Inotropic: affecting the force of muscular contracations, especially of the heart.
β-blocking drugs have negative inotropic effects, whereas positive inotropic drugs increase
the strength of cardiac contractions, thereby increasing cardiac output. The short half life of
IV inotropes means that they must be given by continuous infusion.
Positive inotropic drugs
Positive inotropes strengthen the heart's contractions, so it can pump more blood with fewer heartbeats.
These agents are usually given to patients with cardiomyopathy
or congestive heart failure
they may be given to patients who have experienced recent myocardial
. In some cases, inotropes are given to patients with cardiogenic shock, such as after
cardiac surgeryr, where their hearts have been weakened.
Positive inotropes help the heart pump more blood with fewer heartbeats, so that, although the heart
beats less, it beats with more force.
For example, Digoxin strengthens the force of the heartbeat by increasing the amount of calcium in the
heart's cells, thus stimulating the heart to contract. When the Digoxin reaches the heart muscle, it
binds to sodium and potassium receptors, which control the amount of calcium in the heart muscle, by
stopping the calcium from leaving the cells. As calcium builds up in the cells, it causes a stronger
force of contraction.
Example positive inotropes...
Negative inotropic drugs
weaken the heart's contractions, and slow the heart rate. These agents are used to treat
hypertension, chronic congestive heart failure,
arrhythmias, and angina. They
are sometimes used to reduce stress on the heart, and prevent future heart attacks.
Negative inotrope types include beta-blockers, calcium channel blockers, and antiarrhythmic agents.
Beta-blockers "block" the effects of adrenaline on the body's beta receptors, thus slowing the nerve
impulses which travel through the heart. As a result, the heart does not have to work as hard, because it
needs less blood and oxygen. Beta-blockers also block the impulses which can cause an arrhythmia. Examples:
Atenolol, Metoprolol, Esmolol.
Calcium channel blockers slow the rate at which calcium passes into the heart muscle, and into the vessel
walls, which relaxes the vessels. These relaxed vessels let blood flow more easily through them, thereby
lowering blood pressure. Examples: Diltiazem, Nifedipine, Verapamil.
Antiarrhythmic agents slow the electrical conduction in the heart. Examples: Amiodarone, Flecainide.