A Placebo-Controlled Trial of Percutaneous Coronary Intervention for Stable Angina

BACKGROUND

Percutaneous coronary intervention (PCI) is frequently performed to reduce the symptoms of stable angina. Whether PCI relieves angina more than a placebo procedure in patients who are not receiving antianginal medication remains unknown.

METHODS

We conducted a double-blind, randomized, placebo-controlled trial of PCI in patients with stable angina. Patients stopped all antianginal medications and underwent a 2-week symptom assessment phase before randomization. Patients were then randomly assigned in a 1:1 ratio to undergo PCI or a placebo procedure and were followed for 12 weeks. The primary end point was the angina symptom score, which was calculated daily on the basis of the number of angina episodes that occurred on a given day, the number of antianginal medications prescribed on that day, and clinical events, including the occurrence of unblinding owing to unacceptable angina or acute coronary syndrome or death. Scores range from 0 to 79, with higher scores indicating worse health status with respect to angina.

RESULTS

A total of 301 patients underwent randomization: 151 to the PCI group and 150 to the placebo group. The mean (±SD) age was 64±9 years, and 79% were men. Ischemia was present in one cardiac territory in 242 patients (80%), in two territories in 52 patients (17%), and in three territories in 7 patients (2%). In the target vessels, the median fractional flow reserve was 0.63 (interquartile range, 0.49 to 0.75), and the median instantaneous wave-free ratio was 0.78 (interquartile range, 0.55 to 0.87). At the 12-week follow-up, the mean angina symptom score was 2.9 in the PCI group and 5.6 in the placebo group (odds ratio, 2.21; 95% confidence interval, 1.41 to 3.47; P<0.001). One patient in the placebo group had unacceptable angina leading to unblinding. Acute coronary syndromes occurred in 4 patients in the PCI group and in 6 patients in the placebo group.

CONCLUSIONS

Among patients with stable angina who were receiving little or no antianginal medication and had objective evidence of ischemia, PCI resulted in a lower angina symptom score than a placebo procedure, indicating a better health status with respect to angina. (Funded by the National Institute for Health and Care Research Imperial Biomedical Research Centre and others; ORBITA-2 ClinicalTrials.gov number, NCT03742050.).

The Use and Efficacy of FFR-CT: Real-World Multicenter Audit of Clinical Data With Cost Analysis

BACKGROUND

Fractional flow reserve-computed tomography (FFR-CT) is endorsed by UK and U.S. chest pain guidelines, but its clinical effectiveness and cost benefit in real-world practice are unknown.

OBJECTIVES

The purpose of this study was to audit the use of FFR-CT in clinical practice against England's National Institute for Health and Care Excellence guidance and assess its diagnostic accuracy and cost.

METHODS

A multicenter audit was undertaken covering the 3 years when FFR-CT was centrally funded in England. For coronary computed tomographic angiograms (CCTAs) submitted for FFR-CT analysis, centers provided data on symptoms, CCTA and FFR-CT findings, and subsequent management. Audit standards included using FFR-CT only in patients with stable chest pain and equivocal stenosis (50%-69%). Diagnostic accuracy was evaluated against invasive FFR, when performed. Follow-up for nonfatal myocardial infarction and all-cause mortality was undertaken. The cost of an FFR-CT strategy was compared to alternative stress imaging pathways using cost analysis modeling.

RESULTS

A total of 2,298 CCTAs from 12 centers underwent FFR-CT analysis. Stable chest pain was the main symptom in 77%, and 40% had equivocal stenosis. Positive and negative predictive values of FFR-CT were 49% and 76%, respectively. A total of 46 events (2%) occurred over a mean follow-up period of 17 months; FFR-CT (cutoff: 0.80) was not predictive. The FFR-CT strategy costs £2,102 per patient compared with an average of £1,411 for stress imaging.

CONCLUSIONS

In clinical practice, the National Institute for Health and Care Excellence criteria for using FFR-CT were met in three-fourths of patients for symptoms and 40% for stenosis. FFR-CT had a low positive predictive value, making its use potentially more expensive than conventional stress imaging strategies.

Automated left ventricular dimension assessment using artificial intelligence

Background and purpose

Artificial intelligence (AI) has the potential to greatly improve efficiency and reproducibility of quantification in echocardiography, but to gain widespread use it must both meet expert standards of excellence and have a transparent methodology. We developed an online platform to enable multiple collaborators to annotate medical images for training and validating neural networks.

Methods

Using our online collaborative platform 9 expert echocardiographers labelled 2056 images that comprised the training dataset. They labelled the four points from where the standard parasternal long axis (PLAX) measurements (interventricular septum, posterior wall, left ventricular dimension) would be made. Using these labelled images we trained a 2d convolutional neural network to replicate these labels. Separately, we curated an external validation dataset of the systolic and diastolic frames of 100 PLAX acquisitions. Each of these images were labelled twice by 13 different experts, and the average of the 26 measurements was taken as the consensus standard.

We then compared the individual experts and the AI measurements on the external validation dataset to the consensus standard, and calculated the precision standard deviation (SD) of the signed differences from the consensus standard.

