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11 Cards in this Set
- Front
- Back
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Atrial fibrillation
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A common cardiac dysrhythmia involving atrial contractions that are so rapid that they prevent full repolarization of myocardial fibers between heartbeats.
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Automaticity
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A property of specialized excitable tissue that allows self-activation through the spontaneous development of an action potential, as in the pacemaker cells of the heart.
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Cardiac glycosides
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Glycosides (carbohydrates that yields a sugar and a nonsugar upon hydrolysis) that are derived from the plant species Digitalis purpurea and are used in the treatment of heart disease.
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Chronotropic drugs
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Drugs that influence the rate of the heartbeat. Positive chronotropic drugs increase the heart rate, whereas negative chronotropic drugs decrease it.
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Dromotropic drugs
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Drugs that influence the conduction of electrical impulses. Positive dromotropic drugs enhance the conduction of electrical impulses in the heart.
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Ejection fraction
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The proportion of blood that is ejected during each ventricular contraction compared with the total ventricular filling volume. It is an index of left ventricular function; the normal fraction is 65% (0.65).
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Heart failure
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An abnormal condition in which cardiac pumping is impaired as a result of myocardial infarction, ischemic heart disease, or cardiomyopathy. Failure of the ventricle to eject blood efficiently results in volume overload, chamber dilation, and elevated intracardiac pressure. The retrograde transmission of increased hydrostatic pressure from the left ventricle leads to pulmonary congestion; elevated right ventricular pressure leads to systemic venous congestion and peripheral edema.
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Inotropic drugs
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Drugs that influence the force or energy of muscular contractions, particularly contraction of the heart muscle. Positive inotropic drugs increase myocardial contractility.
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Left ventricular end-diastolic volume
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The total amount of blood in the ventricle immediately before it contracts, or the preload. Ventricular diastole begins with the onset of the second heart sound and ends with the onset of first heart sound.
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Refractory period
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The period during which a pulse generator (e.g., the sinoatrial node of the heart) is unresponsive to an input signal of specified amplitude and during which it is impossible for the myocardium to respond. This is the period during which the cardiac cell is readjusting its sodium and potassium levels and cannot be depolarized again.
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Therapeutic index
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The range of drug levels in the blood that is considered beneficial as opposed to toxic or ineffective.
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