2 ObjectivesTo recognize the normal rhythm of the heart - “Normal Sinus Rhythm.”To recognize the most common rhythm disturbances.To identify emergency interventions for life threatening arrhythmias
3 I. Impulse Conduction & the ECG Sinoatrial nodeAV nodeBundle of HisBundle BranchesPurkinje fibers
4 1. The “PQRST”- Reminder-the EKG only reflects the heart’s electrical activity-not its contraction P wave - Atrial depolarizationQRS - Ventricular depolarizationT wave - Ventricular repolarization
5 Atrial depolarization + 2. The PR IntervalAtrial depolarization +delay in AV junction(AV node/Bundle of His)(delay allows time for the atria to contract before the ventricles contract) normal time 0.12 to 0.20 sec.
6 3. Pacemakers of the Heart SA Node - Dominant pacemaker with an intrinsic rate of beats/minute.AV Node - Back-up pacemaker with an intrinsic rate of beats/minute.Ventricular cells - Back-up pacemaker with an intrinsic rate of beats/minute.
7 4. The ECG Paper Horizontally Vertically One small box - 0.04 s One large box sVerticallyOne large box mV
8 4. The ECG Paper (cont)3 sec3 secEvery 3 seconds (15 large boxes) is marked by a vertical line (hash mark).This helps when calculating the heart rate.You need a 6 second strip to calculate heart rate (30 large boxes)
9 4. The ECG Paper (cont) 3 sec 3 sec Count the number of P waves in a 6 second strip (30 large boxes) and multiply by 10 to determine atrial rate(9 x 10 = 90) Atrial rate = 90 beats/minCount the number of QRS complexes in a 6 second strip (30 large boxes) and multiply by 10 to determine ventricular rate(9 x 10 =90) Ventricular rate + 90 beats/min
10 Normal Sinus Rhythm (NSR) Normal Rhythm of Heart--etiology Etiology: the electrical impulse is formed in the SA node and conducted normally.This is the normal rhythm of the heart; other rhythms that do not conduct via the typical pathway are called arrhythmias.
11 Normal Sinus Rhythm (NSR) Characteristics Rate – 60 to 100Regularity – rhythm is regularP waves – one P wave preceding each QRSPR interval – normal between 0.12 and 0.20 seconds and constant in lengthQRS – all look the sameQRS duration – equal to or less than 0.12 seconds and constant in widthQT interval – equal to or less than 0.44 seconds and constant in length
12 SA Node Problems defined The SA Node can:fire too slow fire too fast Sinus BradycardiaSinus Tachycardia
13 A. Sinus Bradycardia Rate less than 60 beats per minute--etiology Etiology: SA node is depolarizing slower than normal, impulse is conducted normally (i.e. normal PR and QRS interval).Significance: Lower rate may cause decrease in cardiac output
14 A. Sinus Bradycardia-- Characteristics Rate: less than 60 beats per minuteRegularity: rhythm is regularP wave: normal; one precedes each QRSPR interval: normal between 0.12 and 0.20 secondsQRS: normal, equal to or less than 0.12 secondsQT: normal or may be prolonged
15 A. Sinus Bradycardia Signs and Symptoms due to Sinus Bradycardia May have no symptoms at allMay have signs of decreased cardiac output- hypotension, cool clammy skin,- shortness of breath, chest pain or pressure- light headed, dizziness or blurred vision- syncope
16 A. Sinus Bradycardia Treatment for Sinus Bradycardia Treat only if symptomatic- IV atropine- IV dopamine- Transcutaneous pacemaker
17 B. Sinus Tachycardia--etiology Rate greater than 100 beats per minute but less than 150 beats per minuteEtiology: SA node is depolarizing faster than normal, impulse is conducted normally.Significance: increased workload of the heartRemember: sinus tachycardia is a response to physical or psychological stress, (hypoxia, pain, hypovolemia).
