Which Cardiac Imaging Modality Will Become The One-Stop Shop?

 

Cardiac computed tomography (CT)magnetic resonance imaging (MRI)echocardiography and nuclear myocardial perfusion imaging each offer advantages and disadvantages, and frequently at least two of these tests are required to get the full picture of a patient’s cardiac health.  However, in this age of cutting healthcare costs, declining reimbursements and improving efficiency, it would be advantageous to have a single gold standard exam. Technology advances are now making that possibility. 

MRI is ideal because it uses zero radiation, offers higher contrast and clarity than CT, can image without contrast and performs perfusion exams. But, its limitation remains its expense, ferrous metal and implantable device safety issues and the complexity of its operation. 

Nuclear imaging is limited because it fails to provide detailed anatomical information and uses ionizing radiation. It also is expensive, and short half-life radiotracers limit its hours of operations and on-demand use.

Software advances have improved 3-D echo image quality to the point where it appears like a CT reconstruction. It uses no radiation and offers immediate images of anatomy inside the body. But, echo has a limited ability to image the function of the heart. It also requires highly trained operators to ensure precise positioning of the transducer and interpretation can be subjective. (To read about recent echo advances from the September-October 2012 issue, go to www.dicardiology.com/article/ultrasound-sees-increasing-use-interventional-procedures)

CT has the major disadvantage of high radiation doses compared to other modalities, but technical advances make CT the most likely dominant cardiac imaging technology in the next decade.  The rapid expansion and decreasing cost of computing power has enabled fast iterative reconstruction software for lower dose scans. New detector technology is reducing the amount of electronic noise in lower-dose scans and new ECG gating technology has helped cut dose. Combined, these advances have reduced CT dose by more than 50 percent compared to doses a few years ago. 

CT analysis software now allows visualization and quantification of perfusion in the myocardium with images similar to nuclear studies, but with a highly accurate anatomic image base.  

Taking perfusion imaging a step further, CT software now cleared in Europe and in trials in the United States can quantify the fractional flow reserve (FFR) for all vessel segments in the coronary tree, allowing cardiologists to pinpoint the exact lesion causing ischemia. In the future, this technology may eliminate the need for diagnostic catheter angiography and provide a detailed navigation and treatment plan for interventional cardiologists to cut procedure time and improve patient outcomes.  (To read more about these CT advances in the September-Octover 2012 issue, go to www.dicardiology.com/article/latest-advances-coronary-ct-angiography-software.)

Lastly, CT is already a primary tool in emergency rooms and radiology departments across the country. Its widespread availability, ease of use and elimination of user-dependent variability makes CT a primary candidate. 

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I want to redirect the emphasis to the cath lab

 

Dr. Fornell editorializes on the subject of “Which cardiac imaging modality will become the one stop shop”

Concerning the issue of “the one stop shop.” I have been thinking about this subject for a long time, and those who know me, know that I have strong leanings toward the usefulness of the cardiac catheterization laboratory.

Much has been written recently about the usefulness of noninvasive diagnostic tests, with much less being written about the value of cardiac catheterization and contrast angiography. I would like to redirect the emphasis back to the catheterization laboratory and coronary angiography

In addition to being the reference standard for other imaging techniques, it is the only method that allows performance of cardiac and vascular therapeutic procedures at this moment in time. 

 In my view, coronary angiography is going to be with us for a long time. I suggest that we get as much information as possible from this diagnostic technique.

 A proper diagnostic cardiac catheterization and angiography can yield a great deal of information that is important for the

management of the individual patient. What follows is a long list of that information:

1. Stenosis percent narrowing, location, morphology,

and condition of the distal vessel.

2. Stenosis number in the same vessel.

3. Number of vessels containing stenoses.

4. Thrombolysis in myocardial infarction (TIMI) flow

to assess epicardial blood flow.

5. Provide access for other studies, for example, intracoronary

ultrasound, optical coherence tomography (OCT), coronary flow reserve (CFR), and fractional flow reserve (FFR).

6. Identify minimal irregularities (possible plaques

prone to rupture) sometimes associated with coronary artery spasm.

7. Identify myocardial bridges.

8. Identify collateral blood flow.

9. Identify ectopic coronary arteries.

10. Assess the microcirculation by blush of contrast (TIMI myocardial perfusion grade) and assessment of CFR.

11. Assessment of regional myocardial viability by

assessing collateral blood flow, microcirculation

and TIMI flow, and improved contraction after

nitrate or dopamine infusion and post extra-systolic

potentiation (PESP).

12. Visualize the coronary venous circulation, which

may be important to define the anatomy for potential

biventricular pacing.

13. At the time of cardiac catheterization, fluoroscopy

can be done to assess the presence or absence of

calcium in the coronary circulation.

14. Precise measurements of systolic and diastolic

pressure on the left side of the heart.

15. The physiologic significance of coronary stenoses

can be determined by evaluating coronary FFR.

16. Regional and global ventricular function, particularly

if right anterior oblique (RAO) and left anterior

oblique (LAO) ventriculography is performed (wall

motion can be correlated with proximal coronary

stenoses and distal target vessels, microcirculation,

collateral, and anterograde TIMI flow at baseline and

after nitrate infusion).

17.Provides the operator with the opportunity to perform therapeutic procedures e.g. PCI/stent.

 

No other noninvasive studies that I know of can accomplish

all of what I have just outlined, and the radiation dose is acceptable.

 

- C.Richard Conti M.D. MACC