Time to dP/dtmax reflects both inotropic and chronotropic properties of cardiac contraction: a conscious dog study.
This study supports a mathematical model and previous findings indicating that td, the time from onset of contraction to dP/dtmax, reflects the time-dependent aspects of contraction and hence decreases with increasing contractility. Combined data from 20 conscious instrumented dogs create a highly significant inverse and linear td-HR (heart rate) relation. Both norepinephrine and isoproterenol decreased td values, but norepinephrine, in contrast to isoproterenol, decreased the heart rate by a reflex response. Despite the remarkable decline in heart rate (25.8%) td was decreased (16.5%). During wide spontaneous R-R variations longer preceding intervals gave shorter td values. The latter two facts indicate the dependence of td on the contractile state rather than it being merely interval dependent.
Adler
D
D
Department of Biomedical Engineering Hadassah University Hospital, Ein Kerem, Jerusalem, Israel.
Nikolic
S D
SD
Pajaro
O
O
Sonnenblick
E H
EH
Yellin
E L
EL
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology; D004285:Dogs; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008962:Models, Theoretical; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D013268:Stimulation, Chemical; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D002316:Cardiotonic Agents; D007545:Isoproterenol; D009638:Norepinephrine