A Novel Index Using Ankle Hemodynamic Parameters to Assess the Severity of Peripheral Arterial Disease: A Pilot Study

Abstract

In peripheral arterial disease (PAD) of the lower extremities, the presence of flow-limiting stenoses can be objectively detected by the ankle-brachial index (ABI). However, the severity of ischemic symptoms is not necessarily associated with the ABI value. Atherosclerotic plaque in lower extremity PAD induces ankle arterial stiffness and reduces ankle vascular resistance, which may decrease ankle blood flow and cause ischemic symptoms. We hypothesized that the ankle hemodynamic index (AHI), defined as the ratio of ankle arterial stiffness to ankle vascular resistance, could be used to assess the blood supply deficiency in a diseased lower limb in patients with PAD. The 85 consecutive patients with PAD who were retrospectively analyzed in this study had Rutherford grade 1 to grade 6 ischemia diagnosed as PAD and significant stenotic lesions (>50% diameter stenosis) of the lower extremity on contrast angiography. The AHI was calculated as the product of the ankle pulse pressure and the ratio of heart rate to ankle mean arterial pressure (ankle pulse pressure × heart rate/ankle mean arterial pressure). The Rutherford grade was significantly correlated with the AHI (r = 0.50, P < 0.001), but not with the ABI (r = 0.07, P = 0.52). Multiple ordinal regression analysis showed that anemia (odds ratio 0.66, P = 0.002) and AHI (odds ratio 1.04, P = 0.02) were independently associated with Rutherford grade. Our study shows that AHI, a novel parameter based on the ABI measurement, is well correlated with ischemic symptoms, and may be a useful means to assess the arterial blood supply of the lower extremities of patients with PAD.

Fig 1. A flow-chart of the concepts of the AHI.

AHI, ankle hemodynamic index.

Fig 2. Correlation between the Rutherford classification and ABI and AHI.

The correlation between Rutherford grade and AHI (r = 0.50, R² = 0.25, P < 0.001) but not between Rutherford grade and ABI (r = 0.07, R² = 0.005, P = 0.52) was significant. ABI, ankle-brachial index; AHI, ankle hemodynamic index.

Fig 3. Correlation between the Rutherford classification and ABI and AHI in patients with a totally occluded iliofemoral artery or diabetes.

In the subset of patients with totally occluded iliofemoral arteries (n = 33) or those with diabetes (n = 54) the correlation between Rutherford grade and AHI (r = 0.39, R² = 0.15, P = 0.02 and r = 0.32, R² = 0.10, P = 0.02, respectively) but not between Rutherford grade and ABI (r = −0.21, R² = 0.04, P = 0.23, r = −0.12, R² = 0.01, P = 0.40) was significant. ABI, ankle-brachial index; AHI, ankle hemodynamic index.