Introduction

Noncommunicable diseases (NCDs) accounted for seven of the ten leading causes of global mortality between 2000 and 2019, with a predominance of cardiovascular diseases, respiratory conditions, and neonatal disorders. Among these, ischemic heart disease was the leading cause, responsible for 16 % of deaths, with an increase of more than two million deaths during the analyzed period ¹.

In Brazil, the national epidemiological profile reflects this scenario, where cardiovascular diseases (CVDs) have been the leading cause of death. Between 1990 and 2019, ischemic heart disease (IHD) remained the primary cause of mortality, the most prevalent condition was acute myocardial infarction (AMI) ².

Early diagnosis is crucial to guide patients toward the most appropriate therapeutic approach, which range from minimally invasive procedures, such as cardiac catheterization and/or angioplasty, to more complex and highly invasive interventions, such as coronary artery bypass grafting (CABG) ³.

CABG is a highly invasive open-heart surgery that entails greater tissue trauma, longer hospitalization, and a more demanding rehabilitation process, requiring structured pre- and postoperative care to optimize outcomes ³. It aims to restore the heart's functional capacity and reduce symptoms by optimizing blood perfusion to the myocardium ⁴ and is indicated when there is no possibility of clinical treatment or less invasive techniques, such as MICS-CABG, TMR, or PMR ⁵. This surgical experience triggers intense emotional responses, which are characterized by fear of the disease progressing, uncertainty, and psychological distress, which affect both patients and their families throughout the perioperative period.

In the postoperative phase, individuals undergoing CABG may experience feelings of restlessness, fear, vulnerability, and insecurity, with difficulties to adapt upon returning home ⁶. Moreover, the system of beliefs and values acquired throughout life can interfere with the recovery process.

Adequate access to health information enhances knowledge and strengthens skills essential for postoperative self-care, thus promoting the adoption of behaviors that facilitate lifestyle modifications. Participation in structured educational interventions, such as cardiac rehabilitation programs, has demonstrated to significantly improve patients' understanding of surgical wound care, management of postoperative complications, and adjustment to the challenges imposed by cardiac surgery ⁷.

It is necessary to link actions aimed at promoting health and preventing complications in patients undergoing CABG to facilitate their recovery. Therefore, the identification of aspects related to disease knowledge and understanding of behaviors related to their health and illness, understood as health literacy (HL), are necessary to improve quality of life and help in the elaboration of ways to prevent or early detect complications ⁸.

HL is defined as a set of skills developed by searching, under- b standing, and coding health information for incorporation and = appropriate daily decision-making, using a three-dimensional f approach: Functional literacy (skills to read and write); interactive literacy (understanding of information and meanings of different forms of communication, as well as its applicability in the execution of daily tasks); and critical literacy (ability to critically analyze the information received) ^9-10.

Faced with the complexity of analyzing HL, disease knowledge and the challenges of the rehabilitation process for this profile of patients, it was proposed to conduct a mixed-methods study ¹¹. This method allows answering the research problem with a broad approach since its purpose is to obtain different and & complementary data on the same topic, in addition to allowing triangulation between quantitative and qualitative methods. Therefore, it possible to directly compare quantitative statistical results with qualitative findings and development a more complete understanding of the subject under analysis.

Thus, the following research questions emerged: Is there a relationship between knowledge of disease and HL in the late postoperative period of cardiac surgery due to infarction? What are the challenges experienced during the cardiac rehabilitation process? This research aimed to analyze disease knowledge and HL in the late postoperative period of cardiac surgery due to infarction, as well as to recognize the challenges experienced in the rehabilitation process.

Method

Results

Qualitative Phase

The qualitative phase included 24 interviews, with 90.23 % of the text analyzed using the Descending Hierarchical Classification technique (DHC) in the IRAMUTEQ®. The corpus was grouped into five lexical classes: Class 3 (29.4 %) informed the category (Mis)guidance and (mis)information related to care; Classes 5 (21.4 %) and 4 (19.3 %) supported Daily life transformed by the surgical procedure; and Classes 2 (13.9 %) and 1 (16 %) related to Feelings experienced during the surgical process and cardiac rehabilitation. The robust distribution of segments among these classes reflected and validated the thematic framework interpretive analysis.

