DISCUSSION
Life expectancy is increasing steadily in many countries and consequently presents a higher incidence of cardiovascular diseases, including ATAAD,13, 14 which remains a potentially lethal clinical presentation as emergency surgery is still a challenging procedure for elderly patients. It has been reported that surgical risks are increased in the elderly and old age is a negative prognostic factor of early mortality after emergency surgery for ATAAD.2, 3, 15, 16 However, surgical outcomes for ATAAD have been improving in Japan 17 as well as in the rest of the world18, with several studies reporting good results from the surgical repair of ATAAD in elderly patients.4, 13 Surgical outcomes in elderly patients with ATAAD may improve in this decade. Postoperative physical activities may be strongly associated with quality of life, mental health, and functional capacity in elderly patients with ATAAD.8It is reported that walking difficulty is an important risk factor for mortality and morbidity in patients after elective cardiac surgery.6, 19 However, there are few studies that assess physical activities or rehabilitation outcomes in elderly patients after surgery for ATAAD.
This study demonstrated that: 1) there were no significant differences in short-term and long-term mortality and major postoperative complications between patients undergoing surgical repair for ATAAD in the elderly group and in the control group; 2) during rehabilitation, it took significantly longer for elderly patients to walk 100 or 200 m and to require speech and swallowing therapy postoperatively for dysphagia; 3) the AUC of the 200-m walk after surgery as a prognostic indicator for late mortality was 0.878, with a highest accuracy at 30 days (sensitivity = 83.3%, specificity = 91.8%); 4) intriguingly, postoperative walking difficulty was an independent risk factor for late mortality in patients regaining ambulatory autonomy at discharge as well as in all cohorts.
It is still unclear what specific types and intensities of rehabilitation may be postoperatively safe and beneficial for patients with ATAAD. In this study, cardiopulmonary exercise testing or invasive walking tests were not performed to assess physical activities because the safety and efficacy of these tests have not yet been fully established in patients with postoperative residual aortic dissection for ATAAD.7, 20 However, we assessed the duration for the patients to walk 100 or 200 m postoperatively, which is less invasive and helps to assess postoperative physical activity resumption with ease compared with cardiopulmonary exercise testing or other walk tests.
Corone et al reported 33 French patients with type I DeBakey aortic dissection (mean age, 55.1 years) who underwent cardiac rehabilitation soon after surgical repair.21 They reported that noncontact aerobic activity with moderate intensity is likely safe and effective for patients with surgical repair for ATAAD. In this study, our rehabilitation program was based on walking exercise. During rehabilitation, acute elevations in BP may transiently increase the risk of recurrent aortic dissection or rupture after surgical repair for ATAAD,22, 23 because a postdissection aorta is almost invariably dilated and may have increased associated wall stress compared with a nondilated aorta.24 During rehabilitation in our study, sBP was strictly controlled between 100–130 mmHg with antihypertensive drugs without any aortic event, which may support the safety profile of our rehabilitation program. Elderly patients required fewer antihypertensive drugs to control blood pressure during the rehabilitation. Because BMI in the elderly group was significantly lower than the control group, small body size and older age in the elderly group may affect pharmacological metabolism.
The most obvious limitations of this study were its retrospective nature, small number of participants, and single-center design, which are potential sources of bias. In addition, although the majority of patients showed preoperative independence in activities of daily living in this study, patients with impaired physical activity may not have been transferred to our hospital because the family or patients did not want surgical treatment or because they were assessed as inoperable by former doctors. Furthermore, the mean follow-up period in the elderly group was comparatively short (median 42.5 [18.8–75.8] months; range 1–125 months), although we did not find significant differences in long-term follow up between the elderly group and the control group. Further studies with a larger number of patients, longer observation time, and greater emphasis on hemodynamic and biomechanical parameters should be performed to evaluate physical activities and surgical outcomes in elderly patients with ATAAD.