FUNNY LOOKING BEATS

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FUNNY LOOKING BEATS

• CHAPTER 7

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ESCAPE BEATS

• ONE OR MORE EXTRA CARDIAC CYCLES ARE THE MOST
  COMMON ABNORMALITY IN AN EKG.
• CONDUCTION CELLS OUTSIDE THE SA NODE DEVELOP AN
  ABNORMALLY INCREASED AUTOMATICITY.
• THE SA NODE IS UNABLE TO SUPPRESS THE INCREASED
  AUTOMATICITY BY NORMAL OVERDRIVE SUPPRESSION.

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THE MOST AUTOMATIC CELL GENERATES A STIMULUS
WHICH CAUSES A CONTRACTION, AND THE CELL BECOMES
AN ABNORMAL PACEMAKER. INCREASED AUTOMATICITY
IS CONSIDERED CARDIAC IRRITIBILITY BECAUSE IT IS
UNDESIRABLE. THE EXTRA BEATS ARE UNDESIRABLE
BECAUSE THEY MAY NEGATIVELY AFFECT CARDIAC
OUTPUT. SA NODE SUPPRESSION CAUSING CARDIAC RATE
SLOWING IS ANOTHER CAUSE FOR EXTRA
BEATS. OVERDRIVE SUPPRESSION WEAKENS OR FAILS
BECAUSE THE SA NODE IS NO LONGER THE MOST
AUTOMATIC SITE IN THE CONDUCTION SYSTEM.
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THE AUTOMATICITY SITE IN THE CONDUCTION
SYSTEM MAY COMPETE TO OVERDRIVE THE FAILING SA
NODE AND CAUSE A CONDUCTED IMPULSE. AN ECTOPIC
FOCUS IS A SITE OF IMPULSE FORMATION LOCATED
SOMEWHERE OTHER THAN THE SA NODE. ECTOPIC BEATS
OR ECTOPY ARE EXTRA CONTRACTIONS IDENTIFIED BY
THE LOCATION OF THEIR FOCI. ADDITIONAL
NOMENCLATURE INDICATES THE PHYSICAL SITE OF THE
FOCUS, DEFINING THE CONTRACTION AS ATRIAL,
JUNCTIONAL, OR VENTRICULAR.
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PREMATURE ECTOPY

• ECTOPIC BEATS ARE CATAGORIZED BY THEIR TIMING IN
  THE EKG.
• PREMATURE BEATS OCCUR IN THE EKG BEFORE THE NEXT
  REGULAR BEAT CAN OCCUR.
• EXAMPLES PAC, PJC, PVC
• IDENTIFIABLE BY THEIR WAVES OF CONDUCTION
  RECORDED ON THE EKG.

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ESCAPE ECTOPY

• MAJOR FORM OF ECTOPY IS THE CONTRACTION WHICH
  OCCURS BECAUSE THE UNDERLYING RATE IS ABNORMALLY
  SLOW.
• THESE CONTRACTIONS ARE A COMPENSATORY MECHANISM
  OF THE HEART FOR BRADYDYSRHYTHMIA.

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THE SINUS RHYTHM IS DEPRESSED WITH A RATE SLOWER
THAN 60 BEATS. NORMAL AUTOMATICITY OF THE OTHER
CONDUCTION CELLS COMPETES WITH THE OVERDRIVE
SUPPRESSION OF THE SLOWED SINUS RHYTHM. ALLOWS
AN ECTOPIC FOCUS TO ESCAPE TO CAUSE
A CONTRACTION. ANY ECTOPICS IN BRADYCARDIC
RHYTHM ARE CLASSIFIED AS ESCAPE BEATS. ESCAPE
ECTOPY IS COMPENSATORY MECHANISM FOR A SLOW RATE.
PREMATURE ECTOPY INDICATES CARDIAC IRRITIBILITY.
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MANAGEMENT OF THE PATIENT MUST CONSIDER
THE UNDERLYING PATHOLOGY. ESCAPE ECTOPY IS
MANAGED BY ADDRESSING THE BRADYCARDIA. PREMATURE
ECTOPY IS MANAGED DIRECTLY WITH ANTIDYSRHYMIC
THERAPIES.
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PACS

