocardial infarction. Takotsubo cardiomyopathy (TCM) is a transient and reversible myocardial dysfunction whose cause and pathogenesis remain incompletely understood, but which, unlike acute coronary syndrome, does not involve obstructive coronary atherosclerosis or plaque rupture. The potential role of the environment on the risk to develop TCM remains poorly defined.

Methods

We aimed to study the effects of air temperature, particulate matter (PM) and gaseous pollutants (NO2 and ozone) on hospitalization rate forTCM.

All hospitalizations in Belgian Hospitals for TCM (ICD 9:429.83) from 2009 to 2014 were recorded. National air pollution parameters were extracted from the Belgian Environment Agency database. A time-stratified and temperature-matched (except for air temperature effect) case-crossover analysis of the risk of TCM was performed. The main analysis focused on 0-day lag time (lag 0) between exposure and TCM; a lag structure analysis up to lag 4 was also performed.

Results

1840 patients were included in the study (88% women). More TCM occurred during the warm compared to the cold period (fig.1; chi2p value <0.05). At lag 0, each decrease of 1°C in ambient air temperature increased the odds ratio (OR) of TCM of 1.020 (IC 95%: 1.003–1.035). This effect was more pronounced during the cold period and at lag 4 (RR 1.060; IC 95%: 1.031–1.091). Conversely, during the warm period and between lag 1 and 4, an increase of 1°C in ambient air temperature increased the RR of TCM (OR 1.053 at lag 3; IC 95%: 1.021–1.086). No significant association was found between TCM and PM10, PM2.5, NO2at any lag. During the warm period, each increase in 10μg/m3 in ozone from lag 1 to 3 increased the risk of TCM (OR 1.089 at lag 3, IC 95%: 1.017–1.168).

Conclusions

Air temperature strongly influences the onset of TCM. Both cold spells and heat waves seem to be associated with the development of TCM. Ozone exposure also increases the risk of TCM during the warm period, whereas particulate and NO2 pollution do not seem to play a significant role. These patterns seem to differ from those previously reported with STEMI.

P855Evaluation of epicardial coronary resistance using computed tomography angiography

Background

A Fractional flow reserve (FFR) pullback allows assessing the distribution of pressure loss along the vessel. FFR derived from CT (FFRCT) provides a virtual pullback curve that may also aid in the assessment of epicardial coronary resistance in the non-invasive setting.

Purpose

The present study aims to determine the accuracy of the virtual FFRCT pullback curve using a motorized invasive FFR pullback as reference in patients with stable coronary artery disease.

Methods

This is a single centre, prospective study of patients with stable coronary artery disease in whom FFRCT was performed as standard of care for non-invasive assessment. Patients referred to coronary angiography with clinically indicated invasive FFR measurement were included. FFRCT and invasive FFR values were extracted from coronary vessels every 1 mm to generate pullback curves. Invasive FFR pullbacks were acquired using a dedicated device at a speed of 1 mm/s. The area under the pullback curve (AUPC), defined as the sum of areas under the FFR pullback curve, was compared between FFRCT and invasive FFR pullbacks. Lesions were defined based on invasive angiography. FFR gradients in lesions and non-obstructive segments were defined as the difference between FFR values at the proximal and distal edge of the segments. FFR vessel gradient was defined as the difference between the most distal FFR value and the FFR at the ostium of the vessel. Mixed effect model was used to account for the correlation of FFR values within vessels. The agreement between FFRCT and FFR gradients was assessed using the Passing Bablok regression analysis and Bland-Altman methods at the vessel, lesion and non-obstructive level.

Results

A total of 3172 matched FFRCT and FFR values were obtained in 24 vessels. The correlation coefficient between FFRCT and FFR was 0.76 (95% CI 0.75 to 0.78; p<0.001). The mean difference between the FFRCT and invasive FFR pullback values was 0.07 (LOA −0.11 to 0.24). AUPC was similar between FFRCT and invasive FFR (79.0±16.1 vs. 85.3±16.4, p=0.097); the mean slope of FFRCT pullback curve was steeper compared to invasive FFR (p<0.001). The mean difference in lesion gradient was −0.07 (LOA −0.26 to 0.13) and −0.01 (LOA −0.06 to 0.05) in non-obstructive segments. There were no systematic or proportional differences between FFRCT and FFR gradients either in lesion or non-obstructive segments); however, vessel gradients were overestimated by FFRCT with a bias of −0.12 (LOA −0.35 to 0.12) driven by a higher mean difference in lesion gradients (−0.07; 95% CI −0.26 to 0.13).

