Impact of Regadenson in the calculation of cardiac output values

Background: Regadenoson is widely used in clinical practice as an alternative to adenosine for pharmacologic stress perfusion imaging. Unlike adenosine, regadenoson has a longer half-life, with vasodilatory effects lasting up to 30 minutes. This prolonged activity may influence hemodynamic parameters and potentially affect the accuracy of cardiac function measurements. This study aimed to evaluate whether regadenoson’s extended half-life significantly impacts cardiac output over time and whether functional imaging should be acquired exclusively prior to its administration.

Methods: Twenty-six patients undergoing cardiac MRI perfusion stress imaging with regadenoson were included in this study (Table 1). Imaging was performed on two scanners: 13 patients (50%) on a Siemens MAGNETOM Sola 1.5T, and 13 (50%) on a Siemens MAGNETOM Vida 3T. All patients received a 0.4 mg (5 mL) intravenous bolus of regadenoson.

Three full balanced steady-state free precession (bSSFP) short-axis cine stacks were acquired:

1. Baseline- Before regadenoson injection.
2. Early Post-Stress- Five minutes after regadenoson injection.
3. Late Post-Stress – more than 25 minutes after injection.

Cardiac output was measured by three independent observers, and the average indexed cardiac output was used for analysis. During the second short-axis acquisition, patients' heart rate remained elevated by approximately 22% on average compared to baseline, whereas by the third scan, the heart rate difference was minimal (5% on average).

2.

2.

<

Results: Table 2 demonstrates no statistically significant changes in cardiac output across the three timepoints. Compared to baseline, the indexed ejection fraction increased by an average of 5% at 5 minutes post-injection, with the highest value increment in the left ventricular end-systolic volume by 7%.

No significant variations were observed when comparing early and late post-injection measurements to baseline.

Conclusion: This study demonstrates that regadenoson’s prolonged vasodilatory effect does not significantly alter cardiac output measurements when using standard cine imaging. The values of indexed cardiac output and other functional parameters remained stable across timepoints, with only minor changes observed.

These findings suggest that, from a timing efficiency perspective, acquiring short-axis cine imaging between the stress and rest perfusion acquisitions—rather than before the stress agent—is appropriate and does not compromise functional assessment.

Table 1- Population

Patient sex	Number of patients	Age group	Number of patients
Male	14	< 40 years old	5
		41-50 years old	2
Female	12	51-60 years old	7
		61-70 years old	9
		> 71 years old	3

Table 2- Results

	Difference between baseline and early post-stress	Difference between earlypost- stress and late post-stress	Difference between baseline and late post-stress
LVEDV	-1%	-2%	+1%
LVESV	-7%	-6%	-1%
LVSV	+4%	+1%	+3%
LVEF	+5%	+3%	+2%
LV mass	+2%	-1%	+3%
RVEDV	+3%	-1%	+4%
RVESV	-2%	-6%	+2%
RVSV	+5%	1%	+3%
RVEF	+2%	3%	-2%