• PACEMAKER STIMULUS.
• STIMULUS ARISES SOMEWHERE OTHER THAN THE SA NODE
  WITHIN THE TWO ATRIA.
• ANY PREMATURE COMPLEX WITH A P WAVE WITHIN NORMAL
  LIMITS IS A PAC.
• IF IT FAILS TO MEET THE CRITERIA IT IS CLASSIFIED
  AS ABERRANT PAC.

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ATRIAL ECTOPY IS COMMON. IT DOES NOT RULE OUT
THE PRESENCE OF SIGNIFICANT HEART DISEASE. MAY
CONTRIBUTE TO TACHYDYSRHYTHMIA. PATIENTS WITH
PACS FREQUENTLY REPORT A SENSATION OF
PALPITATIONS OR HAVING SKIPPED A BEAT.
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PJCS

• PACEMAKER STIMULUS ARISES FROM AN ECTOPIC FOCUS
  WITHIN THE JUNCTION.
• P WAVE CAN BE ABSENT, INVERTED, RETROGRADE.
• JUNCTIONAL CONTRACTIONS ARE MORE OMINIOUS AND
  SUGGEST UNDERLYING PATHOLOGY.

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PVCS

• ECTOPIC FOCUS WITHIN THE VENTRICLES.
• MOST OMINOUS OF ALL ECTOPIC BEATS.
• INDICATE INCREASED IRRITIBILITY.
• MAY BE TREATED WITH ANTIDYSRHYMIC MEDICATIONS.

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ABERRANT COMPLEXES

• ONE VENTRICLE REPOLARIZES AT A SLOWER RATE THAN
  THE OTHER.
• ONE VENTRICLE IS THEN ABLE TO ACCEPT AN
  ELECTRICAL IMPULSE CAUSING DEPOLARIZATION EARLIER
  THAN THE OTHER VENTRICLE.
• INDIVIDUAL COMPLEXES THAT APPEAR DIFFERENT THAN
  THE COMPLEXES OF THE UNDERLYING RHYTHM.

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THE ABERRANT COMPLEXES BECAUSE THEY DO NOT
FOLLOW THE SAME ELECTRICAL CONDUCTION PATHWAY. A
BERRANTLY CONDUCTED COMPLEXES INCLUDE
AN ABERRANTLY CONDUCTED COMPLEX THAT HAS A
NEGATIVE QRS WHEN THE UNDERLYING RHYTHM HAS A
POSITIVE QRS COMPLEX. THE QRS OF THE ABERRANTLY
CONDUCTED COMPLEX IS WIDER OR SHORTER THAN THE
COMPLEXES OF THE UNDERLYING RHYTHM.
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ABERRANTLY CONDUCTED COMPLEXES CAN ORIGINATE FROM
ANYWHERE IN THE ATRIA, AV JUNCTION, OR
VENTRICLES. THE ORIGIN WILL DETERMINE THE SIZE
AND SHAPE. USUALLY OCCUR AS INDIVIDUAL
COMPLEXES, NOT ENTIRE RHYTHMS.
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PULSELESS ELECTRICAL ACTIVITY

• DYSRHYTHMIA WITHOUT CONTRACTION OF THE
  MYOCARDIUM.
• DEPOLARIZATION SEEMS TO OCCUR BUT NO PULSE OR
  B/P.
• LETHAL AND TREATMENT MUST BEGIN IMMEDIATELY.

