Key result
Short-long RR interval patterns significantly increased action potential duration dispersion in LQT2 rabbits but not in LQT1 rabbits, driven by heterogeneous APD restitution and short-term cardiac memory.
Why the study?
Polymorphic ventricular tachycardia initiation in LQT2 is associated with short-long RR intervals, leading to the hypothesis that this pattern increases APD dispersion to promote arrhythmia.
Does short-long heart rate variation increase APD dispersion in LQT2 transgenic rabbit models?
Does short-long heart rate variation increase APD dispersion in LQT2 transgenic rabbit models?
Short-long heart rate variations increase action potential duration dispersion specifically in LQT2 through heterogeneous restitution and short-term memory, providing a mechanistic basis for pause-dependent arrhythmias in LQT2.
Short-long RR patterns may heighten LQT2 arrhythmia risk; hypothesis-generating for human pause-dependent triggers, requiring clinical validation.
The initiation of polymorphic ventricular tachycardia in long QT syndrome type 2 (LQT2) has been associated with a characteristic ECG pattern of short-long RR intervals. We hypothesize that this characteristic pattern increases APD dispersion in LQT2, thereby promoting arrhythmia. We investigated APD dispersion and its dependence on two previous cycle lengths (CLs) in transgenic rabbit models of LQT2, LQT1, and their littermate controls (LMC) using random stimulation protocols. The results show that the short-long RR pattern was associated with a larger APD dispersion in LQT2 but not in LQT1 rabbits. The multivariate analyses of APD as a function of two previous CLs (APD n = C + α 1 CL n−1 + α 2 CL n−2 ) showed that α 1 (APD restitution slope) is largest and heterogeneous in LQT2 but uniform in LQT1, enhancing APD dispersion under long CL n−1 in LQT2. The α 2 (short-term memory) was negative in LQT2 while positive in LQT1, and the spatial pattern of α 1 was inversely correlated to α 2 in LQT2, which explains why a short-long combination causes a larger APD dispersion in LQT2 but not in LQT1 rabbits. In conclusion, short-long RR pattern increased APD dispersion only in LQT2 rabbits through heterogeneous APD restitution and the short-term memory, underscoring the genotype-specific triggering of arrhythmias in LQT syndrome.
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Kim et al. (2019) studied Long QT syndrome (LQT1 and LQT2) (n=23). Short-long cycle length variation vs. LQT1 and littermate control rabbits was evaluated on Action potential duration (APD) dispersion. Short-long RR interval patterns significantly increased action potential duration dispersion in LQT2 rabbits but not in LQT1 rabbits, driven by heterogeneous APD restitution and short-term cardiac memory.
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