1353542 - Peak Aortic Stroke Volume on Dobutamine Stress Cardiac Magnetic Resonance Is Highly Correlated with Oxygen Pulse on Cardiopulmonary Exercise Test

Dobutamine stress cardiac magnetic resonance imaging (DSCMR) has been considered a reliable test in the risk stratification of pediatric patients with coronary artery anomalies (CAA). In this study, we aimed to measure change in aortic stroke volume (Ao-SV) during a DSCMR and compare peak Ao-SV with oxygen pulse (O2P), a function of stroke volume, from cardiopulmonary exercise test (CPET).

Methods:

Standard phase-contrast method was used on a Siemens 1.5 T scanner to measure Ao-SV at rest and peak pharmacologic stress in addition to standard DSCMR protocol. Peak heart rate ≥ 150 beats per minute (bpm) and rate.pressure product ≥ 20000 bpm.mmHg were used to consider a maximal DSCMR. Inducible first-pass perfusion defect was determined by visual assessment. CPET was performed using Standard Bruce Treadmill protocol and O2P was measured using a metabolic card. We used Wilcoxon signed-rank test to assess individual changes in Ao-SV between rest and stress and Spearman correlation test to evaluate correlation of peak Ao-SV and O2P.

Results:

A total of 19 patients (males 10, 53%) with CAA undergoing DSCMR at a median age of 16 years old (interquartile range (IQR) 12, 17), including 3/19 with inducible hypoperfusion. Ao-SV increased (DAo-SV=7 ml (10%), IQR [3, 15]) in 14/19 patients (74%) from a baseline median of 72 ml (IQR 59, 81) to 80 ml (IQR 70, 101) (p=0.001) and decreased ((DAo-SV=6 ml (9%), IQR [5, 8]) in 5/19 patients (26%) from 73 ml (IQR 64, 87) to 58 (56, 80) (p=0.04). Cardiac output rose from 96 ml/kg/min (IQR 84, 119) to 218 ml/kg/min (IQR 181, 252) with a total of 129% increase (IQR 87, 150). There was no statistical difference in peak heart rate, peak systolic and mean blood pressure, peak rate.pressure product, or percent increase in heart rate, blood pressures, rate-pressure product, or calculated cardiac output during DSCMR between the 2 groups. Ao-SV was highly associated with O2P (median 9.8 ml, [IQR 9.3, 13.4]) on CPET performed within 30 days (IQR 10, 50) of DSCMR (r = 0.88, p < 0.001, Figure).



Conclusion:

Peak Ao-SV on DSCMR is highly correlated with marker of stroke volume on CPET in pediatric patients with CAA. Cardiac output rise during DSCMR is primarily secondary to increase in heart rate. Stroke volume increased in 75% of patients and decreased in 25% during a DSCMR. Future study is important to understand the significance of Ao-SV change pattern during a DS-CMR.