Abstract
Background
The resting ankle-brachial index (ABI) is widely used to diagnose lower extremity artery disease (LEAD). However, some LEAD patients have a normal ABI yet require percutaneous transluminal angioplasty (PTA).
Methods
This was a retrospective study of consecutive LEAD patients who underwent PTA. The patients were classified into two groups based on the ABI of the limb that underwent PTA: the ABI-normal group (ABI 0.91-1.40), and ABI-abnormal group (ABI ≤ 0.90 or > 1.40). The primary endpoints were major adverse cardiovascular and cerebral events (MACCEs) and major adverse limb events (MALEs).
Results
Of the 334 patients (mean age: 70 ± 12 years, 60% male), 69 (21%) had a normal ABI, and 265 (79%) had an abnormal ABI. After a median follow-up of 1.5 (0.6-3.1) years, 84 (25%) patients reached the primary or secondary endpoints. The ABI-normal group had a higher proportion of males (73% vs. 57%, p = 0.02) and a higher prevalence of chronic kidney disease (78% vs. 56%, p < 0.01). Angiography revealed less severe lesions in the femoropopliteal artery (p < 0.01) and a lower rate of stent deployment (15% vs. 31%, p < 0.01) in the ABI-normal group than in the ABI-abnormal group. However, the incidence rates of MACCEs (29% vs. 24%, p = 0.56) and MALEs (23% vs. 28%, p = 0.63) were comparable in the two groups.
Conclusions
LEAD patients with a normal ABI often have less severe above-the-knee artery lesions but similar poor outcomes, highlighting the need for additional hemodynamic assessments and increased clinical attention.
Keywords: Ankle-brachial index, Lower extremity artery disease, Major adverse cardiovascular and cerebral events, Major adverse limb events, Percutaneous transluminal angioplasty
Abbreviations
ABI, Ankle-brachial index
ATA, Anterior tibial artery
ATK, Above-the-knee
BTK, Below-the-knee
CIA, Common iliac artery
CLTI, Critical limb-threatening ischemia
FP, Femoropopliteal
GLASS, Global Limb Anatomic Staging System
IP, Infra-popliteal
LEAD, Lower extremity artery disease
MACCEs, Major adverse cardiovascular and cerebral events
MALEs, Major adverse limb events
PeroA, Peroneal artery
PoTA, Posterior tibial artery
PTA, Percutaneous transluminal angioplasty
INTRODUCTION
Lower extremity artery disease (LEAD) is the third leading cause of death among individuals with atherosclerotic cardiovascular diseases, following coronary artery disease and stroke.1 Clinically, LEAD can manifest as intermittent claudication, critical limb-threatening ischemia (CLTI), or non-joint-related limb symptoms, but it can also present asymptomatically.2 LEAD is frequently associated with other comorbidities such as diabetes mellitus,3-6 hypertension,3-6 and chronic kidney disease.7,8 The morbidity and mortality of LEAD in such patients are equal to or exceed those of coronary artery disease.4,9
The resting ankle-brachial index (ABI) is calculated as the ratio of ankle blood pressure to upper arm blood pressure, and it is a simple and convenient diagnostic tool for detecting LEAD, with high sensitivity and specificity.10 An abnormal ABI (≤ 0.9) typically indicates LEAD, but exceptions exist. In patients with borderline (0.91-0.99) or normal (1.00-1.40) ABIs who have typical LEAD manifestations, additional diagnostic tests such as the toe-brachial index with waveforms, transcutaneous oxygen pressure, or skin perfusion pressure can facilitate the diagnosis of CTLI.1,11 However, these tools are often not available in many hospitals, leading to potential misdiagnosis or delayed diagnosis of patients with a borderline or normal ABI who require revascularization. It is unclear whether LEAD patients presenting with a normal ABI differ from those with an abnormal ABI, and defining these characteristics may help identify this vulnerable subset of LEAD patients. Furthermore, while a lower ABI is associated with an increased risk of myocardial infarction, stroke, and all-cause and cardiovascular mortality,12 the risk and clinical outcomes of symptomatic patients with a borderline or normal ABI who require revascularization remain poorly understood. Characterizing the clinical outcomes of these patients can help optimize their treatment.
