DISCUSSION
We showed that:
In AR patients over 65 years of age, aortic cusp bending was the most frequent AR etiology. On the other hand, in the younger patients, bicuspid AV was the most observed cause of AR.
Aging was the only significant factor to predict coexisting cusp bending of AV.
Cusp bending could occur in any AV cusp, nevertheless, it was detected on RCC by far the most frequently (45 out of 49 cusp-bending related cases). This was consistent with the previous study, reporting that 70% of the isolated cusp bending was seen on RCC (9). Roberts et al. reported that the most frequent cause of AR was “unclear”, accounting for 34% (3). The characteristics of the AR patients with “etiology unclear” were higher age with atherosclerotic diseases, in common with the cusp-bending group in this study. Higher age may also contribute to the result that the patients in this group were shorter in height with smaller body surface area. Recent improvement in TEE image quality has helped to detect cusp-bending more clearly, which may have been included in “etiology unclear”. Aging is associated with degenerative changes in cusps in various signaling pathways of molecular levels (14). In this study, however, there were no differences between those with and without cusp-bending in terms of the prevalence of atherosclerotic factors such as hypertension, diabetes, lipid disorder, CKD and smoking. Most of the patients in this study had various atherosclerotic diseases originally, and aging is considered the most influential contributor to occurrence of cusp bending above all. Although the number of patients with mitral prolapse was small (4 of 126 patients), they were detected only in cusp bending group, which may be associated with valvular vulnerability in patients with cusp bending.
There are several classifications of AR, and adaptation of the Carpentier classification originally designed for the mitral valve have been described for AR and can be helpful to understand the mechanism of AR, to guide valve repair technique, and to predict recurrence of AR (15). This scheme classifies dysfunction based on the aortic root and leaflet morphology. Cusp bending belongs to type II, cusp prolapse, in this category. As shown in this report, AV cusp bending may have favorable surgical repairability and outcome such as freedom from bleeding events caused by anti-coagulants or IE (9). Therefore, it is important to detect cusp bending preoperatively.
There are some limitations in the present study. This is a single center study and the number of patients enrolled in this study was relatively small. Secondly, 10 cases (7.9%) were classified as echocardiographically normal finding (Table 2). Even without any abnormality on AV cusps, AR can be generated from imbalanced sizes of aortic annulus, Valsalva sinus and ST junction (16) (17), which may be beyond echocardiographic resolution capability. Further investigation will be required for the validation of our study.