A practical approach to cardiac imaging in adults with Duchenne muscular dystrophy - echocardiography or cardiac MRI?

Funding Acknowledgements

Type of funding sources: None.

Background

The incidence of cardiomyopathy in Duchenne muscular dystrophy (DMD) increases with age, accounting for up to 20% of mortality in the third decade of life. As patients are frequently asymptomatic until advanced stages of disease, imaging plays an essential role in screening for cardiac involvement and monitoring progression. Guidelines recommend annual transthoracic echocardiography assessment, with periodic use of cardiac magnetic resonance imaging (CMR). However, some studies suggest that CMR should be the gold standard imaging in DMD. This study aimed to review the use echo and CMR in adult patients with DMD, with particular focus on practical utility and real-world limitations.

Methods

 

A retrospective chart review of 24 patients attending our DMD cardiomyopathy clinic was undertaken. Demographic data including age, genotyping and medical therapy were noted. Results of cardiac imaging, as well as discussions regarding referral for CMR were recorded.

Results

All patients had echocardiography performed in our facility (table 1) and all had a documented discussion regarding referral for CMR in their medical notes. 15 patients (60%) were unsuitable for CMR and were not referred. Reasons were inability to lie flat due to breathing/claustrophobia (n = 12) and difficulty with positioning due to contractures (n = 9). 2 patients (8%) attended for CMR but were unable to proceed due to difficulty with positioning in the scanner. 4 patients (16.5%) had CMR performed, 3 additional patients were referred and awaited CMR. Results outlined in table 1 and image 1 show correlation between measurement of left ventricular ejection fraction (LVEF) on echo and CMR. Wall motion abnormalities and fibrosis were better detected with CMR. 

Conclusion

 

Significant limitations were seen with both imaging techniques. Accessibility of CMR for adults with DMD is poor, related primarily to the severity of underlying musculoskeletal and respiratory disease. Echocardiography is easily accessible, but images are frequently suboptimal. Despite this, strong correlation was seen in assessment of LV function in those who underwent both echocardiography and CMR, with indication that echocardiography can accurately guide intensification of medications and cardiac device therapy. CMR remains the optimal modality for the assessment of myocardial fibrosis. Improving accessibility of CMR for patients with DMD should be prioritised for the future of this modality.

1266Novel formin homology 2 domain containing 3 (FHOD3) mutations associated with the pathogenesis of hypertrophic cardiomyopathy (HCM) in an Irish population

Background

The genetic cause of hypertrophic cardiomyopathy (HCM) remains unexplained in a substantial proportion of cases. Recent large sequencing studies suggest that, though not previously implicated, FHOD3 (a Formin protein responsible for sarcomere assembly) may have a role in the pathogenesis of HCM, particularly variants affecting a conserved small coil-coiled domain (amino acids 622 to 655).

Aim

To investigate the relationship between novel FHOD3 mutations, previously classified as variants of uncertain significance (American College of Medical Genetics ACMG Class III), and the development of HCM. 

Methods

A single center review of HCM probands carrying mutations in the FHOD3 gene was conducted. Existing HCM patients from the family heart screening clinic database were retrospectively reviewed. Frequency of FHOD3 mutations, segregation among family members and clinical characteristics of patients were reviewed. All genetic analysis was conducted via the same internationally validated next generation sequencing lab.

Results

Of 367 HCM probands identified in our center, 9 (2.45%) were found to have ACMG Class III mutations affecting the FHOD3 gene. Five of these 9 probands (56%) displayed the same p.Arg637Gln mutation, while the remaining 4 (44%) carry the same p.Ile648Thr residue alteration. Both of these are rare mutations, found to be present in <1% of controls in previous large sequencing studies and not previously reported. Among probands with the p.Ile648Thr mutation, co-segregation was confirmed in one family, another first-degree relative in the same family having suffered a sudden cardiac death (HCM confirmed on autopsy). In those with the p.Arg367Gln mutation, a strong family history was observed in two separate families, 4 first-degree members having a confirmed HCM diagnosis. Carriers of both mutation types displayed varying degrees of disease severity with rates of non-sustained ventricular tachycardia and device implantation similar to other HCM cohorts (∼40%).

