While less common, Jervell and Lange Nielson syndrome is an autosomal recessive form of LQTS in which affected patients have homozygous mutations in the KCNQ1 or KCNE1 genes. This syndrome occurs in approximately 1% to 7% of LQTS patients, displays a typical QTc >550 ms, can be triggered by exercise and emotional stress, is associated with deafness, and carries a high risk of cardiac events at a young age.6
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Acquired Syndromes
In addition to congenital LQTS, certain patients can acquire LQTS after being treated with particular drugs or having metabolic abnormalities, namely hypomagnesemia, hypocalcemia, and hypokalemia. Most experts think patients who “acquire” LQTS that predisposes to torsades de pointes have underlying structural heart disease or LQTS genetic carrier mutations that combine with transient initiating events (e.g., drugs or metabolic abnormalities) to induce dysrhythmias.1 In addition to certain drugs, cardiac ischemia, and electrolyte abnormalities, cocaine abuse, HIV, and subarachnoid hemorrhage can induce dysrhythmias in susceptible patients.5
Many types of drugs can cause a prolonged QT interval, and others should be avoided in patients with pre-existing prolonged QT (see Table 3, p. 17). Potentially offending drugs that are frequently encountered by inpatient physicians include amiodarone, diltiazem, erythromycin, clarithromycin, ciprofloxacin, fluoxetine, paroxetine, sertraline, haloperidol, ritonavir, and methadone.1 Additionally, drugs that cause electrolyte abnormalities (e.g., diuretics and lithium) should be monitored closely.
Overall, the goals of therapy in LQTS are:
- Decrease the risk of dysrhythmic events;
- Minimize adrenergic response;
- Shorten the QTc;
- Decrease the dispersion of refractoriness; and
- Improve the function of the ion channels.3
Supportive measures should be taken for patients who are acutely symptomatic from LQTS and associated torsades de pointes. In addition to immediate cardioversion for ongoing and hemodynamically significant torsades, intravenous magnesium should be administered, electrolytes corrected, and offending drugs discontinued.5 Temporary transvenous pacing at rates of approximately 100 beats per minute is highly effective in preventing short-term recurrence of torsades in congenital and acquired LQTS, especially in bradycardic patients.5 Isoproterenol infusion increases the heart rate and effectively prevents acute recurrence of torsades in patients with acquired LQTS, but it should be used with caution in patients with structural heart disease.5
Long-term strategies to manage LQTS include:
- Minimizing the risk of triggering cardiac events via adrenergic stimulation;
- Preventing ongoing dysrhythmias;
- Avoiding medications known to prolong the QT interval; and
- Maintaining normal electrolytes and minerals.5
Most patients with congenital long QT should be discouraged from participating in competitive sports, and patients should attempt to eliminate exposures to stress or sudden awakening, though this is not practical in all cases.5 Beta blockers generally are the first-line therapy and are more effective for LQT1 than LQT2 or LQT3.4,5 If patients are still symptomatic despite adequate medical therapy, or have survived cardiac arrest, they should be considered for ICD therapy.4,5 In addition, patients with profound bradycardia benefit from pacemaker implantation.5 Patients who remain symptomatic despite both beta blockade and ICD placement might find cervicothoracic sympathectomy curative.4,5
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Perioperative Considerations
Although little data is available to guide physicians in the prevention of torsades de pointes during the course of anesthesia, there are a number of considerations that may reduce the chances of symptomatic dysrhythmias.
First, care should be taken to avoid dysrhythmia triggers in LQTS by providing a calm, quiet environment during induction, monitoring, and treating metabolic abnormalities, and providing an appropriate level of anesthesia.10 Beta-blocker therapy should be continued and potentially measured preoperatively by assessing heart rate response during stress testing.5 An implantable cardioverter-defibrillator (AICD) should be interrogated prior to surgery and inactivated during the operation.5
Finally, Kies et al have recommended general anesthesia with propofol for induction (or throughout), isoflurane as the volatile agent, vecuronium for muscle relaxation, and intravenous fentanyl for analgesia when possible.10