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MAY BE CAUSED BY HYPOVOLEMIA, HYPOXIA,
CARDIAC TAMPONADE OR TENSION PNEUMOTHORAX. PEA
MAY OCCUR IF THE MYOCARDIUM IS SO DAMAGED IT
CANNOT CONTRACT, ALTHOUGH ELECTRICAL IMPULSES ARE
BEING CONDUCTED BY THE ELECTRICAL CONDUCTION
PATHWAYS.
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TEMPORARY PACEMAKERS

• USED TO MAINTAIN HEART RATE IN AN EMERGENCY
  SITUATION OR UNTIL A PERMANENT PACEMAKER CAN BE
  SURGICALLY IMPLANTED.
• TWO TYPES OF TEMPORARY PACEMAKERS.

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TRANSVENOUS (THROUGH A VEIN). THE LEADWIRE IS
INSERTED THROUGH THE SKIN AND THREADED THROUGH A
LARGE VEIN INTO THE RIGHT SIDE OF THE
HEART. ELECTRICAL IMPULSES STIMULATE THE ATRIUM
AND THE IMPULSES ARE CARRIED THROUGH THE CARDIAC
ELECTRICAL CONDUCTION SYSTEM, CAUSING
DEPOLARIZATION. TRANSDERMAL OR TRANSCUTANEOUS
(THROUGH THE SKIN). TWO LARGE PADS AS ELECTRODES
CONDUCT THE IMPULSE.
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TWO LEADWIRES EACH CONNECTED TO A PAD. ONE PAD
ON THE FRONT AND ONE PAD ON THE BACK. THE
IMPULSES ARE THEN CONDUCTED THROUGH THE BODY AND
HEART STIMULATING THE ENTIRE HEART CAUSING
DEPOLARIZATION. TRANSDERMAL IS EASILY POSITIONED
AND DOES NOT REQUIRE PIERCING THE PATIENTS SKIN
TO POSITION THE ELECTRODES. FIXED PACEMAKER
GENERATES A CONSTANT RATE, 72 TO 80
IMPULSES. DEMAND SET TO GENERATE IMPULSES ONLY
WHEN THE PATIENTS RATE FALLS BELOW A
PREDETERMINED RATE.
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PERMANENT PACEMAKERS

• NECESSARY WHEN THE PATIENT IS UNABLE TO MAINTAIN
  A NORMAL HEART RATE OR CARDIAC OUTPUT, EVEN WITH
  AID OF MEDICATIONS.
• GENERATOR IS SURGICALLY IMPLANTED UNDER THE
  PATIENTS SKIN.
• USUALLY UNDER THE UPPER LEFT CHEST SKIN OR
  ABDOMINAL AREA.

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ATRIAL PACEMAKER

• LEADWIRE AND ELECTRODE ARE INSERTED INTO THE
  RIGHT ATRIUM.
• THE IMPULSE STIMULATES THE ATRIA, THEN FOLLOWS
  THE NORMAL ELECTRICAL PATHWAY.
• THE DISCHARGE IS REPRESENTED BY A VERTICAL LINE
  CALLED A PACER SPIKE.
• THE SPIKE IS USUALLY FOLLOWED BY A P WAVE AND QRS.

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THE P WAVE MAY NOT BE SEEN UNLESS THE ELECTRODE
IS POSITIONED HIGH IN THE RIGHT ATRIUM. THE P
WAVE FOLLOWING A PACER SPIKE IS USUALLY NOT
MEASURED. ATRIAL PACEMAKER CAN ONLY BE USED IF
THE AV JUNCTION AND VENTRICULAR CONDUCTION
PATHWAYS ARE FUNCTIONING. RARELY USED TODAY
BECAUSE THEY ARE LESS EFFICIENT THAN VENTRICULAR
OR SEQUENTIAL PACEMAKERS.
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VENTRICULAR PACEMAKERS

• THE LEADWIRE AND ELECTRODE ARE PLACED IN THE
  RIGHT VENTRICLE.
• CAUSES DEPOLARIZATION OF THE VENTRICULAR MUSCLE.
• THE ATRIA MAY NOT DEPOLARIZE IF THE ATRIAL
  MYOCARDIUM IS EXTENSIVELY DAMAGED.
• A PACER SPIKE FOLLOWS THE QRS.
• THE QRS IS USUALLY GREATER THAN 0.12 SECONDS.

