Post-Myocardial Infarction Remodeling and Hyperkinetic Remote Myocardium in Sheep Measured by Cardiac MRI Feature Tracking.

BACKGROUND: Cardiac MRI feature tracking (FT) allows objective assessment of segmental left ventricular (LV) function following a myocardial infarction (MI), but its utilization in sheep, where interventions can be tested, is lacking. PURPOSE: To apply and validate FT in a sheep model of MI and describe post-MI LV remodeling. STUDY TYPE: Animal model, longitudinal. ANIMAL MODEL: Eighteen lambs (6 months, male, n = 14; female, n = 4; 25.2 ± 4.5 kg). FIELD STRENGTH/SEQUENCE: Two-dimensional balanced steady-state free precession (bSSFP) and 3D inversion recovery fast low angle shot (IR-FLASH) sequences at 3 T. ASSESSMENT: Seven lambs underwent test-retest imaging to assess FT interstudy reproducibility. MI was induced in the remaining 11 by coronary ligation with MRI being undertaken before and 15 days post-MI. Injury size was measured by late gadolinium enhancement (LGE) and LV volumes, LV mass, ejection fraction (LVEF), and wall thickness (LVWT) were measured, with FT measures of global and segmental radial, circumferential, and longitudinal strain. STATISTICAL TESTS: Sampling variability, inter-study, intra and interobserver reproducibility were assessed using Pearson's correlation, Bland-Altman analyses, and intra-class correlation coefficients (ICC). Diagnostic performance of segmental strain to predict LGE was assessed using receiver operating characteristic curve analysis. Significant differences were considered P < 0.05. RESULTS: Inter-study reproducibility of FT was overall good to excellent, with global strain being more reproducible than segmental strain (ICC = 0.89-0.98 vs. 0.77-0.96). MI (4.0 ± 3.7% LV mass) led to LV remodeling, as evident by significantly increased LV volumes and LV mass, and significantly decreased LVWT in injured regions, while LVEF was preserved (54.9 ± 6.9% vs. 55.6 ± 5.7%; P = 0.778). Segmental circumferential strain (CS) correlated most strongly with LGE. Basal and mid- CS increased significantly, while apical CS significantly decreased post-MI. DATA CONCLUSION: FT is reproducible and compensation by hyperkinetic remote myocardium may manifest as overall preserved global LV function. EVIDENCE LEVEL: N/A TECHNICAL EFFICACY: Stage 2.

CSANZ and RANZCR Position Statement on Initial Certification and Maintenance of Recognition for Cardiac Magnetic Resonance Imaging (CMRI).

The CSANZ/RANZCR Position Statement on Cardiac Magnetic Resonance Imaging (CMRI) is intended to support and foster the provision of quality, safe CMRI services in Australia and New Zealand. This document specifically pertains to CMRI in adults, as distinct from general vascular MRI or paediatric imaging, and provides certification and recertification requirements.

Initial Invasive or Conservative Strategy for Stable Coronary Disease.

BACKGROUND: Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS: We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS: Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, -1.8 percentage points; 95% CI, -4.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS: Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used. (Funded by the National Heart, Lung, and Blood Institute and others; ISCHEMIA ClinicalTrials.gov number, NCT01471522.).

Burden of mood symptoms and disorders in implantable cardioverter defibrillator patients: a systematic review and meta-analysis of 39 954 patients.

