C-reactive protein is associated with ventricular repolarization dispersion among patients with metabolic syndrome

1Faculty of Medicine, Tetovo Republic of North Macedonia 2Department of Internal Medicine, Faculty of Medicine, Tetovo, Republic of North Macedonia 3Department of Cardiology, Faculty of Medicine, Saints Cyril and Methodius University of Skopje, Republic of North Macedonia 4Department of Cardiology, Faculty of Medicine, M Teresa, Tirana, Republic of Albania 5Department of Internal Medicine, Faculty of Medicine, Tetovo, Republic of North Macedonia 6Department of Cardiology, Medical Center, Dures, Republic of Albania 7Department of Cardiology, Medical Center, Dures, Republic of Albania 8Private Health Institute of Family Medicine, "Florenc", Tetovo, Republic of North Macedonia 9Department of Internal Medicine, General Hospital, "DR Ferit Murat" Gostivar, Republic of North Macedonia 10Private Health Institute,”Rostusha” Debar, Republic of North Macedonia


Introduction
Metabolic syndrome (MetS) has been an increasing health problem worldwide for the last three decades. Estimates suggest that this disorder affects approximately 35%-44% of the adult population. MetS is associated with adverse cardiac events [1,2].
Despite the increasing prevalence of MetS, we have a limited understanding of the contribution of metabolic abnormalities to adverse cardiac events, also precise mechanisms are still under study. An increasing body of evidence indicates that in lammatory activation profoundly impacts the electrophysiological properties of cardiomyocytes via multiple effects, ultimately resulting in a prolongation of Action Potential duration (APD), and thereby of the QTC (QT corrected interval) on ECG [3]. Chronic systemic inlammation in MetsS has emerged as a possible role in the development of arrhythimic events. A marker of systemic in lammation such as C-reactive protein (CRP), is associated with all parameters of the MS and that may result in arrhythmias [4][5][6].One interesting observation is that higher level of proin lamatory citokines in patients with MS correlate with sudden cardiac death [7]. QT interval remains the most widely used index for assessing the propensity to ventricular arrhythmias. Prolonged QT-dispersion, that re lects spatial inhomogeneity in ventricular repolarization, prolonged Tpeak-Tend dispersion, that re lects transmural inhomogeneity in ventricular repolarization, are associated with increased risk of adverse cardiac events (certain arrhythmias and sudden cardiac death) [8,9]. We have e limited understanding of the contribution of chronic in lammation to changes in a set of electrophysiological parameters that indicate a prolonged and more heterogeneous repolarization in patient with MetS. We tested hypothesis: Patients with MS and high level of CRP have higher prevalence of QTdispersion and Tpeak-Tend dispersion than patients with MS and lower level of CRP. These indings might lend further insight into potential mechanisms by which MetS is associated with adverse cardiac events.

Objective
We sought to investigate the in luence of CRP levels on the prevalence of prolonged QT-dispersion and prolonged Tpeak-Tend -dispersion in the patients with MS.

Study design
We conducted a multicenter observational cross-sectional study. The study population was recruited from our outpatient clinic between January 2018 and December 2018. Subjects who ful illed the criteria for MetS according to the results of recent laboratory tests were prospectively evaluated.
The population consisted of 200 patients with MetS strati ied in two groups: 103 participants (50 females and 53 males) with level of CRP>3mg/l, and 97 participants (47 females and 50 males) with level of CRP<3mg/l).
All participants underwent a comprehensive medical history and physical examination. Resting ECG, anthropometrics, blood pressure (obtained after 10 min of rest in the sitting position, expressed as the average of 3 consecutive measurements). Hypertension was de ined as a systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg and/or current anti-hypertensive therapy [10]. Diabetes mellitus was de ined as a fasting serum glucose level ≥126 mg/dL and/or current medical therapy with an oral hypoglycemic agent and/or insulin [11]. Body mass index (BMI) was calculated as weight (kg) divided by the square of the height (m 2 ). Weight was measured with weight balance scales, and height with stadiometer. WCi, was reported in cm. An overnight fasting blood sample, was drawn from each patient to determine: blood glucose, lipid pro ile tests total serum cholesterol (TC), serum High density lipoproteins cholesterol (HDL-C), serum triglycerides (TG). The sample analysis was performed using standard biochemical analytical methods. Plasma CRP levels was measured using latex particle-enhanced immunoassay with the mephelometry (Roche Swiss).Consistent with recommendations from Centers for Disease Control and Prevention [12] (a CRP cutpoint of 3.0mg/L),was used to differentiate high-risk and low-risk group. We excluded all patients with: cardiac arrhythmias, left/right bundle branch block, pre-excitation syndromes, patients with pacemakers, and dialysis patients, anemia, electrolyte inbalnce, renal failure and pulmonary disease. We also excluded patients treated with drugs that prolong the QT interval, suggested by the European Society of Cardiology (ESC) [13].
MetS was de ined according to the harmonized de inition of the International Diabetes Federation and other organizations [1], that three or more out of ive following criteria are considered as MetS: (1) central adiposity {Waist circumference (WCi)} >102 cm in men and >88cm in women); (2) serum HDL-C < 50 mg/dL in women or < 40 mg/dL in men; (3) serum triglyceride levels > 150 mg/dL; (4) SBP ≥ 130mmHg or DBP ≥ 85mmHg or use of antihypertensive drugs; (5) the presence of diabetes mellitus(DM) or use of anti-diabetic drugs.

