Cardiac Resynchronization Therapy for Transthyretin Cardiac Amyloidosis

Transthyretin amyloid cardiomyopathy: Literature review and red-flag symptom clusters for each cardiology specialty

Wild-type transthyretin amyloid cardiomyopathy (ATTRwt-CM) is a progressive and infiltrative cardiac disorder that may cause fatal consequences if left untreated. The estimated survival time from diagnosis is approximately 3-6 years. Because of the non-specificity of initial symptom manifestation and insufficient awareness among treating physicians, approximately one-third of patients with ATTRwt-CM are initially misdiagnosed with other cardiac diseases. Although heart failure (HF) is the most common initial manifestation of ATTRwt-CM, observed in nearly 70% of affected patients, patients may also present with other cardiologic symptoms, such as atrial fibrillation (AF) and aortic stenosis (AS). This non-specific and diverse nature of the initial ATTRwt-CM presentation indicates that various cardiology subspecialties are involved in patient diagnosis and management. Standard guideline-directed pharmacological treatment for HF is not recommended for patients with ATTRwt-CM because of its limited effectiveness. However, no established algorithms are available regarding HF management in this patient population. This literature review provides an overview of the red flags for ATTRwt-CM and research findings regarding HF management in this patient population. In addition to commonly recognized red flags for ATTRwt-CM (e.g., HF, AF and severe AS), published literature identified potential red flags such as coronary microvascular dysfunction. For HF management in patients with ATTRwt-CM, the use of mineralocorticoid receptor antagonists (MRAs) was reported as a well-tolerated option associated with a low discontinuation rate and reduced mortality. Although there is no concrete evidence for recommendations against sodium-glucose cotransporter 2 inhibitor (SGLT2i) administration, research supporting its use is limited to small-scale studies. Robust evidence is lacking for AF ablation, implantable cardioverter-defibrillators and cardiac resynchronization therapy. Based on the published findings and our clinical experience as Japanese ATTRwt-CM experts, red-flag symptom clusters for each cardiology specialty (HF, arrhythmia and ischaemia/structural heart disease) and a treatment scheme for HF management are presented. As this research area remains at an exploratory stage, our observations would require further discussion among experts worldwide.

Cardiac Amyloidosis Due to Transthyretin Protein: A Review

Importance

Systemic amyloidosis from transthyretin (ATTR) protein is the most common type of amyloidosis that causes cardiomyopathy.

Observations

Transthyretin (TTR) protein transports thyroxine (thyroid hormone) and retinol (vitamin A) and is synthesized predominantly by the liver. When the TTR protein misfolds, it can form amyloid fibrils that deposit in the heart causing heart failure, heart conduction block, or arrhythmia such as atrial fibrillation. The biological processes by which amyloid fibrils form are incompletely understood but are associated with aging and, in some patients, affected by inherited variants in the TTR genetic sequence. ATTR amyloidosis results from misfolded TTR protein deposition. ATTR can occur in association with normal TTR genetic sequence (wild-type ATTR) or with abnormal TTR genetic sequence (variant ATTR). Wild-type ATTR primarily manifests as cardiomyopathy while ATTR due to a genetic variant manifests as cardiomyopathy and/or polyneuropathy. Approximately 50 000 to 150 000 people in the US have heart failure due to ATTR amyloidosis. Without treatment, heart failure due to ATTR amyloidosis is associated with a median survival of approximately 5 years. More than 130 different inherited genetic variants in TTR exist. The most common genetic variant is Val122Ile (pV142I), an allele with an origin in West African countries, that is present in 3.4% of African American individuals in the US or approximately 1.5 million persons. The diagnosis can be made using serum free light chain assay and immunofixation electrophoresis to exclude light chain amyloidosis combined with cardiac nuclear scintigraphy to detect radiotracer uptake in a pattern consistent with amyloidosis. Loop diuretics, such as furosemide, torsemide, and bumetanide, are the primary treatment for fluid overload and symptomatic relief of patients with ATTR heart failure. An ATTR-directed therapy that inhibited misfolding of the TTR protein (tafamidis, a protein stabilizer), compared with placebo, reduced mortality from 42.9% to 29.5%, reduced hospitalizations from 0.7/year to 0.48/year, and was most effective when administered early in disease course.

Conclusions and Relevance

ATTR amyloidosis causes cardiomyopathy in up to approximately 150 000 people in the US and tafamidis is the only currently approved therapy. Tafamidis slowed progression of ATTR amyloidosis and improved survival and prevented hospitalization, compared with placebo, in people with ATTR-associated cardiomyopathy.

