Sudden death associated with a novel H401Q PRKAG2 mutation

Genetic variants in Colombian patients with inherited cardiac conditions

BACKGROUND

Clinical and molecular diagnosis of inherited cardiac conditions is key to find at-risk subjects and avoid preventable deaths. This study aimed to identify genetic variants in a sample of Colombian patients diagnosed with inherited cardiac conditions.

METHODS

Next-generation sequencing (Illumina platform) using a 231 gene panel was performed in blood samples of 25 unrelated patients with age disease onset between 9 and 55 years.

RESULTS

Genetic testing yield was 52%. Two novel likely pathogenic/ pathogenic variants were found: a DSP nonsense variant in a patient with arrhythmogenic cardiomyopathy and a KCNE1 frameshift variant in two patients with long QT syndrome. Younger individuals (<18 years) had the highest genetic testing yield (66.6%) compared to 50% and 20% in young adults and patients over 40 years, respectively. All subjects affected with long QT syndrome with a severe event while exercising had a positive genetic test. They also had four times more loss of consciousness events and, resuscitated sudden cardiac arrest was more representative.

CONCLUSION

This study is the first one undertaken in Colombia to evaluate inherited cardiac conditions. It highlights the need to perform mutational analysis to provide adequate genetic counseling and to be able to identify patients at risk of severe events.

Glycogen storage cardiomyopathy (PRKAG2): diagnostic findings of standard and advanced echocardiography techniques

AIMS

Describe the findings obtained using standard echocardiography (Echo) and deformation indices (2D and 3D speckle tracking strain) in patients (Pts) with PRKAG2 cardiomyopathy. Seek to identify any peculiar characteristics and possible strain patterns that may distinguish this condition from other causes of left ventricular hypertrophy (LVH).

METHODS AND RESULTS

Thirty Pts with genetically proven PRKAG2 (R302Q and H401Q), 16 (53.3%) male, mean age 39.1± 15.4 years old, were examined using standard, speckle tracking (STE), and 3D Echo. Pacemaker (PM) had been implanted in 12 (40%) Pts with a mean age of 38.1 ± 13 years. Hypertrophy was found in varying degrees in 18 (86%) Pts. Seven Pts (24%) presented 3D ejection fraction (EF) below normal limits. Diastolic function was abnormal in 17 (63%) Pts. Global longitudinal strain (GLS) on 2D measured -16.4% ± 5.3%. GLS measured -13.2% ± 4.8%, global radial strain 40.8% ± 13.8%, global circumferential strain (GCS) -16.1% ± 4.4%, and global area strain -26.1% ± 6.7% by 3D Echo offline analyses. Pts with PM presented lower EF and GCS compared with those without PM. EF/GLS measured 3.65 ± 1.00. In the bull's eye map, a strain pattern similar to stripes in 18 (60%) Pts was identified, which might be a differentiating signal among LVH.

CONCLUSION

Echocardiography is a valuable tool in detecting diffuse and focal myocardial abnormalities in PRKAG2 cardiomyopathy. The deformation indices are especially revealing because they may help distinguish this rare infiltrative disease, thereby favouring early diagnosis, enhanced treatment, and improved outcome.

Identification, clinical manifestation and structural mechanisms of mutations in AMPK associated cardiac glycogen storage disease

Background

Although 21 causative mutations have been associated with PRKAG2 syndrome, our understanding of the syndrome remains incomplete. The aim of this project is to further investigate its unique genetic background, clinical manifestations, and underlying structural changes.

Methods

We recruited 885 hypertrophic cardiomyopathy (HCM) probands and their families internationally. Targeted next-generation sequencing of sudden cardiac death (SCD) genes was performed. The role of the identified variants was assessed using histological techniques and computational modeling.

Findings

Twelve PRKAG2 syndrome kindreds harboring 5 distinct variants were identified. The clinical penetrance of 25 carriers was 100.0%. Twenty-two family members died of SCD or heart failure (HF). All probands developed bradycardia (HRmin, 36.3 ± 9.8 bpm) and cardiac conduction defects, and 33% had evidence of atrial fibrillation/paroxysmal supraventricular tachycardia (PSVT) and 67% had ventricular preexcitation, respectively. Some carriers presented with apical hypertrophy, hypertension, hyperlipidemia, and renal insufficiency. Histological study revealed reduced AMPK activity and major cardiac channels in the heart tissue with K485E mutation. Computational modelling suggests that K485E disrupts the salt bridge connecting the β and γ subunits of AMPK, R302Q/P decreases the binding affinity for ATP, T400N and H401D alter the orientation of H383 and R531 residues, thus altering nucleotide binding, and N488I and L341S lead to structural instability in the Bateman domain, which disrupts the intramolecular regulation.

Interpretation

Including 4 families with 3 new mutations, we describe a cohort of 12 kindreds with PRKAG2 syndrome with novel pathogenic mechanisms by computational modelling. Severe clinical cardiac phenotypes may be developed, including HF, requiring close follow-up.