(BQ) Part 2 book Pocket ECGs A quick information guide presents the following contents: Atrial dysrhythmias, junctional dysrhythmias, ventricular dysrhythmias, av heart blocks, electrical axis, hypertrophy, bundle branch block and preexcitation, myocardial ischemia and infarction, other cardiac conditions,...
Atrial Dysrhythmias sha19766_cp04.indd 67 7/24/06 11:52:53 AM Chapter What is in this chapter • Premature atrial complexes (PACs) characteristics • Wandering atrial pacemaker characteristics • Atrial tachycardia characteristics Atrial Dysrhythmias 68 • Multifocal atrial tachycardia characteristics • Atrial flutter characteristics • Atrial fibrillatrion characteristics Characteristics common to atrial dysrhythmias • Arise from atrial tissue or internodal pathways • P’ waves (if present) that differ in appearance from normal sinus P waves precede each QRS complex • P’R intervals may be normal, shortened, or prolonged • QRS complexes are normal (unless there is also an interventricular conduction defect or aberrancy) sha19766_cp04.indd 68 7/24/06 11:52:56 AM Wandering atrial pacemaker characteristics Rate: Usually within normal limits Regularity: Slightly irregular P waves: Continuously change in appearance QRS complexes: Normal PR interval: Varies QT interval: Usually within normal limits but may vary Figure 4-1 Summary of characteristics of wandering atrial pacemaker Chapter sha19766_cp04.indd 69 Atrial Dysrhythmias 69 7/24/06 11:52:57 AM Chapter Atrial Dysrhythmias 70 Wandering atrial pacemaker arises from different sites in the atria Figure 4-2 Wandering atrial pacemaker sha19766_cp04.indd 70 7/24/06 11:52:57 AM Premature atrial complexes (PAC) characteristics Rate: Depends on the underlying rhythm Regularity: May be occasionally irregular or frequently irregular (depends on the number of PACs present) It may also be seen as patterned irregularity if bigeminal, trigeminal, or quadrigeminal PACs are seen P waves: May be upright or inverted, will appear different than those of the underlying rhythm QRS complexes: Normal PR interval: Will be normal duration if ectopic beat arises from the upper- or middle-right atrium It is shorter than 0.12 seconds in duration if the ectopic impulse arises from the lower right atrium or in the upper part of the AV junction In some cases it can also be prolonged QT interval: Usually within normal limits but may vary Figure 4-3 Summary of characteristics of premature atrial complexes Chapter sha19766_cp04.indd 71 Atrial Dysrhythmias 71 7/24/06 11:52:57 AM Chapter Atrial Dysrhythmias 72 Premature atrial complexes arise from somewhere in the atrium Figure 4-4 Premature atrial complexes sha19766_cp04.indd 72 7/24/06 11:52:57 AM The pause that follows a premature beat is called a noncompensatory pause if the space between the complex before and after the premature beat is less than the sum of two R-R intervals No n - co m p e n s a to r y pauses are typically seen with premature atrial and junctional complexes (PACs, PJCs) When the tip of the right caliper leg fails to line up with the next R wave it is considered a noncompensatory pause Measure first R-R interval that precedes the early beat Rotate or slide the calipers over until the left leg is lined up with the second R wave — mark the point where the tip of the right leg falls Rotate or slide the calipers over until the left leg is lined up with your first mark Figure 4-5 Premature beats with a noncompensatory pause Chapter sha19766_cp04.indd 73 Atrial Dysrhythmias 73 7/24/06 11:52:57 AM Chapter Atrial Dysrhythmias 74 When the tip of the right caliper leg lines up with the next R wave it is considered a compensatory pause Measure first R-R interval that precedes the early beat Rotate or slide the calipers over until the left leg is lined up with the second R wave —mark the point where the tip of the right leg falls