A 73-year-old Caucasian male with a past medical history of hypertension, hyperlipidemia, right bundle branch block, hereditary transthyretin amyloidosis (Leu78His variant, 3 affected first-degree relatives) status post orthotopic liver transplant (OLT) in 2006, presented to the emergency department with exertional dyspnea and presyncope. Initial evaluation was notable for bradycardia with high-grade atrioventricular block (AVB). Electrocardiography one year prior to the presentation demonstrated sinus rhythm with first-degree AVB and right bundle branch block. An echocardiogram performed at the same time revealed a mild increase in left ventricular (LV) wall thickness (1.3 cm) and normal LV ejection fraction (EF) of 57%. Cardiovascular magnetic resonance (CMR) or scintigraphy imaging was not performed before OLT in 2006. Given the AVB and history of amyloidosis, CMR was ordered.
CMR was performed at 1.5T (Magnetom Avanto, Siemens Healthineers, Germany) using standardized protocols with cine imaging, T1 mapping (Modified Look-Locker Inversion Recovery sequence), T2 mapping (T2-prepared balanced steady-state free precession), and late gadolinium enhancement imaging (phase-sensitive inversion recovery). The LV was top-normal in size (LV end-diastolic volume index 103 ml/m2) and exhibited increased LV wall thickness (1.5 cm), with normal LV (57%) and right ventricular (RV) EF (58%). T2 signal was diffusely elevated (up to 57 ms; Figure 1). Pre-contrast native T1 was elevated in the septum (1142 ms) with extracellular volume fraction of 45% (Figure 1). CMR reference values for the myocardium were based on institutionally established normative control data and were as follows: native T1 1002 ± 41 ms, extracellular volume fraction 25 ± 3%, T2 47 ± 3 ms. There was evidence of altered gadolinium kinetics with prominent and diffuse late gadolinium enhancement in the basal LV segments, dense foci in the septal and lateral walls (Figure 1) with biatrial and partial RV enhancement. 99m-technetium pyrophosphate (Tc-99m PYP) imaging demonstrated a 3-hour heart/contralateral lung ratio of 1.99 and grade 3 myocardial uptake, which confirmed the CMR-based initial diagnosis of cardiac amyloidosis (Figure 1). Laboratory testing was negative for light-chain amyloidosis.
OLT is regarded as a definitive therapy for transthyretin amyloidosis due to halting production of the amyloidogenic transthyretin (TTR) protein. Despite improvement in patient mortality after OLT, progressive cardiomyopathy can still occur [1]. This is hypothesized to be due to continued deposition of wild-type TTR onto an amyloidogenic scaffold from pre-existing mutant TTR [2]. Progressive cardiac disease is not seen in patients undergoing both heart and liver transplant [3].
This case highlights the importance of CMR in cardiac monitoring in patients with amyloidosis, regardless of the type of treatment implemented [4]. The patient exhibited conduction disease for years prior to his index presentation. After CMR and Tc-PYP imaging, the patient underwent pacemaker implantation and was placed on tafamidis therapy. He remains on angiotensin receptor blocker and beta blocker (introduced due to frequent episodes of nonsustained ventricular tachycardia) with good tolerance. Given advancements in medical therapy for cardiac amyloidosis, early detection via CMR can alter management and should be considered in patients with amyloidosis even after OLT.
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