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Extending Coronary Artery Calcium Scanning with CT Coronary Angiography in the Primary Care Setting

      Introduction

      Recent advances in computed tomography coronary angiography (CTCA) have provided a noninvasive approach for assessing the integrity of coronary artery pathology in patients without signs or symptoms of cardiovascular disease.
      • Narula J
      • Chandrashekar Y
      • Ahmadi A
      • et al.
      SCCT 2021 Expert Consensus Document on Coronary Computed Tomographic Angiography: a report of the Society of Cardiovascular Computed Tomography.
      In addition, the reduced cost and increased availability of this procedure have now made it available to primary care physicians (PCP) throughout the United States. Not yet defined are the indications that should be considered by primary caregivers to utilize this radiologic advance in their practice. This perspective will define these indications and describe the additional benefits (and limitations) of CTCA as an extension of coronary artery calcium scanning from a primary care viewpoint. Our recommendations are consistent with 2021 guidelines from the American Heart Association and the Society of Computed Tomography.
      • Narula J
      • Chandrashekar Y
      • Ahmadi A
      • et al.
      SCCT 2021 Expert Consensus Document on Coronary Computed Tomographic Angiography: a report of the Society of Cardiovascular Computed Tomography.
      ,
      • Gulati M
      • Levy PD
      • Mukherjee D
      • et al.
      2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.
      For many cardiovascular indications, CTCA will replace invasive coronary artery angiography (CAA). CAA has been the “gold standard” for defining the anatomy of the coronary arteries. However, in addition to its invasiveness, radiation exposure, and high cost, the resolution is not sufficient to define plaque characteristics.
      • Topol EJ
      • Nissen SE
      Our preoccupation with coronary luminology: the dissociation between clinical and angiographic findings in ischemic heart disease.
      The principal benefit of CAA has been the ability to perform fractional flow reserve (FFR), which provides important data to determine the potential benefit of inserting a coronary artery stent or performing coronary artery bypass grafting.
      • Miszalski-Jamka T
      • Klimeczek P
      • Banyś R
      • et al.
      The composition and extent of coronary artery plaque detected by multislice computed tomographic angiography provides incremental prognostic value in patients with suspected coronary artery disease.
      However, this assessment is now available with CTCA, as described below. Compared with CAA, which requires arterial access and the hazard of insertion of catheters into the heart coronary arteries, CTCA only requires access to a peripheral vein and the injection of contrast material.
      • Adelrahman KM
      • Chen MY
      • Dey AK
      • et al.
      Coronary computed tomography angiography from clinical uses to emerging technologies: JACC state-of-the-art review.
      If FFR is added to the CTCA, beta-blockade and nitroglycerine are often added to reduce heart rate and increase blood flow.

      Case Study Example Utilizing CTCA

      CH is a 59-year-old former smoker with a strong family history of atherosclerotic cardiovascular disease. She has a low-density lipoprotein cholesterol of 180 mg/dL. The American Heart Association risk calculator demonstrates a 10-year cardiovascular risk of 15%. She has occasional vague chest discomfort. However, her coronary artery calcium scan is 75, placing her at moderate 10-year risk. She would like more definitive information about her heart before deciding on therapy. Concerned that she might have extensive non-calcified plaques in her coronary arteries, a CTCA is ordered (Figure). It demonstrates multiple non-calcified plaques in all 4 coronary arteries and a 70% constriction in her circumflex artery. After discussion with the patient, she is started on aggressive medical therapy to lower her low-density lipoprotein cholesterol.
      • Giannini J
      • Padilla J
      • Eaton RP
      • Gonzales K
      • Schade DS
      Prevention of coronary heart disease: a translational clinical challenge.
      Figure
      FigureA coronary artery calcium (CAC) radiograph on the left and a computed tomography coronary angiography (CTCA) radiograph on the right from the same patient. The CAC scan demonstrates calcium deposition in the wall of the circumflex coronary artery (arrow). The total calcium score for this individual was 75 Agatston units. The CTCA demonstrates an atherosclerotic plaque with 70% arterial obstruction in the same location of the circumflex coronary artery (arrow) after injection of contrast material. Each of these non-invasive procedures has different clinical indications and provides different information and prognostic relevance to an individual patient. Both procedures have been shown to be predictive of future cardiovascular events.
      • Budoff MJ
      • Young R
      • Burke G
      • et al.
      Ten-year association of coronary artery calcium with atherosclerotic cardiovascular disease (ASCVD) events: the multi-ethnic study of atherosclerosis (MESA).
      ,
      • Newby DE
      • Adamson PD
      • Berry C
      • et al.
      Coronary CT angiography and 5-year risk of myocardial infarction.

