Ventricular Arrhythmias in Cardiac Amyloidosis

Ventricular arrhythmias in cardiac amyloidosis are clinically important because they may herald advanced myocardial infiltration, yet their management is shaped by competing risks, comorbidity and limited trial evidence. The two major systemic phenotypes are AL amyloidosis, usually driven by an abnormal light-chain protein, and transthyretin amyloidosis (ATTR), which may be wild-type or hereditary. Both can cause myocardial thickening, diastolic dysfunction, conduction disease and sudden cardiac death; AL also requires urgent haematological treatment.

Prevalence estimates vary with phenotype, ambulatory monitoring duration and the definitions used for non-sustained tachycardia. A practical response therefore combines structured rhythm assessment with amyloid-specific prognostic context rather than treating ventricular ectopy as an isolated ventricular problem. Diagnosis, device decisions and follow-up also need to account for the different trajectories of AL, hereditary ATTR and wild-type ATTR.

Prevalence and disease phenotype

Published cohorts suggest that premature ventricular complexes occur in roughly one-third to one-half of patients with AL or ATTR, while non-sustained ventricular tachycardia has been reported in about 20–40%. Sustained ventricular tachycardia or ventricular fibrillation is less frequent but carries a serious prognosis. These ranges remain broad because Holter duration, ventricular burden thresholds, ejection fraction and disease stage differ considerably between studies.

The phenotypes have different clinical patterns. Wild-type ATTR usually affects older adults and may be recognised through conduction disease, atrial fibrillation or a hypertrophic cardiomyopathy phenotype. Hereditary ATTR often presents earlier and may involve neuropathy, autonomic dysfunction or cardiomyopathy. AL can progress rapidly, with arrhythmia occurring alongside renal, neurological, haematological and soft-tissue manifestations that influence both treatment urgency and device eligibility.

Ventricular arrhythmia burden does not map neatly onto the severity of structural disease. Extensive infiltration may produce marked wall thickening and low voltage on the electrocardiogram, yet relatively few early ventricular events. Conversely, non-sustained tachycardia can accompany advanced fibrosis, worsening haemodynamics and poor prognosis. The Journal of Arrhythmia provides relevant electrophysiology evidence, reviews and educational resources for interpreting these findings.

Predictors of arrhythmic risk

Several electrocardiographic features raise concern, although none independently determines the need for an implantable cardioverter-defibrillator. Low voltage despite increased ventricular wall thickness, pseudo-infarction patterns, conduction delay and progressive QRS widening are characteristic clues. Atrial fibrillation, frequent premature ventricular complexes and a high ventricular ectopic burden also indicate advanced electrical disease. Ambulatory monitoring is useful when symptoms are intermittent, but a normal short recording does not exclude clinically important ectopy.

Cardiac magnetic resonance imaging adds information about tissue burden and prognosis. ATTR typically produces diffuse subendocardial or transmural late gadolinium enhancement, whereas AL more often has patchy subendocardial or transmural patterns. Extensive enhancement, diffuse fibrosis and adverse ventricular remodelling are associated with a poorer outlook. Apical sparing is a recognised marker of comparatively favourable survival in ATTR, but it should not be interpreted as complete protection from arrhythmia.

Clinical variables provide further context: age, male sex, reduced ejection fraction, renal impairment, rising troponin or NT-proBNP, orthostatic intolerance and previous syncope. Ventricular arrhythmias frequently occur alongside atrial fibrillation, progressive heart failure and neurological or haematological decline. No amyloid-specific score currently combines these variables into a validated device-selection threshold, and the apparent prognostic effect of non-sustained tachycardia can diminish after adjustment for disease severity.

Device indications in practice

Before considering implantation, clinicians should confirm the amyloid phenotype where possible and exclude reversible contributors such as myocardial ischaemia, electrolyte disturbance, thyroid dysfunction, infection, dehydration or medication toxicity. In AL, treatment of the underlying plasma-cell disorder is urgent and may improve haemodynamics and arrhythmia frequency. Device implantation should complement, rather than delay, disease-directed therapy.

For secondary prevention, an implantable cardioverter-defibrillator is generally more defensible when sustained ventricular tachycardia or ventricular fibrillation has occurred, reversible causes have been excluded, and anticipated survival and quality of life remain acceptable. Primary prevention is more difficult. Randomised evidence is limited, ejection fraction alone performs poorly in amyloidosis, and many deaths arise from progressive pump failure, infection, stroke or neurological deterioration rather than ventricular tachycardia. Competing risk therefore belongs at the centre of the decision, not at its edge.

