肇慶市基礎(chǔ)教育信息化建設(shè)與應用調(diào)研

1、EKGReading:Klabunde, Cardiovascular Physiology ConceptsChapter 2 (Electrical Activity of the Heart) pages 27-37Dubin, Rapid Interpretation of EKGs, 6th Edition.Check these hyperlinks out! Dubins EKG Pocket Guide Basic PrinciplesBasic PrinciplesThe EKG records the electrical activity of contraction o

2、f the heart muscleDepolarization may be considered an advancing wave of positive charges within the hearts myocytes- - - - - - - - - - - + + + + + + + +- - - - - - - - - - - + + + + + + + +- - - - - - - - - - - + + + + + + + +- - - - - - - - - - - + + + + + + + + + - - - - - - - - - - - - - - - - -

3、- - - - - + + + + + + + + + + + + + + + +- - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + Depolarization WaveDepolarizationRepolarizationConduction SystemSA NodeAnteriorInternodal PathwayMiddleInternodal PathwayPosteriorInternodal PathwayAnterior interatrial myocardial b

4、and(Bachmanns Bundle)Left AtriumAN Region N Region NH Region AV NodeBundle of HisRight Bundle BranchLeft Bundle BranchAnterior DivisionPosterior DivisionRight Atrial TractsSinus RhythmThe SA (Sinus) Node is the hearts dominant pacemaker.The ability of a focal area of the heart to generate pacemaking

5、 stimuli is known as Automaticity.The depolarization wave flows from the SA Node in all directions.Atrio-Ventricular (AV) ValvesPrevent blood backflow to the atriaElectrically insulate the ventricles from the atriaAV ConductionAV node is situated on right side of interatrial septum near the ostium o

6、f the coronary sinusWhen the wave of depolarization enters the AV Node, depolarization slows, producing a brief pause, thus allowing time for the blood in the atria to enter the ventricles.RepolarizationPlateauRapid Repolarization PhaseST SegmentVentricular SystoleQT IntervalRecording the EKGLimb Le

7、adsIIIIIIAVRAVLAVFChest LeadsV1V2V3V4V5V6Autonomic Nervous SystemCheck for these on every EKGRATERhythmAxisHypertrophyInfarctionSinus RhythmThe SA (Sinus) Node is the hearts dominant pacemaker.The generation of pacemaking stimuli is automaticity.The depolarization wave flows from the SA Node in all

8、directions.Sinus RhythmThe Sinus Node is the hearts normal pacemakerNormal Sinus Rhythm: 60-100/min.Sinus Bradycardia: Less than 60/min.Sinus Tachycardia: More than 100/min.Automaticity FociLevelAtriaAV JunctionVentriclesInherent Rate Range60-80/min.40-60/min.20-40/min.Overdrive SuppressionSA NodeAt

9、rial Foci (60-80 bpm)Junctional Foci (40-60 bpm)Ventricular Foci (20-40 bpm)Overdrive SuppressionRATESay “300, 150, 100 “75, 60, 50But for bradycardia: rate = cycles/6 sec. strip 10Check for these on every EKGRateRHYTHMAxisHypertrophyInfarctionRHYTHMIdentify the basic rhythm, then scan tracing for p

10、rematurity, pauses, irregularity, and abnormal waves.Check for: P before each QRS.Check for: QRS after each P.Check: PR intervals (for AV Blocks).Check: QRS interval (for Bundle Branch Block)Sinus RhythmOrigin is the SA Node (“Sinus Node)Normal sinus rate is 60 to 100/minuteRate more than 100/min. =

11、 Sinus TachycardiaRate less than 60/min. = Sinus BradycardiaSinus BradycardiaSinus TachycardiaArrhythmiasIrregular rhythmsEscapePremature beatsTachy-arrhythmiasIrregular RhythmsSinus ArrhythmiaWandering PacemakerMultifocal Atrial TachycardiaAtrial FibrillationSinus ArrhythmiaIrregular rhythm that va

12、ries with respiration.All P waves are identical.Considered normal.Wandering PacemakerIrregular rhythm. P waves change shape as pacemaker location varies.Rate under 100/minuteMultifocal Atrial TachycardiaIrregular rhythm. P waves change shape as pacemaker location varies.Rate greater than 100/minuteA

13、trial FibrillationIrregular ventricular rhythm.Erratic atrial spikes (no P waves) from multiple atrial automaticity foci.Atrial discharges may be difficult to see.EscapeEscape RhythmAtrial Escape RhythmJunctional Escape RhythmVentricular Escape RhythmEscape BeatAtrial Escape BeatJunctional Escape Be

14、atVentricular Escape BeatPremature BeatsPremature Atrial BeatPremature Junctional BeatPremature Ventricular Contraction (PVC)Atrial BigeminyPVCsBigeminyTachyarrhythmiasParoxysmal Atrial Tachycardia(Supraventricular Tachycardia)An irritable atrial focus discharging at 150-250/min. produces a normal w

