Bariatric surgery mitigated electrocardiographic abnormalities in patients with morbid obesity

Obesity can lead to cardiovascular dysfunctions and cause electrocardiographic disruptions. Bariatric surgery plays a significant role in weight loss. To assess its benefits, this study investigated electrocardiographic changes before and after bariatric surgery. The present article describes a retrospective cohort study with a 6-month follow-up period. Electrocardiograms were interpreted and compared before and six months after surgery. The relationships between weight loss, type of surgery, and electrocardiographic alterations were analyzed. A total of 200 patients participated in the study, with 34 (17%) men and 166 (83%) women. The mean age of the participants was 44.6 ± 8.6, and their mean body mass index was 43.8 ± 5.5 kg/m2. The mean of QTc decreased after the surgery, while the Sokolow-Lyon scores increased. The statistical analysis showed that QTc dispersion (> 40) (P < 0.001), right ventricular hypertrophy (P < 0.001), abnormal R wave progression (P < 0.001), QTc (P < 0.001) and Sokolow-Lyon criteria (P < 0.001) significantly changed postoperatively. In conclusion, bariatric surgery can reduce QTc, correct poor R wave progression, and resolve right ventricular hypertrophy (RVH) in patients with morbid obesity.


Correlations and regression analysis
We examined whether the demographic and anthropometric factors and the type of bariatric surgery impacted postoperative changes.We conducted a multiple regression analysis for QTc and the Sokolow-Lyon score.However, none of the dependent variables significantly affected either of these parameters.We used binary logistic regression to analyze the relationships between dichotomous variables such as QTc dispersion, RVH, and abnormal R wave progression.Only the type of bariatric procedure significantly predicted abnormal R wave progression (OR: 0.434, P = 0.025).Tables 3 and 4 demonstrate the results of the regression analysis in detail.

Discussion
Obesity is a well-known risk factor for various cardiac complications.Therefore, weight is an essential intervention in managing these conditions.Studies have shown that while any weight loss method can improve cardiac function and lower the risk of cardiovascular events 13 , surgical methods provide the best short-term and longterm benefits compared to pharmacological treatments and lifestyle modifications 3 .
In the current study, we aimed to evaluate the effects of bariatric surgery on ECG alterations during a 6-month follow-up period.The most common preoperative abnormality was QTc dispersion in 69.5% of participants, followed by RVH and abnormal R wave progression in 31.5% and 30% of the participants, respectively.However, all three abnormalities were significantly improved after bariatric surgery (P < 0.001).The mean QTc duration was 443.9 ± 23.4 ms, which markedly decreased to 409.7 ± 20.5 ms after the 6-month follow-up (P < 0.001).Our findings suggest that weight loss achieved through bariatric surgery significantly shortened the QTc duration, improved QTc dispersion and RVH and corrected R wave progression (Table 2).The Sokolow-Lyon criteria indicate LVH if the score exceeds 35.Our findings revealed that the score significantly increased after the surgery.This could be explained by the fact that after surgery, patients experienced weight loss, leading to less subcutaneous fat, better positioning of the heart in the thorax, and lower afterload pressure in the left ventricle, which can result in improved left ventricle function.However, although the Sokolow-Lyon score increased, none of the participants developed LVH within the 6-month follow-up period.
A regression analysis was conducted to predict ECG improvements based on sex, age, BMI, and type of surgery, as presented in Table 3.None of these variables had any statistically significant impact on the ECG.However, a statistically meaningful relationship was found between the type of surgery and abnormal R wave progression.Regression analysis revealed that sleeve gastrectomy was less effective than classic bypass in correcting abnormal R wave progression (OR:0.434,P = 0.025).The binomial logistic regression model was statistically significant (χ2(4):10.619;P = 0.031).The model explained 8.5% (Nagelkerke R2) of the variance in abnormal R wave progression and correctly classified 78.8% of the cases.The reason for these improvements lies in the hormonal and autonomic consequences of bariatric surgeries.Previous studies have shown that insulin resistance (IR) is one of the leading causes of prolonged QTc and QT dispersion 6,[20][21][22][23][24][25] .Insulin has been found to hyperpolarize both  28,29 .Significant weight loss is the second most important cause of ECG changes after bariatric surgery.One study showed that individuals lose approximately 25%-30% of their initial weight or achieve 50%-70% excess weight loss after a successful surgery 30 .This substantial weight loss results in various cardiovascular changes 31 .These include a decrease in BMI, which can lead to lower blood pressure, reduced preload, and a decrease in ventricle mass in the long-term.Recent studies have shown that a prolonged QT interval is related to obstructive sleep apnea and sympathetic nervous system activation 5,7,14,32 .Losing weight by any means is expected to improve obstructive sleep apnea and reduce sympathetic activation, resulting in a normalized QT interval.
Our research findings support previously published articles on the effects of bariatric surgery on patients with obesity.Pontiroli et al. 33 conducted a study on 116 patients with obesity who underwent bariatric surgery.They found that LVH and QT prolongation were common prior to surgery.However, one year after the surgery, the QTc decreased in all patients (P < 0.05), and LVH was resolved in the majority of the participants (P = 0.0025).In a similar study, Al-Salameh et al. 34 assessed 28 patients who underwent sleeve gastrectomy and compared QTc changes three months after the operation.They discovered an average decrease of 28.46 ± 15.61 ms in the QTc within the first three months after the surgery (P < 0.0001).Notably, no statistically significant correlation was found between weight loss and decreased QTc 34 .
In a study conducted by Bezante et al. 31 85 individuals with severe obesity were examined in a case-control setting.Of these, 55 people underwent biliopancreatic diversion, while the remaining 30 were in the control group.The researchers found a significant reduction in QTc and QT dispersion after the operation (P < 0.0001).However, they discovered no correlation between weight loss percentage and QTc changes.They concluded that normalizing ventricular rhythm abnormalities is much more responsive to serum glucose and insulin levels than to absolute weight loss 31 .
We must acknowledge that our study had a few limitations to consider.First, we did not measure weight loss or postoperative BMI percentage in our study group.These measurements are crucial for understanding the correlation between the amount of weight loss and the QTc in the short term.Second, we need laboratory data such as glucose, insulin, and lipid profiles to make our study more comprehensive.By comparing these values, we could identify further correlations and insights.
Finally, we conclude that bariatric surgeries can correct abnormal R wave progression and resolve QT dispersion in morbidly obese patients.The QTc interval significantly decreased within six months postoperatively.Given the positive impact on the cardiovascular system, bariatric surgery can be a practical and beneficial choice for morbidly obese patients who are struggling with cardiac complications.

