CTA effective for monitoring late heart transplant complications

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Cardiac CT angiography (CTA) has been shown to have high accuracy in detecting cardiac allograft vasculopathy (CAV) in heart transplant recipients, making it a viable alternative to invasive coronary angiography, according to a study published in the August issue of Radiology.

“Cardiac [CTA] was feasible without the need for heart rate–lowering drugs and produced diagnostic-quality images in most patients that resulted in high diagnostic accuracy with excellent sensitivity, specificity, and negative predictive value in comparison with invasive angiography,” wrote Tarun K. Mittal, MD, of Harefield Hospital, Royal Brompton & Harefield NHS Foundation Trust, Middlesex, England, and colleagues.

CAV is a common late complication related to heart transplantation that is typically seen as thickening of the middle and distal segments and in the side branches of the arteries, explained the authors. About 8 percent of heart transplant patients experience CAV within one year of transplant, and more than half present with CAV by 10 years.

“Because CAV is the most common cause for late-stage mortality in heart transplant recipients, and its diagnosis requires routine surveillance with invasive angiography, evaluation of noninvasive alternatives remains important,” wrote Mittal and colleagues. Unfortunately, previously studied noninvasive techniques—including treadmill exercise test and myocardial perfusion scans—have lacked adequate sensitivity in the detection of CAV.

To evaluate whether CTA without the use of beta-blockers could stack up with invasive angiography, the authors took 138 heart transplant recipients scheduled for routine invasive angiography and prospectively enrolled them to receive CTA on a 64-section scanner. All patients also received a coronary artery calcification (CAC) scan.

Results showed that absence of calcification alone does not exclude CAV, as 6 percent of patients without CAC had the complication. Increasing CAC is correlated with prevalence of CAV, but the use of a CAC scan is not reliable in identifying CAV, according to the authors.

While the transplant recipients demonstrated increase heart rates, CTA without beta-blockers provided adequate image quality in 96 percent of patients and in 98 percent of the total segments. The noninvasive technique had an area under the receiver operating characteristic curve, sensitivity, specificity, and positive and negative predictive values of 0.880, 98 percent, 78 percent, 77 percent and 98 percent, respectively, for diagnosis of CAV, reported the authors. No patients with normal CTA results demonstrated CAV on invasive angiographic images.

“CT angiography can be used for routine surveillance of CAV in heart transplant recipients, with invasive angiography reserved for those suspected of having substantial or indeterminate stenosis,” wrote Mittal and colleagues.