Influence of ventricular pacing on myocardial oxygen tension.
BACKGROUND
The influence of heart rate on cardiac output, oxygen consumption, and myocardial activity has been widely investigated. However, the influence of heart rate on myocardial oxygen tension (pO2) remains unclear. Since the introduction of flexible pO2 micro catheters to measure partial oxygen tension in a working muscle, it is possible to investigate the influence of heart rate on myocardial oxygen tension.


METHODS
Intraoperatively, a flexible pO2 micro catheter was positioned in the mid-myocardium of 8 male farm pigs. The heart rate was varied via an external pacer from base rate up to fibrillation and the corresponding myocardial pO2 was measured.


RESULTS
Within 2 min, the myocardial pO2 adjusted to a change in heart rate. In this animal model, an optimal myocardial pO2 was observed at 109 bpm. A further increase in heart rate led to a decrease in myocardial pO2. When the heart rate was reaching the level of a fibrillation, pO2 dropped to zero.


CONCLUSIONS
In young healthy pigs--with a normal blood vessel regulation and the pharmacologic and experimental conditions used in this study--a significant relation between myocardial pO2 and heart rate was observed. Myocardial oxygen tension increased during cardiac pacing until a heart rate of 109 bpm. Thereafter a decline of pO2 occurred. Each change in heart rate resulted in a corresponding change of pO2 within roughly 2 min.
Matschke
Klaus
K
Department of Cardiac Surgery, Heart Center Dresden Ltd. University Hospital, Fetscherstr. 76, D-01307 Dresden, Germany. M.Weber@herzzentrum-dresden.com
Pfeiffer
Steffen
S
Mrowietz
Christoph
C
Geisler
Thomas
T
Tugtekin
Sems M
SM
Park
Jai-Wun
JW
Knaut
Michael
M
Jung
Friedrich
F
D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000502:physiology; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D007432:Intraoperative Period; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000097:blood / Q000378:metabolism*; D010101:Oxygen Consumption; D010313:Partial Pressure; D015203:Reproducibility of Results; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000378:metabolism* / Q000503:physiopathology; D016276:Ventricular Function
D010100:Oxygen