title: Long QT syndrome complicating atrioventricular block: arrhythmogenic effects of cardiac memory.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Cardiac memory resulting from a change in QRS morphology during AVB is independently associated with QT prolongation and may be arrhythmogenic during AVB.
authors.affiliation: 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.).
authors.forename: Raphael
authors.initials: R
authors.lastname: Rosso
authors.affiliation: 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.).
authors.forename: Arnon
authors.initials: A
authors.lastname: Adler
authors.affiliation: 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.).
authors.forename: Boris
authors.initials: B
authors.lastname: Strasberg
authors.affiliation: 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.).
authors.forename: Milton E
authors.initials: ME
authors.lastname: Guevara-Valdivia
authors.affiliation: 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.).
authors.forename: Riyaz
authors.initials: R
authors.lastname: Somani
authors.affiliation: 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.).
authors.forename: Adrian
authors.initials: A
authors.lastname: Baranchuk
authors.affiliation: 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.).
authors.forename: Amir
authors.initials: A
authors.lastname: Halkin
authors.affiliation: 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.).
authors.forename: Manlio F
authors.initials: MF
authors.lastname: Márquez
authors.affiliation: 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.).
authors.forename: Melvin
authors.initials: M
authors.lastname: Scheinman
authors.affiliation: 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.).
authors.forename: Arie
authors.initials: A
authors.lastname: Steinvil
authors.affiliation: 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.).
authors.forename: Bernard
authors.initials: B
authors.lastname: Belhassen
authors.affiliation: 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.).
authors.forename: Mark
authors.initials: M
authors.lastname: Kazatsker
authors.affiliation: 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.).
authors.forename: Amos
authors.initials: A
authors.lastname: Katz
authors.affiliation: 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.). samiviskin@gmail.com.
authors.forename: Sami
authors.initials: S
authors.lastname: Viskin
mesh_terms: D000200:Action Potentials; D000368:Aged; D000369:Aged, 80 and over; D054537:Atrioventricular Block / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors
keywords: atrioventricular block; long QT syndrome; torsade de pointes