Click to edit Master subtitle style 3 / 1 9 / 1 2 Dysrhythmias • conditions in which there is abnormal electrical activity in the heart. The heart beat may be too fast or too slow, and may be regular or irregular. • These are due to abnormal automaticity, abnormal conduction or both. • Some dysrhythmias are life-threatening and can result to cardiac arrest and death. • The most common complication and most major cause of death among clients with MI. • Diagnosed by analyzing electrocardiographic wave form • Name according to the site of origin of the impulse and mechanism of formation or conduction involved
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Cardiac Dysrhythmias results fromdisturbances in three major mechanisms:
1. Automaticity – the normal processes of generating a heart rhythm. This process of automatically initiating an impulse can be altered if the normal pacemaker cells are firing too rapidly, or if an impulse isgenerated by a cell that normally does not initiate heartbeats, calledan ectopic pacemaker.
2. Conduction – the impulse travels through the sinus node, AV node,and Purkinje fibers. Latent pacemaker cells can also fire at ratesabove or below their inherent rate. A rhythm slower than theintrinsic rate is called bradycardia. A rhythm faster than the intrinsicrate is called accelerated or tachycardia.
3. Reentry of Impulses - occurs when cardiac tissue is depolarizedmultiple times by the same impulse, and when two pathways arepresent: “slow” and “fast” pathway. Two pathways can develop fromanatomic abnormalities (accessory pathway, fibrosis) or functionaldefects (ischemia, drug interactions). Reentry can result frommyocardial ischemia, the action of antidysrhythmic medications,myocardial fibrosis, existence of an accessory pathway, or bundle-branch block.
ischemia occurs when living tissue is deprived of oxygen.
In the human body, oxygen supply to tissue is accomplishedprimarily by supplying the tissue with a continuous flow of oxygenated blood. Anything which interrupts or decreases theflow of blood thus causes ischemia.
Ischemia causes rapid damage to tissue of all types, thoughsome tissues are more sensitive than others.
ischemia in the heart leads to a heart attack (also known as amyocardial infarction).
Hypoxemia
occurs when there is a low level of oxygen in the blood.Hypoxemia may be manifested by changes in mental status,shortness of breath, increase in blood pressure, changes inheart rate, dysrhythmias, cyanosis (late sign, diaphoresis) andcool extremities. Hypoxemia often leads to hypoxia, which is adecrease of oxygen to the tissues of the body.
Hemodynamic abnormalitiesHemodynamics - blood pressure and blood flow paired
values at different nodes of the cardiovascular system.
Hypertension and congestive heart failure are two bestknown systemic hemodynamic disorders.
SNS and PNS influencesSympathetic Nervous System: The sympathetic system
controls the body’s response to emergencies. When this
system is aroused, a number of things begin to occur: yourheart and breathing rates increase, digestion slows or stops,the pupils dilate and you begin to sweat. Known as the fight-or-flight response, this system responds by preparing your bodyto either fight the danger or flee.
Parasympathetic Nervous System: The parasympathetic
nervous system functions to counter the sympathetic system.After a crisis or danger has passed, this system helps to calmthe body. Heart and breathing rates slow, digestion resumes,pupil contract and sweating ceases.
due to the buildup of lactic acid in the body. Lactic acidosis occurswhen cells make lactic acid (from glucose) faster than it can bemetabolized. The key signs of lactic acidosis include unusually deep
and rapid breathing, vomiting, and abdominal pain. Muscle glycogen is one of the main energy sources for exercise. In
order to be utilized, stored muscle glycogen must be broken down intoglucose, a process known as glycolysis. During glycolysis, eachglucose molecule is cleaved into two pyruvic acid molecules, andenergy is released to form adenosine triphosphate (ATP). Normally, thepyruvic acid enters the mitochondria (the principal cell sites whereenergy is generated) and undergoes the oxidative stage of glycolysisto produce yet more ATP. However, when there is not enough oxygenpresent for this reaction to take place, the pyruvic acid transforms intolactic acid. From this point, lactic acid can diffuse out of the muscle cellinto the blood. It is by this process (known as anaerobic glycolysis) thatmuscle glycogen can be converted into energy without the presence of
oxygen as opposed to ATP production via aerobic glycolysis. Such aconversion allows glycolysis to proceed for minutes, when it couldotherwise last only seconds. Thus, energy is supplied to promotesurvival in stressful times.
Drug toxicity A person with drug toxicity has accumulated too much of a medication
in the bloodstream. The effects of the medication are more pronouncedat toxic levels, and side effects may be severe. Toxicity may result
when the dose is too high, or it may result when the liver or kidneysare unable to remove the drug from the bloodstream. Many commonlyprescribed medications can accumulate in the bloodstream and resultin toxicity.
