European Heart Journal Advance Access originally published online on June 6, 2006
European Heart Journal 2006 27(14):1760-1761; doi:10.1093/eurheartj/ehl074
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Abnormal QT responses to adenosine in subjects with long QT syndrome: reply
Department of Cardiology
Tel Aviv Sourasky Medical Center
Cardiac Hospitalization Unit
Weizman 6
Tel Aviv 64239
Israel
E-mail address: saviskin{at}tasmc.health.gov.il
Department of Cardiology
Tel Aviv Sourasky Medical Center
Cardiac Hospitalization Unit
Weizman 6
Tel Aviv 64239
Israel
Department of Cardiology
Tel Aviv Sourasky Medical Center
Cardiac Hospitalization Unit
Weizman 6
Tel Aviv 64239
Israel
We agree with Dr Ballo that understanding the significance of specific QTc values observed during the sudden heart rate slowing and acceleration provoked by adenosine, in patients with long-QT syndrome (LQTS), is problematic. Clearly, the QTc values obtained during the extreme bradycardia or tachycardia provoked by adenosine should not be defined as ‘normal’ or ‘prolonged’ on the basis of the time-honoured literature on the LQTS, which relates to values during undisturbed heart rate at rest. Instead, the QTc values during the adenosine test should be viewed in comparison with those of a large control population undergoing the same test. Moreover, the following observations suggest that the observations presented in our study on the use of the adenosine challenge test for diagnosing LQTS1 are valid. (i) The heart rate deceleration provoked by adenosine was similar in patients and controls. If anything, controls developed slower heart rate during the bradycardia phase of adenosine (RR interval of 2240±1270 ms in controls vs. only 1670±670 ms in LQTS, P=0.09). However, the absolute (i.e. uncorrected) QT interval increased much more in LQTS patients. In fact, the absolute QT of controls hardly changed despite the marked and sudden bradycardia (the QT of controls increased by only 1.5±6.7% in comparison with their baseline). In contrast, the uncorrected QT of patients with LQTS increased during similar degrees of bradycardia by 15.8±13.1% (P<0.001).1 (ii) Similar arguments can be made about the tachycardia-induced QT changes provoked by adenosine. Despite similar degrees of adenosine-induced heart rate acceleration, not only the QTc, but also the absolute (uncorrected) QT intervals were much longer in LQTS patients (Figure 1 in our article).1 In addition, except for T-wave inversion (which was a non-specific finding), bradycardia and/or tachycardia-induced changes in T-wave morphology were of diagnostic value (Figures 3 and 4 in our article).1 As described for the epinephrine-challenge test,2 appearance of notched T-waves during our adenosine challenge test (especially when the second component of the T-wave was tall) was highly suggestive of LQTS.1
We agree with Dr Ballo that it is likely that patients with LQT3 will develop steeper QT prolongation during the bradycardia phase of the adenosine test, whereas LQT1 patients will develop QT changes only during the tachycardia phase. However, we do not have sufficiently large number of genotyped patients and we hope that other groups will eventually test this hypothesis.
References
- Viskin S, Rosso R, Rogowski O, Belhassen B, Levitas A, Wagshal A, Katz A, Fourey D, Zeltser D, Oliva A, Pollevick GD, Antzelevitch C, Rozovski U. (2006) Provocation of sudden heart rate oscillation with adenosine exposes abnormal QT responses in patients with long QT syndrome: a bedside test for diagnosing long QT syndrome. Eur Heart J 27:469–475.
[Abstract/Free Full Text] - Khositseth A, Hejlik JB, Shen WK, Ackerman MJ. (2005) Epinephrine-induced T-wave notching in congenital long QT syndrome. Heart Rhythm 2:141–146.[CrossRef][Web of Science][Medline]
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