Post-transplant atrial tachyarrhythmias: Epidemiology, mechanisms, outcomes, and management across solid organs

Table 1 Organ-specific features of post-transplant atrial tachyarrhythmias

Organ	Typical burden of AF/atrial arrhythmias	Dominant early mechanisms	Dominant late mechanisms	Main clinical impact	Key management caveats
Heart	(1) Lower AF incidence than other thoracic procedures; and (2) But clinically meaningful atrial arrhythmia burden overall	(1) Perioperative inflammation; (2) Atrial suture lines and altered atrial geometry; and (3) Rejection and ischemia	(1) Scar-related reentry; (2) Rejection-related remodeling; and (3) Cardiac allograft vasculopathy	(1) Worse early and intermediate outcomes; and (2) May signal graft dysfunction rather than isolated rhythm disease	(1) Evaluate promptly for rejection or ischemia; (2) DOACs are increasingly feasible; and (3) Ablation is effective for organized arrhythmias
Lung	(1) Highest thoracic burden; (2) Early AF is common; and (3) Late flutter or atrial tachycardia is frequent	(1) Postoperative stress; (2) Atrial stretch and ischemia; and (3) Vasopressors and recipient comorbidity	(1) Anastomotic scar and low-voltage substrate; (2) Pulmonary vein reconnection; and (3) Macroreentry	(1) Prolonged hospitalization; and (2) Worse long-term outcomes in several series	(1) Amiodarone use is debated because of pulmonary toxicity; and (2) Ablation is a major option for late organized arrhythmias
Kidney	(1) Lower incidence than thoracic transplantation; and (2) But strong prognostic relevance	(1) Reperfusion stress; (2) Steroids and electrolyte shifts; and (3) Hemodynamic instability	(1) CKD substrate, including fibrosis and left ventricular hypertrophy; (2) Autonomic dysfunction; and (3) Persistent immunosuppressive effects	(1) Mortality, stroke, and graft loss; and (2) Longer hospitalization	(1) Early graft-function fluctuation complicates DOAC dosing; and (2) Calcineurin inhibitor interactions are clinically important
Liver	(1) Intermediate burden; and (2) Strongly linked to disease severity and perioperative instability	(1) Cirrhotic cardiomyopathy; (2) Autonomic dysfunction; and (3) Post-reperfusion syndrome	(1) Persistent metabolic and hemodynamic vulnerability; and (2) Chronic cardiovascular stress	(1) Acute kidney injury and graft dysfunction; (2) Prolonged intensive care unit stay and mortality; and (3) Later thromboembolism	(1) Anticoagulation is complicated by thrombocytopenia and unstable liver function; and (2) Amiodarone hepatotoxicity is a concern

AF: Atrial fibrillation; CKD: Chronic kidney disease; DOAC: Direct oral anticoagulant.

Table 2 Key drug-drug interactions involving amiodarone and immunosuppressants

Interacting immunosuppressant	Mechanism	Clinical action
Cyclosporine	CYP3A4/P-gp inhibition may increase cyclosporine exposure and nephrotoxicity	Check trough levels after starting or stopping amiodarone; monitor creatinine, BP, K/Mg, and QTc; reduce dose if needed
Tacrolimus	CYP3A4/P-gp inhibition may increase tacrolimus exposure; additive QT prolongation is clinically relevant	Use early frequent trough monitoring, ECG/QTc and renal assessment; correct K/Mg; consider dose reduction in high-risk patients
Sirolimus/everolimus	mTOR inhibitors are CYP3A4/P-gp substrates; exposure and toxicity may increase	Coordinate with transplant pharmacy; adjust to troughs; monitor cytopenias, lipids, proteinuria, wound healing, and liver function

CYP3A4: Cytochrome P450 3A4; P-gp: P-glycoprotein; mTOR: Mammalian target of rapamycin; BP: Blood pressure; K: Potassium; Mg: Magnesium; QTc: Corrected QT interval; ECG: Electrocardiogram.