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The choice of agent depends largely on specific pharmacological effects of individual agents with respect to the condition. One of the most important factors affecting inotropic state is the level of calcium in the cytoplasm of the muscle cell. Positive inotropes usually increase this level, while negative inotropes decrease it.
Cardiotonic agents, also known as cardiac inotropes or stimulants, have a positive impact on the myocardium (muscular layer of the heart) by enhancing its contractility. . Unlike general inotropes, these agents exhibit a higher level of specificity as they selectively target the myocar
Medications used include: diuretic agents, vasodilator agents, positive inotropes, ACE inhibitors, beta blockers, and aldosterone antagonists (e.g., spironolactone). Some medications which increase heart function, such as the positive inotrope milrinone, lead to increased death, and are contraindicated. [9] [10]
Drugs that positively render the effects of catecholamines such as norepinephrine and epinephrine that enhance contractility are considered to have a positive inotropic effect. The ancient herbal remedy digitalis appears to have both inotropic and chronotropic properties that have been recorded encyclopedically for centuries and it remains ...
Pharmacologic treatment with negative inotropic drugs is first-line therapy. Beta-blockers are used first, and while they improve symptoms of shortness of breath, chest pain and exercise intolerance, they do not reduce resting LV intraventricular pressure gradients and often are inadequate to control symptoms.
Isoprenaline has positive inotropic and chronotropic effects on the heart. β 2-Adrenergic receptor stimulation in arteriolar smooth muscle induces vasodilation. Its inotropic and chronotropic effects elevate systolic blood pressure , while its vasodilatory effects tend to lower diastolic blood pressure.
Both inotropic and lusitropic effects justify the use of amrinone to treat heart failure. Amrinone decreases the pulmonary capillary wedge pressure while increasing cardiac output, as it functions as an arterial vasodilator and increases venous capacitance while decreasing venous return. [ 5 ]
Epinephrine (adrenaline). Activation of β 1 receptors induces positive inotropic, chronotropic output of the cardiac muscle, leading to increased heart rate and blood pressure, secretion of ghrelin from the stomach, and renin release from the kidneys.