Cardiac amyloidosis

ECG : Sinus rhythm with low-voltage P wave; normal PR interval; clearly low-voltage QRS in limb leads (< 5mm in all limb leads); voltage slightly more elevated in precordial leads with a QRS complex > 10 mm in V3 and V4; pseudo-necrosis q wave pattern in V1-V2; repolarization disorders (flattened or negative T waves) in inferolateral leads;

Comments: This patient has AL amyloidosis with renal, digestive and cardiac disorder. Amyloidosis is an infiltrative disease, with cardiac manifestations related to wall infiltration by amyloid deposits within the interstitial myocardial area. The classification of amyloidoses is based on the biochemical nature of the amyloid protein involved in the formation of deposits, the most frequent cardiac forms being AL amyloidosis (immunoglobulin) and transthyretin amyloidosis.

The remarkable feature of this patient’s tracing is the presence of an electrical low voltage in contrast with the significant increase in the thickness of the ventricular myocardium observed on ultrasound. The electrocardiogram may orient towards the diagnosis of cardiac amyloidosis when a lack of electrical myocardial hypertrophy or even a low voltage contrasts with evidence of significant myocardial “hypertrophy” on echocardiography (increase in left ventricular wall thickness usually concentric with right ventricular thickening). This discordance can be expressed by the ratio between the thickness of the left ventricular wall and the voltage of the QRS complexes (sum of all of the amplitudes of the QRS complexes). The absence of an increase in amplitude of the QRS complexes can be explained by the absence of myocytic hypertrophy, the observed thickening being related to infiltration of the heart wall by the amyloid deposits without any increase in the size of myocardial cells. This electrocardiogram/ultrasound discrepancy is not found in all infiltrative heart diseases since electrical hypertrophy is common in Fabri disease or Danon disease. Some 30% to 50% of patients with cardiac amyloidosis have QRS complexes of normal amplitude, with low voltage observed in the remaining 50-70%.

Take-home message: The diagnosis of cardiac amyloidosis should be evoked when faced with any patient with significant ultrasound hypertrophy in contrast with the highlighting of QRS complexes of normal amplitude or of low voltage on the ECG.