Familial atrial standstill caused by amyloidosis

Novel pathogenic variant in LMNA gene identified in a six-generation family causing atrial cardiomyopathy and associated right atrial conduction arrhythmias

Objective

To characterize the cardiac phenotype associated with the novel pathogenic variant (c.1526del) of LMNA gene, which we identified in a large, six-generation family.

Methods and Results

A family tree was constructed. The clinical data of living and deceased family members were collected. DNA samples from 7 family members were analyzed for LMNA mutations using whole-exome high-throughput sequencing technology. The clinical presentation of pathogenic variant carriers was evaluated. In this six-generation family (n = 67), one member experienced sudden death at the age of 40-years-old. Three pathogenic variant carriers were identified to possess a novel heterozygous deletion mutation in LMNA gene (HGVS: NM_170707.4, c.1526del) located at exon 9 of LMNA chr1:156137145, which creates a premature translational stop signal (p.Pro509Leufs*39) in the LMNA gene and results in an mutant lamin A protein product. The main symptoms of the pathogenic variant carriers were palpitation, fatigue, and syncope, which typically occurred around 20-years-old. AV-conduction block and non-sustained ventricular tachycardia were the first signs of disease and would rapidly progress to atrial standstill around 30-years-old. Significant right atrial enlargement and bicuspid aortic valve malformation was also commonly seen in patients who carried this pathogenic variant.

Conclusion

The pathogenic variant of c.1526del p.P509Lfs*39 was a frameshift deletion located at exon 9 of LMNA chr1:156137145 and causes severe right atrial enlargement, sick sinus syndrome, atrial standstill, ventricular tachycardia, and bicuspid aortic valve malformation. Our findings expand the phenotypic spectrum of novel LMNA gene mutations.

Atrial remodeling and metabolic dysfunction in idiopathic isolated fibrotic atrial cardiomyopathy

BACKGROUND

Idiopathic isolated fibrotic atrial cardiomyopathy (IIF-ACM) is a novel subtype of cardiomyopathy characterized by atrial fibrosis that does not involve the ventricular myocardium and is associated with significant atrial tachyarrhythmia. The mechanisms underlying its pathogenesis are unknown.

METHODS

Atrium samples were obtained from 3 patients with IIF-ACM via surgical intervention. Control samples were consisted of 3 atrium biopsies from patients with congenital heart disease and normal sinus rhythm, matched for gender, age and basic clinical characteristics. Comparative histology, immunofluorescence staining, electron microscopy and proteomics analyses were carried out to explore the unique pathogenesis of IIF-ACM.

RESULTS

IIF-ACM atria displayed disordered myofibrils, profound fibrosis and mitochondrial damages compared to the control atria. Proteomics profiling identified metabolic pathways as the most profound changes in IIF-ACM.

CONCLUSIONS

Our study suggested that metabolic changes in the atrial myocardium caused mitochondrial oxidative stress and potential cell damage, which further led to atrial fibrosis and myofibril disorganization, the characteristic phenotype of IIF-ACM.

Persistent atrial standstill following the Cox-maze III procedure: reversal with sustained atrial pacing

Atrial standstill is a rare disorder of cardiac rhythm that is characterized by total absence of electrical activity in one or both atria. We report herein the case of a patient with atrial fibrillation and symptomatic 4.0 s pauses who received a ventricular demand pacemaker. The patient later underwent mitral valve replacement with a pericardial tissue valve and the Cox-maze III procedure for symptomatic mitral stenosis and atrial fibrillation. Following surgery, he developed atrial standstill and became pacemaker dependent. The pacemaker was later revised to an atrioventricular sequential pacemaker. Twelve hours after revision, atrioventricular sequential pacing was noted and mechanical function of the atria was confirmed by Doppler echocardiography.

Autosomal recessive atrial dilated cardiomyopathy with standstill evolution associated with mutation of Natriuretic Peptide Precursor A

BACKGROUND

Atrial dilatation and atrial standstill are etiologically heterogeneous phenotypes with poorly defined nosology. In 1983, we described 8-years follow-up of atrial dilatation with standstill evolution in 8 patients from 3 families. We later identified 5 additional patients with identical phenotypes: 1 member of the largest original family and 4 unrelated to the 3 original families. All families are from the same geographic area in Northeast Italy.

METHODS AND RESULTS

We followed up the 13 patients for up to 37 years, extended the clinical investigation and monitoring to living relatives, and investigated the genetic basis of the disease. The disease was characterized by: (1) clinical onset in adulthood; (2) biatrial dilatation up to giant size; (3) early supraventricular arrhythmias with progressive loss of atrial electric activity to atrial standstill; (4) thromboembolic complications; and (5) stable, normal left ventricular function and New York Heart Association functional class during the long-term course of the disease. By linkage analysis, we mapped a locus at 1p36.22 containing the Natriuretic Peptide Precursor A gene. By sequencing Natriuretic Peptide Precursor A, we identified a homozygous missense mutation (p.Arg150Gln) in all living affected individuals of the 6 families. All patients showed low serum levels of atrial natriuretic peptide. Heterozygous mutation carriers were healthy and demonstrated normal levels of atrial natriuretic peptide.