This study aimed to explore the characteristics and clinical outcomes of LEAD patients with borderline or normal ABI values. Through a retrospective analysis of LEAD patients requiring revascularization, we compared the clinical characteristics, angiographic findings, and outcomes of individuals with a borderline or normal ABI to those with an abnormal value. The primary endpoints were the incidence of major adverse cardiovascular cerebral events (MACCEs) and major adverse limb events (MALEs).
METHODS
Study design
This was a retrospective study of consecutive patients with symptomatic LEAD who underwent percutaneous transluminal angioplasty (PTA) at National Cheng Kung University Hospital between November 01, 2010 and May 31, 2021. This study adhered to the Declaration of Helsinki and was approved by the Human Research and Ethics Committee of National Cheng Kung University Hospital (IRB number: A-ER-111-317). The requirement for informed consent was waived due to the retrospective study design.
Study population
All patients who underwent PTA for claudication or CLTI at our hospital were eligible for inclusion. Patients lacking ABI data within one year before PTA and those who underwent PTA before ABI measurement were excluded. Based on the ABI of the limb that underwent PTA, the patients were categorized into two groups: the ABI-normal group (ABI: 0.91-1.40), and the ABI-abnormal group (ABI ≤ 0.90 or > 1.40).
Clinical information including age, sex, comorbidities, Rutherford classification before PTA, and medications, was obtained through a thorough review of electronic medical records. In addition, the use of devices such as stents, drug-coated balloons, and catheter-directed thrombolysis during PTA was recorded.
Angiographic characteristics
Angiographic characteristics were reviewed and recorded by two specialists (Y.C. and S.W.). Using the Global Limb Anatomic Staging System (GLASS) outlined in the Global Vascular Guidelines,13 femoropopliteal (FP) and infra-popliteal (IP) grades were assigned on a scale from 0 to 4 to delineate the severity of lesions in each vessel. Above-the-knee (ATK) lesions, including in the common iliac artery (CIA), were graded according to the FP disease grade. Below-the-knee (BTK) lesions, including in the anterior tibial artery (ATA), posterior tibial artery (PoTA), and peroneal artery (PeroA), were graded according to the IP disease grade. These grades ranged from 0 (mild or no significant disease) to 4 (most severe obstruction) (Supplemental Table 1).
Clinical outcomes
Medical records of the enrolled patients were reviewed for clinical outcomes, with follow-up until May 31, 2022. The primary endpoint was the incidence of MACCEs, including cardiovascular death, myocardial infarction, coronary revascularization, or stroke. The co-primary endpoint was the incidence of MALEs, including major amputation, repeat endovascular or surgical revascularization, or other limb-related hospitalizations. The secondary endpoints were all-cause mortality and minor amputation. Outcome assessment was initially based on hospital codes, followed by a chart review for confirmation.
Statistical analysis
Statistical analysis was performed using SPSS version 21.0 (IBM, Armonk, NY, USA). Continuous variables are expressed as mean ± standard deviation or median (interquartile range), depending on the distribution, while categorical variables are presented as frequency (percentage). Between-group differences in normally distributed continuous variables were assessed for statistical significance using the Student’s t-test, while the Mann-Whitney U test was used for non-normally distributed continuous variables. The chi-square test or Fisher’s exact test was used for analyzing categorical variables. Univariate logistic regression analysis was conducted to identify factors associated with normal ABI. Variables associated with a p value < 0.1 in the univariate analysis were included in multivariable logistic regression analysis. Event-free survival rates were calculated using the Kaplan-Meier method, and between-group differences were evaluated using the log-rank test. A p value < 0.05 was considered statistically significant.
RESULTS
Study population
Of the 798 patients who underwent PTA during the study period, 426 (53%) had missing ABI data and 38 did not have ABI data within one year before PTA and were therefore excluded (Figure 1). The remaining 334 patients (median age: 71 [62-79] years; 60% male) were included in this retrospective analysis. Of these patients, 37 (11%) had a normal ABI in both legs, and 32 (10%) had a normal ABI in the limb that underwent PTA but an abnormal ABI in the contralateral limb. Consequently, a total of 69 patients (21%) were classified into the ABI-normal group, and the remaining 265 patients (79%) were classified into the ABI-abnormal group (Figure 1).
