Development and validation of non-invasive endothelial shear stress (ESS) estimations of coronary artery haemodynamics using computational modelling

Background

Vascular remodelling is influenced by various biomechanical forces such as endothelial shear stress (ESS) and is associated with development and progression of coronary artery disease (CAD). ESS is the parallel frictional force exerted by blood flow on the endothelial luminal surface of the arterial wall. While ESS may not be the only cause of atherosclerosis, it is postulated that low ESS creates a pro-atherogenic environment and high ESS is athero-protective. Computational fluid dynamics (CFD) is an engineering method used to analyse fluid flow and has been increasingly applied to simulate ESS in cardiovascular research. However, current CFD-derived ESS estimates have never been validated and can display significant variability between research groups.

Purpose

This study aims to provide a comparative analysis of coronary flow using in-silico modelling of coronary flow and particle image velocimetry (PIV).

Methods

A proximal left anterior descending (pLAD) coronary phantom model was constructed from a patient who had received same day cardiac computed tomography angiography (CTCA) and invasive coronary haemodynamic (Combowire XT) assessment. Patient-specific coronary flow data was applied to CFD boundary conditions and a mock circulatory loop. CFD was validated using PIV under steady flow in a 4-times-scaled model. Same plane velocity field and flow patterns (at mid-luminal of pLAD) from both in-silico and in-vivo data were compared and analysed.

Results

Mean velocity contours and magnitude were analysed from CFD and PIV. Patient specific average peak velocity obtained from invasive assessment was 0.21m/s. Patient-specific velocity average from CFD was 0.22m/s. The approximated magnitude difference is 4.7%. Both same-axial average cross-sectional velocity estimated by CFD-pLAD and PIV-pLAD are 0.087m/s. Velocity contours and flow patterns simulated in the CFD were also comparable with the PIV results.

Conclusion

Simulation data from CFD correlate well with experimental PIV results. This early data allows for a non-invasive approach to determine patient-specific coronary haemodynamics (such as velocity profiling and ESS) and form the basis of personalising cardiovascular risk. Insights from this work may aid future development of a novel tool that incorporates CFD-derived ESS estimates with patient-specific risk factors to better predict rapid CAD progression.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Cardiac Society of Australia and New Zealand Monash Institute of Medical Engineering

P32 SELF–LEARN IMPLEMENTATION OF ULTRASOUND FOR THE STUDY AND ULTRASOUND–GUIDED PUNCTURE OF VASCULAR ACCESSES IN THE IMPLANTATION OF PACEMAKERS AND IMPLANTABLE DEFIBRILLATORS

Background

The vascular access represents a crucial phase in the management of complications related to the implantation of devices. After the use of the axillary vein, which allows the elimination of intrathoracic complications as well as the subclavian crush of the catheters, the ultrasound–guided approach could represent the next step for the reduction of vascular complications.

Experience

All implants performed (n = 86) by an independent operator who implemented ultrasound to minimize complications related to central access were reviewed. During the first phase, the ultrasound–guided approach involved the study of vascular accesses before the start of the implant. The assessment took place before the preparation of the sterile field, for the localization of the axillary approach and for the study of the anatomical variants. It was immediately followed by the use of skin marks. The use of markers made it possible to attempt surgical isolation of the cephalic vein as a first approach. In case of failure, or the need for multiple accesses, the transition to central access could be facilitated by the presence of skin markers. This approach have not significantly modified the probability of successful axillary vein puncture without the use of venography (75% vs 71%, p NS). In the last phase all implants were performed with ultrasound–guided puncture with sterile technique before skin incision (n = 26). The procedures involved dual chamber (61%), single chamber (19%), CRTD (11%), dual chamber ICD. Ultrasound showed all cases of hypoplastic cephalic vein (15%). In the first three months of implementation, the success rate was 71.4% with 1 self–healing case of apical pneumothorax. In the following months the success rate rapidly increased to 94.1% (p < 0.05) with no pneumo or hemothorax. The median time to effective puncture was 28 seconds (8–450sec) in the second phase. It was possible to isolate the cephalic vein in 40% of cases for two or three chamber implants.