Results

For diastolic septum thickness, the AI had a precision SD of 1.8 mm (ICC 0.81; 95% CI 0.73 to 0.97), compared with 2.0 mm for the individual experts (ICC 0.64; 95% CI 0.57 to 0.72). For diastolic posterior wall thickness, the AI had a precision SD 1.4 mm (ICC 0.54; 95% CI 0.38 to 0.66), and the individual experts 2.2 mm (ICC 0.37; 95% CI 0.29 to 0.46).

The AI's precision SD for left ventricular internal dimension was 3.5 mm (ICC 0.93, 95% CI 0.90 to 0.94), and for individual experts was 4.4mm (ICC 0.82, 95% CI 0.78 to 0.95). Both the experts and AI performed better in diastole than systole (precision SD AI 2.5mm vs 4.3mm, p&lt;0.0001; experts 3.3mm vs 5.3mm, p&lt;0.0001).

Conclusions

AI trained by a group of echocardiography experts was able to perform PLAX measurements which matched the reference standard more closely than any individual expert's own measurements.

This open, collaborative approach may be a model for the development of AI that is explainable to, and trusted by clinicians.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIHR Imperil BRC ITMATDr Howard was additionally funded by Wellcome. Online collaborative platformResults of AI and experts

Three-month cardiac outcomes of survivors of COVID-19 presenting to a district general hospital in West Hertfordshire, UK

Background

COVID-19 is novel entity associated with significant morbidity and mortality. Most patients recover completely, however, a proportion describe persistent symptoms consistent with cardiopulmonary disturbance. The long-term cardiac and respiratory outcomes of COVID-19 are not known.

Purpose

The aim of this study was to undertake a comprehensive cardiopulmonary assessment of survivors of COVID-19 with post recovery symptoms. The cardiac findings are presented here.

Methods

Survivors of COVID-19 presenting to a general hospital in West Hertfordshire between 18 March 2020 and 15 May 2020, were reviewed at 3 months using a structured prespecified protocol. Patients with persistent symptoms and those admitted to the intensive care unit (ICU) were invited to attend a clinical assessment comprising an electrocardiogram (ECG), echocardiography, chest x-ray (CXR) and pulmonary function tests. At follow up, patients were categorised according to disease course: 1) monitored via a community based virtual hospital, 2) admitted for supplemental oxygen, 3) requiring non-invasive ventilation and 4) ICU admission.

Results

448 eligible patients were evaluated by telephone. 11 patients admitted to ICU and 147 patients with persistent symptoms were invited for further assessment. At presentation, hospitalised patients were older, had higher levels of obesity and increased rates of hypertension than those managed virtually (p&lt;0.05). Among hospitalised patients, the degree of pulmonary infiltration on CXR was higher, ROX index for intubation lower, eGFR lower, C-reactive protein levels higher and lymphocyte counts lower, compared to those managed virtually (p&lt;0.05). The prevalence of known respiratory conditions was higher among patients admitted to hospital, with a trend towards statistical significance (p=0.051). There were no differences in the prevalence of known cardiac disorders and other co-morbidities amongst both patient groups (table 1).

At follow up, CXR appearances were improved and similar among patients monitored virtually, those admitted for supplemental oxygen, those requiring non-invasive ventilation and those treated on ICU. There were no differences in heart rhythm and ECG parameters in the four patient groups. Left ventricular systolic and diastolic dimensions, Simpson's biplane ejection fraction, left atrial volume and left ventricular filling pressures were similar in all four patient groups. There were no differences in right ventricular dimensions, right ventricular fractional area change, tricuspid annular plane systolic excursion and pulmonary artery systolic pressures among patients irrespective of disease severity (table 2).

Conclusions

At 3 months, we identified no differences in ECG indices and echocardiographic parameters of left and right ventricular function among survivors of COVID-19, independent of disease course. The findings of this study argue against significant cardiac sequalae following COVID-19 infection.

Funding Acknowledgement

Type of funding sources: None.

Fully automated global longitudinal strain assessment using artificial intelligence developed and validated by a UK-wide echocardiography expert collaborative

Background

Left ventricular longitudinal strain has been reported to deliver reproducibility, sensitivity and prognostic value over and above ejection fraction. However, it currently relies on uninspectable proprietary algorithms and suffers from a lack of widespread clinical use. Uptake may be improved by increasing user trust through greater transparency.

Purpose

We therefore developed a machine-learning based method, trained, and validated with accredited experts from our AI Echocardiography Collaborative. We make the dataset, code, and trained network freely available under an open-source license.

Methods

AI enables strain to be calculated without relying on speckle tracking by directly locating key points and borders across frames. Strain can then be calculated as the fractional shortening of the left ventricular perimeter. We first curated a dataset of 7523 images, including 2587 apical four chamber, each labelled by a single expert from our collaboration of 17 hospitals, using our online platform (Figure 1). Using both this dataset and a semi-supervised approach, we trained a 3d convolutional neural network to identify the annulus, apex, and the endocardial border throughout the cardiac cycle.

Separately, we constructed an external validation dataset of 100 apical 4 chamber video-loops. The systolic and diastolic frame were identified, and each image was separately labelled by 11 experts. From these labels we then derived the expert consensus strain for each of the 100 video loops. These experts also ordered all 100 echocardiograms by their visual grading of left ventricular longitudinal function. Finally, a single expert calculated strain using two different proprietary commercial packages (A and B).

