scanners. Depending on the extent of the calcium deposits, physicians can determine a patient’s level of atherosclerotic burden - mild, moderate, or severe. Dr. Mahmarian co-authored a recent study published in the Annals of Emergency Medicine, which followed 1,000 patients who had gone to the emergency department with chest pain symptoms but no evidence of a heart attack by standard electrocardiogram or cardiac enzyme criteria. Each patient received calcium scoring followed by stress myocardial perfusion imaging: a test to assess the blood flow to the muscle of the heart. Of the 625 patients who had a calcium score of 0, none had an abnormal perfusion study - and only two experienced a cardiac event in the seven months following their screening. “So if patients come into the ED with chest pain of uncertain cardiac etiology and have a calcium score of 0, we can safely send them home with instructions to follow up with their doctors the next day,” says Dr. Mahmarian. “In this regard, calcium scoring should help prevent unnecessary hospitalisation, which benefits both the hospital and the patients. For patients with scores above 0, we can admit them
to the chest-pain unit, and do a stress myocardial perfusion study the next morning,” Dr. Mahmarian adds. Depending on the results of these follow-up tests, physicians can tailor subsequent patient management decisions which would include intensive lipid-lowering therapy and controlling other cardiac risk factors, such as diabetes and hypertension. While there are no data yet to confirm a link between knowing a patient’s calcium score and preventing future cardiac events, Dr. Mahmarian and his Methodist colleagues are working to change that. “We’re in the middle of developing a trial where we do calcium scoring on people with metabolic syndrome and treat them based on their score - controlling blood pressure and diabetes, lowering LDL cholesterol to the 55–60 mg/dl range, and so on,” he says.
CAROTID ARTERY ULTRASOUND “For many years, our best predictor of cardiovascular risk was the Framingham Questionnaire,” recalls Dr. Vijay Nambi of the Methodist Department of Cardiology. “It asks patients about factors like cholesterol, blood pressure, and smoking
to calculate their risk score. The problem is, up to 70% of people who have heart attacks would be placed in the low or intermediate risk category.” With carotid artery ultrasound, Dr. Nambi and his colleagues have found a far more accurate predictor of cardiovascular risk. This simple, non-invasive test uses ultrasound technology and advanced software to measure the inner walls of the carotid artery in the neck. “We measure the thickness of the artery wall compared to what it should be for the average person in the patient’s age group. We can also measure the artery’s stiffness with software that tracks the movement of the artery wall.” In a study co-authored by Drs. Nambi and Ballantyne published in the Journal of the American College of Cardiology, researchers performed carotid artery ultrasound on more than 13,000 healthy patients and followed them over a 10-year period. Results showed that the ultrasound does indeed provide a more complete snapshot of a patient’s risk. “It’s not a homerun by any means, but it’s definitely an improvement on where we’ve been.” says Dr. Nambi. Another advantage of carotid artery ultrasound is that the patient receives not only a picture of the artery, but also a ‘vascular age’, which represents the age at which the results would be considered normal. “We actually adapted the algorithm for vascular age here at Methodist, and shared the formula with the medical community so anyone can use it” says Marti McCulloch, director of the DeBakey Heart & Vascular Center.
METHODIST VASCULAR LAB: WHERE INNOVATION MEETS EXPERTISE Of course, the accuracy of any imaging test is only as good as the expertise of the staff performing it. “In tests like the ultrasound, the skill of the technician is vital,” notes Dr. Nambi. Recognized as a national leader in the field of cardiovascular imaging, the Vascular Lab at The Methodist Hospital has played a role in numerous major studies. “It offers a combination of the newest technology and a high volume of patients, which makes for highly experienced technicians,” continues Dr. Nambi. “As a result, physicians and patients can be very confident in the results they receive.” ■
AH 150
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