Conclusions

The ultrasound study of the accesses performed before the incision allows to identify the anatomy and to define the course of the axillary vascular system and its relationships. When performed with a sterile approach, it allows direct ultrasound–guided puncture before the surgical incision, with a high success rate from the early stages of implementation.

Abnormal fractional flow reserve and non-hyperaemic pressure ratios in patients with severe aortic stenosis and non-obstructive coronary artery disease

Background

Fractional flow reserve (FFR) and non-hyperaemic pressure ratios (NHPRs) are well-validated tools that assess the physiological significance of coronary artery disease (CAD). Low coronary lumen to myocardial mass (V/M) ratio on CT is associated with lower FFR/NHPRs and predisposes towards ischaemia in CAD. Whilst CAD and aortic stenosis (AS) frequently co-exist, patients report angina despite obstructive disease.

Purpose

We therefore sought to study the interrelationship between V/M and invasive pressure indices in patients with severe AS.

Methods

35 patients with severe AS were prospectively recruited as part of CAST-FFR study. Patients underwent CT coronary angiography and invasive pressure-wire assessment. All pressure-indices were assessed in the left anterior descending artery (LAD). Data was extracted to calculate FFR, iFR, diastolic pressure ratios (DPR and dPR) and Diastolic Hyperaemia-free Ratio (DFR). Patient-specific V/M were extracted off-site by independent core lab.

Results

Mean age was 75±7.5 years, median V/M ratio was 20.7 and mean aortic gradient and DI were 44.3±11.6mmHg and 0.23±0.4 respectively. 79% of patients had CADRADs score of <2. There were moderate positive correlations between FFR/NHPRs and V/M, including FFR (r=0.60), PdPa (r=0.48), iFR (r=0.59), DPR (r=0.59), dPR (r=0.63), DFR (r=0.67), (all p<0.005). In patients with positive pressure assessments, 69% (FFR), 71% (iFR), 70% (DPR) and 65% (DFR) had CADRADs score <2. In severe AS, lower V/M was associated with lower pressure-indices (FFR 0.75 vs 0.86, iFR 0.79 vs 0.92, DFR 0.80 vs 0.91, all p<0.005), leading to high rates of positive physiologic assessment (FFR 88%, PdPa 72%, iFR 67%, DPR 78%, DFR 74%).

Conclusion

Patients with severe AS exhibit high rates of abnormal FFR and NHPR values, despite having no obstructive CAD. Their propensity for having abnormal physiological results is, in part, influenced by coronary volume to mass ratio. These results are important for clinicians considering using invasive physiological tools to guide revascularisation decisions in patients with severe AS.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Monash University, Cardiac Society of Australia and New Zealand Correlation between NHPR/FFR and VMInvasive pressure indices and VM

Correlation between atrial electrocardiographic indexes and left atrial enlargement in competitive athletes. From the ALMUDAINA case-control study

Background

Left atrial (LA) remodelling and enlargement in athletes is a well-kown component of the athlete's heart. However, information about the correlation between of LA enlargement and atrial electrophysiological features in athletes is scarce.

Purpose

Our aim was to characterize LA enlargement, P-wave duration, and the prevalence of interatrial block (IAB) in competitive athletes (with and without LA enlargement) and in controls.

Methods

ALMUDAINA (Analysis of Left atrial Measurements of Ultrasound Dilation Among International and National Athletes) was a nationwide, cross-sectional study involving 9 hospitals and sport clinics across Spain. Cases fulfilled the international consensus definition of a competitive athlete and were currently engaged in skill, power, mixed or endurance disciplines at a national or international level. The following P-wave parameters were analysed: 1) duration 2) voltage in lead I and 3) the presence of interatrial block (IAB). LA enlargement was defined as an indexed volume by body surface area ≥34 ml/m2, measured by transthoracic echocardiography. A contemporary cohort of otherwise healthy and active controls was used as a comparison group.

