Metabolic response of normal human myocardium to high-dose atropine-dobutamine stress studied by 31P-MRS.
BACKGROUND
31P-MRS during cardiac stress may provide (patho)physiological insights into the high-energy phosphate metabolism of the myocardium. Accordingly, the purpose of the present study was to determine the metabolic response of normal human myocardium to severe atropine-dobutamine (A-D) stress. To corroborate the results from the present in vivo study, a 31P-MRS experiment was performed with a moving phantom to simulate respiratory motion.


RESULTS
The phantom experiment showed no relation (P=.371) between the intensity ratio of two separate phosphate peaks and amplitude of phantom excursions. The phosphocreatine (PCr) and ATP signal strength and the PCr/ATP ratio were determined from the left ventricular wall in 20 healthy subjects (posttest likelihood for coronary artery disease was <2.5%) with 31P-MRS at rest and during high-dose A-D stress (rate-pressure product increased threefold). Stress-induced changes were -21% for PCr (P<.001) and -9% for ATP (P<.05). The average PCr/ATP value at rest was 1.42+/-0.18 and decreased by 14% to 1.22+/-0.20 during stress (P<.001).


CONCLUSIONS
The phantom experiment shows that the in vivo decrease of myocardial PCr/ATP due to high-dose A-D stress we observed is not a motion artifact. Consequently, this indicates that myocardial high-energy phosphate metabolism of the normal human heart is altered at high workloads.
Lamb
H J
HJ
Department of Radiology, Leiden University Medical Center, and the Heart Lung Institute, The Netherlands.
Beyerbacht
H P
HP
Ouwerkerk
R
R
Doornbos
J
J
Pluim
B M
BM
van der Wall
E E
EE
van der Laarse
A
A
de Roos
A
A
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D000368:Aged; D001285:Atropine; D004280:Dobutamine; D005080:Exercise Test; D005260:Female; D006439:Hemodynamics; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*
D010725:Phosphocreatine; D004280:Dobutamine; D001285:Atropine; D000255:Adenosine Triphosphate