Results

Consensus strain measurements (obtained by averaging individual assessments by the 11 experts) across the 100 cases ranged from −4% to −27%, with strong correlations with the individual experts and machine methods (Figure 2). Using each cases' consensus across experts as the gold standard, median error from consensus was 3.1% for individual experts, 3.4% for Propriety A, 2.6% for Proprietary B, 2.6% for our AI.

Using the visual grading of longitudinal strain as the reference, the 11 individual experts and 4 machine methods each showed significant correlation: coefficients ranged from 0.55 to 0.69 for experts, and for Proprietary A was 0.68, Proprietary B 0.69, and our AI 0.69.

Conclusions

Our open-source, vendor-independent AI-based strain measure automatically produces values that agree with expert consensus, as strongly as the individual experts do. It also agrees with the subjective visual ranking by longitudinal function. Our open-source AI strain performs at least as well as closed-source speckle-based approaches, and may enable increased clinical and research use of longitudinal strain.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIHR Imperial BRC ITMAT.Dr Howard was additionally funded by Wellcome. Figure 1. Collaborative online platformFigure 2. Correlations between strain methods

Placebo-Controlled Efficacy of Percutaneous Coronary Intervention for Focal and Diffuse Patterns of Stable Coronary Artery Disease

[Figure: see text].

Hypertension attenuates the prognostic value of coronary artery calcification scoring in low-risk patients

OBJECTIVES

In outpatients with suspected ischaemic symptoms, we investigated the impact of risk factor profile on the prognostic value of coronary artery calcium scoring (CACS) and CT coronary angiography (CTCA).

METHODS

772 consecutive patients underwent CACS and CTCA; 52 patients (6.7%) with significant coronary artery lesions underwent revascularisation within 60 days and were excluded. 720 remaining patients were followed up for 38.1±17.4 months.

RESULTS

Late presentation (after 60 days) major adverse cardiovascular events (MACEs) were recorded in 27 patients (3.8%). Hypertension was strongly associated with adverse outcomes (unadjusted HR 6.5 (2.9 to 14), p<0.001), and hypertensive patients had double the prevalence of non-calcified plaque versus normotensive individuals (30.2% vs 14.3%, p<0.001). Adjusting for confounders, severe stenosis at CTCA was predictive of MACE for normotensive and hypertensive patients (HR 9.6 (2.8 to 43.1), p<0.001, and HR 6.2 (2.4 to 16.1), p<0.001, respectively). CACS alone was not predictive of MACE throughout the cohort (HR 1.001 (0.9997 to 1.001), p=0.36) and when adjusting for confounders, a cut-off of CACS>400 predicted MACE in normotensive individuals (HR 10.6 (2.41 to 49.3), p<0.001) but not in hypertensive individuals (HR 1.3 (0.5 to 3.6), p=0.56). Zero calcium score did not mitigate the risk of MACE (HR 0.84 (0.39 to 1.8), p=0.65) and 13/27 patients (48.1%) who suffered MACE had a 0 calcium score; all had hypertension.

CONCLUSIONS

In low-risk patients with stable cardiovascular symptoms, CTCA provides important additive prognostic information over CACS, and CACS (including CACS>400) underestimated cardiovascular risk in patients with hypertension. This may relate to the increased prevalence of non-calcified plaque in these individuals.

Role of T1 mapping in identification of convalescent Takotsubo cardiomyopathy

Funding Acknowledgements

Type of funding sources: None.

Background

Takotsubo cardiomyopathy remains an elusive entity to diagnose, especially with increasing time following the initial clinical event. Patients are often referred for cardiac MR, but when performed on a convalescent patient, the conventional CMR exam can be normal. However CMR elevated native T1 values on mapping may persist, aiding diagnosis.

Purpose

We sought to review a series of confirmed Takotsubo cases to evaluate which CMR features were most helpful in making a diagnosis.

Methods

We reviewed 2 years of CMR exams in our institution and identified 14 patients with a confirmed diagnosis of Takotsubo cardiomyopathy after a read of all clinical data by two consultant cardiologists. All of the 14 patients had a troponin positive cardiac event, unobstructed coronary arteries on invasive angiography and echocardiographic evidence of apical hypo/akinesia (or basal, in the non-apical variants) at the time of presentation. All CMR exams were performed at 1.5T. All included functional assessment, T1 mapping and late gadolinium enhancement(LGE). Some exams also included T2 mapping and STIR.

Results

All patients were female. The time interval between presentation and CMR exam varied from 24 hours to 2 years. 2 of the scans showed evidence of non-apical Takotsubo cardiomyopathy. At the time of CMR, only 7 patients(50%) had a residual regional wall motion abnormality, but 13 patients(93%) had a region of elevated native T1 (&gt;1 myocardial segment). High signal was identified on STIR in 6(43%) and elevated native T2 in 10(71%). Of interest, we identified small areas of patchy LGE in 2 patients(14%).

Conclusion

Increased native T1 signal may be the only residual cardiac MRI marker of previous Takotsubo cardiomyopathy, persisting for months after the initial cardiac event, even after resolution of regional wall motion abnormalities and recovery of the left ventricular function. T1 mapping should be performed in CMR exams for Takotsubo cardiomyopathy to improve diagnostic yield.

