Prehospital Activation of the Cardiac Catheterization Laboratory in ST-Segment-Elevation Myocardial Infarction for Primary Percutaneous Coronary Intervention.

Background Prehospital activation of the cardiac catheter laboratory is associated with significant improvements in ST-segment-elevation myocardial infarction (STEMI) performance measures. However, there are equivocal data, particularly within Australia, regarding its influence on mortality. We assessed the association of prehospital activation on performance measures and mortality in patients with STEMI treated with primary percutaneous coronary intervention from the Queensland Cardiac Outcomes Registry (QCOR). Methods and Results Consecutive ambulance-transported patients with STEMI treated with primary percutaneous coronary intervention were analyzed from January 1, 2017 to December 31, 2020 from the QCOR. The total and direct effects of prehospital activation on the primary outcomes (30-day and 1-year cardiovascular mortality) were estimated using logistic regression analyses. Secondary outcomes were STEMI performance measures. Among 2498 patients (mean age: 62.2±12.4 years; 79.2% male), 73% underwent prehospital activation. Median door-to-balloon time (34 minutes [26-46] versus 86 minutes [68-113]; P<0.001), first-electrocardiograph-to-balloon time (83.5 minutes [72-98] versus 109 minutes [81-139]; P<0.001), and proportion of patients meeting STEMI targets (door-to-balloon <60 minutes 90% versus 16%; P<0.001), electrocardiograph-to-balloon time <90 minutes (62% versus 33%; P<0.001) were significantly improved with prehospital activation. Prehospital activation was associated with significantly lower 30-day (1.6% versus 6.6%; P<0.001) and 1-year cardiovascular mortality (2.9% versus 9.5%; P<0.001). After adjustment, no prehospital activation was strongly associated with increased 30-day (odds ratio [OR], 3.6 [95% CI, 2.2-6.0], P<0.001) and 1-year cardiovascular mortality (OR, 3.0 [95% CI, 2.0-4.6]; P<0.001). Conclusions Prehospital activation of cardiac catheterization laboratory for primary percutaneous coronary intervention was associated with significantly shorter time to reperfusion, achievement of STEMI performance measures, and lower 30-day and 1-year cardiovascular mortality.

Impact of cyclic bending on coronary hemodynamics.

It remains unknown that the degree of bias in computational fluid dynamics results without considering coronary cyclic bending. This study aims to investigate the influence of different rates of coronary cyclic bending on coronary hemodynamics. To model coronary bending, a multi-ring-controlled fluid-structural interaction model was designed. A coronary artery was simulated with various cyclic bending rates (0.5, 0.75 and 1 s, corresponding to heart rates of 120, 80 and 60 bpm) and compared against a stable model. The simulated results show that the hemodynamic parameters of vortex Q-criterion, temporal wall shear stress (WSS), time-averaged WSS (TaWSS) and oscillatory shear index (OSI) were sensitive to the changes in cyclic rate. A higher heart rate resulted in higher magnitude and larger variance in the hemodynamic parameters. Whereas, the values and distributions of flow velocity and relative residence time (RRT) did not show significant differences between different bending periods. This study suggests that a stable coronary model is not sufficient to represent the hemodynamics in a bending coronary artery. Different heart rate conditions were found to have significant impact on the hemodynamic parameters. Thus, cyclic bending should be considered to mimic the realistic hemodynamics in future patient-specific coronary hemodynamics studies.

The Prognostic Value of Echocardiographic Wall Motion Score Index in ST-Segment Elevation Myocardial Infarction.