Arrhythmias and Device Therapies in Cardiac Amyloidosis

Cardiac amyloidosis is caused by amyloid fibrils that deposit in the myocardial interstitium, causing restrictive cardiomyopathy and eventually death. The electromechanical, inflammatory, and autonomic changes due to amyloid deposition result in arrhythmias. Atrial fibrillation is by far the most common arrhythmia. The rate control strategy is generally poorly tolerated due to restrictive filling physiology and heart rate dependance, favoring adoption of the rhythm control strategy. Anticoagulation for stroke prophylaxis is warranted, irrespective of CHA2DS2-VASc score in patients with a favorable bleeding profile; data on left appendage closure devices are still insufficient. Ventricular arrhythmias are also not uncommon, and the role of implantable cardioverter-defibrillator in cardiac amyloidosis is controversial. There is no evidence of improvement in outcomes when used for primary prevention in these patients. Bradyarrhythmia is most commonly associated with sudden cardiac death in cardiac amyloidosis. Pacemaker implantation can help provide symptomatic relief but does not confer mortality benefit.

Feasibility and safety of left bundle branch area pacing in cardiac amyloidosis. A single center experience

BACKGROUND

Conventional right ventricle (RV) pacemaker stimulation has been associated with worse clinical outcomes in patients with cardiac amyloidosis (CA). Left bundle branch area pacing (LABPP) has been suggested as a promising alternative. We sought to assess the safety, feasibility, and outcomes of LABPP in patients with CA.

METHODS

We retrospectively analyzed echocardiography and pacing parameters and clinical outcomes in 23 consecutive patients with CA and LBBAP implanted from June 2020 to October 2022.

RESULTS

LBBAP was successfully performed in 22 over 23 patients (19 male, 78.6 ± 11.7 years, 20 ATTR, mean LVEF 45.5 ± 16.2%). After the procedure, 9 patients showed Qr pattern and 11 a qR pattern in V1 on ECG. Average procedure time was 67 ± 28 min. After 7.7 ± 5.2 months follow-up, no procedure-related complications had occurred. Although, a significant reduction in QRS width (p = .001) was achieved, we did not observe significant changes in LVEF and Nt ProBNP at 6 months of follow-up. Pacing parameters were stable during follow-up: LBB capture threshold and R wave amplitude were 1.0 ±  0.5 V and 10.6 ± 6.0 mV versus 0.8 ±  0.1 V, p = .21 and 10.6 ± 5.1 mV (p = .985) at follow up.

CONCLUSION

LBBAP is safe and feasible pacing technique for patients with CA. LBBAP is associated with significant narrowing of QRSd without worsening in LVEF and Nt-proBNP.

Bradyarrhythmias in Cardiac Amyloidosis and Role of Pacemaker

Cardiac amyloidosis (CA) is an underdiagnosed disease that is caused by deposition of misfolded transthyretin (ATTR) or immunoglobulin light chain (AL) fibrils in the myocardium. Bradyarrhythmias are commonly seen in CA, due to disruption of conducting system by amyloid fibrils. Atrioventricular conduction defect is more common than sinus node dysfunction. Bradyarrhythmias are most prevalent in wtATTR, followed by hATTR and AL. Pacemaker implantation, when indicated, can help provide symptomatic relief but does not confer mortality benefit. Progression of conduction system disease is common and often leads to increased right ventricular pacing burden with time. Therefore, cardiac resynchronizing therapy (biventricular therapy) is often considered as a better and safer option in these patients. Finally, the role of prophylactic pacemaker implantation is controversial, and current guidelines do not recommend prophylactic pacemaker insertion in CA patients.

Genetic Abnormalities of the Sinoatrial Node and Atrioventricular Conduction

The peculiar electrophysiological properties of the sinoatrial node and the cardiac conduction system are key components of the normal physiology of cardiac impulse generation and propagation. Multiple genes and transcription factors and metabolic proteins are involved in their development and regulation. In this review, we have summarized the genetic underlying causes, key clinical findings, and the latest available clinical evidence. We will discuss clinical diagnosis and management of the genetic conditions associated with conduction disorders that are more prevalent in clinical practice, for this reason, very rare genetic diseases presenting sinus node or cardiac conduction system abnormalities are not discussed.

