DIAGNOSIS OF CORONARY ARTERY DISEASE


Note-Per ACC/AHA, selection of diagnostic modality for coronary disease should be based in part on pretest probability based in turn on age, gender, and type of chest pain, the latter grouped into four categories as follows.  Patients with either very low or high pretest probability do not benefit from noninvasive testing:
Differentiating panic disorder from myocardial ischemia
Response to Organic Nitrates as a diagnostic test for myocardial ischemia
Exercise Stress Testing
Pharmacologic-ECG Stress Testing
Stress Echocardiography
Myocardial Perfusion Imaging (nuclear medicine cardiac testing)
Coronary Angiography
Positron Emission Tomography ("PET") of the heart for diagnosis of CAD
Magnetic Resonance Coronary Angiography
Computed Tomography of Coronary Arteries
Computed Tomography Coronary Angiography


Factors which favor a diagnosis of panic disorder over myocardial ischemia:

  • Many different autonomic symptoms
  • Symptoms of major depressive disorder
  • Agoraphobic behavior
  • Response to Organic Nitrates as a diagnostic test for myocardial ischemia

    Exercise-ECG Stress Testing

  • Note that resting ECG may be normal in patients with CAD
  • Patient exercises while 12-lead ECG is obtained; Interpretation is based on symptoms, ECG changes, and BP changes
  • Sensitivity/Specificities (source: 2002 ACC/AHA preoperative evaluation guidelines)-Diagnostic accuracy may be less in women
  • For single vessel CAD: 68%/77%
  • For multivessel CAD: 81%/66%
  • For 3-vessel or left main disease: 86%/53%
  • ST DEPRESSIONS in stress test: upgoing are least ominous, flat are intermediate, and downgoing are most ominous (for future MI)
  • Functional exerise capacity was the MOST POWERFUL predictor of mortality (> evidence of ischemia) results in 2y f/u study of 3400 adults who underwent thallium ETT (JACC 30:641, 1997-JW)
  • Exercise-induced LBBB during ETT was strongly associated with a combined endpointed that included all-cause mortality, CABG, PTCA, nonfatal MI, or documented symptomatic tachyarrhythmia in one prospective trial comparing 70 such pts w/70 matched controls (JAMA 279:153, 1998--abst)
  • Adding right precordial leads (V3R, V4R, and V5R) to standard ETT increases sensitivity with no change in specificity (NEJM 340:340, 1999--JW)
  • Exaggerated BP responses with exercise is ass'd with sig. higher risk of developing HTN in the following years (Circ. 99:1831, 1999--JW)
  • Contraindicated if acute coronary syndrome or aortic dissection is suspected, or patient has severe valvular stenosis, decompensated heart failure, severe COPD, or other conditions precluding exercise; or in left bundle branch block (because obscures signs of ischemia on ECG)
  • Can add imaging modalities to increase sensitivity-See "Myocardial Perfusion Imaging" and "Stress Echocardiography" below.
  •  

    Pharmacologic-ECG Stress Testing

     When the patient cannot exercise, pharmacologic stress can be used:

    Stress Echocardiography

     

    Myocardial Perfusion Imaging (nuclear medicine cardiac testing)


    Coronary Angiography

  • Rarely necessary to make the diagnosis of angina (can do clinically & with EKG) or determine extent of CAD (can do with ETT), but used to identify lesions amenable to revascularization
  • Identifies structural disease (stenosis) but there are likely other factors that determine risk of a coronary event
  • Positron Emission Tomography ("PET") of the heart for diagnosis of CAD

     

    Magnetic Resonance Coronary Angiography

    Computed Tomography of Coronary Arteries

  • aka Coronary electron beam computed tomography (EBCT)
  • Measures calcium deposits in arterial walls, generating a "coronary artery calcium score" (CACS)-Not the same as CT coronary angiography (see below)
  • Techniques are advancing rapidly as of 2012, so results from more than a few years back need to be evaluated with caution.
  • One study looked at 1173 asymptomatic pts who were referred by MD's or by self for coronary EBCT, and followed them for avg. of 19 mos to correlate EBCT findings with clinical outcome (Circulation. 1996;93:1951)
    1. Calcium scores were sig. higher in those who eventually had MI, PTCA, CABG, sudden death, or ischemic stroke
    2. Depending on threshold of calcium score used, was able to predict such events with either:
    3. Sensitivity 89%; neg. pred. value 99.8%, pos. pred. value 5.5%
    4. Sensitivity 50%, neg. pred. value 99.2%, pos. pred. value 14%
  • In another study comparing electron beam CT vs. angiography in 125 pts, EBCT yielded satisfactory imaging in only 75% of arteries; in those arteries that were adequately seen on EBCT, it had 92% sensitivity and 94% specificity for high-grade stenosis (NEJM 339:1964, 1998--JW)
  • In another study, 1,196 pts < 45yo w/o known CAD but with CAD risk factors underwent EBCT; presence of detectable coronary calcifications did not predict coronary events over a mean f/u period of 41mos (Circ. 99:2633, 1999--JW)
  • One study found significant inter-scan variability in CACS in pts undergoing consecutive EBCT studies (Am. J. Roentgenol. 174:803, 2000--JW)
  • Another study found sig. correlation between calcium scores on EBCT and incidence of cardiac death or nonfatal MI over 32mo f/u, BUT only 22% of events occurred in pts with "severely abnormal" calcium scores; thus, majority of events occurred in pts with mild or moderate Ca scores (Circ. 101:850, 2000--JW)
  • In a study comparing 16-slice CT angiography of the coronary arteries with standard coronary angiography in 187 pts with suspected CAD, CT angiography had sensitivity of 89% and specificity of of 65% (for detection of > 50% stenosis on standard angiography) (JAMA 296:403, 2006--JW)
  • In a prospective study in 517 pts with chest symptoms, all of whom underwent both CT of the coronary arteries and stress testing, with coronary angiography if either were abnormal, CT had higher sensitivity and specificity than stress testing, including in each of three baseline-risk subgroups.  For stress testing, NPV was 11%-96% and PPV was 32%-95% (depending on pretest probability category); for CT of the coronaries, NPV was 88%-100% and PPV was 52%-97% (depending on pretest probability category) (Ann. Int. Med. 152:630, 2010-JW)
  • In a prospective cohort study in non-diabetics followed for median 5.8y, adding CACS to traditional risk factors increased accuracy
  • CT for evaluating left main coronary artery patency after stenting
  • In a study in 70 pts s/p left main coronary aftery stenting who underwent multislice CT and coronary angiography, sensitivity of CT for restenosis was 100% but positive predictive value was only 67% (Circ. 114:645, 2006--JW)
  • ACC/AHA 2010 guidelines state that coronary CT is "reasonable" for asymptomatic patients with 10-y Framingham Risk predicted at 10-20% and "may be reasonable" for asymptomatic patients with 10-y risk of 6-10%
  • Computed Tomography Coronary Angiography (Sources include Core Content Review of Family Medicine, 2012)