The dilemma of diagnosing coronary calcification: angiography versus intravascular ultrasound.

OBJECTIVES: We sought to determine whether careful examination of angiograms in conjunction with other clinical information could reliably detect, quantitate and localize target lesion calcification before a coronary intervention.

BACKGROUND: The presence, extent and location of calcium in coronary artery lesions are important determinants of outcome after coronary intervention. Intravascular ultrasound is proposed as a superior technique for identifying patients with coronary artery calcification. However, the precise role of this costly and invasive method has not yet been established.

METHODS: Target lesion calcification was assessed in 183 patients (155 men; mean [+/-SD] age 58 +/- 10 years) by angiography and intravascular ultrasound before a planned percutaneous coronary intervention.

RESULTS: Ultrasound detected calcium in 138 patients (>90 degrees in 56, 91 degrees to 180 degrees in 52, 181 degrees to 270 degrees in 22 and > 270 degrees in 8), whereas angiography showed calcification in 63 (1+ in 32, 2+ in 27 and 3+ in 4). The two techniques agreed in 92 patients and disagreed in 91. Sensitivity and specificity of angiography were 40% and 82%, respectively. The arc of calcium by ultrasound was greater in patients with angiographically visible calcification (175 degrees +/- 85 degrees vs. 108 degrees +/- 71 degrees, p=0.0001). The depth of calcification by ultrasound was superficial in 61 patients (44%), deep in 68 (49%) and mixed in 8 (7%). The sensitivity of angiography in identifying superficial calcium was 35%. Of 120 patients without angiographically visible calcium at the target lesion site, 83 showed calcium by ultrasound. The only predictor of ultrasound calcium in these 120 patients was angiographic calcification elsewhere in the coronary tree (p=0.0001). The probability of any calcium and superficial >90 degrees calcium were 60% and 12%, respectively, in the 90 patients without angiographic calcifications anywhere in the coronary tree.

CONCLUSIONS: Despite poor sensitivity, angiography may help identify patients requiring intravascular ultrasound. When it is angiographically visible, the arc of calcium is likely to be large and superficial. Angiographic calcification at a remote site is a predictor of angiographically undetected target lesion calcium. Patients without angiographic calcification in the coronary tree may not need routine ultrasound examination, as the likelihood of >90 degrees superficial calcium is low.