Cardiac surgery aims to prolong patients’ lives and reduce cardiovascular disease-related morbidity. Despite significant advances in these procedures, postoperative complications, including infections, remain important non-cardiac complications and are associated with increased morbidity, mortality, length of hospital stay, and healthcare-resource use.^(1–4) Preoperative patient preparation supports perioperative stability, helps prevent complications, and promotes favorable postoperative outcomes.^(1,5)

Postoperative infections may include surgical site infection, mediastinitis, urinary tract infection, primary bloodstream infection, gastrointestinal infection, pulmonary infection, and endocardial infection, with manifestations ranging from local inflammation and superficial wound infection to severe septicemia.^(1,3) Several risk factors are associated with healthcare-associated infections (HAIs), including age, nutritional status, diabetes mellitus, smoking, obesity, coexisting infections at other sites, length of hospital stay, mechanical ventilation, and breaches of asepsis.^(5,6)

The oral cavity contains numerous microorganisms; therefore, invasive dental procedures, oral hygiene, and chewing can cause transient bacteremia.⁽⁷⁾ In patients with altered immune responses or sites susceptible to infection, bacteremia may be a risk factor.⁽⁸⁾ Although the biological mechanisms are not fully understood, oral microbiota homeostasis is closely related to health status.⁽⁹⁾ Some studies^(10,11) have associated pulmonary infections and endocarditis with oral health; however, whether intraoral infectious foci before elective cardiac surgery influence the development of other post-surgical infections (PSIs) remains unclear.

To date, published guidelines have not provided conclusive information on key issues related to dental treatment for patients preparing for cardiac surgery, including which treatments should be performed before surgery, the optimal timing of dental treatment, and the risks and benefits of dental treatment before cardiovascular procedures.^(9,12) Several studies^(13–18) have evaluated the influence of dental treatment and oral health on cardiac surgery outcomes, and dental treatment has been considered beneficial for patients with cardiovascular disease, particularly those undergoing valve surgery or heart transplantation.⁽¹⁸⁾

At the Heart Institute of the Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (InCor-HCFMUSP), the Valve Surgery Group (VSG) routinely recommends dental evaluation as part of the preoperative assessment for all patients, whereas the Coronary Surgery Group (CSG) requests preoperative dental evaluation only in selected cases, such as suspected dental abscess or severe coronary artery disease. Thus, the InCor Dentistry Unit prepares patients scheduled for cardiac surgery by identifying and treating oral infectious foci. The protocol is based on detailed clinical and radiographic evaluation while considering each patient's systemic condition. Oral infectious foci may include carious lesions involving dentin, supra- and subgingival calculus, radiographically detected periapical lesions with or without signs of inflammation, residual roots, dentoalveolar or periodontal abscesses or fistulas, moderate to severe periodontal disease, teeth requiring endodontic treatment, and intraoral candidiasis. Dental clearance requires treatment of all identified infectious foci.

Therefore, this study aimed to evaluate the prevalence and clinical characteristics of post-surgical infections after elective coronary and/or valvular heart surgery at InCor and to examine the relationship between these infections and prior dental assessment before cardiac surgery.

This retrospective study evaluated the prevalence of post-surgical infection after elective cardiac surgery at InCor-HCFMUSP between January 2018 and April 2019. The study was approved by the Ethics Committee of Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (CAAE: 27224619.5.0000.0068; # 3.807.023).

A total of 1,886 surgeries were performed in 1,873 patients. Of these, 607 surgeries were excluded because they did not meet the inclusion criteria, leaving 1,279 surgeries in 1,274 patients. Patients were divided into two groups: the CSG, with 507 surgeries (39.6%), and the VSG, with 772 surgeries (60.4%). Patients who underwent both valve surgery and coronary artery bypass grafting in the same procedure were allocated to the VSG. Post-surgical infection occurred in 137 cases (10.6%), including 52 (4.0%) in the CSG and 85 (6.6%) in the VSG (Figure 1). No significant association was observed between infection status and type of surgery performed (p=0.5089) (Table 1).

Of the total sample, 716 patients (56.2%) were male; of these, 388 (76.5%) were in the CSG. Among female patients, 439 (57.2%) were in the VSG. Sex distribution differed significantly between the groups (p<0.0001) (Table 1).

The mean age was 59.8±13.2 years and was significantly higher in the CSG than in the VSG (63.5±8.9 versus 57.4±14.9 years, respectively; p<0.0001). In both groups, the most frequent comorbidity was systemic arterial hypertension (SAH), followed by dyslipidemia (DLP) and diabetes mellitus (DM). In the VSG, 52.5% of patients had SAH, 23.2% had DLP, and 17.2% had DM. In the CSG, 86.6% of patients had SAH, 53.65% had DLP, and 49.9% had DM; comorbidities were significantly more frequent in the CSG than in the VSG (p<0.0001). No significant association was observed between infection and comorbidities in either the VSG (p=0.4750) or the CSG (p=0.6222).

Among the studies identified in the literature, only the study by Hakeberg et al.,⁽¹³⁾ conducted in Sweden, used an approach similar to that of the present study. In that prospective study of 253 patients undergoing valve surgery, the authors concluded that dental treatment did not decrease the rate of immediate infections after valve surgery. However, they noted that the long-term consequences of prior dental treatment remained unclear. The sample size in that study was much smaller than ours; in addition, good oral health was reported in the studied population, largely reflecting the country's national dental health insurance system, which covers dental care—a context that does not apply to the Brazilian population.