Results

Baseline clinical and echocardiographic characteristics of both cohorts are summarised in table 1 whereas electrocardiographic characteristics are displayed in table 2, respectively. 356 subjects were included, 308 athletes (mean age: 36.4±11.6 years) and 48 controls (mean age: 49.3±16.1 years). Athletes showed a higher mean LA indexed volume (29.8±8.6 vs. 25.6±8.0 mL/m2, P=0.006) and higher prevalence of LA enlargement (113 [36.7%] vs. 5 [10.4%], P<0.001), but there were no relevant differences in P-wave duration (106.3±12.5 ms vs 108.2±7.7 ms; P=0.31), voltage in lead I (0.08±0.04 vs. 0.08±0,04 mV; P=0.79) and the prevalence of IAB (40 [13.0%] vs. 4 [8.3%], P=0.36). Only a case of advance IAB was detected, in an athlete without LA enlargement. Among athletes, those with LA enlargement (113, 36.7%) had higher P-wave duration (110.3±14.1 vs. 103.0±10.9 ms, P<0.001) and a higher prevalence of interatrial blockade (23 [20.4%] vs. 17 [8.8%], P=0.004), but similar voltage of P-wave in lead I (0.08±0.003 vs. 0.08±0.05 mV, P=0.689). In a multivariate analysis, competitive training was independently associated with LA enlargement (odds ratio [OR] 14.7, 95% confidence interval [CI] 4.7–44.0; P<0.001) but was not associated with P-wave duration (OR 1.02, 95% CI: 0.99–1.04; P=0.19) or IAB (OR 1.4, 95% CI 0.7–3.1; P=0.34).

Conclusions

LA enlargement is prevalent in adult competitive athletes. However, ECG indexes of atrial electrophysiology were not different from healthy controls. Our data suggest that LA enlargement and IAB are two different entities.

Funding Acknowledgement

Type of funding sources: None.

P7 The impact of coronary calcification on diagnostic performance of workstation CT derived fractional flow reserve - a multicentre experience

Background

On-site workstation based computed tomography derived fractional flow reserve (CT-FFR) is an emerging method to assess the vessel specific ischaemia in coronary artery disease (CAD). The impact of coronary calcification on its diagnostic performance is unknown.

Purpose

To evaluate the impact of coronary calcification on the diagnostic performance of reduced-order CT-FFR at detecting vessel specific ischaemia.

Methods

This is a retrospective pooled analysis of 141 patients with suspected CAD enrolled from 3 global centres who underwent CT-coronary angiography (CTA), onsite CT-FFR and invasive FFR.  Coronary calcification was assessed by Agatston score (AS). The diagnostic performance of CT-FFR (≤0.8) and CTA (≥50%) in evaluation of vessel specific ischaemia (FFR ≤ 0.8) was assessed across AS quartiles (Q1-4). A comparison of diagnostic performance of the low to mid AS (Q1 to Q3) versus high AS (Q4) was performed.

Results

Mean age and median AS was 65.8 ± 9.9 and 327.3 (interquartile range = 78.5 – 798.1). Diagnostic accuracy, sensitivity and specificity of CT-FFR for low-mid AS (0-798) and high AS (799-4019) were 77.4% vs 82.9%; 78.9% vs 94.7%; 68.8% vs 76.5% respectively with no statistical difference between the two groups.  The AUC for ischaemia of CT-FFR in low to mid AS was comparable with AUC in the high AS (0.76 [95% CI: 0.66-0.86] vs 0.84 [0.69-0.99]; P = 0.397).  The AUC for ischemia for CT-FFR in both low to mid AS and high AS was significantly higher than for CTA (0.76 [0.66-0.86] vs 0.57 [0.50-0.64]; P = 0.003 and 0.84 [0.69-0.99] vs 0.48 [0.38-0.57]; P < 0.001 respectively).

Conclusion

On-site workstation CT-FFR demonstrated consistently high diagnostic performance in patients with high AS. Its diagnostic performance was superior when compared with significant stenosis assessment on CTA across all spectrum of Agatston scores.

