Presentation on theme: "Ivan Casserly MD Denver VA Medical Center"— Presentation transcript:
1 The Ankle Brachial Index Measurement, Calculation, and Interpretation Limitations Ivan Casserly MDDenver VA Medical CenterUniversity of Colorado Hospital
2 Ankle Brachial Index Ankle brachial index (ABI) Ankle brachial pressure index (ABPI)Ankle arm index (AAI)
3 Ankle Brachial Index Why should we care? In clinical practiceAids in diagnosis and assessment of patients with symptoms suggestive of PADRole in primary prevention since PAD is a powerful independent predictor of CV morbidity and mortality regardless of symptomatic status of PAD.
4 Ankle Brachial Index How good is it at diagnosing PAD? Using gold standard of DSA angiography>50% stenosis in lower extremity vessel
5 Ankle Brachial Index Diagnosis of PAD Niazi et al, Cath Cardiovasc Interv 2006;68:
6 Ankle Brachial Index Role in Primary Prevention – Low incidence of classic claudication PADAsymptomaticAtypical SymptomsClaudicationSubstrate for CLI of underlying PAD.Only 1-3% of all patients with PAD progress to CLIClinical pathway to CLI is variable - Prior to presentation with CLI, most patients will have been asymptomatic – perhaps related to sedentary existence, only a minority with prior claudication.Some present with tissue loss (especially diabetics), others progress through rest pain and subsequent tissue loss.StablePADRest PainTissue LossCLI
7 Peripheral Arterial Disease Prevalence PARTNERS Program (PAD Awareness, Risk, and Treatment: New Resources for Survival)350 Primary care sitesPatients (n=~7,000)>70 yrs50-69 yrs with history DM or smokingPVD diagnosisABI <0.9Previous documentationAbnormal vasc studiesPrior revascularizationHirsch AT, JAMA 2001;286:
9 Peripheral Arterial Disease Under-diagnosis in Primary Care Practice / Influence of assoc. diagnosis of CVD10%7%6%6%Hirsch AT, JAMA 2001;286:
10 Peripheral Arterial Disease Impact of Diagnosis on Survival Normal SubjectsAsymptomatic PADSymptomatic PADSevere Symptomatic PADSurvivalYear1.00121086420.000.250.500.75severe symptomatic PAD had the worst prognosis: analysis of this group revealed a 15-fold increase in rates of mortality due to cardiovascular disease and CHD.The study cited above categorized patients (n=565) into four groups: normals (n=318) and those with PAD (n=67). Evaluated were those with asymptomatic PAD (by Rose questionnaire) , those with symptomatic PAD (symptomatic and either abnormal ABI or diminished doppler flow velocities, not both) characterized by claudication, and those with PAD that was both symptomatic and severe (symptoms by Rose, and severity by both abnormal ABI and diminished doppler flow velocities).The graph shows the survival curves for the three groups of patients compared with the normal subjects. Patients with severe symptomatic PAD had by far the worst prognosis of the three groups of patients; only one in four was still alive at the end of the 10-year follow-up period.METHODS. We examined 565 men and women (average age, 66 years) for the presence of large-vessel peripheral arterial disease by means of two noninvasive techniques--measurement of segmental blood pressure and determination of flow velocity by Doppler ultrasound. We identified 67 subjects with the disease (11.9 percent), whom we followed prospectively for 10 years. RESULTS. Twenty-one of the 34 men (61.8 percent) and 11 of the 33 women (33.3 percent) with large-vessel peripheral arterial disease died during follow-up, as compared with 31 of the 183 men (16.9 percent) and 26 of the 225 women (11.6 percent) without evidence of peripheral arterial disease. After multivariate adjustment for age, sex, and other risk factors for cardiovascular disease, the relative risk of dying among subjects with large-vessel peripheral arterial disease as compared with those