Figure 1.
Flow diagram of the study cohort. ABI, ankle-brachial index; PAD, peripheral artery disease; PTA, percutaneous transluminal angioplasty.
The ABI-normal group had a significantly higher proportion of males (73% vs. 57%, p = 0.02), and a higher prevalence of coronary artery disease (58% vs. 42%, p = 0.02) and chronic kidney disease (78% vs. 56%, p < 0.01) than the ABI-abnormal group. Both groups were comparable in terms of comorbidities and Rutherford classification (Table 1). Notably, 47 patients (68%) in the ABI-normal group had tissue loss and 17 (25%) patients reported resting pain, indicating a need for angioplasty. Multivariate analysis revealed that chronic kidney disease and male sex were the only factors associated with the ABI-normal group (Supplemental Table 2).
Table 1. Baseline characteristics of ABI-normal and ABI-abnormal groups.
| All (n = 334) | ABI-normal (n = 69) | ABI-abnormal (n = 265) | p value | |
| Age, years | 70 (62-79) | 70 (63-77) | 70 (62-80) | 0.63 |
| Male sex | 201 (60%) | 50 (73%) | 151 (57%) | 0.02 |
| Hypertension | 230 (69%) | 49 (71%) | 181 (68%) | 0.67 |
| Diabetes mellitus | 249 (75%) | 55 (80%) | 194 (73%) | 0.27 |
| Dyslipidemia | 108 (32%) | 27 (32%) | 81 (31%) | 0.18 |
| Coronary artery disease | 152 (46%) | 40 (58%) | 112 (42%) | 0.02 |
| Old stroke | 52 (16%) | 9 (13%) | 43 (16%) | 0.52 |
| Chronic kidney disease | 201 (60%) | 54 (78%) | 147 (56%) | < 0.01 |
| End-stage renal disease | 150 (45%) | 45 (65%) | 105 (40%) | < 0.01 |
| Atrial fibrillation | 47 (14%) | 9 (13%) | 38 (14%) | 0.78 |
| Heart failure | 62 (19%) | 15 (22%) | 47 (18%) | 0.45 |
| Cancer | 19 (6%) | 2 (3%) | 17 (6%) | 0.38 |
| ABI, left leg | 0.7 (0.5-0.9) | 1.0 (0.9-1.2) | 0.6 (0.5-0.8) | < 0.01 |
| ABI, right leg | 0.7 (0.6-0.9) | 1.0 (0.9-1.1) | 0.7 (0.5-0.8) | < 0.01 |
| Rutherford classification | 0.43 | |||
| < 4 | 48 (14%) | 5 (7%) | 43 (16%) | |
| 4 | 87 (26%) | 17 (25%) | 70 (26%) | |
| 5 | 173 (52%) | 41 (59%) | 132 (50%) | |
| 6 | 23 (7%) | 6 (9%) | 17 (6%) | |
| Aspirin | 213 (64%) | 37 (54%) | 176 (66%) | 0.049 |
| Clopidogrel | 195 (58%) | 33 (48%) | 162 (61%) | 0.046 |
| Cilostazol | 214 (64%) | 43 (62%) | 171 (65%) | 0.73 |
| Statin | 115 (34%) | 23 (33%) | 92 (35%) | 0.83 |
| RAASi | 84 (25%) | 13 (19%) | 71 (27%) | 0.18 |
| Stent | 92 (28%) | 10 (15%) | 82 (31%) | < 0.01 |
| Drug-coated balloon | 26 (8%) | 4 (6%) | 22 (8%) | 0.62 |
| CDT | 3 (1%) | 0 (0%) | 3 (1%) | 1 |
Data presented as median (IQR) or n (%). Medications and stents were recorded post-angioplasty. Between-group differences were assessed using the Mann-Whitney U test for continuous variables. For categorical variables, a chi-square test or Fisher’s exact test was used.
ABI, ankle-brachial index; CDT, catheter-directed thrombolysis; RAASi, renin-angiotensin-aldosterone system inhibitor.
