Published online Feb 15, 2018. doi: 10.4291/wjgp.v9.i1.28
Peer-review started: August 7, 2017
First decision: September 7, 2017
Revised: October 4, 2017
Accepted: October 30, 2017
Article in press: October 30, 2017
Published online: February 15, 2018
Cirrhosis can affect many organs and systems of the body including cardiovascular and autonomic nervous system (ANS). Cirrhotic patients have abnormal ANS function and it is reflected in several cardiac- and vascular-related parameters such as QT interval prolongation, heart rate variability (HRV) and arterial pressure changes, all components of the so-called cardiac autonomic neuropathy (CAN). Both QT prolongation and CAN have been associated with increased cardiovascular and all-cause mortality. The findings of this study show that cirrhotic patients and, in particular those who have at the same time diabetes or who are on treatment with diuretics, have longer QT interval independently from serum electrolyte levels, suggesting that they need monitoring for QT prolongation.
This study has shown that patients with cirrhosis have more often CAN and QT prolongation; however, this is a cross-sectional study and a cause and effect relationship cannot be established. A prospective study is needed to examine whether patients with cirrhosis develop autonomic dysfunction and QT prolongation. Moreover, it would of interest to know the potential impact of treatment with b-blockers on QT interval or cardiac ANS activity. An important finding of this study is that the etiology of cirrhosis does not impact QT prolongation or cardiac autonomic activity.
The main aim of this study was to examine the impact of liver cirrhosis on QT-related parameters and on CAN. The authors’ hypothesis was confirmed and implies that cardiac autonomic dysfunction and/or QT prolongation may contribute to the increased mortality in patients with cirrhosis.
In this study, the authors managed to collect complete data related to full blood count and biochemical analyses, while the diagnosis of cirrhosis was confirmed with liver biopsies when it was indicated. The diagnosis of cardiac autonomic dysfunction was based upon robust criteria such as the battery of the tests proposed by Ewing and Clarke by determination of the HRV. QT intervals were measured using a standard 12-lead ECG recordings. Statistical analysis was performed using programs available in the SPSS statistical package by four co-authors who have experience in statistical analysis and a biomedical statistician.
In the present study, the authors found that QT and QTc intervals as well as their dispersions were substantially prolonged in patients with cirrhosis in comparison with healthy controls. In addition, the authors demonstrated that patients with cirrhosis were diagnosed more often with cardiac autonomic dysfunction. Additionally, the authors found that severity of cirrhosis does not impact QT interval but it affects severity of cardiac autonomic dysfunction.
The novel finding of this study is that not only QT, but also QT dispersion is prolonged in patient with cirrhosis. Furthermore, CAN or QT prolongation is not associated with the etiology of cirrhosis. Patients with cirrhosis, especially those who have diabetes or an on treatment with diuretics should be screened for cardiac autonomic dysfunction an QT prolongation. Patients with cirrhosis have often CAN and QT prolongation. The original insights of this study are: (1) the authors measured QT dispersion, which is considered as an excellent marker of left ventricular repolarization abnormalities and better than QT prolongation, which has not been studied so far; and (2) the authors found that severity of cirrhosis affects strongly cardiac ANS activity and probably contributes to the development of the cirrhotic myocardiopathy. The new methods used in this study is the robust methodology for the diagnosis of cardiac autonomic dysfunction and presence as well as severity of cirrhosis.
The results of this study suggest that patients with cirrhosis often have QT prolongation and cardiac autonomic dysfunction and therefore, they should be screened for these comorbidities; especially those who have diabetes or an on treatment with diuretics. Future research should be directed to the potential impact of treatment with b-blockers on QT interval or cardiac ANS activity. In addition, a prospective study is needed to examine whether patients with cirrhosis develop autonomic dysfunction and QT prolongation.