Cardiac output measured by electrical velocimetry in the CT suite correlates with coronary artery enhancement: a feasibility study

Abstract

Background: Cardiac output (CO) is inversely related to vascular contrast medium (CM) enhancement during computed tomography (CT). Impedance cardiography with a new technique, electrical velocimetry (EV), may create opportunities to measure CO pre-examination for adaptation of CM injection parameters.

Purpose: To relate CO_EV measured by radiology staff to aortic attenuation as a measure of coronary artery attenuation during CT coronary angiography (CTCA), and to formulate a tentative statistical model to adapt CM injection parameters to CO.

Material and Methods: CO_EV was measured immediately before 100 kVp CTCA (64-multirow detector) in 27 patients with presumed coronary artery disease. For CTCA, 260 mg I/kg (maximum dosage weight: 80/90 kg for women/men) was injected intravenously during 12 s. Simple linear regression analysis was performed to explore the correlation between aortic attenuation (Hounsfield units, HU) and body weight, the influence of CO_EV on aortic attenuation adjusted to injected CM dose rate (HU per mg I/kg/s), and to establish a tentative formula on how to adapt CM injection parameters to CO_EV and desired aortic attenuation.

Results: The correlation between aortic attenuation and body weight was weak and non-significant (r=−0.14 after outlier exclusion). A significant negative correlation (r=−0.63) was found between aortic attenuation adjusted to injected CM dose rate (HU per mg I/kg/s) and CO_EV. The resulting formula, CM dose rate=CO_EV×(aortic attenuation−240)/55, made it possible to calculate CM volumes and injection rates at various COs and, for example, the present mean aortic attenuation (438 HU), injection time (12 s), CM concentration (320 mg I/ml), and a certain body weight.

Conclusion: EV makes it possible to measure CO in the CT suite before vascular examinations. Hence, CM doses may be decreased in low CO states to reduce the risk of CM-induced nephropathy without jeopardizing diagnostic quality and may be increased in high CO states to avoid poor enhancement.

Key words::

• Contrast enhancement
• coronary angiography
• contrast medium-induced nephropathy

Acknowledgments

We thank Krister Johansson, Bluegrass AB, Mölnlycke, Sweden, for placing an electrical velocimeter (Aesculon^®) at our disposal during the study and librarian Elisabeth Sassersson for excellent service regarding literature references.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.