Final answer:
Milrinone acts as a positive inotropic agent by increasing cAMP and thus raising intracellular Ca2+, which enhances heart muscle contractions and increases myocardial oxygen consumption. While arrhythmogenic, it is not related to thyroid hormones.
Step-by-step explanation:
Milrinone is a medication that works by causing an increase in intracellular cAMP, which in turn leads to a rise in intracellular calcium ions (Ca2+). This biochemical mechanism increases the strength of heart contractions through a process known as positive inotropy. Milrinone is not structurally related to thyroid hormones, though these hormones also increase cardiac rate and contractility by a different mechanism.
Arrhythmogenic effects refer to the potential of a drug to cause irregular heartbeats, which is one of the risks associated with milrinone use. Its action to increase contractility does indeed increase myocardial oxygen consumption, which is an important consideration in patients with heart conditions.
Positive inotropic agents like milrinone and digitalis enhance heart muscle contraction by either increasing calcium concentrations or inhibiting the sequestration of calcium ions.