Genetic testing in the management of inherited cardiac disorders: two cases of Filamin-C arrhythmogenic left ventricular cardiomyopathy

Background

Arrhythmogenic left ventricular cardiomyopathy (ALVC) is a left ventricle-dominant arrhythmogenic cardiomyopathy (ACM) subtype often associated with malignant ventricular arrhythmias, left ventricular (LV) scar and sudden cardiac death. Awareness about LV involvement is now on the rise. The diagnosis relies on structural abnormalities on cardiac magnetic resonance (CMR) imaging and known ACM-causing genetic mutations.

Case summary

A 28-year-old lady (Case 1) was referred for cardiac screening after her father passed away suddenly. Her paternal uncle (Case 2) had been diagnosed with supposed dilated cardiomyopathy prior to referral. Both cases were worked up extensively with an electrocardiogram (ECG), 24-h ambulatory ECG monitor, exercise testing, and CMR imaging. Investigations of Case 1 showed T-wave inversion in the infero-lateral leads and a ventricular ectopic burden of 3% on ambulatory monitoring. Cardiac magnetic resonance imaging revealed moderately reduced LV systolic function (ejection fraction of 40%) with circumferential macroscopic fibrosis. Her uncle (Case 2) also had an impaired and dilated ventricle with extensive scar on CMR. Following the recent introduction of a cardiogenetic service in our unit, both were heterozygous for a pathogenic Filamin-C variant (c.7384+1G>A). Based on CMR findings and genetic results, the diagnosis of both patients was deemed to be ALVC. After years of surveillance, Patient 1 now has an implantable cardioverter defibrillator (ICD) indication.

Discussion

The importance of diagnosing patients with ACM lies in the predisposition to sudden cardiac death. Gene-specific treatment algorithms in ACM may alter management strategies, including ICD implantation as primary prevention. An in-depth multidisciplinary discussion and respecting patient autonomy are key factors in any decision pertaining to ICD implantation.

BEAT-IT: A de-novo cardiac screening programme in Maltese adolescents

AIMS

Sudden cardiac death (SCD) in young individuals is often unexpected, provoking substantial emotional stress for family and friends of the deceased. Cardiac screening may identify individuals who harbour disorders linked to SCD. The feasibility and diagnostic yield of a nationwide cardiac screening programme in adolescents has never been explored.

METHODS

All individuals eligible for cardiac screening (students aged 15 years) were systematically invited to enrol. Students were provided with a health questionnaire. ECGs were acquired at school. A physician led consultation was carried out on site. Participants with an abnormal screen were then referred for secondary evaluation to the nation's tertiary centre. Feasibility criteria included a) participation rate >60%, b) adherence to secondary evaluation >80%, and c) cost per individual screened equating to <€100. The diagnostic yield was also evaluated.

RESULTS

At the end of enrolment, 2708 students gave consent (mean 15 years, 50.4% male), equating to 67.9% of the eligible cohort. Overall, 109 participants (4.0%) were referred for further evaluation. An abnormal electrocardiogram (ECG) was the most common reason for referral (3.7%). Fifteen individuals (0.6%) were diagnosed with a cardiac condition. Nine (0.3%) had a condition linked to SCD (n = 1 Long-QT syndrome, n = 1 Hypertrophic Cardiomyopathy, n = 5 Wolff-Parkinson White, n = 2 coronary anomalies). The yield was similar in athletes and non-athletes (p = 0.324). The cost per cardiac individual screened equated to €51.15.

CONCLUSION

A nationwide systematic cardiac screening programme for adolescent athletes and non-athletes is feasible and cost-efficient, provided that responsible centres have the appropriate infrastructure.

The juvenile ECG pattern in adolescent athletes and non-athletes in a national cardiac screening program (BEAT-IT)

BACKGROUND

Anterior T wave inversion (TWI) is frequent in healthy adolescent individuals (juvenile ECG pattern), normalising after puberty. Its clinical implications are uncertain.

