CT calcium

Question 1

three scoring methods

Answer 1

There are three most commonly used scoring techniques: the original Agatston score, mass scoring and volume scoring.

Question 2

what use is of the coronary Ca scoring method?

example of scores

Answer 2

numerous studies have shown that formal quantification of the extent of CAC is reliably associated with the overall coronary plaque burden and, to a lesser extent, the probability of significant coronary artery stenosis. Further, increasing CAC over serial scans has been closely associated with progression of coronary artery disease.

. CAC is now established as a reliable estimator of the risk of myocardial infarction, coronary death, and all-cause mortality

0 - No identifiable atherosclerotic plaque. Very low cardio-vascular disease risk. A ‘negative’ examination. Greater than 97% chance for absence of coronary artery disease.

> 400 - Extensive plaque burden. High likelihood of at least one ‘significant’ coronary stenosis.

very predictive of CV events in diabetics

Question 3

Limitations of coronary Ca scoring:

Answer 3

• Measure of global atheroma burden
  
  • Cannot predict the location of discrete stenoses, only the likelihood of having at least one somewhere
• Although calcium predicts risk in populations, it does not necessarily indicate individual vulnerability
• The majority of data concerning coronary calcium scoring has come from predominantly male, asymptomatic populations

Question 4

unrelated but - what is The MDCT agiography dataset

Answer 4

1. Coronary lumenography and anatomy
2. Cardiac morphology
3. Ventriculography (left)
   All in the same 5-10 second breath-hold study
   *No additional radiation burden

Question 5

observer variation in CT coronary angiography?

Answer 5

• CT coronary angiography highly reproducible across low, intermediate and high likelihood cohorts
• Inter- and Intra-observer agreements in >95% in all cohorts with non-eccentric calcium and mixed plaque morphology most common causes of disagreement1

Question 6

MDCT vs ICA

Answer 6

• Conventional angiography – 0.2mm3 spatial resolution, 20ms temporal resolution
  
  • Able to distinguish between lesions to within 10% at any heart rate
• MDCT coronary angiography – 0.4mm3
  
  • Able only to distinguish lesions within 30-50% (i.e. why studies use > 50% as positive)

With heart rate limitations

Question 7

RELATION BETWEEN Ca AND INFLAMMATION

Answer 7

Though Inflammation may trigger vascular calcification via all the mechanisms listed above, including the stimulation of VSMC osteogenic transdifferentiation, the relation between the two phenomena is dual

Regarding cellular mechanisms, it is well known that VSMCs and macrophages participate in vascular calcification, though they have not been definitely linked to a specific phase/pattern of calcium deposition.

Question 8

RESULTS FROM PROSPECTIVE multicenter international OCNFIRM registry:

Answer 8

The prognostic value of coronary artery calcium (CAC) scoring is well established and has been suggested for use to exclude significant coronary artery disease (CAD) for symptomatic individuals with CAD.

Contrast-enhanced coronary computed tomographic angiography (CCTA) is an alternative modality that enables direct visualization of coronary stenosis severity, extent, and distribution.

In symptomatic patients with suspected CAD, CCTA adds incremental discriminatory power over CAC for discrimination of individuals at risk of death or MI.

Question 9

overall, what is the current opinion of coronary Ca now?

Answer 9

Coronary artery calcium (CAC) scanning is a reliable, noninvasive technique for estimating overall coronary plaque burden and for identifying risk for future cardiac events
.
numerous studies have shown that formal quantification of the extent of CAC is reliably associated with the overall coronary plaque burden and, to a lesser extent, the probability of significant coronary artery stenosis.

Question 10

what assumptions are made in Ca scoring?

Answer 10

First, both the AS and MS methods make assumptions that denser calcifications should be weighted more heavily than less dense calcifications. However, on an individual plaque basis, increased plaque density per se may be protective for CVD by identifying more stable plaque devoid of an active lipid core.
Based on contrast enhanced coronary CT angiography (CCTA) data, a mild degree of calcification characterizes patients with acute coronary events, while diffuse high-attenuation calcific plaques are associated with chronic coronary events

assumption that is made in all three scoring systems is that the location of the plaque within a given coronary artery is not important. 
Proximal plaque is more prone to rupture and undergo thrombotic occlusion with more disastrous outcomes, while distal disease is more frequently associated with multi-vessel disease than single-vessel disease. 
####It may be more clinically relevant to estimate the score specific to a lesion of interest.
### Similarly, whether a particular artery within the coronary tree is involved (eg, the left main) is not accounted for in the total score of all three methods. 

Finally, none of the scoring methods include information about the distribution of coronary calcium, whether it is localized in a single plaque or it is distributed throughout the coronary system. Whether there is focal or diffuse calcification for a given calcium score may have implications for patient outcomes