Major lower limb amputation in peripheral arterial disease : treatment outcome, risk factors, and health-related quality of life

Abstract

Critical limb ischemia is the end stage of peripheral arterial disease. These patients have a high risk of amputation and death regardless of revascularization. One of the most important questions for the patient and the surgeon is the risk of amputation despite a revascularization attempt. Some patients with poor vascular anatomy may be better served by a primary below knee amputation than by a high-risk revascularization procedure. Furthermore, patients with critical limb ischemia that undergo an amputation have a high risk of stump complications and re-amputation. An amputation below knee is associated with more complications related to wound healing than an above knee amputation. On the other hand, a patient with an amputation below knee has a 50% higher chance to learn to walk compared to those having an above-knee amputation.

Mobility has been found to be an important factor for the patient´s Health-Related Quality of Life after an amputation. However, the association between mobility, use of prosthesis and perceived Health-Related Quality of Life among those amputated due to peripheral arterial disease is largely unknown. Furthermore, knowledge regarding the patients´ experience of the amputation decision and the first time after an amputation is sparse. Most of the performed studies consist of patients referred to a rehabilitation ward, resulting in a selection of healthier patients. As patients amputated due to peripheral arterial disease are older with significant co-morbidities, transferring results from studies of populations with trauma or cancer as indication is problematic.

The overall aims with this thesis was to study patient-related risk factors for amputation and re-amputation in patients revascularized for critical limb ischemia and to enhance the knowledge regarding the use of prosthesis, its impact on the patients’ perceived Health-Related Quality of Life, and their experience of having had an amputation. Paper I assessed risk factors for amputation in 855 patients amputated after a revascularization due to critical limb ischemia. It was a population-based cohort study using data from the Swedvasc Registry in 2009-2013 with follow-up data until 2017. Risk factors for amputation were assessed using a competing risk analysis and compared to a Cox’s proportional-hazards regression. Age (subdistribution hazard ratio [sub-HR], 0.98; confidence interval [CI], 0.97-1.00), preoperative ambulatory status (independent versus bedridden) (sub-HR, 4.10; CI, 2.14-7.86) and ischaemic wound versus rest pain (sub-HR, 3.03; CI, 1.72-5.36) were associated with an increased risk in the analysis using competing risk regression. In comparison, in the analysis using Cox regression, female versus male sex (hazard ratio [HR], 0.77; CI, 0.64-0.94), age (HR, 1.02; CI, 1.01-1.03), renal impairment (HR, 2.08; CI, 1.61-2.67), preoperative ambulatory status (independent versus bedridden) (HR, 3.45; 2.30-5.18) and ischaemic wound versus rest pain (HR, 2.41; CI, 1.78-3.25) were risk factors associated with an increased risk for amputation. Paper III was a prospective cohort study of 98 patients undergoing a major amputation due to peripheral arterial disease 2014-2018. The patients were included at the hospital in connection with their amputation. An interview regarding the patients’ functional level the week before the amputation as well as an assessment of Health-Related Quality of Life using the EQ-5D-3L questionnaire was performed at baseline. At the one-year follow-up a semi-structured interview by telephone was performed. Health-Related Quality of Life was measured using the EQ-5D-3L questionnaire. Prosthesis use and prosthesis wearing habit were evaluated using the Stanmore Harold Wood mobility scale and the Houghton scale. Out of the 73 patients that completed the one-year follow-up, 23 were classified as walkers. All patients had an increased Health-Related Quality of Life at follow-up in comparison to their baseline measure. The largest difference in EQ-5D-3L value index was in the group that walked with a prosthesis, 0.12 (IQR =0.09-0.36) at baseline compared to 0.78 (IQR=0.52-0.82) at follow-up, p<.001. Paper IV was an interview study of 13 patients who had undergone a major amputation due to peripheral arterial disease. The interviews were analyzed using content analysis and resulted in three themes: “From irreversible problem to amputation decision”, “A feeling of being in a vacuum” and “Adaptation to the new life”. The patients expressed a feeling of lack of knowledge of the process after the amputation and what to expect in the future. They did not feel that the healthcare givers had taken enough time to explain the whole process to them. Even so, the patients felt satisfied with their amputation decision, and some expressed that the decision should have been made earlier.

In conclusion: There is a risk for biased estimates using standard survival methods in cahoots with a high mortality. A competing risk regression that takes the competing event of death into account may improve the prediction of the actual risk of amputation. Patients with ischemic pain as indication for their amputation have a high risk of a re-amputation. Prosthesis use is important for the patients’ perceived Health-Related Quality of Life. Patients who walked or were able to use their prosthesis for independent movement had an increased level of Health-Related Quality of Life at follow-up compared to baseline. The patients need more information regarding the whole process of the amputation in order to increase their feeling of being involved in the care. To reduce unnecessary suffering and increase the patient´s Health-related Quality of Life, amputation may be presented earlier in the process as a treatment alternative.