Toe pressure measurement in the context of digital artery calcification

Background In patients suspected for Peripheral Arterial Disease, and who are at risk for arterial calcification, measurement of the Toe Pressure (TP) is preferred over Ankle Brachial Index, due to an alleged reduced susceptibility for calcification in the digital arteries. Recent studies however have shown that calcification of digital arteries is prevalent in Chronic Limb Threatening Ischemia (CLTI) patients. This study examines the influence of digital artery calcification in suspected CLTI on the measured toe pressure. Methods Single center, retrospective analysis of patients reporting to a multidisciplinary vascular clinic. All patients had bilateral toe pressure measurements, and patients without X rays of the foot were excluded. Cox proportional hazard modelling was performed for 1 year major adverse limb events (MALE) between patients with- and without digital artery calcification. Propensity Score Matching was performed to create comparable groups of patients with- and without digital artery calcification, and included known confounders for the presence of digital artery calcification. Toe pressure was plotted against a calculated probability of 1 year MALE-free survival for both matched groups. Results Four-hundred-ninety-four limbs in 382 patients were included, of which 143 had radiographical signs of digital artery calcifications (28.9%), and 351 (71.1%) had not. Digital artery calcification had a 2.51 Hazard Ratio (95C CI: 1.68-3.73) for MALE-free survival. One-hundred-sixty-five patients were matched. Probability of 1-year MALE-free survival increased with decreasing systolic toe pressure in both calcified and non-calcified digital arteries. Overall, a 20-30 mmHg difference between groups is visualized for each estimate of risk. Conclusion Calcification of the arteries of the first toe is present in 27.2% of patients, which significantly reduces MALE-free survival, with a hazard ratio of 2.5. For an adequate assessment of ischemia risk, when Medial Arterial Calcification (MAC) is present in X-ray imaging of the foot, we advise to subtract 20-30 mmHg of the toe pressure measurement.