Abstract Figure. CMR in convalescent Takotsubo

Diffusion tensor cardiovascular magnetic resonance predicts adverse remodelling after myocardial infarction

Background

Changes in myocardial microstructure that underlie post-myocardial infarction (MI) left ventricular (LV) remodelling may contribute to progressive deterioration in cardiac function and increased risk of adverse clinical events. Diffusion Tensor Cardiovascular Magnetic Resonance (DT-CMR) derived parameters provide in vivo measures of helix angle (HA) and sheetlet angle (SA), which allow non-invasive characterization of microstructural dynamics associated with cardiac contraction.

Purpose

To evaluate the relationship between DT-CMR metrics of myocardial microstructure with the development of adverse LV remodelling and to determine the relationship between DT-CMR and strain post- MI.

Methods

We performed a longitudinal pre-clinical CMR study whereby DT-CMR, cine imaging and strain were acquired pre-MI and 3 days and 16 weeks post- MI in a pig model. HA (E1A), SA (E2A), and sheetlet angle mobility (ΔE2A = E2Asystole– E2Adiastole), as well as circumferential (Ecc) and radial (Err) strain were calculated at each timepoint and related to change in left ventricular end-diastolic volume (ΔLVEDV) and change in left ventricular end-systolic volume (ΔLVESV) between 3 days post-MI and 16 weeks post-MI. The translational value of this preclinical study was further assessed in six patients with chronic MI.

Results

ΔE2A over the whole LV (global ΔE2A) at 3 days post-MI correlated significantly with ΔLVEDV (R2=0.89, p=0.0013, Fig.1A;) and ΔLVESV (R2=0.81, p=0.0055, Fig.1B). Global Ecc at 3 days post-MI also correlated with both ΔLVEDV (R2=0.75, p=0.012, Fig.1C) and ΔLVESV (R2=0.71, p=0.018, Fig.1D). Global Err at 3 days post-MI did not show significant correlation with either ΔLVEDV (R2=0.32, p=0.19, Fig.1E) or ΔLVESV (R2=0.35, p=0.17, Fig.1F). Global ΔE2A correlated strongly with global Ecc 3 days post-MI (R2=0.9, p=0.00099, Fig.1G) but less strongly with global Err 3 days post-MI (R2=0.57, p=0.049, Fig.1H). Global ΔE2A at the chronic stage correlated significantly with ejection Fraction (EF), in both clinical (R2=0.87, p=0.007) and preclinical data (R2=0.87, p=0.0024). Global ΔE2A correlated well with LVEDV (clinical: R2=0.72, p=0.033; preclinical: R2=0.8, p=0.0066) and LVESV (clinical: R2=0.78, p=0.020; preclinical: R2=0.89, p=0.0013). In vivo E1A maps at 16 weeks post-MI and ex vivo DT-CMR demonstrated reduced right-handed helix angles in the endocardium of the infarct region.

Conclusion

ΔE2A measured at 3 day post-reperfused MI is strongly correlated with the development of increased end-systolic and end-diastolic volumes, and may therefore serve as a novel CMR early predictor of adverse LV remodelling after reperfused MI. Strong correlations between ΔE2A, LV volumes and EF in a small cohort of stable patients with remodelled hearts after chronic MI confirm the feasibility of performing these measurements in patients and the plausibility of further evaluation of ΔE2A as a predictor of adverse remodelling after reperfused MI.

Sheetlet mobility predicts volume change

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): National Institutes of Health by the Division of Intramural Research (NHLBI, NIH, DHHS); British Heart Foundation

1641 Bicuspid pulmonary valve - an unusual cause of dilated pulmonary artery

Introduction

Dilated pulmonary artery is a common finding with a variety of possible aetiologies. We present a case of unexplained dilated pulmonary artery that was associated with bicuspid pulmonary valve identified by CMR.

Case Presentation

A 67-year-old female underwent mitral valve repair for severe mitral regurgitation. She had presented with breathlessness, and had severe mitral regurgitation due to a myxomatous valve with bileaflet prolapse, confirmed with TOE. Echo showed: normal LV dimensions, LVEF 66%. RV size and systolic function normal. Coronary angiography was normal and pulmonary hypertension was not present on right heart catheterization.

At postoperative follow up she was well and asymptomatic, with echo showing good LV systolic function, intact mitral valve repair, and normal systolic pulmonary artery pressures (36mmHg). New T wave inversion was identified across the precordial leads so a CMR was performed.

CMR showed normal LV volumes and function with no wall motion abnormality or LVH. There was no fibrosis or infarction in the late phase after Gadolinium contrast. The RV was dilated (73mm diameter at base) with normal systolic function. The main pulmonary artery was dilated at 42mm. Flow mapping showed no evidence of shunt (Qp:Qs = 1:1) and the atrial septum was intact. Pulmonary valve function was normal but the valve was bicuspid in morphology.

Discussion

Bicuspid pulmonary valve is a rare finding. In our case this was identified by CMR and was associated with a dilated pulmonary artery.