Electrical Dyssynchrony in Cardiac Amyloidosis: Prevalence, Predictors, Clinical Correlates, and Outcomes

BACKGROUND

Conduction-system involvement in cardiac amyloidosis (CA) is common. The prevalence, clinical correlates and impact on outcome related to ventricular electrical dyssynchrony in CA remain insufficiently elucidated.

METHODS

Data from a prospectively maintained registry of patients with CA diagnosed in the Cleveland Clinic's amyloidosis clinic was used to determine the frequency of electrical dyssynchrony (defined as a QRS > 130 msec). The relation with the clinical profile and clinical outcome was assessed. To determine the impact of hypertrophy on QRS prolongation, a QRS-matched cohort without CA was used for comparison of cardiac magnetic resonance imaging.

RESULTS

A total of 1140 patients with CA (39% AL, 61% TTR) were evaluated, of whom 230 (20%) had electrical dyssynchrony. The type of conduction block was predominantly a right bundle branch block (BBB, 48%) followed by left BBB (35%) and intraventricular conduction delay (17%). Presence of transthyretin amyloidosis (ATTR-CA), older age, male gender, white race, and coronary artery disease were independently (P< 0.05 for all) associated with electrical dyssynchrony, and patients were more commonly prescribed a mineralocorticoid receptor antagonist. In ATTR-CA, specifically, every increase in ATTR-CA disease stage was associated with a 1.55-fold (1.23--1.95; P< 0.001) increased odds for electrical dyssynchrony. In a subset of patients with CA who underwent cardiac magnetic resonance imaging (n = 41), left ventricular mass index was unrelated to the QRS duration (r = 0.187; P = 0.283) in CA, in contrast to a non-CA QRS-matched cohort (r = 0.397; P< 0.001). Patients with electrical dyssynchrony were more symptomatic at initial presentation, as illustrated by a higher New York Heart Association class (P= 0.041). During a median follow-up of 462 days (IQR:138--996 days), a higher proportion of patients with electrical dyssynchrony died from all-cause death (P= 0.037) or developed a permanent pacing indication (3% vs 10.4%; P< 0.001) during follow-up.

CONCLUSION

Electrical dyssynchrony is common in CA, especially in ATTR-CA, and is associated with worse functional status and clinical outcome. Given the high rate of permanent pacing indications at follow-up, additional studies are necessary to determine the best monitoring and pacing strategies in CA.

Management of Cardiac Symptoms in Amyloidosis

Cardiac amyloidosis (CA) results in symptoms of heart failure, atrial and ventricular arrhythmias, conduction disturbances, and profound autonomic dysfunction. These symptoms present unique management challenges as compared with patients without CA, and can be very debilitating. Thus, management of the cardiovascular symptoms of these patients plays a central role in their care. This review presents an overview of the typical cardiovascular manifestations encountered in patients with CA and highlights the key management considerations for each.

Ventricular arrhythmia burden and implantable Cardioverter-defibrillator outcomes in transthyretin cardiac amyloidosis

BACKGROUND

As targeted treatments for amyloid transthyretin cardiomyopathy (ATTR-CM) are becoming available, we aim to characterize the rates of ventricular arrhythmias (VAs), implantable cardioverter-defibrillator (ICD) utilization, and their impact on survival.

METHODS

This is a retrospective cohort study of 130 patients with ATTR-CM diagnosed at Emory University's Cardiac Amyloidosis Center between April 2012 and September 2020. VAs were defined as non-sustained or sustained ventricular tachycardia and ventricular fibrillation.

RESULTS

Of 130 patients, 42 had wild-type disease (wtATTR) and 88 had hereditary variants (hATTR), most commonly Val122Ile (89%). At ATTR-CM diagnosis, 80 (62%) patients had EF ≤ 40% consistent with systolic heart failure. Of the 69 (53%) patients with documented VAs significantly higher rates occurred among those with EF ≤ 40% compared with EF > 40% (67% vs 28%, p = 0.001). Thirty-two patients (25 hATTR, 7 wtATTR) had primary prevention ICDs implanted. Eight (25%) of these patients received appropriate ICD therapy while two (6%) experienced inappropriate therapy. Comparing patients with EF ≤ 35% with and without ICDs did not reveal any survival difference (3.3 ± 0.5 vs. 2.8 ± 0.4 years, p = 0.699).

CONCLUSIONS

High rates of VAs and appropriate ICD therapy were found amongst a unique cohort of largely hereditary ATTR-CM patients with a high rate of systolic heart failure. This article is protected by copyright. All rights reserved.