Source: Prepared by the authors.

Figure 1 Phylogram Generated from the Descending Hierarchical Classification of Interviews with Participants Residing in the Western Paraná Mesoregion, Brazil, 2023. (n=24) 

Figure 2 presents a combined representation of the QUAN + QUAL results, highlighting the areas of convergence and divergence between the CADE-Q SV and HLAT-8 scores and the participants' narratives. This integration allows for a deeper understanding of the health literacy and knowledge profiles of individuals undergoing CABG in the Western Paraná mesoregion.

For example, although the participants demonstrated reasonable clinical knowledge (average = 6.38), their low score in the IUS domain (average = 1.35) and their testimonies suggest that their health knowledge is based primarily on personal experiences rather than a formal understanding. Similarly, despite their recognition of behavioral causes of disease, the low score in Risk Factors (average = 4.88) suggests a limited understanding of disease prevention, which is reflected in ambivalent or contradictory attitudes, expressed in the interviews.

Divergence was also observed in the domains Physical Exercise and Diet: Participants presented high scores in these areas (average = 7.5 and 11.75, respectively), but reported maintaining unhealthy bey haviors after surgery. This points to a gap between knowledge and behavioral change. Finally, although knowledge about psychosocial risk was moderately good (average = 5.38), the emotional burden reported in the interviews reveals significant psychological challenges, reinforcing the importance of addressing emotional literacy in cardiac rehabilitation.

This joint presentation corroborates the dialogic nature of mixed methods research, highlighting how qualitative data can explain or contrast quantitative findings, enriching interpretation and providing insights into the complexity of health literacy and behavior.

Source: Prepared by the authors.

Figure 2 Joint display articulating QUAN and QUAL results based on participants' statements and CADE-Q SV and HLAT-8 scores. Western Paraná mesoregion, Brazil, 2023. (n=24) 

Discussion

This study analyzed CAD knowledge and HL in individuals with infarction and late CABG, in which challenges in the rehabilitation process were identified through a mixed-methods approach. It can be highlighted for ¹ using CADE-Q SV to assess disease knowledge in a South American population; ² applying a mixed-methods design, as in Brawnwe et al. ²²; and ³ integrating HLAT-8 and CADE-Q SV in a post-infarction and CABG population.

The results of this study indicated that participants had difficulties understanding health information since they had unsatisfactory levels of HL. These data corroborate the study conducted in Denmark with 15,728 people, with four out of 10 people reporting difficulties in accessing, understanding, and applying health information. From these, 8.18 % had inadequate HL and 30.94 % showed problematic HL levels ²³.

The H L domains that scored the lowest in this study were related to understanding health information and critical literacy. Such results show difficulties in understanding disease care guidelines and health information, as well as interfering with the ability to select safe health information on the internet.

Our findings corroborate the results of a survey conducted with 1,700 Americans regarding information linked to social networks about COVID-19. The American study highlighted that people with limited HL had difficulties identifying the veracity of health information posted on media channels ²⁴. While media platforms can disseminate information and educate people to take public health action, they can also lead to misinformation and misguidance ²⁵.

Our study found no statistically significant difference between HL and CAD knowledge in relation to sociodemographic characteristics. In line with a study conducted with 76 participants, with acute coronary syndrome (ACS), in which 85.5 % obtained inadequate HL, regardless of their level of education ²⁶. However, other authors agree that education levels and sociodemographic variables influence all dimensions of HL when associated with a higher prevalence of risks ^27-28.

It is important to emphasize the conceptual differences between HL and health education; the first is a multidimensional concept, related to a set of skills and competencies, which can be developed through the second (education) ²⁹. Therefore, social determinants tend to interfere with the development of fundamental skills necessary for HL, as they influence the health information used by patients ^30-31.

As for CAD knowledge, in CADE-Q SV, despite participants having unsatisfactory HL, they had good knowledge about the disease. The areas with the most knowledge were Diet, Physical Exercise and Clinical Knowledge, with lesser knowledge regarding areas of Psychosocial Risk and Risk Factors ³².