AIMS: Implantable cardioverter defibrillators (ICDs) prevent sudden cardiac death. Anxiety, depression, and post-traumatic stress disorder (PTSD) are underappreciated symptoms. We aimed to systematically synthesize prevalence estimates of mood disorders and symptom severities, pre- and post-ICD insertions. Comparisons were made with control groups, as well as within ICD patients by indication (primary vs. secondary), sex, shock status, and over time. METHODS: Databases (Medline, PsycINFO, PubMed, and Embase) were searched without limits from inception to 31 August 2022; 4661 articles were identified, 109 (39 954 patients) of which met criteria. RESULTS: Random-effects meta-analyses revealed clinically relevant anxiety in 22.58% (95%CI 18.26-26.91%) of ICD patients across all timepoints following insertion and depression in 15.42% (95%CI 11.90-18.94%). Post-traumatic stress disorder was seen in 12.43% (95%CI 6.90-17.96%). Rates did not vary relative to indication group. Clinically relevant anxiety and depression were more likely in ICD patients who experienced shocks [anxiety odds ratio (OR) = 3.92 (95%CI 1.67-9.19); depression OR = 1.87 (95%CI 1.34-2.59)]. Higher symptoms of anxiety were seen in females than males post-insertion [Hedges' g = 0.39 (95%CI 0.15-0.62)]. Depression symptoms decreased in the first 5 months post-insertion [Hedges' g = 0.13 (95%CI 0.03-0.23)] and anxiety symptoms after 6 months [Hedges' g = 0.07 (95%CI 0-0.14)]. CONCLUSION: Depression and anxiety are highly prevalent in ICD patients, especially in those who experience shocks. Of particular concern is the prevalence of PTSD following ICD implantation. Psychological assessment, monitoring, and therapy should be offered to ICD patients and their partners as part of routine care.

Non-linear Mendelian randomization analyses support a role for vitamin D deficiency in cardiovascular disease risk.

AIMS: Low vitamin D status is associated with a higher risk for cardiovascular diseases (CVDs). Although most existing linear Mendelian randomization (MR) studies reported a null effect of vitamin D on CVD risk, a non-linear effect cannot be excluded. Our aim was to apply the non-linear MR design to investigate the association of serum 25-hydroxyvitamin D [25(OH)D] concentration with CVD risk. METHODS AND RESULTS: The non-linear MR analysis was conducted in the UK Biobank with 44 519 CVD cases and 251 269 controls. Blood pressure (BP) and cardiac-imaging-derived phenotypes were included as secondary outcomes. Serum 25(OH)D concentration was instrumented using 35 confirmed genome-wide significant variants.We also estimated the potential reduction in CVD incidence attributable to correction of low vitamin D status. There was a L-shaped association between genetically predicted serum 25(OH)D and CVD risk (Pnon-linear = 0.007), where CVD risk initially decreased steeply with increasing concentrations and levelled off at around 50 nmol/L. A similar association was seen for systolic (Pnon-linear = 0.03) and diastolic (Pnon-linear = 0.07) BP. No evidence of association was seen for cardiac-imaging phenotypes (P = 0.05 for all). Correction of serum 25(OH)D level below 50 nmol/L was predicted to result in a 4.4% reduction in CVD incidence (95% confidence interval: 1.8- 7.3%). CONCLUSION: Vitamin D deficiency can increase the risk of CVD. Burden of CVD could be reduced by population-wide correction of low vitamin D status.

Prognostic Value of Nonischemic Ringlike Left Ventricular Scar in Patients With Apparently Idiopathic Nonsustained Ventricular Arrhythmias.

