Perspectives in Circulation Today
Peripheral Vascular Tests and Long Term Prognosis of Claudication and Critical Leg Ischemia
Beauty is in the Eyes of the Beholder
Factors Affecting Results of Peripheral Vascular Studies and Their Long Terms Comparisons
in Patients with Peripheral Vascular Disease
| Systemic Cardiovascular Factors | |
 | Cardiac output |
| Blood and plasma volumes |
| Blood viscosity |
| Changes in pulse pressure with changes in heart rate |
| Sepsis |
| Pain and anxiety |
| Desired response to cardiovascular medications |
| Adverse response to medications/antibiotics |
| Delirium tremens |
| Extremity Factors | |
| Allowed body position |
| Length of rest period after exercise |
| Venous pressure, scarring and thrombi |
| Lymphatic scarring, lymphedema, edema |
| Peripheral arteriosclerosis obliterans |
| Infection (edema & septic arteritis) |
| Sympathetic & cholinergic neuropathy |
| Tremor |
| Benefit of reconstruction vascular procedures |
| Complications of vascular procedures |
| Benefits of endothelial fibrinolytic and vasodilating factors and of neovascularization resulting from boot therapy |
The ABI has found prominence as a reputable screening test for PAD. Values under 0.9 are said to signify disease and values under 0.4-0.5 are said to signify advanced arteriosclerotic disease and a decrease in the potential to heal. (See our Vascular Test Library for references relevant to test results and healing: http://www.circulatorboot.com/literature/vasctest.html). A rise of 0.1 in the ABI or ten mm Hg in the toe pressure have been taken as evidence of benefit of angioplasty procedures (Silvestro et al). One might ask if the reproducibility of these tests is sufficient to make such assumptions. Besides the factors listed above, the administration of vasodilators may cloud the issue. They are not helpful in improving flow to tissues distal to arteriosclerotic lesions (Coffman 1972); normal vasculature may dilate but arteriosclerotic lesions cannot. The alcoholic, for example, may benefit from the anesthesia produced by his/her drink but his red nose is of little benefit while his toes have an increase in pallor. Many of the above factors are so altered during hospitalizations for vascular procedures that it would be surprising if the toe pressures and ABI of the good leg (the non-operative leg) remained stable during the immediate postoperative period. Papankolaoul et al concluded that there is a lack of consistent correlation between the measured arm-ankle BP difference, or arm-ankle index, and the estimated stenotic graft pressure gradient. This finding illustrates the limitation of the AAI as a monitoring test to predict failure of stenotic infrainguinal vein grafts. Weatherley et al studied 119 participants in both the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS) and did repeat ABIs within 1 year, using a common protocol, automated oscillometric blood pressure measurement devices, and technician pool. Their estimated reliability coefficient for the ankle systolic blood pressure (SBP) was 0.68 (95% CI: 0.57, 0.77) and for the brachial SBP was 0.74 (95% CI: 0.62, 0.83). The reliability for the ABI based on single ankle and arm SBPs was 0.61 (95% CI: 0.50, 0.70) and the reliability of the ABI computed as the ratio of the average of two ankle SBPs to two arm SBPs was estimated from simulated data as 0.70. They concluded their results suggested the need for repeated measures of the ABI in clinical practice, preferably within visits and also over time, before diagnosing peripheral artery disease and before making therapeutic decisions. Augustine et al found that 29% of the measurements taken by the untrained doctors were incorrect by an ABI ratio of more than 0.15, as compared to those taken by the vascular technicians. In contrast, the doctors who received one formal training session and feedback from the vascular technician demonstrated that 15% of the measurements of an ABI ratio differed by greater than 0.15. The results of this study suggested that health professionals should undergo formal training before performing ABI measurements to increase their reliability. Blood pressure determinations at the toes may be more helpful than those at the ankle especially in diabetics, but proper cuff size is important: Påhlsson HI et al found that the toe blood pressure values were 18 mmHg higher (p < 0.01) if measured with a 2.0-cm compared to a 2.5-cm wide cuff. There was a relationship (r = 0.63, p < 0.05 for patients) between toe circumference and the toe blood pressure value, where smaller hallluxes gave lower values. de Graaff et all found significant differences in repeatability coefficients between observers for BP (31 mm Hg), ankle pressure (44 mm Hg), ABI (27%), big toe pressure (41 mm Hg), second toe pressure (67 mm Hg) and TCPO2 (30 mm Hg). Arveschoug et al. studied distal blood pressure measurements using the strain gauge technique. They found a mean day-to-day variation of 11 mmHg at ankle level and 10 mmHg at toe level, thereby giving a minimal significant difference between two distal BP determinations of 22 mmHg at ankle and 20 mmHg at toe level. It would appear that small reported differences in vascular tests after any form of treatment may not be significant. The changes reported after invasive procedures and those associated with slow-acting pneumatic boots are to be compared with those obtained by the Circulator Boot (see Dillon 1980 and Gruenes 2005 in our Pneumatic Boot Library).(Since this Newsletter was published both Angiology and Vascular Medicine have had articles examining the ABI. See Holland-Letz et al and Nukimizu et al in our Vascular Test Library.)