P6187Multicentre diagnostic performance of on-site workstation CT derived fractional flow reserve

Background

On-site workstation based computed tomography derived fractional flow reserve (CT-FFR) is an emerging method to assess vessel specific ischaemia in coronary artery disease (CAD). Global data on its diagnostic performance when compared with CT coronary angiography (CTA) is limited.

Purpose

To evaluate the on-site multicentre diagnostic performance of reduced-order CT-FFR at detecting vessel specific ischaemia.

Method

This is a retrospective pooled analysis of 141 patients (204 vessels) with suspected CAD enrolled from 3 global centres who underwent CTA, onsite CT-FFR and invasive FFR. On-site CT-FFR was performed using a reduced order model on a standard desktop computer with dedicated software. The per vessel diagnostic performance of CT-FFR (≤0.8) for vessel specific ischemia (FFR≤0.8) was compared with CTA (≥50% stenosis).

Results

Mean age was 65.8±9.9, 70.7% were male. FFR significant stenosis was present in 34.3% (70/204) of vessels. Pearson correlation of CT-FFR for invasive FFR was 0.52, P<0.001. Bland Altman analysis demonstrated a mean difference of 0.06±0.15 (95% limits of agreement −0.22 to 0.35). Per vessel diagnostic accuracy, sensitivity and specificity of CT-FFR and CTA were 79.9% vs 53.5%; 78.6% vs 85.7%; 80.6% vs 35.9% respectively. Diagnostic performance as assessed by area under the receiver operator curve (AUC) for CT FFR was superior to CTA (0.82 [95% CI 0.76–0.88] vs 0.61 [0.55–0.67]; P<0.001).

Conclusion

On-site workstation CT-FFR demonstrated high per vessel diagnostic performance and was superior when compared with CTA in assessment of vessel specific ischaemia as assessed by invasive FFR in a multicentre setting.

Changes in clinical, pulmonary function, quality of life and costs in a cohort of asthmatic patients followed for 10 years

Few studies have comprehensively assessed the evolution asthma disease in recent years.

OBJECTIVES

To determine changes in morbidity, lung function and quality of life and to establish the impact in terms of cost in a cohort of patients with asthma.

METHODS

Prospective, descriptive and realistic study that included 220 asthma patients evaluated 10 years after their inclusion (1994-2004). For all the patients, data for symptoms, lung function, quality of life and financial cost were collected.

RESULTS

There was a decrease in the frequency of health service visits, including: emergency room visits for asthma exacerbations, 0.3 (0.9) versus 0.6 (1) visits per patient per year (P=.003); a reduction in the severity of the disease, with a greater proportion of patients with mild asthma, 121 (54.8%) versus 94 (42.7%) (P=.001); a decrease (improvement in quality of life) in the total SGRQ, 30.1 (16.5) versus 37 (19.6) (P<.001); and reduced total costs, 1,464€ (3,415.8) compared to 2,267€ (4.174) per patient/year (P<.001), mainly due to indirect costs, 617.50€ (2855.9) compared to 1,320.10€ (3,685.3) per patient/year (P=.001). When assessing the changes observed according to asthma severity, no differences were observed between groups.

CONCLUSIONS

The evolution of the morbidity and quality of life of asthma patients between 1994 and 2004 are clearly favorable. This improvement provided a significant reduction in the total costs of disease treatment.

Costs of asthma according to the degree of severity

An increase in asthma-related morbidity and mortality has been reported recently, resulting in a substantial increase in the economic impact of this condition. Little information is available relating to the costs of asthma depending on the degree of severity of the disease. Total, direct and indirect costs generated by asthma patients who sought medical care for asthma control over a one-year period in a northern area of Spain were determined. Data were obtained from the patients themselves and severity of illness was classified into mild, moderate and severe according to the International Consensus Report on Diagnosis and Treatment of Asthma, 1992. The average total annual asthma-derived cost was estimated at US$2,879 per patient, with averages of US$1,336 in mildly asthmatic patients, US$2,407 in moderate asthma and US$6,393 in severe asthma. At all levels of severity, indirect costs were twice as high as direct costs, and at the same degree of severity, direct costs due to medication and hospitalization were higher among females than males. A minority of severe asthmatics incurred some 41% of the total costs. The cost of asthma was surprisingly high and varied substantially depending on the degree of severity of the disease. Further knowledge of the costs of asthma across various levels of severity will contribute to a better characterization of optimal intervention strategies for asthma care.

