EP Q&A; Q6

A 31 year-old woman presents with dizziness and syncope while talking on the phone. She had been otherwise healthy and had not been on any medications or supplements. Physical examination is unremarkable. Supine and upright BPs are 110/85 and 125/80 mmHg respectively. ECG is as shown. While being monitored in an emergency room, occasional PVCS were noted. Patient complains of no symptoms. Bedside echocardiogram shows normal study. Blood work for electrolytes and thyroid function is within normal ranges.

What is the best next step?

Implant a dual chamber pacemaker.
Implant a single chamber ICD.
Start beta-blocker.
Electrophysiologic study and possible ICD implantation.
Lifestyle modification.

Show Answer

Answer: C

EKG shows sinus rhythm with prolong QT interval. In this patient, there is no other reversible causes for prolong QT. Congenital long QT syndrome (LQTs) is highly likely.
According to the 2017 ACC guidelines for SCA, beta blocker (esp nadolol) is the first line in the symptomatic LQTs including the survivor of SCA, before ICD.
Lifestyle modification includes avoiding drugs that prolong QT, avoiding high fevers, and attention to maintain normal level of potassium and magnesium.
EP study has no role in long QT syndrome.

Exercise Treadmill Testing in LQTs

Exercise or standing increases QT interval in LQTs.
Helpful in diagnosis in a highly suspected case with borderline QT at rest (IIa).
Helpful in monitoring the response to BB therapy (IIa).

Role of EP study in SCA risk stratification

ICM, NICM, ACHD with syncope who does not meet indication for ICD for primary prevention.
Not useful in cardiac channelopathies (LQTs, SQTs, CPVT, HCM, or Early repolarization).
In asymptomatic ARVD, EP study may be considered for risk stratification (IIb).

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