Angiographic characteristics
A normal ABI indicates healthier ATK arterial condition in the ipsilateral limb. Compared to the ABI-abnormal group, the ABI-normal group had a significantly lower GLASS score for the FP artery (p < 0.01), but similar GLASS score for the IP artery (Table 2). This indicated that the primary distinction between the two groups was in the severity of FP artery involvement. Regarding severity in each vessel, the ABI-normal group had significantly lower severity in the CIA and PeroA (p < 0.01), but higher severity in the ATA (p = 0.02). This suggested that occlusive vessels in the ABI-normal group occurred predominantly BTK, especially in the ATA and PoTA (Table 2). Furthermore, the ABI-normal group had lower rates of stent deployment (15% vs. 31%, p < 0.01) and antiplatelet use compared to the ABI-abnormal group (Table 1).
Table 2. Comparison of angiographic findings between the ABI-normal and ABI-abnormal groups.
| ABI-normal (n = 69) | ABI-abnormal (n = 265) | p value | |
| CIA | 0.01 | ||
| 0 | 12 (17%) | 38 (14%) | |
| 1 | 10 (15%) | 53 (20%) | |
| 2 | 4 (6%) | 46 (17%) | |
| 3 | 0 (0%) | 14 (5%) | |
| 4 | 3 (4%) | 4 (2%) | |
| N/A | 40 (58%) | 110 (42%) | |
| GLASS-FP | < 0.01 | ||
| 0 | 7 (10%) | 2 (1%) | |
| 1 | 16 (23%) | 21 (8%) | |
| 2 | 17 (25%) | 39 (15%) | |
| 3 | 24 (35%) | 107 (40%) | |
| 4 | 5 (7%) | 83 (31%) | |
| N/A | 0 (0%) | 13 (5%) | |
| GLASS-IP | 0.10 | ||
| 1 | 3 (4%) | 3 (1%) | |
| 2 | 4 (6%) | 11 (4%) | |
| 3 | 9 (13%) | 30 (11%) | |
| 4 | 47 (68%) | 168 (63%) | |
| N/A | 6 (9%) | 53 (20%) | |
| ATA | 0.02 | ||
| 0 | 2 (3%) | 0 (0%) | |
| 1 | 7 (10%) | 18 (7%) | |
| 2 | 12 (17%) | 39 (15%) | |
| 3 | 11 (16%) | 50 (19%) | |
| 4 | 31 (45%) | 105 (40%) | |
| PoTA | 0.05 | ||
| 0 | 0 (0%) | 0 (0%) | |
| 1 | 10 (15%) | 21 (8%) | |
| 2 | 9 (13%) | 41 (16%) | |
| 3 | 19 (28%) | 47 (18%) | |
| 4 | 25 (36%) | 103 (39%) | |
| PeroA | < 0.01 | ||
| 0 | 2 (3%) | 0 (0%) | |
| 1 | 8 (12%) | 13 (5%) | |
| 2 | 19 (28%) | 61 (23%) | |
| 3 | 21 (30%) | 64 (24%) | |
| 4 | 13 (19%) | 74 (28%) |
Data presented as n (%). # The 0-4 scores for GLASS-FP and GLASS-IP are based on the GLASS evaluation. These grades range from 0 (mild or no significant disease) to 4 (most severe obstruction). N/A indicates the absence of angiographic data.
ATA, anterior tibial artery; CIA, common iliac artery; FP, femoropopliteal; GLASS, Global Limb Anatomic Staging System; IP, infra-popliteal; PeroA, peroneal artery; PoTA, posterior tibial artery.