Conclusions

FHOD3 is a novel gene, recently implicated in the pathogenesis of HCM, though not previously well described in the literature. Carrier frequency of FHOD3 mutations in the HCM population in our center is similar to that described in recent publication (1-2%), and all carry variants affecting the suspected small coil-coiled domain (amino-acids 622-625).

P333Left atrial function by echocardiography is independent of degree of left atrial electrical scar

Introduction

Assessment of left atrial function via transthoracic echocardiography (TTE) is performed most commonly by measuring the transmitral A wave in sinus rhythm. Left atrial (LA) fibrosis plays an important role in the pathogenesis and perpetuation of Atrial Fibrillation (AF). It may be identified by bipolar voltage (BiV) mapping, which can easily be performed at the beginning of a Pulmonary Vein Isolation (PVI) procedure. The relationship between the degree of LA fibrosis, characterised with mapping, and LA function, determined by echocardiography, has not previously been elucidated.

Methods

Patients were enrolled in a project to evaluate the degree of fibrosis during PVI procedures. Pre-procedure TTEs of those presenting in sinus rhythm were assessed and the transmitral A wave was measured and compared to the degree of scarring seen. The high density electroanatomic maps (HD-EAMs) created during the PVIs were analysed using a novel VHA algorithm after the procedure. All points with voltages < 0.5mV were defined to have electrical scar. Patients were classified into 4 quartiles based on the levels of scar seen (Figure 1).

Results

39 patients were included in the evaluation. Average age was 60.6 +/- 13.2 years. 32 (82.0%) of the patients were male. Mean CHADS2VASc score was 1.5. The mean percentage of scar was calculated as 19.6 +/- 15.9%. The average A wave was 0.62 +/- 0.18 ms-1. Pearson’s correlation coefficient showed no relationship between LA scar and either A wave velocities (r = 0.26, p = 0.11) or E:A ratio (r=-0.02, p = 0.91). A significant correlation between A wave velocity and CHADS2VASc was observed (r = 0.49, p = 0.001).

Conclusion

Our study demonstrates no relationship between degree of LA scarring and reduced LA function on TTE as assessed by the A wave. It has been established that structural remodelling in AF (such as atrial dilatation) may occur independently of the electrical remodelling. A potential explanation for our findings is that the electrical scarring in AF, which results in alterations in refractory periods, precedes the negative remodelling which ultimately results in reduced atrial function. This hypothesis would need to be further evaluated in larger studies.

Abstract Figure 1

P338Dystrophin deficient cardiomyopathy: predictors associated with the cardiac phenotype in a Duchenne registry population - A guide for device therapy

Background

Patients with Duchenne muscular dystrophy (DMD) typically exhibit cardiac dysfunction. With increasing life expectancy due to advances in respiratory support, cardiomyopathy and associated dsyrhythmia are fast becoming the primary cause of morbidity and mortality in this patient group. Despite advances, the correlation between genotype and cardiac phenotype remains poorly understood and individual registries small, with implementation of device therapy often delayed due to poor diagnostic imaging. 

Methods and Aims: A single-center registry for DMD patients was established and data including genotyping, medical therapy and investigations such as cardiac MRI, nt-Pro BNP levels, echocardiogram were analysed. The aim was to potentially identify predictors associated with a more severe cardiac phenotype and thus help to guide provision of device therapy.  

