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Physiology · Physiology concepts

Dromotropic effect

dromotropy

Dromotropic effect is a change in the conduction velocity of electrical excitation through the cardiac conduction system. This effect primarily manifests at the level of the internodal pathways (from the sinus node to the atrioventricular node) and the atrioventricular (AV) junction itself.

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Essence of the effectChange in the conduction velocity of the electrical impulse through the myocardium
Main targetAtrioventricular (AV) junction and internodal pathways
Extreme degreeDevelopment of atrioventricular block with severe suppression of conduction
2 min readFor medical studentsUpdated 09/24/2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesReviewed by medical editor: Aulov A. A., general practitioner · 09/24/2026

What is the dromotropic effect and its role in cardiac regulation?

Sympathetic and parasympathetic reflexes have a complex effect on the heart, which can be positive (+) or negative (-). The dromotropic effect is responsible for altering the velocity of excitation propagation.

Along with it, physiology distinguishes other regulatory effects:

  • Chronotropic effect — change in heart rate (HR).
  • Inotropic effect — change in contraction force.
  • Bathmotropic effect — change in myocardial excitability.
  • Tonotropic effect — change in myocardial tone.

How does the nervous system regulate conduction?

  • Sympathetic stimulation: Excitation of $\beta_1$-adrenergic receptors induces a positive dromotropic effect (accelerated conduction). Concurrently, myocardial contractility and heart rate increase.
  • Parasympathetic stimulation: Increased vagal influence (N. Vagus) and its cholinergic properties on the heart determine the negative dromotropic effect of acetylcholine. This leads to a significant decrease in the impulse propagation velocity through the conduction system, particularly at the AV node level.
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How do pharmacological agents alter conduction?

  • Non-selective adrenomimetics (e.g., orciprenaline): Stimulate $\beta_1$-receptors, exerting a positive dromotropic effect.
  • $\beta_1$-Adrenergic receptor blockers: Exert a direct inhibitory effect on the heart, causing a negative dromotropic effect, and also decrease the automaticity of ectopic pacemaker sites (AV node and Purkinje fibers).
  • Cardiac glycosides (digoxin): Inhibit conduction through the AV junction.
  • Antiarrhythmic drugs: Amiodarone inhibits AV conduction. Quinidine has a complex profile: its direct effect on cardiomyocytes decreases conduction, whereas its vagolytic (anticholinergic) action blunts vagal transmission, accelerating AV conduction and counteracting the direct effect.

What is the clinical significance of the effect?

Changes in conduction velocity are important for treating rhythm disorders:

  • Application of the positive effect: Improving conduction via $\beta_1$-stimulation is used in AV blocks and bradyarrhythmias.
  • Application of the negative effect: Slowing conduction is used in tachy-form atrial fibrillation. For example, digoxin causes incomplete conduction block, normalizing ventricular rate and converting the arrhythmia into a normosystolic form.
  • Hazards and overdose: Significant slowing of conduction through the AV node can lead to pathological atrioventricular block (up to complete block). In complete heart block due to high doses of digoxin, the ventricles switch to an autonomous (idioventricular) rhythm, with cardiomyocytes of the bundle of His acting as the pacemaker at a rate of 40–60 beats per minute.
How to memorize

To remember the localization of adrenergic receptors: $\beta_1$ stands for "Heart and kidneys" (stimulation produces a positive dromotropic effect), while $\beta_2$ stands for "Relaxation and metabolism".

Class and exam questions

What happens during an excessive negative dromotropic effect?

An atrioventricular block develops. In complete heart block, the ventricles may switch to an autonomous (idioventricular) rhythm generated by cardiomyocytes of the bundle of His at a rate of 40–60 beats per minute.

Which receptors are responsible for the positive dromotropic effect?

Stimulation of $\beta_1$-adrenergic receptors is responsible for accelerating conduction.

How does the vagus nerve affect conduction?

Increased vagal influence (N. Vagus) causes a negative dromotropic effect via the action of acetylcholine, significantly slowing impulse propagation in the AV node.

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What else to study on this topic

  • Chronotropic effect
  • Inotropic effect
  • Bathmotropic effect
  • Conduction system of the heart
  • Atrioventricular block

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