High-Resolution Free-Breathing Automated Quantitative Myocardial Perfusion by Cardiovascular Magnetic Resonance for the Detection of Functionally Significant Coronary Artery Disease

AIMS

Current assessment of myocardial ischaemia from stress perfusion cardiovascular magnetic resonance (SP-CMR) largely relies on visual interpretation. This study investigated the use of high-resolution free-breathing SP-CMR with automated quantitative mapping in the diagnosis of coronary artery disease (CAD). Diagnostic performance was evaluated against invasive coronary angiography (ICA) with fractional flow reserve (FFR) measurement.

METHODS & RESULTS

Seven-hundred and three patients were recruited for SP-CMR using the research sequence at 3 Tesla. Of those receiving ICA within 6 months, 80 patients either had FFR measurement, or identification of a chronic total occlusion (CTO) with inducible perfusion defects seen on SP-CMR. Myocardial blood flow (MBF) maps were automatically generated in-line on the scanner following image acquisition at hyperaemic stress and rest, allowing myocardial perfusion reserve (MPR) calculation. 75 coronary vessels assessed by FFR, and 28 vessels with CTO were evaluated at both segmental and coronary territory level. Coronary territory stress MBF and MPR were reduced in FFR-positive (≤ 0.80) regions (median stress MBF: 1.74 [0.90-2.17] ml/min/g; MPR: 1.67 [1.10-1.89]) compared with FFR-negative regions (stress MBF: 2.50 [2.15-2.95] ml/min/g; MPR 2.35 [2.06-2.54] p < 0.001 for both). Stress MBF ≤ 1.94 ml/min/g and MPR ≤ 1.97 accurately detected FFR-positive CAD on a per-vessel basis (area under the curve: 0.85 and 0.96 respectively; p < 0.001 for both).

CONCLUSIONS

A novel scanner-integrated high-resolution free-breathing SP-CMR sequence with automated in-line perfusion mapping is presented which accurately detects functionally significant CAD.

Coronary wave energy to predict functional recovery in patients with ischemic left ventricular dysfunction

Background

Invasive coronary angiography and non-invasive viability testing are the cornerstones of diagnosing and managing ischemic left ventricular dysfunction. At present there is no single test which serves both needs but, if developed, could revolutionise investigation of this condition. Coronary wave intensity analysis (cWIA) interrogates both contractility and microvascular physiology of the subtended myocardium [1,2] and therefore has the potential to fulfil this goal.

Objectives

We hypothesized that cWIA measured during coronary angiography would predict functional recovery with a similar accuracy to late gadolinium enhanced cardiac magnetic resonance imaging (LGE-CMR).

Methods

Patients with a left ventricular ejection fraction ≤40% and extensive coronary disease were enrolled. cWIA, fractional flow reserve and microvascular resistance were assessed with a simultaneous coronary Doppler and pressure-sensing guidewire during cardiac catheterization at rest, during hyperaemia and during low-dose dobutamine stress. Viability was assessed using LGE-CMR. Regional left ventricular function was assessed at baseline and 6-month follow up after optimization of medical therapy +/− revascularization, using transthoracic echocardiography. The primary outcome was regional functional recovery.

Results

Forty participants underwent baseline physiology, LGE-CMR and thirty had echocardiography at baseline and 6 months; 21/42 territories demonstrated functional recovery. Resting backward compression wave energy was significantly greater in recovering than non-recovering territories (−5240±3772 vs. −1873±1605 W m–2 s–1, p=0.099, Figure 1), and had comparable diagnostic accuracy to CMR (area under the curve 0.812 vs. 0.757, p=0.649, Figure 2); a threshold of −2500 W mm–2 s–1 had 86% sensitivity and 76% specificity at predicting recovery. Backward expansion wave energy did not predict recovery. FFR was numerically higher in recovering territories (0.81±0.17 vs. 0.71±0.16, p=0.058), whilst hyperaemic microvascular resistance did not differentiate recovering from non-recovering territories (1.97±0.73 vs. 2.29±1.00, p=0.287). The likelihood of functional recovery was similar in revascularised and non-revascularised territories (15/29 vs. 6/13 respectively, p=0.739). Low-dose dobutamine stress increased the energy of all waves, but did not improve the accuracy of cWIA in predicting recovery. In a regression model, resting backward compression wave energy and optimization of medical therapy predicted functional recovery; fractional flow reserve and hyperemic microvascular resistance did not.

Conclusions

Backward compression wave energy has similar accuracy to LGE-CMR in the prediction of functional recovery. cWIA has the potential to revolutionise the management of ischaemic left ventricular dysfunction, in a manner analogous to the effect of fractional flow reserve on the management of stable angina.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The British Heart Foundation Clinical Research Training Fellowship

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Atrial tissue characterisation using electroanatomic voltage mapping and cardiac magnetic resonance imaging

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background

Atrial voltage mapping and atrial cardiac magnetic resonance imaging are two contemporary methods for quantification of atrial fibrosis. However, the absence of a gold standard for measuring atrial fibrosis has precluded their direct comparison. Nevertheless, understanding the relative performance of voltage mapping and atrial late gadolinium enhancement for identification of atrial cardiomyopathy remains critical to correctly targeting clinical application of these techniques.

Purpose

To assess the relative performance of electroanatomic voltage mapping and atrial late gadolinium enhancement imaging using three surrogate markers chosen to distinguish pre-procedural utility (progression to recurrent atrial fibrillation following ablation) from potential utility for providing atrial fibrillation mechanistic insights (paroxysmal vs. persistent status of atrial fibrillation and relationship with co-morbidities associated with atrial fibrillation).

Methods

123 patients underwent atrial late gadolinium enhancement imaging and electroanatomic voltage mapping prior to atrial fibrillation ablation. Atrial late gadolinium enhancement imaging was assessed with CEMRG software and electroanatomic voltage mapping processed with OpenEP software using previously published thresholds. Low voltage tissue was defined at (1) &lt;0.5mV, (2) &lt;1.17mV, and (3) &lt;1.3mV. Atrial fibrosis using late gadolinium enhancement was defined using four thresholds (1) signal intensity &gt;3.3 standard deviations above the blood pool mean; (2) image intensity ratio (IIR) 1.2x blood pool mean; (3) IIR 1.32x blood pool mean; and (4) IIR 0.97x blood pool mean.

Results

Patients with persistent atrial fibrillation and those with CHA2DS2VaSc &gt;2 had increased low voltage area for each of the thresholds tested, but there was no increase in atrial late gadolinium enhancement area at any of the imaging thresholds tested.

Increased atrial fibrosis using IIR&gt;0.97 was independently associated with recurrence of atrial fibrillation (OR 1.05 (CI 1.01-1.09), p=0.009) in both univariate and multivariate analysis. Low voltage area &lt;1.13mV and low voltage area &lt;1.17mV were associated with increased risk of recurrence (OR 1.02 (CI 1.01-1.04), p=0.01, and OR 1.03 (CI 1.01-1.04), p=0.009) in univariate analysis but neither voltage threshold remained statistically significant in multivariate analysis controlling for clinical variables.