Results

A total of 19 patients (age 17 - 31) with DMD were reviewed (demographics table 1). All patients were evaluated with echocardiography on at least one occasion (mean EF 46.5%). Cardiac MRI was attempted in 6 patients however only completed in 2 due to contractures preventing access to scanning. 11 of 19 patients (58%) demonstrated an impaired left ventricular ejection fraction (EF) <50% (mean EF 42%). Proximal "hot spot" mutations/deletions (exon 2-19) were associated with a more pronounced reduction in EF, all patients with proximal mutations demonstrating an EF < 45% (mean 41%). 5 of 6 (83%) of those with >1 exon deletion mutations demonstrated more severely impaired EF (mean EF 41%) compared to those with single exon deletions (mean EF 52%). Interestingly, one patient with a proximal mutation (exon 3-6 deletion) remains mobilising to distances of 70 meters, however cardiac MRI revealed a moderate degree of fibrosis with an EF of 43%. Correlation between nt-Pro BNP levels with reduced EF was not uniform, however a level < 100 was associated with an EF >55% in 89% of patients studied. of those on steroid regimes, 6 (54%) had impaired LVEF compared to 5 (83%) of those not on steroid therapy. All patients were on at least one class of heart failure modification, with 79% on two and 37% on three agents. Only one patient in the registry has had an ICD implanted. He has had a device for 10 years in and in this time there have been no therapies delivered however runs of non-sustained ventricular tachycardia have been noted. 

Conclusions

Correlation between predictors and cardiac phenotype in a Duchenne population remains unreliable. Location and size of exon alteration appears to be indicative of more markedly impaired LV function, however larger studies are required to characterise this further and challenges remain with regard to accurate assessment of EF. The use of predictors in future may help to guide appropriate provision of device therapy.

1269The SADS heart of the matter: a review of the sudden arrhythmic death syndrome (SADS) biobank - the cornerstone of a national strategy

Background

Sudden cardiac death (SCD) in the young (age 1-35) is commonly attributed to structural and arrhythmogenic syndromes, for which there is often an underlying genetic basis. Expert recommendation emphasises the importance of genetic testing in such cases, however to date this remains the first and only national programme in Europe to facilitate this. 

Aim

 To review detection rates of genetic variants in samples tested via the SADS BioBank and possibly demonstrate the merits of this novel resource for primary prevention for family members.

Methods

 Family screening and consent for genetic testing was carried out in the Family Heart Screening Clinic. Result analysis of samples sent for molecular autopsy via the BioBank from its induction in January 2015 was performed. Genetic analysis was conducted via the same internationally accredited next generation sequencing lab.

Results

 From January 2015 to July 2019, 161 samples had been stored in the SADS BioBank following confirmed SADS death on autopsy; 33% female and 67% male. Of these, 24 (14.9%) samples were sent for genetic testing: 21 for a 380 gene molecular autopsy and 3 for a targeted hypertrophic cardiomyopathy panel (173 genes). Of 24 samples tested, 10 (42%) yielded positive genetic variants: 4 American College of Medical Genetics (ACMG) Class IV or V mutations considered pathogenic, and 6 ACMG class III variants of uncertain significance (VUS). Familial cascade screening following confirmed pathogenic mutations resulted in detection of 3 (33.3%) positive genotypes in 9 first-degree relatives. Screening of relatives of Class III positive probands resulted in diagnosis of an Inherited Cardiac Condition (ICC) in 25% of first-degree relatives. 8.2% of first-degree relatives of probands with negative gene testing were given an ICC diagnosis following clinical screening.

Conclusions

 This short study demonstrates the unique potential the SADS BioBank has to offer in terms of identifying those most at risk and optimising prevention strategies for relatives, thus highlighting the role for such a resource in terms of preventative screening in the future.

Pathogenic Variant (ACMG Class IV & V) Variant of Uncertain Significance(ACMG Class III) No Gene Variant Identified Number Detected (n = 24) 4 6 14 1st Degree Relatives Screened (n = 86) 17 20 49 2nd Degree Relatives Screened (n = 46) 4 23 19 Genotype Detected (n = 4) 3 1 0 Phenotype Detected (n = 10) 1 5 4 Breakdown of clinical and genetic results of family screening by ACMG class.

Abstract Figure.

Internal Delensing of Cosmic Microwave Background Polarization B-Modes with the POLARBEAR Experiment

Using only cosmic microwave background polarization data from the polarbear experiment, we measure B-mode polarization delensing on subdegree scales at more than 5σ significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a means of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments.

