Cardiac Arrhythmias
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Rhythms are classified as normal or aberrant by viewing measurements of the heart’s electrical output.Ã?¯Ã?¿Ã?½ This is done using an E.K.G., or electrocardiogram.Ã?¯Ã?¿Ã?½ Electrodes placed on key areas of a person’s chest wall pick up and record the electrical activity of the heart onto a strip of paper.Ã?¯Ã?¿Ã?½ This activity appears as a series of spikes and dips.Ã?¯Ã?¿Ã?½ The heart’s rhythm is interpreted based on the nature and frequency of the spikes and dips seen.Ã?¯Ã?¿Ã?½ First, the heart rate, or number of beats per minute, is checked.Ã?¯Ã?¿Ã?½ Rates higher of lower than the normal adult rate of between 60 and 100 beats per minute (bpm) warrant further examination.Ã?¯Ã?¿Ã?½ In addition, the quality and timeliness of spikes and dips are studied.Ã?¯Ã?¿Ã?½ In order to interpret these images, it is important to understand what causes each to appear.
When the heart is beating as it should, it receives an electrical impulse to beat from the sinus node. This appears on the strip as a small bump, dubbed a “p” wave.Ã?¯Ã?¿Ã?½ Immediately after receiving this signal, the heart responds by contracting, producing a small dip followed by a tall, narrow spike, and ending with another small dip.Ã?¯Ã?¿Ã?½ This is called the “qrs” complex; the q and s representing the dips, and the r referring to the spike.Ã?¯Ã?¿Ã?½ Another small bump, called the “t” wave, appears at the end and is in response to repolarization of the heart, “during which time it cannot respond” (Thelan 392).Ã?¯Ã?¿Ã?½ Finally, the heart rests briefly and awaits the next signal, during which time a straight line appears on the graphed strip.Ã?¯Ã?¿Ã?½ As long as these elements are present and occur within a specific range, the heart rate is said to be normal.Ã?¯Ã?¿Ã?½ Measurements outside the normal range are diagnosed as arrhythmic.
SINUS RHYTHMS
Cardiac activity within the desired range is called normal sinus rhythm.�¯�¿�½ This is characterized by a rate of 60 to 100 bpm, a p wave before the qrs complex, a narrow qrs spike, and a resting phase between beats.�¯�¿�½ There are some variations to normal sinus rhythm, as listed below.
SINUS ARRHYTHMIA
The rate, presence, and quality of p waves and qrs complexes are all normal, but occur at slightly irregular intervals that are shown to correspond with inhalation and exhalation.�¯�¿�½ This arrhythmia is a type of normal rhythm seen in some individuals and is benign.�¯�¿�½ No treatment is required.
SINUS TACHYCARDIA
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The presence and quality of waves are normal and occur regularly; however the rate exceeds 100 bpm.Ã?¯Ã?¿Ã?½ This can be caused by exercise, illness, stress, certain drugs such as caffeine or amphetamines, or a number of ailments.Ã?¯Ã?¿Ã?½ Tachycardia can be dangerous if the rate increases greatly, as the heart cannot perfuse itself or the body efficiently when working this hard.Ã?¯Ã?¿Ã?½ The faster rate means shorter resting phase and less time for the squeezed muscle’s blood supply to refill.Ã?¯Ã?¿Ã?½ The heart is also more susceptible to having errant or ectopic beats evolve in this state, possibly establishing a more dangerous rhythm pattern in the process.Ã?¯Ã?¿Ã?½ Treatment involves rest, medications to slow the rate of the heart, avoidance of stress and tachycardia-inducing medications, and collateral treatment of any contributory illness.
SINUS BRADYCARDIA
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When the rhythm of the heart is regular and all waves are present and within normal parameters except a rate of less than 60 bpm, the rhythm is termed sinus bradycardia.�¯�¿�½ This can be seen among a person at rest and also is common among athletes, whose strong hearts are so efficient at pumping blood that a lower rate is sufficient.�¯�¿�½ However, this can also indicate that the heart is not pumping enough blood for proper circulation to the extremities or brain.�¯�¿�½ Fatigue, dizziness, and mental confusion due to poor oxygenation can occur, as well as lack of coordination.�¯�¿�½ Should the heart continue to slow, death is a possibility.�¯�¿�½ Medications to stimulate beating of the heart is a recommended course of action, and if the bradycardia is severe (consistently less than 40 bpm), the insertion of an implantable cardiac pacemaker may be necessary as well.
ECTOPIC BEATS
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Sometimes, an overall normal rhythm is occasionally interrupted by one or more ectopic, or aberrant, beats.�¯�¿�½ These beats are usually benign but can pose a risk of throwing the heart into a dangerous, life threatening rhythm.
