Usability of QTc dispersion for the prediction of orthostatic intolerance syndromes.
BACKGROUND
Syncope is defined as transient loss of consciousness and muscle tone, usually of short duration. Noncardiac causes of syncope are classified as orthostatic intolerance syndromes (OIS). QT and QTc (corrected QT) dispersions are the measurements of myocardial instability and show predisposition to arrhythmias. In this study; clinical findings, QT and QTc dispersions of the patients who were diagnosed as OIS were evaluated retrospectively. Also, the aim of the study is to clarify the association of clinical characteristics of unexplained syncope with the outcome of the QT and QTc dispersions in children.


METHODS
We designed a retrospective study including 152 children and adolescents who had repeated unexplained syncope or presyncope between June 2002 and August 2010. Head-up Tilt table test (HUTT) were performed for all patients. Control group consisted of 67 healthy children. The QT and QTc dispersions were measured from the 12 ECG leads.


RESULTS
Eighty-four (55.2%) patients had positive and 68 (44.8%) had negative response to HUTT. QT and QTc dispersions were significantly higher in HUTT-positive group than in negative (p < 0.01, p < 0.001 respectively). Also, QTc dispersion was significantly higher in both vasovagal syncope and postural orthostatic tachycardia syndrome groups than in HUTT-negative group (p < 0.001, p < 0.05 respectively). Specifity and sensitivity of QTc dispersion for predicting positive HUTT are 76.5% and 59.5% respectively. The positive predictive value of the test calculated as 75.8%.


CONCLUSIONS
These results revealed that we can use QTc dispersion measurement as a noninvasive electrocardiographic test to evaluate OIS for predicting positive result before performing HUTT.
Selcuk University Meram, Department of Pediatric Cardiology, Beysehir Yolu, Meram, Konya, Turkey. zehrakaratas1975@hotmail.com
Zehra
Z
Karataş
Hayrullah
H
Alp
Fatih
F
Sap
Hakan
H
Altın
Tamer
T
Baysal
Sevim
S
Karaarslan
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D054971:Orthostatic Intolerance / Q000175:diagnosis* / Q000503:physiopathology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018667:Tilt-Table Test