Background: When compared to left ventricular ejection fraction (LVEF), previous studies have suggested the superiority of wall motion score index (WMSI) in predicting cardiac events in patients who have suffered acute myocardial infarction. However, there are limited studies assessing WMSI and mortality in ST-segment elevation myocardial infarction (STEMI). We aimed to compare the prognostic value of WMSI in a cohort of STEMI patients treated with primary percutaneous coronary intervention (PCI). Methods: A comparison of WMSI, LVEF, and all-cause mortality in STEMI patients treated with primary PCI between January 2008 and December 2020 was performed. The prognostic value of WMSI, LVEF, and traditional risk scores (TIMI, GRACE) were compared using multivariable logistic regression modelling. Results: Among 1181 patients, 27 died within 30-days (2.3%) and 49 died within 12 months (4.2%). WMSI ≥1.8 was associated with poorer survival at 12-months (9.2% vs 1.5%; p < 0.001). When used as the only classifier for predicting 12-month mortality, the discriminatory ability of WMSI (area under the curve (AUC): 0.77; 95% CI: 0.68-0.84) was significantly better than LVEF (AUC: 0.71; 95% CI: 0.61-0.79; p=0.034). After multivariable modelling, the AUC was comparable between models with either WMSI (AUC: 0.89; 95% CI: 0.85-0.94) or LVEF (AUC: 0.87; 95% CI: 0.83-0.92; p < 0.08) yet performed significantly better than TIMI (AUC: 0.71; 95% CI: 0.62-0.79; p < 0.001), or GRACE (AUC: 0.63; 95% CI: 0.54-0.71; p < 0.001) risk scores. Conclusions: When examined individually, WMSI is a superior predictor of 12-month mortality over LVEF in STEMI patients treated with primary PCI. When examined in multivariable predictive models, WMSI and LVEF perform very well at predicting 12-month mortality, especially when compared to existing STEMI risk scores.

Clinical Outcomes in Pre-Hospital Activation and Direct Cardiac Catheterisation Laboratory Transfer of STEMI for Primary PCI.

INTRODUCTION: Pre-hospital activation and direct cardiac catheterisation laboratory (CCL) transfer of ST segment elevation myocardial infarction (STEMI) has previously been shown to improve door-to-balloon (DTB) times yet there is limited outcome data in the Australian context. We aimed to assess the impact of pre-hospital activation on STEMI performance measures and mortality. METHODS: Prospective cohort study of consecutive ambulance transported STEMI patients treated with primary percutaneous coronary intervention (PCI) patients over a 10-year period (1 January 2008-31 December 2017) at The Prince Charles Hospital, a large quaternary referral centre in Brisbane, Queensland Australia. Comparisons were performed between patients who underwent pre-hospital CCL activation and patients who did not. STEMI performance measures, 30-day and 1-year mortality were examined. RESULTS: Amongst 1,009 patients included (mean age: 62.8 yrs±12.6), pre-hospital activation increased over time (26.6% in 2008 to 75.0% in 2017, p<0.001). Median DTB time (35 mins vs 76 mins p<0.001) and percentage meeting targets (DTB<60 mins 92% vs 27%, p<0.001) improved significantly with pre-hospital activation. Pre-hospital activation was associated with significantly lower 30-day (1.0% vs 3.5%, p=0.007) and 1-year (1.2% vs 7.7%, p<0.001) mortality. After adjusting for confounders and mediators, we observed a strong total effect of pre-hospital activation on 1-year mortality (OR 5.3, 95%CI 2.2-12.4, p<0.001) compared to patients who did not have pre-hospital activation. False positive rates were 3.7% with pre-hospital activation. CONCLUSION: In patients who underwent primary PCI for STEMI, pre-hospital activation and direct CCL transfer is associated with low false positive rates, significantly reduced time to reperfusion and lower 30-day and 1-year mortality.

Impact of Patient BMI on Patient and Operator Radiation Dose During Percutaneous Coronary Intervention.

AIMS: This study sought to investigate patient and operator radiation dose in patients undergoing percutaneous coronary intervention (PCI) and the impact of body mass index (BMI) on patient and operator dose. METHODS: In patients undergoing PCI, radiation dose parameters, baseline characteristics and procedural data were collected in a tertiary centre for 3.5 years. Operators wore real time dosimeters. Patients were grouped by BMI. Dose area product (DAP) and operator radiation dose were compared across patient BMI categories. Multivariable analysis was performed to investigate the impact of patient BMI and other procedural variables on patient and operator dose. RESULTS: 2,043 patients underwent 2,197 PCI procedures. Each five-unit increase in BMI increased patient dose (expressed as DAP) by an average 31% (95% CI: 29-33%) and operator dose by 27% (95% CI: 20-33%). Patient dose was 2.3 times higher and operator dose was 2.4 times higher in patients with a BMI>40 than for normal BMI patients. Multivariable analysis indicated that there were many procedural factors that were predictors for increasing operator dose and patient dose but that patient BMI was a major contributor for both operator dose and patient dose. CONCLUSION: Increasing BMI increases the DAP and operator dose for PCI procedures and BMI is demonstrated to be a major factor that contributes to both patient and operator radiation dose.

