Published June 2000
Revised Septermber 2001

Probability of Coronary Artery Disease

Medicine is a science of uncertainty and an art of probability
Osler
Coronary Artery Calcification
CT detection

Atherosclerotic heart disease is the number one cause of death. Methods of detecting coronary artery disease prior to fatal events are needed so that appropriate measures can be taken to reduce risk. Anatomic studies have established that coronary calcification is invariably located near areas of advanced atherosclerotic disease. A direct relation between the extent of coronary calcification and the severity of stenotic lesions or frequency of myocardial infarction is consistently observed in autopsy series. The more extensive the calcification, the more frequent and more severe the degree of stenosis. This relationship is recognized in all age groups and both sexes, but is more marked in younger patients.

CT and in particular, electron-beam CT (EBCT) is the most sensitive radiographic method to detect coronary artery calcification. The value of EBCT can be summarized as follows:
Absence of Detectable Coronary Artery Calcification EBCT*
  • Does not absolutely rule out the presence of atherosclerotic plaque, including unstable plaque
  • Highly unlikely in the presence of significant luminal obstructive disease
  • Observation made in the majority of patients who have had both angiographically normal coronary arteries and EBCT scanning
  • Testing is gender independent
  • May be consistent with a low risk of a cardiovascular event in the next 2-5 years
Presence of Detectable Coronary Artery Calcification EBCT*
  • Confirms the presence of coronary atherosclerotic plaque
  • The greater the amount of calcification (i.e., calcium area or calcium score), the greater the likelihood of obstructive disease, but there is no one-to-one relation, and findings may not be site specific
  • Total amount of calcification correlates best with total amount of atherosclerotic plaque, although the true "plaque burden" is underestimated
  • A high calcium score may be consistent with moderate to high risk of a cardiovascular event within the next 2-5 year
Electron Beam CT (EBCT) Protocol
  • Imatron Ultrafast CT
  • No contrast
  • 3 mm slice thickness
  • High resolution volume mode
  • 100 ms scan time
  • EKG gating, triggered at 80% of the RR interval
  • Breath hold
  • Supine position
  • Radiation exposure < 500 mrem
  • Total procedure time 10 min

    • Coronary calcification score (Agatston)

    • Threshold CT density > 130 HU for pixel areas > 1mm2
    • Lesion Score 1 = 130 - 199, 2 = 200 - 299, 3 = 300 - 399, 4 > 400
    • Score each region of interest by multiplying the density score and the area
    • Total coronary calcium score determined by adding up each lesion score for all sequential slices


    Coronary Artery Anatomy
    Quictime Movies
    Normal Cardiac Cine
    Coronary Artery Calcification

    Flash movies
    Normal Cardiac Cine
    Coronary Artery Calcification
    		Left main and anterior descending coronary artery
    Calculate the Probability of Coronary Artery Disease Malpractice
    Select
  • age
  • gender
  • patient presentation
  • coronary artery calcification at CT
    		• Berlin L. Liability of performing CT screening for coronary artery disease and lung cancer. AJR 2002; 179:837-42.
    [Related Records][Full text]
    Clinical Characteristics
    Age:
    Gender:
    Male Female
    Presentation
    Coronary Calcification
     Yes
    		  No
    Prior probability CAD
    Posterior probability CAD
    Prediction of Coronary Heart Disease

    For the prior probability of coronary artery disease, the above model uses age, gender and clinical presentation. Other predictive models could be used for prior probability. Based on data from the Framingham Study, predictive models have been derived from the blood pressure, total cholesterol, LDL cholesterol, and HDL cholesterol, diabetes, smoking, gender and age. To calculate risk based on these models choose one of the following.
    Probability (90% specificity) that 1 coronary artery will have degree of stenosis (from Rumberger et al)
    Angiography % Stenosis
    		 EBCT calcium score
    > 20
    27-88
    > 30
    89-127
    > 40
    128-166
    > 50
    167-370
    > 70
    > 371
    example: score of 150, 90% specificity of stenosis one artery > than 40%
    EBCT Scoring Guidelines (adapted from Rumberger et al.)
    Calcium Score
    Probability of CAD (> 80% stenosis)
    Cardiac Risk Status
    0
    Low < 5%
    Minimal
    1-10
    Low < 10%
    Low
    11-100
    Mild Stenosis
    Moderate
    101-400
    Nonobstructive disease, may have stenosis
    Likely
    > 400
    High likelihood (> 90%) at least one stenosis
    High
    Likelihood ratios
    Likelihood ratios for coronary artery calcification and significant coronary artery disease (>70% stenosis)
    Budoff n=709
    Likelihood Ratio (Calcium present)
    Likelihood Ratio (Calcium absent)
    < 40 age
    2.58 (1.37 - 4.89)
    0.43 (0.22 - 0.86)
    40 - 50
    1.77 (1.38 - 2.27)
    0.30 (0.19 - 0.50)
    > 50
    1.50 (1.35 - 1.67)
    0.01 (0 - 0.07)
    From 6 participating centers, EBCT used in 709 patients (427 with angiographic significant disease). Likelihood ratios (95% confidence interval) calculated from data provided in Table 2.

