Difference between Inotropic, Chronotropic and Dromotropic

Key Difference: Inotropic, Chronotropic, and Dromotropic are different types of cardiac drugs. This classification is based on the way these drugs are used for the treatment of a particular condition. Inotropic drugs affect the force of cardiac contraction. Chronotropic drugs affect the heart rate.  Dromotropic drugs affect conduction velocity through the conducting tissues of the heart.

Inotropic, Chronotropic and Dromotropic are different types of cardiac drugs. This classification is based on the way these drugs are used for the treatment of a particular condition. Inotropic drugs affect the force of cardiac contraction. Chronotropic drugs affect the heart rate.  Dromotropic drugs affect conduction velocity through the conducting tissues of the heart. 

See: Difference between heart attack and heart failure

Inotropic agents basically affect the contraction of the heart muscles. There are two types of inotropic agents– Positive inotropic agents increase the force of myocardial contraction. On the other hand, negative inotropic agents decrease the force of myocardial contraction. Also see: Heart attack Vs. Cardiac arrest. 

Positive inotropic agents include dopamine, isoprenaline, etc. Negative inotropic agents include beta blockers, quinidine, flecainide, etc. Positive inotropes are also known as sympathomimetic drugs. Inotropes are used to treat impaired cardiac contractility. Also see: Heart attack Vs. Stroke

 

Chronotropic is another type of cardiac drug which affects heart rate. They are further classified into positive and negative chronotropic agents. Positive chronotropic increases the heart rate by the acceleration of the rate of impulse formation in the SA node. Negative chronotropic drugs are just opposites of positive chronotropic agents as they slow down the heart rate by decreasing impulse formation. Also see: Difference between Heart Attack and Panic Attack

Dromotropic drugs affect the conduction of electrical impulses through the myocardium. Positive dromotropic drugs increase this rate of conduction, whereas negative dromotropic drugs decrease this rate of electrical conduction.

These cardiovascular drugs differ from each other primarily on the basis of the aspects related to cardiac performance which they influence or effect. 

Also see: Difference between Anxiety and Heart Attack

Comparison between Inotropic, Chronotropic, and Dromotropic:

 

Inotropic

Chronotropic

Dromotropic

Definition

Affects the force of cardiac contraction

Affects the heart rate

Affects conduction velocity through the conducting tissues of the heart

Classification

Positive Inotropic – strengthens the force of cardiac contraction

 

Negative Inotropic – weakens the force of cardiac contraction

Positive chronotropic – accelerates the heart rate

 

Negative chronotropic – slows down the heart rate

Positive dromotropic –  speeds up conduction

 

Negative dromotropic - slow down conduction

Examples

Positive Inotropic – dopamine, adrenaline, etc.

 

Negative Inotropic – labetalol and propanolol

Positive chronotropic – Adernaline

 

Negative chronotropic – digoxin

Positive dromotropic –  phenytoin

 

Negative dromotropic -  verapamil

Origin of word

From Greek in-, meaning fiber or sinew)

From chrono-, meaning time, and tropos, "a turn"

From the Greek word "dromos", meaning running, a course, a race

Image Courtesy: khanacademy.org, dailymail.co.uk

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Comments

Yeah it's a good explanation...And thank you...

Dr.Nidhi

Mon, 01/15/2018 - 23:13

minimal satisfaction attained... otherwise go and become a billionare like trump

unknown

Sat, 10/14/2017 - 04:22

Wow, clear and nice.

doctor

Tue, 07/11/2017 - 17:03

well explained, thanks

Tere

Fri, 06/30/2017 - 16:46

Really helpful, thank you.

K B

Mon, 06/06/2016 - 10:31

A very satisfying clarification simple and to the point!

Kibrom Tesggai

Tue, 03/08/2016 - 21:39

I believe your drug examples are incorrect. Digoxin deals with contractility, it is POSITIVE Inotropic. Digoxin gives your heart a more powerful efficient pump. Propranolol is NEGATIVE chronotropic as it slows down the heart rate, which is why you need to assess heart rate before administration, because if it's below 60bpm administration is contraindicated as it will bring the heart rate down dangerously low. Your Calcium channel blocker Verapamil is correct it blocks calcium from causing contractions in the heart.

Mark

Mon, 01/18/2016 - 07:13

Dioxin is both a positive inotrope abdominal a negative chronotropic agent. Remember it slows heart rate down which is why you check it before administration. It also improves contraction (inotropic effect) by increasing ca in cells.

Angy

Sat, 10/15/2016 - 05:41

Elaborated well..!! (Y)

Madiha Qureshi

Thu, 12/24/2015 - 21:00

I like this presentation, but in the interest of accuracy, we normally spell propranolol with 2 r's in the U.S.. Is it not spelled that way in the U.K.?

Anonymous

Wed, 12/09/2015 - 20:33

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