EP Consult and Ablation for IST with Suspected Hashimoto's Thyroiditis
An EP consult and ablation should NOT be pursued at this time; instead, prioritize treating the newly identified Hashimoto's thyroiditis as the reversible cause of her symptoms, and continue medical management with propranolol while awaiting endocrinology evaluation. 1
Rationale: Address Reversible Causes First
The ACC/AHA/HRS guidelines explicitly state that evaluation for and treatment of reversible causes are Class I (strongest) recommendations in patients with suspected IST. 1 This patient has:
- Elevated thyroid peroxidase antibodies (406) and antithyroglobulin antibodies (31) consistent with Hashimoto's thyroiditis 2
- Hyperthyroidism can cause physiological sinus tachycardia that mimics IST, and the guidelines emphasize distinguishing IST from secondary causes including hyperthyroidism 1
- Even with "normal" thyroid function tests, Hashimoto's can present with sinus tachycardia 2
Why Ablation Is Not Appropriate Now
Catheter ablation for IST has significant limitations and risks that make it inappropriate as anything other than a last resort:
- Modest efficacy: Acute success rates of 76-100% but symptomatic recurrence occurs in up to 45% of patients, with IST recurrence in 27% 1
- Significant complications include:
- Symptomatic bradycardia requiring permanent pacemaker placement
- Phrenic nerve injury with hemidiaphragm paralysis
- Superior vena cava syndrome 1
- Guidelines state ablation should only be considered for highly symptomatic patients who cannot be adequately treated by medication, and only after informing patients that risks may outweigh benefits 1
Current Clinical Status Does Not Support Ablation
This patient's presentation argues against ablation:
- Event monitor showed symptoms did NOT correlate with heart rhythm disturbances - her 32 patient triggers correlated with sinus rhythm or sinus tachycardia, not true arrhythmias [@case presentation@]
- She reports alprazolam is "helping quite a bit", suggesting an anxiety component that would not be addressed by ablation [@case presentation@, 1]
- She has not exhausted medical therapy - she was unable to tolerate ivabradine but is currently on propranolol 80 mg daily, and combination therapy with beta blockers and ivabradine may be considered 1
- The prognosis of IST is generally benign, with treatment aimed at symptom reduction rather than mortality/morbidity prevention 1
Recommended Management Algorithm
Step 1: Complete endocrinology evaluation and treat Hashimoto's thyroiditis
- Thyroid dysfunction (even subclinical) can resolve tachycardia symptoms entirely 2, 3
- Sinus tachycardia secondary to thyroid disease typically resolves with correction of the underlying cause 1
Step 2: Optimize medical management while awaiting thyroid treatment response
- Continue propranolol 80 mg daily (Class IIb recommendation for IST) 1
- Consider retrial of ivabradine at lower doses (Class IIa recommendation, strongest medical therapy for IST) 1
- Ivabradine has been successfully used for hyperthyroidism-induced sinus tachycardia resistant to beta blockers 4, 3
- Continue alprazolam for anxiety component 1, 5
Step 3: Reassess after 3-6 months of thyroid treatment
- If symptoms persist despite optimized thyroid management and maximal medical therapy, THEN consider EP referral 1
Critical Pitfall to Avoid
Do not pursue invasive procedures before excluding and treating reversible causes - this is the most common error in IST management. 1 The guidelines are explicit that IST is a diagnosis of exclusion, and this patient has an identifiable, treatable thyroid disorder that must be addressed first. 1