Amyloidosis is a systemic illness with a large spectrum of clinical presentation and varied prognosis.1
Cardiac amyloidosis occurs usually in AL type amyloidosis due to the deposition of low molecular weight proteins in the intercellular spaces of cardiac myocytes and carries worse prognosis.2
Cardiac amyloidosis is rare among Caucasians (0.6%).3
The common clinical presentation of cardiac amyloidosis results from the infiltrative cardiomyopathy secondary to diffuse amyloid deposition of the ventricles. Patients often present with features of congestive cardiac failure and predominantly right heart failure.4
Other cardiac manifestations include syncope and angina. Renal involvement often accompanies cardiac amyloidosis and makes both diagnosis and treatment challenging.
Cardiovascular examination may reveal elevated JVP, bipedal oedema, hypotension, third heart sound and soft systolic murmur. ECG shows low voltage complexes (in 46%) or pseudo-infarct pattern.4
Trans-thoracic echocardiogram forms the cornerstone in the diagnosis of cardiac amyloidosis. Echocardiographic findings include thickened ventricular and septal walls, dilated atria, small sized ventricular cavity and a ‘speckled’ appearance of the myocardium. Valvular involvement is rare and best quantified by echocardiogram. Under normal physiological conditions, left ventricular filling happens due to predominant passive filling (E filling) and minimal atrial contraction (A filling). In cardiac amyloidosis, E/A ratio is increased with rapid equalisation of the filling pressures resulting in a short deceleration time due to amyloid infiltration and thereby resulting in restriction of diastolic ventricular function. The mechanisms for changes in E/A ratio in restrictive filling are described elsewhere.5
Coronary angiography is often normal and right heart studies may show elevated right heart pressures. Cardiac MRI shows late and global subendocardial enhancement. The combination of low voltage complexes on ECG and thickened interventricular septum on echocardiography has been shown to be highly specific for diagnosis of cardiac amyloidosis.6
Technetium-labelled SAP radioisotope scan can identify tissue infiltration of amyloid fibrils. This test is not useful in cardiac amyloidosis due to the presence of large amount of circulating blood in cardiac chambers, which makes the differentiation of myocardial infiltration more difficult to interpret. However, although LVH seen in these cases would not be incompatible with diffuse myocardial infiltration; we believe this finding is due to the existence of hypertension. A higher prevalence of ‘silent’ AF and mural thrombi in this group is well known. But, the absence of a giant left atrium (more than 5.5 cm), absence of stenotic mitral valve lesion, absence of severe left ventricular dysfunction, lack of ‘auto contrast’ in the chambers and the absence of LV aneurysm led us to believe the risk of cardiac thrombo-embolic event to be low in this case.
Cardiac involvement isolated to the mitral valve as happened in our patient is rare and has been reported only a few times in the literature.7 8
Mitral valve dysfunction in cardiac amyloidosis can be due to local amyloid deposition, chordal rupture and local ischaemia or secondary to mitral annular dilatation.
The differential diagnosis of light chain cardiac amyloidosis includes various aetiologies of infiltrative cardiomyopathy such as sarcoidosis, haemochromatosis, senile cardiomyopathy and endomyocardial fibrosis. Haemochromatosis is associated with iron overload and serum ferritin levels more than 1000 g/l. Sarcoidosis is diagnosed by classical peri-hilar shadows on chest x-ray and often associated with raised serum calcium. Endomyocardial fibrosis is a hyper-eosinophilic syndrome with good response to steroids.
We propose that the mitral valve dysfunction seen in our patient is secondary to amyloid deposits in the subvalvular apparatus, which has altered the actual physical properties of the valve resulting in incompetence. Moreover, his mitral regurgitation and symptoms of congestive heart failure improved with chemotherapy and heart failure therapy. The literature on the reversibility of mitral valve dysfunction in cardiac amyloidosis is scanty. Combination chemotherapy of patients with cardiac amyloidosis has been shown to produce remission in up to 21%.9
The prognosis of the illness in this subset of patients with isolated valvular involvement is unknown but the reversibility of mitral regurgitation as happened in our case may suggest a better prognosis. In addition, as in our case, the presence of large voltage complexes in the ECG of patients with suspected cardiac amyloidosis does not refute the diagnosis.