SCREENING FOR CORONARY ARTERY DISEASE:
64 SLICE HELICAL CT NOW OPERATIONAL AT PARKVIEW IMAGING
ACCURATE, NONINVASIVE IMAGING OF THE CORONARY ARTERIES HAS BECOME A REALITY
The prevalence of atherosclerotic coronary artery disease is very high in the united states. One third of Americans die of heart disease (one in four die from cancer). A Cleveland Clinic study on donor hearts utilizing intravascular ultrasound discovered that one in four hearts under the age of 25 years and three of four over the age of 40 had atherosclerotic changes. Sudden death is the first and last sign of coronary artery disease in 150,000 people a year. Greater than 50% of coronary artery disease deaths and myocardial infarctions in the United States occur in patients considered low to intermediate risk. 50% of myocardial infarct patients have normal cholesterol profiles. It is now understood that atherosclerotic plaque begins within the blood vessel wall and expands towards the adventitia before projecting into the blood vessel lumen. Small vulnerable plaques are not seen at cardiac caths. They may only be seen with intravenous ultrasound and 64 slice CT. Soft plaque is believed to be the greatest at risk factor for rupture and vessel occlusion. Soft plaque can be present without predisposing risk factors or vessel stenosis. 64 slice CT is the only noninvasive means of detecting vulnerable plaque in the end organ (arterial wall) responsible for CAD. CT coronary angiography will become a first line imaging study for CAD work-up.
Earlier diagnosis and treatment for coronary artery disease is crucial. There is a critical need for noninvasive screening to detect coronary artery disease.
What are the factors necessary for a relevant screening exam?
- Screening for a serious disease.
- Preclinical phase of the disease should have a high prevalence among
the targeted group.
- Screening should be performed before a critical point in the natural
history of disease.
What are the advantages of CT coronary angiography over conventional angiography?
- Images the arterial wall
- Faster and noninvasive and no potential complications
- 3d data set allows infinite reprojections
- Calcium score
- Cardiac functional analysis including ejection fraction, stroke volume, cardiac output and left ventricular mass
- CT also demonstrates the pericardium, myocardium and the cardiac chambers
- View the mediastinum
- Detect coronary anomalies
- Evaluate cardiac valves
- Pacemakers and defibrillators okay
What are the advantages of 64 slice over 16 slice CT?
- Faster scan time decreases cardiac motion
- Improved spatial, temporal and contrast resolution
- Accommodates wider range of patients (COPD, CHF, fast heart rate)
What are the parameters for a great cardiac exam?
- Temporal resolution - how well can you decrease cardiac motion?
- Spatial resolution (high contrast) – how well can you visualize small structures?
- Low contrast resolution – how well can you differentiate between soft plaque and vessel wall and between iodine (contrast) and calcium?
Eventually CT coronary angiography may precede all caths.
- 90% of all caths are elective
- 70% of all caths are either normal or demonstrate disease that does not require mechanical or surgical intervention
- 64 CT slice ct has a 98% negative predictive value
- There is significant cost savings
Other applications include chest pain triage to rule out aortic disease either aneurysm or dissection and pulmonary emboli. CT is now the gold standard for the diagnosis of pulmonary embolus.
High resolution imaging of the carotid arteries, Circle of Willis, renal artery stenosis and peripheral arteries is now routine.