Phenotypic presentation trends of transthyretin amyloid cardiomyopathy: are we getting better?

Introduction

Transthyretin amyloid cardiomyopathy (ATTR-CM) is being increasingly recognized due to recent advances in non-invasive imaging notably bone scintigraphy and newer effective therapies - particularly tafamidis, which was shown to improve survival and decrease heart failure hospitalizations in the ATTR-ACT trial. Earlier tafamidis use appeared to be more beneficial, as reflected by NYHA class I and II patients being associated with lower mortality and hospitalizations compared to NYHA class III. Increased awareness will likely lead to an increasing number of ATTR-CM patients being diagnosed with concerns regarding applicability of ATTR-ACT criteria on these patients.

Purpose

To investigate ATTR-CM phenotypic presentation trends based on initial clinical, biomarkers and transthoracic echocardiographic (TTE) data.

Methods

From 2005–2020, 116 ATTR-CM patients were seen at our amyloidosis center, who were stratified into 3 time periods based on the date of diagnosis: Early (21 patients, pre-2016), Mid (46 patients, 2016–2018), and Recent (49 patients, 2018–2020). ATTR-CM diagnosis was established based on the standard criteria of confirmed ATTR variant + typical TTE features; histological confirmation endomyocardial biopsy; or typical diffuse cardiac tracer uptake on bone scintigraphy while ruling out light chain amyloidosis. With less typical imaging, cardiac MRI typically served as a confirmatory test prior to pursuing histological confirmation. Demographics, cardiac biomarkers, diagnostic method used, and TTE variables that raise the suspicion of ATTR-CM were compared across time periods using one-way ANOVA test and Fischer's exact test.

Results

There was a significant change in the predominant method of diagnosis with the majority of patients in the Early time period diagnosed by endomyocardial biopsy, whereas in the Recent time period the majority of patients were diagnosed via pyrophosphate scintigraphy (Figure). Despite increasing number of patients being diagnosed, the clinical phenotype at diagnosis did not change significantly with similar proportion of patients NYHA class I/II, median daily diuretic dose, biomarkers, having at least one heart failure hospitalization prior to diagnosis, and similar TTE phenotype (Table). Only the age at diagnosis significantly increased across time periods. Women represented the minority of patients across all time periods.

Conclusion

Despite the increased awareness of ATTR-CM, there have been no major changes in the clinical, cardiac biomarker, or TTE phenotype on presentation in patients referred to our center for suspicion or a diagnosis of ATTR-CM. Our findings challenge the assumption that patients with ATTR-CM are being identified earlier with milder phenotypes. Women with ATTR-CM likely remain largely undiagnosed in our community. Continued education and knowledge dissemination are essential to identify ATTR-CM patients earlier to achieve better outcomes in this population.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Pranav Chandrashekar is supported by an educational grant from Pfizer, Inc paid to Oregon Health and Science University. Table 1

Management strategies for atrial fibrillation and flutter in patients with transthyretin cardiac amyloidosis

Background

Atrial fibrillation (AF) and flutter (AFL) are common in transthyretin cardiac amyloidosis (ATTR-CM). Ventricular rate control drugs in ATTR-CM are poorly tolerated but data addressing tolerability and efficacy of rhythm control strategies is limited.

Purpose

We report characteristics and outcomes of AF/AFL in a cohort with ATTR-CM.

Methods

A single center observational study of patients seen at our Amyloidosis Center with wild-type or hereditary ATTR-CM diagnosed between 2005–2019. Treatment was prescribed as per treating cardiologists.

Results

Eighty-four patients with ATTR-CM (average age 74±10 years, 94% male) had mean follow-up of 27.6±22.8 months. AF/AFL occurred in 61 patients (73%). Clinically significant rapid ventricular response (RVR) was common as well attempted rate control with AV node blockers (Table 1). However, discontinuation was frequent (80%), often for adverse effects of hypotension (33%), bradycardia (15%), or presyncope/syncope (10%). Rhythm control was initiated in 64%, most often with cardioversion (DCCV) or ablation (Table 2). Post-DCCV recurrence was common (91%) and time to recurrence did not differ with use of anti-arrhythmic drugs (AAD; 5.8 months (IQR 1.9–12.5) vs without AAD 6.2 months (IQR 1.9–12.5) p=0.83). TEE was performed for 33% of DCCV with thrombus seen in 11% of cases – all patients who were not anticoagulated at the time. TEE was otherwise deferred due to known AF/AFL duration <48 hours (13%) or adequate anticoagulation (54%). Ablation was performed in 23% of patients with AFL (all for typical AFL) with 2 patients (14%) having recurrence after mean of 60.9 months. Pulmonary vein isolation for AF was performed in 12% (86% for persistent AF) with 86% recurrence after median of 6.2 months (IQR 5.6–12.3). Most patients (62%) with rhythm control had subjective improvement (≥1 NYHA class or resolved palpitations). Among AAD, amiodarone was most well tolerated with only 8% of patient discontinuing due to side effects. DCCV and ablation resulted in no direct complications although one patient had a perforation of a previously unknown Zenker diverticulum during TEE pre-DCCV.

Conclusions

In our ATTR-CM cohort, AF/AFL was common. Rate control was poorly tolerated and often abandoned. While rhythm control of AF/AFL had a favorable safety profile and successful conversion to sinus rhythm led to symptomatic improvement in a majority of cases, durable success with rhythm control was limited, often requiring multiple therapies. DCCV is only modestly successful and not significant improved with AAD. Ablation was successful in cases of cavo-tricuspid isthmus dependent AFL but had limited success in AF.

Funding Acknowledgement

Type of funding sources: None.