Pacemakers are appropriate for symptomatic bradycardia or advanced atrioventricular block when prognosis and goals align. Amyloid can make lead placement technically difficult because of RV fragility, poor electrical signals and future lead displacement. Leadless pacing may reduce pocket and lead complications, although battery life, retrievability and availability through Australian distributors require consideration. Cardiac resynchronisation may help selected patients with reduced ejection fraction, sinus rhythm and a suitable wide-QRS conduction pattern, particularly with left bundle branch block, but supporting evidence is largely extrapolated from other cardiomyopathies.

Catheter ablation may be considered for symptomatic monomorphic ventricular tachycardia or recurrent atrial flutter in selected patients. Scar-related circuits can be targeted, yet extensive amyloid infiltration increases mapping and procedural difficulty. Antiarrhythmic drugs require careful attention to bradycardia, hypotension, renal clearance and QT prolongation; amiodarone is often used for recurrent ventricular arrhythmia, while sotalol may be unsuitable in advanced structural disease. For atrial fibrillation, anticoagulation decisions should combine standard stroke-risk assessment with amyloid-specific bleeding risk, especially in AL.

The Australian care pathway

Specialist assessment is concentrated in major centres in Melbourne, Sydney, Brisbane and Adelaide, with many patients travelling considerable distances for cardiac imaging, haematology, neurology and electrophysiology. These urban services support multidisciplinary discussion, while regional patients may face delayed access, travel costs and difficulty attending repeated device checks. For education and evidence synthesis, the journal’s themed collections can support local journal clubs and clinician meetings.

Australian practice combines Medicare rebates for eligible procedures with private-insurance funding for many implantable-device services, and actual out-of-pocket costs depend on the insurer, hospital and device. A recognised Australian clinical custom is multidisciplinary review for complex cardiac infiltrative disease, bringing together electrophysiology, heart failure, imaging, neurology, haematology and geriatrics. This approach helps distinguish an arrhythmia that requires a device from one reflecting systemic deterioration or medication intolerance.

Devices are regulated by the Therapeutic Goods Administration and supplied through Australian distributors and hospital procurement pathways. Local product availability, warranty support and access to experienced implanting teams can therefore influence leadless pacing, defibrillator or resynchronisation choices. Culturally safe communication, interpreter support and Aboriginal and Torres Strait Islander health expertise should be incorporated into consent discussions. For patients living outside metropolitan areas, remote device transmission and structured telephone follow-up are important components of safe long-term management.

Integrating risk with patient-centred decisions

Device therapy begins by comparing three separate questions: how likely is a lethal ventricular event, how long is meaningful survival likely to remain, and would the intervention improve the patient’s experience? Frailty, cognition, renal function, autonomic neuropathy, mobility and the pace of AL or ATTR progression may be more influential than an isolated ejection-fraction cut-off. A patient may value symptom relief and reliable rhythm control more than protection from sudden death, while another may prioritise defibrillator protection despite substantial procedural burden.

For primary prevention, the record should explain why expected survival is sufficient, which prognostic features support the decision, and how competing mortality risks were addressed. For secondary prevention, clinicians should document the arrhythmia, exclude reversible causes and confirm that shock delivery remains consistent with the patient’s goals. Informed consent must also cover generator replacement, future procedures, infection and the possibility that an implanted device will never provide benefit.

Multidisciplinary follow-up should reassess rhythm burden, conduction disease, heart failure symptoms and device complications as the underlying disease evolves. Medication review, management of orthostasis and coordination with the amyloid team are integral rather than secondary tasks. Device checks must remain accessible for regional patients, with clear plans for urgent assessment when shocks, syncope, worsening dyspnoea or infection occurs.

For Australian clinicians and trainees, act now to recognise cardiac amyloidosis in patients with unexplained ventricular ectopy, conduction disease or disproportionate wall thickening, obtain prompt amyloid phenotyping, and involve an electrophysiologist when syncope, sustained tachycardia or advanced conduction disease appears. Pair every device decision with an explicit assessment of arrhythmic risk, competing health risks and the priorities that define meaningful survival for that patient.