    Note that in older subjects, the presence of calcium does not raise the likelihood of significant coronary artery disease as much as it does in younger patients. Conversely note that the absence of calcium markedly decreases the likelihood of coronary artery disease in the older patient population.
    Likelihood ratios for coronary artery calcification and significant coronary artery disease (>70% stenosis)
    Detrano
    n=491
    Any Calcium present
    Calcium score > 100
    Likelihood Ratio (Calcium present)
    Likelihood Ratio (Calcium absent)
    Likelihood Ratio (Calcium present)
    Likelihood Ratio (Calcium absent)
    Male
    > 55 years
    1.12 (1 - 1.25)
    0.2 (0.04 - 0.95)
    1.76 (1.32 - 2.35)
    0.27 (0.14 - 0.50)
    < 55
    1.32 (1.13 - 1.55)
    0.26 (0.11 - 0.61)
    1.86 (1.2 - 2.86)
    0.69 (0.53 - 0.89)
    Female
    > 55
    1.42 (1.21 - 1.66)
    0.07 (0.01 - 0.49)
    2.18 (1.54 - 3.09)
    0.36 (0.21 - 0.62)
    < 55
    1.73 (1.34 - 2.22)
    0.15 (0.02 - 0.98)
    4.93 (2.36 - 10.33)
    0.46 (0.24 - 0.85)
    From 5 institutions, EBCT used in 491 symptomatic patients (211 (43%) with angiographic disease). Likelihood ratios (95% confidence interval) calculated from data provided in Table 2. As with Budoff, the absence of calcium does not rule out disease. The presence of calcium is most helpful in the younger subjects
    Prevalence of Coronary Artery Stenosis at Autopsy
    adapted from Diamond and Forrester
    Male
    Female
    Age
    Proportion
    Prevalence %
    Odds
    Proportion
    Prevalence %
    Odds
    30-39
    57/2954
    2
    0.02
    5/1545
    0.3
    0.003
    40-49
    234/4407
    5.5
    0.06
    18/1778
    1
    0.01
    50-59
    488/5011
    9.7
    0.11
    62/1934
    3.2
    0.03
    60-69
    569/4641
    12.3
    0.14
    130/1726
    7.5
    0.08
    Prevalence of Coronary Artery Disease in Symptomatic Patients
    Likelihood ratios in (), adapted from Diamond and Forrester
    Nonanginal Chest Pain
    Atypical Angina
    Typical Angina
    Age
    Men
    Women
    Men
    Women
    Men
    		 Women
    30-39
    5.2 (0.05)
    0.8 (0.008)
    21.8 (0.28)
    4.2 (0.04)
    69.7 (2.3)
    25.8 (0.35)
    40-49
    14.1 (0.16)
    2.8 (0.03)
    46.1 (0.86)
    13.3 (0.15)
    87.3 (6.9)
    55.2 (1.23)
    50-59
    21.5 (0.27)
    8.4 (0.09)
    58.9 (1.43)
    32.4 (0.48)
    92 (11.5)
    79.4 (3.85)
    60-69
    28.1 (0.39)
    18.6 (0.23)
    67.1 (2.0)
    54.4 (1.19)
    54.4 (1.19)
    90.6 (9.64)
    Typical angina: discomfort
  • 1) in the anterior chest, neck, shoulders, jaw, or arms,
  • 2) precipitated by physical exertion or psychic stress,
  • 3) relieved by rest or nitroglycerin within minutes.