Conclusion

Increased fibrosis burden measured with atrial magnetic resonance imaging, but not with low voltage area, is independently associated with recurrence of atrial fibrillation following catheter ablation. However, increased low voltage area measured with electroanatomic mapping is associated with persistent atrial fibrillation status and CHADS2VaSc score. These findings support the use of magnetic resonance imaging for pre-procedure assessment and the use of electroanatomic mapping for intraprocedural mechanism-based assessment of atrial cardiomyopathy.

Stress myocardial blood flow reduced after severe COVID-19, not related to symptoms

Introduction

Persistent cardiopulmonary symptoms after COVID-19 are reported in a large number of patients and the underlying pathology is still poorly understood. (1) Histopathologic studies revealed myocardial macrophage infiltrates in deceased patients, likely an unspecific finding of severe illness, and increased prevalence of micro- and macrovascular thrombi. (2) We examined whether microvascular perfusion, measured by quantitative cardiac magnetic resonance under vasodilator stress, was altered post COVID-19.

Methods

Our population consisted of 12 patients from the Pa-COVID-19-Study of the Charité Berlin, which received a cardiac MRI as part of a systematic follow up post discharge, 10 patients that presented at the German Heart Center Berlin with persistent cardiac symptoms post COVID-19 and 12 patients from the Kings College London referred for stress MRI and previous COVID-19.

The scan protocol included standard functional, edema and scar imaging and quantitative stress and rest perfusion to assess both macro- and microvascular coronary artery disease. The pharmacological stress agent was regadenosone in 20 and adenosine in 13 of the patients. To control for the higher heart rate increase under regadenosone compared to adenosine, we calculated the myocardial blood flow per heartbeat (MBF_HRi) under stress.

Results

The median time between first positive PCR for COVID-19 and the CMR exam was 2 months (Range 0 to 12). None of the 33 patients exhibited signs of myocardial edema. One patient with a previous history of myocarditis had focal fibrosis. Three patients with known coronary artery disease showed ischemic Late Enhancement. Five patients had a small pericardial effusion; one of these four patients showed slight focal pericardial edema and LGE, consistent with mild focal pericarditis. Five Patients had a stress-induced focal perfusion deficit.

Mean Stress MBF_HRi was 32.5±6.5 μl/beat/g. Stress MBF_HRi was negatively correlated with COVID-19 severity (rho=−0.361, P=0.039) and age (r=−0.452, P=0.009). The correlation with COVID-19 severity remained significant after controlling for age (rho=−0.390, P=0.027). There was no apparent difference in stress MBF_HRi between patients with and without persistent chest pain (34.5 vs. 31.5 μl/beat/g, P=0.229)

Conclusion

While vasodilator-stress myocardial blood flow after COVID-19 was negatively correlated to COVID-19 severity, it was not correlated to the presence of chest pain. The etiology of persistent cardiac symptoms after COVID-19 remains unclear.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Philips Figure 1. A) Quantitative regadenosone stress myocardial blood flow (MBF) map, medial short axis slice, in a patient with persistent cardiac symptoms after COVID-19. B) Boxplot of stress MBF per heart beat by COVID-19 severity, showing decreasing MBF with increasing COVID-19 severity.

In-depth phenotyping by cardiovascular magnetic resonance uncovering differences between ethnic groups in hypertensive heart disease

Background

Black African/African-Caribbean individuals with hypertension (BH) are at greater risk of heart failure than those of white European ethnicity (WH). The mechanisms underlying this dissimilarity remain poorly understood.

Purpose

To investigate the influence of ethnicity on left ventricular (LV) remodelling using multi-parametric cardiovascular magnetic resonance (CMR).

Methods

BH (n=44), WH (n=38) and healthy-volunteers (HV; n=25, 5 of black ethnicity) underwent comprehensive CMR. The exam included: i) Arterial Stiffness/Afterload pulse-wave-velocity (PWV), aortic elastance (Ea) and systemic vascular resistance (SVR) by phase-contrast velocity-encoding imaging; ii) Ventricular remodelling/Function LV and right ventricular (RV) volumes, mass, ejection fraction (EF), LV peak-filling rate by short-axis cine images; myocardial strains were measured by feature tracking; iii) Left atrial (LA) remodelling/Function volumes and functions by long-axis cine images; iv) Tissue characterisation: extracellular volume by pre/post-contrast T1-mapping and late gadolinium enhancement (LGE) for interstitial and replacement myocardial fibrosis, respectively. Multivariate linear regression models were developed to investigate how LV remodelling associates with ethnicity, arterial afterload, including elastance (Ea) and stiffness [PW], and SVR. Models were adjusted for age, gender, body-mass-index, LV volumes or function and LA volumes.

Results

Subject characteristics are summarised in the Table. PWV and Ea and SVR were greater in hypertensives, particularly in BH, than HV; this was paralleled by higher LV mass, interventricular septum thickness (IVS), LA volumes but lower LV-EF. These findings were confirmed after adjusting for age.

On the Model-1, IVS was associated with Ea (β=0.335, P=0.008) and black ethnicity (β=0.226, P=0.019) but not with SVR or PWV. For each increment of Ea there was a similar increase of IVS in BH and WH (P=0.602 for interaction), however BH had greater IVS than WH at each Ea value (Figure, fully-adjusted Model-1). On Model-2, LV end-diastolic volume was associated with Ea (β=−0.268, P=0.001), SVR (β=−0.319, P=0.019) but not with PWV or ethnicity. However, the inverse relation between LV size and Ea was significantly attenuated in BH (P=0.039 for interaction), (Figure, fully-adjusted Model-2). On model-3, LV-EF was associated with Ea (β=0.223, P=0.009) but not with ethnicity, PWV or SVR. LV-EF reduction for each Ea increment was similar for BH and WH (P=0.597 for interaction).

Conclusion

BH and WH show a distinctive LV remodelling phenotype. BH had a greater susceptibility to hypertrophy and an attenuated reduction of chamber size in response to arterial afterload. Further research to disentangle the genetic and environmental factors underlying these ethnic group-specific differences is utterly required.

