ABC | Volume 110, Nº6, June 2018

Original Article Karaman et al Myocardial repolarization and VPC burden Arq Bras Cardiol. 2018; 110(6):534-541 heart disease. 7,30,31 Tp-e interval is considered a new marker of increased risk of SCD. Yamaguchi et al. 32 showed that Tp-e interval is more significant than QTd or QTc in predicting Torsade de Pointes in patients with acquired long QT syndrome. At the same time, an increase in Tp-e interval and Tp-e/QT ratios was shown to be associated with Brugada syndrome. 8 Tp-e/QT and Tp-e/QTc ratios were found to be relatively more constant than other markers because they were not affected by changes in heart rate and body weight. 9 Althoughwe found an increase in Tp-e interval and Tp-e/QTc ratios as VPC frequency increased, the slight increase observed in Tp-e/QT ratio was not statistically significant. Yayla et al. 33 assessed the myocardial repolarization parameters before and after RFA in patients with a VPC burden of more than 5% on a 24 h Holter recording. After the successful procedure, Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio significantly decreased more than before RFA (all p < 0.001). In accordance with this data, the higher detection of Tp-e interval in patients with increased VPC frequency suggests that the risk of malignant arrhythmias might be higher in these patients. In our study, malignant arrhythmias, such as Vc and VT, were seen more in group 3 patients, thus supporting our predictions. This important link can be used to closely follow up on and manage their treatment of patients with increased VPC frequency. Study limitations Our study has several major limitations. First, our study was single centered and included a small number of patients. Therefore, statistical power was limited. The results should be verified in a larger prospective cohort study. Second, because we did not have other ambulatory Holter measures, such as heart rate variability and heart rate turbulence, we could not exclude the effect of these measurements on the VPC frequency. Third, we did not have data on cardiac event rates for this study because we could not follow up on the patients prospectively for future arrhythmic events. Fourth, we aimed to record a relatively young patient profile to exclude occult CAD in our study. However, we abandoned this goal because of the limited number of patients. Further comprehensive studies should be conducted with a larger number of patients and a longer follow-up time to increase the consistency of our results. Conclusions In conclusion, Tp-e interval and Tp-e/QTc ratios increased in patients with high VPC number. Our study showed that VPCs could have a negative effect on myocardial repolarization. This interaction could lead to an increased risk of malignant arrhythmias. Author contributions Conception and design of the research: Karaman K, Karayakali M, Arisoy A; Acquisition of data: Karaman K, Akar O, Ozturk M, Yanik A, Yilmaz S; Analysis and interpretation of the data: Karaman K, Karayakali M, Arisoy A, Yilmaz S, Celik A; Statistical analysis: Karaman K, Karayakali M, Arisoy A, Akar O, Celik A; Obtaining financing: Karaman K, Arisoy A, Akar O; Writing of the manuscript: Karaman K, Arisoy A, Yanik A; Critical revision of the manuscript for intellectual content: Karaman K, Karayakali M, Ozturk M, Yanik A, Celik A. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This study is not associatedwith any thesis or dissertationwork. Ethics approval and consent to participate This study was approved by the Ethics Committee of the Gaziosmanpasa University Faculty of Medicine under the protocol number 83116987-252. All the procedures in this study were in accordance with the 1975 Helsinki Declaration, updated in 2013. Informed consent was obtained from all participants included in the study. 539