PREMATURE ATRIAL CONTRACTIONS (PAC)
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PAC’s are seen on the graph as a wave that occurs earlier than normal, and is not followed by a qrs complex.Ã?¯Ã?¿Ã?½ It occurs when the atrium contracts prematurely.Ã?¯Ã?¿Ã?½ This is the least serious of the ectopic beats, as it rarely is sufficient to throw the whole rhythm off.
PREMATURE VENTRICULAR CONTRACTIONS (PVC)
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PVC’s indicate a premature contraction of the ventricles of the heart and is seen on a strip as an extra wave.Ã?¯Ã?¿Ã?½ Caffeine and stress can cause this, as can illness.Ã?¯Ã?¿Ã?½ While usually benign as the heart continues on or resets without responding to the contraction, because it originates in the ventricle it can lead to a dangerous ventricular tachycardia or fibrillation.Ã?¯Ã?¿Ã?½ Treatment involves medication and avoidance of stress, caffeine, and other drugs that could exacerbate the problem.
JUNCTIONAL ARRHYTHMIAS
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The impulse message for the heart to beat normally comes from the SA node in the atrial portion of the heart.Ã?¯Ã?¿Ã?½ When the atrium cannot produce a stimulus, the heart has a backup system. The junction between the atrium and ventricles will take over.Ã?¯Ã?¿Ã?½ Though not nearly as efficient as the sinus node, junctional rhythms “prevent asystole in the event of sinus node failure”.Ã?¯Ã?¿Ã?½ Without this reserve, the heart would stop functioning.Ã?¯Ã?¿Ã?½ Because the junction is not an effective manager of impulses, however, the presence of a junctional rhythm is an indication for immediate medical intervention in order to restore the origin of impulses to the atrium.
JUNCTIONAL ESCAPE RHYTHM
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Junctional rhythm is characterized as a regular bradycardic rhythm with a rate between 40 and 60 bpm.�¯�¿�½ P waves may be absent or appear inverted, and the pr interval is shortened (<0.12).�¯�¿�½ A common cause is digoxin toxicity; in this case, the medication must be withheld to reestablish sinus node function.�¯�¿�½ A pacemaker can be inserted as a precaution, as the junction cannot often sustain a rhythm indefinitely and may ultimately fail.
ACCELERATED JUNCTIONAL
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A junctional rhythm that has a rate of 60 to 100 bpm, but has the typical aberrant p wave characteristics. The higher rate makes this the more desirable form, though neither is benign.�¯�¿�½ Withholding depressive medication (digoxin) can help resolve the need for junctional stimulus.
VENTRICULAR ARRYTHMIAS
The most dangerous of rhythms, these forms of ectopy involve electrical activity initiating in the ventricles instead of the atrium.�¯�¿�½ Thus the ventricles are overworked and unable to eject blood efficiently and in a timely manner.�¯�¿�½ Lack of perfusion results.
VENTRICULAR TACHYCARDIA (VTACH)
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Often caused by some underlying disease, this rhythm is characterized by a heart rate of between 140 and 250 bpm, and an abnormally wide qrs complex. P waves may also be inverted.�¯�¿�½ Blood ejection from the heart is reduced due to rapid, erratic contractions of the ventricles which prevent proper filling of blood.�¯�¿�½ Symptoms from poor perfusion include weakness, dizziness, and syncope.
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If left untreated, ventricular tachycardia can cause a myocardial infarction (heart attack) or be life threatening.�¯�¿�½ Treatment is vital immediately, and includes
VENTRICULAR FIBRILLATION (VFIB)
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The most life threatening of all arrhythmias, ventricular fibrillation is an ineffective quivering of the ventricle’s musculature that is incompatible with sustaining life.Ã?¯Ã?¿Ã?½ On EKG, a series of small, wide hills will appear in place of the normal pqrst complexes.Ã?¯Ã?¿Ã?½ Severe myocardial infarction, drug toxicity, or accident such as electric shock or drowning can induce ventricular fibrillation.
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Immediate response by electrical cardio version/defibrillation, administered along with emergency advanced life support medications, is necessary to try and convert the rhythm and reestablish perfusion to the heart and organs, or death will occurs within minutes.
CONCLUSION
Cardiac rhythms, detectable through the use of electrocardiogram, are a measure of the electrical impulses traveling through the nodes and chambers of the heart which produce a muscular contraction in response.�¯�¿�½ A delayed or erratic impulse can cause contractions which are premature or ineffective, some of which can be immediately life threatening.�¯�¿�½ A return to normal electrical output can often be affected through the use of chemical or invasive means, including the use of medications such as Digoxin or Atropine; implantation of artificial pacemakers to induce electrical signal; or invasive shock via cardiac defibrillator.�¯�¿�½ These interventions are not interchangeable, but are each specific to varying types of arrhythmias.�¯�¿�½ Thus, the wrong treatment will prove ineffective or even harmful.�¯�¿�½ Thus, the use of electrocardiogram measurement of the p, qrs, and t wave intervals is essential to diagnose the type of arrhythmia before planning the appropriate form of treatment.
