Equivalent heart rate during ventricular fibrillation in the dog heart: mechanoenergetic analysis.
We propose equivalent heart rate (eHR) as an estimate of the frequency of contractions of individual myocytes in a fibrillating ventricle by analyzing mechanics and energetics of the ventricle. Using the isolated, cross-circulated dog heart preparation, we determined eHR in two different ways. First, we obtained eHR (eHR1) from myocardial O2 consumption (Vo2)-equivalent pressure-volume area (ePVA) data points during ventricular fibrillation (VF) by utilizing the Vo2-pressure-volume area (PVA) relation in the beating state. PVA is the area surrounded by the end-systolic and end-diastolic pressure-volume relations and the systolic pressure-volume trajectory in the pressure-volume diagram. PVA has been shown to represent the total mechanical energy generated by each contraction. We have recently proposed ePVA as a measure of the total mechanical energy generated by single contractions of all individual asynchronously contracting myocytes in a fibrillating ventricle. ePVA is the area surrounded by the horizontal line at the VF pressure and the end-systolic and end-diastolic pressure-volume relations in the beating state. Second, we measured Vo2 in beating state at various heart rates and Vo2 during VF under a mechanically unloaded condition. By comparing these fibrillating and beating Vo2 values, we determined eHR (eHR2) for the fibrillating state. eHR1 was 216 +/- 27 beats/min and eHR2 was 223 +/- 26 beats/min. These two values were not significantly different. We conclude that the average frequency of contractions of individual myocytes in a fibrillating ventricle is equivalent approximately to 220 beats/min in terms of ventricular energetics.
Yaku
H
H
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Suita, Japan.
Goto
Y
Y
Futaki
S
S
Ohgoshi
Y
Y
Kawaguchi
O
O
Hata
K
K
Takasago
T
T
Suga
H
H
D000818:Animals; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology; D003427:Cross Circulation; D004285:Dogs; D004734:Energy Metabolism; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D014693:Ventricular Fibrillation / Q000473:pathology / Q000503:physiopathology*