The use of the CUSUM chart method for surveillance of learning effects and quality of care in endovascular procedures

Introduction: Quality of care and learning effect surveillance are two mandatory responsibilities within a changing therapeutical paradigm. We aimed to evaluate the feasibility and value of CUSUM chart method in assessing performance in consecutive endovascular procedures done by vascular surgeons of a single department on aorto-iliac, femoropopliteal and renal artery occlusive disease.

Material and method: Data were collected in 405 consecutive patients, scheduled for endovascular intervention of aorto-iliac (n = 131, 32.3%), femoropopliteal (n = 142, 35%) and renal artery (n = 132, 32.7%) occlusive disease during a 6-year period. Quality indicators included inability to cross the lesion, peri- and post-procedural complications and significant residual stenosis or occlusion at 1 month. CUSUM curves were generated for each territory globally and according to each quality indicator. The relevance of curve upward inflections was evaluated with Fisher's Exact Test.

Results: Failure to cross the lesion occurred in 6.9% (aorto-iliac), 10.6% (femoropopliteal) and 2.3% (renal) of patients. One-hundredth twenty aorto-iliac, 127 femoropopliteal and 132 renal angioplasties were finally performed. Peri- and post-procedural complications appeared in 14.5% (aorto-iliac), 9.2% (femoropopliteal) and 2.3% (renal), while significant residual stenosis or occlusion was seen in 0.8%, 4.9% and 2.3% of patients, respectively. Aorto-iliac CUSUM curve showed two upward inflections at the beginning and the end of the period, both associated with peri- and post-procedural complications (p = 0.002 and p = 0.0013) and the latter also with failure to cross the lesion (p = 0.009). Femoro-popliteal CUSUM curve moved progressively upward during all the period, initially related to peri- and post-procedural complications (p = 0.038) and later to failure to cross the lesion (p = 0.004). Renal CUSUM curve didn't show any upward inflection during the analysed period.

Conclusion: CUSUM curves are an excellent tool for measuring learning effect and quality of care within a changing paradigm, such it is the case of endovascular interventions. Curve upward inflections can be further interpreted according to the type of "failure" thus helping to evaluate their underlying causes.