BACKGROUND: Left ventricular (LV) scar on late gadolinium enhancement (LGE) cardiac magnetic resonance has been correlated with life-threatening arrhythmic events in patients with apparently idiopathic ventricular arrhythmias (VAs). We investigated the prognostic significance of a specific LV-LGE phenotype characterized by a ringlike pattern of fibrosis. METHODS: A total of 686 patients with apparently idiopathic nonsustained VA underwent contrast-enhanced cardiac magnetic resonance. A ringlike pattern of LV scar was defined as LV subepicardial/midmyocardial LGE involving at least 3 contiguous segments in the same short-axis slice. The end point of the study was time to the composite outcome of all-cause death, resuscitated cardiac arrest because of ventricular fibrillation or hemodynamically unstable ventricular tachycardia and appropriate implantable cardioverter defibrillator therapy. RESULTS: A total of 28 patients (4%) had a ringlike pattern of scar (group A), 78 (11%) had a non-ringlike pattern (group B), and 580 (85%) had normal cardiac magnetic resonance with no LGE (group C). Group A patients were younger compared with groups B and C (median age, 40 vs 52 vs 45 years; P<0.01), more frequently men (96% vs 82% vs 55%; P<0.01), with a higher prevalence of family history of sudden cardiac death or cardiomyopathy (39% vs 14% vs 6%; P<0.01) and more frequent history of unexplained syncope (18% vs 9% vs 3%; P<0.01). All patients in group A showed VA with a right bundle-branch block morphology versus 69% in group B and 21% in group C (P<0.01). Multifocal VAs were observed in 46% of group A patients compared with 26% of group B and 4% of group C (P<0.01). After a median follow-up of 61 months (range, 34-84 months), the composite outcome occurred in 14 patients (50.0%) in group A versus 15 (19.0%) in group B and 2 (0.3%) in group C (P<0.01). After multivariable adjustment, the presence of LGE with ringlike pattern remained independently associated with increased risk of the composite end point (hazard ratio, 68.98 [95% CI, 14.67-324.39], P<0.01). CONCLUSIONS: In patients with apparently idiopathic nonsustained VA, nonischemic LV scar with a ringlike pattern is associated with malignant arrhythmic events.

Evidence-based cardiovascular magnetic resonance cost-effectiveness calculator for the detection of significant coronary artery disease.

BACKGROUND: Although prior reports have evaluated the clinical and cost impacts of cardiovascular magnetic resonance (CMR) for low-to-intermediate-risk patients with suspected significant coronary artery disease (CAD), the cost-effectiveness of CMR compared to relevant comparators remains poorly understood. We aimed to summarize the cost-effectiveness literature on CMR for CAD and create a cost-effectiveness calculator, useable worldwide, to approximate the cost-per-quality-adjusted-life-year (QALY) of CMR and relevant comparators with context-specific patient-level and system-level inputs. METHODS: We searched the Tufts Cost-Effectiveness Analysis Registry and PubMed for cost-per-QALY or cost-per-life-year-saved studies of CMR to detect significant CAD. We also developed a linear regression meta-model (CMR Cost-Effectiveness Calculator) based on a larger CMR cost-effectiveness simulation model that can approximate CMR lifetime discount cost, QALY, and cost effectiveness compared to relevant comparators [such as single-photon emission computed tomography (SPECT), coronary computed tomography angiography (CCTA)] or invasive coronary angiography. RESULTS: CMR was cost-effective for evaluation of significant CAD (either health-improving and cost saving or having a cost-per-QALY or cost-per-life-year result lower than the cost-effectiveness threshold) versus its relevant comparator in 10 out of 15 studies, with 3 studies reporting uncertain cost effectiveness, and 2 studies showing CCTA was optimal. Our cost-effectiveness calculator showed that CCTA was not cost-effective in the US compared to CMR when the most recent publications on imaging performance were included in the model. CONCLUSIONS: Based on current world-wide evidence in the literature, CMR usually represents a cost-effective option compared to relevant comparators to assess for significant CAD.

Impact of Surgical and Transcatheter Aortic Valve Replacement on Frailty Score.