Funding Acknowledgement

Type of funding sources: None. Figure 1Table 1

Acute regional changes in myocardial strain may predict ventricular remodelling after myocardial infarction in a large animal model

To identify predictors of left ventricular remodelling (LVR) post-myocardial infarction (MI) and related molecular signatures, a porcine model of closed-chest balloon MI was used along with serial cardiac magnetic resonance imaging (CMRI) up to 5-6 weeks post-MI. Changes in myocardial strain and strain rates were derived from CMRI data. Tissue proteomics was compared between infarcted and non-infarcted territories. Peak values of left ventricular (LV) apical circumferential strain (ACS) changed over time together with peak global circumferential strain (GCS) while peak GLS epicardial strains or strain rates did not change over time. Early LVR post-MI enhanced abundance of 39 proteins in infarcted LV territories, 21 of which correlated with LV equatorial circumferential strain rate. The strongest associations were observed for D-3-phosphoglycerate dehydrogenase (D-3PGDH), cysteine and glycine-rich protein-2, and secreted frizzled-related protein 1 (sFRP1). This study shows that early changes in regional peak ACS persist at 5-6 weeks post-MI, when early LVR is observed along with increased tissue levels of D-3PGDH and sFRP1. More studies are needed to ascertain if the observed increase in tissue levels of D-3PGDH and sFRP1 might be casually involved in the pathogenesis of adverse LV remodelling.

Unravelling racial differences in hypertensive heart disease by multiparametric cardiovascular magnetic resonance: a phenotype-wide association study

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Dr Georgiopoulos was supported by the Onassis Foundation under the special grant & support program for scholars" association members

Introduction – Black Afro-Caribbean hypertensives (BAHs) are exposed to a higher risk of heart failure (HF) than white hypertensives (WHs). Arterial afterload is higher in BAHs due to increased arterial stiffness and vascular volume; BAHs develop more often left ventricular (LV) hypertrophy, dilatation and systolic dysfunction than WHs. However, it is unclear whether other racial differences concur to the more pronounced LV remodelling in BAHs.

Methods – This cross-sectional study included hypertensive patients undergoing cardiovascular magnetic resonance for their clinical work-up (1.5T Aera Siemens-Healthcare). Clinical history and haemodynamic parameters were collected in all participants; a subset of patients had complete bio-humoral assay of the renin-angiotensin-aldosterone system (RAAs). Arm cuff pressure was measured during CMR. The CMR protocol included: i) Arterial afterload / LV arterial-coupling - pulse-wave-velocity (PWV), aortic (Ea) and LV elastance (Ees) by aorta anatomic and phase-contrast velocity-encoding imaging; ii) ventricular remodelling and function - LV and right ventricular (RV) volumes, mass, EF, LV peak-filling rate by short-axis cine images; global circumferential and longitudinal strains by cine feature tracking; iii) left atrial (LA) remodelling volumes and reservoir, conduit and booster functions by long-axis cine images; iv) tissue characterisation: T2 and pre/post-contrast T1 relaxation times, extracellular volume (ECV) by single mid-ventricular short-axis T1/T2-mapping.

Results – 34 BAHs and 35 WHs (52 ± 12 vs 45 ± 14 years, P &lt; 0.05; 61% vs 65% males P = NS) were included in the study. Baseline features are summarised in the Table. LV systolic dysfunction was more prevalent in BAH than WHs (P = 0.038). Of note, BAHs tended to have greater LV volumes and significantly higher LV mass and septal thickness than WHs. In BAHs, but not in WHs, PWV was associated with increased septal thickness after correction for blood pressure and age (β-value: 0.447, P = 0.02). Normalised RV mass was greater in BHA than WHs; RV mass suits for the identification of racial or circulating factors predisposing to hypertrophy being largely unaffected by systemic afterload. In our study LV diastolic function and LA volumes were similar between BAHs and WHs, and none of the subjects had conditions associated with pre-capillary pulmonary hypertension. Hence, higher RV-mass in BAHs pinpoints a racial susceptibility to myocardial hypertrophy. Finally, in a subset of patients with RAAs assays (n = 43), the aldosterone/renin ratio was higher in BAHs than WHs (67.04 [IQR: 19.37-209.73] vs 13.77 [IQR: 7.47-40.43], P = 0.01).

Conclusion – BAHs have heightened LV remodelling than WHs because of racial predisposition to develop hypertrophy which also encompasses derangements in RAAs. Altogether, these findings may account for the greater risk for HF in BAHs than WHs.

Myocardial perfusion quantification by CMR for detection of obstructive coronary artery disease in patients with previous coronary artery bypass surgery

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): British Heart Foundation

Background

Coronary artery bypass grafting (CABG) is an established treatment for patients with advanced coronary artery disease (CAD). A subsequent recurrence of symptoms can cause the need for re-assessment of the coronary circulation. The accuracy of visually assessed stress perfusion cardiovascular magnetic resonance (CMR) for the detection of obstructive CAD is reduced in patients with prior CABG. In patients with complex multi-vessel CAD, myocardial perfusion quantification by CMR is superior to visual assessment (VA) for detection of obstructive disease however patients with CABG have been absent from previous studies.

Purpose

This study sought to assess the performance of myocardial perfusion quantification by CMR against invasive coronary angiography (ICA) for detecting obstructive CAD in patients with previous CABG.

Methods

Twenty-nine patients with a history of previous CABG and subsequent clinically indicated perfusion CMR study and invasive coronary angiography were recruited. Patients underwent a dual bolus stress perfusion CMR with late gadolinium enhancement (LGE) imaging at 3 Tesla. Stress myocardial blood flow (MBF) was estimated at the coronary territory level according to the AHA 16 segment model using Fermi function-constrained deconvolution. Segments with transmural LGE were excluded from MBF analysis. Stress perfusion images were analysed visually alongside LGE images and matched perfusion-LGE defects were considered negative. On ICA, coronary territories with lumen stenosis &gt;70% without an unobstructed bypass graft (&lt;70% stenosis) were considered positive.

Results

86/87 coronary territories were suitable for analysis. Sixty-five territories had at least one bypass graft including 32 territories with arterial grafts. 28/86 territories (33%) had obstructive disease on angiography. Territories with obstructive CAD had significantly lower stress MBF than unobstructed territories (1.21 [IQR: 0.96–1.45] vs 1.58 [1.40–1.84] ml/g/min, p &lt; 0.001, Figure 1). Stress MBF had good accuracy to detect coronary territories with obstructive CAD (sensitivity 71%, specificity 84%, area under the curve (AUC) 0.83, p &lt; 0.001, Figure 2A). For visual assessment, sensitivity was 79%, specificity 78% and diagnostic accuracy 78%. When analysis was confined to only territories with bypass grafts, stress MBF had 78% sensitivity, 81% specificity and AUC of 0.85, p &lt; 0.001 (Figure 2B).. In this subgroup, VA had a sensitivity of 78%, specificity of 76% and a 77% diagnostic accuracy.

Conclusions

In patients with previous surgical revascularisation, quantification of stress myocardial blood flow by CMR offers good diagnostic accuracy for the detection and localisation of anatomically significant stenoses. Accuracy is reduced compared with published data in patients without coronary grafts but remains comparable to expert visual assessment.