with no evidence of such disease was 3.1 (95 percent confidence interval, 1.9 to 4.9) for deaths from all causes, 5.9 (95 percent confidence interval, 3.0 to 11.4) for all deaths from cardiovascular disease, and 6.6 (95 percent confidence interval, 2.9 to 14.9) for deaths from coronary heart disease. The relative risk of death from causes other than cardiovascular disease was not significantly increased among the subjects with large-vessel peripheral arterial disease. After the exclusion of subjects who had a history of cardiovascular disease at base line, the relative risks among those with large-vessel peripheral arterial disease remained significantly elevated. Additional analyses revealed a 15-fold increase in rates of mortality due to cardiovascular disease and coronary heart disease among subjects with large-vessel peripheral arterial disease that was both severe and symptomatic. CONCLUSIONS. Patients with large-vessel peripheral arterial disease have a high risk of death from cardiovascular causes.Adapted from Criqui MH, et al. N Engl J Med. 1992;326:Criqui MH, Langer RD, Fronek A, et al. Mortality over a period of 10 years in patients with peripheral arterial disease. N Engl J Med. 1992;326:
11 Peripheral Arterial Disease Impact of Diagnosis on Survival Data from the Strong Heart Study, n= Strong heart study Circ 2004;109: Only 25 patients with ABI<0.6Background—The associations of low (0.90) and high (1.40) ankle brachial index (ABI) with risk of all-cause andcardiovascular disease (CVD) mortality have not been examined in a population-based setting.Methods and Results—We examined all-cause and CVD mortality in relation to low and high ABI in 4393 AmericanIndians in the Strong Heart Study. Participants had bilateral ABI measurements at baseline and were followed up foryears ( person-years). Cox regression was used to quantify mortality rates among participants with highand low ABI relative to those with normal ABI (0.90 ABI 1.40). Death from all causes occurred in 1022 participants(23.3%; 27.9 deaths per 1000 person-years), and of these, 272 (26.6%; 7.4 deaths per 1000 person-years) wereattributable to CVD. Low ABI was present in 216 participants (4.9%), and high ABI occurred in 404 (9.2%). Diabetes,albuminuria, and hypertension occurred with greater frequency among persons with low (60.2%, 44.4%, and 50.1%) andhigh (67.8%, 49.9%, and 45.1%) ABI compared with those with normal ABI (44.4%, 26.9%, and 36.5%), respectively(P0.0001). Adjusted risk estimates for all-cause mortality were 1.69 (1.34 to 2.14) for low and 1.77 (1.48 to 2.13) forhigh ABI, and estimates for CVD mortality were 2.52 (1.74 to 3.64) for low and 2.09 (1.49 to 2.94) for high ABI.Conclusions—The association between high ABI and mortality was similar to that of low ABI and mortality, highlightinga U-shaped association between this noninvasive measure of peripheral arterial disease and mortality risk. Our datasuggest that the upper limit of normal ABI should not exceed (Circulation. 2004;109: )Resnick et al. Circulation 2004;109;
12 Peripheral Arterial Disease Impact of Diagnosis on Survival – Polyvascular Disease Hospitalization events: Transient ischemic attack, unstable angina, or worsening of PAD.Adjusted for sex and age.Adapted from PG Steg et al. JAMA.2007;297:
13 ABI and Primary Prevention Algorithm Doobay AV et al. Arterioscler Thromb Vasc Biol.2005;25:
16 Ankle Brachial Index Performance Hiatt WR, N Engl J Med 2001;344:
17 Ankle Brachial Index Performance CLINICAL DEMONSTRATION
18 Ankle Brachial Index Performance - Review Patient PositionNo activity for 4-5 minutesSupine position
19 Ankle Brachial Index Performance – Arm Pressure Appropriate cuff sizeDoppler over brachial arteryNOT STETHESCOPE (underestimate SBP)NOT OVER RADIAL ARTERYRecord right AND left arm brachial pressuresWhy?
