El-Hamad Fatima J, Bonabi Safa Y, Müller Alexander, Steger Alexander, Schmidt Georg, Baumert Mathias
School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA, Australia.
School of Electronic and Telecommunications Engineering, RMIT University, Melbourne, VIC, Australia.
Front Physiol. 2020 Nov 9;11:578173. doi: 10.3389/fphys.2020.578173. eCollection 2020.
This study seeks to decompose QT variability (QTV) into physiological sources and assess their role for risk stratification in patients post myocardial infarction (MI). We hypothesize that the magnitude of QTV that cannot be explained by heart rate or respiration carries important prognostic information.
Elevated beat-to-beat QTV is predictive of cardiac mortality, but the underlying mechanisms, and hence its interpretation, remain opaque.
We decomposed the QTV of 895 patients post MI into contributions by heart rate, respiration, and unexplained sources.
Cox proportional hazard analysis demonstrates that augmented oscillations in QTV and their level of dissociation from heart rate are associated with a higher 5-year mortality rate (18.4% vs. 4.7%, < 0.0001). In patients with left ventricular ejection fraction (LVEF) > 35%, a higher QTV risk score was associated with a significantly higher 5-year mortality rate (16% vs. 4%, < 0.0001). In patients with a GRACE score ≥ 120, a higher QTV risk score was associated with a significantly higher 5-year mortality (25% vs. 11%, < 0.001).
Augmented oscillations in QTV and discordance from heart rate, possibly indicative of excessive sympathetic outflow to the ventricular myocardium, predict high risk in patients post MI independent from established risk markers.
www.ClinicalTrials.gov, identifier NCT00196274.
本研究旨在将QT间期变异性（QTV）分解为生理来源，并评估其在心肌梗死（MI）后患者风险分层中的作用。我们假设无法由心率或呼吸解释的QTV大小携带重要的预后信息。
逐搏QTV升高可预测心脏死亡，但潜在机制及其解释仍不明确。
我们将895例MI后患者的QTV分解为心率、呼吸和无法解释的来源所起的作用。
Cox比例风险分析表明，QTV的增强振荡及其与心率的解离程度与较高的5年死亡率相关（18.4%对4.7%，<0.0001）。在左心室射血分数（LVEF）>35%的患者中，较高的QTV风险评分与显著更高的5年死亡率相关（16%对4%，<0.0001）。在GRACE评分≥120的患者中，较高的QTV风险评分与显著更高的5年死亡率相关（25%对11%，<0.001）。
QTV的增强振荡以及与心率的不一致，可能表明心室心肌交感神经流出过多，可独立于既定风险标志物预测MI后患者的高风险。