ATTR Amyloidosis: Current and Emerging Management Strategies: JACC: CardioOncology State-of-the-Art Review

Transthyretin cardiac amyloidosis (ATTR-CA) is increasingly diagnosed owing to the emergence of noninvasive imaging and improved awareness. Clinical penetrance of pathogenic alleles is not complete and therefore there is a large cohort of asymptomatic transthyretin variant carriers. Screening strategies, monitoring, and treatment of subclinical ATTR-CA requires further study. Perhaps the most important translational triumph has been the development of effective therapies that have emerged from a biological understanding of ATTR-CA pathophysiology. These include recently proven strategies of transthyretin protein stabilization and silencing of transthyretin production. Data on neurohormonal blockade in ATTR-CA are limited, with the primary focus of medical therapy on judicious fluid management. Atrial fibrillation is common and requires anticoagulation owing to the propensity for thrombus formation. Although conduction disease and ventricular arrhythmias frequently occur, little is known regarding optimal management. Finally, aortic stenosis and ATTR-CA frequently coexist, and transcatheter valve replacement is the preferred treatment approach.

Cardiovascular outcomes after cardiac resynchronization therapy in cardiac amyloidosis

Aims

Cardiac resynchronization therapy (CRT) is highly effective in dilated cardiomyopathy (DCM) patients with impaired left ventricular ejection fraction (LVEF) and left bundle block branch. In cardiac amyloidosis (CA) patients, left ventricular dysfunction and conduction defects are common, but the potential of CRT to improve cardiac remodelling and survival in this particular setting remains undefined. We investigated cardiovascular outcomes in CA patients after CRT implantation in terms of CRT echocardiographic response and major cardiovascular events (MACEs).

Methods and results

Our retrospective study included 47 CA patients implanted with CRT devices from January 2012 to February 2020, in nine French university hospitals (77 ± 6 years old, baseline LVEF 30 ± 8%) compared with propensity‐matched (1:1 for age, LVEF at implantation, and CRT indication) DCM patients with a CRT device. CA patients had lower rates of CRT response (absolute delta LVEF ≥ 10%) compared with DCM patients (36% vs. 70%, P = 0.002). After multivariate Cox analysis, CA was independently associated with MACE (hospitalization for heart failure/cardiovascular death) [hazard ratio (HR) 3.73, 95% confidence interval (CI) 1.85–7.54, P < 0.001], along with the absence of CRT response (HR 3.01, 95% CI 1.56–5.79, P = 0.001). The presence of echocardiographic CRT response (absolute delta LVEF ≥ 10%) was the only predictive factor of MACE‐free survival in CA patients (HR 0.36, 95% CI 0.15–0.86, P = 0.002).

Conclusion

Compared with a matched cohort of DCM patients, CA patients had a lower rate of CRT response and consequently a worse cardiovascular prognosis after CRT implantation. However, CRT could be beneficial even in CA patients given that CRT response was associated with better cardiac outcomes in this population.

Practical recommendations for the diagnosis and management of transthyretin cardiac amyloidosis

Cardiac amyloidosis (CA) is an infiltrative restrictive cardiomyopathy caused by accumulation in the heart interstitium of amyloid fibrils formed by misfolded proteins. Most common CA types are light chain amyloidosis (AL) caused by monoclonal immunoglobulin light chains and transthyretin amyloidosis (ATTR) caused by either mutated or wild-type transthyretin aggregates. Previously considered a rare disease, CA is increasingly recognized among patients who may be misdiagnosed as undifferentiated heart failure with preserved ejection fraction (HFPEF), paradoxical low-flow/low-gradient aortic stenosis, or otherwise unexplained left ventricular hypertrophy. Progress in diagnosis has been due to the refinement of cardiac echocardiographic techniques (speckle tracking imaging) and magnetic resonance (T1 mapping) and mostly due to the advent of bone scintigraphy that has enabled noninvasive diagnosis of ATTR, limiting the need for endomyocardial biopsy. Importantly, proper management of CA starts from early recognition of suspected cases among high prevalence populations, followed by advanced diagnostic evaluation to confirm diagnosis and typing, preferentially in experienced amyloidosis centers. Differentiating ATTR from other types of amyloidosis, especially AL, is critical. Emerging targeted ATTR therapies offer the potential to improve outcomes of these patients previously treated only palliatively.