AIM

This study assessed a) national prevalence of anterior TWI, b) ST segment morphology, c) proportion of individuals with a juvenile ECG pattern whose ECG normalises and d) factors predicting TWI persistence >16 years.

METHODS

Adolescents (mean 15y) in Malta were systematically invited to enrol in a cardiac screening program. Subjects completed a health questionnaire and an ECG at their school. Participants with TWI were labelled as TWI in V₁-V₂ or extended TWI (V₁-V₃/₄). The latter were followed at 1 year with a repeat ECG. Those with persistent extended anterior TWI were offered evaluation and surveillance.

RESULTS

The prevalence of isolated anterior TWI was 5.0%, commoner in females (6.3%) independent of athletic ability. Extended TWI was commoner in female athletes (4.2%, non-athletes 2.1%). Females often had shallow TWI without overt ST segment abnormalities. Deep TWI and ST segment changes were more frequent in males. Only 0.2% of cases persisted ≥16 years of age. ST segment characteristics were not able to predict T wave normalisation. No events took place during follow up (40 ± 9 months).

CONCLUSION

Anterior TWI is a frequent phenomenon in adolescents, especially in females. Female athletes are also more likely to have extended anterior TWI. Only 0.2% of cases have persistent anterior TWI at 16 years of age. Chest wall anatomy may explain this phenomenon in females. It is uncommon in males, hence why surveillance is more prudent.

Clinical Features and Natural History of Preadolescent Nonsyndromic Hypertrophic Cardiomyopathy

BACKGROUND

Up to one-half of childhood sarcomeric hypertrophic cardiomyopathy (HCM) presents before the age of 12 years, but this patient group has not been systematically characterized.

OBJECTIVES

The aim of this study was to describe the clinical presentation and natural history of patients presenting with nonsyndromic HCM before the age of 12 years.

METHODS

Data from the International Paediatric Hypertrophic Cardiomyopathy Consortium on 639 children diagnosed with HCM younger than 12 years were collected and compared with those from 568 children diagnosed between 12 and 16 years.

RESULTS

At baseline, 339 patients (53.6%) had family histories of HCM, 132 (20.9%) had heart failure symptoms, and 250 (39.2%) were prescribed cardiac medications. The median maximal left ventricular wall thickness z-score was 8.7 (IQR: 5.3-14.4), and 145 patients (27.2%) had left ventricular outflow tract obstruction. Over a median follow-up period of 5.6 years (IQR: 2.3-10.0 years), 42 patients (6.6%) died, 21 (3.3%) underwent cardiac transplantation, and 69 (10.8%) had life-threatening arrhythmic events. Compared with those presenting after 12 years, a higher proportion of younger patients underwent myectomy (10.5% vs 7.2%; P = 0.045), but fewer received primary prevention implantable cardioverter-defibrillators (18.9% vs 30.1%; P = 0.041). The incidence of mortality or life-threatening arrhythmic events did not differ, but events occurred at a younger age.

CONCLUSIONS

Early-onset childhood HCM is associated with a comparable symptom burden and cardiac phenotype as in patients presenting later in childhood. Long-term outcomes including mortality did not differ by age of presentation, but patients presenting at younger than 12 years experienced adverse events at younger ages.

Relationship Between Maximal Left Ventricular Wall Thickness and Sudden Cardiac Death in Childhood Onset Hypertrophic Cardiomyopathy

BACKGROUND

Maximal left ventricular wall thickness (MLVWT) is a risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). In adults, the severity of left ventricular hypertrophy has a nonlinear relationship with SCD, but it is not known whether the same complex relationship is seen in childhood. The aim of this study was to describe the relationship between left ventricular hypertrophy and SCD risk in a large international pediatric HCM cohort.

METHODS

The study cohort comprised 1075 children (mean age, 10.2 years [±4.4]) diagnosed with HCM (1-16 years) from the International Paediatric Hypertrophic Cardiomyopathy Consortium. Anonymized, noninvasive clinical data were collected from baseline evaluation and follow-up, and 5-year estimated SCD risk was calculated (HCM Risk-Kids).