Bicuspid pulmonary valve is most commonly identified in the context of pulmonary valve stenosis. Isolated pulmonary valve stenosis is a rare finding; it is most often associated with other congenital defects like Fallot. Pulmonary stenosis has been associated with pulmonary artery aneurysm, attributed to hemodynamic changes caused by the stenotic valve. However as with bicuspid aortic valve it is recognized that the "post stenotic dilation" is part of the pathology of bicuspid valve and does not need the changed haemodynamics of a stenotic valve.

During embryogenesis neural crest cells are necessary for the normal development of the semilunar valves, the septation of the outflow tract into the aorta and pulmonary artery, and the remodeling of the aortic arch. Any defect in this migration can cause abnormalities or aneurysm of the aorta or pulmonary artery together with semilunar valve defects. A study of 3,861 donor hearts dissected at the European Homograft Bank revealed only four cases (0.1%) of bicuspid pulmonary valves.

Bicuspid pulmonary valve with normal function can be difficult to identify at echocardiography. It can be well visualized by CMR and this can be combined with an assessment of the pulmonary arteries. It should be remembered as a rarer cause of dilated pulmonary artery when other causes have been excluded.

Figure

A. Dilated MPA. B. Dilated RV. C. and D. Bicuspid pulmonary valve.

Abstract 1641 Figure. Dilated MPA. Bicuspid pulmonary valve

Dobutamine Stress Echocardiography Ischemia as a Predictor of the Placebo-Controlled Efficacy of Percutaneous Coronary Intervention in Stable Coronary Artery Disease: The Stress Echocardiography-Stratified Analysis of ORBITA

BACKGROUND

Dobutamine stress echocardiography is widely used to test for ischemia in patients with stable coronary artery disease. In this analysis, we studied the ability of the prerandomization stress echocardiography score to predict the placebo-controlled efficacy of percutaneous coronary intervention (PCI) within the ORBITA trial (Objective Randomised Blinded Investigation With Optimal Medical Therapy of Angioplasty in Stable Angina).

METHODS

One hundred eighty-three patients underwent dobutamine stress echocardiography before randomization. The stress echocardiography score is broadly the number of segments abnormal at peak stress, with akinetic segments counting double and dyskinetic segments counting triple. The ability of prerandomization stress echocardiography to predict the placebo-controlled effect of PCI on response variables was tested by using regression modeling.

RESULTS

At prerandomization, the stress echocardiography score was 1.56±1.77 in the PCI arm (n=98) and 1.61±1.73 in the placebo arm (n=85). There was a detectable interaction between prerandomization stress echocardiography score and the effect of PCI on angina frequency score with a larger placebo-controlled effect in patients with the highest stress echocardiography score (P_interaction=0.031). With our sample size, we were unable to detect an interaction between stress echocardiography score and any other patient-reported response variables: freedom from angina (P_interaction=0.116), physical limitation (P_interaction=0.461), quality of life (P_interaction=0.689), EuroQOL 5 quality-of-life score (P_interaction=0.789), or between stress echocardiography score and physician-assessed Canadian Cardiovascular Society angina class (P_interaction=0.693), and treadmill exercise time (P_interaction=0.426).

CONCLUSIONS

The degree of ischemia assessed by dobutamine stress echocardiography predicts the placebo-controlled efficacy of PCI on patient-reported angina frequency. The greater the downstream stress echocardiography abnormality caused by a stenosis, the greater the reduction in symptoms from PCI.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02062593.

P2243CTCA alone demonstrates superior diagnostic accuracy, prognostic utility and is less expensive than CTCA combined with subsequent multi-modality functional imaging in patients with ischaemic symptoms

Background

The evaluation of suspected ischaemic symptoms incorporates multi-modality anatomical and functional imaging tests. The 2016 update to the UK's NICE guidelines recommends CT coronary angiogram (CTCA) first line in patients without known coronary artery disease. Additive multi-modality functional imaging may provide synergistic diagnostic and prognostic information.

Purpose

To investigate the diagnostic accuracy, prognostic utility and cost of CTCA combined with subsequent multi-modality functional testing versus (vs) CTCA alone.

Methods

772 consecutive patients were referred to a single UK tertiary centre with symptoms suggestive of ischaemia. 657 individuals (“CTCA group”) underwent CTCA alone, and 115 individuals (“Combined group”) underwent CTCA and then either perfusion cardiac MRI (n=25), stress echocardiogram (n=16), or myocardial perfusion scintigraphy (n=74). Patients underwent invasive angiography (n=79) +/− revascularisation at the discretion of the referring clinician. All readers and operators were aware of previous imaging findings. Revascularised patients (n=52) were excluded from long term follow-up. The remaining patients were followed-up for a mean of 38.1±17.4 months and the incidence of major adverse cardiovascular events (MACE) recorded. Costs were derived from the NICE guidelines.

Results

Baseline characteristics were similar between groups. The Combined group underwent significantly more invasive angiograms than the CTCA group (29.6% vs 6.8%, p=0.0001) with no significant difference in the rate of revascularisation (73% vs 67%, p=0.72). Mean time from CTCA to angiogram was significantly longer in the Combined group (81.2 vs 38.1 days, p=0.0001). Both sensitivity and specificity were lower in the Combined group than in the CTCA group (sensitivity: 70% vs 93%, specificity: 75% vs 100%). The rate of long term MACE was significantly higher in the Combined group (8.7% vs 2.6%, p=0.0026). Multivariate analysis of CTCA and functional imaging findings found that CTCA-derived four vessel aggregate stenosis score (0–12) was the strongest predictor of MACE for the whole cohort (OR 4.4, p<0.0001), and also for those with negative functional tests (OR 3.9, p<0.0001). Per patient, a combined strategy was more expensive than CTCA alone (£1551 vs £368, p=0.0001).