OBJECTIVE: Frailty is common in the aortic stenosis (AS) population and impacts outcomes after both transcatheter and surgical aortic valve replacement (TAVR and sAVR, respectively). Frailty can significantly impact the decision regarding the suitability of a patient for aortic valve intervention, with frail patients often excluded. Since many frailty tools use indicators which may be influenced by AS itself, some of which are subjectively symptom driven, we sought to determine the impact of intervention on frailty scores. METHODS: A prospective, observational cohort study included patients being assessed for aortic valve (AV) intervention with either TAVR or sAVR due to severe aortic stenosis. Patients were assessed for symptoms at baseline, and 1- and 6-months post intervention subjectively, using the New York Heart Association (NYHA) class and the Kansas City Cardiomyopathy Questionnaire (KCCQ), and objectively, using a 6-minute walk test (6MWT). These were compared with frailty at baseline and final review using the Fried Frailty Scale (FFS). RESULTS AND CONCLUSIONS: Sixty-six (66) patients completed pre- and post-intervention reviews. The mean FFS score was significantly lower, indicating less frailty, at 6 months relative to pre procedure (1.18 vs 1.73, p=0.002). This correlated with the change in symptoms (p<0.001). Between intervention groups, the final mean FFS of both groups decreased significantly, with TAVR to 1.33 (p=0.030) and sAVR to 0.8 (p=0.015). There was no difference in the degree of improvement between interventions (p=0.517). Aortic valve intervention improves frailty scores in both TAVR and sAVR treated patients.

Initial Invasive Versus Conservative Management of Stable Ischemic Heart Disease in Patients With a History of Heart Failure or Left Ventricular Dysfunction: Insights From the ISCHEMIA Trial.

BACKGROUND: Whether an initial invasive strategy in patients with stable ischemic heart disease and at least moderate ischemia improves outcomes in the setting of a history of heart failure (HF) or left ventricular dysfunction (LVD) when ejection fraction is ≥35% but <45% is unknown. METHODS: Among 5179 participants randomized into ISCHEMIA (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches), all of whom had left ventricular ejection fraction (LVEF) ≥35%, we compared cardiovascular outcomes by treatment strategy in participants with a history of HF/LVD at baseline versus those without HF/LVD. Median follow-up was 3.2 years. RESULTS: There were 398 (7.7%) participants with HF/LVD at baseline, of whom 177 had HF/LVEF >45%, 28 HF/LVEF 35% to 45%, and 193 LVEF 35% to 45% but no history of HF. HF/LVD was associated with more comorbidities at baseline, particularly previous myocardial infarction, stroke, and hypertension. Compared with patients without HF/LVD, participants with HF/LVD were more likely to experience a primary outcome composite of cardiovascular death, nonfatal myocardial infarction, or hospitalization for unstable angina, HF, or resuscitated cardiac arrest (4-year cumulative incidence rate, 22.7% versus 13.8%; cardiovascular death or myocardial infarction, 19.7% versus 12.3%; and all-cause death or HF, 15.0% versus 6.9%). Participants with HF/LVD randomized to the invasive versus conservative strategy had a lower rate of the primary outcome (17.2% versus 29.3%; difference in 4-year event rate, -12.1% [95% CI, -22.6 to -1.6%]), whereas those without HF/LVD did not (13.0% versus 14.6%; difference in 4-year event rate, -1.6% [95% CI, -3.8% to 0.7%]; P interaction = 0.055). A similar differential effect was seen for the primary outcome, all-cause mortality, and cardiovascular mortality when invasive versus conservative strategy-associated outcomes were analyzed with LVEF as a continuous variable for patients with and without previous HF. CONCLUSIONS: ISCHEMIA participants with stable ischemic heart disease and at least moderate ischemia with a history of HF or LVD were at increased risk for the primary outcome. In the small, high-risk subgroup with HF and LVEF 35% to 45%, an initial invasive approach was associated with better event-free survival. This result should be considered hypothesis-generating. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01471522.

Randomized controlled trial of perhexiline on regression of left ventricular hypertrophy in patients with symptomatic hypertrophic cardiomyopathy (RESOLVE-HCM trial).