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SEQUENTIAL PACEMAKERS

• COMMONLY USED.
• STIMULATES THE DEPOLARIZATION OF BOTH THE ATRIA
  AND VENTRICLES.
• THE LEADWIRE HAS TWO ELECTRODES ONE IN THE
  ATRIA AND ONE IN THE VENTRICLE.

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THE RHYTHM STRIP USUALLY SHOWS TWO PACER SPIKES
BEFORE EACH QRS COMPLEX. SPIKES MAY OCCUR
CLOSELY TOGETHER THAT THEY APPEAR AS ONE LONG
SPIKE. FIRST SPIKE REPRESENTS THE ATRIA FIRING,
THE SECOND REPRESENTS THE VENTRICLE FIRING. P
WAVE MAY BE SEEN, AND QRS IS GREATER THAN 0.12
SECONDS.
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CAPTURE AND PACING

• THE PERCENTAGE OF CAPTURE AND PACING MUST BE
  DETERMINED.
• CAPTURE REFERS TO THE CARDIAC MUSCLES ABILITY TO
  CONDUCT THE ELECTRICAL IMPULSE GENERATED BY A
  MECHANICAL PACEMAKER.
• P WAVE OR QRS COMPLEX FOLLOWING EVERY PACER SPIKE.

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THE PRESENCE OF A COMPLEX FOLLOWING A PACER SPIKE
DOES NOT ALWAYS INDICATE THE CONTRACTION OF THE
MYOCARDIUM, ONLY THE CONDUCTION OF AN ELECTRICAL
IMPULSE. THE PATIENT MUST BE ASSESSED. PERCENTAG
E OF CAPTURE IS DETERMINED BY THE NUMBER OF PACER
SPIKES FOLLOWED BY A COMPLEX IN RELATIONSHIP TO
THE TOTAL NUMBER OF PACER SPIKES ON THE ENTIRE
STRIP. LOSS OF CAPTURE A QRS DOES NOT FOLLOW A
PACER SPIKE.
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LOSS OF CAPTURE INDICATES THE ELECTRICAL IMPULSE
GENERATED BY THE MECHANICAL PACEMAKER HAS NOT
BEEN CONDUCTED. MAY INDICATE THE MYOCARDIUM IS
SO DAMAGED, IT IS UNABLE TO RESPOND TO EVERY
ELECTRICAL IMPULSE. PACING REFERS TO THE
PERCENTAGE OF COMPLEXES GENERATED BY THE
MECHANICAL PACEMAKER. THE PERCENTAGE OF PACING
DEPENDS ON THE PACEMAKER ABILITY OF THE
PATIENTS OWN HEART THE PERCENTAGE OF CAPTURE
SHOULD ALWAYS BE 100.
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AICDS

• AUTOMATIC IMPLANTABLE CARDIOVERTER DEFIBRILLATORS
• CAN IDENTIFY AND TREAT SOME RAPID LETHAL
  DYSRHYTHMIAS.
• SURGICALLY IMPLANTED.
• CAN BE PROGRAMMED TO INITIATE LOW-VOLTAGE
  ELECTRICAL IMPULSES WHEN THE HEART RATE BECOMES
  VERY FAST.

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THE AICD IMPULSE ATTEMPTS TO FORCE THE HEART INTO
A NORMAL RATE. IF THE HEART RATE CONTINUES TO
INCREASE, OR IF THE RHYTHM BECOMES V-FIB OR
V-TACH, THE AICD WILL DELIVER A SHOCK STRONG
ENOUGH TO DEFIBRILLATE. THE AICD WILL
DEFIBRILLATE THE PATIENT UNTIL THE HEART HAS
RECOVERED OR UNTIL IT IS TURNED OFF BY MEDICAL
PERSONNEL. ON THE RHYTHM STRIP, THE FIRING OF
THE AICD APPEARS SIMILAR TO A PACING SPIKE, BUT
MAY HAVE A GREATER AMPLITUDE.