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  Disease summary:

  
  
  
  
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    Coronary artery disease (CAD) is a multifactorial disorder that results from interplay between genetic and environmental factors.

    
    
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    CAD is the most common cause of death worldwide.

    
    
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    CAD is a progressive disease process that generally begins in childhood and manifests clinically in mid-to-late adulthood. It results from the accumulation of atherosclerotic changes within the walls of coronary arteries. The distribution of lipid and connective tissue, and the degree of inflammation in the atherosclerotic lesions determine whether they are stable or at risk of rupture, and subsequent thrombosis, causing acute coronary syndromes (ACSs).

    
    
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    Hypertension, hypercholesterolemia, smoking, and diabetes are major risk factors for CAD. However, they do not account for up to 15% to 20% of patients with myocardial infarction (MI); such patients often have a family history of CAD, pointing to an integral role of genetics in the development of this disease.

    
    
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    Commonly used CAD risk prediction models such as the Framingham risk score take into account known risk factors such as age, plasma lipid levels, blood pressure, tobacco use, and type 2 diabetes. Newer models such as the Reynolds risk score additionally include family history as an independent risk factor but the exact mechanisms by which risk of CAD is inherited remain unclear.

  
  

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  Hereditary basis:

  
  
  
  
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    Monogenic causes of lipid disorders exist. The more commonly encountered premature CAD is highly heritable and common variation in several genes has been shown to be associated with increased risk.

  
  

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  Environmental factors:

  
  
  
  
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    Age, tobacco, sedentary lifestyle, high-fat or -salt diet, hypertension

  
  

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  Monogenic forms:

  
  
  
  
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    Familial hypercholesterolemia (FH), familial defective apolipoprotein B or ApoB (FDB), autosomal dominant hypercholesterolemia, autosomal recessive hypercholesterolemia (ARH), sitosterolemia, primary hypoalphalipoproteinemia

  
  

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  Genome-wide associations:

  
  
  
  
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    More than a dozen genetic loci related to CAD have been found. Currently, testing for any of them has not been clinically validated for risk prediction or to guide treatment (Table 11-1).

  
  

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  Pharmacogenomics:

  
  
  
  
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    The Food and Drug Administration (FDA) has approved CYP2C19 genotype testing to determine if patients may be poor metabolizers of clopidogrel, an agent commonly used to prevent rethrombosis among CAD patients (Table 11-2). Pharmacogenomic data has demonstrated increased risk of statin-related myopathy based on variation in the SLCO1B1 gene.

  
  

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  Differential diagnosis:

  
  
  
  
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    Thromboangiitis obliterans, Kawasaki disease, pericarditis, myocarditis, coronary artery anomaly, coronary artery vasospasm, cardiomyopathy, esophageal disorders

  
  

The manifestations of CAD are quite broad, ranging from asymptomatic to ACSs and sudden cardiac death. Equally broad and intricate are the diagnostic criteria and clinical characteristics used for risk stratification and choice of treatment. Here we provide a brief overview of the characteristics and testing of patients with stable disease and those with ACS. It must be noted that majority of patients with CAD are asymptomatic and physicians rely on ever improving methods of risk stratification to guide their management. Diagnostic evaluation of suspected CAD begins with a clinical assessment.

Clinical Characteristics

Chronic CAD

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  Dyspnea on exertion; substernal chest pain (angina) from cardiac stressors with radiation to the neck, jaw, shoulders, arm, or abdomen; palpitations, syncope or presyncope, and fatigue

ACSs

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  Angina that is new in onset, progressive, or at rest. Relieved by nitroglycerin or rest.

  
  
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  Vagal symptoms such as diaphoresis and nausea; shortness of breath, dizziness; sense of impending doom.

  
  
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  New S4 on physical examination, mitral regurgitation murmur, paradoxical S2, increased jugular venous pressure (JVP), lung crackles.

Diagnostic Testing for CAD

Screening of Asymptomatic Middle-Aged Individuals

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  Fasting lipid profile: Total cholesterol, high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), and triglyceride levels

  
  
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  Inflammatory markers (high-sensitivity C-reactive protein [hs-CRP])

  
  
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  Ankle-brachial index (ABI)

  
  
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  Blood pressure

Evaluation of Suspected or Chronic CAD

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  Electrocardiogram (ECG) and ECG stress testing

  
  
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  Rest or stress transthoracic echocardiography (TTE)

  
  
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  Nuclear imaging studies (treadmill nuclear stress test, a dipyridamole [Persantine] or adenosine nuclear stress test, and a dobutamine nuclear stress test)

  
  
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  Electron beam computed tomography (CT) scanning

  
  
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  Percutaneous coronary angiography

Evaluation of ACS

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  ECG

  
  
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  Measurement of biomarkers of myocardial necrosis (serum troponin I or T, creatinine kinase myocardial band [CK-MB])

  
  
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  TTE

  
  
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  Nuclear imaging studies

  
  
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  Percutaneous coronary angiography