RESULTS

MLVWT Z score was <10 in 598 (58.1%), ≥10 to <20 in 334 (31.1%), and ≥20 in 143 (13.3%). Higher MLVWT Z scores were associated with heart failure symptoms, unexplained syncope, left ventricular outflow tract obstruction, left atrial dilatation, and nonsustained ventricular tachycardia. One hundred twenty-two patients (71.3%) with MLVWT Z score ≥20 had coexisting risk factors for SCD. Over a median follow-up of 4.9 years (interquartile range, 2.3-9.3), 115 (10.7%) had an SCD event. Freedom from SCD event at 5 years for those with MLVWT Z scores <10, ≥10 to <20, and ≥20 was 95.6%, 87.4%, and 86.0, respectively. The estimated SCD risk at 5 years had a nonlinear, inverted U-shaped relationship with MLVWT Z score, peaking at Z score +23. The presence of coexisting risk factors had a summative effect on risk.

CONCLUSIONS

In children with HCM, an inverted U-shaped relationship exists between left ventricular hypertrophy and estimated SCD risk. The presence of additional risk factors has a summative effect on risk. While MLVWT is important for risk stratification, it should not be used either as a binary variable or in isolation to guide implantable cardioverter defibrillator implantation decisions in children with HCM.

Yield from family screening in a national adolescent cardiac screening program

Introduction

Cascade family screening in patients with confirmed or suspected inherited cardiac disorders is now well established. This may refute or confirm a familial clinical diagnosis and is particularly relevant in young adolescent individuals as it may be too early to manifest a distinct phenotype.

Objectives

A large cohort of 2708 adolescents aged 14–16 years gave consent to participate in a national cardiac screening program (BEAT-IT). Individuals with suspected inherited cardiac disorders were extensively evaluated. Their relatives were also invited to undergo screening. This study reports the yield of this family cardiac screening program.

Methodology

Family members of probands with suspected or confirmed inherited cardiac conditions were offered cardiac screening. A standard clinical screening protocol for all first-degree family members included a resting 12-lead ECG and echocardiogram. Those with a channelopathy suspicion also underwent postural ECGs and exercise testing. Screening second-degree relatives was also performed in a cascade fashion when clinically indicated. Relatives with a normal baseline screen were offered surveillance if younger than 25 years or a proband clinical diagnosis. Those with an abnormal ECG and/or echocardiogram were referred for further evaluation.

Results

17 probands (63% females) were suspected of harbouring inherited heart disease. Another 2 were diagnosed with a clinical phenotype. The mean age was 15.3±0.58 years. All were Caucasian.

77 family members underwent cardiac screening, with a mean age of 42.5±16.43 at first evaluation. The majority were female (n=44, 57.1%). 12 (15.6%) had an abnormal ECG. 6 (7.8%) had an abnormal echocardiogram, with 2 (2.6%) consistent with cardiomyopathy. 8 (10.4%) were diagnosed with an inherited cardiac condition (n=2 HCM, n=1 DCM, n=5 LQTS). Another 7 (9.1%) are under surveillance because of a pathological ECG in the absence of a clinical phenotype.

The highest clinical yield was in the Long QT group (n=5, 55.6%). Family members (n=25) referred because of proband lateral TWI were the second most likely to require clinical follow-up because of a pathological ECG or a clinical diagnosis (n=7, 28.0%). Relatives referred because of isolated anterior TWI on the proband's ECG had the lowest diagnostic yield (n=17, 0%). After excluding families of probands with isolated anterior TWI (n=18), the overall clinical yield increased to 13.6%. Another 11.9% are under surveillance because of a pathological ECG.

