LQT3 with SCN5A Mutation and Prolonged QT Interval: When Initial Therapy Fails to Achieve Adequate QTc Shortening

This protocol addresses patients with long QT syndrome type 3 (LQT3) carrying an SCN5A pathogenic mutation and a prolonged QT interval on 12-lead ECG — a genetically defined subgroup requiring a specific therapeutic approach.

When the previous approach is insufficient

First-line management for this population consists of general risk-reduction measures (avoiding QT-prolonging drugs, correcting electrolyte abnormalities, avoiding genotype-specific triggers) combined with beta-blockers and mexiletine as genotype-specific therapy. This regimen is considered to have not met its primary goal when oral mexiletine testing fails to shorten the QTc interval by 40 ms. The present protocol defines the next clinical step for that situation.

Next-line approach (partial overview)

For LQT3 patients in whom the initial pharmacological regimen has not achieved the required QTc response, the next step involves a device-based intervention alongside continued pharmacological therapy. The complete decision sequence and structured regimen are available in the full protocol.

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References

DOI: 10.1093/eurheartj/ehac262

Mexiletine is indicated in LQT3 patients with a prolonged QT interval.

ICD implantation is recommended in patients with LQTS who are symptomatic while receiving beta-blockers and genotype-specific therapies.

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