Rotate or slide the calipers over until the left leg is lined up with your first mark Figure 4-6 Premature beats with a compensatory pause sha19766_cp04.indd 74 Compensatory pauses are typically associated with premature ventricular complexes (PVCs) 7/24/06 11:52:58 AM Premature beats occurring in a pattern One way to describe PACs is how they are intermingled among the normal beats When every other beat is a PAC, it is called bigeminal PACs, or atrial bigeminy If every third beat is a PAC, it is called trigeminal PACs, or atrial trigeminy Likewise, if a PAC occurs every fourth beat, it is called quadrigeminal PACs, or atrial quadrigeminy Regular PACs at greater intervals than every fourth beat have no special name Normal PAC Normal PAC Normal PAC Normal PAC a) Figure 4-7 Premature atrial complexes: (a) bigeminal PACs, (b) trigeminal PACs, and (c) quadrigeminal PACs Chapter sha19766_cp04.indd 75 Atrial Dysrhythmias 75 7/24/06 11:52:58 AM Chapter Normal PAC Normal Normal PAC Normal Atrial Dysrhythmias Normal 76 PAC b) Normal Normal PAC Normal Normal Normal PAC c) sha19766_cp04.indd 76 7/24/06 11:52:58 AM Figure 10-4 Leads I, aVL, V5, and V6 are used to identify lateral myocardial infarction I Septal infarction V1 + I + V2 + V3 Lateral infarction + V5 V6 + + V1 V2 V3 V5 aVL Figure 10-3 Leads V1, V2, and V3 are used to identify septal myocardial infarction + Chapter 10 sha19766_cp10.indd 141 V6 aVL Myocardial Ischemia and Infarction 141 7/24/06 2:17:16 PM Chapter 10 Myocardial Ischemia and Infarction 142 Posterior view of heart Inferior infarction Posterior infarction V1 V2 + + II III + II + III + aVF + aVF V1 Figure 10-5 Leads II, III, and aVF are used to identify inferior myocardial infarction sha19766_cp10.indd 142 V3 V2 V3 Figure 10-6 Leads V1 and V2 are used to identify posterior myocardial infarction 7/24/06 2:17:16 PM Other Cardiac Conditions sha19766_cp11.indd 143 11 7/24/06 2:39:35 PM Chapter 11 What is in this chapter • Pericarditis • Pericardial effusion with lowvoltage QRS complexes • Pericardial effusion with electrical alternans sha19766_cp11.indd 144 • • • • Other Cardiac Conditions 144 Pulmonary embolism Pacemakers Electrolyte imbalances Digoxin effects seen on the ECG 7/24/06 2:39:38 PM Pericarditis • Initially with pericarditis the T wave is upright and may be elevated During the recovery phase it inverts • The ST segment is elevated and usually flat or concave • While the signs and symptoms of pericarditis and myocardial infarction are similar, certain features of the ECG can be helpful in differentiating between the two: ∞ The ST segment and T wave changes in pericarditis are diffuse resulting in ECG changes being present in all leads ∞ In pericarditis, T wave inversion usually occurs only after the ST segments have returned to base line In myocardial infarction, T wave inversion is usually seen before ST segment normalization (continued) sha19766_cp11.indd 145 Effects of pericarditis on the heart Enlarged view Normal pericardium Inflamed pericardium Effects on ECG Elevated ST segment is flat or concave ST segments and T waves are off the baseline, gradually angling back down to the next QRS complex Figure 11-1 Pericarditis and ST segment elevation Chapter 11 Other Cardiac Conditions 145 7/24/06 2:39:38 PM Chapter 11 ∞ In pericarditis, Q wave development does not occur • Pericardial effusion is a buildup of an abnormal amount of fluid and/or a change in the character of the fluid in the pericardial space ∞ The pericardial space is the space between the heart and the pericardial sac • Formation of a substantial pericardial effusion dampens the electrical output of the heart, resulting in low-voltage QRS complex in all leads • However, the ST segment and T wave changes of pericarditis may still be seen Figure 11-2 Pericardial effusion with low-voltage QRS complexes sha19766_cp11.indd 146 