The strain-7 study: multimodal, multivendor, multifield strength, scan:rescan comparison of global longitudinal and circumferential strain in healthy volunteers

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): National Insitute for Health Research

Background

There is clinical and prognostic evidence for global longitudinal strain (GLS) and circumferential strain (GCS). A range of techniques exist: 2-dimensional echocardiography (2Decho), 3-dimensional echocardiography (3Decho) and Cardiovascular Magnetic Resonance (CMR).

Purpose

To investigate inter-study repeatability and inter-method comparison of GLS and GCS techniques.

Methods

Volunteers underwent same day scan

rescan 2Decho, 3Decho, 1.5T Siemens CMR (Cine imaging and Displacement encoding with stimulated echoes [DENSE]), 3T Siemens CMR (Cine Imaging and DENSE) and 3T Philips CMR (Tagging and Fast strain-encoding [fSENC]) imaging. Strain was quantified for 2Decho (EchoPAC), 3Decho (TomTec), Feature tracking (FT) for cine imaging (CircleCVI), CIM (University of Auckland) for DENSE and Tag, and Myostrain (Myocardial solutions) for fSENC.

Results

20(6F) volunteers, mean age 33 ± 7 years, mean LVEF 62 ± 4%. All GLS and GCS methods had excellent inter-study agreement (ICC &gt; 0.75) with coefficient of variation (CoV) between 4-8% (Table 1). Median and IQR are presented in Figure 1.

Friedman’s test revealed statistically significant inter-method differences for GLS (χ2 = 66.4,p &lt; 0.0001) and GCS (χ2 = 50.9,p &lt; 0.0001). Post hoc analysis using Dunn’s test with Bonferroni correction demonstrated significant differences:

-GLS: 2Decho vs DENSE 1.5T (p = 0.001) and Myostrain 3T (p = 0.0116); 3Decho vs FT 3T (p = 0.049) and DENSE 1.5T (p &lt; 0.0001); FT 1.5T vs DENSE 1.5T (p = 0.001) and Myostrain 3T (p = 0.01); FT 3T vs Myostrain 3T (p &lt; 0.0001); DENSE 1.5T vs Tag 3T (p = 0.0008) and Myostrain 3T (p &lt; 0.0001); Tag 3T vs Myostrain (p = 0.02).

-GCS: 3Decho vs DENSE 1.5T (P = 0.0005), FT 1.5T (p &lt; 0.001), FT 3T (P &lt; 0.001) and Myostrain (p = 0.003); FT 1.5T vs Tag 3T (p = 0.001), FT 3T vs Myostrain 3T (p = 0.04).

Conclusion

There is excellent interstudy agreement for GLS and GCS methods. However, there are important inter-method differences in absolute values, that need to be considered for clinical application as a surveillance method and longitudinal studies.

Table 1 Acquisiton Post processing GLS CoV(%) GLS ICC GCS CoV(%) GCS ICC 2DEcho EchoPAC 4.88 0.80 - - 3DEcho TomTec 4.77 0.86 3.97 0.85 Siemens 1.5T cine FT CircleCVI 8.30 0.79 6.00 0.85 Siemens 3T cine FT CircleCVI 6.21 0.89 4.76 0.94 Philips 3T Tag CIM 6.15 0.89 5.86 0.88 Siemens 1.5T DENSE CIM 4.36 0.90 4.65 0.89 Philips 3T fSENC Myostrain 8.45 0.81 4.06 0.90 Interstudy agreement for the different GLS and GCS methods. Abstract Figure 1

Left ventricular ejection fraction as an imaging biomarker to guide cardiac resynchronisation therapy in heart failure patients: a multimodal comparison of 2D and 3D echocardiography and CMR

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): The authors acknowledge financial support from the Department of Health through the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy’s & St Thomas’ NHS Foundation Trust in partnership with King’s College London and King’s College Hospital NHS Foundation Trust and by the NIHR MedTech Co-operative for Cardiovascular Disease at Guy’s and St Thomas’ NHS Foundation Trust. This work was supported by the Wellcome/EPSRC Centre for Medical Engineering [WT 203148/Z/16/Z]. MSN was funded by a clinical lectureship awarded by the NIHR. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the DoH, EPSRC, MRC or the Wellcome Trust.

Introduction – Imaging derived left ventricular ejection fraction (LVEF) has an important role to guide initiation of medical therapy and device insertion in patients with heart failure and reduced ejection fraction (HFrEF). Previous studies have reported the correlation and agreement of LVEF in various patient populations, but sparse evidence exists on patients with heart failure referred for Cardiac Resynchronisation Therapy (CRT) using 2D and 3D echocardiography (2DE & 3DE) and cardiovascular magnetic resonance (CMR).

Objectives – To determine the correlation and agreement of LVEF as determined by 2DE, 3DE and CMR in a cohort of HF patients referred for assessment of CRT.

Methods – Patients with suspected HFrEF referred for assessment for CRT therapy were included in this single centre study. Patients underwent 2DE, 3DE and CMR to derive LVEF, LVESV and LVEDV. Correlation was determined with Pearson’s correlation, agreement with Bland-Altman analysis and Cohen’s kappa analysis for agreement using a dichotomous cut off of LVEF ≤35% as a threshold for CRT insertion (Ponikowski, 2016).

Results - 55 patients (mean age 71 ± 9.2, 76% male) were included. The mean LVEF for 2DE, 3DE, CMR and were 32.4 ± 8.6, 32.1 ± 9.6 and 30.3 ± 9.5 respectively. CMR had a significantly lower LVEF compared to 2DE (p = 0.03).

There was good correlation between 3DE & CMR and 2DE & CMR, and excellent correlation between 3DE and 2DE for LVEF (Table 1). There was for trend for CMR to underestimate LVEF compared to 2DE and 3DE, with small biases although wide limits of agreement (Figure 1). There was excellent correlation of LVEDV and LVESV across all 3 techniques. CMR underestimated volumes compared to 2DE and 3DE with large biases and wide LOA.

The kappa coefficient agreement at threshold level for CRT insertion (LVEF ≤35%) was fair for 3DE and CMR (0.379, p = 0.004) and 2DE and CMR (0.462, p = 0.001), and moderate for 3DE and 2DE (0.575, p ≤ 0.001).

Conclusion – Whilst LVEF is not the only indicator to guide CRT insertion, it remains an important imaging parameter for clinical decision making. We observed large biases in left ventricular volumes between 2D, 3D and CMR. However, whilst the overall bias in LVEF is small, the wide limits of agreement (LOA) observed may represent an area of clinical uncertainty, which may impact on the dichotomous imaging threshold for CRT insertion.

