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Funding Acknowledgements Type of funding sources: None. BACKGROUND The coronary collateral circulation is a preformed network of anastomotic connections acting as a "natural bypass" mechanism. Whilst the prevalence of collaterals varies between species, approximately 25% of patients have angiographically visible robust collaterals at the time of ST elevation myocardial infarction. While the presence of collaterals is associated with improved outcomes, the magnitude of myocardial perfusion which can be provided by the collateral circulation remains uncertain. PURPOSE The aim was to quantify collateral myocardial perfusion during experimental coronary balloon occlusion in patients with CAD. METHODS The study was approved by the local investigational review board, and all patients provided informed consent. Patients without prior infarction, bypass surgery, or angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel, underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 hours after PTCA. RESULTS The study included 21 patients (median [interquartile range] age 70 [56-74] years, 52% male). The degree of diameter stenosis of treated vessels ranged from 60-99%, with successful PTCA performed with a mean 5-minute balloon occlusion time, resulting in ≤20% residual stenosis in all cases. The vessels undergoing PTCA were 6 in the LAD, 5 in the LCx, and 10 in the RCA. For the cohort, the size of the perfusion defect was 16 [8-30]% of the LV and the collateral perfusion at rest within the perfusion defect was 64 [58-68]% of normal perfusion within that region. Collateral perfusion was negatively correlated with perfusion defect size (R2 = 0.85, p Abstract Figure. Collateral perfusion during occlusion.

Background Wall shear stress (WSS) plays an important role in coronary atherosclerosis. Low WSS is associated with inflammation, endothelial dysfunction, and progression of atherosclerosis; while high WSS leads to vulnerable plaque transformation and future myocardial infarction. Defining the relationship between WSS and the currently available coronary physiology indices would provide valuable insights into potential mechanisms for predicting future adverse cardiac events. Purpose To investigate the relationship between WSS and the coronary epicardial/microvascular physiology indices. Methods Patients undergoing coronary angiography and physiology testing were prospectively recruited. Physiology measurements were performed under resting and hyperaemic conditions using a pressure/temperature sensor guidewire. Fractional flow reserve (FFR), non-hyperaemic pressure ratios (NHPRs), coronary flow reserve (CFR), and corrected index of microcirculatory resistance (IMR) were measured. The NHPRs including resting full-cycle ratio (RFR), resting distal/aortic pressure (Pd/Pa), instantaneous wave-free ratio (iFR), diastolic pressure ratio (dPR) and diastolic hyperaemia-free ratio (DFR) were derived offline by a blinded expert reader. Values of FFR ≤0.80, NHPR ≤0.89, CFR 25 were considered ischaemic/abnormal. Computational fluid dynamics analysis was performed and fluid motion equations were solved using finite-volume based software. The inlet and outlet boundary conditions were set to the patient-specific Pa and Pd respectively. The lesion WSS, mean WSS in five segments (WSSupstream = 5mm proximal to lesion, WSSprox = proximal third of lesion, WSSmid = middle third of lesion, WSSdistal = distal third of lesion, WSSdownstream = 5mm distal to lesion), and the total area of low WSS (defined as Results A total of 112 vessels from 93 patients were included in the study. The total area of low WSS was significantly larger in lesions with ischaemic FFR, NHPRs, and CFR values (Figure B), and not significantly different in lesions with abnormal IMR values. There was no significant difference in lesion WSS between groups stratified by all physiology indices. Within the lesion WSS sub-segments, WSSprox was significant higher in ischaemic lesions stratified by normal/abnormal FFR, iFR, and dPR (4.2 vs 3.3 Pa, 4.2 vs 3.3 Pa, 4.3 vs 3.3 Pa respectively, all p=0.04), and not significantly different when stratified by RFR, DFR, Pd/Pa, CFR, and IMR. Conclusion Functionally significant coronary lesions classified by the epicardial physiology indices have significantly larger total area of low WSS and higher WSSprox which may explain the higher cardiovascular event rates in patients with ischaemic lesions. There was no significant relationship between WSS and coronary microcirculatory resistance. Figure 1 Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National Heart Foundation of Australia Health Professional Scholarship

Introduction Patients with Coronary Artery Disease (CAD) are exposed to myocardial ischemia and hypoxia, resulting in altered autonomic function. Obstructive sleep apnoea (OSA) is highly prevalent in CAD and is associated with increased sympathetic activity which could further exacerbate cardiovascular risk. We aimed to determine whether OSA severity is associated with altered autonomic function in CAD patients. Methods Patients presenting to the coronary care unit with CAD underwent level 2 portable polysomnography to assess the presence and severity of OSA. Autonomic function was calculated from continuous blood pressure and 3-lead ECG 5 minute recordings while awake. Mean spontaneous baroreceptor sensitivity (sBRS msec/mmHg); vagally mediated heart rate variability (HRV) markers (pNN50%, RMSSD, HF-HRV); and, sympathetically mediated vascular autonomic function (LF-BPV) were measured. Autonomic function was assessed in relation to OSA severity (Apnoea Hypopnea Index, AHI; oxygen desaturation index, ODI). Results OSA was present in 49/51 (96%) participants with CAD (age 54±9 years; BMI 28.9±5.4 kg/m2; male 41(77%)). No association was found between sBRS and AHI. There was a modest inverse correlation between AHI and vagally mediated HRV (RMSSD, r= -0.28 p=0.04; HF, r= -0.31 p=0.03). AHI positively correlated with LF-SBP (r=0.29, p=0.04) suggesting upregulation of sympathetic modulation. Linear regression analyses, adjusted for age, sex, and BMI, showed AHI was a determinant of parasympathetically modulated HRV measures (pNN50% -0.25(0.12), p=0.05). Conclusions In patients with CAD, increased AHI was associated with parasympathetic withdrawal suggesting that OSA could increase poor cardiovascular prognosis in this population.