Conclusion

The yield of family screening as part of a national cardiac screening program was 10.4%. This increases to 13.6% when excluding probands with anterior TWI, with 11.9% under surveillance because of a pathological ECG. To our knowledge, this is the first such study of its kind.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Beating Hearts MaltaResearch, Innovation and Development Trust (University of Malta)

The prevalence of short PR interval in adolescent athletes and non-athletes

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Malta Heart Foundation and Beating Hearts

Background

Little is known about the prevalence and clinical relevance of an isolated short PR interval in young individuals.

Objectives

To explore the PR interval in adolescent athletes and non-athletes and determine possible association with sex, age, ethnicity, athletic ability and sporting discipline.

Methods

Between 2017-2018, school children aged 14-17 years were invited to participate in a National cardiac screening programme comprised of a health questionnaire and a resting 12-lead ECG. An athlete was defined as an individual participating in &gt;4 hours/week of organised sports. Sport disciplines were categorised as skill, power, mixed and endurance. A short PR interval was defined as &lt;120ms.

Results

A total of 1619 (61.0%) non-athletes and 1036 (39.0%) athletes  (median age 15 years, 50.5% females, 93.0% Caucasian) participated in the screening program. Most athletes participated in mixed sports (62.2%).

The mean PR interval was shorter in non-athletes compared to athletes (136.65 ± 19.00ms vs 139.93 ± 19.86ms p &lt; 0.001) and in females compared to males (135.98 ± 18.39ms vs 139.93 ± 20.20ms, p &lt; 0.001). An isolated short PR interval was present in 405 (15.3%) individuals. Associated pre-excitation was present in an additional 5 cases (0.2%). A short PR interval was commoner in females (18.7% vs 11.7%, p &lt; 0.001) and in non-athletes (16.6% vs 13.2%, p = 0.020). Age (p = 0.657) and ethnicity (p = 0.115) did not influence the presence of a short PR interval.

The presence of a short PR interval in adolescent athletes was independent of the sporting discipline category (p = 0.071), in both males (p = 0.400) and females (p = 0.233).  The absolute PR interval did not differ significantly between sporting categories (p = 0.065),  in both genders (males, p = 0.202, females, p = 0.279).

Symptoms that were suggestive of arrhythmias were present in similar proportions of individuals with short and normal PR intervals (18.8% vs 17.1%, p = 0.393). 

Conclusion

An isolated short PR interval was a frequent finding in this cohort, with a predilection for females and non-athletes. The high frequency of short PR in young individuals suggests that in the absence of pre-excitation or symptoms, further evaluation is not warranted. Long-term follow-up studies may further elucidate the clinical relevance of this phenomenon.

Usual or unusual presentations of Dirofilaria repens in two sibling dogs: a case report

This study describes two different manifestations of Dirofilaria repens infection in sibling dogs with microfilaremia. Dog 1, asymptomatic, harbored a gravid female of D. repens on the parietal layer of tunica vaginalis of one testicle and showed a marked circulating eosinophilia (3.3·103/μL). Both testicles were normal in shape and size without any gross lesions. Dog 2 had a pyotraumatic dermatitis. The cases were confirmed by PCR and sequencing. The sequences obtained showed 100% identity with those of D. repens isolated from human scrotum in Croatia. The treatment with moxidectin 2.5% and imidacloprid 10%/kg was effective in eliminating microfilariae after just one application, as demonstrated by negative modified Knott's tests and PCR analyses of blood samples. This status was maintained during the post-treatment observation period. The classical localization of D. repens in dogs is in subcutaneous tissues, within nodules or free; however, it can also occur with some frequency in testicles, as described in humans. The infection can be associated with circulating eosinophilia or pyotraumatic dermatitis, as reported in this study. Thus, in endemic areas, it is advisable to carefully inspect the removed testicles at neutering since parasite localization can take place without any macroscopic changes. Moreover, in the case of circulating eosinophilia or pyotraumatic dermatitis, investigations should include modified Knott's test and PCR to ensure that D. repens is not the cause of these alterations. Rapid and sensitive tests for the early detection of infected animals would help to prevent or limit the spread of this zoonosis.

