Cardiac interventions carry risk from radiation

The radiation dose delivered during fluoroscopic cardiac interventional procedures should be subjected to rigorous and sustained scrutiny, according to researchers from Ireland. A team from the University College Dublin and the University of Ulster in Jordanstown, Belfast, is conducting an ongoing survey that is partially funded by the Health Research Board. The group presented its initial findings at the U.K. Radiological Congress in June.

Ireland has the highest rate of heart disease in Europe, accounting for 42% of all deaths, said lead researcher Catherine D'Helft from the School of Diagnostic Imaging, St. Anthony's in Dublin. She cites the Web site www.irishhealth.com as the source for this statistic.

Interventional cardiac procedures play an important role in tackling this problem, and the number of patients referred for interventional cardiology has increased as a result of the techniques' cost-effectiveness relative to surgery. Patients can be treated as outpatients or as day cases, and the complication rate is fairly low.

"However, the radiation doses associated with such procedures are high compared with other diagnostic x-ray examinations and have been reported to be close to thresholds causing deterministic radiation effects. This dose implication must be carefully monitored," D'Helft said.

The study aims to establish local x-ray dose reference levels for examinations in Irish cardiovascular centers and to produce a benchmark against which individual performance can be judged.

The researchers hope to quantify the ionizing radiation exposure to patients undergoing cardiac intervention and to identify causal agents in high-dose situations.

The goal is to encourage centers to take corrective action if necessary. Overall, the team seeks to establish ways of reducing radiation dose while maintaining image quality and diagnostic efficacy.

The researchers determined radiation exposure levels to patients for coronary angiography (CA), percutaneous coronary interventions (PCI), and permanent pacemaker insertion procedures (PPI). They detailed factors that may influence radiation dose, including patient demographics, the grade of the cardiologist, projections acquired, equipment specifications, exposure factors, and a complexity score for all examinations. They also identified elements associated with low radiation dose and acceptable/ high image quality.

Data on dose measurements using calibrated dose-area product meters, collated from 15 participating centers in the Republic of Ireland and Northern Ireland, are still being collected and analyzed. The researchers presented preliminary results at the UKRC and at the ECR in March. Mean dose values for CA, PCI, and PPI were 7426 cGycm2, 10,744 cGycm2, and 3705 cGycm2 respectively, although large examination-specific variations were apparent.

The team also compared data for CA and PCI procedures with radiation dose levels determined by the DIMOND project (Eur Radiol 2003;13:2259-2263), and it found that dose values from the Irish study were higher than those in the DIMOND project. For CA and PCI procedures, the radiation doses that were recorded in Ireland were 1.3 and 1.1 times higher, respectively, than those reported by the DIMOND group.

"Direct relationships are being noted between radiation doses and screening time and examination complexity," D'Helft said. "There is also some evidence to suggest that the grade of the operator, patient body mass index, and techniques employed also impact radiation dose levels."

Doses should be kept as low as reasonably achievable consistent with optimizing image quality. Significant variations in radiation dose exist, and doses appear to be higher than those published elsewhere, but the current results are preliminary, according to the Irish team.