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


OBJECTIVE
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.


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.


CONCLUSIONS
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.
Flinck
Marianne
M
Department of Radiology, Sahlgrenska University Hospital and Sahlgrenska Academy at Gothenburg University, Sweden.
Gradén
Asa
A
Milde
Helén
H
Flinck
Agneta
A
Hellström
Mikael
M
Björk
Jonas
J
Nyman
Ulf
U
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001835:Body Weight; D002302:Cardiac Output / Q000502:physiology*; D003287:Contrast Media / Q000008:administration & dosage*; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011446:Prospective Studies; D012212:Rheology / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media