Isolated Atrial Amyloidosis in Patients with Various Types of Atrial Fibrillation

Imaging findings of right cardiac amyloidosis: impact on prognosis and clinical course

Cardiac involvement from amyloidosis is of growing interest in the overall literature. Despite cardiac amyloidosis (CA) has been considered for a long time a rare disease, the diagnostic awareness is increasing mainly thanks to the improvement of diagnostic softwares and of imaging techniques such as cardiac magnetic resonance  (CMR). Some authors have observed an increase of prevalence rate of CA; moreover it's often underestimated because clinical manifestations are aspecific. The interstitial infiltration of the left ventricle has been extensively studied, while the involvement of the right ventricle (RV) has been less investigated. Involvement of the RV, even in the absence of pulmonary hypertension or clearly left ventricle infiltration, plays an important role as prognostic factor and is useful to achieve an early diagnosis. Therefore, the use of fast and low-cost diagnostic methods such as ultrasound strain of the right ventricle could be used to recognize cardiac amyloidosis early. Herein the importance of evaluating the right ventricular involvement, which can predict the most severe course of the disease also without overt clinical manifestations. The role of imaging, in particular of echocardiography, CMR, and scintigraphy is here reported.

Epidemiology and clinical manifestations of cardiac amyloidosis

Cardiac amyloidosis, once considered a rare disease, has garnered significant attention over the last few years due to three key reasons: first, increased recognition of this disease in conjunction with various common cardiac conditions such as heart failure with preserved ejection fraction and aortic stenosis; second, due to the advent of promising new therapies for light chain disease (AL), transthyretin (ATTR) cardiomyopathy, and amyloid neuropathy; finally, the advancements in cardiac imaging including echocardiography, magnetic resonance imaging, and nuclear cardiac scintigraphy aid in non-biopsy diagnosis of ATTR cardiac amyloidosis. The hereditary forms of ATTR have further come into importance with the availability of genetic testing and increased prevalence of certain mutations in African Americans. Recognition of non-cardiac clues to this disease has gained importance and reiterates that high clinical suspicion, detailed patient history, and examination with appropriate use of imaging are vital to confirm the diagnosis.

Age-related amyloidosis outside the brain: A state-of-the-art review

Inside and outside the brain, accumulation of amyloid fibrils plays key roles in the pathogenesis of fatal age-related diseases such as Alzheimer's and Parkinson's diseases and wild-type transthyretin amyloidosis. Although the incidence of all amyloidoses increases with age, for some types of amyloidosis aging is known as the main direct risk factor, and these types are typically diseases of elderly people. More than 10 different precursor proteins are known to cause age-associated amyloidosis; these proteins include amyloid β protein, α-synuclein, transthyretin, islet amyloid polypeptide, atrial natriuretic factor, and the newly discovered epidermal growth factor-containing fibulin-like extracellular matrix protein 1. Except for intracerebral amyloidoses, most age-related amyloidoses have been little studied. Indeed, in view of the increasing life expectancy in our societies, understanding how aging is involved in the process of amyloid fibril accumulation and the effects of amyloid deposits on the aging body is extremely important. In this review, we summarize current knowledge about the nature of amyloid precursor proteins, the prevalence, clinical manifestations, and pathogenesis of amyloidosis, and recent advances in our understanding of age-related amyloidoses outside the brain.

Clinical implications of atrial natriuretic peptide amyloidosis

A 74-year-old woman with a history of diastolic heart failure and refractory atrial fibrillation (AF) presented with unstable angina for coronary artery bypass grafting. Routine pathological analysis of tissue specimens obtained from the left atrial appendage revealed subendocardial and interstitial fibrosis and patchy amyloid deposits with Congo red staining demonstrating filamentous deposits. Mass spectrometry was consistent with isolated atrial amyloidosis (IAA). IAA in this patient was found incidentally on routine postoperative pathology, but likely contributed to significant morbidity. The established relationship between IAA with AF and diastolic heart failure underscores the relevance. Further delineating the pathogenesis has potentially immense implications for the future management of associated conditions. To bridge the gaps in the understanding, a standardised approach to diagnosis is needed to open the door to a large-scale study and further work toward establishing evidence-based management pathways.

The long and winding road to target protein misfolding in cardiovascular diseases

BACKGROUND

In the last decades, cardiovascular diseases (CVD) have remained the first leading cause of mortality and morbidity in the world. Although several therapeutic approaches have been introduced in the past, the development of novel treatments remains an important research goal, which is hampered by the lack of understanding of key mechanisms and targets. Emerging evidences in recent years indicate the involvement of misfolded proteins aggregation and the derailment of protein quality control in the pathogenesis of cardiovascular diseases. Several potential interventions targeting protein quality control have been translated from the bench to the bedside to effectively employ the misfolded proteins as promising therapeutic targets for cardiac diseases, but with trivial results.

DESIGN

In this review, we describe the recent progresses in preclinical and clinical studies of protein misfolding and compromised protein quality control by selecting and reporting studies focusing on cardiovascular diseases including cardiomyopathies, cardiac amyloidosis, atherosclerosis, atrial fibrillation and thrombosis.

RESULTS

In preclinical models, modulators of several molecular targets (eg heat shock proteins, unfolded protein response, ubiquitin protein system, autophagy and histone deacetylases) have been tested in various conditions with promising results although lacking an adequate transition towards clinical setting.