      CTCA and Coronary Artery Calcium

      Both CTCA and coronary artery calcium scan are similar in that both involve a multi-slice CT scan of the chest with a focus on the coronary arteries. Both provide prognostic value on predicting future coronary events and quantitation of the condition of each coronary artery.
      • Budoff MJ
      • Young R
      • Burke G
      • et al.
      Ten-year association of coronary artery calcium with atherosclerotic cardiovascular disease (ASCVD) events: the multi-ethnic study of atherosclerosis (MESA).
      ,
      • Newby DE
      • Adamson PD
      • Berry C
      • et al.
      Coronary CT angiography and 5-year risk of myocardial infarction.
      The major difference is that CTCA directly visualizes the plaques in the coronary arteries, whereas coronary artery calcium scan measures the calcium in the artery, an indirect assessment of atherosclerotic plaques. The CTCA also has the ability to visualize non-calcified coronary artery plaque. However, the cost of CTCA is higher ($500 to $800) than for coronary artery calcium scan (approximately $100), adds additional radiation exposure, requires more expertise to perform, requires an injection of contrast material (into a peripheral vein), and is done at fewer medical centers in the United States. The Figure
      • Budoff MJ
      • Young R
      • Burke G
      • et al.
      Ten-year association of coronary artery calcium with atherosclerotic cardiovascular disease (ASCVD) events: the multi-ethnic study of atherosclerosis (MESA).
      ,
      • Newby DE
      • Adamson PD
      • Berry C
      • et al.
      Coronary CT angiography and 5-year risk of myocardial infarction.
      provides a visual comparison of the radiographic output of each test.

      When Should a CTCA Be Considered?

      There are several specific indications for ordering a CTCA procedure by the PCP. First, when a patient has vague symptoms of chest pain and a coronary artery calcium procedure does not resolve the issue. Second, when a patient is in a relatively high-risk category with a 0 calcium score and is concerned about future risk. Third, when a patient with a positive cardiac stress test does not want an invasive CAA procedure or can't afford a coronary angiogram. Fourth, when a young patient has vague symptoms and a known condition of hypertrophic cardiomyopathy or family history of anomalous coronary arteries. Fifth, when a middle-aged man presents with a history of non-exertional chest pain, hypertension, and a prominent thoracic aorta on a previous chest x-ray study. Sixth, when a middle-aged male has non-diagnostic chest discomfort and a past history of a coronary artery stent or coronary artery bypass grafting.

      Fractional Flow Reserve

      Recent advancements in cardiology have demonstrated that visualizing atherosclerotic plaques in the coronary arteries is not sufficient to warrant invasive procedures such as stenting of the coronary artery or coronary bypass grafting.
      • Schade DS
      • Gonzales K
      • Eaton RP
      Stop stenting; start reversing atherosclerosis.
      Assessment of blood flow across the atherosclerotic constriction in the coronary artery greatly increases the validity of prediction of risk of serious cardiovascular events and beneficial bypass or stent procedures. This technique was once restricted to coronary angiography. However, FFR can now be done using CTCA.
      • Zhuang B
      • Wang S
      • Zhao S
      • Lu M
      Computed tomography angiography-derived fractional flow reserve (CT-FFR) for the detection of myocardial ischemia with invasive fractional flow reserve as reference: systematic review and meta-analysis.
      Because this calculation using CTCA requires additional computational resources (a 3-dimensional model of the heart needs to be reconstructed), commercial establishments can provide this service by electronically sending the CTCA images to them.
      • Ball C
      • Pontone G
      • Rabbat M
      Fractional flow reserve derived from coronary computed tomography angiography datasets: the next frontier in noninvasive assessment of coronary artery disease.
      CTCA-FFR is now covered by Medicare and Medicaid, as well as many insurance companies.

      Summary

      A CTCA should be considered by every PCP when an appropriate patient needs additional anatomical information concerning his/her heart. Recent advances in radiologic techniques now demonstrate that CTCA can provide similar cardiovascular data to coronary angiography without the hazards and cost of an invasive procedure.
      • Adelrahman KM
      • Chen MY
      • Dey AK
      • et al.
      Coronary computed tomography angiography from clinical uses to emerging technologies: JACC state-of-the-art review.
      It can provide critical information as to when a referral to a cardiologist may be indicated or, alternatively, when aggressive medical therapy is the optimal treatment. It may save the patient hundreds of dollars in medical expenses and reduce potential hazards of an invasive procedure. CTCA is now being routinely performed by radiologists in all major medical centers in the United States, making it available to individuals in most towns and cities. It should no longer be considered the sole purview of specialized medical care.

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