Conclusions

The evaluation of epicardial coronary resistance using coronary CT angiography with FFRCT was feasible. FFRCT pullbacks were accurate in the assessment of lesion and non-obstructive gradients. FFRCT can identify the physiological pattern of coronary artery disease in the non-invasive setting.

Ecology of the cardiovascular system: Part II - A focus on non-air related pollutants

An integrated exposomic view of the relation between environment and cardiovascular health should consider the effects of both air and non-air related environmental stressors. Cardiovascular impacts of ambient air temperature, indoor and outdoor air pollution were recently reviewed. We aim, in this second part, to address the cardiovascular effects of noise, food pollutants, radiation, and some other emerging environmental factors. Road traffic noise exposure is associated with increased risk of premature arteriosclerosis, coronary artery disease, and stroke. Numerous studies report an increased prevalence of hypertension in people exposed to noise, especially while sleeping. Sleep disturbances generated by nocturnal noise are followed by a neuroendocrine stress response. Some oxidative and inflammatory endothelial reactions are observed during experimental session of noise exposure. Moreover, throughout the alimentation, the cardiovascular system is exposed to persistent organic pollutants (POPs) as dioxins or pesticides, and plastic associated chemicals (PACs), such as bisphenol A. Epidemiological studies show positive associations of exposures to POPs and PACs with diabetes, arteriosclerosis and cardiovascular disease incidence. POPs and PACS share some abilities to interact with nuclear receptors activating different pathways leading to oxidative stress, insulin resistance and angiotensin potentiation. Regarding radiation, survivors of nuclear explosion have an excess risk of cardiovascular disease. Dose-effect relationships remain debated, but an increased cardiovascular risk at low dose of radiation exposure may be of concern. Some emerging environmental factors like electromagnetic fields, greenspace and light exposure may also require further attention. Non-air related environmental stressors also play an important role in the burden of cardiovascular disease. Specific methodologies should be developed to assess the interactions between air and non-air related pollutants.

Air pollution and ST-elevation myocardial infarction: A case-crossover study of the Belgian STEMI registry 2009-2013

BACKGROUND

Previous studies have shown that air pollution particulate matter (PM) is associated with an increased risk for myocardial infarction. The effects of air pollution on the risk of ST-elevation myocardial infarction (STEMI), in particular the role of gaseous air pollutants such as NO₂ and O₃ and the susceptibility of specific populations, are still under debate.

METHODS

All patients entered in the Belgian prospective STEMI registry between 2009 and 2013 were included. Based on a validated spatial interpolation model from the Belgian Environment Agency, a national index was used to address the background level of air pollution exposure of Belgian population. A time-stratified and temperature-matched case-crossover analysis of the risk of STEMI was performed.

RESULTS

A total of 11,428 STEMI patients were included in the study. Each 10μg/m³ increase in PM10, PM2.5 and NO₂ was associated with an increased odds ratio (ORs) of STEMI of 1.026 (CI _95%: 1.005-1.048), 1.028 (CI _95%: 1.003-1.054) and 1.051 (CI _95%: 1.018-1.084), respectively. No effect of O₃ was found. STEMI was associated with PM10 exposure in patients ≥75y.o. (OR: 1.046, CI _95%: 1.002-1.092) and with NO₂ in patients ≤54y.o. (OR: 1.071, CI _95%: 1.010-1.136). No effect of air pollution on cardiac arrest or in-hospital STEMI mortality was found.

CONCLUSION

PM2.5 and NO₂ exposures incrementally increase the risk of STEMI. The risk related to PM appears to be greater in the elderly, while younger patients appear to be more susceptible to NO₂ exposure.

[Renal denervation: new treatment for refractory hypertension?]

