## 4 Discussion
Individual clinical data could explain the contributions of severity of disease per country, but they are not available at the national level. The striking increase in Croatia can partly be explained by the higher availability of technological and human resources, patient preferences, the extent and application of specific non-invasive diagnostic procedures that enhance downstream testing, and the implementation of evidence-based guidelines [40]. In the 1990s and early 2000s, Croatia faced a shortage of invasive cardiologists and equipment, but nowadays, interventional cardiology services are widely employed in public and private settings [41]. Still, evaluation of treatment effectiveness and clinical outcomes, especially those from medium to long-term post-TCA periods and hospital mortality rates, are not routinely available. Nevertheless, the appropriateness of TCA indications and the extent of potential overutilization in clinical practice is the first to be addressed. There is a worldwide trend of overuse, but similar studies in Croatia have not been conducted [42]. In Italy, the rate of inappropriate TCA and coronary angiography is estimated at 22% and 30%, respectively, as in Spain [43; 44]. There is a lack of agreement regarding the fundamental definition of this scientifically understudied problem in interventional cardiology. However, some clinical, financial, cultural, and legal drivers of overuse have been previously recognized [45]. Financial interest does not need further clarification since more interventions mean more direct and indirect financial benefits. Regarding clinical issues, TCA is questioned in patients with stable IHD since they can have more benefits from medications or even CABG. Also, secondary prevention with optimal medical therapy has proved its worth compared with TCA [46; 47]. Recommendations to reduce overuse require guidelines, a country-specific approach with comprehensive data extraction from hospital databases, and a willingness to conduct economic and cost-effectiveness analyses of invasive cardiology treatments to avoid insufficient cardiovascular care. Also, exposure to unnecessary risk could result in unwanted clinical outcomes and the additional financial burden that continuously strains healthcare budgets. The TCA:CABG ratio represents an effort to quantify the utilization of cardiological interventions. This indicator was previously used as a parameter of potential overutilization of TCA and as a predictor of in-hospital mortality of patients with acute coronary syndrome [48]. All countries continuously and significantly increased the TCA:CABG ratio in the 2011-2019 period: Croatia at +8.9%, followed by France at +5.1%, Italy at +3.5%, Slovenia at +3.1%, and Spain at +2.2% (Figure 9). The high-to-low ratio for France vs. Slovenia was 1.74. Still, a detailed TCA:CABG ratio analysis requires evaluating the numerator and denominator. For example, the highest ratio for France can be explained by the augmentation of the TCA rate and reduction in CABG procedures. On the other hand, Croatia simultaneously increased both rates, TCA and CABG, and had lower ratio values. Although the TCA:CABG ratio alone cannot provide accurate conclusions about the overuse of TCA or CABG, it can be indicative and used to quantify the intercountry differences. IHD causes the most deaths in all analyzed countries [49; 50; 51; 52; 53]. This study showed significant health gaps among Mediterranean old and new EU country members, especially in standardized mortality and medical intervention rates. These differences are most likely associated with differences in prevention, constantly facing obstacles such as the lack of political will, competing financial and commercial interests, and missing the focus on social determinants [54]. Unlike prevention, medical interventions can be easily pharmacy-driven, especially in countries without cost-effective preventive strategies and mandatory monitoring of health outcomes, such as Croatia.