QTc-Dispersion. Tpeak-Tend disperion measurements
All subjects underwent a standard 12-leads surface ECG. The ECG was always performed with the patient's supine, at rest, at a paper speed of 25 mm/s and voltage of 10 mm/mV. To make the ECGs we used the electrocardiograph Cardioline -Delta 1 Plus. The subjects were required to have a normal ECG and with no pathologic processes that might affect ventricular repolarization. To this end, we conducted a consultation of the clinical process and only one ECG of the individuals that met the desired criteria. For the analysis of the ECG, we performed a manual measurement of the values using a digital caliper with measuring range of 0-150 mm, 0.01 mm resolution, and 0-100 ± 0.02 mm accuracy. The value obtained was converted to milliseconds (ms).
Measurement of the QT interval (the interval from the start of the QRS complex to the end of the T-wave) was performed in all 12 leads, and the longest and the shortest intervals measured were selected. QT interval dispersion was obtained by the difference between the maximum and the minimum QT intervals found in the 12lead electrocardiogram. The QT interval was corrected according to Bazett's formula which consists in dividing the measured QT by the square root of the RR interval (QTC = QT/√ RR), thus providing the QT interval value adjusted for heart rate.
The QTc dispersion was obtained by the difference between the highest and the lowest values of QTc in the 12 leads of the ECG [14].
According to internationally accepted guidelines, the QTC interval was considered prolonged when higher than 440 ms for male patients, and higher than 460 ms for female patients [15]. The QT dispersion was considered prolonged when higher than 65 ms, according to other previously conducted studies [16]. Measurement of the Tpeak-Tend interval was conducted in DII, V2 and V5 leads. The Tpeak-Ted interval was obtained from the difference between QT interval and QT peak interval. The Tpeak-Tend interval was considered prolonged when greater than 100 ms, and the Tpeak-Tend dispersion was considered prolonged when higher than 20 ms, as suggested by otherstudies [17]. The ECG was performed by the same operator, and the aforementioned measurements were made by two independent observers.In case of disagreement on the values obtained, the measurements were repeated by a third observer with expertise in electrocardiographic analysis.
The study is in compliance with the Declaration of Helsinki. All patient that participated in this study were written informed, consent was obtained from all participating patients before they were enrolled into the study (Figure 1).
Results are expressed as mean and ±SD, or as percentage. A simple descriptive analysis was performed for the general characterization of the sample and distribution of variables. The distribution of variables was tested for normality using the Kolmogorov-Smirnov test, and the heterogeneity of variances was evaluated by Levene's test. To compare baseline characteristics and echocardiographic indings between groups, we used Student , s unpaired t test for continuous data, Mann-Whithey U -test for continuous data with abnormal distribution, and X 2 -test for categorical data. The association between variables were analyzed using logistic regression. Odds ration (OR) and 95% con idence interval (CI) were estimated by logistic regression. A, p value <0.05 was considered statistically signi icant for a con idence interval of 95%.Statistical analyses were performed with the SPSS software package (SPSS 19.0).

Results
A total of 200 patients with MS strati ied in two groups: 103 participants (50 females and 53 males) with level of CRP>3mg/l , and 97 participants (47 females and 50 males) with level of CRP<3mg/l), completed the suvey and provided data for a onemedical record review.
We conducted a comparative analysis between the participants with level of CRP>3mg/l and participants with level of CRP<3mg/l, of the following parameters: QT and QTC intervals, QT and QTC dispersions, Tpeak-Tend intervals, and Tpeak-Tend dispersions, data are shown in table 2.

QT and QTC intervals:
The result showed that, only mean of QTCmax. Interval, was signi icantly higher in participants with level of CRP>3mg/l than participants with level of CRP<3mg/l (448.27±16.2ms vs.437.92±15.2ms, p<0.001). No signi icant differences were observed between participants with level of CRP>3mg/l and participants with level of CRP<3mg/l, in others means QT. intervals and means of corrected for Heart rate QT. intervals. QT-max.

Prolonged (QT dispersion and QTC dispersion):
No signi icant differences were observed between participants with level of CRP>3mg/l and participants with level of CRP<3mg/l in relation to prolonged QT-dispersion (29.39 ±2.2 vs.30.42±1.8, Frequency of prolonged QTCmax. Interval: Prolonged QTC.max. interval, was found in 46.6% of participants with level of CRP>3mg/l and in 27.8% in participants with level of CRP<3mg/l, the differences were statistically signi icant.(p=0.04).
Frequency of prolonged QTC-dispersion: Prolonged QTC. dispersion, was found in 51.4% of participants with level of CRP>3mg/l and in 32.9% of with level of CRP<3mg/l, the differences were statistically signi icant.(p=0.004).