An Unexpected Case of Isolated Left Ventricular Apical Hypoplasia in an Asymptomatic Patient

Isolated left ventricular (LV) apical hypoplasia is a rare type of congenital heart disease. It is often asymptomatic in childhood but may lead to complications later on in life. The proposed mechanism is inadequate LV dilatation during development of the primitive ventricle, resulting in a spherical LV. To our knowledge, we describe for the first time a case of isolated LV apical hypoplasia in an asymptomatic patient, diagnosed on investigation of an abnormal 12-lead resting electrocardiogram (ECG).

Development of a Novel Risk Prediction Model for Sudden Cardiac Death in Childhood Hypertrophic Cardiomyopathy (HCM Risk-Kids)

Importance

Sudden cardiac death (SCD) is the most common mode of death in childhood hypertrophic cardiomyopathy (HCM), but there is no validated algorithm to identify those at highest risk.

Objective

To develop and validate an SCD risk prediction model that provides individualized risk estimates.

Design, Setting, and Participants

A prognostic model was developed from a retrospective, multicenter, longitudinal cohort study of 1024 consecutively evaluated patients aged 16 years or younger with HCM. The study was conducted from January 1, 1970, to December 31, 2017.

Exposures

The model was developed using preselected predictor variables (unexplained syncope, maximal left-ventricular wall thickness, left atrial diameter, left-ventricular outflow tract gradient, and nonsustained ventricular tachycardia) identified from the literature and internally validated using bootstrapping.

Main Outcomes and Measures

A composite outcome of SCD or an equivalent event (aborted cardiac arrest, appropriate implantable cardioverter defibrillator therapy, or sustained ventricular tachycardia associated with hemodynamic compromise).

Results

Of the 1024 patients included in the study, 699 were boys (68.3%); mean (interquartile range [IQR]) age was 11 (7-14) years. Over a median follow-up of 5.3 years (IQR, 2.6-8.3; total patient years, 5984), 89 patients (8.7%) died suddenly or had an equivalent event (annual event rate, 1.49; 95% CI, 1.15-1.92). The pediatric model was developed using preselected variables to predict the risk of SCD. The model's ability to predict risk at 5 years was validated; the C statistic was 0.69 (95% CI, 0.66-0.72), and the calibration slope was 0.98 (95% CI, 0.59-1.38). For every 10 implantable cardioverter defibrillators implanted in patients with 6% or more of a 5-year SCD risk, 1 patient may potentially be saved from SCD at 5 years.

Conclusions and Relevance

This new, validated risk stratification model for SCD in childhood HCM may provide individualized estimates of risk at 5 years using readily obtained clinical risk factors. External validation studies are required to demonstrate the accuracy of this model's predictions in diverse patient populations.

Pompe disease, a storage cardiomyopathy

Pompe disease also known as glycogen storage disease type II, is a rare and progressive lysosomal storage disorder caused by the deficiency of the enzyme acid α-glucosidase. This results in the accumulation of glycogen in various tissues particularly involving the heart, skeletal muscle and liver. It is inherited in an autosomal recessive manner due to mutations in the GAA gene. There are several known pathogenic variants, some of which are particularly common in certain geographical regions. Pompe disease is a single disease exhibiting a heterogeneous clinical spectrum depending on the extent of enzyme deficiency, the age of onset, the progression of the disease and the degree of organ involvement. It may lead to muscle weakness, hypotonia, respiratory compromise and premature death. Pompe disease is classically divided into two forms, infantile and late-onset disease. The infantile form is further subdivided into classical and non-classical subtypes. Cardiac involvement is particularly seen in the infantile phenotype of the condition, presenting as severe cardiomyopathy associated with conduction abnormalities. Enzyme replacement therapy with recombinant human acid α-glucosidase is the approved treatment option for patients with this metabolic condition. Further research is currently being done to explore more treatment options. One must keep in mind other metabolic and mitochondrial conditions, which may give a similar cardiac and neurological clinical picture.