Single perturbed beat vs. steady-state beats for assessing systolic function in the isolated heart.
Single-beat and steady-state techniques for evaluating end-systolic pressure-volume relationship (ESPVR) and Frank-Starling mechanism (FSM) in the crystalloid-perfused isolated rabbit heart were compared. In the single-beat technique, a train of stable isovolumic beats was interrupted with a single perturbed beat that either ejected against various levels of imposed isobaric load (ESPVR protocol) or beat isovolumically against various levels of end-diastolic volume (V(ED); FSM protocol). In steady-state technique, sustained beating was established, isobarically, at each of various loads (ESPVR protocol) or, isovolumically, at each of various V(ED) values (FSM protocol). ESPVR from steady-state technique lay above and to the left of that from single-beat technique. Contractile state was not uniform within steady-state technique, whereas it was uniform within single-beat technique. In the FSM protocol, single-beat technique exhibited the following features relative to steady-state technique: 1) greater range of developed pressures, 2) steeper ascending limb and more sharply defined maxima, 3) higher maximal developed pressure (Pdmax), and 4) greater volume at Pdmax(Vmax). Again. a common contractile state existed within single-beat technique but not within steady-state technique. It was concluded that single-beat technique was preferable to steady-state technique for evaluating ESPVR and FSM because 1) single-beat technique required less time for obtaining data, 2) single-beat technique allowed identification of uncomplicated values of Pdmax and Vmax, and 3) single-beat technique provided a common contractile-state reference for all data, whereas steady-state technique did not.
Campbell
K B
KB
Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman 99164-6520.
Taheri
H
H
Kirkpatrick
R D
RD
Slinker
B K
BK
D000818:Animals; D001794:Blood Pressure; D001810:Blood Volume; D005069:Evaluation Studies as Topic; D006321:Heart / Q000502:physiology*; D006334:Heart Function Tests; D006706:Homeostasis; D066298:In Vitro Techniques; D008297:Male; D011674:Pulse; D011817:Rabbits; D012044:Regression Analysis; D013599:Systole; D013997:Time Factors