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

heart rate Heart rate is the frequency of the cardiac cycle, heartbeat measured by the number of contractions of the heart per minute (''beats per minute'', or bpm). The heart rate varies according to the body's Human body, physical needs, including the nee ...

. Chronotropic

drugs A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via inhalation, injection, smoking, ingestio ...

may change the

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

rate and

rhythm Rhythm (from Greek , ''rhythmos'', "any regular recurring motion, symmetry") generally means a " movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions". This general meaning of regular r ...

by affecting the

electrical conduction system of the heart The cardiac conduction system (CCS, also called the electrical conduction system of the heart) transmits the Cardiac action potential, signals generated by the sinoatrial node – the heart's Cardiac pacemaker, pacemaker, to cause the heart musc ...

and the nerves that influence it, such as by changing the rhythm produced by the

sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node, sinus node or Keith–Flack node) is an ellipse, oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of Cell (biology), cells known as pa ...

. Positive chronotropes increase heart rate; negative chronotropes decrease heart rate. A dromotrope affects

atrioventricular node The atrioventricular node (AV node, or Aschoff-Tawara node) electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. The AV node lies at the ...

(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

inotrope An inotrope or inotropic is a drug or any substance that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular ...

s affect preload and

afterload Afterload is the pressure that the heart must work against to eject blood during systole (ventricular contraction). Afterload is proportional to the average arterial pressure. As aortic and pulmonary pressures increase, the afterload increases on ...

. __TOC__

Positive chronotropes

* Most Adrenergic agonists *

Atropine Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate, and to decrease saliva production during surgery. It is typically give ...

Dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...

Epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands a ...

* Isoproterenol * Milrinone *

Theophylline Theophylline, also known as 1,3-dimethylxanthine, is a drug that inhibits phosphodiesterase and blocks adenosine receptors. It is used to treat chronic obstructive pulmonary disease (COPD) and asthma. Its pharmacology is similar to other met ...

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 ''Digitalis'' ( or ) is a genus of about 20 species of herbaceous perennial plants, shrubs, and Biennial plant, biennials, commonly called foxgloves. ''Digitalis'' is native to Europe, Western Asia, and northwestern Africa. The flowers are ...

, though it turns out that digitalis has an

inotropic An inotrope or inotropic is a drug or any substance that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular co ...

effect rather than a chronotropic effect. *

Beta blockers Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms (arrhythmia), and to protect the heart from a second heart attack after a first heart attack (secondary prevention). ...

such as metoprolol *

Acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...

Digoxin Digoxin (better known as digitalis), sold under the brand name Lanoxin among others, is a medication used to treat various heart disease, heart conditions. Most frequently it is used for atrial fibrillation, atrial flutter, and heart failure. ...

* Pacemaker current (i.e. HCN channel) inhibitors (e.g.

ivabradine Ivabradine, sold under the brand name Procoralan among others, is a medication, which is a pacemaker current (I''f'') inhibitor, used for the symptomatic management of heart-related chest pain and heart failure. Patients who qualify for use o ...

)

References

Cardiovascular physiology Antiarrhythmic agents {{cardiovascular-drug-stub