Treatment of patients with LQTS can be divided into short-term and long-term strategies. Short-term strategies include immediate management of unstable rhythms (torsade de pointes), regardless of the specific etiology of the QT prolongation. Immediate treatment with magnesium sulfate is the agent of choice for all forms of LQTS. This is frequently accompanied by potassium chloride, even in patients for whom the serum potassium level is only in the lower range of normal. In acquired LQTS, withdrawal of the offending agent and/or electrolyte repletion is often all that is necessary to prevent recurrences in most patients. The exception is in patients with sick sinus syndrome or atrioventricular blocks in which a pause or bradycardia precipitates torsades de pointes. These patients require permanent pacemakers. In contrast, all patients with congenital LQTS require long-term treatment.
The cornerstone of therapy is life-long adrenergic blockade with beta-blockers, which reduces the risk for arrhythmia. In some patients, beta-blockers may also shorten the QT interval. Propranolol and nadolol are the two most commonly prescribed beta-blockers. These patients should also avoid any drugs that are known to prolong the QT interval or those that reduce serum potassium or magnesium levels. Advice is mixed regarding whether all asymptomatic patients should be treated with beta-blockers, or just those at high risk for an acute cardiac event.
In cases refractory to adrenergic blockade, several additional, more aggressive measures are also available. Left thoracic sympathectomy may be used in conjunction with beta-blockers to provide increased adrenergic blockade. The permanent implantation of a pacemaker or cardiac defibrillator has been effective in reducing the incidence of sudden cardiac death in high-risk patients. In certain subtypes of LQTS, patients are advised to avoid strenuous activity, in particular swimming or diving.
At this time, there are no established gene-specific therapies widely in use, although several treatment modalities are under investigation in both limited human trials and animal models. All family members of those patients with suspected LQTS are encouraged to be screened by an ECG, but not by genetic testing. Genetic testing is not extensive enough to cover all potential mutations at this time, and it is reserved mainly as a research tool.
The patient in this case was admitted to a cardiac telemetry unit after a discussion with the on-call cardiologist for further evaluation and management. On the basis of her family history, clinical story, and lack of any medications known to prolong QT intervals, she was suspected to have a congenital adrenergic-dependent form of LQTS. Beta-blocker therapy was initiated while in the hospital. An extensive discussion about the long-term risks associated with LQTS occurred between the patient and the cardiologist during her admission, and she was additionally offered a defibrillator and further outpatient ambulatory telemetry monitoring. She was discharged to home to be followed up by her primary care provider and an outpatient cardiologist in order to assess her response to the initiation of therapy. Other members of her family, in particular her brother, were encouraged to seek consultation for LQTS.
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