Frequency of prolonged Tpeak-Tend intervals:
The results showed that 51.4% participants with level of CRP>3mg/l had a prolonged Tpeak-Tend interval, and 30.9% of participants with level of CRP<3mg/l had prolonged Tpeak-Tend interval. Difference were statistically signi icant (p=0.004).

Frequency of prolomged Tpeak-Tend Dispersion:
The results showed that 51.4% participants with level of CRP>3mg/l had a prolonged Tpeak-Tend interval, and 32.9% of participants with level of CRP<3mg/l had prolonged Tpeak-Tend interval. Difference were statistically signi icant (p=0.04).
In a Simple logistic regression (Table 3), we investigated the independent association of CRP levels with: QTC-dispersion, Tp-Te-dispersion, Prolonged QTC max. interval, Prolonged Tp-Te-interval, BMI and uncontrolled glicemia. There were signi icant association of increased levels of CRP and QTC-dispersion (OR = 2.486,95% CI 1.389-

Discusion
Despite the increasing prevalence of MetS, we have a limited understanding of the contribution of metabolic abnormalities to adverse cardiac events. Increasing body of evidence indicates that in lammatory activation profoundly impacts the electrophysiological properties of cardiomyocites [3]).In this study we found that patients with MetS and higher levels of CRP had signi icantly higher prevalence set of electrophysiological parameters that indicate a prolonged and more heterogeneous repolarization than did those with MetS and lower levels of CRP. Results of present study con irmed our hypothesis. Experimental and observational evidence suggest that in lammation has a pivotal role in cardiac remodeling in patient with MetS [19], also several proin lamatory cytokines modulate membrane potencial and abnormal Ca 2+ homeostasis with consequently prolongs the Ca 2+ transient duration and action potencial [20]. Increased dispersion of repolarization between the base and apex of the heart intramurally or in the region of interventricular septum predisposes to ventricular arrhythmias, especially in the presence of ion channel diseases including long QT syndrome, short QT syndrome [21,22]. These markers may be used as an electrocardiographic index of ventricular arrhythmogenesis and sudden cardiac death [23]. In our study, prevalence of prolonged QTC-max. interval, prolonged QTCdisprsion and prolonged Tpek-Tend interval, prolonged Tpek-Tend-dispersion, was higher in patient with MetS and higher levels of CRP. Previous evidence suggest that MetS lead to cardiac electrical remodeling [24], and increased levels of CRP was found to be associated with severity of Mets [25]. In present study increased levels of CRP, was associated independently with number of risk factor of MetS. Others have found similar results [25,26]. A number of previous studies have demonstrated that CRP levels correspond with individual components of MetS [27,28]. In present study increased levels of CRP, was associated independently with Obesity, BMI, uncontrolled glicemia and uncontrolled BP. Results they are consistent with prior studies [27][28][29][30]. Another fact of great importance is the in luence of medication on several elektrocardiographic parameters, there are numerous drugs that cause prolongation and/or dispersion of repolarization. This study was excluded individuals receiving medication that are more frequently associated with repolarization changes, however, there was no absolute guarantee that all other medications had no in luence on repolarization. In fact, a study by Costa et al. [31], evaluated the in luence of metformin (a drug commonly used in diabetics to control blood glucose) on QT interval and QT dispersion in diabetic rats. The results showed that, with low and moderate doses of metformin, there were signi icant changes in electrcardiographic parameters, but this did not happen when the dose was high. Our data highlights the possible role of chronic in lammation in the development of electrical remodeling in patients with MetS.

Several limitations deserve mention:
Our study is a cross-sectional observational study, oversimpli ication of multifactorial mechanisms based upon limited markers, is inhered to this kind of studies and precludes causal inferences. A larger sample would certainly increase the statistical power of the study, and probably some differences would therefore become more expressive. Moreover, manual measurements of intervals without the support of any technology that could ensure a more precise measurements may also be an aspect to be taken into account. The accuracy and reproducibility of measurements of repolarization parameters problem encountered was the lack of a consensus on the values of several normal electrocardiographic parameters. Despite some methodological limitations, this study clearly demonstrated a relationship between increased levels of CRP and changes in set of electrophysiological parameters that indicate a prolonged and more heterogeneous repolarization in patient with MetS.

Conclusion
We think we proved the hypothesis that patients with MetS and high level of CRP have higher prevalence of QT-dispersion and Tpeak-Tend dispersion than patients with MetS and lower level of CRP. These indings have both epidemiological and clinical relevance, also these indings might lend further insight into potential mechanisms by which MetS is associated with adverse cardiac events. Assessment of levels of CRP for arrhythmogenic risk may be important for better risk strati ication of patients with MetS, a conclusion that needs con irmation in larger prospective studies.