Cardiac dysrhythmiawordf2014 (1) - Cardiac dysrhythmia(arrhythmia Irregular heart action caused by physiological or pathological disturbances in the

Cardiac dysrhythmiawordf2014 (1) - Cardiac...

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Cardiac dysrhythmia (arrhythmia):Irregular heart action caused by physiological or pathological disturbances in the discharge and transmission of impulses through the conductive tissue of the heartDepolarization:reversal of the electrochemical charges at the cell membrane in an excitable cell; this produces and electrical charge that will cause cardiac muscles to contractRepolarization: return of the electrochemical charges at the cell membrane to theresting polarized stateAbsolute refractory period:no transmission of electrochemical impulse is possibleRelative refractory period: abnormal transmission of electrochemical impulse occur; stressors/disease extend refractory periodsElectromechanical dissociation: electrochemical impulse does not produce muscle contraction; seen in severe cardiomyopathyAsystole: absence of electrical activity and contraction of the heartConductivity:the ability of the heart muscle to transmit of electrochemical impulse from one cell to another; some cells are more efficient conductors than others (increased conductivity)Automaticity: the unique ability of the heart muscle to initiate an electrochemicalimpulse without nervous stimulationPacemaker: specialized groups of cells that can initiate impulses; most cardiac cells can become pacemakerContractility: ability of muscle cells to contract
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Automatic pacemaker rates (potential ectopic sites)Atrial = 75AV node = 40-60Ventricles = 15=40SA node fires normally 60-100 bpmTachycardia: rapid beat (above 100 bpm)Bradycardia: slow beat (below 60 bpm)Sinus dysrhythmia: defect starts in SA nodeAtrial dysrhythmia: defect in starts in atriaNodal/Junctional dysrhythmia: defect starts in AV NodeVentricular dysrhythmia: defect in starts ventriclesFibrillation:rapid irregular electrical activity which results in quivering cardiac muscle and ineffective ejection of blood form the chamberBlock: failure of conduction of impulseFirst degree heart block:slow impulse from atria to ventriclesSecond degree heart block: not every impulse gets transmitted from atria to ventriclesThird degree (complete) heart block:atria and ventricles no longer communicate; each beats independentlyBundle branch block: slow or incomplete conduction through the Bundle of His in the ventriclesPremature beats (come early and are followed by compensatory pause)PAC (PAB) premature atrial contractions
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PVC (PVB) premature ventricular contractionsPAC’s have no P wave but QRS looks normalPVC’s have no P wave but QRS is wide and abnormalEpidemiology:Very common problem but seen more in older adult10% of people over 70 have A. FibSome very well tolerated and undiagnosedSome life threateningOver 1 million in USA have pacemakerRisk Factors:Damaged cardiac tissueHypoxiaElectrolyte disturbances (especially K+)Stimulants such as caffeine & cocaineEndocrine: hyperthyroidism, adrenalineFever, anxiety, pain
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