Author + information
- C. Richard Conti, MD⁎ ()
- ↵⁎University of Florida, Health Science Center, Room M-438, 1600 SW Archer Road, P.O. Box 100277, Gainesville, Florida 32610-0277
I read with interest the paper by Meijboom et al. (1) relating to diagnostic accuracy of 64-slice computed tomographic coronary angiography (CTA) and the editorial comment on the limitations of CTA by Nissen (2).
Bluemke et al. (3), in a scientific statement on noninvasive coronary artery imaging, remind us that CTA gives one no option for immediate intervention, does not serve as the only basis for coronary artery bypass grafting (CABG), has no outcome analyses, has angiographic comparisons with small groups pre-selected to undergo both procedures, and has lower spatial resolution compared to catheter-based coronary angiography (CBCA); in addition, motion and other artifacts may result in false-negative and false-positive results with CTA, and continuous visualization of the coronaries with CTA is not possible at present on patients with atrial fibrillation or frequent ectopy.
Further limitations as outlined by Nissen (2) are as follows: when CTA is used to visualize the coronary arteries, calcification of the coronaries can cause false-negative and false-positive results, stents make visualization of the coronary lumen difficult, and the predominant risk of CTA is radiation exposure. However, I am told by CTA advocates that radiation reduction strategies such as tube modulation or prospectively ECG-triggered acquisitions are on the horizon (4).
I have no doubt that CTA will become a useful, but limited, diagnostic imaging device for coronary artery assessment. However, I would like to point out some of the positive values of CBCA since it has been and remains the standard of reference for coronary noninvasive imaging techniques.
CBCA provides assessment about stenosis percent narrowing, location, morphology, and condition of the distal vessel, stenosis number in the same vessel, number of vessels containing stenoses, Thrombolysis In Myocardial Infarction (TIMI) flow grade, and TIMI myocardial perfusion grade. It also provides access for intracoronary ultrasound, optical coherence tomography (vascular wall evaluation), coronary flow reserve (microcirculation evaluation), and fractional flow reserve (epicardial stenosis evaluation).
CBCA also can detect minimal irregularities (such as plaque prone to rupture). Collateral flow is easily detected with this method as are coronary artery anomalies as well as evaluation of microcirculation by assessment of myocardial blush and collateral blood flow. With the catheters in place, one can obtain information about regional and global ventricular function, valves can be assessed, and pressures measured.
CBCA is useful for the detection of myocardial bridges and coronary artery spasm, physiologic investigation of the coronary circulation, detection of coronary artery dissections, and their therapy. Coronary artery calcium seen at fluoroscopy does not interfere with the detection of coronary stenoses an angiography. Coronary angiography also provides information about regional myocardial viability by the assessment of TIMI flow grade, TIMI myocardial blush grade, and left ventricular regional wall motion on ventriculography.
With catheters in the heart, the coronary venous circulation may also be assessed, either by runoff from the coronary arteries or by direct catheterization of the coronary sinus with retrograde coronary venous perfusion possibly useful in biventricular pace implantation.
I would add to this that oftentimes when pictures of CTA are compared to pictures of CBCA, only a single view and single frame of the catheter-based angiogram is shown. This is not the real world of coronary angiography. No one looks at a single frame, and no one looks in one single projection to assess coronary pathology.
Finally, all things considered, properly done cardiac catheterization with contrast angiography can be a 1-stop shop for diagnostic imaging and therapy of the cardiovascular system, and the radiation dose is acceptable.
- American College of Cardiology Foundation
- Meijboom W.B.,
- Meijs M.F.L.,
- Schuijf J.D.,
- et al.
- Nissen S.E.
- Bluemke D.A.,
- Achenback S.,
- Budoff M.,
- et al.