Geometric and muscle physiological factors of the Frank-Starling mechanisms.
The relation between left-ventricular stroke volume (SV) and end-diastolic volume (EDV) was determined based on angiocardiographic measurements in 10 open-chest minipigs under varying filling conditions (blood letting or infusions). The results were compared with a theoretical relation calculated under the assumption of varying EDV but constancy of myocardial properties. In contrast to the linear increase of SV as a function of EDV as found in the animal experiments, the calculated curve reveals a maximum near the normal operating point with a decrease in the range of higher EDV. It can be concluded that the well-known increase of SV with increasing ventricular filling, beyond the normal EDV, is almost completely due to muscle physiological factors (mainly increase in Ca2+ sensitivity of the contractile apparatus), whereas the decrease of SV in the range of low filling pressure is mainly due to the geometrical conditions.
Jacob
R
R
Physiologisches Institut II, Universität Tübingen, FRG.
Dierberger
B
B
Gülch
R W
RW
Kissling
G
G
D000790:Angiocardiography; D000818:Animals; D003326:Coronary Circulation; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D012016:Reference Values; D012044:Regression Analysis; D013314:Stress, Mechanical; D013318:Stroke Volume; D013552:Swine; D013556:Swine, Miniature