15、ave sequence, if P waves are visible.P.A.T. with block(Supraventricular Tachycardia)Same as P.A.T. but only every second (or more) P wave produces a QRS.Paroxysmal Junctional TachycardiaAV Junctional focus produces a rapid sequence of QRS-T cycles at 150-250/min.QRS may be slightly widened.Paroxysma

16、l Ventricular TachycardiaVentricular focus produces a rapid (150-250/min) sequence of (PVC-like) wide ventricular complexes.Atrial FlutterA continuous (“saw tooth) rapid sequence of atrial complexes from a single rapid-firing atrial focus.Many flutter waves needed to produce a ventricular response.V

17、entricular FlutterA rapid series of smooth sine waves from a single rapid-firing ventricular focusUsually in a short burst leading to Ventricular Fibrillation.Atrial FibrillationMultiple atrial foci rapidly discharging produce a jagged baseline of tiny spikes.Ventricular (QRS) response is irregular.

18、Ventricular FibrillationMultiple ventricular foci rapidly discharging produce a totally erratic ventricular rhythm without identifiable waves.Needs immediate treatment.BlockSinus BlockAV BlockBundle Branch BlockHemiblockSinus (SA) BlockAn unhealthy Sinus (SA) Node misses one or more cycles (sinus pa

19、use)The Sinus Node usually resumes pacingHowever, the pause may evoke an “escape response from an automaticity focus1 AV BlockPR interval is prolonged to greater than 0.2 sec (one large square)1 AV Block2 AV Block(Some P waves without QRS Response)WenkebachPR gradually lengthens with each cycle unti

20、l the last P wave in the series does not produce a QRS2 AV Block(Some P waves without QRS Response)MobitzSome P waves dont produce a QRS response.Intermittent may cause an occasional QRS to be dropped.More advanced may produce a 3:1 pattern or higher AV ration.2 AV Block(Some P waves without QRS Res

21、ponse)2:1 AV BlockMay be Mobitz or Wenkebach.2 AV Block3 AV Block(“Complete Block)P waves of SA node originQRSs if narrow, and if the ventricular rate is 40-60/min., then origin is a junctional focus.3 AV Block(“Complete Block)P waves of SA node originQRSs if PVC-like, and if the ventricular rate is

22、 20-40/min., then origin is a ventricular focus.3 AV BlockBundle Branch BlockFind R, R in right or left chest leadsAlways check: Is QRS within 3 tiny squares? Left Bundle Branch BlockRight Bundle Branch BlockHemiblockBlock of Anterior or Posterior Fasicle of the Left Bundle BranchAlways check: Has A

23、xis shifted outside normal range?Anterior Hemiblock:Axis shifts leftward L.A.D. Look for Q1S3Posterior Hemiblock:Axis shifts rightward R.A.D. Look for S1Q3Left Anterior HemiblockCheck for these on every EKGRateRhythmAXISHypertrophyInfarctionUsing Vectors to Represent Electrical PotentialsA vector is

24、 an arrow that points in the direction of the electrical potential generated by current flowThe arrowhead of the vector is in the positive directionThe length of the arrow is drawn proportional to the voltage of the potentialNSEW+RVLV+Lead I+AxisQRS above or below baseline for Axis Quadrant (Normal

25、vs. R or L Axis Dev.)For Axis in degrees, find isoelectric QRS in a limb leadAxis rotation in the horizontal plane (chest leads) find “transitional (isoelectric) QRSCauses of Axis DeviationChange of the position of the heart in the chestHypertrophy of one ventricleMyocardial infarctionBundle branch

26、blockCheck for these on every EKGRateRhythmAxisHYPERTROPHYInfarctionHypertrophyP wave for Atrial hypertrophyR wave for Right Ventricular HypertrophyS wave depth in V1 + R wave height in V5 for Left Ventricular HypertrophyRight Atrial HypertrophyLarge, diphasic P wave with tall initial componentSeen

27、in lead V1Left Atrial HypertrophyLarge, diphasic P wave with wide terminal componentSeen in lead V1Right Ventricular HypertrophyR S wave in V1R wave gets progressively smaller from V1-V6S wave persists in V5-V6RAD with slightly widened QRSRightward rotation in the horizontal planeLeft Ventricular Hy

28、pertrophymm of S in V1mm of R in V5+Total:If more than 35 mm there is LVHLeft Ventricular HypertrophyLAD with slightly widened QRSLeftward rotation in the horizontal planeInverted T waveSlants downward gradually, but up rapidlyHypertrophyLeft Ventricle and Left AtriumCheck for these on every EKGRate

29、RhythmAxisHypertrophyINFARCTION (and Ischemia)InfarctionScan all leads for:Q wavesInverted T wavesST segment elevation or depressionFind the location of the pathology and then identify the occluded coronary arteryNecrosis= Q wave (significant Qs only)Significant Q wave:One mm wide (0.04 sec in durat

30、ion) or1/3 the amplitude (or more) of the QRSOmit lead AVR when looking for significant QsOld infarcts: Q waves remain for a lifetimeInjury= ST elevationSignifies an acute processST elevation associated with significant Q waves indicates an acute (or recent) infarctST depression (persistent) may represent a “subendocardial infarctionIschemia= T wave inversionInverted T wave (of ischemi