CONCLUSIONS

Autosomal recessive atrial dilated cardiomyopathy is a rare disease associated with homozygous mutation of the Natriuretic Peptide Precursor A gene and characterized by extreme atrial dilatation with standstill evolution, thromboembolic risk, preserved left ventricular function, and severely decreased levels of atrial natriuretic peptide.

Cardiac amyloidosis: approaches to diagnosis and management

Amyloidosis is a clinical disorder caused by the extracellular deposition of misfolded, insoluble aggregated protein with a characteristic ss pleated sheet configuration that produces apple-green birefringence under polarized light when stained with Congo red dye. The spectrum of organ involvement can include the kidneys, heart, blood vessels, central and peripheral nervous systems, liver, intestines, lungs, eyes, skin, and bones. Cardiovascular amyloidosis can be primary, a part of systemic amyloidosis, or the result of chronic systemic disease elsewhere in the body. The most common presentations are congestive heart failure because of restrictive cardiomyopathy and conduction abnormalities. Recent developments in imaging techniques and extracardiac tissue sampling have minimized the need for invasive endomyocardial biopsy for amyloidosis. Cardiac amyloidosis management will vary depending on the subtype but consists of supportive treatment of cardiac related symptoms and reducing the amyloid fibrils formation attacking the underlying disease. Despite advances in treatment, the prognosis for patients with amyloidosis is still poor and depends on the underlying disease type. Early diagnosis of cardiac amyloidosis may improve outcomes but requires heightened suspicion and a systematic clinical approach to evaluation. Delays in diagnosis, uncertainties about the relative merits of available therapies, and difficulties in mounting large-scale clinical trials in rare disorders combine to keep cardiac amyloidosis a challenging problem. This review outlines current approaches to diagnosis, assessment of disease severity, and treatment of cardiac amyloidosis.

Prolonged transient atrial electrical silence following termination of chronic atrial tachyarrhythmias

INTRODUCTION

Atrial standstill is a rare heterogeneous arrhythmia characterized by electrical and mechanical standstill and electrical inexcitability. A long-lasting progressive form is seen with cardiac and neuromuscular diseases, and a familial or idiopathic form may have a genetic basis. A transient form was described secondary to drug intoxication, electrolyte imbalance, cardiac inflammation, and ischemia.

METHODS

We investigated three patients with long-standing atrial tachyarrhythmia (AT) (atrial flutter in two, and focal atrial tachycardia in one). All patients underwent a complete electrophysiological study with mapping of right and left atrial activity and radiofrequency ablation (RF Abl) of AT.

RESULTS

Following RF Abl of AT, all three patients manifested transient atrial electrical silence in the absence of known reversible causes. Atrial electrical silence was observed when, following AT termination, an escape atrioventricular (AV) junctional rhythm (in two patients) and an escape VVI pacemaker rhythm (in one patient) showed transient ventriculo-atrial (VA) conduction block (up to 30 seconds). A dominant sinus rhythm was observed to return 30 minutes, 90 minutes, and 12 hours, respectively, in the three patients. Two patients received a dual chamber pacemaker and a decision was made not to upgrade the patient with VVI pacemaker.

DISCUSSION AND CONCLUSIONS

The present report expands the spectrum of the syndrome of atrial standstill and raises interesting questions regarding possible electrophysiologic mechanism(s) of prolonged post overdrive atrial standstill. The report suggests that chronic overdrive of sinus and subsidiary atrial pacemakers may result in calcium overloading of cardiac cells, which is known to cause suppression of pacemaker activity as well as increased intracellular resistance. These mechanisms can possibly result in either prolonged suppression of sinus and atrial pacemaker activity and/or pacemaker exit block.

Progressive and Persistent Atrial Inexcitability

Sinus node disease is characterized by the presence of significant sinus bradycardia or prolonged sinus pauses, and is attributed to either primary failure of sinus node automaticity or sino-atrial conduction disturbance. We present two patients with symptomatic bradycardia due to idiopathic global atrial inexcitability.

Familial Atrial Standstill in Association with Dilated Cardiomyopathy

. Atrial standstill is an extremely uncommon arrhythmia that rarely appears to be familial and genetically determined. Atrial standstill has been associated with several conditions including, but not restricted to, congenital heart disease, valvular heart disease, conduction disturbances, Brugada syndrome, myocardial infarction, and amyloidosis. Only a few cases of familial clustering of atrial standstill have been reported so far. This report represents a family with atrial standstill associated with syncope, dilated cardiomyopathy, and sudden cardiac death.