Comparison of indices between modalities LVEF Correlation (r) LVEF Bias & LOA (%±SD) EDV Correlation (r) EDV Bias & LOA (mL ± SD) ESV Correlation (r) ESV Bias & LOA (mL ± SD) 3DE vs CMR 0.676 (p &lt; 0.001) +1.75 ± 15.4 0.896 (p &lt; 0.001) -82.16 ± 42.8 0.937 (p &lt; 0.001) -61.3 ± 34.9 3DE vs 2DE 0.872 (p &lt; 0.001) +0.48 ± 4.5 0.909 (p &lt; 0.001) -10.31 ± 28.3 0.936 (p &lt; 0.001) -8.42 ± 20.5 2DE vs CMR 0.675 (p &lt; 0.001) +2.35 ± 14.6 0.876 (p &lt; 0.001) -67.35 ± 36.3 0.898 (p &lt; 0.001) -51.42 ± 30.1 Abstract Figure. Bland-Altman Plot LVEF by 3DE & CMR

Novel dark-blood versus conventional bright-blood late gadolinium enhancement CMR: A pilot study comparing impact on myocardial ischaemic burden

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background

In patients with coronary artery disease (CAD), increasing myocardial ischaemic burden (MIB) is a strong predictor of adverse events. When measured by cardiovascular magnetic resonance (CMR), a MIB ≥12.5% is considered significant and often used as a threshold to guide revascularisation. Ischaemic scar can cause stress perfusion defects which do not represent ischaemia and should be excluded from the MIB calculation. Conventional bright-blood late gadolinium enhancement (LGE) is able to identify ischaemic scar but can suffer from poor scar-to-blood contrast, making accurate assessment of scar volume difficult. Dark-blood LGE methods increase scar-to-blood contrast and improve scar conspicuity which may impact the calculated scar burden and consequently the estimation of MIB when read in conjunction with perfusion images.

Purpose

To evaluate the impact of dark-blood LGE versus conventional bright-blood LGE on the estimation of MIB in patients with CAD.

Methods

37 patients with suspected or known CAD who had evidence of CMR stress perfusion defects and ischaemic scar on LGE imaging were recruited. Patients underwent adenosine stress perfusion imaging followed by dark-blood LGE then conventional bright-blood LGE imaging at 3T. For dark-blood LGE, phase sensitive inversion recovery imaging with a shorter inversion time to null the LV blood-pool was used without any additional magnetization preparation. For each patient, three short-axis LGE slices were selected to match the three perfusion slice locations. Images were anonymised and analysed in random order. Ischaemic scar burden (ISB) was quantified for both LGE methods using a threshold &gt;5 standard deviations above remote myocardium. Perfusion defect burden (PDB) was quantified by manual contouring of perfusion defects. MIB was calculated by subtracting the ISB from the PDB.

Results

MIB calculated using dark-blood LGE was 19% less compared to bright-blood LGE (15.7 ± 15.2% vs 19.4 ± 15.2%, p &lt; 0.001). There was a strong positive correlation between the two LGE methods (rs = 0.960, p &lt; 0.001, Figure 1A). Bland-Altman analysis revealed a significant fixed bias (mean bias = -3.6%, bias 95% CI: -2.6 to -4.7%, 95% limits of agreement: -9.8 to 2.5%) with no proportional bias (Figure 1B). MIB was calculated ≥12.5% and &lt;12.5% by both LGE methods in 19 (51%) and 12 (32%) patients respectively. In 6 patients (16%), MIB was ≥12.5% using bright-blood LGE and &lt;12.5% using dark-blood LGE (Figure 1A – orange data points). Overall, when used to classify MIB as &lt;12.5% or ≥12.5%, there was only substantial agreement between the two LGE methods (κ=0.67, 95% CI: 0.45 to 0.90).

Conclusions

The use of dark-blood LGE in conjunction with perfusion imaging results in a lower estimate of MIB compared to conventional bright-blood LGE. This can cause disagreement around the threshold of clinically significant ischaemia which could impact clinical management in patients being considered for coronary revascularisation.

Abstract Figure. Linear regression with corresponding B&A

Role of myocardial T1 mapping in arrhythmogenic right ventricular cardiomyopathy

Background

T1 mapping by cardiovascular magnetic resonance (CMR) is an accurate tool to assess myocardial extracellular space with wider clinical applications in the aetiological characterization of cardiomyopathies. The aims of the study were to explore a possible role of myocardial T1 mapping in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and in first-degree relatives at risk and to investigate the possible relationship between left ventricular (LV) involvement at CMR and ECG features.

Methods

Thirty patients with ARVC (47% males, mean age 42±22 years) and 59 first-degree relatives who did not fulfil ARVC diagnostic Task Force criteria, underwent full diagnostic work-up including CMR with native and post-contrast T1 mapping.

Results

The CMR was abnormal in 26 (86%) patients with ARVC. The RV was affected in isolation in 13 (43%) patients. Prior to T1 mapping assessment, 2 (7%) patients exhibited isolated LV involvement and 11 (36%) patients showed features of biventricular disease. Left ventricular involvement was manifested as detectable LV late gadolinium enhancement (LGE) in 12 out of 13 cases. According to pre-specified septal T1 mapping thresholds, 11 (37%) patients showed abnormally high native T1 values. Myocardial T1 mapping was higher than normal in 5 (17%) patients who would have been classified as exhibiting a normal LV by conventional imaging. The proportion of patients with abnormal T1 values was similar in patients with or without LGE. Myocardial T1 mapping was higher than normal in 22 (37%) of the 59 first-degree relatives.

Conclusions

Native and/or post contrast myocardial T1 values are raised in almost half of patients with ARVC and in a similar proportion of unaffected first-degree relatives. T1 mapping offers the potential for early detection of LV involvement in patients with ARVC and in first-degree relatives at risk.

Funding Acknowledgement

Type of funding source: None

High-resolution CINE MRI allows estimation of 3D regional atrial strains

Introduction

It is increasingly evident that atrial function is an important marker of cardiovascular health. Impaired global left atrial strain has been associated with risk of thromboembolic events, atrial fibrillation and heart failure. When performed at high spatial resolution, CINE MRI allows the estimation of regional atrial strains, which may facilitate earlier identification of atrial disease and improved (non-contrast) characterisation of atrial fibrosis. Nevertheless, to date, high resolution regional atrial strains has not been assessed using CINE MRI.

Purpose

We introduce a novel rapid 2.2-mm isotropic atrial CINE MRI protocol used to image healthy subjects and patients with cardiovascular disease (CVD). We additionally present a dedicated image analysis pipeline to estimate regional 3D atrial strains from these images.

Methods

We imaged 10 healthy subjects (5 female, 24–36 years old) and 6 patients referred for cardiac MRI due to known or suspected CVD (2 female, 25–80 years old). All subjects were scanned in a 1.5T Philips Ingenia MRI scanner in a single breath-hold (&lt;25 s), using a short-axis 3D bSSFP protocol (flip angle: 60°, TE/TR: 1.6/3.3 ms) with retrospective cardiac gating, SENSE = 2.3 (along both phase encode directions), typical FOV: 400 x 270 x 70 mm3, isotropic acquisition resolution of 2.2 mm3. Images were reconstructed to 20 cardiac phases with 55% view sharing.