Sympathetic renal hyperactivity is involved hypertension and in its progression towards organ damages. Using femoral access, a dedicated ablation catheter can be inserted into the renal vessels to deliver high frequency energy in the arterial wall. This therapy leads to a focal heating, which ablates the renal nerve fibers running in the adventitia. First clinical results (Simplicity HTN 1 and HTN 2 trials) have demonstrated a significant and sustained decrease in office blood pressure. The response rate to this therapy was about 85 to 90%. This procedure did not cause serious adverse event and seems to have also positive impact on glucose metabolism and exercise capacity. Based on these first results, renal denervation appears as a new interesting therapy, which requires further studies to better define its place in the antihypertensive therapeutic arsenal. Actually, it should not be considered as an alternative to pharmacological therapy and renal denervation should be only proposed to patients with resistant hypertension. Prior to renal denervation, an upstream work has to be done to ensure an adequate patient selection. The mandatory point is to ensure that patient scheduled for this therapy respond to the definition of arterial resistant hypertension. Because of the narrowed limit between the very common situation of "uncontrolled" hypertension and the "true resistant" group, we proposed a 3 steps algorithm that can help for patient selection.

Facial cooling and peripheral chemoreflex mechanisms in humans

AIM

Reductions in arterial oxygen partial pressure activate the peripheral chemoreceptors which increase ventilation, and, after cessation of breathing, reduce heart rate. We tested the hypothesis that facial cooling facilitates these peripheral chemoreflex mechanisms.

METHODS

Chemoreflex control was assessed by the ventilatory response to hypoxia (10% O2 in N2) and the bradycardic response to voluntary end-expiratory apnoeas of maximal duration in 12 young, healthy subjects. We recorded minute ventilation, haemoglobin O2 saturation, RR interval (the time between two R waves of the QRS complex) and the standard deviation of the RR interval (SDNN), a marker of cardiac vagal activity throughout the study. Measurements were performed with the subject's face exposed to air flow at 23 and 4 degrees C.

RESULTS

Cold air decreased facial temperature by 11 degrees C (P < 0.0001) but did not affect minute ventilation during normoxia. However, facial cooling increased the ventilatory response to hypoxia (P < 0.05). The RR interval increased by 31 +/- 8% of the mean RR preceding the apnoea during the hypoxic apnoeas in the presence of cold air, compared to 17 +/- 5% of the mean RR preceding the apnoea in the absence of facial cooling (P < 0.05). This increase occurred despite identical apnoea durations and reductions in oxygen saturation. Finally, facial cooling increased SDNN during normoxia and hypoxia, as well as during the apnoeas performed in hypoxic conditions (all P < 0.05).

CONCLUSION

The larger ventilatory response to hypoxia suggests that facial cooling facilitates peripheral chemoreflex mechanisms in normal humans. Moreover, simultaneous diving reflex and peripheral chemoreflex activation enhances cardiac vagal activation, and favours further bradycardia upon cessation of breathing.

Acute effect of sidestream cigarette smoke extract on vascular endothelial function

Acute exposure to passive smoking adversely affects vascular function by promoting oxidative stress and endothelial dysfunction. However, it is not known whether tobacco sidestream (SS) smoke has a greater deleterious effect on the endothelium than non-tobacco SS smoke and whether these effects are related to nicotinic endothelial stimulation. To test these hypotheses, endothelial-dependent relaxation and superoxide anion production were assessed in isolated rat aortas incubated with tobacco SS smoke, non-tobacco SS smoke, or pure nicotine. Tobacco SS smoke decreased the maximal relaxation to acetylcholine (Ach) from 79 +/- 6% to 57 +/- 7.3% (% inhibition of phenylephrine-induced plateau, P < 0.001) and increased superoxide anion production from 31 +/- 9.7 to 116 +/- 24 count/10 sec/mg (P < 0.01, lucigenin-enhanced chemiluminescence technique). The non-tobacco SS smoke extract had no significant effect on the response to Ach but increased superoxide anion production in the aortic wall to 133 +/- 2 count/10 sec/mg (P < 0.001). Furthermore, concentration-response curves to Ach and superoxide production remained unaltered with nicotine (0.001, 0.01, or 0.1 mM). In conclusion, despite similar increases in vascular wall superoxide production with tobacco and non-tobacco SS smoke, only the tobacco SS smoke extracts affected endothelium-dependent vasorelaxation. Nicotine alone does not reproduce the effects seen with tobacco SS smoke, suggesting that the acute endothelial toxicity of passive smoking cannot simply be ascribed to a nicotine-dependent mechanism.