Long QT Syndrome Type 1 and 2 Patients Respond Differently to Arrhythmic Triggers – The TriQarr In Vivo Study

Peter Marstrand, Kasim Almatlouh, Jørgen K. Kanters, Claus Graff, Alex Hørby Christensen, Henning Bundgaard, Juliane Theilade

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In patients with long QT syndrome (LQTS), swimming and loud noises have been identified as genotype-specific arrhythmic triggers in LQTS type 1 and LQTS type 2, respectively.

To compare LQTS groups’ responses to arrhythmic triggers.

LQTS1 and LQTS2 patients were included. Before and after beta blocker intake, electrocardiograms were recorded as participants: 1) were exposed to a loud noise of ∼100 dB. 2) immersed face into cold water.

Twenty-three patients (9 LQTS1 and 14 LQTS2) participated. In response to noise, LQTS groups increased heart rate similarly, but LQTS2 patients prolonged their QTcF (Fridericia) significantly more than LQTS1: 37±8 vs. 15±6 ms (p=0.02). After intake of beta blocker, the QTcF prolongation in LQTS2 patients was significantly blunted and similar to LQTS1 (p=0.90).
In response to simulated diving, LQTS groups experienced a heart rate drop of ∼28 bpm, which shortened QTcF similarly in both groups. After intake of beta blockers, heart rate dropped 28±2 bpm in LQTS1 patients and 20±3 bpm in LQTS2, resulting in slower heart rate in LQTS1 compared with LQTS2 (p=0.01). In response, QTcF shortened similarly in LQTS1 and LQTS2 patients: 57±9 vs. 36±7 ms (p=0.10).

When exposed to noise, LQTS2 patients prolonged their QTc significantly more than LQTS1 patients. Importantly, beta blockers reduced the noise-induced QTc prolongation in LQTS2 patients — demonstrating the protective effect of beta blockers. In response to simulated diving, LQTS groups responded similarly, but a slower heart rate was observed in LQTS1 patients during simulated diving after beta blockers.
TidsskriftHeart Rhythm
StatusE-pub ahead of print - 31 aug. 2020

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