4 | Discussion
Periodontitis has a high worldwide prevalence of 40 % - 50 %. This is not only important for oral health because there is increasing evidence that periodontitis can promote the development of atherosclerosis and subsequent diseases such as CHD. The majority of these previous longitudinal studies investigated patient groups without clinical symptoms of atherosclerosis or CVD at baseline . However, in two previous studies, an association between periodontal disease and recurrent cardiovascular events was shown . Therefore, it can be assumed that periodontitis may influence cardiovascular outcome after cardiac surgery. In this study, we examined whether periodontitis was associated with the incidence of new cardiovascular events after CAGB surgery. Different periodontitis classification systems were used in order to compensate disadvantages of a separate classification system. For instance, in both the CDC classification and the new classification system bleeding upon probing is not taken into account. However, in particular the area of the periodontal inflamed tissue may associate with the systemic inflammatory burden. For that reason, PESA and PISA were additionally determined as continuous values. PESA allows determining the amount of periodontal altered pocket epithelium whereas PISA allows determining the amount of inflamed pocket epithelium .
Among our test group, the prevalence of a severe periodontitis (71.3%, Table 1) was more than two times as high in comparison to the normal population because the “Fifth German Oral Health Study” revealed among younger seniors (65 to 74 year olds) a prevalence of 28.3% [39]. This result may support the importance of severe periodontitis in the pathogenesis of atherosclerosis and CHD. However, after cross-sectional comparisons and survival analyzes, we were unable to ascertain that clinical parameters of periodontitis, oral hygiene habits but also the caries index were significantly associated with the incidence of new cardiovascular events. Only a history of early tooth loss due to tooth loosening among first-degree relatives was associated with increased HR for new cardiovascular events. Regarding the internal parameters, a PAD and a previous myocardial infarction were significant and atrial fibrillation was marginally significant associated with a new event. Oral anticoagulants and antiarrhythmic drugs were also significantly associated with a new event, according to cross-sectional comparisons. Since both drugs are mainly given to patients with atrial fibrillation, no separate survival analyses were carried out.
The hypothesis that clinical parameters of periodontitis and oral hygiene habits influence the follow-up after CABG surgery has not been confirmed by our study. However, the association of a putative familial aggregation of periodontitis assessed as early tooth loss according tooth loosening with the cardiovascular endpoint could be important and should be replicated in further studies. The following hypotheses for this association are conceivable. At first, members of a family share conditions, e.g. less self-care, which promote periodontal disease and CHD. This hypothesis is contradicted by the fact that we could not demonstrate any significant differences in dental care and plaque index between the groups with and without the event. Secondly, this observation may indicate the existence of common genetic risk markers for periodontitis and CHD. A single nucleotide polymorphisms (SNPs) in long non-coding RNA ANRIL (antisense noncoding RNA in the INK4locus) were shown to be associated with both, CHD and periodontitis [. Interestingly, genetic variants of ANRIL was associated with the extent of elevated levels of CRP and new adverse events within three years follow-up in patients who had to be hospitalized for treatment CHD .
The positive association between PAD and cardiovascular outcome revealed in our study has been confirmed by others . It was shown that patients with PAD had in particular poorer long-term survival rates after CAGB surgery than patients without PAD . The association between PAD and long-term survival after CABG may have several explanations. PAD may be a marker of more severe atherosclerosis and subsequent diseases such as CHD. Another possibility is that in spite of successful CABG surgery, the risk of noncardiac mortality may be increased . Chue et al. found among patients with PAD a higher incidence of comorbidities and they were generally sicker than patients without PAD .
In our study, a history of myocardial infarction was associated with a higher incidence of new adverse events after CABG surgery. Another study supported our results. A history of MI was associated with increased mortality during the first 30 days after CAGB surgery but not thereafter. Furthermore, patients with a history of MI developed more frequently a new MI. Moreover, a previous MI was also associated with a longer total hospital stay mainly caused by new MI, angina pectoris and congestive heart failure .
In our study, we observed a higher incidence of postoperative events in patients with preoperative atrial fibrillation. This result is also supported by further studies . Preoperative atrial fibrillation was found associated with increased late cardiac morbidity and mortality, poor long-term survival, higher risk of all-cause mortality, and congestive heart failure.