Aims Identification and management of the Standard Modifiable Cardiovascular Risk Factors (SMuRFs; hypercholesterolaemia, hypertension, diabetes and smoking) has substantially improved cardiovascular disease outcomes. However, cardiovascular disease remains the leading cause of death worldwide. Suspecting an evolving pattern of risk factor profiles in the ST elevation myocardial infarction (STEMI) population with the improvements in primary care, we hypothesized that the proportion of 'SMuRFless' STEMI patients may have increased. Methods/results We performed a single centre retrospective study of consecutive STEMI patients presenting from January 2006 to December 2014. Over the study period 132/695 (25%) STEMI patients had 0 SMuRFs, a proportion that did not significantly change with age, gender or family history. The proportion of STEMI patients who were SMuRFless in 2006 was 11%, which increased to 27% by 2014 (odds ratio 1.12 per year, 95% confidence interval: 1.04-1.22). The proportion of patients with hypercholesterolaemia decreased (odds ratio 0.92, 95% confidence interval 0.86-0.98), as did the proportion of current smokers (odds ratio 0.93, 95% confidence interval 0.86-0.99), with no significant change in the proportion of patients with diabetes and hypertension. SMuRF status was not associated with extent of coronary disease; in-hospital outcomes, or discharge prescribing patterns. Conclusion The proportion of STEMI patients with STEMI poorly explained by SMuRFs is high, and is significantly increasing. This highlights the need for bold approaches to discover new mechanisms and markers for early identification of these patients, as well as to understand the outcomes and develop new targeted therapies.

Aims Intracoronary thrombus is disrupted by stent deployment and confounded by the development of intrastent plaque prolapse. This study aims at investigating the feasibility and repeatability of thrombus quantification prior to stent implantation using optical coherence tomography (OCT) in ST-segment elevation myocardial infarction (STEMI) patients. Methods and results Patients were enrolled in an OCT substudy of the TOTAL trial (a randomized trial of routine aspiration ThrOmbecTomy with PCI vs. PCI ALone in patients with STEMI undergoing primary PCI) of aspiration thrombectomy or percutaneous coronary intervention (PCI) alone in primary PCI (PPCI) of STEMI. Using OCT, thrombus burden (TB) and other measures of pre- and post-stent atherothrombus were analysed over the arterial segment defined by the final stent length. Feasibility was 86.2% (25/29 patients) for both pre- and post-stent OCT imaging. Altogether, 8111 OCT cross-sections were analysed. In Bland–Altman analyses of inter-observer variation ( n = 25), the mean pre-stent TB was 8.76% for Observer 1 and 8.97% for Observer 2 (limits of agreement −2.6 to 2.2%). In Bland–Altman analyses of intra-observer variation ( n = 15), the mean pre-stent TB was 8.06% for the first and 7.35% for the second round of analysis by Observer 1 (limits of agreement −1.72 to 3.15%). There was a good correlation between pre-stent TB and pre-stent quadrants with thrombus/mm ( r = 0.97), but only modest correlation between pre-stent TB and post-stent atherothrombotic burden (ATB; r = 0.54). Conclusions Measurement of pre-stent TB by OCT during the PPCI of STEMI is feasible and highly repeatable. Pre-stent TB is only modestly correlated with post-stent ATB, which indicates that pre-stent measurements might be of additional value when assessing the TB in STEMI.

Aims To investigate the relationship between Eustachian valve (EV) length and degree of atrial septal movement in patients with patent foramen ovale (PFO) and presumed paradoxical cerebral embolism. PFO is a well-established risk factor for cryptogenic stroke. However, due to the high prevalence of PFO, many of these are bystanders rather than true pathological entities. Other studies have sought to define which patients with PFO are particularly at risk of cryptogenic stroke by measuring various parameters of right atrial anatomy. We investigated the relationship between EV length and atrial septal movement. Methods and results Measurements of EV length and atrial septal movement were made prospectively from 72 consecutive patients referred to our centre for PFO closure following presumed cryptogenic stroke, by intracardiac phased array echocardiography. The most significant finding from this study was that patients with fewer than 10 mm atrial septal movement had significantly longer EVs than those in whom there was >10 mm septal movement ( P = 0.003). The mean EV length with >10 mm septal movement is 6.35 mm, and 13.33 mm with fewer than 10 mm movement. The prevalence of septal movement beyond 10 mm was significantly less in our series than in previously published papers. Conclusion We propose that while a large degree of atrial septal movement significantly increases propensity to cerebral embolism in patients with PFO, its absence does not negate this risk. We have shown that long EV may function independently from atrial septal movement to potentiate paradoxical embolism.

Thienopyridines are a class of drug targeting the platelet adenosine diphosphate 2 receptor. They have been shown to significantly reduce platelet activity exerting an important role in those clinical settings in which such an effect is beneficial. Ticlopidine was first to be introduced several years ago but it was quickly replaced by clopidogrel as it had a better risk/benefit profile. Recently, prasugrel has been developed and tested in several ex vivo studies and clinical trials showing able to provide a more powerful antiplatelet effect at the expense of a higher risk of bleeding complications. Great debate rose around its recent approval in the US as well as in Europe. This review aims at exploring the development and available clinical data of this third-generation thienopyridine while discussing its practical implementation in routine practice.

Cocaine causes myocardial injury through multiple mechanisms including vasoconstriction, adrenergic hyper-stimulation, and de novo thrombus formation. This report presents two cases of cocaine-induced coronary artery thrombosis with no underlying stenosis, resulting in substantial myocardial injury. A previously well 32-year-old man presented with chest pain which commenced 24 h after intranasal cocaine use. He denied use …