Clinical outcomes
Over a median follow-up period of 1.5 (0.6-3.1) years, primary composite events occurred in 84 patients (25%). While the incidence rates of MACCEs, coronary revascularization, and stroke did not differ significantly between the ABI-normal and ABI-abnormal groups, the ABI-normal group had a significantly higher incidence of cardiovascular death (10% vs. 2%, p < 0.01, chi-square test) and myocardial infarction (10% vs. 4%, p = 0.05, chi-square test) compared to the ABI-abnormal group (Table 3). Kaplan-Meier survival analysis revealed no significant difference in MACCE-free survival between the ABI-normal and ABI-abnormal groups (29% vs. 24%, p = 0.56, log-rank test, Figure 2A). Furthermore, 89 (27%) patients developed MALEs, and 29 (9%) underwent minor amputation. There were no significant between-group differences in the incidence of MALEs, major amputation, repeat revascularization, or limb hospitalization. However, the ABI-normal group had a higher all-cause mortality rate (42% vs. 22%, p < 0.01) and minor amputation rate (15% vs. 7%, p = 0.05) compared to the ABI-abnormal group (Table 3). Moreover, Kaplan-Meier analysis revealed no significant difference in MALE-free survival between the ABI-normal and ABI-abnormal groups (23% vs. 28%, p = 0.63, log-rank test, Figure 2B).
Table 3. Comparison of clinical outcomes between ABI-normal and ABI-abnormal groups.
| ABI-normal (n = 69) | ABI-abnormal (n = 265) | p value | |
| MACCE | 20 (29%) | 64 (24%) | 0.37 |
| Cardiovascular death | 7 (10%) | 4 (2%) | < 0.01 |
| Myocardial infarction | 7 (10%) | 11 (4%) | 0.05 |
| Coronary revascularization | 18 (26%) | 56 (21%) | 0.38 |
| Stroke | 0 (0%) | 10 (3%) | N/A |
| MALE | 16 (23%) | 73 (28%) | 0.47 |
| Major amputation | 4 (6%) | 19 (7%) | 1.00 |
| Repeat angioplasty | 9 (13%) | 45 (17%) | 0.43 |
| Limb hospitalization | 3 (4%) | 10 (4%) | 0.74 |
| All-cause mortality | 29 (42%) | 57 (22%) | < 0.01 |
| Minor amputation | 10 (15%) | 19 (7%) | 0.05 |
Data presented as n (%).
ABI, ankle-brachial index; MACCE, major adverse cardiovascular and cerebral events; MALE, major adverse limb events.
Figure 2.
Kaplan-Meier curves for (A) cumulative survival free of major adverse cardiovascular and cerebral events (MACCE) and (B) cumulative survival free of major adverse limb events (MALE) in patients with normal or abnormal ankle-brachial indices (ABIs). MACCE was defined as a composite endpoint consisting of cardiovascular death, myocardial infarction, coronary revascularization, or ischemic stroke; MALE was defined as a composite endpoint consisting of major amputation, repeat revascularization, surgical revascularization, or limb-related hospitalization.
DISCUSSION
This study investigated the characteristics and clinical outcomes of LEAD patients presenting with false-negative ABI results. The findings revealed that among the patients requiring angioplasty, those with false-negative ABI results in the target leg were more likely to be male and have chronic kidney disease compared to those with abnormal ABI results, despite a similar prevalence of other comorbidities. Notably, vessel occlusion in the patients with false-negative ABI results predominantly occurred BTK, especially in the ATA and PoTA. Notably, the incidence rates of MALEs and MACCEs were similar between the patients with false-negative ABI results and those with abnormal ABI results.
Previous studies have consistently demonstrated that the ABI has high sensitivity (> 90%) and specificity (95%) for diagnosing lower extremity arterial stenosis with a 50% stenosis threshold.3,14-17 In the present study, 11% of all enrolled patients had a normal bilateral ABI, consistent with previous reports.18 In a large cohort of patients with CLTI who underwent interventions, approximately 24% of those with compressible arteries had a normal ABI.19 Consistent with this finding, 21% of the patients in the present study were classified into the ABI-normal group. Moreover, 93% of the patients in the normal ABI group had tissue loss or resting pain, suggesting that PTA should be considered and would not constitute overtreatment. While the sensitivity of the ABI has been demonstrated in the general population, lower sensitivity has been reported in diabetic patients (53%-70%)12,20,21 and patients with symptoms of LEAD (69%-79%).11,22 In addition, patients with distal lesions have also been reported to be at a higher risk of false-negative ABI results (odds ratio: 3.41).23 This indicates that although ABI is a valuable diagnostic tool, the possibility of false-negative results should be considered, especially in referral centers or patients with specific comorbidities. This highlights the importance of performing additional clinical guideline-recommended examinations11 beyond crucial wound assessment.24 These include assessments of the toe-brachial index with waveforms, transcutaneous oxygen pressure, and skin perfusion pressure to evaluate LEAD in patients with suspicious symptoms and a borderline or normal ABI. In facilities lacking these tools, vascular duplex ultrasound offers a dynamic, non-invasive, radiation- and contrast-free alternative. Importantly, a normal ABI value does not rule out LEAD.