Prognostic Value of Cardiac Magnetic Resonance Imaging in Acute Coronary Syndrome Patients With Troponin Elevation and Nonobstructive Coronary Arteries.

OBJECTIVE: To define the diagnostic yield of cardiac magnetic resonance (CMR) in differentiating the underlying causes of myocardial infarction with nonobstructive coronary arteries (MINOCA) and to determine the long-term prognostic implications of such diagnoses. METHODS: Cardiac magnetic resonance evaluation was performed in 227 patients (mean age, 56.4±14.9 years; 120 [53%] female) with a "working diagnosis" of MINOCA as defined by presentation with a troponin-positive acute coronary syndrome (troponin I >0.04 µg/L) and nonobstructed coronary arteries between January 1, 2007, and February 28, 2013. Follow-up was performed to assess the primary composite end point of myocardial infarction, heart failure, and all-cause mortality. RESULTS: Cardiac magnetic resonance identified nonstructural cardiomyopathies in 97 (43%) patients, myocardial infarction in 55 (24%) patients, structural cardiomyopathies in 27 (12%) patients, and pulmonary embolism in 1 patient. No CMR abnormalities were identified in the remaining patients. Kaplan-Meier analysis demonstrated the ability of a CMR diagnosis to predict the risk of the primary composite end point (P=.005) at 5-year follow-up. Worse outcomes were seen among patients with "true" MINOCA and a normal CMR image compared with those with CMR-confirmed myocardial infarction (P=.02). Use of antiplatelets (78% [37/45] vs 95% [52/55]; P=.01), beta blockers (56% [25/45] vs 82% [45/55]; P=.004), and statins (64% [29/45] vs 85% [47/55]; P=.01) was significantly lower in patients with true MINOCA with normal CMR imaging compared with those with CMR-confirmed myocardial infarction. CONCLUSIONS: Cardiac magnetic resonance carries a high diagnostic yield in patients with MINOCA and predicts long-term prognosis. Patients with MINOCA with normal CMR imaging had an increased rate of major adverse cardiac events and lower use of guideline-recommended myocardial infarction therapy compared with those with CMR-confirmed myocardial infarction.

Case Report: Evaluating Biomechanical Risk Factors in Carotid Stenosis by Patient-Specific Fluid-Structural Interaction Biomechanical Analysis.

BACKGROUND: Carotid atherosclerosis is one of the main underlying inducements of stroke, which is a leading cause of disability. The morphological feature and biomechanical environment have been found to play important roles in atherosclerotic plaque progression. However, the biomechanics in each patient's blood vessel is complicated and unique. METHOD: To analyse the biomechanical risk of the patient-specific carotid stenosis, this study used the fluid-structure interaction (FSI) computational biomechanical model. This model coupled both structural and hemodynamic analysis. Two patients with carotid stenosis planned for carotid endarterectomy were included in this study. The 3D models of carotid bifurcation were reconstructed using our in-house-developed protocol based on multisequence magnetic resonance imaging (MRI) data. Patient-specific flow and pressure waveforms were used in the computational analysis. Multiple biomechanical risk factors including structural and hemodynamic stresses were employed in post-processing to assess the plaque vulnerability. RESULTS: Significant difference in morphological and biomechanical conditions between 2 patients was observed. Patient I had a large lipid core and serve stenosis at carotid bulb. The stenosis changed the cross-sectional shape of the lumen. The blood flow pattern changed consequently and led to a complex biomechanical environment. The FSI results suggested a potential plaque progression may lead to a high-risk plaque, if no proper treatment was performed. The patient II had significant tandem stenosis at both common and internal carotid artery (CCA and ICA). From the results of biomechanical factors, both stenoses had a high potential of plaque progression. Especially for the plaque at ICA branch, the current 2 small plaques might further enlarge and merge as a large vulnerable plaque. The risk of plaque rupture would also increase. CONCLUSIONS: Computational biomechanical analysis is a useful tool to provide the biomechanical risk factors to help clinicians assess and predict the patient-specific plaque vulnerability. The FSI computational model coupling the structural and hemodynamic computational analysis, better replicates the in vivo biomechanical condition, which can provide multiple structural and flow-based risk factors to assess plaque vulnerability.

