Editing Chronotropic

{{Short description|Effects that change the heart rate}}
{{distinguish|Chronotype|Chronotope}}
{{more citations needed|date=August 2013}}
'''Chronotropic''' effects (from ''chrono-'', meaning time, and ''tropos'', "a turn") are those that change the [[heart rate]].

Chronotropic [[drugs]] may change the [[heart]] rate and [[cardiac cycle|rhythm]] by affecting the [[electrical conduction system of the heart]] and the [[Heart#Influences|nerves that influence it]], such as by changing the [[sinus rhythm|rhythm produced by]] the [[sinoatrial node]]. Positive chronotropes increase heart rate; negative chronotropes decrease heart rate.

A [[dromotropic|dromotrope]] affects [[atrioventricular node]] (AV node) conduction. A positive dromotrope increases AV nodal conduction, and a negative dromotrope decreases AV nodal conduction. A [[Lusitropy|lusitrope]] is an agent that affects diastolic relaxation.

Many positive [[inotrope]]s affect [[Preload (cardiology)|preload]] and [[afterload]].
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==Positive chronotropes==
* Most [[Adrenergic agonists]]
* [[Atropine]]
* [[Dopamine]]
* [[Epinephrine]]
* [[Isoproterenol]]
* [[Milrinone]]
* [[Theophylline]]<ref name="pmid9236443">{{cite journal|last=Alboni|first=P.|author2=Menozzi, C. |author3=Brignole, M. |author4=Paparella, N. |author5=Gaggioli, G. |author6=Lolli, G. |author7= Cappato, R. |title=Effects of Permanent Pacemaker and Oral Theophylline in Sick Sinus Syndrome: The THEOPACE Study: A Randomized Controlled Trial|journal=Circulation|year=1997|volume=96|issue=1|pages=260–266|doi=10.1161/01.CIR.96.1.260|pmid=9236443}}</ref>

==Negative chronotropes==
Chronotropic variables can be considered in systolic myocardial left and right sides. Left sided systolic chronotropy can be appreciated as Aortic Valve open to close time. Right sided variables are represented by pulmonary valve open to close time. Inverted as diastolic chronotropy, the variables are aortic valve close to open and pulmonic close to open time. Pharmaceutical manipulation of chronotropic properties was perhaps first appreciated by the introduction of [[digitalis]], though it turns out that digitalis has an [[inotropic]] effect rather than a chronotropic effect.
* [[Beta blockers]] such as [[metoprolol]]
* [[Acetylcholine]]
* [[Digoxin]]
* Pacemaker current (i.e. [[HCN channel]]) inhibitors (e.g. [[ivabradine]])<ref name="pmid32038284">{{cite journal|last=DiFrancesco|first=D.|title=A Brief History of Pacemaking|journal= Frontiers in Physiology|year=2020|volume=10|pages=1599|doi=10.3389/fphys.2019.01599|pmid=32038284|pmc=6987461|doi-access=free}}</ref>

==References==
{{Reflist}}

{{Cardiovascular physiology}}

[[Category:Cardiovascular physiology]]
[[Category:Antiarrhythmic agents]]


{{cardiovascular-drug-stub}}