Acute aortic dissection after aortic valve replacement is rare, estimated to occur at a rate of 0.53-2.3%. The reported average interval from initial surgery to aortic dissection ranges from several days to over 10 years [1, 2]. The presumed cause of this condition is manipulation of the aorta during the initial surgery . Previous aortotomy or manipulations such as aortic perfusion, cardioplegia of the root, cross-clamping, etc. can cause intimal tears. On the other hand, while Fukuda et al.  reported that the common factor in all of his 6 reported patients was cystic medial necrosis of the aorta. However, histopathological examination of the excised aorta in our patients did not reveal any evidence of cystic medial necrosis.
Some of the possible causes of aortic dilatation prior to the AVR are infected aortic aneurysm or infective aortitis. Various microorganisms have been reported to be associated with this condition, most commonly staphylococci, enterococci, streptococci, and salmonella species . In our cases, the relationship between the preoperative aortic dilatation and infection remains unclear, however, histopathological examination did not show any evidence of inflammation caused by bacteria.
In a patient with marked enlargement of the aorta (>50 mm) at the time of the initial AVR, AVR plus ascending aortic replacement would be the gold standard. However, there is no consensus on whether a mildly dilated aorta (40-50V mm) should be surgically treated. Tsutsumi et al.  reported that aortic regurgitation combined with systemic hypertension, male sex, and a thinned or fragile aorta with mild dilatation (>45 mm) at initial AVR may be risk factors for late aortic complications. Albat et al.  reported that, in their series of 752 AVR cases, aortic dissection occurred in 0.53%, with the ascending aortic width being >55 mm at the time of the initial operation in 29% of cases. Based on their experience, they are performing prosthetic graft replacement for enlargement of the ascending aortic width to >55 mm, and systemic reinforcement with a Dacron mesh for enlargement of the ascending aortic width to 45-50 mm, concomitantly with the AVR. Both procedures have been shown to have long-term effectiveness. The results also appear reasonable from the point of view of consistent with LaPlace’s law. According to LaPlace’s law, the risk of further dilatation of the ascending aorta, aortic rupture, and aortic dissection definitely increases with increasing diameter of the ascending aorta. Even in the absence of structural damage of the connective tissue, graft replacement or size reduction surgery may be a promising approach.
However, most surgeons hesitate to perform AVR plus ascending aortic replacement in elderly patients who have poor cardiac function, because prolonged extracorporeal circulation may lead to cerebral edema, respiratory dysfunction, acute renal failure, and myocardial damage, which can increase the morbidity and mortality.
Currently, based on these experiences, we perform aortic plication with reinforcement using Teflon felt for enlargement of the ascending aortic width to 40-50 mm, concomitantly with AVR, however, the issue of reinforcement or reduction ascending aorotoplication requires continued re-evaluation because there are some adverse reports such as “under-the-wrap” aortic wall atrophy .