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What is Milrinone and explain in detail?
Milrinone, sold under the brand name Primacor, is a pulmonary vasodilator used in patients who have heart failure.   It is a phosphodiesterase 3 inhibitor that works to increase the hearts contractility and decrease pulmonary vascular resistance. Milrinone also works to vasodilate which helps alleviate increased pressures (afterload) on the heart, thus improving its pumping action.  While it has been used in people with heart failure for many years, studies suggest that milrinone may exhibit some negative side effects that have caused some debate about its use clinically.Overall, milrinone supports ventricular functioning of the heart by decreasing the degradation of cyclic adenosine monophosphate (cAMP) and thus increasing phosphorylation levels of many components in the heart that contribute to contractility and heart rate. Milrinone is used as a drug that causes positive inotropy and it will lead to an increased force of contraction. Milrinone use following cardiac surgery has been under some debate because of the potential increase risk of postoperative atrial arrhythmias.  However,  in the short term milrinone has been deemed beneficial to those experiencing heart failure and an effective therapy to maintain heart function following cardiac surgeries. There is no evidence of any long term beneficial effects on survival. In critically ill patients with evidence of cardiac dysfunction there is limited good quality evidence to recommend its use.Milrinone is administered IV only and eliminated unchanged in the urine. Dose adjustment is required for patients with renal impairment.

Contractility in the heart
People experiencing some forms of heart failure have a significant decrease in the contractile ability of muscle cells in the heart (cardiomyocytes). This impaired contractility occurs through a number of mechanisms. Some of the main problems associated with decreased contractility in those with heart failure are issues arising from imbalances in the concentration of calcium. Calcium permits myosin and actin to interact which allows initiation of contraction within the cardiomyocytes. In those with heart failure there may be a decreased amount of calcium within the cardiomyocytes reducing the available calcium to initiate contraction. When contractility is decreased the amount of blood being pumped out of the heart into circulation is decreased as well. This reduction in cardiac output can cause many systemic implications such as fatigue, syncope and other issues associated with decreased blood flow to peripheral tissues.

Mechanism of action
cAMP causes increased activation of protein kinase A (PKA). PKA is an enzyme that phosphorylates many elements of the contractile machinery within the heart cell. In the short term this leads to an increased force of contraction. Phosphodiesterases are enzymes responsible for the breakdown of cAMP