According to epidemiological data collected by the InCor Dentistry Unit between 1995 and 2004, only 19.5% of 1,000 patients preparing for heart valve surgery had good oral health. Good oral health was defined as the absence of periodontal disease and the presence of at least 20 teeth, indicating that poor oral health was prevalent in this patient population. Although this condition may not be a risk factor for immediate post-surgical cardiac infections, it should not be neglected.^(13,15) Although bacteremia is not the only factor associated with infection, the removal of acute and/or chronic oral infectious foci may help restore oral health by reducing bacterial load and the frequency of bacteremia, thereby potentially contributing to the prevention of infective endocarditis and ventilator-associated pneumonia by supporting oral microbiota balance.^{(9,11,15,16,18,21)}

The most prevalent microorganisms in the infection processes affecting the study sample belonged to the genus Staphylococcus, which is frequently associated with SSIs⁽²²⁾ and is therefore less commonly found in the oral cavity. Sands et al.⁽¹⁰⁾ evaluated the oral biofilm microbiota of patients receiving mechanical ventilation and observed Staphylococcus aureus and Pseudomonas aeruginosa in 32.7% of evaluated patients, suggesting that dental plaque may represent a potential source of pathogens for ventilator-associated pneumonia; this condition is associated with changes in the oral microbiota due to factors such as reduced immune function and patient frailty.

Patients who underwent dental assessment had shorter hospital stays in both groups. This finding has not been reported consistently in previous studies. In a study conducted in Brazil, De Souza et al.⁽¹⁵⁾ showed that patients who underwent dental treatment before surgery had a longer hospital stay than those who did not undergo dental treatment (21.5 versus 14 days). Because the study group had characteristics similar to those of the present study population, their oral health status may also have been similar. However, the study by De Souza et al.⁽¹⁵⁾ included 481 patients, a smaller sample than that evaluated in the present study. Thus, because prolonged hospitalization is associated with higher hospital costs,⁽⁴⁾ this finding is relevant both clinically and economically.

Several studies have evaluated the risks of dental treatment in patients scheduled for cardiac surgery.^(14–18) For example, Nakamura et al.⁽¹⁸⁾ evaluated the risk factors associated with dental treatment before cardiac surgery, including extractions, in patients scheduled for valve surgery. The authors concluded that dental treatment had no significant impact on postoperative complication rates and could therefore be safely performed before valve surgery. Nevertheless, individual assessment remains essential for planning and determining the appropriate timing of dental treatment.^(13–18)

The infection rate observed in the present study was higher than that reported in high-income settings but compatible with rates reported in some low- and middle-income settings.^(1–3,6,22) In a study of 5,158 patients undergoing cardiac surgery in the United States, Gelijns et al.⁽²⁾ observed a 4.6% prevalence of post-surgical infection. In China, Jiang et al.⁽³⁾ found that 7.8% of 1,606 patients developed post-surgical infection, whereas in Brazil, Soares et al.⁽¹⁾ found that 18.1% of 204 patients developed post-surgical infection; the latter study had a smaller sample than the present study, which may partly explain the difference in results.

Most surgeries performed in the present study were valve surgeries, which differs from previous studies reporting a higher prevalence of coronary artery bypass grafting.^(1,5,23) This finding may be related to the characteristics of the hospital, which is a tertiary university hospital focused on highly complex cases.

Male sex, which was more prevalent in the CSG, is considered a risk factor for hypercholesterolemia and atherosclerotic disease.^(23,24) Hypertension, diabetes mellitus, and dyslipidemia are also risk factors for atherosclerotic disease,^(23,24) and these comorbidities were prevalent in the study sample. Female sex, which was predominant in the VSG, has been associated in previous studies with a greater predisposition to some valvular heart diseases.⁽¹²⁾ Some comorbidities, such as hypertension, may be associated with valvular heart diseases,^(12,25) as observed in the present sample. Although no association between comorbidities and infection was observed in the present study, some comorbidities, such as diabetes, may be associated with a higher occurrence of postoperative infection by impairing healing, contributing to vascular complications, and reducing host defense mechanisms.^(3,5,6,26)

The most frequently identified microorganisms were closely related to the most frequent infection diagnoses observed in both groups, consistent with the literature.^(2,27,28) The SSI rate was within the range reported in Brazilian studies but remained above ideal levels. These infections are considered preventable because they are associated with maintenance of the aseptic chain from patient preparation to the surgical team's intraoperative practices.⁽²²⁾ In high-income countries, SSI rates range from 1.2% to 5.2%, whereas in low- and middle-income countries, they may reach 11.8%.⁽²²⁾ In Brazilian studies, Andrade et al.⁽⁵⁾ and Soares et al.⁽¹⁾ reported SSI rates of 8.3% and 6.6%, respectively. By contrast, pneumonia is the most prevalent postoperative infection after cardiac surgery in high-income countries,^{(2–4,27,29)} as reported by Gelijns et al.,⁽²⁾ in whose study 2.38% of patients developed pneumonia.

Previous studies^(2–5,22) show that prolonged hospitalization and death are associated with infection, as observed in the evaluated sample. Greco et al.⁽⁴⁾ concluded that major HAIs increase hospitalization by an average of 2 weeks, and Jiang et al.⁽³⁾ reported mortality rates of 16.8% in infected patients and 2.7% in non-infected patients.

There is no significant relationship between pre-cardiac surgery oral health and chronic venous insufficiency; however, it should be considered that poor oral health can be a risk factor for the development of ventilator-associated pneumonia and late infections such as endocarditis. Therefore, dental treatment aimed at removing foci of infection is important. The prevalence of chronic venous insufficiency was low, with no difference observed between the groups studied. Further studies should be conducted to clearly establish the relationships between dental treatment and chronic venous insufficiency in cardiovascular surgeries.