[Efficacy of topical 0.3% ciprofloxacin application in reducing the conjunctival biota of patients undergoing cataract extraction]

OBJECTIVE

To determine the efficacy of topical 0.3% ciprofloxacin in reducing conjunctival biota in patients undergoing cataract surgery.

PATIENTS AND METHODS

Experimental, prospective, randomized, controlled and single-blind study. Forty-six eyes of 46 patients were randomized into 2 groups, the study group (n=23) received topical 0.3% ciprofloxacin one day before surgery for six times, and on the day of the surgery one drop every 15minutes starting one hour before surgery until 3 doses were completed. The control group (n=23) did not receive any antibiotics. For both groups for the surgical field 10% povidone-iodine was applied. Samples from the conjunctiva were taken at four different times and then cultured on solid media (chocolate agar, blood agar) and enrichment broth (thioglycolate). The aqueous humor samples were also cultured in thioglycolate. The presence of bacteria was identified quantitatively and qualitatively, and the frequency of contamination was measured by considering the presence of bacteria in liquid and solid culture media. The number of colony forming units (CFU) was counted in the solid culture medium.

RESULTS

Positive cultures were obtained in 82.6% and 78.2% of the patients in the study and control groups, respectively, before the administration of 0.3% ciprofloxacin. The administration of 0.3% ciprofloxacin significantly reduced the CFU compared to the control group (P<.05). Immediately after the use of povidone-iodine, the proportion of patients with a positive culture decreased to 21.7% in the study group, and 8.7% in the control group. At the end of the surgery, this percentage was 26% and 30.4%, respectively. The most common isolated pathogen was negative-coagulase Staphylococcus (66.7%).

CONCLUSION

The administration of 0.3% ciprofloxacin reduces conjunctival bacterial load in the preoperative period. However, it was unable to eradicate the bacteria completely. The administration of povidone-iodine reduced conjunctival biota in 50%-70% of patients undergoing cataract surgery.

Ontogenetic development of mRNA levels and binding sites of hepatic beta-adrenergic receptors in cattle

Catecholamines regulate glucose metabolism and affect hepatic glucose production mainly through beta2-adrenergic receptors. The hypothesis was tested that gene expression and numbers of hepatic beta-adrenergic receptors in calves are influenced by age. Examined developmental stages included pre-term (P0) and full-term (F0) calves immediately after birth, full-term calves on day 5 of life (F5), and veal calves (VC) at the age of 159 days. Expression of beta1-, beta2-, and beta3-adrenergic receptor mRNA was measured by real-time PCR. Receptor binding was quantified by saturation binding assays using (3H)-CGP-12177 as a ligand. Abundance of mRNA differed among beta-adrenergic subtypes (beta2 > beta1 > beta3; P < 0.01). Beta3-adrenergic receptor mRNA was undetectable in VC. mRNA abundance for beta2-adrenergic receptors was higher (P < 0.05) in VC than P0 and for beta3-adrenergic receptors was higher (P < 0.001) in F5 than P0. Binding studies revealed most binding of (3H)-CGP-12177 to beta2-adrenergic receptors, which were highest in VC (P < 0.001) and higher (P < 0.05) in F5 than P0. Binding sites correlated positively with mRNA levels of beta2-adrenergic receptors (r = 0.67; P < 0.001), with hepatic activities of phosphoenolpyruvate kinase (r = 0.73; P < 0.001) and with pyruvate kinase (r = 0.4; P < 0.05), and with plasma glucose concentrations (r = 0.5; P < 0.01). In conclusion, mRNA of all three beta-adrenergic receptor subtypes were found in liver, with beta2-adrenergic receptors being the dominant subtype. Numbers of beta2-adrenergic receptors increased with age and were mainly regulated at the transcriptional level. Numbers of beta-adrenergic receptors were positively associated with hepatic activities of gluconeogenetic enzymes and with plasma glucose levels, suggesting functional importance.

