Study reveals 'magic angle' in cardiac CT

According to new research in Academic Radiology, a 70-degree lead tip angle was found to ensure diagnostic image quality of all modalities in CT pacemaker imaging, leading authors to dub it the “magic angle.”

More than one million cardiovascular implantable electronic devices including pacemakers (PMs) and implantable cardioverter-defibrillators (ICDs) are being implanted in people with cardiovascular diseases each year, noted corresponding author Sebastian D. Reinartz, MD, with the department of diagnostic and interventional radiology at University Hospital in RWTH Aachen University in Germany, and colleagues.

Guidelines for evaluating protrusions or perforations involving cardiac lead implants are strict, calling for an electrocardiography-synchronized CT of the heart. However, metal artifacts often impede, limiting visualization of the lead tip, which is a critical obstacle for patient safety.

With that in mind, German researchers compared two CT techniques (Dual-Energy CT [DECT] and Dual-Source CT [DSCT]) along with the influence of incremental alterations of current-time product and PM lead-tip angle with respect to the gantry plane.

The ex vivo phantom study examined four pacemaker leads and one ICD lead using the CT techniques. A total of 344 images were rated on a five-point Likert scale.

The most notable finding proved to be positioning the lead-tip angle at 70 degrees resulted in 100 percent diagnostic image quality, while “the commonly applied 90-degree positioning of the PM lead tip is the worst possible angle to use in imaging,” wrote Reinartz et al.

DECT and dual-source DSCT techniques each scored an 86 percent diagnostic image quality. In the testing the current-time product, there was “no statistically significant change” found, according to Reinartz et al.

Authors noted further research analyzing in vivo leads must be conducted systematically to gain reliable results.