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Monitoring of the QT Interval in Perioperative and Critical Care

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An advance in perioperative and critical care for patients with Long QT Syndrome (LQTS)1

Long QT syndrome (LQTS) is characterized by prolongation of the QT interval in the electrocardiogram and polymorphic ventricular tachycardia known as Torsades de pointes (TdP). LQTS can either be inherited or acquired; both forms lead to altered ion channel function and impaired repolarization of ventricular action potentials.

Acquired LQTS is typically caused by interaction between a wide variety of drugs with HERG potassium channels. These include several frequently used in perioperative and critical care, such as volatile anesthetics, antibiotics, antiemetics and antipsychotic agents. During perioperative and critical care, patients with acquired or inherited LQTS may be at increased risk of developing malignant cardiac arrhythmia such as R on T phenomena and TdP. The latter may lead to syncope and sudden cardiac death. 

The perioperative management of patients with LQTS is challenging, and there is a need for standardized treatment. The administration of several drugs including droperidol to LQTS patients requires monitoring of the QT interval. Thus monitoring of the QT interval throughout the perioperative process forms an integral part of current recommendations for standardized treatment.

This paper describes the QT interval and the challenges to its measurement, especially in perioperative and critical care. Manual measurement of the QT interval has been found too consuming for monitoring purposes and is likely unfeasible under the time constraints and  multi-tasking requirements of the OR and critical care unit.

Two recent case reports demonstrate the feasibility of automatic determination of the QT interval in perioperative care. Algorithms requiring 12-lead ECG recordings and a reduced- lead QT analysis requiring five electrodes are available. Today, patients with congenital and acquired LQTS, or at risk of acquiring LQTS during drug treatment, can easily be monitored for QT analysis with automatic algorithms during perioperative and critical care.

1 Professor Dr. Med. Patrick Friederich, Chairman, Department of Anaesthesiology, Critical Care Medicine, Pain Therapy, Klinikum Bogenhausen Academic Hospital of Technische Universität München

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