[Clinical characteristics and morbidity in stable asthma. A descriptive analysis of asthma in a Mediterranean community]

Scarce clinical and epidemiological data related to asthma are available in Spain.

OBJECTIVES

a) to determine the severity of disease and morbidity among symptomatic asthmatics, and b) to determine whether international recommendations for the treatment of asthma are being followed. A prospective descriptive study enrolling asthmatics older than 14 years of age who experienced symptoms within the past year. The study was performed in the Osona district, a semi-rural area north of Barcelona. Spirometric tests were given and case histories taken, including symptoms caused by the disease. The international guidelines analyzed were those published in 1992 by the National Institutes of Health for the International Consensus Report on Diagnosis and Treatment of Asthma. We studied 333 patients; 214 (64%) were women and 119 (36%) men. Asthma was mild in 140 (42%), moderate in 116 (35%) and severe in 77 (23%). The need for short-term oral corticosteroids, visits to primary care physicians, and missed work days were all significantly greater among patients with severe asthma than for those with mild or moderate asthma. However, 23% of the patients with mild asthma missed work at least once. Drugs used were beta-adrenergic agonists of short duration of effect (76%) and inhaled corticosteroids (66%).

CONCLUSIONS

a) in most symptomatic asthma patients, disease is mild; b) although patients with severe asthma have higher rates or morbidity, patients with mild disease also have marked symptoms; c) the drugs used for treatment are in compliance with the 1992 international guidelines.

[Inhalation chambers: an alternative to the conventional inhalator?]

BACKGROUND

Aerosol inhalers constitute the most commonly used form of administration of medication by most of the patients with respiratory disease although incorrect usage is a demonstrated fact in many studies. A previous study demonstrated that, despite correct instruction by health care staff and the patients, 30% of the same use these inhalers incorrectly. In the present study, the efficacy of inhalation chambers (750 ml) and spacers (50 ml) versus the conventional inhaler was evaluated by quantification of bronchodilator response.

METHODS

Fifty-six stable patients with chronic obstruction to air flow in habitual treatment with aerosol inhalers (AI) were studied. For this study 27 patients used the chamber and 29 the spacer. The patients using the maneuvers correctly (n = 42) and those that did not (n = 14) were studied together and separately.

RESULTS

Patients using the inhaler incorrectly were found to benefit significantly from either of the procedures. Upon comparison of the chambers (750 ml) with the spacers (50 ml) a significant improvement was observed with the former.

CONCLUSIONS

The response to bronchodilator treatment in patients not using aerosol inhalers correctly improves significantly upon use of either inhalation chambers or spacers with the former demonstrating the best results.

[A study of the tobacco habit in a general hospital]

Health professionals are the individuals with the greatest capacity to influence the population on smoking habit. Unfortunately, recent statistics, report that this professional group smoke as much if not more than the rest of the population, thus difficulting the reduction of this social problem. In order to evaluate smoking habit in our hospital, we presented a study on the prevalence and attitude of smoking habit in all the personnel working in our hospital. We were negatively surprised that after several public campaigns on the subject, the prevalence of smoking amongst the hospital personnel.

Anomalous coronary arteries: a report of 2 cases of single coronary artery

One patient with chronic exertional angina, not significant electrocardiographic signs of myocardial ischemia at exercise stress test and recent onset of angina at rest underwent coronary arteriography. A second one with known severe aortic stenosis underwent cardiac catheterization and coronary arteriography because of effort chest pain and syncope. A single coronary artery originating respectively from the right and from the left sinus of Valsalva but without significant coronary stenosis was detected in both patients. This entity is a quite uncommon finding of relevant interest if surgical treatment is required and good prognosis if not associated with additional cardiac anomalies.