Left atrial myopathy in cardiac amyloidosis: implications of novel echocardiographic techniques

AIMS

To assess left atrial (LA) function and determine the prevalence of LA dysfunction in AL amyloidosis (AL) using conventional and strain echocardiography.

METHODS AND RESULTS

LA ejection fraction, LA filling fraction, LA ejection force, peak LA systolic strain rate (LAsSR), and LA systolic strain (LA epsilon) were determined in 95 AL patients (70 with and 25 without echocardiographic evidence of cardiac involvement, abbreviated CAL and NCAL, respectively), 30 age-matched controls (CON), and 20 patients with diastolic dysfunction and LA dilatation (DD). Peak LAsSR >2 standard deviations below mean CON value was used as the cut-off for normal LA function. LA ejection fraction was lower in CAL when compared with CON (40.4+/-13.6 vs. 67.0+/-6%, P=0.01). Left atrial septal strain rate and strain were lower in CAL (0.8+/-0.5 s(-1) and 5.5+/-4%, respectively) compared with CON (1.8+/-0.8 s(-1) and 14+/-4%, respectively, P=<0.0001), NCAL (1.6+/-0.8 s(-1) and 13+/-7%, respectively, P<0.0001) and DD (1.3+/-0.4 s(-1) and 10+/-2%, respectively, P<0.0001). Based on peak LA systolic strain rate criteria, the cut-off values for normal LA function were -1.1 s(-1) and -1.05 s(-1) for lateral and septal walls. Using these criteria, LA dysfunction was identified in 32% (lateral LA criteria) and 60% (septal LA criteria) of CAL patients. Lateral and septal LAsSR were lower in CAL patients with vs. those without symptoms of heart failure. Inter- and intra-observer agreement was high for LA strain echocardiography.

CONCLUSION

LA function assessment using strain echocardiography is feasible with low intra- and inter-observer variability. LA dysfunction is observed in AL patients without other echocardiographic features of cardiac involvement and may contribute to cardiac symptoms in CAL.

A cardiac sodium channel mutation cosegregates with a rare connexin40 genotype in familial atrial standstill

Atrial standstill (AS) is a rare arrhythmia that occasionally appears to be genetically determined. This study investigates the genetic background of this arrhythmogenic disorder in a large family. Forty-four family members were clinically evaluated. One deceased and three living relatives were unambiguously affected by AS. All other relatives appeared unaffected. Candidate gene screening revealed a novel mutation in the cardiac sodium channel gene SCN5A (D1275N) in all three affected living relatives and in five unaffected relatives, and the deceased relative was an obligate carrier. In addition, two closely linked polymorphisms were detected within regulatory regions of the gene for the atrial-specific gap junction protein connexin40 (Cx40) at nucleotides -44 (G-->A) and +71 (A-->G). Eight relatives were homozygous for both polymorphisms, which occurred in only approximately 7% of control subjects, and three of these relatives were affected by AS. The three living AS patients exclusively coinherited both the rare Cx40 genotype and the SCN5A-D1275N mutation. SCN5A-D1275N channels showed a small depolarizing shift in activation compared with wild-type channels. Rare Cx40 genotype reporter gene analysis showed a reduction in reporter gene expression compared with the more common Cx40 genotype. In this study, familial AS was associated with the concurrence of a cardiac sodium channel mutation and rare polymorphisms in the atrial-specific Cx40 gene. We propose that, although the functional effect of each genetic change is relatively benign, the combined effect of genetic changes eventually progresses to total AS.

Images in cardiology. Infective endocarditis

Images

Non-invasive detection of left atrial mechanical failure in patients with left ventricular disease

OBJECTIVE

To define patients with left atrial mechanical failure and identify its echocardiographic, physiological, and clinical associations.

DESIGN

Prospective study with cross sectionally guided M mode and Doppler echocardiograms, and with apexcardiograms, electrocardiograms, and phonocardiograms.

SETTING

Tertiary cardiac referral centre.

PATIENTS

10 patients with left atrial mechanical failure and 20 healthy controls of similar age.

RESULTS

10 patients with left atrial mechanical paralysis were identified among 4036 adults over a 1 year interval. Nine were in sinus rhythm and one had a DDD pacemaker. Left atrial mechanical activity was absent on M mode echocardiograms of the left sided atrioventricular ring and the aortic root. A Doppler A wave on transmitral flow and a clearly defined A wave on the left ventricular apexcardiogram were also absent, though evidence of right atrial mechanical movement was present in nine patients. Mean (SD) age was 63 (19) years and six were men. Nine had left ventricular disease and one had undergone extensive resection of the left atrium. Abnormal measurements of left ventricular end diastolic dimension (62 (13) mm), fractional shortening (15 (6)%), isovolumic relaxation time (19 (12) ms), left atrial size (45 (10) mm), and transmitral Doppler E wave deceleration time (110 (35) ms) were recorded.