The finding that significantly more male patients required PTA for LEAD aligns with the higher incidence of LEAD in men.25 A previous study also reported that CLTI patients with a normal ABI were more likely to be male.19 Our data also revealed high incidence rates of diabetes mellitus, hypertension, and chronic kidney disease among LEAD patients undergoing PTA, consistent with established atherosclerosis risk factors. Interestingly, women may be more prone to FP disease, whereas patients with diabetes and kidney disease may be more predisposed to IP disease.13 We found a higher proportion of male patients and those with chronic kidney disease in the ABI-normal group. This may explain why some LEAD patients with these comorbidities present with normal ABI values despite having more severe IP lesions. These findings suggest that further investigations are warranted in these patients, particularly in males and those with chronic kidney disease, even when the ABI is normal.
Our results also revealed that the patients with a normal ABI had less severe lesions in the FP artery or CIA but similar or even more severe arterial obstruction in the IP vessels, especially the ATA and PoTA. Previous studies have noted differences in treatment at anatomical levels, however these differences were often subtle (e.g., FP: 49.5% vs. 47.1%).19 In contrast, we used the GLASS-FP score, which showed more substantial differences between the ABI-normal and ABI-abnormal groups (GLASS-FP score < 3: 58% vs. 24%; score = 4: 7% vs. 31%), offering greater clinical relevance. Therefore, in addition to the commonly discussed medial artery calcification causing incompressibility,26 false-negative ABI values may be attributed to less severe ATK obstruction, allowing sufficient calf perfusion. However, stenosis in BTK vessels may still lead to inadequate perfusion of the plantar territory. Maintaining long-term patency with current IP PTA strategies remains a challenge. New devices such as everolimus-eluting resorbable scaffolds27 may help address this issue. This could be one of the reasons for the sub-optimal prognosis in the patients with false-negative ABI results. Another potential contributing factor is calcification, for which several scoring systems have already been proposed.28-30 Incorporating a calcification score in future studies may provide a more comprehensive explanation for the observed discrepancies.
In the COMPASS and VOYAGER PAD trials,31,32 the rates of major amputation, myocardial infarction, stroke, and total amputation were 3.1-3.5%, 4.0-4.5%, 2.0-2.5%, and 19.5%, respectively. In comparison, the rates of major amputation (6-7%), myocardial infarction (5%), and stroke (0-3%) were higher in the present study. The higher incidence of clinical events in our study may be attributed to the extended follow-up period or distinct baseline characteristics of our patient population. We found that the patients with a normal ABI who underwent PTA did not have better outcomes compared to those with an abnormal ABI. Indeed, having a normal ABI may even have increased the risk of minor amputation and all-cause mortality. The exact reasons for these poor outcomes are unclear, but could be due to underlying factors including chronic kidney disease and undetected severe microvascular damage. First, these patients may experience delayed diagnosis and treatment. Second, the current PTA strategies for microvascular disease are less effective than those for larger vessels. This may contribute to disease progression and increase the risk of mortality and adverse events, despite less severe macrovascular lesions. Therefore, for LEAD patients, and particularly those with CLTI, standard treatment should not be delayed based on a normal ABI value. Instead, a comprehensive approach is recommended, including multispecialty care, revascularization, minimization of tissue loss, wound management,33 and adherence to guideline-directed management and therapy,11 particularly medical treatments that can reduce MACEs.
