Monitoring Patients With BTM for AFib

The prevalence of AFib in patients with BTM is expected to continue increasing. The authors of the study warned that physicians should be aware of AFib and how to treat it. They suggested monitoring patients with active screening “even when cardiac function still appears normal,” allowing early detection of AFib at its onset.

Active screening for AFib in patients with BTM includes (1) reviewing the patient’s history of iron overload and associated disorders, such as thyroid disease; and (2) conducting and checking 12-lead electrocardiograms, 24-Holter electrocardiograms, and echocardiographs for characteristics related to the onset of AFib.

If a patient has a high number of risk factors, follow-up with an external or internal loop recorder should be considered.

Treating AFib in Patients With BTM

The cornerstone of treatment for patients with BTM is iron chelation therapy. When patients have acute iron overload or their iron plasmatic levels are not regularly controlled, they are at risk for developing AFib.

If an AFib diagnosis is made, 4 primary therapeutic considerations should be made:

  • Rate control. Due to the risk of heart failure and the highly symptomatic nature of AFib in patients with BTM, who tend to be relatively young at AFib onset, heart rate control is often necessary. Rate control may be achieved through the use of calcium antagonists and beta blockers, with lower doses recommended in patients with a history of heart failure or Doppler abnormalities. Digoxin may also be used in patients with low T2* values or impaired ejection fractions.
  • Rhythm control. After rate control is achieved, rhythm control may be pursued with antiarrhythmic therapy. The team noted that few studies have evaluated the use of antiarrhythmic medications for controlling AFib in patients with BTM and that, at this time, treatment of patients with BTM should not differ from recommended treatment for the general population. Amiodarone has previously been used in combination with iron chelation therapy to control atrial arrhythmias. However, arrhythmia may be associated with iron-mediated thyroid injury, and this should be considered when choosing medications.
  • Anticoagulant therapy. Patients with BTM have higher thrombotic risk than nonthalassemic populations.9 Therefore, anticoagulation therapy is generally recommended but should only be initiated after a risk/benefit ratio assessment has been conducted. Bleeding risk can be assessed by testing liver function, platelet count, and renal function; CHA2DS2-VASc and HAS-BLED scores should also be considered. The authors noted that warfarin is the most commonly used anticoagulant.
  • Catheter ablation therapy. The authors recommend early referral for an ablation procedure if a patient’s AFib cannot be successfully controlled with medications. Catheter ablation indications for patients with BTM are the same as those for the general population. While no studies exist that measure the success rate of AFib ablation in patients with BTM, it ranges from 70% to 80% in nonthalassemic patients.10

Above all else, iron chelation therapy is critical for arrhythmia management in patients with BTM. After achieving regular, successful chelation, and if AFib persists, treatment of AFib should be pursued at an early stage to avoid complex remodeling of the atria.

References

1. Cappellini MD, Cohen A, Porter J, Taher A, Viprakasit V. Guidelines for the Management of Transfusion Dependent Thalassaemia (TDT). 3rd ed. Nicosia (CY): Thalassaemia International Federation; 2014.

2. Williams TN, Weatherall DJ. World distribution, population genetics, and health burden of the hemoglobinopathies [published online September 1, 2012]. Cold Spring Harb Perspect Med. doi: 10.1101/cshperspect.a011692

3. Barbero U, Fornari F, Guarguagli S, et al. Atrial fibrillation in β-thalassemia major patients: diagnosis, management and therapeutic options [published online Oct 1, 2018]. Hemoglobin. doi: 10.1080/03630269.2018.1488724

4. Taher AT, Cappellini MD. How I manage medical complications of beta-thalassemia in adults [published online October 25, 2018]. Blood. doi: 10.1182/blood-2018-06-818187

5. Coumel P. Cardiac arrhythmias and the autonomic nervous system. J Cardiovasc Electrophysiol. 1993;4(3):338-355.

6. Kuryshev YA, Brittenham GM, Fujioka H, et al. Decreased sodium and increased transient outward potassium currents in iron-loaded cardiac myocytes. Circulation. 1999;100(6):675-683.

7. Buja LM, Roberts WC. Iron in the heart. Am J Med. 1971;51(2):209-221.

8. Pennell DJ, Udelson JE, Arai AE, et al. Cardiovascular function and treatment in β-thalassemia major. Circulation. 2013;128(3):281-308.

9. Taher A, Mehio G, Isma’eel H, Cappellini MD. Stroke in thalassemia: A dilemma. Am J Hematol. 2008;83(4):343.

10. Gaita F, Scaglione M, Battaglia A, et al. Very long-term outcome following transcatheter ablation of atrial fibrillation. Are results maintained after 10 years of follow up? EP Eur. 2018;20(3):443-450.