18 B. Sinus Tachycardia-characteristics Rate greater than 100 beats per minute but less than 150 beats per minuteRate: 100 beats per minute but less than 150 beats per minute.Regularity: rhythm is regularP wave: normal, one precedes each QRSPR interval: normal between 0.12 and 0.20 secondsQRS: normal, equal to or less than 0.12 secondsQT: normal
19 B. Sinus Tachycardia Signs and Symptoms May have no symptoms at allMay have signs of decreased cardiac output- hypotension, syncope and blurred vision- chest pain and/or palpitations- may report a sense of nervousness or anxiety
20 B. Sinus Tachycardia Treatment Look for the cause (ie. pain, anxiety, fever, hemorrhage) and treat the cause.If tachycardia leads to cardiac ischemia treatment may include medications to slow the heart rateBeta blockers orCalcium channel blockers
21 III. Atrial Arrhythmias Atrial tissueSingle or Multiple irritable areas can depolarize and “take over” from the SA node.
22 A. Atrial Fibrillation etiology Etiology: Atrial impulses are formed in a totally unpredictable fashion-there are no p waves.Significance:The atria do not contract in a coordinated way therefore, the cardiac output is decreased.The atria do not empty fully, so there is a risk of atrial clotsThe AV node allows some of the impulses to pass through at variable intervals (so rhythm is irregularly irregular). Rates can get dangerously high
23 A. Atrial Fibrillation characteristics Rate:Atrial rate: not measurable exceeds 400 beats per minute.Ventricular rate: 30 to 220 beats per minuteRegularity: grossly irregularP waves: absent; erratic baselinePR interval: not measurableQRS: normal QT: not measurable
24 A. Atrial Fibrillation Signs and symptoms Patients with chronic atrial fibrillation may be asymptomaticNew onset atrial fibrillation patients may have symptoms related to decreased cardiac output (loss of atrial contraction and fast ventricular rate)hypotension, cool clammy skin,shortness of breath, chest pressure or pain,dizziness, blurred vision or syncope
25 A. Atrial Fibrillation treatment If treatment is required:Beta Blocker, Calcium Channel blockers will decrease rateIV Amiodarone may decrease rate and convert rhythm (NOT IV bolus!)Synchronized Cardioversion will convert the rhythm
26 B. Atrial Flutter Deviation from NSR No P waves. Instead flutter waves (note “sawtooth” pattern) are formed at a rate of per minuteOnly some impulses conduct through the AV nodeSignificance & treatment -as in Atrial Fibrillation
27 Supra Ventricular Tachycardia (SVT) Atrial Tachycardia Deviation from NSRHeart rate: speeds up to greater than 150 beats per minuteRhythm: regular, with normal QRS complexes.Significance:Greatly increased myocardial oxygen demandCould become life threatening
28 C. SVT – Signs and symptoms Patient may be asymptomaticMay have signs of decreased cardiac output:Hypotension, cool clammy skin,shortness of breath, chest pain or pressure,dizziness, blurred vision or syncopeReview the key characteristics of PSVT.
29 C. SVT Treatment Treatment: Adenosine followed by Beta Blocker or Calcium Channel BlockerSynchronized Cardioversion in emergencyReview the key characteristics of PSVT.
30 IV. Ventricular Cell Problems Ventricular cells can:fire occasionally from 1 or more irritable areafire continuously from multiple irritable areasfire continuously from a single irritable areaPremature Ventricular Contractions (PVCs)Ventricular FibrillationVentricular Tachycardia(VT)
31 IV. Ventricular beats When an impulse originates in a ventricle: conduction through the ventricles will be abnormalQRS will be wide (greater than 0.12 seconds) and bizarre.Multi-focal PVCs
32 IV. Ventricular Conduction AbnormalSignal moves slowly through the ventricles result is a wide QRSNormalSignal moves rapidly through the ventricles
33 A. PVCs--characteristics Deviation from NSREarly beats originate in the ventricles resulting in wide (greater than 0.12 sec.) and bizarre QRS complexes.When there is more than one premature beat, and the beats look alike, they are called “unifocal”.When there is more than one premature beat, and the beats look different, they are called “multifocal”.