BACKGROUND: The presence and extent of left ventricular hypertrophy (LVH) is a major determinant of symptoms in patients with hypertrophic cardiomyopathy (HCM). There is increasing evidence to suggest that myocardial energetic impairment represents a central mechanism leading to LVH in HCM. There is currently a significant unmet need for disease-modifying therapy that regresses LVH in HCM patients. Perhexiline, a potent carnitine palmitoyl transferase-1 (CPT-1) inhibitor, improves myocardial energetics in HCM, and has the potential to reduce LVH in HCM. OBJECTIVE: The primary objective is to evaluate the effects of perhexiline treatment on the extent of LVH, in symptomatic HCM patients with at least moderate LVH. METHODS/DESIGN: RESOLVE-HCM is a prospective, multicenter double-blind placebo-controlled randomized trial enrolling symptomatic HCM patients with at least moderate LVH. Sixty patients will be randomized to receive either perhexiline or matching placebo. The primary endpoint is change in LVH, assessed utilizing cardiovascular magnetic resonance (CMR) imaging, after 12-months treatment with perhexiline. SUMMARY: RESOLVE-HCM will provide novel information on the utility of perhexiline in regression of LVH in symptomatic HCM patients. A positive result would lead to the design of a Phase 3 clinical trial addressing long-term effects of perhexiline on risk of heart failure and mortality in HCM patients.

Atrial fibrosis and substrate based characterization in atrial fibrillation: Time to move forwards.

Atrial fibrillation (AF) is the most commonly encountered cardiac arrhythmia in clinical practice. However, current therapeutic interventions for atrial fibrillation have limited clinical efficacy as a consequence of major knowledge gaps in the mechanisms sustaining atrial fibrillation. From a mechanistic perspective, there is increasing evidence that atrial fibrosis plays a central role in the maintenance and perpetuation of atrial fibrillation. Electrophysiologically, atrial fibrosis results in alterations in conduction velocity, cellular refractoriness, and produces conduction block promoting meandering, unstable wavelets and micro-reentrant circuits. Clinically, atrial fibrosis has also linked to poor clinical outcomes including AF-related thromboembolic complications and arrhythmia recurrences post catheter ablation. In this article, we review the pathophysiology behind the formation of fibrosis as AF progresses, the role of fibrosis in arrhythmogenesis, surrogate markers for detection of fibrosis using cardiac magnetic resonance imaging, echocardiography and electroanatomic mapping, along with their respective limitations. We then proceed to review the current evidence behind therapeutic interventions targeting atrial fibrosis, including drugs and substrate-based catheter ablation therapies followed by the potential future use of electro phenotyping for AF characterization to overcome the limitations of contemporary substrate-based methodologies.

Right ventricular myocardial deoxygenation in patients with pulmonary artery hypertension.

BACKGROUND: In pulmonary arterial hypertension (PAH), progressive right ventricular (RV) dysfunction is believed to be largely secondary to RV ischaemia. A recent pilot study has demonstrated the feasibility of Oxygen-sensitive (OS) cardiovascular magnetic resonance (CMR) to detect in-vivo RV myocardial oxygenation. The aims of the present study therefore, were to assess the prevalence of RV myocardial ischaemia and relationship with RV myocardial interstitial changes in PAH patients with non-obstructive coronaries, and corelate with functional and haemodynamic parameters. METHODS: We prospectively recruited 42 patients with right heart catheter (RHC) proven PAH and 11 healthy age matched controls. The CMR examination involved standard functional imaging, OS-CMR imaging and native T1 mapping. An ΔOS-CMR signal intensity (SI) index (stress/rest signal intensity) was acquired at RV anterior, RV free-wall and RV inferior segments. T1 maps were acquired using Shortened Modified Look-Locker Inversion recovery (ShMOLLI) at the inferior RV segment. RESULTS: The inferior RV ΔOS-CMR SI index was significantly lower in PAH patients compared with healthy controls (9.5 (- 7.4-42.8) vs 12.5 (9-24.6)%, p = 0.02). The inferior RV ΔOS-CMR SI had a significant correlation to RV inferior wall thickness (r = - 0.7, p < 0.001) and RHC mean pulmonary artery pressure (mPAP) (r = - 0.4, p = 0.02). Compared to healthy controls, patients with PAH had higher native T1 in the inferior RV wall: 1303 (1107-1612) vs 1232 (1159-1288)ms, p = 0.049. In addition, there was a significant difference in the inferior RV T1 values between the idiopathic PAH and systemic sclerosis associated PAH patients: 1242 (1107-1612) vs 1386 (1219-1552)ms, p = 0.007. CONCLUSION: Blunted OS-CMR SI suggests the presence of in-vivo microvascular RV dysfunction in PAH patients. The native T1 in the inferior RV segments is significantly increased in the PAH patients, particularly among the systemic sclerosis associated PAH group.

