Aortic Disease
Acute Aortic Dissection in Progressively Aging Societies
2024 Volume 88 Issue 3 Pages 307-308
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2024 Volume 88 Issue 3 Pages 307-308
Acute aortic dissection (AAD) is a sudden tear of the aortic intima that allows blood flow into the aortic wall, separating the intima and media from the adventitia. It causes not only acute chest and back pain, but also life-threatening conditions such as cardiac tamponade, acute aortic regurgitation, aortic rupture, and coronary artery occlusion due to false lumen. The severity of AAD depends on its location; as classified by the Stanford system, “type A” involves the ascending thoracic aorta while “type B” does not. Although the treatment strategy in the acute setting is generally emergency surgical intervention for type A dissection and conservative treatment for type B, each patient should be treated according to the specifics of their condition by considering the occlusion of branch arteries, thrombosis in the false lumen, persistent symptoms, and general conditions. Although a small percentage of patients develop AAD before 60 years of age and have specific conditions such as connective tissue disorders (e.g., Marfan syndrome), in most cases patients are aged ≥60.1 Although much evidence has accumulated regarding the diagnosis and treatment of AAD, there is limited epidemiologic evidence regarding the incidence and mortality of this condition in the general population.
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Several studies on the incidence of AAD have been performed, mainly in Western countries.2–8 An early population-based study from Hungary reported in 2000 that an annual incidence in the general population was 2.9/100,000 populations and the mean patient age was 65.7 years.2 The largest study thus far, performed in Canada in 2018, included 5,966 patients and reported an annual incidence of 4.6/100,000 population with a mean patient age of 66 years.8 In 2021, Yamaguchi et al9 reported Japanese epidemiological data from Nobeoka City, Miyazaki Prefecture, Japan. Their study demonstrated that the annual incidence, adjusted by the age distribution of the whole population in Japan, was 17.6/100,000 population, with a mean age of patients with AAD as 75.9 years and the age-adjusted 30-day mortality rate as 9.9/100,000 populations.
In this issue of the Journal, Moriyama et al10 investigate the incidence and 30-day mortality rate of AAD in the population around Yatsushiro City, a well-defined geographic area in south Kyushu, Japan. Their study showed a crude incidence of 13.6/100,000 population (age-adjusted incidence, 11.4/100,000 population), and a crude 30-day mortality rate of 4.9/100,000 population (age-adjusted mortality, 4.0/100,000 population). Additionally, their study revealed that both the incidence of AAD and the 30-day mortality rate increased with age. In comparison with the previously noted reports, the results from Moriyama et al10 are most similar to those of Yamaguchi et al.9 Thus far, the annual incidence of AAD reported from Japan has been higher than reported from Western countries.
Besides racial and regional differences, what can account for this difference? One possibility is that patients with the acute aortic syndrome of intramural hematoma (IMH), often called the thrombosed type of aortic dissection in Japan,11 were included in the groups of patients with AAD in the both studies from Japan. By contrast, IMH is usually distinguished from AAD in Western countries, which might result in a lower incidence of AAD being reported in Western countries compared with Japan. Another possible explanation relates to the healthcare system in Japan. The high prevalence of computed tomography, the availability of public health insurance, and the accessibility of emergency hospitals may all contribute to a higher diagnostic rate, and thus a higher incidence. However, the main cause of this difference may be the unprecedented aging of society in Japan. The study by Moriyama et al clearly demonstrated an association between advanced age and a higher incidence of AAD. The mean age of patients with AAD calculated from the 2 Japanese studies was greater (75.1 years),9,10 than in the reports from Western countries (66.3 years).2,4–8 From 2010 to 2020, public statistics showed a 32% increase in the number of people in Japan aged ≥75 years (Figure),12 and a report based on the Japanese Registry of All Cardiac and Vascular Diseases-Diagnosis Procedure Combination (JROAD-DPC) database during this period indicated an increase in the number of patients hospitalized with AAD.13
Expected trends in population and the number of older patients with aortic dissection in Japan.
Does this epidemiological evidence provide insight into the incidence of AAD in the future? The elderly population in Japan is expected to continue to grow until 2050, and furthermore, the proportion of elderly people is expected to be higher in rural areas than in urban areas.12 As such, the number of patients with AAD in Japan is also expected to continue to increase, and this trend may be more pronounced in rural areas than in urban ones (Figure). Regarding the treatment of AAD, the guideline from the American College of Cardiology/American Heart Association14 emphasized the establishment of multidisciplinary aortic teams comprising cardiac surgical, vascular surgical, and endovascular specialists with extensive experience managing complex aortic disease; imaging specialists with expertise in aortic disease; anesthesiologists experienced in the management of acute aortic disease and cerebrospinal fluid drainage; and an intensive care unit experienced in the management of acute aortic disease. The epidemiological evidence gathered thus far should facilitate the appropriate distribution of these valuable medical resources to various areas based on their proportion of older individuals. This may be an ideal time to begin preparing medical systems for treatment of aortic disease in each region.
T.N. is a member of Circulation Journal’s Editorial Team.