Symptoms of drug toxicity depends on the drug taken. Symptoms drugtoxicity can be broken down into: symptoms of gamma-Hydroxybutyric
acid (depressant), symptoms of hallucinogens, symptoms of narcotics,symptoms or sedatives, and symptoms of stimulants.
Electrolyte Imbalances Electrolytes are heavy metals, also known as salts, and are important
for body chemistry to function correctly. Calcium, sodium andpotassium are the most important electrolytes.
Calcium and potassium have to be in balance -- sitting on either side of cell membranes, ready to switch places -- in order to cause muscles tocontract or nerves to transmit impulses. Once calcium and potassiumswap places and cause things to happen, sodium puts them back intheir place for the next time.
If there aren't enough of one or all of these electrolytes, then the heartmuscle cells can't move, which means the heart won't pump.
Ø Sinus arrythmia - the physiologic cyclic variation in heartrate, originating in the sinoatrial node and related to vagalimpulses to the node; it occurs commonly in children and inthe aged.
Atrial dysrhythmias - begin in the upper chambers of the heart.
Ø Premature atrial complex (PAC) - premature heartbeatsoriginating in the atria. May be the result of atrial enlargement orischemia or may be caused by stress, caffeine, or nicotine.
Treatment:
ü Quinidine and Procainamide can be given to patient thathaving a frequent PACs to slow the heart rate.
Ø Atrial flutter – atrial contractions are rapid (230-80 per minute),but regular.
§ Types:o Type I – atrial rate is usually 290 – 310 per minute but can
range from 230 – 350.o Type II – atrial rate is usually 360 – 380 per minute but can
ü Diltiazem, Beta-blockers, Digitalis (to slow the conduction of AVnode)
ü Cardioversion – elective procedure, activation of electricimpulse, countershock.
Ø Atrial fibrillation - a very common irregular rhythm, starts in theupper parts (atria) of the heart. A disorder of the heart beatassociated with a higher risk of stroke. In this disorder, the upper
chambers (atria) of the heart do not completely empty when theheart beats, which can allow blood clots to form.Symptoms:
o Feeling dizzy or lightheadedo Feeling weak and tired, palpitations, chest pain (angina).
syncope (fainting).
Treatment:ü You might take an anticoagulant, such as warfarin, or an
antiplatelet, such as aspirin to prevent stroke.
ü Rhythm-control medicines (antiarrhythmics) help return the heartto its normal rhythm and keep it there.
Ventricular dysrhythmias - begin in the lowerchambers of the heart.
Ø Premature ventricular contraction (PVC) - "skippedbeat" or felt as palpitations in the chest. In a normal
heartbeat, the ventricles contract after the atria have helpedto fill them by contracting; in this way the ventricles canpump a maximized amount of blood both to the lungs and tothe rest of the body. In a PVC, the ventricles contract first,which means that circulation is inefficient.
Symptoms:
o Dizziness,o lightheadednesso fainting
Treatment:
ü Beta blockers (drugs that block the effect of adrenaline)reduce arrhythmias.
ü Eliminating caffeine intake, as well as tobacco and alcoholusage, may reduce the frequency of PVCs
Ø Ventricular tachycardia - a rapid heart beat that originatesin one of the lower chambers (the ventricles) of the heart. Tobe classified as tachycardia, the heart rate is usually at least
100 beats per minute.Symptoms:
Sustained ventricular tachycardia prevents the ventricles fromfilling adequately so the heart can not pump normally. This results inloss of blood pressure, and can lead to a loss of consciousness andto heart failure.
Treatment:
ü Acute episodes of sustained (that is, prolonged) ventriculartachycardia are often medical emergencies. If a cardiacarrest has occurred, then standard cardiopulmonaryresuscitation (CPR) measures must be taken immediately.
ü Arrhythmia can often be terminated by deliveringintravenous medications, such as lidocaine.
ü Or the patient can be sedated and given an electrical shockto stop the arrhythmia, a procedure referred to as"cardioversion."
Ø Ventricular fibrillation (VF) - is an extremely dangerousform of cardiac arrhythmia, which invariably causes asudden cardiac arrest. VF occurs when the electrical impulsein the ventricles - the main pumping chambers of the heart -
suddenly becomes disrupted. The loss of an organizedelectrical signal causes the ventricles to immediately stopbeating, which causes the circulation to collapse. Unless thecirculation is restored, loss of consciousness usually occurswithin 10 seconds, and death within 5 to 10 minutes.
Treatment:
VF is a medical emergency. It always produces a sudden cardiacarrest, which will lead to death within a few minutes unless effectivetreatment is delivered - which means immediate cardiopulmonaryresuscitation (CPR) followed, as quickly as possible, by defibrillation.
Prevention:
The very best way to prevent VF, and to keep your risk of suddencardiac death as low as possible, is to avoid developing heart diseasein the first place. You should make every attempt to maintain goodcardiac health by keeping your cardiac risk factors under control