We thank Dr. Brown for his interest in our article, and for his thoughtful comments.
It is true that there are very few case reports of subjects with LQTS who had documented arrhythmia-related complications from dental interventions, but this does not imply that such dental procedures do not produce potentially life-threatening rhythm disorders in high-risk LQTS patients.
To date, children and adolescents with LQTS, who are viewed as the highest-risk population, may have empirically received their dental treatment in a hospital, at the request of either their cardiac specialist or the dentist providing care. It also is important to reconsider previously documented medical emergencies, such as neurocardiogenic syncope and seizure within the dental office, as these cases may represent misdiagnosed LQTS-mediated events.
We propose a comprehensive medical work-up for all patients with a personal or family history suspicious for LQTS. It is important to remember that a large percentage of symptomatic patients are children and adolescents.
The other important aspect of this condition is that cardiac events primarily occur in structurally normal hearts. In other words, pediatric patients who remain asymptomatic commonly go undiagnosed prior to sustaining their first cardiac event. Unfortunately, this first event is fatal in many cases. Therefore, cardiac events such as syncope and seizures must not be discounted as benign processes in all cases. Recent syncope is a troublesome symptom, and in those with LQTS, it indicates a high-risk situation. In fact, 20 percent of untreated LQTS patients presenting with syncope will die within one year, and 50 percent within 10 years.1
As such, it is prudent to view unexplained syncope, syncope during exertion and seizures in children and adolescents as LQTS-mediated cardiac events until proven otherwise.2,3 Cardiovascular work-up, including an electrocardiogram with assessment of the heart rate-corrected QT interval and, in some cases, genetic testing, is recommended to verify, or rule out, LQTS as the mediator for loss of consciousness.
We agree with Dr. Brown that drug interactions leading to QT prolongation should be avoided, as torsades de pointes arrhythmia can occur. Also, we stress that patients with LQTS should diligently avoid any drugs known to prolong the QT interval. Amiodarone is an infrequently used anti-arrhythmic drug in cardiac patients, and it generally is reserved for those with serious underlying structural heart disease. Comments about amiodarone are not relevant to the LQTS article.
Epinephrine-containing local anesthetics have never been shown to be safe and effective for patients with LQTS. Patients with LQT1 gene mutation are particularly susceptible to the effects of epinephrine on the QT interval. In fact, epinephrine infusion at a dose of less than 0.1 microgram per kilogram per minute has been shown to increase the QT interval of LQT1 patients from 440 to 530 milliseconds.4
Thus, a male teenager with LQTI who weights 70 kilograms may experience QT prolongation and be at an increased risk of experiencing a cardiac event in response to less than one-half of a cartridge of dental local anesthetic containing 1:100,000 epinephrine delivered into the systemic circulation. Considering that about 43 percent of LQTS patients demonstrate the LQT1 form of the disorder,5 it is prudent to avoid local anesthetics with epinephrine in those with LQTS.
In summary, we must not discount the impact of LQTS on dental care simply because of its poor documentation in the past. Dentists should not be required to diagnose LQTS with our current level of knowledge in the field of cardiac electro-physiology. We must, however, remain aware of suspicious findings in our patient’s medical history and properly inform our medical colleagues of our findings prior to providing dental treatment.
The dental profession, as a whole, must increase its level of knowledge with regard to LQTS, and we must work in greater collaboration with our patients’ primary care physicians and cardiac specialists not only to prevent cardiac events in the dental office, but also to increase early referral and diagnosis of patients with latent LQTS.
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