Ethics statement
The study was carried out in accordance with the principles of the Declaration of Helsinki.All authors confirm that all methods were performed in accordance with the relevant guidelines and regulations.The study started after approval from the Shiraz University of Medical Sciences Ethics Committee (approval ID: IR.SUMS.MED.REC.1401.056,approval date: 2022.05.01).The patients undergoing bariatric surgery had to provide written informed consent that informed them of the potential risks during and after the surgery.Patients agreed to participate in a long-term follow-up after the surgery.

Population and study design
In the current cohort, we included 200 patients who underwent bariatric surgery at Mother and Child Hospital in Shiraz, Iran, from April 2020 to March 2021.We used the census method to determine the study population size and enrolled 500 patients admitted for bariatric operations.Ultimately, 200 patients met the inclusion criteria: were candidates for bariatric surgery, had complete medical records, and provided informed consent.Patients who did not consent to participate or had incomplete medical records were excluded from the survey.The patient selection, exclusions, and inclusions are shown in Fig. 1.
We collected demographic information, past medical histories, and intraoperative and postoperative data from the patients' medical records using a prepared checklist.The criteria for bariatric surgeries include the following: 1. BMI > 40 kg/m 2 , 2. BMI > 35 kg/m 2 accompanied by a significant risk factor, e.g., diabetes and hypertension, 3. Poor response to primary weight loss methods, such as exercise, diet, and medical approaches.
Exclusion criteria were considered to remove variables that may bias the results and hamper a clear safety assessment for both patients and researchers.The following exclusion criteria were then applied (Fig. 1 www.nature.com/scientificreports/ 4. Contraindicating medical conditions such as advanced heart disease, unmanaged mental health disorders, or end-stage organ diseases, 5. Individuals who reported medical interference, who were taking medications that could significantly influence weight or interact with surgical procedures or who experienced postoperative recovery were excluded.
The patients were then divided into two groups based on the type of bariatric surgery they received: sleeve gastrectomy and classic bypass.An electrocardiogram was obtained before the surgery and six months postoperatively.An expert cardiologist blindly interpreted and compared the ECGs before and after surgery.

Statistical analysis
Continuous variables are reported as the mean ± SD, while quantitative values are reported as the frequency.To check normality, we used Shapiro-Wilk and Kolmogorov-Smirnov tests and related histograms.We used a paired t-test to compare the means for normally distributed variables, while nonparametric tests were performed for nonnormally distributed values.To analyze categorical data, we conducted a chi-square test.We also ran multiple and binary logistic regression analyses to predict possible correlations between variables.We considered p-values less than 0.05 to indicate statistical significance.The data were analyzed using SPSS version 23.

Table 1 .
Demographic and baseline characteristics of the participants.BMI body mass index.

Table 3 .
The associations of sex, age, BMI, and surgery type with changes in the QTc and Sokolow-Lyon index were assessed via multiple regression analysis.BMI body mass index, df degrees of freedom.

Table 4 .
27e excitable and nonexcitable cells, and can directly prolong the QT interval26.Excess insulin can indirectly cause QTc prolongation by inducing a hyperkalemic state, which is a known cause of this abnormality27.Moreover, higher doses and prolonged periods of hyperinsulinemia can result in increased release of catecholamines, leading to increased blood pressure.Over time, hypertension caused by elevated catecholamine release can cause left ventricle hypertrophy.Studies have suggested that an increased left ventricle mass is one of the most important causes of rhythm abnormalities, particularly QT prolongation effects of sex, age, BMI, and surgery type on QTc dispersion, RVH, and abnormal R wave progression after bariatric surgery according to binary logistic regression analysis.BMI body mass index, RVH right ventricle hypertrophy, OR odds ratio, CI confidence interval, df degrees of freedom.†, ‡ Chi-square of binary logistic regression.Vol:.(1234567890)Scientific Reports | (2024) 14:6710 | https://doi.org/10.1038/s41598-024-57155-2www.nature.com/scientificreports/