Rosso Raphael, Adler Arnon, Strasberg Boris, Guevara-Valdivia Milton E, Somani Riyaz, Baranchuk Adrian, Halkin Amir, Márquez Manlio F, Scheinman Melvin, Steinvil Arie, Belhassen Bernard, Kazatsker Mark, Katz Amos, Viskin Sami
From the Tel Aviv Sourasky Medical Center (R.R., A.A., A.H., A.S., B.B., S.V.) and Rabin Medical Center, Petah-Tikva (B.S.), Sackler School of Medicine, Tel Aviv University, Israel; UMAE Hospital de Especialidades Dr. Antonio Fraga Mouret, CMN La Raza IMSS, Mexico (M.E.G.-V.); Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico (M.F.M.); Kingston General Hospital, Queen's University, Kingston, ON, Canada (R.S., A.B.); University of California San Francisco (M.S.); Hillel Yaffe Medical Center, Hedera, Israel (M.K.); and Barzilai Medical Center, Ashkelon, Ben-Gurion University, Beersheba, Israel (A.K.).
Circ Arrhythm Electrophysiol. 2014 Dec;7(6):1129-35. doi: 10.1161/CIRCEP.114.002085. Epub 2014 Oct 13.
The magnitude of QT prolongation in response to bradycardia, rather than the bradycardia per se, determines the risk for torsade de pointes during atrioventricular block (AVB). However, we do not know why some patients develop more QT prolongation than others, despite similar bradycardia. We hypothesized that in patients who develop significant QRS vector changes during AVB, the effects of cardiac memory lead to excessive QT prolongation.
We studied 91 patients who presented with AVB and who also had an ECG predating the bradyarrhythmia for comparison. We correlated changes in QRS morphology and axis taking place during AVB with the bradycardia-induced QT prolongation. Patients with and without QRS morphology changes at the time of AVB were of similar age and sex. Moreover, despite similar R-R interval during AVB, cases with a QRS morphology change had significantly longer QT (648 ± 84 versus 561 ± 84; P<0.001) than those without. Patients who developed a change in QRS morphology at the time of AVB had a 7-fold higher risk of developing long QT. This risk nearly doubled when the change in QRS morphology was accompanied by a change in QRS axis.
Cardiac memory resulting from a change in QRS morphology during AVB is independently associated with QT prolongation and may be arrhythmogenic during AVB.
房室传导阻滞（AVB）期间，尖端扭转型室速的风险取决于心动过缓时QT间期延长的程度，而非心动过缓本身。然而，我们并不清楚为何有些患者尽管心动过缓程度相似，但QT间期延长却比其他患者更明显。我们推测，在AVB期间出现显著QRS向量改变的患者中，心脏记忆效应会导致QT间期过度延长。
我们研究了91例患有AVB且有心动过缓发作前心电图以供比较的患者。我们将AVB期间发生的QRS形态和电轴变化与心动过缓诱发的QT间期延长进行关联分析。AVB时出现和未出现QRS形态改变的患者在年龄和性别上相似。此外，尽管AVB期间R-R间期相似，但出现QRS形态改变的患者QT间期（648±84对561±84；P<0.001）显著长于未出现改变的患者。AVB时出现QRS形态改变的患者发生长QT的风险高7倍。当QRS形态改变伴有QRS电轴改变时，这一风险几乎翻倍。
AVB期间QRS形态改变导致的心脏记忆与QT间期延长独立相关，且在AVB期间可能具有致心律失常性。
