Familial and primary cardiac amyloidosis: echocardiographically similar diseases with distinctly different clinical outcomes
- The First Department of Internal Medicine,
- Shinshu University School of Medicine,
- Matsumoto 390, Japan
Sir,—In a recent issue, Dubrey et al reported interesting data concerning echocardiographic and electrocardiographic features in relation to the clinical outcome in two types of systemic amyloidosis: primary (AL) and familial.1 They pointed out that despite indistinguishable echocardiographic findings, including comparable ventricular wall thickening, patients with familial amyloid polyneuropathy (FAP) had a lower incidence of heart failure and low voltage on ECG, as well as longer one year survival, compared with patients with AL amyloidosis. Based on these results, Dubrey et al suggested differences in biochemical characteristics of the two types of amyloid fibril or myocyte response to myocardial amyloid deposition. Another point of interest was that echocardiographic abnormalities might be related to the type of mutant transthyretin genes. They noted fewer significant abnormalities in patients with FAP and the valine-30-methionine mutation compared with patients with other mutations.
On the basis of our data2-8 and extensive experience over 20 years, we agree with Dubrey et al’s data on ECG voltage–mass relation and mortality from cardiac causes in patients with FAP or AL amyloidosis. However, additional comments on their echocardiographic findings, especially in patients with FAP, are necessary. Dubrey et al included only patients with ventricular wall thickening of > 1.3 cm. This may result in nearly identical echocardiographic data in the two types of amyloid disease. However, 70% of their original patients with FAP had normal or only minor abnormalities. In contrast to other forms of amyloid heart disease, such as primary amyloidosis, amyloid deposition in FAP is generally noticeable in the subendocardium and valves, and less so in the myocardium.2 9 In addition, as we have previously reported,3 the incidence and magnitude of the echocardiographic abnormalities in FAP are generally mild to moderate compared with those in primary amyloidosis, and progressive development of these abnormalities occurs with progression of disease stage, duration of illness, and aging in patients with FAP. We also found amyloid deposition in the heart using endomyocardial biopsy, even in patients with FAP and no clinical or echocardiographic evidence of cardiac involvement, in whom left ventricular diastolic function5-7 and myocardial adrenergic innervation8 were severely impaired, and diffuse positive myocardial uptake of technetium-99m-pyrophosphate was usually observed.4 Thus, it is of note that the echocardiographic data and features presented by Dubrey et al are not always representative of patients with FAP, and that their data are derived only from patients with FAP and advanced cardiac amyloid infiltration.
