Why the study?
How do changes in heart rate, preload, afterload, and inotropy affect left ventricular dP/dt max compared to external stroke work in an in situ dog heart model?
How do changes in heart rate, preload, afterload, and inotropy affect left ventricular dP/dt max compared to external stroke work in an in situ dog heart model?
The study demonstrates that pre-ejection measurements like dP/dt max may diverge from actual pump performance (stroke work) under certain conditions, questioning their interchangeable use in assessing inotropic agents.
Answers are grounded in this paper and cite their sources.
dP/dt max may diverge from stroke work with heart rate changes; leaves open their interchangeable use for inotropic assessment.
Dog hearts were prepared in situ so that heart rate (HR), left ventricular end diastolic pressure (LVEDP) and mean aortic pressure (MAP) could be controlled separately during computation of left ventricular dP/dt max and external stroke work (SW). Progressive increases in HR consistently raised dP/dt max over a wide range, and consistently lowered SW except at low rates. Progressive increases in LVEDP or MAP consistently raised both dP/dt max and SW. Infusion of noradrenaline consistently raided both dP/dt max and SW, except at very high HR when only dP/dt max was consistently raised. Our results lead us to question the validity of equating changes in pre-ejection measurements with changes in performance of the heart as a pump under abnormal conditions and in the assessment of inotropic agents.
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Kane et al. (1976) studied this question.
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