Editing Chronotropic (section)

==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>