CTCA and functional data vs outcomes

Conclusions

Combining multi-modality functional testing with CTCA increased costs but did not improve diagnostic accuracy or long term outcomes. Further reductions in both MACE and unnecessary invasive angiography are desirable; CT-derived functional data such as FFRCT may be implicated.

Fractional Flow Reserve and Instantaneous Wave-Free Ratio as Predictors of the Placebo-Controlled Response to Percutaneous Coronary Intervention in Stable Single-Vessel Coronary Artery Disease

BACKGROUND

There are no data on how fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are associated with the placebo-controlled efficacy of percutaneous coronary intervention (PCI) in stable single-vessel coronary artery disease.

METHODS

We report the association between prerandomization invasive physiology within ORBITA (Objective Randomised Blinded Investigation With Optimal Medical Therapy of Angioplasty in Stable Angina), a placebo-controlled trial of patients who have stable angina with angiographically severe single-vessel coronary disease clinically eligible for PCI. Patients underwent prerandomization research FFR and iFR assessment. The operator was blinded to these values. Assessment of response variables, treadmill exercise time, stress echocardiography score, symptom frequency, and angina severity were performed at prerandomization and blinded follow-up. Effects were calculated by analysis of covariance. The ability of FFR and iFR to predict placebo-controlled changes in response variables was tested by using regression modeling.

RESULTS

Invasive physiology data were available in 196 patients (103 PCI and 93 placebo). At prerandomization, the majority had Canadian Cardiovascular Society class II or III symptoms (150/196, 76.5%). Mean FFR and iFR were 0.69±0.16 and 0.76±0.22, respectively; 97% had ≥1 positive ischemia tests. The estimated effect of PCI on between-arm prerandomization-adjusted total exercise time was 20.7 s (95% confidence interval [CI], -4.0 to 45.5; P=0.100) with no interaction of FFR ( P_interaction=0.318) or iFR ( P_interaction=0.523). PCI improved stress echocardiography score more than placebo (1.07 segment units; 95% CI, 0.70-1.44; P<0.00001). The placebo-controlled effect of PCI on stress echocardiography score increased progressively with decreasing FFR ( P_interaction<0.00001) and decreasing iFR ( P_interaction<0.00001). PCI did not improve angina frequency score significantly more than placebo (odds ratio, 1.64; 95% CI, 0.96-2.80; P=0.072) with no detectable evidence of interaction with FFR ( P_interaction=0.849) or iFR ( P_interaction=0.783). However, PCI resulted in more patient-reported freedom from angina than placebo (49.5% versus 31.5%; odds ratio, 2.47; 95% CI, 1.30-4.72; P=0.006) but neither FFR ( P_interaction=0.693) nor iFR ( P_interaction=0.761) modified this effect.

CONCLUSIONS

In patients with stable angina and severe single-vessel disease, the blinded effect of PCI was more clearly seen by stress echocardiography score and freedom from angina than change in treadmill exercise time. Moreover, the lower the FFR or iFR, the greater the magnitude of stress echocardiographic improvement caused by PCI.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02062593.

Association of Titin-Truncating Genetic Variants With Life-threatening Cardiac Arrhythmias in Patients With Dilated Cardiomyopathy and Implanted Defibrillators

Importance

There is a need for better arrhythmic risk stratification in nonischemic dilated cardiomyopathy (DCM). Titin-truncating variants (TTNtvs) in the TTN gene are the most common genetic cause of DCM and may be associated with higher risk of arrhythmias in patients with DCM.

Objective

To determine if TTNtv status is associated with the development of life-threatening ventricular arrhythmia and new persistent atrial fibrillation in patients with DCM and implanted cardioverter defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRT-D) devices.

Design, Setting, and Participants

This retrospective, multicenter cohort study recruited 148 patients with or without TTNtvs who had nonischemic DCM and ICD or CRT-D devices from secondary and tertiary cardiology clinics in the United Kingdom from February 1, 2011, to June 30, 2016, with a median (interquartile range) follow-up of 4.2 (2.1-6.5) years. Exclusion criteria were ischemic cardiomyopathy, primary valve disease, congenital heart disease, or a known or likely pathogenic variant in the lamin A/C gene. Analyses were performed February 1, 2017, to May 31, 2017.

Main Outcome and Measures

The primary outcome was time to first device-treated ventricular tachycardia of more than 200 beats/min or first device-treated ventricular fibrillation. Secondary outcome measures included time to first development of persistent atrial fibrillation.