34 A. PVCs etiologyEtiology: Ventricular irritability can be caused by hypoxia, electrolyte imbalances.Significance: Early beats from the ventricle do not deliver full cardiac output; if untreated may lead to VT/VF.
35 B. Ventricular Tachycardia Deviation from NSR:Impulse is originating in the ventricles (no P waves, wide QRS, rate greater than 100).Significance:greatly reduced cardiac output--Life threatening arrhythmia!!Treatment:IV Lidocaine or IV Amiodarone (NOT IV bolus)
36 C. Ventricular Fibrillation Etiology: Hundreds of ventricular cells are excitable and depolarizing randomlySignificance: no cardiac output; no pulseDeath producing arrhythmiaTreatment: CODE BLUEDefibrillationIV EpinephrineIV Amiodarone
37 V. Heart Blocks (Bradycardia) Etiology: weakness, fatigue or damage to the AV nodeSignificance: Bradycardia may result in decreased cardiac outputTreatment (same as for bradycardia):IV AtropineIV DopamineTranscutaneous Pacing
38 A. 1st Degree AV BlockEtiology: Prolonged conduction delay in the AV node or Bundle of His.PR interval: greater than 0.20 seconds and is constant
39 B. 2nd Degree AV Block, Type I Etiology: Each successive atrial impulse encounters a longer and longer delay in the AV node until one impulse (usually the 3rd or 4th) fails to make it through the AV node.P waves: More than QRSsP-R interval: gets progressively longer
40 C. 2nd Degree AV Block, Type II Etiology: Conduction is all or nothing (no prolongation of PR interval);typically block occurs in the Bundle of His.More P waves than QRSsPR interval does not vary in length
41 D. 3rd Degree AV BlockEtiology: There is complete block of conduction in the AV node; atria and ventricles form impulses independently of each other.More P: waves than QRSsQRS to QRS (ventricular rate) is regularP to P (atrial rate) is regular—faster than ventricular rate
42 3rd Degree AV Block Characteristics Rate?40 bpmRegularity?regularP waves?no relation to QRSPR interval?noneQRS duration?wide (greater than 0.12 s)
43 Summary Rhythm Rate (beats per minute) Regularity Comments Treatment Sinus60-100RegularNormal rhythm of heartNoneSinus BradycardiaLess than 60Slow rhythm-can cause symptoms of decreased cardiac outputIf symptomatic: atropine 0.5 mg IV pushSinus Tachycardia100 – 150Fast rhythm-caused by fever, pain, dehydrationTreat the causeSuprventricular Tachycardia (SVT)Greater than 150Fast-can cause symptoms of decreased cardiac outputAdenosine, -blockers, Diltiazem (Cardizem), Cardioversion if unstableAtrial FibrillationIrregularNo p-waves, PR not measurable-blockers, Diltiazem (Cardizem)Atrial FlutterRegular or IrregularNo p-waves, flutter waves—sawtooth patternPremature Ventricular ContractionsVaries—can be normalEarly beats, wide, bizarreAmiodaroneVentricular TachycardiaWide, regular, fast; no p-wavesAmiodarone—if pulseDefibrillation—if pulselessVentricular FibrillationRapid,ChaoticNo pattern; Can lead to deathDefibrillation!
44 Summary—Heart Blocks Name of Block # p-waves compared to # QRS complexesPR intervalQRS complexesTreatmentFirst degree# p-waves = # QRS complexesPR interval longer than 0.20; constantAll presentAtropine, if slowSecond degree type IMore p-waves than QRS complexesPR interval gets longer and longerQRS dropped periodicallySecond degree type IIPR interval is constantTranscutaneous pacingThird degree Complete blockNo PR interval; P to P constantQRS to QRS constantEnd of Reading
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