Introduction
Cardiovascular diseases (CVDs) are among the leading causes of mortality and disability worldwide across different demographics, including men, women, and various racial and ethnic groups [1]. In the United States, approximately 695000 individuals lost their lives to heart disease in 2021, accounting for one in every five deaths [1، 2]. Statistics indicate that one-third of all global deaths are attributable to CVDs [3], with coronary artery disease (CAD) being the most prevalent type. In 2021, CAD was responsible for 375476 deaths, and approximately 5% of adults aged 20 years and older were diagnosed with CAD [2].
Similarly, in Iran, CVDs were among the leading health concerns, with the country experiencing one of the highest rates of coronary heart disease in 2015 [4]. Studies have reported a 20%-45% increase in the incidence of CVDs in Iran over recent years [5]. If the current mortality trend persists, approximately 23.4 million people are projected to lose their lives from these diseases by 2030 [6].
Accordingly, myocardial infarction (MI) refers to a process in which a portion of the heart muscle undergoes permanent damage due to the cessation or reduction of blood flow [8]. As a manifestation of CVDs, MI most commonly occurs due to the thrombotic occlusion of an epicardial coronary artery [9]. Several risk factors contribute to the occurrence of MI, including modifiable risk factors (such as physical inactivity, smoking, poor diet, hyperlipidemia, and hypertension) and non-modifiable risk factors (such as age, sex, and family history) [10]. The diagnosis of acute MI presents physical health challenges and significantly affects patients’ mental health, leading to anxiety, depression, and uncertainty about future medical decisions and emergency treatments [11].
Considering the critical importance of CVDs and the aforementioned considerations, this study conducts a comparative epidemiological analysis of coronary artery bypass graft (CABG) surgery. The study focuses on assessing the changing characteristics of patients across two distinct periods (2018-2019 and 2020-2021) at Dr. Heshmat Heart Hospital in Rasht City, Iran, the only specialized cardiovascular hospital in Guilan Province, Iran. The findings of this study may provide valuable insights into demographic changes over time, allowing for appropriate planning to promote healthy lifestyle behaviors, manage controllable risk factors, and ultimately improve public health.

Methods
This analytical cross-sectional study was conducted on patients who underwent CABG surgery at Dr. Heshmat Heart Hospital in Guilan Province, Iran, between 2018 and 2021.
Patient data were collected using a structured checklist, which included information on age, gender, education level, place of residence, body mass index (BMI), smoking habits, underlying conditions (including diabetes mellitus, hypertension, hyperlipidemia [total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides], peripheral vascular disease [PVD], congestive heart failure [CHF], acute coronary syndrome [ACS], ischemic heart disease [IHD], MI, previous history of CABG, atrial fibrillation [AF], and other arrhythmias), and surgical outcomes such as stroke, coma, and mortality within 30 days post-operation.
Meanwhile, the data were analyzed using SPSS software, version 20. The distribution of continuous variables was assessed using histograms and Q-Q plots. Given the non-normal distribution of data, median and interquartile ranges were used to report continuous variables. The chi-square test, the Fisher exact test, and the Mann-Whitney U test were used for comparative analyses of categorical and continuous variables between the two time periods. A significance level of P<0.05 was considered statistically significant.

Results
The distributions of age, gender, BMI, smoking status, and place of residence were similar across the two study periods (P>0.05). The median and interquartile range (IQR) for patient age were 60 years (55-68) in the 2018-2019 cohort and 60.5 years (55-68) in the 2020-2021 cohort. The median BMI in the first period was 26.7 kg/m² (24.2-29.6) and 26.6 kg/m² (24.1-29.8) in the second period. In the first period, 69.3% (n=122) of patients were male, 57.7% (n=101) were urban residents, and 43.5% (n=74) were smokers.
A significantly higher percentage (40.4%, n=78) of patients in the second period were illiterate compared to the first period, which was statistically significant (P=0.014). Laboratory findings indicated higher fasting blood sugar (FBS), low-density lipoprotein cholesterol, and triglyceride levels in the second period, while high-density lipoprotein cholesterol levels were lower. The prevalence rates of diabetes mellitus, IHD, CHF, and MI were higher in the second period, although these differences were not statistically significant (P>0.05).
ACS, cardiac arrhythmias, and PVD were not reported in the first period but were observed in one patient in the second period. No cases of AF were reported in either period. The median and IQR for diastolic blood pressure were 75 mm Hg (70-80) in the first period and 80 mm Hg (70-85) in the second period, with a statistically significant difference (P=0.024).
A higher proportion of patients in the second period had hyperlipidemia (32.7% vs 19.3%), a history of CABG (7.7% vs 2.3%), and hypertension (39.4% vs 21.5%), all of which were statistically significant (P<0.05). The mortality rate was 5.1% (n=9) in the first period and 2.8% (n=5) in the second period. Although the mortality rate was lower in the second period, the difference was not statistically significant (P=0.123). Additionally, no cases of stroke or coma were reported in either period.

Conclusion
The findings of the present study revealed significant differences in certain demographic and clinical variables between the two study periods, while other variables remained unchanged. A higher proportion of urban residents compared to rural residents were affected by CVDs, possibly due to reduced physical activity and inadequate exercise patterns. Implementing proper planning strategies could help mitigate stressors associated with urban living.
Although literacy rates were expected to improve over time, a greater proportion of patients in the second period were illiterate, highlighting the need for national educational programs tailored to the illiterate population. Patients in the second period exhibited higher levels of blood pressure, lipid profiles, triglyceride, low-density lipoprotein cholesterol, and cholesterol suggesting a lack of awareness and adherence to medical follow-ups, emphasizing the need for continued patient education and intervention.
Moreover, an increase in smoking prevalence among patients in the second period was observed. Given the high rates of tobacco and substance use, public health officials must prioritize preventive measures and educational initiatives to curb smoking behaviors.
Despite previous studies on this subject, regional differences in disease epidemiology, lifestyle habits, and demographic characteristics necessitate localized assessments of cardiovascular risk factors. This study underscores the importance of tailoring educational programs, prevention strategies, disease screening, and therapeutic interventions to the specific population dynamics of each region.

Ethical Considerations

Compliance with ethical guidelines
This study was approved by the Ethics Committee of Guilan University of Medical Sciences, Rasht, Iran (Code: IR.GUMS.REC.1399.652). Due to the confidentiality of the information recorded in the patients' files, access to the patients' medical records was limited to the researchers only, and the results were published anonymously.

Funding
This study was supported by the Vice Chancellor for Research and Technology, Guilan University of Medical Sciences, Rasht, Iran.

Authors' contributions
Conceptualization and study design: Parand Pourghane; Data acquisition: Parinaz Shahroudi, Fatemeh Rahimi, and Laleh Godarzwand; Drafting of the manuscript: Parand Pourghane, Maryam Ghalandari, Parinaz Shahroudi, and Fatemeh Rahimi; Statistical analysis: Maryam Ghalandari; Data analysis, interpretation, review and editing: Parand Pourghane and Maryam Ghalandari; 

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank the officials of Dr. Heshmat Heart Hospital for their cooperation and provision of relevant information. Also, this project has been registered at the Cardiovascular Research Center of Guilan University of Medical Sciences, in the Vice-Chancellor of Research of Guilan University of Medical Sciences, and the researchers would like to thank this center and the Vice-Chancellor of Research.

References