These findings corroborate the results observed in the Persian validation of the CADE-Q SV from English to Farsi, where the highest and lowest scores of patients' knowledge were attributed to the areas of Nutrition and Psychosocial Risk, respectively ³², which were also evidenced in this study. Similar results were found when validating the CADE-SV for Brazilian Portuguese and French-Canadian. The area with the greatest knowledge was related to Risk Factors and Diet, with less knowledge on Psychosocial Risk ³³.

However, this study partially diverges from these previous findings, suggesting that variations in knowledge levels across different domains may be influenced by cultural and lifestyle differences among populations ³².

HL in CAD influences outcomes through behavioral changes shaped by beliefs, perceptions, and sociocultural factors. A Chinese study found that greater disease knowledge was associated with lower adherence to healthy behaviors, while inadequate HL correlated with greater use of health services and acceptance of medical recommendations ³⁴, thus diverging from the findings of this study.

Despite lower scores in the risk factors domain of the CADE-Q SV, participants recognized determinants of their illness but maintained unhealthy behaviors such as smoking, alcohol use, and sedentarism. These findings are consistent with studies showing adherence to pharmacological treatment despite persistent risk factors ³⁵, and with evidence linking HL to physical activity, but not to smoking or alcohol consumption ³⁶.

Proper management of lifestyle-related risk factors, which can be changed, requires people to gain some understanding of their disease. Thus, low HL and low health education are associated with a higher prevalence of risk factors ²⁷. Therefore, a process centered on the person and their needs for cardiac rehabilitation, which considers the barriers and profiles of HL, becomes determinant for effectively targeting and providing services ³⁶.

In a systematic review with meta-analysis, covering 17 studies conducted in 12 countries in five continents, it was observed that inadequate HL was highly prevalent in patients with CAD, while was associated with a higher risk of CVD, thus reinforcing significant changes in relation to the self-care of patients through educational interventions ³⁷.

It should be noted that HL may be a consequence of AMI, which is a recurrent cause of hospital admissions; however, it is sensitive to interventions by primary services ³⁸, which must be an interconnected network to provide comprehensive care.

The absence of communication and formal protocols between primary and specialized care leads to discontinuity after hospital discharge, making patients and families responsible for seeking information and managing care needs ³⁹, results also found in this study.

Integrated data analysis highlighted the challenges experienced by participants in the late cardiac rehabilitation process. Most reported weaknesses in accessing health information and guidance during the recovery phase, in line with HLAT-8 data, in which participants had unsatisfactory HL. However, they were not usually seeking information or health guidelines and had difficulties understanding them. Furthermore, the information and guidance given at discharge had little impact on the rehabilitation process.

Finding health information and critically assessing health are decisive skills for those with multiple chronic illnesses since they need multiple sources of information to understand and cope with each of their illnesses ⁴⁰. The difficulty in understanding health instructions can lead to a lack of self-confidence in the ability to practice self-care, constituting a detrimental factor for compliance with treatment ⁴¹.

Another important finding concerns participants' low knowledge of psychosocial risks, as it is known that CABG is a procedure full of feelings of doubt, fear, and uncertainty, before and after the surgical procedure. Stress was identified in participants' statements and CADE-Q SV as a risk factor for a cardiac event, being considered as important as DM and hypertension.

A recent study with 190 patients followed for three months after cardiac surgery identified that 14.7 % presented elevated levels of depression, anxiety, irritability, and dyspnea ^42-44, which corroborates this study's findings. Nursing guidelines at discharge can reduce postoperative stress, as interaction with health professionals and family support positively influence care perception, clarify doubts, and promote self-care ⁴⁵.

Conclusion

This study identified acceptable levels of CAD knowledge and unsatisfactory HL among individuals who underwent post-myocardial infarction and CABG. The primary challenge observed in the rehabilitation process was the difficulty in understanding professional healthcare guidelines necessary for lifestyle changes.

The integration of quantitative and qualitative data revealed important divergences between knowledge acquisition and health behaviors, highlighting barriers to effective self-care. Emotional challenges, limited understanding of risk factors, and discontinuities in care transitions further complicate the rehabilitation process.

These findings underscore the need for nursing interventions that assess HL and disease knowledge to design individualized educational strategies, aimed at promoting behavior change, preventing complications, and supporting long-term recovery. Incorporating HL assessment tools into the routine of nursing care is essential to optimize patient outcomes after cardiac surgery.