Optical coherence tomography: fundamentals and clinical utility.

Although coronary angiography is the standard method employed to assess the severity of coronary artery disease and to guide treatment strategies, it provides only 2D image of the intravascular lesions. In contrast, intravascular imaging modalities such as optical coherence tomography (OCT) produce cross-sectional images of the coronary arteries at a far greater spatial resolution, capable of accurately determining vessel size as well as plaque morphology, eliminating many of the disadvantages inherent to angiography. This review will discuss the role of OCT in the catherization laboratory for the assessment and management of coronary disease.

Optical coherence tomography-based patient-specific coronary artery reconstruction and fluid-structure interaction simulation.

Plaque rupture is related to the mechanical stress it suffered. The value and distribution of the mechanical stress in plaque could help on assessing plaque vulnerability. To look into the stress conditions in the coronary artery, a patient-specific coronary model was created by using optical coherence tomography (OCT) and angiography imaging data. The reconstructed coronary model consisted of the structure of the lumen, the arterial wall and plaque components. Benefited by the high resolution of OCT, detailed structures such as the thin fibrous cap could be observed and built into the geometry. On this reconstructed coronary model, a fully coupled fluid-structure interaction (FSI) simulation was performed. The principle stress in coronary plaque and the wall shear stress (WSS) were analyzed. The FSI simulation results show that the cap thickness had a significant effect on the stress, and the principle stress at the thin cap area was more than double of those at the locations with a larger thickness. WSS is thought as an important parameter to assess the potentially dangerous areas of the atherosclerosis-prone (caused by low WSS) and the plaque rupture (high WSS). From the WSS plots of our FSI model, the area with abnormal WSS value was detected around the position where a lipid core existed. The FSI simulation results were compared with the results from the conventional structure-only and the computational fluid dynamics (CFD)-only computational models to quantify the difference between the three models. We found little difference in the principle stress results between the FSI and the structure-only model, but a significant difference between the FSI and the CFD-only model when looking into the WSS. The WSS values at the two observation spots from the CFD-only model were higher than the values from the FSI model by 17.95% and 22.66% in average, respectively. Furthermore, the FSI model detected more areas of low WSS, because the fluid domain could expand circumferentially when pressure loaded on the flexible arterial. This study suggests that OCT-based FSI model may be useful for plaque vulnerability assessment and it may be critical to perform the FSI simulation if an accurate WSS value is required.

Carotid Bifurcation With Tandem Stenosis-A Patient-Specific Case Study Combined in vivo Imaging, in vitro Histology and in silico Simulation.

A patient-specific carotid bifurcation with tandem stenosis found at both internal carotid artery (ICA) and common carotid artery (CCA) was studied. The in vivo pre-carotid endarterectomy (pre-CEA) multi-spectral magnetic resonance imaging (MRI) were performed and in vitro post-CEA carotid plaque tissue sample was collected. MR imaging data and tissue sample staining histology were used to recognize the plaque components. Further, the computational fluid dynamics (CFD) were performed on four MR-based reconstructed 3D carotid bifurcation models (the patient-specific geometry with tandem stenosis and three presumptive geometries by removing the stenosis part). The flow and shear stress behavior affected by the tandem stenosis was analyzed. From the results of MR segmentation and histology analysis, plaque lipid pool and calcification were found at both ICA and CCA. From the result of CFD simulation, the flow shear stress behavior suggested the tandem stenosis as a more "dangerous" situation than a single-stenosis artery. Besides, the CFD results deduced that the stenosis at the CCA location formed initially and led to the subsequent formation of stenosis at ICA. This study suggests that when planning CEA, CFD simulation on the presumptive models could help clinicians to estimate the blood flow behavior after surgery. Particular attention should be paid to the case of tandem stenosis, as the local hemodynamic environment is more complex and treatment of one stenosis may lead to a variation in the hemodynamic loading on the second plaque, which may result in either a higher risk of plaque rupture or restenosis.

Diagnostic accuracy of intracoronary optical coherence tomography-derived fractional flow reserve for assessment of coronary stenosis severity.