Cost-Effectiveness of Cardiovascular Magnetic Resonance in Diagnosing Coronary Artery Disease in the Australian Health Care System.

BACKGROUND: Coronary artery disease (CAD) remains a major public health problem in Australia and globally. A variety of imaging techniques allow for both anatomical and functional assessment of CAD and selection of the optimal investigation pathway is challenging. Cardiovascular magnetic resonance (CMR) is not widely used in Australia, partly due to perceived cost and lack of Federal Government reimbursement compared to the alternative techniques. The aim of this study was to estimate the cost-effectiveness of different diagnostic strategies in identifying significant CAD in patients with chest pain suggestive of angina using the evidence gathered in the Clinical Evaluation of Magnetic Resonance Imaging in Coronary Heart Disease 2 (CE-MARC trial), analysed from the Australian health care perspective. METHODS: A decision analytic model coupled with three distinct Markov models allowed eight potential clinical investigation strategies to be considered; combinations of exercise electrocardiogram stress testing (EST), single-photon emission computed tomography (SPECT), stress CMR, and invasive coronary angiography (ICA). Costs were from the Australian health care system in Australian dollars, and outcomes were measured in terms of quality-adjusted life-years. Parameter estimates were derived from the CE-MARC and EUropean trial on Reduction Of cardiac events with Perindopril in patients with stable coronary Artery disease (EUROPA) trials, and from reviews of the published literature. RESULTS: The most cost-effective diagnostic strategy, based on a cost-effectiveness threshold of $45,000 to $75,000 per QALY gained, was EST, followed by stress CMR if the EST was positive or inconclusive, followed by ICA if the stress CMR was positive or inconclusive; this held true in the base case and the majority of scenario analyses. CONCLUSIONS: This economic evaluation shows that an investigative strategy of stress CMR if EST is inconclusive or positive is the most cost-effective approach for diagnosing significant coronary disease in chest pain patients within the Australian health care system.

Differential gene responses 3 days following infarction in the fetal and adolescent sheep heart.

There are critical molecular mechanisms that can be activated to induce myocardial repair, and in humans this is most efficient during fetal development. The timing of heart development in relation to birth and the size/electrophysiology of the heart are similar in humans and sheep, providing a model to investigate the repair capacity of the mammalian heart and how this can be applied to adult heart repair. Myocardial infarction was induced by ligation of the left anterior descending coronary artery in fetal (105 days gestation when cardiomyocytes are proliferative) and adolescent sheep (6 mo of age when all cardiomyocytes have switched to an adult phenotype). An ovine gene microarray was used to compare gene expression in sham and infarcted (remote, border and infarct areas) cardiac tissue from fetal and adolescent hearts. The gene response to myocardial infarction was less pronounced in fetal compared with adolescent sheep hearts and there were unique gene responses at each age. There were also region-specific changes in gene expression between each age, in the infarct tissue, tissue bordering the infarct, and tissue remote from the infarction. In total, there were 880 genes that responded to MI uniquely in the adolescent samples compared with 170 genes in the fetal response, as well as 742 overlap genes that showed concordant direction of change responses to infarction at both ages. In response to myocardial infarction, there were specific changes in genes within pathways of mitochondrial oxidation, muscle contraction, and hematopoietic cell lineages, suggesting that the control of energy utilization and immune function are critical for effective heart repair. The more restricted gene response in the fetus may be an important factor in its enhanced capacity for cardiac repair.