The left atrium (LA) was manually segmented in atrial diastole. We tracked the position of evenly spaced points along the LA contour across all phases of the cardiac cycle using the Medical Image Tracking Toolbox. This was used to create a series of deforming smooth triangular meshes, from which Lagrange strain tensors were estimated.

Results

Figs a-c show 3 orthogonal views of the proposed high-resolution atrial CINE MRI scans for a representative CVD patient, with the LA segmentation overlaid in red. Representative LA principal strain directions (as arrows) with the colour indicating the amount of strain observed along this direction are shown in Fig d for active atrial contraction (posterior view). The calculated strain directions varied smoothly in space and time, as expected, and were largest in amplitude in the regions closest to the mitral valve.

Overall, principal strains were larger in healthy subjects (AC strains: 0.12±0.06) than in the CVD cohort (AC strains: 0.04±0.01). This difference was statistically significant during AC (p-value: 0.02), but not during atrial diastole (p-value: 0.06).

Conclusions

We present a novel high-resolution CINE-MRI protocol for estimating regional atrial strains in 3D, with pilot data from 10 healthy subjects and 6 cardiovascular patients. Future studies will compare regions of abnormal atrial strain with fibrosis identified in late gadolinium enhanced MRI to assess whether regional strains can provide a better characterisation of atrial tissue and improved stratification of patients at risk.

Figure 1

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation, EPSRC/Wellcome Trust Centre for Medical Engineering

A cost effectiveness study into the detection of functionally significant coronary artery disease in patients with chronic coronary syndrome: a decision-analytic modelling approach

Background

ESC guidelines recommend functional or anatomical imaging for stable coronary artery disease (CAD) diagnosis. We investigated cost-effective diagnostic strategies for CAD detection with invasive coronary angiography (ICA) and fractional flow reserve (FFR) as reference standard [1,2], using NHS reference costs.

Methods

Deterministic and probabilistic decision-analytic models for diagnostic strategies in low (25%), intermediate (50%) and high (75%) risk CAD were devised. Strategies: standalone or combined testing with computed tomographic coronary angiography (CTCA), stress echocardiography (SE), CT-FFR, single-photon emission computed tomography (SPECT), cardiac magnetic resonance (CMR), positron emission tomography (PET), ICA, and ICA-FFR. Proportion of correct diagnosis served as measure of clinical effectiveness. Incremental cost-effectiveness ratios were calculated for dominant strategies. Cost-effectiveness acceptability curves (CEAC) tested variation of cost-effectiveness threshold (CET).

Results

Base case (Table 1) consistent with probabilistic analysis (Figure 1 left). CEACs (Figure 1 right).

Conclusions

Direct ICA is not cost-effective. Functional testing has significant role in low/intermediate risk. CMR is cost-effective in all risk and most likely cost-effective in CETs &lt;£10,000. ICA-FFR yields highest correct diagnoses in all at highest cost. Future long-term follow-up studies with quality of life measures are needed.

References

1. Knuuti et al EHJ. 2018; 39(35):3322–30

2. Danad et al. EHJ. 2016; 38(13):991–8.

Figure 1. A: low, B: intermediate, C: high.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): The authors acknowledge financial support from the Department of Health through the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy's & St Thomas' NHS Foundation Trust in partnership with King's College London and King's College Hospital NHS Foundation Trust and by the NIHR MedTech Co-operative for Cardiovascular Disease at Guy's and St Thomas' NHS Foundation Trust. This abstract presents independent research funded by the National Institute for Health Research (NIHR) under its Research for Patient Benefit (RfPB) Programme (Grant Reference Number PB-PG-0416-20008). This work was supported by the Wellcome/EPSRC Centre for Medical Engineering [WT 203148/Z/16/Z]. MSN was funded by the UK Medical Research Council under grant number MR/P01979X/1. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care, EPSRC, MRC or the Wellcome Trust.

2380Mechanisms of myocardial ischemia during exercise in microvascular angina

Background

Coronary microvascular dysfunction (MVD) is defined by impaired flow augmentation in response to a vasodilator, the pathophysiological basis of which is unclear. This study sought to address two major gaps in our understanding of MVD: firstly, whether diminished flow reserve is due to structural changes within the microvasculature or potentially reversible dysfunction and secondly to unravel the mechanism of exercise-induced ischemia in the absence of obstructive disease.

Methods

Simultaneous intracoronary pressure and flow velocity recordings were made in the left anterior descending artery of patients with angina and no obstructive epicardial disease (Fractional Flow Reserve >0.80). Measurements were made at rest, during adenosine-mediated hyperaemia and supine bicycle exercise. Wave intensity analysis was used to quantify waves that accelerate and decelerate coronary blood flow, coronary perfusion efficiency being defined as the proportion of total wave energy that accelerates blood flow. Patients were prospectively classified into MVD (coronary flow reserve <2.5) and controls with researchers blinded to the classification throughout the protocol. Myocardial perfusion and vascular function were assessed by 3T cardiac MRI and venous occlusion plethysmography with forearm blood flow (FBF) assessment during serial infusions of acetylcholine, adenosine and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).

Results

78 patients were enrolled (42 patients had MVD and 36 were controls), with no differences in cardiovascular risk factors between groups. The MVD group had elevated coronary blood flow (21.3±6.4 vs. 15.1±4.5cm s–1; p<0.001) and global myocardial perfusion (1.36±0.37 vs. 1.13±0.22ml/min/g; p=0.01) at rest. Maximum coronary and myocardial blood flow during hyperaemia was similar in both groups. During exercise, MVD patients achieved similar peak flow (30.5±10.0 vs. 26.3±7.7cm s–1; p=0.07) despite a higher rate-pressure product (20777±5205 vs. 17450±4710bpm.mmHg; p=0.01). Coronary perfusion efficiency, decreased with exercise in the MVD group (61±11% vs. 44±10% p<0.001) but was unchanged in controls. On MRI, MVD had lower hyperaemic endo-epicardial perfusion ratio than controls (0.94±0.08 vs. 1.04±0.13; p=0.001). Augmentation of FBF with acetylcholine was attenuated in MVD patients compared to controls (p=0.02) but the response to adenosine was similar (p=0.13). Infusion of L-NMMA caused a significantly greater reduction in FBF in MVD patients compared to controls (p<0.001).

Exercise Physiology in MVD

Conclusion

Impaired flow reserve in MVD represents a dysfunctional state, characterised by inappropriately elevated resting flow due to increased nitric-oxide synthase mediated vasodilatation. There is abnormal flow distribution in the myocardium predisposing to subendocardial ischaemia, associated with and exacerbated by impaired cardiac-coronary coupling during exercise. These novel findings may represent distinct therapeutic targets.

Acknowledgement/Funding

British Heart Foundation

P6484Invasive and non-invasive characterisation of low gradient aortic stenosis

Background

Low gradient severe aortic stenosis (LGAS) is associated with unfavourable outcomes when compared to high gradient aortic stenosis (HGAS), yet the contributing pathophysiology is poorly understood.

