Lumbar Sympathetic Radiofrequency Ablation for Peripheral Arterial Disease: Considerations Regarding Patient Selection and Interpretation of Short-Term Outcomes [Letter]

Dear editor

We read with interest the recent study by Lv et al examining lumbar sympathetic radiofrequency ablation (LSRA) in patients with peripheral arterial disease (PAD).¹ The authors appropriately present their work as a preliminary, hypothesis-generating pilot study and acknowledge the limitations related to its retrospective design, small sample size, absence of a comparator, and short follow-up. Nevertheless, we believe that three aspects of the study merit further clarification because they directly affect how the observed short-term changes should be interpreted.

First, the clinical position of LSRA within the treatment pathway depends strongly on the revascularization status of the included patients. The eligibility criteria allowed enrollment of patients who were refractory to at least three months of conservative management or were considered unsuitable for surgical or endovascular revascularization.¹ These criteria may identify clinically different populations. Among the 14 patients with atherosclerotic occlusive disease, 13 were classified as Rutherford grade 4–6.¹ Current PAD guidelines recommend surgical, endovascular, or hybrid revascularization in patients with chronic limb-threatening ischemia when feasible, whereas lumbar sympathectomy is described as a palliative procedure in patients for whom revascularization is not an option.² Therefore, knowing how many patients in the present cohort were truly considered unsuitable for revascularization is important for determining the potential clinical role of LSRA. It would be useful for the authors to clarify the number of patients who were anatomically unsuitable for revascularization, had prohibitive procedural risk, had undergone unsuccessful previous revascularization, or were included solely because symptoms persisted despite conservative treatment.

Second, attribution of the day-7 physiological changes specifically to LSRA warrants caution. The authors report that routine postoperative symptomatic treatment, including pharmacotherapy intended to improve microcirculation, was administered before skin temperature and perfusion index (PI) were reassessed on postoperative day 7.¹ Thus, the same observation period used to evaluate the physiological effect of LSRA also included an intervention directed toward microcirculation. Previous studies of sympathetic interventions have used changes in skin temperature, peripheral blood flow, or PI as indicators of sympathetic blockade or procedural response.^3,4 For example, Wang et al measured plantar temperature and PI shortly after lumbar sympathetic radiofrequency thermocoagulation and used their increase as part of the definition of procedural success.³ In the present study, however, the contribution of LSRA cannot be separated from that of the concomitant postoperative treatment at the day-7 assessment. We therefore believe that clarification of the medications administered, their timing, and whether immediate post-ablation temperature or PI measurements were available would strengthen interpretation of the physiological findings. Future studies may also benefit from standardized background therapy and predefined measurements before additional microcirculation-directed treatment.

Third, we suggest greater caution in describing the observed changes as clinically meaningful solely based on standardized effect-size classification. The authors report a 0.90°C increase in toe skin temperature and a 1.02 increase in PI and state that large Hedges’ g values indicate that these changes were “clinically meaningful in magnitude”.¹ Standardized effect sizes quantify the magnitude of an observed difference relative to variability, but their clinical importance depends on the clinical context and the meaning of the underlying outcome.^5,6 Notably, the effect-size thresholds cited by the authors were proposed as tentative interpretive reference values and were explicitly intended to be considered alongside contextual factors.⁶ Moreover, thresholds derived from distributions of effect sizes in pain research should not necessarily be assumed to define clinical importance for physiological outcomes such as toe temperature or perfusion index. Temperature and PI have been used in the sympathetic-block literature primarily as physiological indicators of sympathetic modulation.^3,4 Accordingly, the present findings provide evidence of a short-term physiological response, but designating the specific temperature and PI changes as clinically meaningful would require a clinically justified threshold or evidence linking these changes to outcomes relevant to PAD. The authors themselves appropriately identify wound healing, limb salvage, amputation-free survival, and quality of life as important endpoints for future studies.¹

These considerations do not detract from the value of this pilot study. Rather, they may help define the question that subsequent investigations should address: whether the short-term physiological response observed after LSRA translates into clinically relevant benefit in a clearly defined population of patients with limited revascularization options. Clarification of revascularization status, concomitant postoperative therapy, and the basis for interpreting physiological effect sizes as clinically meaningful would further strengthen the clinical interpretation of these preliminary findings.

Disclosure

The author reports no conflicts of interest in this communication.