AIMS: A novel method for computation of fractional flow reserve (FFR) from optical coherence tomography (OCT) was developed recently. This study aimed to evaluate the diagnostic accuracy of a new OCT-based FFR (OFR) computational approach, using wire-based FFR as the reference standard. METHODS AND RESULTS: Patients who underwent both OCT and FFR prior to intervention were analysed. The lumen of the interrogated vessel and the ostia of the side branches were automatically delineated and used to compute OFR. Bifurcation fractal laws were applied to correct the change in reference lumen size due to the step-down phenomenon. OFR was compared with FFR, both using a cut-off value of 0.80 to define ischaemia. Computational analysis was performed in 125 vessels from 118 patients. Average FFR was 0.80±0.09. Accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for OFR to identify FFR ≤0.80 was 90% (95% CI: 84-95), 87% (95% CI: 77-94), 92% (95% CI: 82-97), 92% (95% CI: 82-97), and 88% (95% CI: 77-95), respectively. The AUC was higher for OFR than minimal lumen area (0.93 [95% CI: 0.87-0.97] versus 0.80 [95% CI: 0.72-0.86], p=0.002). Average OFR analysis time was 55±23 seconds for each OCT pullback. Intra- and inter-observer variability in OFR analysis was 0.00±0.02 and 0.00±0.03, respectively. CONCLUSIONS: OFR is a novel and fast method allowing assessment of flow-limiting coronary stenosis without pressure wire and induced hyperaemia. The good diagnostic accuracy and low observer variability bear the potential of improved integration of intracoronary imaging and physiological assessment.

Cerebral Microcirculation and Histological Mapping After Severe Head Injury: A Contusion and Acceleration Experimental Model.

BACKGROUND: Cerebral microcirculation after severe head injury is heterogeneous and temporally variable. Microcirculation is dependent upon the severity of injury, and it is unclear how histology relates to cerebral regional blood flow. OBJECTIVE: This study assesses the changes of cerebral microcirculation blood flow over time after an experimental brain injury model in sheep and contrasts these findings with the histological analysis of the same regions with the aim of mapping cerebral flow and tissue changes after injury. METHODS: Microcirculation was quantified using flow cytometry of color microspheres injected under intracardiac ultrasound to ensure systemic and homogeneous distribution. Histological analysis used amyloid precursor protein staining as a marker of axonal injury. A mapping of microcirculation and axonal staining was performed using adjacent layers of tissue from the same anatomical area, allowing flow and tissue data to be available from the same anatomical region. A mixed effect regression model assessed microcirculation during 4 h after injury, and those results were then contrasted to the amyloid staining qualitative score. RESULTS: Microcirculation values for each subject and tissue region over time, including baseline, ranged between 20 and 80 ml/100 g/min with means that did not differ statistically from baseline flows. However, microcirculation values for each subject and tissue region were reduced from baseline, although their confidence intervals crossing the horizontal ratio of 1 indicated that such reduction was not statistically significant. Histological analysis demonstrated the presence of moderate and severe score on the amyloid staining throughout both hemispheres. CONCLUSION: Microcirculation at the ipsilateral and contralateral site of a contusion and the ipsilateral thalamus and medulla showed a consistent decline over time. Our data suggest that after severe head injury, microcirculation in predefined areas of the brain is reduced from baseline with amyloid staining in those areas reflecting the early establishment of axonal injury.

Pre-hospital ambulance notification and initiation of treatment of ST elevation myocardial infarction is associated with significant reduction in door-to-balloon time for primary PCI.

BACKGROUND: Mortality in ST elevation myocardial infarction (STEMI) is strongly predicted by the time from first medical contact to reperfusion. The aim of this study was to examine the impact of pre-hospital diagnosis by paramedics in the field on the door-to-balloon (DTB) times of patients with ST elevation myocardial infarction undergoing primary percutaneous intervention. METHODS: Paramedics in the field identified patients with ST elevation myocardial infarction on a 12-lead electrocardiograph, activated the cardiac catheter laboratory team from the field and initiated therapy with anticoagulants and antiplatelet agents in the pre-hospital setting. This cohort of patients was compared to a similar group of patients without pre-hospital diagnosis and notification. The primary outcome measure was DTB times. A secondary end point was mortality at 30 days and mortality at six months. RESULTS: A total of 281 patients, mean age of 61.1±12.9 years underwent primary percutaneous intervention with pre-hospital notification occurring in 63 cases. DTB times were lower in those with pre notification than in those without pre-hospital notification (40.4 vs. 75.6 minutes, p<0.001). This represented a 47.6% shorter DTB time. A non-statistically significant mortality reduction at one month and six months was observed in the pre-hospital notification group (1.6 versus 4.3%, p= 0.307 and 1.6 versus 6.4%, p= 0.203, respectively). CONCLUSION: Pre-hospital intervention at our centre had a powerful effect in reducing the time to reperfusion in patients with STEMI undergoing primary percutaneous intervention.

