Changes in Patient Characteristics of Infective Endocarditis with Congenital Heart Disease: 25 Years Experience in a Single Institution

Infective endocarditis (IE) is a disease that can cause serious complications, and the risk of IE is higher in patients with underlying heart disease.1) Over the past several decades, IE was commonly associated with rheumatic heart disease and degenerative valvular heart disease. However, the profile of IE has since changed, with an increasing prevalence of IE among congenital heart disease (CHD) patients.2-4)

Reports on the clinical features of CHD with IE in different countries5), 6) indicate that the occurrence of IE has different features according to medical status, culture, and the region involved.7-9)

In Korea, there has been an increased survival rate of patients with CHD, but little is known about the occurrence of IE in these patients. Therefore, we reviewed cases of IE over the past 25 years at a single institution, and studied the change in theclinical profiles of IE in patients with CHD.

The treatment outcomes of patients with CHD have dramatically improved over the past several decades, with an increase in longterm survival. This has resulted in an increased number of CHD patients diagnosed with IE.3) CHD has been reported as 9-28%,3), 5) and 17-26%11), 12) of the causes of IE in Korea, suggesting a causative role of CHD in IE. In our study, 28.6% of patients diagnosed with IE had underlying CHD. The high prevalence of IE at our institute compared to the other domestic institutes, in part, results from the increased survival rate of CHD patients due to improved treatment methods, as well as the increased number of patients undergoing long-term follow-up at our institute, which runs a CHD center.

Patients with CHD have a possibility of IE in their lifetime, but the occurrence rate differs according to the type of CHD. Uncorrected VSD patients showed a high risk for IE13-15) and, in our study, VSD was the most commonly observed underlying CHD in both groups A and B. However, the larger percentage of patients with a cyanotic complex cardiac anomaly were observed in group B. This was likely due to an improvement in the early detection of CHD and improved surgical techniques, such as use of prosthetic materials, with patients consequently undergoing those procedures earlier in life. Consequently, there was a decreased risk of IE due to unrepaired simple CHD and the improved long-term survival rate of patients with a complex cardiac anomaly. The differences between the two groups are probably due to the improved treatment modality and improved treatment outcomes.13), 16)

In the year 2000, the year that divides the two study groups, Korea implemented a nationwide systemic change, separating the prescribing and dispensing of pharmaceuticals, and regulating the use of antibiotics under national guidelines.

Previous studies have shown that 2.5-31% of IE patients did not have an identified microorganism in the blood culture.17) This is less than the 37.6% found in our study, and although we found no statistically significant differences between group A (44.1%) and group B (26.5%), we noticed a decreasing trend in group B. Considering that the most common cause of non-identifiable microorganism in IE is antibiotic use prior to acquiring a blood sample, the changed health system regulating the use of antibiotics may be associated with this change.

The prevalence of IE due to Staphylococcus has previously been reported as having increased in patients who underwent previous cardiac surgery, compared to IE due to viridians streptococci.18) In our study, the most common pathogen of IE was viridians Streptococci in both groups, and IE due to Staphylococcus was comparably low. However, the prevalence rate of Staphylococcus infection in group B indicated an increase. IE due to fungus was reported to be dominant in patients who had previously undergone open heart surgery, were exposed to the long-term use of broad spectrum antibiotics, and had had intravenous catheter insertion.19) IE due to fungus has previously been shown to be increasing,20) but our study showed a decreasing tendency.

The most common complication reported in the literature was heart failure, at 15-65%,21) which appears to be in line with the findings of 31.2% in our study. However, the number of patients who underwent a surgical correction of IE due to uncontrolled infection after the intravenous injection of antibiotics increased in group B to 29.4% (compared to 5.1% in group A), and this was higher than the 14%22) reported previously. Given that the indication for surgery is "uncontrolled infection", surgical correction of IE has also increased in recent years. Mortality has been reported as between 7% and 8%,15), 23), 24) but we found an overall lower percentage (5.3%), although the mortality rate increased to 11.7% in group B. These results probably reflect the increased number of patients undergoing palliative treatment or prosthetic material surgery. Consequently, there was an increase in the number of IE high-risk patients16) and likely an increase in uncontrolled infection, leading to a higher rate of surgical correction among IE patients.

This study has a number of limitations. Our study was a nonrandomized controlled trial conducted retrospectively by reviewing medical records, which may not properly reflect the medical technology status, environmental changes, and societal changes and their ramifications. Furthermore, we lacked data on antibiotic prophylaxis before high-risk procedures, such as dental procedures or gastro-intestinal tract manipulation. However, this study is meaningful in that a single protocol was able to be evaluated over a long period of time at a single institute.

In conclusion, IE and CHD present a close correlation, and the profile of IE patients can change according to the tendency of an early correction for CHD and the development of diagnostic modalities. These changes were likely due to an increase in the long-term survival rate of patients with complex CHD and an improvement in surgical techniques, such as the use of prosthetic materials. Ongoing reassessment and the systematic management of these patients is crucial in the prevention and treatment of IE, especially for patients with complex CHD.