Results

Of 148 patients recruited, 117 adult patients with nonischemic DCM and an ICD or CRT-D device (mean [SD] age, 56.9 [12.5] years; 76 [65.0%] men; 106 patients [90.6%] with primary prevention indications) were included. Having a TTNtv was associated with a higher risk of receiving appropriate ICD therapy (shock or antitachycardia pacing) for ventricular tachycardia or fibrillation (hazard ratio [HR], 4.9; 95% CI, 2.2-10.7; P < .001). This association was independent of all covariates, including midwall fibrosis measured by late gadolinium enhancement on cardiac magnetic resonance images (adjusted HR, 8.3; 95% CI, 1.8-37.6; P = .006). Having a TTNtv was also associated with the risk of receiving a shock (HR, 3.6; 95% CI, 1.1-11.6; P = .03). Individuals with a TTNtv and fibrosis had a greater rate of receiving appropriate device therapy than those with neither (HR, 16.6; 95% CI, 3.5-79.3; P < .001). Having a TTNtv was also a risk factor for developing new persistent atrial fibrillation (HR, 3.9; 95% CI, 1.3-12.0; P = .01).

Conclusions and Relevance

Having a TTNtv was an important risk factor for clinically significant arrhythmia in patients with DCM and ICD or CRT-D devices. Having a TTNtv, especially in combination with midwall fibrosis confirmed with cardiovascular magnetic resonance imaging, may provide a risk stratification approach for evaluating the need for ICD therapy in patients with DCM. This hypothesis should be tested in larger studies.

Large meta-analysis of genome-wide association studies identifies five loci for lean body mass

Lean body mass, consisting mostly of skeletal muscle, is important for healthy aging. We performed a genome-wide association study for whole body (20 cohorts of European ancestry with n = 38,292) and appendicular (arms and legs) lean body mass (n = 28,330) measured using dual energy X-ray absorptiometry or bioelectrical impedance analysis, adjusted for sex, age, height, and fat mass. Twenty-one single-nucleotide polymorphisms were significantly associated with lean body mass either genome wide (p < 5 × 10⁻⁸) or suggestively genome wide (p < 2.3 × 10⁻⁶). Replication in 63,475 (47,227 of European ancestry) individuals from 33 cohorts for whole body lean body mass and in 45,090 (42,360 of European ancestry) subjects from 25 cohorts for appendicular lean body mass was successful for five single-nucleotide polymorphisms in/near HSD17B11, VCAN, ADAMTSL3, IRS1, and FTO for total lean body mass and for three single-nucleotide polymorphisms in/near VCAN, ADAMTSL3, and IRS1 for appendicular lean body mass. Our findings provide new insight into the genetics of lean body mass.

Lean body mass is a highly heritable trait and is associated with various health conditions. Here, Kiel and colleagues perform a meta-analysis of genome-wide association studies for whole body lean body mass and find five novel genetic loci to be significantly associated.

Defining the role of common variation in the genomic and biological architecture of adult human height

Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explained one-fifth of the heritability for adult height. By testing different numbers of variants in independent studies, we show that the most strongly associated ∼2,000, ∼3,700 and ∼9,500 SNPs explained ∼21%, ∼24% and ∼29% of phenotypic variance. Furthermore, all common variants together captured 60% of heritability. The 697 variants clustered in 423 loci were enriched for genes, pathways and tissue types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/β-catenin and chondroitin sulfate-related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.

The South Asian genome

The genetic sequence variation of people from the Indian subcontinent who comprise one-quarter of the world's population, is not well described. We carried out whole genome sequencing of 168 South Asians, along with whole-exome sequencing of 147 South Asians to provide deeper characterisation of coding regions. We identify 12,962,155 autosomal sequence variants, including 2,946,861 new SNPs and 312,738 novel indels. This catalogue of SNPs and indels amongst South Asians provides the first comprehensive map of genetic variation in this major human population, and reveals evidence for selective pressures on genes involved in skin biology, metabolism, infection and immunity. Our results will accelerate the search for the genetic variants underlying susceptibility to disorders such as type-2 diabetes and cardiovascular disease which are highly prevalent amongst South Asians.

Genome-wide trans-ancestry meta-analysis provides insight into the genetic architecture of type 2 diabetes susceptibility

To further understanding of the genetic basis of type 2 diabetes (T2D) susceptibility, we aggregated published meta-analyses of genome-wide association studies (GWAS) including 26,488 cases and 83,964 controls of European, East Asian, South Asian, and Mexican and Mexican American ancestry. We observed significant excess in directional consistency of T2D risk alleles across ancestry groups, even at SNPs demonstrating only weak evidence of association. By following up the strongest signals of association from the trans-ethnic meta-analysis in an additional 21,491 cases and 55,647 controls of European ancestry, we identified seven novel T2D susceptibility loci. Furthermore, we observed considerable improvements in fine-mapping resolution of common variant association signals at several T2D susceptibility loci. These observations highlight the benefits of trans-ethnic GWAS for the discovery and characterisation of complex trait loci, and emphasize an exciting opportunity to extend insight into the genetic architecture and pathogenesis of human diseases across populations of diverse ancestry.

