Chronotropic

Not to be confused with Chronotype or Chronotope.

Chronotropic effects (from chrono-, meaning time, and tropos, "a turn") are those that change the heart rate.

Chronotropic drugs may change the heart rate by affecting the nerves controlling the heart, or by changing the rhythm produced by the sinoatrial node. Positive chronotropes increase heart rate; negative chronotropes decrease heart rate.

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

Many positive inotropes affect preload and afterload.

Negative chronotropes

Chronotropic variables in systolic myocardial left and right. 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
The non-dihydropyridine calcium channel blockers diltiazem and verapamil

Positive chronotropes

References

↑ Alboni, P.; Menozzi, C.; Brignole, M.; Paparella, N.; Gaggioli, G.; Lolli, G.; Cappato, R. (1997). "Effects of Permanent Pacemaker and Oral Theophylline in Sick Sinus Syndrome: The THEOPACE Study: A Randomized Controlled Trial". Circulation 96: 260–266. doi:10.1161/01.CIR.96.1.260. PMID 9236443.

Physiology of the cardiovascular system

Heart

Cardiac output	Cardiac cycle Cardiac output Heart rate Stroke volume Stroke volume End-diastolic volume End-systolic volume Afterload Preload Frank–Starling law of the heart Cardiac function curve Venous return curve Wiggers diagram Pressure volume diagram

Ultrasound	Fractional shortening = (End-diastolic dimension End-systolic dimension) / End-diastolic dimension Aortic valve area calculation Ejection fraction Cardiac index

Heart rate	Cardiac pacemaker Chronotropic (Heart rate) Dromotropic (Conduction velocity) Inotropic (Contractility) Bathmotropic (Excitability) Lusitropic (Relaxation)

Conduction	Conduction system Cardiac electrophysiology Action potential cardiac atrial ventricular Effective refractory period Pacemaker potential Electrocardiography P wave PR interval QRS complex QT interval ST segment T wave U wave Hexaxial reference system

Chamber pressure	Central venous Right atrial ventricular pulmonary artery wedge Left atrial ventricular Aortic

Other	Ventricular remodeling

Vascular system/
Hemodynamics

Blood flow	Compliance Vascular resistance Pulse Perfusion

Blood pressure	Pulse pressure Systolic Diastolic Mean arterial pressure Jugular venous pressure Portal venous pressure

Regulation of BP	Baroreflex Kinin–kallikrein system Renin–angiotensin system Vasoconstrictors Vasodilators Autoregulation Myogenic mechanism Tubuloglomerular feedback Cerebral autoregulation Paraganglia Aortic body Carotid body Glomus cell

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