Methods

Symptomatic LGAS and HGAS patients undergoing trans-catheter aortic valve implantation (TAVI) underwent 3T stress perfusion cardiac magnetic resonance imaging (CMR) pre-(within 24 hours) and post-(4–6 months) TAVI. Left ventricular (LV) contractility and coronary flow/pressure were measured during hyperaemia and rapid pacing, immediately before and after TAVI, using a conductance LV catheter and dual-pressure and Doppler sensor–tipped guidewire in the mid-left anterior descending coronary artery.

Results

24 patients were recruited resulting in 19 suitable datasets (LGAS N=9, HGAS N=10, equally matched for comorbidities and B-natriuretic peptide level). LGAS patients had a smaller LV end diastolic volume index (p=0.035) and lower LV mass index (LVMI) (p=0.037). Pre-TAVI stress global endocardium-epicardium gradient was 0.88±0.09 and global myocardial perfusion reserve (MPR) 2.0±0.48 in 14 patients (6 LGAS and 8 HGAS patients, no difference between groups). Pre-TAVI, baseline coronary data demonstrated lower augmentation pressure (AP, p=0.035) and augmentation index (AIx, p=0.02) in the LGAS group. LGAS patients also exhibited a shorter ejection time (p=0.015), larger forward compression waves during rest, hyperaemia and rapid pacing, and smaller backward expansion waves (BEW) (p=0.001). Lower baseline end systolic pressure (p=0.004), inotropy (dP/dt+, p=0.045), lusitropy (dP/dt-, p=0.069), and stroke work (p=0.019) were observed in the LGAS group. Whilst LV size was smaller the LGAS group, rapid pacing induced a more significant drop in end systolic volume (p=0.045) and ejection fraction (p=0.015) in patients with HGAS. Post-TAVI, the hyperaemic BEW fell sharply (p<0.001), along with coronary VTI (p=0.02), and average pulse velocity (p=0.028), and AP and AIx remained lower (p=0.034 and p=0.031, respectively). The forward expansion wave was reduced in LGAS during rapid pacing. The HGAS group displayed a more profound drop in dP/dt+ (p=0.011) and dP/dt- p=0.014) at rest following intervention. Repeat CMR demonstrated statistically significant reduction in LV size and LVMI (p=0.012 and p<0.001, respectively) with significant increase in 3D global peak radial, circumferential and longitudinal strain (p=0.004, p=0.001 and p=0.018, respectively). Post-TAVI stress global endocardium-epicardium gradient was 0.88±0.13 and MPR 2.46±0.59 (improved from pre-TAVI, p=0.05). There was no difference in remodelling patterns or perfusion between the two groups.

Conclusion

This is the first study detailing the combined invasive and CMR pathophysiological changes in LGAS. Despite invasive parameters indicating a disease of less severe AS, the level of perfusion abnormality is disproportionate which may in part, relate to their adverse prognosis.

Acknowledgement/Funding

This research is funded by a Clinical Research Training Fellowship grant from the British Heart Foundation (FS/16/51/32365).

Rest perfusion abnormalities in hypertrophic cardiomyopathy: correlation with myocardial fibrosis and risk factors for sudden cardiac death

Aim

To measure the prevalence of abnormal rest perfusion in a population of consecutive patients with known hypertrophic cardiomyopathy (HCM) referred for cardiovascular MRI (CMR), and to assess any associations between abnormal rest perfusion and the presence, pattern, and severity of myocardial scar and the presence of risk factors for sudden death.

Materials and methods

Eighty consecutive patients with known HCM referred for CMR underwent functional imaging, rest first-pass perfusion, and late gadolinium enhancement (LGE).

Results

Thirty percent of the patients had abnormal rest perfusion, all of them corresponding to areas of mid-myocardial LGE and to a higher degree of segmental hypertrophy. Rest perfusion abnormalities correlated with more extensive and confluent LGE. The subgroup of patients with myocardial fibrosis and rest perfusion abnormalities (fibrosis+/perfusion+) had more than twice the incidence of episodes of non-sustained ventricular tachycardia on Holter monitoring in comparison to patients with myocardial fibrosis and normal rest perfusion (fibrosis+/perfusion–) and patients with no fibrosis and normal rest perfusion (fibrosis–/perfusion–).

Conclusions

First-pass perfusion CMR identifies abnormal rest perfusion in a significant proportion of patients with HCM. These abnormalities are associated with the presence and distribution of myocardial scar and the degree of hypertrophy. Rest perfusion abnormalities identify patients with increased incidence of episodes of non-sustained ventricular tachycardia on Holter monitoring, independently from the presence of myocardial fibrosis.

•

30% of patients with HCM have perfusion abnormalities related to scar.

•

No rest perfusion abnormalities were observed in areas of viable myocardium.

•

Scar-related perfusion abnormalities were associated with the incidence of NSVT.

Quantitative myocardial perfusion imaging by cardiovascular magnetic resonance and positron emission tomography

Recent studies have demonstrated that a detailed knowledge of the extent of angiographic coronary artery disease (CAD) is not a prerequisite for clinical decision making, and the clinical management of patients with CAD is more and more focused towards the identification of myocardial ischemia and the quantification of ischemic burden. In this view, non-invasive assessment of ischemia and in particular stress imaging techniques are emerging as preferred and non-invasive options. A quantitative assessment of regional myocardial perfusion can provide an objective estimate of the severity of myocardial injury and may help clinicians to discriminate regions of the heart that are at increased risk for myocardial infarction. Positron emission tomography (PET) has established itself as the reference standard for myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) quantification. Cardiac magnetic resonance (CMR) is increasingly used to measure MBF and MPR by means of first-pass signals, with a well-defined diagnostic performance and prognostic value. The aim of this article is to review the currently available evidence on the use of both PET and CMR for quantification of MPR, with particular attention to the studies that directly compared these two diagnostic methods.

Quantitative analysis of transmural gradients in myocardial perfusion magnetic resonance images

Conventional quantitative assessments of myocardial perfusion analyze the temporal relation between the arterial input function and the myocardial signal intensity curves, thereby neglecting the important spatial relation between the myocardial signal intensity curves. The new method presented in this article enables characterization of sub-endocardial to sub-epicardial gradients in myocardial perfusion based on a two dimensional, "gradientogram" representation, which displays the evolution of the transmural gradient in myocardial contrast uptake over time in all circumferential positions of the acquired images. Moreover, based on segmentation in these gradientograms, several new measurements that characterize transmural myocardial perfusion distribution over time are defined. In application to clinical image data, the new two-dimensional representations, as well as the newly defined measurements revealed a clear distinction between normal perfusion and inducible ischaemia. Thus, the new measurements may serve as diagnostic markers for the detection and characterization of epicardial coronary and microvascular disease.