Coronary heart disease in Indian Asians

The Indian Asian population accounts for a fifth of all global deaths from coronary heart disease (CHD). CHD deaths on the Indian subcontinent have doubled since 1990, and are predicted to rise a further 50% by 2030. Reasons underlying the increased CHD mortality among Indian Asians remain unknown. Although conventional cardiovascular risk factors contribute to CHD in Indian Asians as in other populations, these do not account for their increased risk. Type-2 diabetes, insulin resistance and related metabolic disturbances are more prevalent amongst Indian Asians than Europeans, and have been proposed as major determinants of higher CHD risk among Indian Asians. However, this view is not supported by prospective data. Genome-wide association studies have not identified differences in allele frequencies or effect sizes in known loci to explain the increased CHD risk in Indian Asians. Limited knowledge of mechanisms underlying higher CHD risk amongst Indian Asians presents a major obstacle to reducing the burden of CHD in this population. Systems biology approaches such as genomics, epigenomics, metabolomics and transcriptomics, provide a non-biased approach for discovery of novel biomarkers and disease pathways underlying CHD. Incorporation of these ‘omic’ approaches in prospective Indian Asian cohorts such as the London Life Sciences Population Study (LOLIPOP) provide an exciting opportunity for the identification of new risk factors underlying CHD in this high risk population.

Seventy-five genetic loci influencing the human red blood cell

Anaemia is a chief determinant of global ill health, contributing to cognitive impairment, growth retardation and impaired physical capacity. To understand further the genetic factors influencing red blood cells, we carried out a genome-wide association study of haemoglobin concentration and related parameters in up to 135,367 individuals. Here we identify 75 independent genetic loci associated with one or more red blood cell phenotypes at P < 10(-8), which together explain 4-9% of the phenotypic variance per trait. Using expression quantitative trait loci and bioinformatic strategies, we identify 121 candidate genes enriched in functions relevant to red blood cell biology. The candidate genes are expressed preferentially in red blood cell precursors, and 43 have haematopoietic phenotypes in Mus musculus or Drosophila melanogaster. Through open-chromatin and coding-variant analyses we identify potential causal genetic variants at 41 loci. Our findings provide extensive new insights into genetic mechanisms and biological pathways controlling red blood cell formation and function.

Genome-wide association study identifies loci influencing concentrations of liver enzymes in plasma

Concentrations of liver enzymes in plasma are widely used as indicators of liver disease. We carried out a genome-wide association study in 61,089 individuals, identifying 42 loci associated with concentrations of liver enzymes in plasma, of which 32 are new associations (P = 10(-8) to P = 10(-190)). We used functional genomic approaches including metabonomic profiling and gene expression analyses to identify probable candidate genes at these regions. We identified 69 candidate genes, including genes involved in biliary transport (ATP8B1 and ABCB11), glucose, carbohydrate and lipid metabolism (FADS1, FADS2, GCKR, JMJD1C, HNF1A, MLXIPL, PNPLA3, PPP1R3B, SLC2A2 and TRIB1), glycoprotein biosynthesis and cell surface glycobiology (ABO, ASGR1, FUT2, GPLD1 and ST3GAL4), inflammation and immunity (CD276, CDH6, GCKR, HNF1A, HPR, ITGA1, RORA and STAT4) and glutathione metabolism (GSTT1, GSTT2 and GGT), as well as several genes of uncertain or unknown function (including ABHD12, EFHD1, EFNA1, EPHA2, MICAL3 and ZNF827). Our results provide new insight into genetic mechanisms and pathways influencing markers of liver function.

Common genetic variation near melatonin receptor MTNR1B contributes to raised plasma glucose and increased risk of type 2 diabetes among Indian Asians and European Caucasians

OBJECTIVE

Fasting plasma glucose and risk of type 2 diabetes are higher among Indian Asians than among European and North American Caucasians. Few studies have investigated genetic factors influencing glucose metabolism among Indian Asians.

RESEARCH DESIGN AND METHODS

We carried out genome-wide association studies for fasting glucose in 5,089 nondiabetic Indian Asians genotyped with the Illumina Hap610 BeadChip and 2,385 Indian Asians (698 with type 2 diabetes) genotyped with the Illumina 300 BeadChip. Results were compared with findings in 4,462 European Caucasians.

RESULTS

We identified three single nucleotide polymorphisms (SNPs) associated with glucose among Indian Asians at P < 5 x 10(-8), all near melatonin receptor MTNR1B. The most closely associated was rs2166706 (combined P = 2.1 x 10(-9)), which is in moderate linkage disequilibrium with rs1387153 (r(2) = 0.60) and rs10830963 (r(2) = 0.45), both previously associated with glucose in European Caucasians. Risk allele frequency and effect sizes for rs2166706 were similar among Indian Asians and European Caucasians: frequency 46.2 versus 45.0%, respectively (P = 0.44); effect 0.05 (95% CI 0.01-0.08) versus 0.05 (0.03-0.07 mmol/l), respectively, higher glucose per allele copy (P = 0.84). SNP rs2166706 was associated with type 2 diabetes in Indian Asians (odds ratio 1.21 [95% CI 1.06-1.38] per copy of risk allele; P = 0.006). SNPs at the GCK, GCKR, and G6PC2 loci were also associated with glucose among Indian Asians. Risk allele frequencies of rs1260326 (GCKR) and rs560887 (G6PC2) were higher among Indian Asians compared with European Caucasians.

CONCLUSIONS

Common genetic variation near MTNR1B influences blood glucose and risk of type 2 diabetes in Indian Asians. Genetic variation at the MTNR1B, GCK, GCKR, and G6PC2 loci may contribute to abnormal glucose metabolism and related metabolic disturbances among Indian Asians.