Abstract
Background
Acute limb ischemia (ALI) represents an emergency in which delayed intervention results in significant morbidity, and potentially, death.
Purpose
To assess the role of duplex in differentiating embolic from thrombotic ALI.
Methods and Materials
We prospectively recruited 57 patients; with 62 non-traumatic ALI. We measured the diameter at the occluded site (d O ) and the corresponding contralateral healthy side (d C ). The absolute (∆) and percent change (∆%) between the two diameters were calculated as: (d O –d C ) and [(∆/d C )×100] respectively. According to the reference standard (contrast angiography or surgery), limbs were classified into embolic (E-group:37 limbs) and thrombotic (T-group:25 limbs) groups. Postoperative duplex was done in 34 patients after embolectomy and the absolute (∆ P ) and percent change (∆ P %) between the postoperative (d P ) and preoperative (d O ) diameters at the occlusion were calculated as: (d P –d O ) and [(∆ P /d O )×100] respectively.
Results
The baseline clinical characteristics were similar between both groups. However, in the E-group, (∆%) was 21.96 ± 17.53% vs. -11.03 ± 16.16% in the T-group, (p < 0.001). A cutoff value of > 1.41% for (∆%) had 100% sensitivity and 76% specificity for the diagnosis of embolic vs. thrombotic occlusion with AUC 0.95 (95% CI: 0.901–0.999, p < 0.00 l). Postoperatively (∆ P %) was − 11.8 ± 8.2% with a significant negative correlation found between (∆) and (∆ P ); Spearman′s coefficient (rho) = − 0.912, P < 0.001.
Conclusions
A cut off value of 1.41% as percent dilatation or diminution in the diameter of occluded artery is the most important duplex sign for predicting embolic or thrombotic ALI respectively. Postoperative reduction in the diameter of occluded artery after embolectomy confirms this sign.
1
Introduction
According to the 2007 Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II), acute limb ischemia is defined as: a sudden decrease in limb perfusion that causes a potential threat to limb viability (manifested by ischemic rest pain, ischemic ulcers, and/or gangrene) in patients who present within two weeks of the acute event .
There are diverse etiologies for ALI, with the two most common etiologies being embolus and thrombosis in situ secondary to underlying disease such as atherosclerosis. Differentiation between the two can sometimes be difficult; the latter is far more common in occluded bypass grafts .
The appropriate and early clinical evaluation of acute limb ischemia is crucial to identify the etiology (embolic or thrombotic) of the ischemic limb. Early intervention can lead to limb salvage, whereas delayed recognition can place the patient at high risk of significant morbidity, including limb loss and, potentially, mortality .
Patients in whom urgent or semi-urgent surgical or endovascular revascularization is indicated may undergo catheter angiography unless there is a contraindication, such as profound critical limb ischemia, renal dysfunction, or contrast allergy. Alternative imaging modalities include ultrasound, contrast-enhanced computed tomographic angiography, and magnetic resonance angiography .
Many previous studies proposed that duplex scanning can replace effectively preoperative contrast angiography and to be the sole preoperative imaging in the setting of chronic limb ischemia ; however it has not been properly evaluated in the setting of acute limb ischemia .
2
Material and methods
2.1
Patient selection
Fifty-seven consecutive patients with sixty-two cases of ALI admitted to the vascular surgery emergency room and cardiovascular department of Cairo University were studied prospectively.
Exclusion criteria were patients with past history of peripheral arterial graft or arteriovenous fistula, patients with traumatic limb ischemia and patients with non-atherosclerotic peripheral arterial disease (e.g. arteritis and dissection).
2.2
Study design
Eligible patients were subjected to physical examination, electrocardiogram, echocardiography (± transesophageal echocardiography), and duplex scanning. ALI was classified according to the functional classification of the Society of Vascular Surgery/International Society of Cardiovascular Surgery (SVS/ISCVS). Based on the duration of presentation of ischemia, patients were classified into hyperacute (24 h), acute A (1–7 days) and acute B (8–14 days) .
2.2.1
Duplex ultrasound scanning (DUS)
All examinations were performed by two operators, who are experienced DUS operators and who were blinded to the clinical data of the patients. All limbs were scanned from the aorta to the pedal arteries in the lower limb and from the subclavian to the distal ulnar and radial arteries in the upper limb to detect the occluded segment using Advanced Technology Laboratories HDI (high-definition imaging) 5000, Siemens Elegra, and HP Sonos 2000 systems. All had a high-resolution broadband-width linear array transducer (L7 MHz).
The aorta, iliac, femoral and anterior tibial arteries were examined with the patient in the supine position, whereas the popliteal, the peroneal and the posterior tibial arteries were examined with the patient in lateral decubitus position. Arterial segments were identified upon detection of a color signal or, if the artery was occluded, by the identification of a vessel wall accompanied by a vein or two veins in the calf. The following features were used to diagnose occlusion: segmental loss of signal in the insonated vessel, dampened distal signal compared with the proximal signal and proximal exit collaterals as well as distal re-entry collaterals.