CONCLUSION

Left atrial mechanical failure may be present in patients with left ventricular disease despite normal sinus rhythm. Normal atrial activation on 12 lead electrocardiogram suggests it is primarily mechanical in origin. The possibility of left atrial mechanical failure must be considered when Doppler patterns of transmitral flow are used to assess left ventricular diastolic function.

Clinical and electrophysiological characteristics of atrial standstill

To clarify the clinical and electrophysiological characteristics of atrial standstill (AS) we studied 11 patients (7 males and 4 females), whose average age was 62 years and who were followed over a period of 4-179 months. Underlying heart disease was present in nine patients and two cases were idiopathic. Major clinical symptoms in the 11 cases included Adams-Stokes attacks, and dyspnea on exertion. In the standard 12-lead ECGs obtained on admission, the P wave was absent in six cases. Atrial flutter (AF) was noted in 3, atrial fibrillation (Af) in 1, and multifocal atrial tachycardia in 1. In some cases, the ECG initially showed AF or Af, and was transformed after several years into ectopic atrial tachycardia or an ectopic atrial rhythm with a markedly decreased amplitude of the P wave. Finally, the P wave disappeared over a prolonged period. When intracardiac mapping was performed, the atrial electrograms tended to diminish at the site of high, mid-lateral right atrium (RA). Electrograms were remained present in the vicinity of the tricuspid valve (TV) annulus. A repeated mapping and pacing study conducted in two patients revealed that the "silent" area spread toward the lower site of RA. During the average follow-up period of 64 months, four patients died. The interval until death in one patient with myocarditis was 6 months, and in another with dilated cardiomyopathy (DCM) it was 8 months. It appears that the atrial muscular lesion starts in the high lateral RA and progresses toward the lower RA, then to the vicinity of the TV annulus. A diffuse and progressive disturbance may occur not only in the atrial muscle, but also in the atrioventricular conduction system in patients with AS who had progressive myocarditis or DCM.

Resolution of atrial standstill in a child with myocarditis

Atrial standstill is a rare disorder usually seen in adults with extreme myocardial disease. Etiologies described in the literature have included muscular dystrophy, familial amyloidosis, and rarely myocarditis. These etiologies usually lead to permanent atrial standstill and require ventricular pacing. We present a case of an 11-year-old black female who developed atrial standstill secondary to biopsy proven acute necrotizing myocarditis. Absence of atrial function was confirmed by surface electrocardiogram, echocardiogram, and an invasive electrophysiology study. Atrial function returned within 3 days of initiation of methyl-prednisolone. In cases of atrial standstill due to myocarditis, a delay in the placement of a permanent pacemaker with or without a trial of methylprednisolone may prove beneficial.

Persistent atrial standstill--clinical, electrophysiological, and morphological study

Persistent atrial standstill (PAS) is a rare disorder characterized by absence of atrial activity on the surface and intracavity electrograms, absence of atrial mechanical activity, and inability to electrically stimulate the atria. Four patients (ages 18-60 years) with PAS were evaluated. One of these (no. 3) only had right atrial (RA) standstill, whereas left atrium (LA) showed spontaneous activity and could be stimulated electrically. As RA biopsy is not possible, right ventricular (RV) endomyocardial biopsy (EMB) was obtained to identify possible atrial pathology that revealed inflammatory myocarditis, 2; amyloidosis, 1; and myocardial hypertrophy with fibrosis, 1. Three patients were given permanent pacemakers. One of these with amyloidosis died suddenly. One is lost to follow-up. The others cases are persisting with PAS.

Atrial standstill: an indication for rate responsive pacing

Atrial standstill (atrial paralysis) is a rare reason for permanent bradycardia. A case of atrial standstill is presented. A 35-year-old man had suffered from bradycardia since his childhood. For 2 years he had complaints (diminishment of his working capacity, and dyspnea occurred with effort) as well. On admission, a slow (38/min) junctional escape rhythm could be detected. There were no signs of atrial mechanical activity (atrial contraction) according to chest x ray, echocardiography, and the atrial pressure curve. The electrophysiological study revealed that the atria could not be electrically stimulated, and no P wave (A wave) could be recorded on right atrial electrograms. The patient received a rate responsive pacemaker. After pacemaker implantation, he became symptom-free; his working capacity improved markedly and his heart size decreased. Owing to the permanent bradycardia and the lack of atrial stimulation, the atrial standstill represents an indication for ventricular rate responsive pacing. Atrial standstill, permanent bradycardia, and the inability to stimulate the atrium are indications for ventricular rate responsive pacing.