New clinical trials showcase versatility of high-tech cardiovascular imaging

Peer-reviewed research published in October offered an eye-opener for anyone who thinks that cardiac imaging is all about measuring coronary artery occlusions. Variety spiced the most notable imaging research of the month. Studies produced fresh insight into the relevance of renal artery calcium, delayed enhancement and the prediction of post-myocardial infarction left ventricular remodeling, initial imaging assessments of acute stroke, coronary flow reserve and diabetes, aortic dissection, and Turner syndrome, as well as, of course, coronary artery imaging.

Arteriosclerosis

Renal artery calcium is independently associated with hypertension

J Am Coll Cardiol 2007;50:1578-1583

A University of California, San Diego study involving more than 1400 subjects has established a relationship among renal artery calcium, high blood pressure, and hypertension. Dr. Matthew A. Allison and colleagues from the department of family and preventive medicine based their findings on multidetector CT evaluations of 1435 consecutive patients at a university-affiliated disease prevention center. Overall, 17% of the subjects showed evidence calcium, with men having a significantly higher prevalence (19%) than women (14.7%). After adjusting for age and gender, researchers found that 41.2% of subjects with a renal artery calcium score greater than 0 were hypertensive, a significantly higher percentage than the 29.5% rate of hypertension for patients with a score of 0.

Left ventricular remodeling

Prediction of left ventricular remodeling and analysis of infarct resorption in patients with reperfused myocardial infarcts by using contrast-enhanced MR imaging

Radiology 2007;245:95-102

Infarct size involving 24% or more of the left ventricle is an important threshold that predicts remodeling among myocardial infarction patients. Dr. Gunnar K. Lund and colleagues in the cardiology and radiology departments of the University Hospital Eppendorf in Hamburg, Germany, came to this conclusion from delayed enhancement and first-pass perfusion MRI measures of infarct size obtained from 55 patients three days after MI and from follow-up scans eight months later. Remodeling was defined as an increase in left ventricular end-diastolic volume index of 20% or more during follow-up scans. Infarct size with delayed enhancement MR was a powerful predictor for remodeling. The risk rose 2.8-fold with each 10% increase in infarct size. The sensitivity, specificity, and accuracy of DE-MRI for predicting remodeling for infarcts involving 24% or more of left ventricular volume were 92%, 93%, and 93%, respectively.

Acute stroke

MRI-based and CT-based thrombolytic therapy in acute stroke within and beyond established time

Stroke 2007;38:2640-2645

Pooled data from five European stroke centers have found that MRI-based thrombolysis is safer and potentially more efficacious than standard CT-based thrombolysis of acute stroke even when the approved three-hour window for the use of clot-busting tPA has closed. Principal investigator Dr. Peter D. Schellinger, a neurologist from the University of Erlangen in Germany, examined 1210 stroke cases, including 714 patients who received noncontrast CT within three hours of stroke symptom onset, 316 evaluated with MRI within three hours, and 180 who received MRI and possible thrombolysis after three hours. The incidences of symptomatic intracranial hemorrhage for the three scenarios were 5.3%, 2.8%, and 4.4%, respectively. The mortality rates were 13.7%, 11.7%, and 13.3%, respectively, and favorable outcomes based on a modified Rankin Scale were observed in 35.4%, 37%, and 40% of the cases, respectively.

Coronary flow reserve

Additional prognostic value of coronary flow reserve in diabetic and nondiabetic patients with negative dipyridamole stress echocardiography by wall motion criteria

J Am Coll Cardiol 2007;50(14):1354-1361

A prospective multicenter trial has established that coronary flow reserve (CFR) helps predict survival for diabetic and nondiabetic patients with known or suspected coronary artery disease. Cardiologist Dr. Lauro Cortigiani of Campo di Marte Hospital in Lucca, Italy, and colleagues at four other teaching hospitals in Italy performed stress echocardiography on 1130 patients, including 207 diabetics with known or suspected coronary artery disease. Cortigiani found that an abnormal CFR score produced a more powerful prediction of future cardiac events and death in the 16 months after imaging (p>0.0001) than anti-ischemic therapy at the time of testing (

p

= 0.002), age (

p

= 0.02), or resting wall month abnormality (

p

= 0.05). The event rate was significantly higher for both diabetic and nondiabetic patients with abnormal CFR.

Aortic dilatation and dissection

Aortic dilatation and dissection in Turner syndrome

Circulation 2007;116(15):1663-1670

Research by Lea Ann Matura, Ph.D., and colleagues in the developmental endocrinology branch of the National Institute of Child Health and Human Development has attached hard numbers to the risk factors for aortic dissection among women diagnosed with Turner syndrome. The genetic condition, caused by the absence of an X chromosome, occurs in one of 2500 female births. Aortic root dilatation appears in 8% to 42% of Turner syndrome patients. It may be associated with the short height typical for TS women and may lead to aortic dissection and rupture. The study found that the average aortic diameters were identical for 166 TS subjects and 26 normal controls. But the ascending aortic diameters normalized to body surface area were significantly greater in the TS group. Nearly one-third of the TS women had values greater than the 95% percentile of 2 cm/m². Three TS women developed aortic dissections in the three years following initial MRI measurement. All had aortic size indices of more than 2.5 cm/m².

Risk assessment

Prognostic value of multidetector coronary computed tomographic angiography for prediction of all-cause mortality

J Am Coll Cardio 2007; 0(12):1161-1170

A multislice CT angiogram that fails to identify a greater than 50% coronary artery stenosis can almost guarantee that patients with chest pain will not die from heart-related illness in at least the following year. Dr. James K. Min, an assistant professor of Medicine at Weill Medical College of Cornell University, based this conclusion on evaluations of 1127 consecutive patients who were at least 45 years old and complained of chest pain before imaging. Min and colleagues calculated their all-cause death rate an average of 15.3 months (±3.9 month) after CT coronary angiography was performed. The survival rate for patients who had no stenoses occluding more than 50% of a coronary artery was 99.7%, compared with 96% survival for patients with one significant stenosis (>50% stenosis) and 70% for patients with two or more significant stenoses.