Duplex scan was used to assess the state of the arterial wall whether healthy or atherosclerotic. Atherosclerosis was defined by the presence of plaques or intima-media thickness of ≥ 1 mm. The presence of calcification or collaterals was reported. The arterial diameters at the site of occlusion (d O ) and at the corresponding contralateral healthy side (d C ) were measured. The absolute change (Δ) and percent change (Δ%) between the two diameters were calculated as: (d O − d C ) and (Δ/d C ) × 100, respectively.
According to surgical findings and contrast angiography, limbs were classified into embolic (E group = 38 limbs) and thrombotic (T group = 25limbs) groups.
Postoperative duplex study was done in 34 patients after embolectomy and the absolute change (Δ P ) and percent change (Δ P %) between the postoperative (d P ) and preoperative (d O ) diameters at the site of occlusion were calculated as: (d P − d O ) and (ΔP/d O ) × 100, respectively.
In order to assess the interobserver reliability of duplex ultrasound in measuring the dimensions of different peripheral arterial segments (which is a cornerstone in our study), a subset of 20 healthy volunteers with no reported history of peripheral arterial diseases was recruited. Measurements were taken consecutively with only two observers (AMT, DO) for the SFA diameter (just after the CFA bifurcation) and both observers were blinded to the results of each other. Data were given as the average determined from three optimized measurements. Comparison between measurements of the superficial femoral arteries by both operators was done.
Also a subset of 30 healthy volunteers with no reported history of peripheral arterial diseases was recruited to assess the degree of homogeneity between the diameters of the different peripheral arterial segments measured at the same level bilaterally to validate using the segment contralateral to the occlusion and at the same level as a reference segment. The diameter of the superficial femoral artery just after its origin and the popliteal artery at the popliteal crease were measured in both limbs by a single operator (AMT) and then comparison was done between both sides.
2.3
Statistical analysis
The categorical variables were expressed as numbers and percentages, and continuous variables as the mean ± SD. Differences between the 2 groups (embolic and thrombotic occlusion) were calculated using chi-square test for categorical variables and independent sample t-test for continuous parameters. Pearson correlation coefficient (r) and its significance (p) were calculated between (Δ), (Δ%) and the diameter of the contralateral healthy side (d C ). Statistical significance was accepted for all p values ≤ 0.05. In parallel, non-parametric tests were also performed because of wide dispersion of some of the data (Mann–Whitney, Spearman correlation, each when appropriate).
Receiver operating characteristic curve (ROC) analysis was used to determine the optimal cutoff of different duplex measurements for differentiating acute embolic from thrombotic limb occlusion with best sensitivity and specificity.
Multiple stepwise logistic regression was done for detection of the most important independent variables that can detect embolic and thrombotic occlusion.
Interobserver reliability was expressed as intraclass correlation coefficients (ICCs). An ICC < 0.20 is considered as poor agreement, 0.21–0.40 as fair agreement, 0.41–0.60 as moderate agreement, 0.61–0.80 as good agreement and 0.81–1.00 as very good agreement.
2
Material and methods
2.1
Patient selection
Fifty-seven consecutive patients with sixty-two cases of ALI admitted to the vascular surgery emergency room and cardiovascular department of Cairo University were studied prospectively.
Exclusion criteria were patients with past history of peripheral arterial graft or arteriovenous fistula, patients with traumatic limb ischemia and patients with non-atherosclerotic peripheral arterial disease (e.g. arteritis and dissection).
2.2
Study design
Eligible patients were subjected to physical examination, electrocardiogram, echocardiography (± transesophageal echocardiography), and duplex scanning. ALI was classified according to the functional classification of the Society of Vascular Surgery/International Society of Cardiovascular Surgery (SVS/ISCVS). Based on the duration of presentation of ischemia, patients were classified into hyperacute (24 h), acute A (1–7 days) and acute B (8–14 days) .
2.2.1
Duplex ultrasound scanning (DUS)
All examinations were performed by two operators, who are experienced DUS operators and who were blinded to the clinical data of the patients. All limbs were scanned from the aorta to the pedal arteries in the lower limb and from the subclavian to the distal ulnar and radial arteries in the upper limb to detect the occluded segment using Advanced Technology Laboratories HDI (high-definition imaging) 5000, Siemens Elegra, and HP Sonos 2000 systems. All had a high-resolution broadband-width linear array transducer (L7 MHz).
The aorta, iliac, femoral and anterior tibial arteries were examined with the patient in the supine position, whereas the popliteal, the peroneal and the posterior tibial arteries were examined with the patient in lateral decubitus position. Arterial segments were identified upon detection of a color signal or, if the artery was occluded, by the identification of a vessel wall accompanied by a vein or two veins in the calf. The following features were used to diagnose occlusion: segmental loss of signal in the insonated vessel, dampened distal signal compared with the proximal signal and proximal exit collaterals as well as distal re-entry collaterals.
