Mechanisms for cardiac output augmentation in patients with a systemic right ventricle.
BACKGROUND
Conflicting data have been published on the differences in cardiac response to exercise between patients with an atrially switched transposition of the great arteries (TGA), and patients with a congenitally corrected TGA (ccTGA). The purpose of our study was to evaluate the differences in cardiac response to exercise in these 2 patient groups with a systemic right ventricle (RV).


METHODS
Thirty four patients (62% male; mean 35, range 21-69 years) with a systemic RV (20 with an atrially switched TGA and 14 with a ccTGA) were included. Exercise tests with Portapres measurements were performed to assess maximal exercise capacity (V'O(2peak)), cardiac index, stroke volume index, and heart rate augmentation. Cardiac function was assessed by Cardiovascular Magnetic Resonance or Computed Tomography, and serum NT-proBNP levels.


RESULTS
We found that both groups were able to significantly augment cardiac index during exercise. Cardiac index augmentation during exercise was positively related to V'O(2peak) (r=0.37, p<0.05), and independent of resting cardiac function. Although the increase in cardiac index during exercise was similar in both patients with TGA and with ccTGA, mechanisms to achieve this increase differed between groups. ccTGA patients increased both stroke volume and heart rate during exercise. Atrially switched TGA patients augmented heart rate during exercise, but failed to increase stroke volume.


CONCLUSIONS
Mechanisms to achieve cardiac output augmentation differ between ccTGA patients and TGA patients. We suggest that therapeutic approaches should be tailored to the specific patient group to avoid counterproductive effects.
Winter
Michiel M
MM
Department of Cardiology, Academic Medical Center, Amsterdam, The Netherlands.
van der Plas
Mart N
MN
Bouma
Berto J
BJ
Groenink
Maarten
M
Bresser
Paul
P
Mulder
Barbara J M
BJ
D000328:Adult; D000368:Aged; D015444:Exercise / Q000502:physiology*; D005260:Female; D006334:Heart Function Tests; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013318:Stroke Volume / Q000502:physiology*; D014057:Tomography, X-Ray Computed; D014188:Transposition of Great Vessels / Q000503:physiopathology* / Q000601:surgery*; D018497:Ventricular Dysfunction, Right / Q000175:diagnosis / Q000503:physiopathology*; D055815:Young Adult