Prolonged QT interval on electrocardiogram and fainting — is there always a relationship?

Abstract

Using a clinical example, the article draws the attention of doctors to the problem of the prolonged QT interval (“long QT”) and the related problem of fainting (syncope). Syncope is a component of long QT syndrome, and syncope is a precursor of sudden cardiac death. However, syncope in a patient with long QT syndrome may have pathogenesis that is completely unrelated to abnormalities of cardiac ion channels. In other words, such a patient may have a second disease as a syntropy relates to prolonged QT interval, to an extent mimicking long QT syndrome. The presented medical history of a 33-year-old patient S. shows the complexity of differential diagnosis of the causes of syncope. The crucial part in the diagnosis, in addition to the clinical picture, was the so-called “tilt test”, little-known to general medical practice, as well as the laboriousness of making a final diagnosis of the long QT Syndrome type 2, which required a molecular genetic study — whole-exome sequencing. Patient S. had vasovagal syncope that not associated with long QT syndrome, but she has a risk of sudden cardiac death, and the article identifies therapeutic and other measures to reduce this risk.

Keywords

long QT / syncope / tilt test / whole-exome sequencing

References

[1] Clinical guidelines “Long QT interval syndrome” (approved by the Ministry of Health of Russia). M. 2016. https://legalacts.ru/doc/klinicheskie-rekomendatsii-sindrom-udlinennogo-intervala-qt-utv-minzdravom-rossii/ (access date: 05.04.2021). (In Russ.)

[2] Клинические рекомендации «Синдром удлинённого интервала QT» (утв. Минздравом России). М. 2016. https://legalacts.ru/doc/klinicheskie-rekomendatsii-sindrom-udlinennogo-intervala-qt-utv-minzdravom-rossii/ (дата обращения: 05.04.2021).

[3] Clinical guidelines “Ventricular rhythm disturbances. Ventricular tachycardia and sudden cardiac death” (approved by the Russian Ministry of Health). M. 2020. https://bazanpa.ru/download/pdf/?target_url=/minzdrav-rossii-klinicheskie-rekomendatsii-ot01012020-h4961518/ (access date: 29.06.2021). (In Russ.)

[4] Клинические рекомендации «Желудочковые нарушения ритма. Желудочковые тахикардии и внезапная сердечная смерть» (утв. Минздравом России). М. 2020. https://bazanpa.ru/download/pdf/?target_url=/minzdrav-rossii-klinicheskie-rekomendatsii-ot01012020-h4961518/ (дата обращения: 29.06.2021).

[5] Shkol'nikova M.A., Chuprova S.N. Clinical and genetic polymorphism of hereditary syndrome of long QT interval, risk factors for syncope and sudden death. Vestnik aritmologii. 2002; (26): 35–42. (In Russ.)

[6] Школьникова М.А., Чупрова С.Н. Клинический и генетический полиморфизм наследственного синдрома удлинённого интервала QT, факторы риска синкопе и внезапной смерти. Вестн. аритмол. 2002; (26): 35–42.

[7] El-Sherif N., Turitto G., Boutjdir M. Congenital long QT syndrome and torsade de pointes. Ann. Noninvasive Electrocardiol. 2017; 22 (6): e12481. DOI: 10.1111/anec.12481.

[8] Mazzanti A., Maragna R., Vacanti G., Monteforte N., Bloise R., Marino M., Braghieri L., Gambelli P., Memmi M., Pagan E., Morini M., Malovini A., Ortiz M., Sacilotto L., Bellazzi R., Monserrat L., Napolitano C., Bagnardi V., Priori S.G. Interplay between genetic substrate, QTc duration, and arrhythmia risk in patients with long QT syndrome. J. Am. Coll. Cardiol. 2018; 71 (15): 1663–1671. DOI: 10.1016/j.jacc.2018.01.078.

[9] Richards S., Aziz N., Bale S., Bick D., Das S., Gastier-Foster J., Grody W.W., Hegde M., Lyon E., Spector E., Voelkerding K., Rehm H.L.; ACMG Laboratory Quality Assurance Committee. Standards and guidelines for the interpretation of sequence variants: a joint consensus recom­mendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet. Med. 2015; 17 (5): 405–424. DOI: 10.1038/gim.2015.30.

RIGHTS & PERMISSIONS

Eco-Vector