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.

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.

Positive inotropic agents include dopamine, isoprenaline, etc. Negative inotropic agents include beta blockers, quinidine, flecainide, etc. Positive inotropes are also known as sympathiomimetic drugs. Inotropes are used to treat impaired cardiac contractility.

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 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.

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

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 -  slows 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 fibre 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...

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

Wow, clear and nice.

well explained, thanks

Really helpful, thank you.

A very satisfying clarification simple and to the point!

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.

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.

Elaborated well..!! (Y)

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.?

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