A rare mechanism of very late bare metal stent thrombosis--role of optical coherence imaging in its evaluation and management.

Very late stent thrombosis is an uncommon event following implantation with bare metal stents (BMS) in coronary arteries. Long term follow up studies have shown that a small number of BMS develop very late thrombosis following years of stability. Atherosclerotic transformation of neointimal tissue is increasingly being recognised as the cause of these adverse events. A 49 year-old male presented with acute inferior wall myocardial infarction resulting from thrombosis of the BMS implanted in his right coronary artery five years earlier. He was successfully thrombolysed and his coronary angiogram showed mild diffuse instent restenosis. The intravascular optical coherence tomography revealed instent neoatherosclerotic plaque rupture without any flow limiting stenosis as the likely culprit event.

Impact of optimising fluoroscopic implant angles on paravalvular regurgitation in transcatheter aortic valve replacements - utility of three-dimensional rotational angiography.

AIMS: The clinical value of optimising implant angles during transcatheter aortic valve replacements (TAVR) remains undefined. The Aortic Valve Guide (AVG) is a proprietary software that provides structured analysis of three-dimensional images from rotational angiography (DynaCT). This study compares AVG with preprocedural multislice computed tomography (MSCT) and DynaCT in optimal implant angle prediction for TAVR, and evaluates if an optimised implant angle is associated with reduced paravalvular regurgitation (PVR). METHODS AND RESULTS: One hundred and six consecutive patients were included, comprising three groups. Group 1 (n=19) underwent no preprocedural MSCT or DynaCT (or AVG); Group 2 (n=44) underwent periprocedural DynaCT, without AVG; Group 3 (n=43) had DynaCT with AVG. Implant angles yielded were graded as excellent, satisfactory or poor. Group 3 were more likely than Groups 2 and 1 to have excellent implant angles (83.7% vs. 52.3% vs. 42.1%, respectively, p=0.001). In 100 patients who had 30-day transthoracic echocardiogram follow-up, an excellent implant angle was significantly more likely to be associated with no PVR than a non-excellent angle (41.3% vs. 21.6%, respectively, p=0.045), independent of operator experience and THV used. CONCLUSIONS: Optimising implant angles may be important in reducing PVR. This is significantly more likely to be achieved with AVG rotational angiography.

Comparison between integrated backscatter intravascular ultrasound and 64-slice multi-detector row computed tomography for tissue characterization and volumetric assessment of coronary plaques.

BACKGROUND: The purpose of this study was to determine the cut-off values of Hounsfield units (HU) for the discrimination of plaque components and to evaluate the feasibility of measurement of the volume of plaque components using multi-detector row computed tomography (MDCT). METHODS: Coronary lesions (125 lesions in 125 patients) were visualized by both integrated backscatter intravascular ultrasound (IB-IVUS) and 64-slice MDCT at the same site. The IB values were used as a gold standard to determine the cut off values of HU for the discrimination of plaque components. RESULTS: Plaques were classified as lipid pool (n =50), fibrosis (n =65) or calcification (n =35) by IB-IVUS. The HU of lipid pool, fibrosis and calcification were 18 ± 18 HU (-19 to 58 HU), 95 ± 24 HU (46 to 154 HU) and 378 ± 99 HU (188 to 605 HU), respectively. Using receiver operating characteristic curve analysis, a threshold of 50 HU was the optimal cutoff values to discriminate lipid pool from fibrosis. Lipid volume measured by MDCT was correlated with that measured by IB-IVUS (r =0.66, p <0.001), whereas fibrous volume was not (r =0.21, p =0.059). CONCLUSION: Lipid volume measured by MDCT was moderately correlated with that measured by IB-IVUS. MDCT may be useful for volumetric assessment of the lipid volume of coronary plaques, whereas the assessment of fibrosis volume was unstable.