Coronary Artery Anomalies Workup

Updated: Dec 30, 2019
  • Author: Louis I Bezold, MD; Chief Editor: Stuart Berger, MD  more...
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Workup

Laboratory Studies

In the initial evaluation of a critically ill infant, include an assessment of acid-base status and rule out systemic sepsis. Cardiac enzymes (creatine kinase [CK], lactate dehydrogenase [LDH], serum glutamic-oxaloacetic transaminase [SGOT], troponins) are elevated in association with muscle loss. Brain natriuretic peptide (BNP) may be obtained as an index of congestive heart failure (CHF).

In a typical patient with myocardial muscle damage, SGOT levels elevate within 6 hours of injury, peak at 2-10 times normal at 18-36 hours, and normalize within 3-4 days. In typical patients, LDH levels increase relatively late, peak in 3-6 days, and normalize within 8-14 days. The plasma CK levels exceed normal within 4-6 hours, peak within 24 hours, and decline to normal within 3-4 days.

In addition to the heart, skeletal muscle, smooth muscle, and the brain are endowed with CK, and diagnostic specificity is enhanced by reporting of isoenzymes. Isoenzymes of CK are dimers composed of muscle (M) or brain (B) subunits. MB isoenzyme fraction is only minimally present in tissues other than the heart; consequently, an elevation in CK-MB fraction represents myocardial cell death and is unlikely to be present with ischemia alone.

Because of their high specificity for both myocardial cell injury and infarction, cardiac troponins may allow for detection of minor cell damage and quantification of myocardial cell injury. Troponins are three distinct proteins (I, C, T) that regulate calcium-dependent interaction of myosin and actin. Troponin C is similar in myocardial and skeletal muscle; however, troponins I and T are unique to myocardium, and a sensitive enzyme-linked immunosorbent assay is currently available for clinical use.

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Imaging Studies

Chest radiography

Radiographic features of anomalous coronary arteries are similar to those of CHF, including cardiomegaly, pulmonary venous congestion, interstitial edema, and left atrial enlargement.

Echocardiography

In patients sustaining myocardial injury, echocardiography demonstrates a hypocontractile, dilated, poorly functioning ventricle. Global or regional areas of myocardial dysfunction may be present. Mitral valve insufficiency from papillary muscle dysfunction is often demonstrable and may be recoverable.

Coronary arteries should be diligently sought in any patient presenting with cardiac dysfunction or in an older child presenting with activity-related chest pain. By routine evaluation of coronary arteries, chances for identification of coronary variants are increased.

Specific echocardiographic findings may include identification of the site of coronary artery origin with anomalous origin off pulmonary vasculature, which is associated with reciprocal dilatation and increased flow of corresponding coronary artery as it arises from the aorta. Septal collateral vessels often present as increased color flow signals within the interventricular septum. Transesophageal studies employing color Doppler assessment have been useful in identifying turbulent high-velocity flow in patients with coronary ostial stenosis.

Routine, systematic echocardiographic evaluation of coronary artery origins in a large cohort of asymptomatic patients suggests that clinically "silent" congenital coronary anomalies are more common than generally recognized, particularly high coronary takeoff, wrong sinus of origin, and small coronary artery fistulas. Associated congenital heart defects were found in 53% of individuals with coronary anomalies. [17] Recent description of a clinically unsuspected anomalous left coronary artery diagnosed via echocardiography in a premature infant underscores the importance of routinely identifying coronary artery origins on routine echocardiograms. [18]

Cardiac Magnetic Resonance Imaging (MRI)

Cardiac MRI allows noninvasive evaluation of cardiac structure, flow, and function (as is seen in the image below).

MRI of anomalous right coronary artery (RCA = blac MRI of anomalous right coronary artery (RCA = black arrow) arising from the left sinus of Valsalva and coursing interatrially between the aorta (AO) and the pulmonary artery (PA). Note the oblique origin and the intramural course within the aortic wall, all factors compromising coronary blood flow.

Newer MRI sequences have improved image quality with better anatomical definition. Cine MRI sequences are useful to show dynamics and flow disturbances. Black-blood imaging enables visualization of the lumen and aortic wall. Three-dimensional reconstruction provides optimal anatomical information.