CONCLUSIONS

At present, no therapeutic strategies have been reported to attenuate proteotoxicity in patients with CVD due to a lack of specific biomarkers for pinpointing upstream events in protein folding defects at a subclinical stage of the diseases requiring an intensive collaboration between basic scientists and clinicians.

Morpho-functional changes of cardiac telocytes in isolated atrial amyloidosis in patients with atrial fibrillation

Telocytes are interstitial cells with long, thin processes by which they contact each other and form a network in the interstitium. Myocardial remodeling of adult patients with different forms of atrial fibrillation (AF) occurs with an increase in fibrosis, age-related isolated atrial amyloidosis (IAA), cardiomyocyte hypertrophy and myolysis. This study aimed to determine the ultrastructural and immunohistochemical features of cardiac telocytes in patients with AF and AF + IAA. IAA associated with accumulation of atrial natriuretic factor was detected in 4.3-25% biopsies of left (LAA) and 21.7-41.7% of right (RAA) atrial appendage myocardium. Telocytes were identified at ultrastructural level more often in AF + IAA, than in AF group and correlated with AF duration and mitral valve regurgitation. Telocytes had ultrastructural signs of synthetic, proliferative, and phagocytic activity. Telocytes corresponded to CD117+, vimentin+, CD34+, CD44+, CD68+, CD16+, S100-, CD105- immunophenotype. No significant differences in telocytes morphology and immunophenotype were found in patients with various forms of AF. CD68-positive cells were detected more often in AF + IAA than AF group. We assume that in aged AF + IAA patients remodeling of atrial myocardium provoked transformation of telocytes into "transitional forms" combining the morphological and immunohistochemical features with signs of fibroblast-, histiocyte- and endotheliocyte-like cells.

Isolated atrial amyloidosis suspected by electrophysiological voltage mapping and diagnosed by 99m Tc-DPD scintigraphy

We present not‐yet‐seen multimodal images of a 55‐year‐old female patient with isolated atrial amyloidosis (IAA) who clinically suffered from multiple atrial arrhythmias and heart failure symptoms with preserved left ventricular ejection fraction. We aim to show structural and functional abnormalities detected by electrophysiological voltage mapping, cardiac magnetic resonance imaging (MRI) [cMRI; atrial strain measurements, late gadolinium enhancement (LGE) visualization], and ^99mTc‐DPD scintigraphy. Bipolar voltage mapping performed during two electrophysiological procedures showed diffuse left atrial low‐voltage areas (bipolar < 0.5 mV) and also a moderately diseased right atrium suspected of infiltrative cardiomyopathy. Catheter ablation did successfully treat a left atrial and two right atrial focal tachycardias. For further diagnostics, a 3T cMRI was performed, revealing a subendocardial circumferential left atrial LGE and pathological atrial strain measurements, especially during conduit and reservoir phase. Afterwards, nuclear imaging with 559 MBq of ^99mTc‐DPD was performed. The scan revealed amyloid infiltration of the left atrium. Neither an uptake in the ventricular myocardium nor an extra‐cardiac uptake of DPD was seen. Genetic testing for transthyretin amyloidosis mutations in this patient was negative, and peripheral neuropathy was ruled out by electromyogram analysis. The synopsis of these findings reveals IAA as the most possible diagnosis and showed isolated atrial nuclear tracer uptake with ^99mTc‐DPD scintigraphy for the first time. Non‐invasive imaging techniques might help in suggesting IAA but need further investigation.

Reduced left atrial myocardial deformation irrespective of cavity size: a potential cause for atrial arrhythmia in hereditary transthyretin amyloidosis

BACKGROUND

Cardiac amyloidosis (CA) is a myocardial disease and commonly under-diagnosed condition. In CA patients, atrial fibrillation might occur in the absence of left atrial (LA) enlargement.

OBJECTIVES

The aim of this study is to assess LA size and function, and its relationship with atrial arrhythmia in patients with hereditary transthyretin amyloidosis (ATTR).

METHODS

Forty-six patients with confirmed ATTR amyloidosis on abdominal biopsy were studied. Assessment with 2D echocardiography and 2D strain showed 31 patients had increased LV wall thickness (LVWT) (septal thickness >12 mm), and 15 had normal LVWT. In addition to conventional measurements, LV and LA global longitudinal strain (GLS%) and strain rate (SR) were obtained. Western blot analysis was done to assess fibril type. ATTR patients with increased LVWT were compared with 23 patients with hypertrophic cardiomyopathy (HCM) and 31 healthy controls. ATTR amyloidosis patients also underwent 24 hour Holter monitoring to determine the presence of atrial arrhythmia.

RESULTS

Atrial deformation during atrial systole was reduced in ATTR amyloidosis patients with increased LVWT independent of LA size and in contrast to HCM. Twenty of the ATTR amyloidosis patients (54%) had ECG evidence of significant atrial arrhythmic events. LA strain rate, during atrial systole, was the only independent predictor of atrial arrhythmia (β = 3.28, p = .012).

CONCLUSION

In ATTR cardiomyopathy with increased LVWT, LA myocardial function is abnormal, irrespective of atrial cavity size. Reduced LA myocardial SR during atrial systole, irrespective of cavity volume, E/e' and LV deformation, is also a strong predictor for atrial arrhythmic events.