Advanced Technology

CT Angiography -- Fact or Fiction?

Remember the science fiction movies where the doctor of the future answered all questions about his patients with a fancy scan that showed exactly what the problem was? The usual refrain heard from this Doc-of-the-Future for any diagnostic dilemma was "Put them in the scanner!" Is this farfetched and foolishly futuristic? Maybe not.

One of the major limitations in preventative cardiology is that by the time someone has angina or fails a stress test, the disease is rather severe and has been present for decades before it becomes clinically evident by symptoms, an abnormal stress test, or sudden death. Historically, cardiologists have measured coronary obstructions as the standard for determining the presence and severity of coronary artery disease. In order to have a physiologically significant obstruction to coronary blood flow, however, it takes approximately a 70% stenosis. The vast majority of clinical events occur, however, as the result of a plaque rupture, in which a lipid-rich, unstable plaque of less that 50% suddenly ruptures and occludes blood flow! This helps explain why sudden cardiac death is the presenting initial symptom in one-half of men approximately two-thirds of women in the United States today. Coronary artery disease is, by far, the leading cause of death in the US, killing over a million Americans every year.

Enter Computerized Tomographic Angiography (CTA). Available since approximately 2005, CTA is a technology that offers an incredible new way of visualizing the heart and vascular structures that is revolutionizing how we detect and treat atherosclerosis and heart disease. With the development of 64-slice spiral (or helical) CTA, we are now able see cardiac and vascular structures that previously could only be seen in the operating room or on the autopsy table. This "virtual autopsy" takes about ten minutes on the CT scanner table and a ten second breath hold and yields incredibly detailed, high resolution (400 micron), two-, three-, and four-dimensional images of any vascular structure in the body - from the Circle of Willis to the interdigital vessels of the toes and everything in between. Although the technique is relatively straightforward, it is possible due to the revolution in CT imaging hardware as well as computer hardware and software including fast, real-time, three-dimensional computer graphics. In fact, the capability to do this imaging is largely due to the legions of computer gamers that made the silicon powering this technology cheap enough for the "niche" application of CTA!

Since the introduction of office-based 64-slice CTA technology in my practice in Dallas, Texas in 2005, I have been able to replace essentially all of my former invasive angiography with CTA. My cardiac catheterization volume fell by 84% in one year after the introduction of CTA into my practice � the only patients going directly to the cath lab were those who presented in the Emergency Department with Acute Coronary Syndromes and ST-segment elevation MIs. Just this change in my practice during the first year saved approximately 2.8 million dollars by replacing invasive cardiac catheterizations. I was able to do non-invasive angiography safer, faster, more accurately, and cheaper with CTA. Because of this I now offer CTA as the first line test to detect the presence and severity of coronary artery disease, rather than using the relatively inaccurate (and expensive) stress testing.

In addition to obtaining information about coronary disease, structural heart disease, and cardiac and vascular anomalies, I also can also obtain physiological information from the scan. It shows cardiac systolic- and end-diastolic volumes, left ventricular ejection fraction, left ventricular wall thicknesses, cardiac output, and stroke volumes. I can also evaluate other causes of chest pain and chest pathology from the same scan by detecting the presence of aortic dissections, pulmonary emboli, pericardial disease, lung disease, and even hiatial hernias. As an example, I now diagnose approximately one new, occult, very early lung cancer a month in patients who are having a Cardiac CTA scan.

Beyond the assessment of coronary artery disease, we can also determine the true plaque "burden" present, as CTA allows me to see plaque that is outside the lumen (unlike invasive angiography, which shows only the luminal constriction caused by plaque in the intima and media). Because of this, this technique shares the accuracy of research techniques, such as coronary intravascular ultrasound (IVUS). Unlike IVUS, however, cardiac CTA is non-invasive, safer, simpler, and dramatically less expensive. Cardiac CTA also allows me to go beyond assessing the presence or absence of plaque in a highly sensitive way, it also allows the ability to characterize plaque � hard, soft, lipid-rich, calcium-rich, stable, unstable, etc. These characteristics are extremely valuable in determining an individual�s risk of an acute event and provide information that can be useful to make therapeutic decisions about cholesterol lowering medications.

With the advent of fast, highly accurate, safe, and relatively inexpensive Cardiac CTA, I think we are on the verge of identifying individuals at risk, years before they need stents, bypass surgery, or have sudden cardiac death as the initial symptoms of coronary artery a disease. Not only can we identify (and treat) plaque years before it causes trouble, the images provided to my patients are dramatically successful in convincing them to make life-style changes, quit smoking and take their medications. In the future, I predict that in addition to ones colonoscopy at age fifty, the average American will get their Cardiac CTA "Heartogram™"!

Today we have the technology that has already begun to dramatically change cardiology and the rate of change and adoption of this technology will only increase in the near future. Already in 2007, just like in those science fiction movies, when I need to understand what is going on with my cardiac patients, now I say "Put them in the scanner!"