Is Atrial Fibrillation a Stroke Risk Factor or Risk Marker? An Appraisal Using the Bradford Hill Framework for Causality.

Atrial fibrillation (AF) is strongly associated with stroke risk but association on its own does not necessarily imply causality. Is AF a cause (risk factor) of stroke? Would treatment that reduces AF burden also reduce the burden of stroke? Or, perhaps, AF is a risk marker associated with a vascular syndrome in which there is co-existing atrial structural and electrical remodelling that results in the clinical manifestation of AF and the risk of stroke in parallel. A number of recent studies appear to detach AF as a direct cause of stroke. Studies in which cardiac implantable devices have been used to collect AF data preceding stroke appear to show no immediate temporal relationship. The Global Anticoagulant Registry in the Field - Atrial Fibrillation (GARFIELD-AF) a large worldwide registry of non-valvular AF, has shown that the risk of death exceeds the risk of stroke and that mortality, together with stroke and bleeding risk, is predicted by other vascular risk factors, defined by the CHA2DS2VASc score. Sir Bradford Hill proposed criteria to assess whether two associated factors are causal, more than 50 years ago. This method of analysing cause and effect in a complex scenario could be applied to AF and stroke. This paper aims to clinically appraise the evidence for each criterion outlined by Bradford Hill to single out whether the collective data supports one or the other.

Effect of Balloon Aortic Valvuloplasty on Mortality in Patients With Severe Aortic Stenosis Prior to Conservative Treatment and Surgical or Transcatheter Aortic Valve Replacement.

BACKGROUND: Outcomes following an initial strategy of balloon aortic valvuloplasty (BAV) prior to medical therapy or intervention with surgical or transcatheter aortic valve replacement (SAVR or TAVR) are unclear in the modern transcatheter intervention era. METHODS: A retrospective, observational cohort study of the echocardiography, cardiothoracic surgery and TAVR databases between 1 January 2006 and 31 December 2016 was performed to compare outcomes between all patients with severe aortic stenosis (AS) treated with or without BAV prior to medical or invasive therapy. RESULTS: 3,142 patients were available for analysis. 223 BAV treated patients had lower mortality relative to medically treated patients, particularly early (20.1% v. 7.6% at 6 months, 58.1% v. 52.5% at 5 years). Over 5 years, the adjusted hazard ratio (HR) was 0.62 (95% CI 0.48-0.80, p < 0.001). Compared with 630 patients proceeding directly to intervention, 75 patients receiving BAV experienced a higher mortality (HR = 2.76, 95% CI 2.07-3.66, p < 0.001). No subsequent excess perioperative mortality was observed with BAV compared with those receiving surgery directly (HR = 1.45, 95% CI 0.91-2.31, p = 0.117). CONCLUSIONS: The risk associated with BAV is low, and improves mortality compared with medical therapy. Balloon aortic valvuloplasty treated patients have poorer outcomes, but treatment with BAV does not increase perioperative mortality and may lessen it.

Feasibility of phase-contrast cine magnetic resonance imaging for measuring blood flow in the sheep fetus.