Effects of dexamethasone and colostrum feeding on mRNA levels and binding capacities of beta-adrenergic receptors in the liver of neonatal calves

Glucocorticoids increase plasma glucose concentrations in neonatal calves, but not hepatic gluconeogenic enzyme mRNA levels and activities. Catecholamines, too, enhance plasma glucose levels and regulate hepatic glucose metabolism. We have measured hepatic mRNA levels of beta-adrenergic receptors and beta-adrenergic receptor binding in neonatal calves on day 5 of life. Calves were fed either colostrums (C) or an isoenergetic milk-based formula (F), and in each feeding group, half of the calves were treated with dexamethasone (DEXA; 30 microg/(kg body weightday)). Abundance of mRNA was highest (P < 0.01) for beta2-adrenergic receptors and was higher (P < 0.01) for beta1- than for beta3-adrenergic receptors. DEXA treatment decreased (P < 0.05) beta1- and beta2-adrenergic receptor mRNA levels. Beta3-adrenergic receptor mRNA levels were higher (P < 0.05) in colostrum- than in formula-fed calves. Competitive binding revealed highest affinities for alprenolol, propranolol (both beta1- and beta2-antagonists), and ICI-188,551 (beta2-antagonist), which did not significantly differ from each other. Atenolol (beta1-antagonist) up to 10(-5) M did not displace (3H)-CGP-12177 from receptors. Competitive binding for adrenaline was best fitted by a two-receptor model. DEXA decreased (P < 0.05) (3H)-CGP-12177 binding capacities, whereas binding affinity of (3H)-CGP-12177 was not affected by DEXA or different feeding. Binding sites correlated positively with mRNA levels of beta2-adrenergic receptors (r = 0.56; P < 0.01). In conclusion, beta2-adrenergic receptors were the dominant subtype in the hepatic tissue. Feeding did not significantly affect beta2-adrenergic binding sites. However, DEXA decreased beta2-adrenergic binding sites and this was regulated at the transcriptional level.

Recent advances in ultratrace analysis of dioxins and related halogenated hydrocarbons

Analytical methodology for polychlorinated dioxins and furans (PCDDs and PCDFs) in environmental samples is not standardized. Many variations exist for the extraction, cleanup, quantitation, and confirmation of these compounds and reported detection limits and recoveries vary over several orders of magnitude. This paper describes research carried out at the Canada Centre for Inland Waters over the past seven or eight years to develop reliable methodology at ultratrace levels (10−12–10−15 g/g) applicable to a wide range of environmental samples. Extraction techniques are described for biological tissue (fish, clams, leaches, eggs), fly ash, sediments, and water. Detailed cleanup procedures for the various matrices consist of most or all of the following: gel permeation chromatography liquid/liquid extraction with Na3PO4, liquid/liquid extraction with H2SO4, basic alumina chromatography, and carbon fibre chromatography. Preliminary screening of the cleaned extracts is achieved by gas chromatography equipped with a mass selective detector and positive identification by gas chromatography/mass spectrometry operated in electron impact and chemical ionization modes and with full scan and multiple ion detection. Custom software permitting the analysis of a wide range of compounds in a single run by gc/ms is reported. The presence of specific isomers of PCDDs and PCDFs is confirmed by high resolution gas chromatography/mass spectrometry. A radioimmunoassay screening procedure for PCDDs in environmental samples is also described.

The relative sensitivity of peripheral blood T-lymphocyte colony forming cells and bone marrow CFU-GM to deoxyadenosine and 2'deoxycoformycin

The effects of the nucleoside deoxyadenosine (AdR) towards 2'deoxycoformycin (dCF) treated peripheral blood T-lymphocyte and bone marrow myeloid progenitor cells has been studied. Mononuclear cell preparations were exposed to dCF and AdR in suspension culture prior to washing and culture in a medium free of exogenous nucleosides. The combination of dCF and AdR was found to be highly toxic to peripheral blood T lymphocyte colony forming cells (CFU-TL) following prolonged (18 h) incubation. CFU-GM were markedly less sensitive to the combination of dCF and AdR, concentrations of dCF (10(-5) M) and AdR (10(-5) M) which produced an almost total inhibition of CFU-TL only inhibited CFU-GM by a mean of 10%.