    • Atypical angina: 2 of 3 features

    Nonanginal chest pain: < 2 features

    		 The prevalence of disease is higher in men and increases with age. Patients with symptoms, especially typical angina increases the likelihood of malignancy. These relationships may be explored using the calculator.
    The Importance of Bayes

    Reverend Bayes wins case

    After a two-week trial, a Sedgwick County, Kansas, jury returned a verdict in favor of the surviving spouse and two children of a 37-year-old assembly line worker. The jury found the defendant physician at fault for damages of $750,000. There is a big difference between a doctor who goes through the motions of collecting facts and ordering tests, and one who truly understands the significance of those facts and the implications of the test results. The plaintiff experienced classic angina. At the Emergency Room MI was excluded leaving angina (myocardial ischemia) at the top of the differential diagnosis. The defendant-internist admitted the patient for further evaluation. A stress test was performed and was negative. On the basis of a normal stress test, the physician explained that nothing in the test indicated ischemia. Whatever caused the chest pain was not related to the heart. Seven days the plaintiff collapsed and died at work. At autopsy, all three major coronary arteries evidenced significant obstruction. At trial, the defendant's position, which had support in the literature, was that the hospital evaluation was appropriate and complete, and a negative treadmill test after 12 minutes of exercise justified discharging the patient back to normal activity. Plaintiffs' position was that, while the defendant went through all of the proper motions, collected most of the important information, and did an acceptable test, he had a fundamental and dangerous lack of understanding the information from the test. The defendant did not understand the principle of Bayes Theorem. Bayes Theorem is part of the medical standard of care. The physician who understands the limitations of the treadmill stress test and the principles of Bayesian analysis is never justified in reassuring a patient that typical angina is not caused by coronary artery disease. In every case where a diagnosis is missed, justified on the basis of a test result, it is important to find out what the sensitivity and specificity of the test is, and how Bayesian analysis comes into play to determine the posttest likelihood of disease, notwithstanding a negative test result.

    References:

    Schoenhagen P, Halliburton SS, Stillman AE, et al. Noninvasive Imaging of Coronary Arteries: Current and Future Role of Multi-Detector Row CT. Radiology 2004; 232:7-17.
    [Related Records][Full text]

    Schoepf UJ, Becker CR, Ohnesorge BM, Yucel EK. CT of Coronary Artery Disease. Radiology 2004; 232:18-37.
    [Related Records][Full text]

    Greenland P, LaBree L, Azen SP, Doherty TM, Detrano RC. Coronary artery calcium score combined with Framingham score for risk prediction in asymptomatic individuals. Jama 2004; 291:210-215.
    [Related Records]

    Wexler L, Brundage B, Crouse J, et al. Coronary artery calcification: pathophysiology, epidemiology, imaging methods, and clinical implications. A statement for health professionals from the American Heart Association. Writing Group. Circulation 1996; 94:1175-1192.
    [Related Records]

    Diamond GA, Forrester JS. Analysis of probability as an aid in the clinical diagnosis of coronary-artery disease. N Engl J Med 1979; 300:1350-1358.
    [Related Records]

    Black WC, Armstrong P. Communicating the significance of radiologic test results: the likelihood ratio. AJR 1986; 147:1313-1318.
    [Related Records]

    Stanford W, Thompson BH, Weiss RM. Coronary artery calcification: clinical significance and current methods of detection. AJR 1993; 161:1139-1146.
    [Related Records]

    Agatston AS, Janowitz WR, Hildner FJ, et al. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol 1990; 15:827-832.
    [Related Records]

    Budoff MJ, Georgiou D, Brody A, et al. Ultrafast computed tomography as a diagnostic modality in the detection of coronary artery disease: a multicenter study. Circulation 1996; 93:898-904.
    [Related Records]

    Rifkin RD, Parisi AF, Folland E. Coronary calcification in the diagnosis of coronary artery disease. Am J Cardiol 1979; 44:141-147.
    [Related Records]

    Detrano R, Hsiai T, Wang S, et al. Prognostic value of coronary calcification and angiographic stenoses in patients undergoing coronary angiography. J Am Coll Cardiol 1996; 27:285-290.
    [Related Records]

    Rumberger JA, Brundage BH, Rader DJ, Kondos G. Electron beam computed tomographic coronary calcium scanning: a review and guidelines for use in asymptomatic persons. Mayo Clin Proc 1999; 74:243-252.
    [Related Records]

    Disclaimer:

    Information provided is not intended to be medical or technical advice. The information given at this site is for educational purposes only and is not sufficient for medical decisions. I disclaim any liability for the acts of any physicians or any other individual who receives any information on any medical procedure through this web site. I accept no legal responsibility for any injury and/or damage to persons or property from any of the suggestions or material discussed herein.