The carina as a useful radiographic landmark for positioning the intraaortic balloon pump.

The aortic knob is thought to be the most useful radiographic landmark for the proper positioning of the intraaortic balloon pump (IABP) tip. However, this has not been studied formally. In this study we assessed whether the aortic knob is a reliable landmark for positioning the IABP and compared it with another potential landmark, the carina. We measured the distance from the top of the distal aortic arch (aortic knob) to the left subclavian artery (LSCA) on three-dimensional computed tomography angiography in 100 patients. The distance from the level of the LSCA origin to the level of the carina was also measured using three-dimensional computed tomography in 150 additional patients. In 16% of the aortic knob study population, the LSCA to aortic knob distance was <0 cm or 0 cm. The median distance from the LSCA to the carina was 42 mm (range: 30-63 mm). In the carina study population, the origin of the LSCA was 35-55 mm above the carina in 95.3% of patients. In 16% of patients, the IABP was too close to the LSCA origin when it was placed at the aortic knob, whereas positioning the IABP at 2 cm above the carina provided an adequate position for the IABP tip (1.5-3.5 cm distal to the origin of the LSCA) in 95.3% of patients. The carina may be a more reliable landmark for positioning the IABP than the aortic knob.