Some limitations of this study should be considered. First, the small sample size of the ABI-normal group may have reduced the statistical power to detect meaningful between-group differences. A larger sample size may have revealed more differences. Second, the retrospective study design introduces limitations and potentially overlooked confounding factors, such as medication adherence, dual antiplatelet therapy, wound management, and timing of PTA and ABI. In addition, wound assessment24 data were incomplete, and defining surgical success was challenging due to variability in physician and patient factors. Third, the proportion of patients with ABI data was lower than expected, possibly due to incomplete recording of ABI reports from other hospitals in our electric medical records. In addition, some physicians may have prioritized computed tomography over ABI testing. Fourth, we did not investigate the role of calcification in false-negative ABI results, which may require further investigation. Fifth, not all vessels were examined using angiography, and comprehensive hemodynamic assessments such as toe pressure or skin perfusion pressure were not performed.
CONCLUSIONS
In conclusion, a normal ABI may only indicate sufficient blood flow in ATK vessels rather than adequate perfusion of the planter region. This highlights the potential for false-negative ABI results, particularly in patients with distal lesions or other comorbidities. Therefore, for patients with a high suspicion of LEAD, a normal ABI result should not delay further examinations. Moreover, we found that the patients with normal ABI values who underwent angioplasty had similar or higher incidence rates of MACCEs and MALEs, including mortality and MI, compared to those with abnormal ABI values. This underscores the need for increased clinical attention and vigilance in managing these patients to improve their prognosis.
DECLARATION OF CONFLICT OF INTEREST
All the authors declare no conflicts of interest.
SUPPLEMENTARY MATERIALS
Supplemental Table 1. Grading of ATK and BTK lesions.
| ATK: CIA | |
| Grade | Lesion grading criteria |
| 0 | Mild or no significant disease (< 50%). |
| 1 | Lesion length < 1/3 (< 10 cm) of total ATK artery. |
| Focal CTO < 5 cm, but not flush occlusion. | |
| 2 | Lesion length < 1/3 (< 10 cm) of total ATK artery. |
| CTO < 1/3 (< 10 cm), but not flush occlusion. | |
| 3 | Lesion length > 2/3 (> 20 cm) of total ATK artery. |
| Flush occlusion < 20 cm or non-flush CTO 10-20 cm. | |
| 4 | Total ATK artery occlusion > 20 cm. |
| BTK: PeroA/PoTA/ATA | |
| Grade | Lesion grading criteria |
| 0 | Mild or no significant disease. |
| 1 | Focal stenosis < 3 cm in tibial artery. |
| 2 | Lesion length < 1/3 of total tibial artery. |
| Focal CTO (< 3 cm) of tibial artery without ostium involvement. | |
| 3 | Lesion length < 2/3 of total tibial artery. |
| CTO < 1/3 of total tibial artery (without ostium involvement). | |
| 4 | Lesion length > 2/3 of total tibial artery. |
| CTO > 1/3 of total tibial artery. | |
| Any CTO of ostium. |
ATA, anterior tibial artery; ATK, above-the-knee; BTK, below-the-knee; CIA, common iliac artery; PeroA, peroneal artery; PoTA, posterior tibial artery.
Supplemental Table 2. Factors associated with normal ABI.
| Variables | Univariate* | Multivariate# | ||
| Odds ratio (95% CI) | p value | Odds ratio (95% CI) | p value | |
| Chronic kidney disease | 2.89 (1.55-5.38) | < 0.01 | 2.70 (1.43-5.07) | < 0.01 |
| Male sex | 1.98 (1.11-3.55) | 0.02 | 1.91 (1.06-3.47) | 0.03 |
| Coronary artery disease | 1.88 (1.10-3.22) | 0.02 | 1.60 (0.92-2.78) | 0.1 |
* Univariate logistic regression was used to compare normal ABI and abnormal ABI groups. # Adjusted for chronic kidney disease, male sex, and coronary artery disease.
ABI, ankle-brachial index; CI, confidence interval.
Acknowledgments
We are grateful to Prof. Sheng-Hsiang Lin and Ms. Chih-Hui Hsu for providing the statistical consulting services from the Biostatistics Consulting Center, Clinical Medicine Research Center, National Cheng Kung University Hospital. This work was supported by a grant from the National Cheng Kung University Hospital (NCKUH-11205001).
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