Cardiac amyloidosis

ECG 2A: Different electrical signs are suggestive of the presence of cardiac amyloidosis; atrial fibrillation with slowed atrioventricular conduction in the absence of rate-controlling treatment (attesting to an atrioventricular conduction disorder); clearly low-voltage QRS in limb leads (< 5mm in all limb leads); voltage slightly more elevated in precordial leads although no lead with an amplitude > 10 mm; QRS axis deviated to the right (136°); pseudo q wave pattern (V1-V2) with poor anterior R wave progression;

ECG 2B: Tracing recorded after performing an external electric shock; sinus rhythm, with long PR pattern (first degree AV block);

Comments: This patient presented a myeloma complicated with AL-type cardiac amyloidosis with evocative electrical signs inconsistent with ultrasound ventricular hypertrophy. The electrocardiogram is abnormal in 90% of amyloidosis patients with cardiac involvement. The two most commonly observed abnormalities are low voltage QRS complexes and a pseudo-infarct pattern in precordial leads with Q waves and poor R wave progression. It is also common to observe repolarization disorders, conduction disorders or rhythm disturbances.

• low QRS voltage; there are various definitions, the most common being the absence of a limb lead with a QRS amplitude exceeding 5 mm and the absence of a precordial lead with a QRS amplitude exceeding 10 mm; in amyloidosis, the low voltages are mainly observed in the frontal leads with a possible right axis deviation (as in this patient) or left axis deviation; the presence of low voltages on the electrocardiogram associated with a significant increase in the thickness of the ventricular walls on ultrasound is evocative of an amyloidosis-type infiltrative disease; the absence of low voltage does not eliminate the diagnosis of cardiac disease, the sensitivity of this sign varying according to the type of amyloidosis (more common in AL amyloidosis); moreover, a relatively large number of patients with amyloidosis have undergone implantation of a pacemaker or a defibrillator, with ventricular pacing rendering the electrocardiogram uninterpretable in terms of the amplitude of the QRS complexes;
• Q-waves suggestive of necrosis are observed in approximately half of cases, most often in the anteroseptal territory (somewhat less frequently in the lateral and inferior leads); the sensitivity of this electrical sign also varies depending on the type of amyloidosis (more common in AL amyloidosis);
• Poor R wave progression in the precordium;
• Repolarization (diffuse or lateral) disorders with flattening or inversion of T waves can be observed; the association between q waves and negative T waves can lead to a misdiagnosis of ischemic cardiomyopathy;
• Supraventricular rhythm disorders (fibrillation or atrial flutter) may be observed (very common in senile amyloidosis) even if a majority of patients remain in sinus rhythm with a widened and low voltage P wave pattern; extensive atrial disease can reduce the amount of myocardium required to support the perpetuation of atrial arrhythmia; even at sinus rhythm, atrial contractility can be altered with evidence of atrial thrombi in sinus rhythm patients (electromechanical dissociation);
• The presence of polymorphic ventricular extrasystoles is a factor of poor prognosis and associated with an increase in mortality;
• Conduction disorders (long PR, branch block, high grade atrioventricular block) are relatively common, reflecting the presence of amyloid deposits in the myocardium but also in conduction pathways; an altered atrioventricular conduction explains the very rapid ventricular rate during an episode of atrial fibrillation;

Take-home message: In a patient with cardiac amyloidosis, it is common to observe various,  electrocardiographic signs in discordance with the echocardiographic pattern: low voltage, pseudo-necrosis q waves, repolarization disorders, rhythm disturbances or conduction disorders.