MRI does not use radiation and enables adequate definition of the origin of the coronary vasculature but is limited by time of acquisition and gating requirements for cardiac study and may suboptimally define the distal course and extent of a coronary anomaly.

Computed tomography (CT) scanning

Robust imaging technologies of electron-beam CT (EBCT) and multidetector row CT (MDCT) using intravenous contrast injection have shown excellent definition of coronary arterial anatomy (as is shown in the image below).

Three-dimensional volume rendering from multidetec Three-dimensional volume rendering from multidetector CT imaging of a large right coronary artery aneurysm (arrow). Subtraction of the myocardium in B shows the fistula draining to the coronary sinus and then into the right atrium. (Reproduced from Manghat NE, Morgan-Hughes GJ, Marshall AJ, Roobottom CA: Multidetector row computed tomography: imaging congenital coronary artery anomalies in adults. Heart 2005 Dec; 91(12): 1515-22).

Following a period of approximately 20 seconds of acquisition, very detailed 3-dimensional reconstruction of the origin and course of the coronary distribution can be obtained. Advantages of EBCT and MDCT include greater spatial resolution, with better distal coronary artery and side-branch visualization than MRI.

CT scanning is useful in coronary artery anomalies associated with congenital heart disease. [19] Recently a new classification system for coronary artery anatomy in patients with d-TGA has been proposed based on CT angiography. [20]

Nuclear imaging

In children, radionuclide studies are used to study regions of myocardium at risk for myocardial ischemia and acute or remote myocardial infarction.

Myocardial perfusion imaging with compounds labeled with thallium-201 or technetium-99m permits evaluation both at rest and with exercise. The radiopharmaceutical is taken up by myocardial cells at a certain rate of extraction. Under basal conditions, 88% of thallium is extracted during the first transit. Decreased accumulation of radionuclide indicates underperfusion relative to other areas of myocardium.

Rubidium-82 positron emission tomography (PET) scanning may have use in assessment of myocardial perfusion in children. [21]

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Other Tests

Electrocardiography (ECG)

ECG demonstrates findings of myocardial ischemia, injury, and/or infarction. Characteristic electrocardiographic patterns are evident in patients with evolving myocardial infarction and may include changes in T waves, ST segments, and QRS complexes. These serial changes are most evident in the distribution of the myocardium involved and may include reciprocal changes in leads facing away from this region.

Particularly evident are patterns of ischemia that cause T-wave inversion resulting from repolarization changes, muscle cell injury that causes ST segment elevation, and areas of infarction manifested as Q or QR alteration in QRS complexes.

ECG may also be a useful test in patients with coronary anomalies associated with congenital heart disease. [22]

Preparticipation ECG screening is becoming increasingly common for athletes; some countries have mandatory requirements across many sporting activities. Guidelines related to preparticipation screening for cardiovascular abnormalities in competitive athletes have been established. [23, 24, 25, 26, 6, 27, 28, 29, 30, 31]

Exercise stress test

During exercise, the coronary blood flow increases 5-fold to 6-fold. Blood supply and oxygen delivery may be adequate at rest but may be unable to meet increased demands during exercise.

Treadmill or pharmacologic stress protocols may be administered, with immediate postexercise and late redistribution studies performed to delineate regions of myocardium at risk.

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Procedures

Cardiac catheterization (as is shown in the image below) may be warranted if noninvasive studies fail to define specific anatomic abnormality.

Selective right coronary arterial injection in an Selective right coronary arterial injection in an 8-month-old female with tetralogy of Fallot malformation. Study demonstrates left anterior descending coronary artery (LAD) arising early from the right coronary artery (RCA) and coursing across the right ventricular outflow tract. Left anterior oblique projection.

Right heart pressures may be elevated as a reflection of left heart compromise. Aortic root angiography may be sufficient to accurately define a specific coronary anomaly, yet selective coronary artery studies may be necessary.

Experience in coronary arteriography is necessary to accurately define and identify significant coronary variations.

Postcatheterization precautions to monitor for include hemorrhage, vascular disruption after balloon dilation, pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm. Complications may include rupture of blood vessel, tachyarrhythmias, bradyarrhythmias, and vascular occlusion. These invasive studies carry a significant risk in critically ill infants, and often the experience of an angiographer who specializes in adults may be helpful.

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