Activity of endothelial factors on myocardial inotropy

Both nitric oxide (NO) and endothelins can either increase or decrease myocardial contractility. A positive inotropic effect occurs in response to low NO concentrations, whereas a negative effect is brought about by high concentrations. Activation of protein kinase A and protein kinase G accounts for the increase and decrease in contractility respectively. Basal NO concentration is virtually unknown so that when NO-donors and NOS stimulators add newly released NO, the most frequent effect is a decrease in contractility. This negative inotropic effect represents a protection against the maladaptative activity of the increased production of angiotensin II and cathecholamines in heart failure. Unlike NO, the main effect of endothelins is an increase in contractility. While the increase in contractility is attributed to an activation of Na+/H+ and Na+/Ca2+ exchangers a decrease seems to depend on the triggering of NO-cGMP pathway by endothelin receptors B. Since endothelin concentration increases in several cardiovascular diseases, the blockade of endothelin receptors has been suggested as a therapeutic tool. The study of the endothelial-dependent repolarizing factors revealed the inotropic activity of 14,15 isoform of epoxi-eicosatrienoic acids.

Surgical revascularization in the ischemic heart disease. Long-term results in a series of consecutive patients selected according to the principles

AIM

Ischemic heart disease can be treated with drugs, percutaneous coronary interventions (PCI) and surgical revascularization (CABG). In our institution the therapeutic decisions for non emergent cases have been regularly taken during a daily meeting attended by clinicians, interventionalists, and surgeons, who all adhere to the principles of Evidence Based Medicine. The purpose of the present report is to investigate the long-term results in a series of consecutive patients to whom surgical revascularization has been recommended following the abovementioned approach.

METHODS

We selected 597 patients with no prior interventions, who were referred to our institution for coronary angiography between January 1991 and December 1997 and to whom surgical revascularization was recommended. The Kaplan-Meier method was adopted to evaluate survival and freedom from: non fatal acute myocardial infarction, PCI, repeat CABG.

RESULTS

The results were compared to those of the randomized trials or of large follow-up reports. The mean observation period was 6.8 years. The results at 5 and 10 years were: overall survival 95.5% and 90.2%; freedom from acute myocardial infarction 95.5% and 90.2%; freedom from surgical reintervention 98.6% and 97.1%; freedom from PCI 91.2% and 79.8%; survival free from all events 79.3% and 58.1%. These rates were comparable to those reported by the most important clinical trials.

CONCLUSIONS

If surgical treatment for patient with coronary artery disease is recommended according to the suggestions of the leading clinical trials and pertinent guidelines, the results in terms of mortality and morbidity are comparable to those of the trials themselves, even in the non selected patients of daily clinical practice.

Fatty acids are important for the Frank-Starling mechanism and Gregg effect but not for catecholamine response in isolated rat hearts

In some pathophysiological conditions myocardial metabolism can switch from mainly long chain fatty acid (LCFA) oxidation to mainly glucose oxidation. Whether the predominant fatty acid or glucose oxidation affects cardiac performance has not been defined. In a buffer perfused isovolumetrically contracting rat heart, oxidation of endogenous pool LCFA was avoided by inhibiting carnitine-palmitoyl-transferase I (CPT-I) with oxfenicine (2 mM). In order to restore fatty acid oxidation, hexanoate (1 mM), which bypasses CPT-I inhibition, was added to the perfusate. Three groups of hearts were subjected to either an increase in left ventricular volume (VV, +25%) or an increase in coronary flow (CF, +50%), or inotropic stimulation with isoproterenol (10(-8) and 10(-6) m). The increase in VV (the Frank-Starling mechanism) increased rate-pressure product (RPP) by 21 +/- 2% under control conditions, but only by 6 +/- 2% during oxfenicine-induced CPT-I inhibition. The contractile response to changes in VV recovered after the addition of hexanoate. Similar results were obtained in hearts, in which an increase in CF was elicited (the Gregg phenomenon). Isoproterenol caused a similar increase in contractility regardless of the presence of oxfenicine or hexanoate. In all groups, a commensurate increase in oxygen consumption accompanied the increase in contractility. The fatty acid oxidation is necessary for an adequate contractile response of the isolated heart to increased pre-load or flow, whereas the inotropic response to adrenergic beta-receptor stimulation is insensitive to changes in substrate availability.

Cytochrome P-450 metabolite of arachidonic acid mediates bradykinin-induced negative inotropic effect

This study focused on the mechanisms of the negative inotropic response to bradykinin (BK) in isolated rat hearts perfused at constant flow. BK (100 nM) significantly reduced developed left ventricular pressure (LVP) and the maximal derivative of systolic LVP by 20-22%. The cytochrome P-450 (CYP) inhibitors 1-aminobenzotriazole (1 mM and 100 microM) or proadifen (5 microM) abolished the cardiodepression by BK, which was not affected by nitric oxide and cyclooxygenase inhibitors (35 microM NG-nitro-L-arginine methyl ester and 10 microM indomethacin, respectively). The CYP metabolite 14,15-epoxyeicosatrienoic acid (14,15-EET; 50 ng/ml) produced effects similar to those of BK in terms of the reduction in contractility. After the coronary endothelium was made dysfunctional by Triton X-100 (0.5 microl), the BK-induced negative inotropic effect was completely abolished, whereas the 14,15-EET-induced cardiodepression was not affected. In hearts with normal endothelium, after recovery from 14,15-EET effects, BK reduced developed LVP to a 35% greater extent than BK in the control. In conclusion, CYP inhibition or endothelial dysfunction prevents BK from causing cardiodepression, suggesting that, in the rat heart, endothelial CYP products mediate the negative inotropic effect of BK. One of these mediators appears to be 14,15-EET.

Coronary reactive hyperaemia after two periods of coronary occlusion in the anaesthetized goat

In the coronary circulation an ischaemic preconditioning obtained with two periods of 2.5 min each of occlusion of the left circumflex coronary artery alters the pattern of a coronary reactive hyperaemia which follows 15 s only of occlusion of the studied artery. The most remarkable change consists of a reduction of 40-45% of the time required by the flow to reach the maximum hyperaemic peak (time to peak) after the brief occlusion. The present investigation was planned to study whether the time to peak of the hyperaemia following the second 2.5 min preconditioning occlusion was shorter than the hyperaemia following the first occlusion. Experiments performed in the anaesthetized goat, in which coronary flow was measured with an electromagnetic flow-probe placed around the left circumflex coronary artery showed that in the hyperaemia occurring after the second preconditioning occlusion the time to peak was reduced by 18% only. The moderate effect of the second preconditioning occlusion in reducing the time to peak is attributed to the fact that the heart was already partially preconditioned after the first occlusion and that after relatively long periods (2.5 min) of occlusion the metabolic component of the hyperaemic response was so predominant to partially mask the role of the vascular mechanisms presumably responsible for the reduction of the time to peak.