20 Ankle Brachial Index Performance – Ankle Pressure CuffAppropriate sizeAppropriate locationLower leg above malleoliNOT OVER BULK OF CALF MUSCLESDoppler over DP AND PTNOT STETHESCOPE
21 Ankle Brachial Index Calculation ABINumerator – Ankle pressuresHigher of the two pedal pressuresBrachialDenominator – Brachial pressureHigher of the two arm pressuresBest reflects aortic pressure
22 Ankle Brachial Index Calculation - Rationale PatientDP 100, PT 150, Highest brachial 150Method 1.Higher of the two pressuresABI 150/150 = 1Sensitivity ↓Specificity ↑Method 2.Lower of the two pressuresABO 100/150 = 0.66Sensitivity ↑Specificity ↓
23 Ankle Brachial Index High versus Low Ankle Pressure (HAP vs LAP) Niazi et al, Cath Cardiovasc Interv 2006;68:
24 Ankle Brachial Index Interpretation What is a normal ABI?
25 Ankle Brachial Index Interpretation Normal ankle pressure is 8-15% higher than arm pressureEpidemiological studies have used ABI of 0.9 as cutoff of normal from abnormal for diagnosis of PAD.
26 Ankle Brachial Index Interpretation – High ABI – Non-compressible vessels
27 Ankle Brachial Index Interpretation Hirsch AT et al, J Am Coll Cardiol 2006;47:
28 Study17 volunteers1st year n=102nd year n=43rd year n=3
29 Feedback from Study Part A – Performance of ABI Measure ABI for right leg on patient
37 Ankle Brachial Index Limitations Localization of diseaseNon-compressible ABIPseudo-normal ABIResting versus exercise ABIRole in diagnosis of critical limb ischemia (CLI)Hypertensive patient
38 ABI and Localization of Disease Segmental Limb Pressures BrachialUpper ThighUpper CalfAnkleToeAorto-Iliac, CFA, Prox SFAMid/distal SFA and PoplitealTibialSmall Vessel Disease
39 ABI and Localization of Disease Pulse Volume Recordings Measures volume change in limb with each pulsationVolume of tissue and venous blood relatively constantChange in volume due to arterial inflowCuffs inflated to ~60mmHgVolume change presented on spectral displaySimilar to arterial pulse wave tracingStenosis indicated by loss of amplitude during systole
41 Non-Compressible ABIs Role of Toe Pressure Great toe 32mHg2nd toe 35mmHg3rd toe 17mmHg4th toe 19mmHg5th toe absentValue of toe pressure in patients with non-compressible tibial vessels and supranormal ABI -Normal toe-brachial index > 0.7
42 Non-invasive Hemodynamic Evaluation Toe Pressure
44 Resting versus Exercise ABI Exercise Testing ABI at baseline2 mph at 12% grade, 5 minutesABI post-exercise, 1 minute, then q 2 minutesPost-exercise ankle systolic pressureFalls >20% from baselineTakes longer than 3 minutes to recover
45 Resting versus Exercise ABI Exercise Testing Resting ABIExercise ABIN=396 symptomatic patients with PAD.
46 Resting versus Exercise ABI Exercise Testing 58 year old maleRight buttock claudicationClassic description
48 ABI in Patients with Critical Limb Ischemia Limitation Delete n=49ABIDelete
49 ABI in Patients with Critical Limb Ischemia Importance of Indication for Assessment Hemodynamic findings are usually confirmatory – However exceptions exist as illustrated in this case.Ankle Pressure 140mmHgABIToe Pressure 92mmHgRight Heel
50 Popliteal and Tibial Angiography ATPTPeronealATEmphasizing the point that anatomic definition is sometimes required to confirm the diagnosis.PTPeroneal
51 ConclusionsABIHelpful in diagnosis and assessment of patients with symptomatic PADUseful in primary prevention of CV morbidity and mortality, especially in asymptomatic patients or patients with atypical symptoms.Requires training in order to perform correctly and calculate ABIHas limitations that should be understood