Chronotropic effects (from chrono-, meaning time, and tropos, "a turn") are those that change the heart rate.
Chronotropic drugs may change the heart rate and cardiac cycle by affecting the electrical conduction system of the heart and the nerves that influence it, such as by changing the sinus rhythm the sinoatrial node. Positive chronotropes increase heart rate; negative chronotropes decrease heart rate.
A dromotropic affects atrioventricular node (AV node) conduction. A positive dromotrope increases AV nodal conduction, and a negative dromotrope decreases AV nodal conduction. A Lusitropy is an agent that affects diastolic relaxation.
Many positive affect preload and afterload.
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