Phase-contrast cine MRI (PC-MRI) is the gold-standard noninvasive technique for measuring vessel blood flow and has previously been applied in the human fetal circulation. We aimed to assess the feasibility of using PC-MRI to define the distribution of the fetal circulation in sheep. Fetuses were catheterized at 119-120 days of gestation (term, 150 days) and underwent MRI at ∼123 days of gestation under isoflurane anesthesia, ventilated at a FIO2 of 1.0. PC-MRI was performed using a fetal arterial blood pressure catheter signal for cardiac triggering. Blood flows were measured in the major fetal vessels, including the main pulmonary artery, ascending and descending aorta, superior vena cava, ductus arteriosus, left and right pulmonary arteries, umbilical vein, ductus venosus, and common carotid artery and were indexed to estimated fetal weight. The combined ventricular output, pulmonary blood flow, and flow across the foramen ovale were calculated from vessel flows. Intraobserver and interobserver agreement and reproducibility was assessed. Blood flow measurements were successfully obtained in 61 out of 74 vessels (82.4%) interrogated in 9 fetuses. There was good intraobserver [R = 0.998, P < 0.0001; intraclass correlation (ICC) = 0.997] and interobserver agreement (R = 0.996, P < 0.0001; ICC = 0.996). Repeated MRI measurements showed good reproducibility (R = 0.989, P = 0.0002; ICC = 0.990). We conclude that PC-MRI using fetal catheters for gating triggers is feasible in the major vessels of late gestation fetal sheep. This approach may provide a useful new tool for assessing the circulatory characteristics of fetal sheep models of human disease, including fetal growth restriction and congenital heart disease.

Echocardiography in Infiltrative Cardiomyopathy.

Left ventricular (LV) wall thickening can occur due to both physiological and pathological processes. Some LV wall thickening is caused by infiltrative cardiac deposition diseases - rare disorders from both inherited and acquired conditions, with varying systemic manifestations. They portend a poor prognosis and are generally not reversible except in rare circumstances when early diagnosis and treatment may alter the outcome (e.g., Fabry disease). Cardiac involvement is variable and depends on the degree of infiltration and type of infiltrate. These changes often lead to the development of abnormalities in both the relaxation and contractile function of the heart ultimately resulting in heart failure. Echocardiography is generally the first investigation of choice as it is easily available and gives valuable information about the thickness of the ventricular walls as well as systolic and diastolic function. It is also able to identify unique, characteristic features of the disease as well as detecting any haemodynamic sequelae. This review looks at the role of echocardiography in the diagnosis and prognosis of infiltrative cardiac deposition diseases.

The role of miRNA regulation in fetal cardiomyocytes, cardiac maturation and the risk of heart disease in adults.

Myocardial infarction is a primary contributor towards the global burden of cardiovascular disease. Rather than repairing the existing damage of myocardial infarction, current treatments only address the symptoms of the disease and reducing the risk of a secondary infarction. Cardiac regenerative capacity is dependent on cardiomyocyte proliferation, which concludes soon after birth in humans and precocial species such as sheep. Human fetal cardiac tissue has some ability to repair following tissue damage, whereas a fully matured human heart has minimal capacity for cellular regeneration. This is in contrast to neonatal mice and adult zebrafish hearts, which retain the ability to undergo cardiomyocyte proliferation and can regenerate cardiac tissue after birth. In mice and zebrafish models, microRNAs (miRNAs) have been implicated in the regulation of genes involved in cardiac cell cycle progression and regeneration. However, the significance of miRNA regulation in cardiomyocyte proliferation for humans and other large mammals, where the timing of heart development in relation to birth is similar, remains unclear. miRNAs may be valuable targets for therapies that promote cardiac repair after injury. Therefore, elucidating the role of specific miRNAs in large animals, where heart development closely resembles that of humans, remains vitally important for identifying therapeutic targets that may be translated into clinical practice focused on tissue repair.

Noninvasive imaging in cardiac deposition diseases.

Infiltrative cardiomyopathy represents a heterogeneous group of diseases of the heart tissue with similar phenotypic expression. The condition is rare, but can be easily mistaken for other more common conditions of the heart. The diagnosis of infiltrative cardiomyopathy is therefore challenging and has often required the use of invasive procedures in the past. In the last decade there have been great advances in non-invasive cardiac imaging modalities like echocardiography, cardiovascular magnetic resonance and nuclear imaging. Although no single imaging modality abnormality on its own is pathognomic for infiltrative cardiomyopathy, a combination of these different modalities are synergistic, and can greatly aid in the clinical diagnosis. In this review, we describe these advancements in non-invasive cardiac imaging modalities with a particular focus on cardiovascular magnetic resonance imaging. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:44-59.