Duplex scan was used to assess the state of the arterial wall whether healthy or atherosclerotic. Atherosclerosis was defined by the presence of plaques or intima-media thickness of ≥ 1 mm. The presence of calcification or collaterals was reported. The arterial diameters at the site of occlusion (d O ) and at the corresponding contralateral healthy side (d C ) were measured. The absolute change (Δ) and percent change (Δ%) between the two diameters were calculated as: (d O − d C ) and (Δ/d C ) × 100, respectively.
According to surgical findings and contrast angiography, limbs were classified into embolic (E group = 38 limbs) and thrombotic (T group = 25limbs) groups.
Postoperative duplex study was done in 34 patients after embolectomy and the absolute change (Δ P ) and percent change (Δ P %) between the postoperative (d P ) and preoperative (d O ) diameters at the site of occlusion were calculated as: (d P − d O ) and (ΔP/d O ) × 100, respectively.
In order to assess the interobserver reliability of duplex ultrasound in measuring the dimensions of different peripheral arterial segments (which is a cornerstone in our study), a subset of 20 healthy volunteers with no reported history of peripheral arterial diseases was recruited. Measurements were taken consecutively with only two observers (AMT, DO) for the SFA diameter (just after the CFA bifurcation) and both observers were blinded to the results of each other. Data were given as the average determined from three optimized measurements. Comparison between measurements of the superficial femoral arteries by both operators was done.
Also a subset of 30 healthy volunteers with no reported history of peripheral arterial diseases was recruited to assess the degree of homogeneity between the diameters of the different peripheral arterial segments measured at the same level bilaterally to validate using the segment contralateral to the occlusion and at the same level as a reference segment. The diameter of the superficial femoral artery just after its origin and the popliteal artery at the popliteal crease were measured in both limbs by a single operator (AMT) and then comparison was done between both sides.
2.3
Statistical analysis
The categorical variables were expressed as numbers and percentages, and continuous variables as the mean ± SD. Differences between the 2 groups (embolic and thrombotic occlusion) were calculated using chi-square test for categorical variables and independent sample t-test for continuous parameters. Pearson correlation coefficient (r) and its significance (p) were calculated between (Δ), (Δ%) and the diameter of the contralateral healthy side (d C ). Statistical significance was accepted for all p values ≤ 0.05. In parallel, non-parametric tests were also performed because of wide dispersion of some of the data (Mann–Whitney, Spearman correlation, each when appropriate).
Receiver operating characteristic curve (ROC) analysis was used to determine the optimal cutoff of different duplex measurements for differentiating acute embolic from thrombotic limb occlusion with best sensitivity and specificity.
Multiple stepwise logistic regression was done for detection of the most important independent variables that can detect embolic and thrombotic occlusion.
Interobserver reliability was expressed as intraclass correlation coefficients (ICCs). An ICC < 0.20 is considered as poor agreement, 0.21–0.40 as fair agreement, 0.41–0.60 as moderate agreement, 0.61–0.80 as good agreement and 0.81–1.00 as very good agreement.
3
Results
3.1
Patient characteristics
This study recruited 57 consecutive patients with 62 occlusions (5 patients had two occlusions at two different sites). Mean age was 53.6 ± 15.8 years with age range between 20 and 85 years, 53.2% occlusions were detected in females while 46.8% occlusions were detected in males. The baseline clinical characteristics of the patients with embolic or thrombotic ALI are shown in ( Table 1 ) with no significant difference was noted between embolic or thrombotic occlusion.
| Variables | E-Group 37 (59.7%) | T-Group 25 (40.3%) | p value |
|---|---|---|---|
| Age (mean ± SD) | 50.9 ± 15.6 | 57.5 ± 15.6 | NS |
| Male gender | 16 (43.2%) | 13 (52%) | NS |
| Diabetes | 8 (21.6%) | 8 (32%) | NS |
| Hypertension | 15 (40.5%) | 8 (32%) | NS |
| Smoking | 10 (27.0%) | 9 (36%) | NS |
| Ischemic heart disease | 8 (21.6%) | 6 (24%) | NS |
| Heart failure | 6 (16.2%) | 4 (16%) | NS |
| Atrial fibrillation | 11 (29.7%) | 5 (20%) | NS |
| Cerebrovascular diseases | 4 (10.8%) | 4 (16%) | NS |
| Time of presentation | |||
| Hyperacute | 9 (24.3%) | 3 (12%) | NS |
| Acute A | 16 (43.2%) | 12 (48%) | NS |
| Acute B | 12 (32.4%) | 10 (40%) | NS |
| Mode of presentation | |||
| Pain | 37 (100%) | 25 (100%) | NS |
| Paresthesia | 20 (54.1%) | 10 (40%) | NS |
| Paralysis | 4 (10.8%) | 4 (16%) | NS |
| Coldness | 26 (70.3%) | 19 (76%) | NS |
| Color changes | 21 (56.8%) | 16 (64%) | NS |
| SVS/ISCVS Classification | |||
| Class I | 11 (29.7%) | 5 (20%) | NS |
| Class IIa | 16 (43.2%) | 11(44%) | NS |
| Class IIb | 9 (24.3%) | 6 (24%) | NS |
| Class III | 1 (2.7%) | 3 (12%) | NS |
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