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Tetralogy of Fallot: Postoperative Delayed Recovery of Left Ventricular Stroke Volume after Physical Exercise—Assessment with Fast MR Imaging¹

¹ From the Departments of Radiology (A.A.W.R., A.d.R., H.J.L., J.D., P.K.), Cardiology (A.A.W.R., E.E.v.d.W.), Pediatric Cardiology (A.A.W.R., W.A.H.), and Pulmonology (J.G.v.d.A.), Leiden University Medical Center, Albinusdreef 2, Bldg 1-C2S, 2333 ZA Leiden, the Netherlands; and Interuniversity Cardiology Institute of the Netherlands, Utrecht (A.A.W.R., A.d.R., E.E.v.d.W.). Received July 9, 2001; revision requested August 20; final revision received April 15, 2002; accepted May 14. Address correspondence to H.J.L. (e-mail: h.j.lamb@lumc.nl).

View larger version (20K): [in a new window]   Figure 1. Schematic shows the MR examination protocol. Throughout the entire examination, 21 MR flow maps of the ascending aorta were assessed (vertical black bars). The first flow measurement was obtained at the beginning of the examination during the resting period; the second measurement, at the steady-state exercise level. A period of 4 minutes during passive recovery after exercise was covered with 19 flow measurements in 15-second intervals. Acquisition time for a complete flow map was eight heartbeats.

View larger version (23K): [in a new window]   Figure 2. Time course shows changes in mean heart rate of control subjects and patients during recovery from ergometer exercise. Curves show mean values plus or minus standard error of the mean. No difference in heart rate recovery was found between the groups during the entire period.

View larger version (119K): [in a new window]   Figure 3. Modulus (M) and phase (P) images acquired perpendicular to the ascending aorta at the level of the pulmonary trunk at different points in the cardiac cycle (top) during exercise and (bottom) 4 minutes after termination of exercise. The modulus images are anatomic, whereas the pixel intensity in the phase images represents velocity information. In the phase images, pixel intensity in the ascending aorta is higher at 116 and 232 msec in the images obtained during exercise compared with that in images obtained 4 minutes after exercise. Image quality was sufficient to allow evaluation of flow in the ascending aorta at rest, with exercise, and during the recovery period.

View larger version (31K): [in a new window]   Figure 4. Top: Flow volume curves in a patient and a control subject at rest, during exercise, and during the recovery period. Bottom: Corresponding stroke volumes, expressed as a percentage of the rest value, for each flow volume curve. Stroke volume increases in response to physical exercise. In the patient, an initial increase in stroke volume exceeds that during exercise; throughout the entire recovery period, stroke volume is higher than that in the control subject.

View larger version (26K): [in a new window]   Figure 5. Time course of stroke volume during recovery after exercise. Curves show mean values plus or minus standard error of the mean. All participants showed an increase in stroke volume after termination of exercise. However, differences in the change in stroke volume during the 4-minute recovery period were significant between control subjects and patients (P < .01, mixed-model analysis of variance).

View larger version (25K): [in a new window]   Figure 6. Time course of cardiac output during recovery after exercise. Curves show mean values plus or minus standard error of the mean. Cardiac output in patients decreased significantly more slowly than that in control subjects (P < .01, mixed-model analysis of variance).