DISCUSSION
The main finding of the present study is that surgery does not have a negative impact on the basal frailty status of patients referred for cardiac surgery. On the contrary, we have shown a significant improvement in the overall burden of frailty 6 months after surgery. This finding is true for both measurements that were employed to assess frailty, the Fried frailty scale and the CFS. In this way, we can confirm the dynamic and partially reversible nature of frailty in patients referred for cardiac surgery.
Changes or transitions among the ordinal levels of frailty is frequent in community-dwelling adults. As we get older, these transitions tend to occur towards a progressively greater degree of frailty. However, in frail patients who suffer a specific pathology for which there is an effective treatment, we could speculate that once this pathology has been treated effectively, the level of frailty will decrease to the extent that this pathology was contributing to it. For example, and focusing on cardiovascular medicine, the presence of heart failure secondary to a certain valve disease promotes a decrease in the level of the patient’s activity and energy consumption. These decrease in the individual activity can favor the appearance of a certain degree of sarcopenia, which constitutes a central etiological element in the frailty pathophysiology. These events will have a direct negative impact on each of the items that are evaluated by the Fried Scale, that is to say: slow walking speed, muscle weakness, low physical activity, low resistance to effort and weight loss. Conversely, once the valve disease has been successfully treated and, therefore, the situation of heart failure has been resolved, it is foreseeable that the postoperative scores obtained in the different frailty scales will be improved compared to the preoperative ones.
Our results are consistent with the previous arguments. Frail and pre-frail patients showed a clear improvement in their postoperative scores on four of the five items evaluated by the Fried scale. Conversely, none of the 26 patients classified as robust with the Fried scale presented significant deterioration in the scores evaluated by this scale.
The reversibility of frailty was first shown in studies at community level during the first years of the 21st century (27,28). As an example, in the study of Binder et al. (27), 152 sedentary community-dwelling people, with an average age of 83 years and with a previous screening of mild or moderate frailty, were randomized to perform various strength, balance and resistance exercises during 9 months. The individuals who performed the exercises showed a marked improvement in their previous frailty status, quantified by the modified PPT test (modified Physical Performance Test), and in their functional capacity measured through the basic and instrumental activities of daily life.
In the clinical setting and more specifically in the field of surgery, very few studies have focused on changes in the patient’s frailty status after the intervention. In 2015, McAdams et al. (29), with the aim to “study the natural history of frailty after aggressive surgical intervention such as kidney transplantation”, analyzed a prospective cohort of 349 patients who were assessed for frailty using the Fried scale before and after kidney transplant surgery. They showed that frailty was increased during the first postoperative month (going from 19.8% to 33%), but it recovered its previous prevalence during the second month and decreased in the third month (17.2%).
In the context of cardiac surgery, Jha et al. (20), published in 2017 a study analyzing the preoperative and postoperative frailty status of 100 patients in whom either a heart transplant was performed, or a ventricular assist device was implanted as a bridge to transplant. Similarly to our study, the authors found that most frail patients who survived the intervention showed a significant improvement in their frailty status two months after surgery.
Therefore, considering our results, we could add a decrease in the previous frailty status to the benefits provided by surgery, besides an improvement in functional capacity and quality of life. This improvement would translate into a lower risk for the occurrence of adverse health-related outcomes, such as falls, disability, need for hospitalization and dependency.
One limitation of the present study is the relatively low number de patients included, however, it has been enough to demonstrate a decrease in the global burden of frailty after surgery. Other limitation of the study is that the follow-up period is limited to 6 months. It would have been interesting to extend this period up to a year or more to see if this improvement in frailty is consolidated or, on the contrary, it tends to return to its preoperative values. As we have previously published (19), frail patients present higher postoperative mortality and morbidity rates. This could have led to a selection bias, as patients who died tend to present higher levels of frailty. However, this trend was only significative when frailty was assessed with the Fried frailty scale.