Pericardial effusion Pericardial sac Pericardial effusion with low-voltage QRS complexes I 146 Other Cardiac Conditions Normal pericardium Collection of fluid Dampened electrical output aVR II aVL III aVF 7/24/06 2:39:39 PM Pericardial effusion with electrical alternans Pericardial sac Collection of fluid H ro ea t a fre te rt el s y • If a pericardial effusion is large enough, the heart may rotate freely within the fluid-filled sac • This can cause electrical alternans, a condition in which the electrical axis of the heart varies with each beat • A varying axis is most easily recognized on the ECG by the presence of QRS complexes that change in height with each successive beat • This condition can also affect the P and T waves Pericardial effusion II Figure 11-3 Pericardial effusion with electrical alternans Chapter 11 Other Cardiac Conditions sha19766_cp11.indd 147 147 7/24/06 2:39:39 PM Chapter 11 Other Cardiac Conditions 148 Pulmonary embolism • ECG changes that suggest the development of a massive pulmonary embolus include: ∞ Tall, symmetrically peaked P waves in leads II, III, and aVF and sharply peaked biphasic P waves in leads V1 and V2 ∞ A large S wave in lead I, a deep Q wave in lead III, and an inverted T wave in lead III This is called the S1 Q3 T3 pattern ∞ ST segment depression in lead II ∞ Right bundle branch block (usually subsides after the patient improves) ∞ The QRS axis is greater than +90° (right axis deviation) ∞ The T waves are inverted in leads V1–V4 ∞ Q waves are generally limited to lead III sha19766_cp11.indd 148 Embolus Large S wave in lead I S1Q3T3 ST segment depression in lead II Large Q wave in lead III with T wave inversion Right bundle branch block in leads V1–V4 V1 V2 T wave inversion in leads V1–V4 V3 V4 Figure 11-4 ECG changes seen with pulmonary embolism 7/24/06 2:39:39 PM Pacemakers • A pacemaker is an artificial device that produces an impulse from a power source and conveys it to the myocardium • It provides an electrical stimulus for hearts whose intrinsic ability to generate an impulse or whose ability to conduct electrical current is impaired • The power source is generally positioned subcutaneously, and the electrodes are threaded to the right atrium and right ventricle through veins that drain to the heart • The impulse flows throughout the heart causing the muscle to depolarize and initiate a contraction sha19766_cp11.indd 149 Impulses initiated by the SA node not reach the ventricles Pacemaker ED CK Pacemaker initiates impulses that stimulate the ventricles to contract BLO Pacemaker spike Figure 11-5 Pacemakers are used to provide electrical stimuli for hearts with an impaired ability to conduct an electrical impulse Chapter 11 Other Cardiac Conditions 149 7/24/06 2:39:39 PM Chapter 11 150 Other Cardiac Conditions Pacemaker impulses Figure 11-6 Location of pacemaker spikes on the ECG tracing with each type of pacemaker Ventricular pacing Atrial pacing Atrial and ventricular pacing Pacemaker spikes • An atrial pacemaker will produce a spike trailed by a P wave and a normal QRS complex • With an AV sequential pacemaker, two spikes are seen, one that precedes a P wave and one that precedes a wide, bizarre QRS complex • With a ventricular pacemaker, the resulting QRS complex is wide and bizarre Because the electrodes are positioned in the right ventricle, the right ventricle will contract first, then the left ventricle This produces a pattern identical to left bundle branch block, with delayed left ventricular depolarization sha19766_cp11.indd 150 7/24/06 2:39:40 PM Electrolyte imbalances Depressed ST segment U wave Hypokalemia • ECG changes seen flattens with serious hypoka- T(orwave is inverted) lemia include: and U wave appears ST segment ∞ Depressed depression ST segment U wave ∞ Flattening of the T wave ∞ Appearance of U waves U wave becomes more prominent ∞ Prolongation of the QT interval Figure 11-7 ECG effects seen with hypokalemia Figure 11-8 ECG effects seen with hyperkalemia Hyperkalemia Peaked, narrow T waves in • ECG changes seen with all leads hyperkalemia include: ∞ Peaked T waves (tenting) ∞ Flattened P waves ∞ Prolonged PR interval (1stdegree AV heart block) T wave peaking increases, P waves flatten and QRS complexes widen ∞ Widened QRS complex ∞ Deepened S waves and merging of S and T waves ∞ Concave up and down slope of the T wave Widened QRS complexes and peaked T waves become almost Sine-wave pattern ∞ indistinguishable, forming what are described as a “sine-wave pattern” Chapter 11 sha19766_cp11.indd 151 Other Cardiac Conditions 151 7/24/06 2:39:40 PM Chapter 11 Hypercalcemia/ Hypocalcemia • Alterations in serum calcium levels mainly affect the QT interval Short QT interval • Hypocalcemia prolongs the QT interval while hypercalcemia shortens it • Torsades de pointes, a variant of ventricular tachycardia, is seen Prolonged QT interval in patients with prolonged QT intervals Figure 11-9 ECG effects seen with hypocalcemia and hypercalcemia sha19766_cp11.indd 152 Other Cardiac Conditions 152 Digoxin effects seen on the ECG • Digoxin produces a characteristic gradual downward curve of the ST segment (it looks like a ladle) ∞ The R wave slurs into the ST segment ∞ Sometimes the T wave is lost in this scooping effect The lowest portion of the ST segment is depressed below the baseline • When seen, the T waves have shorter amplitude and can be biphasic • The QT interval is usually shorter than anticipated, and the U waves are more visible Also, the PR interval may be prolonged Gradual downward curve of the ST segment Figure 11-10 Effects of digoxin on the ECG 7/24/06 2:39:40 PM Index Accelerated idioventricular rhythm, 103–104 Accelerated junctional rhythm, 91–92 Atrial dysrhythmias, 68 Atrial fibrillation, 83–84 Atrial flutter, 81–82 Atrial tachycardia, 77–78 Augmented limb leads, 13–14 AV heart blocks, 108–116 Bipolar leads, 11 Bradycardia, 25, 26 Caliper method, 29 Conduction system, heart’s, Counting the small squares method, 31 sha19766_idx.indd 153 Digoxin, 152–153 Dysrhythmias, by heart rate, 25–26 ECG (electrocardiogram), 3–4 ECG leads augmented limb leads (aVR, aVL, aVF), 13–14, 123 Leads I, II, III, 11–12, 122 modified chest leads, 16 precordial leads (Leads V1–V6 ), 15–16 ECG paper, 9–10 ECG tracings, 3, 4, 19–20 Electrical axis, 119–124 Electrical conductive system, 4, Electrolyte imbalances, 151–152 1500 method, heart rate using, 24 1st-degree AV heart block, 109–110 Heart, 5–7 Heart rate, determining, 21–24 Hypercalcemia/hypocalcemia, 152 Hypokalemia/hyperkalemia, 151 Idioventricular rhythm, 101–102 Irregularity, types of, 32, 40 frequently irregular, 34 irregular irregularity, 38 occasionally irregular, 33 paroxysmally irregular, 36 patterned irregularity, 37 7/31/06 9:18:39 AM 154 slightly irregular, 35 variable irregularity, 39 Junctional dysrhythmias, 86 Junctional escape rhythm, 89–90 Junctional tachycardia, 93–94 Left anterior hemiblock, 133 Left atrial enlargement, 128 Left bundle branch block, 132 Left posterior hemiblock, 134 Left ventricular hypertrophy, 129, 130 Lown-Ganong-Levine syndrome, 136 Mean QRS axis, 120–123 Multifocal atrial tachycardia, 79–80 Myocardial ischemia and infarction, 139–142 P wave, 41, 49–50 Pacemakers, 149–150 Paper and pen method, 30 Pericardial effusion, 146–147 Pericarditis, 145–146 P–P interval, 27–28 PR interval, 45–46, 53–54 Premature atrial complexes (PACs), 71–76 Premature junctional complexes (PJCs), 87–88 Premature ventricular complexes (PVCs), 97–100 Pulmonary embolism, 148 Q wave, 42 QRS complex, 42–44, 51–52, 124 QT interval, 48 R wave, 42 Regularity, determining, 27–40 Right atrial enlargement, 127 Right bundle branch block, 131 Right ventricular hypertrophy, 129, 130 R–R interval, 27–28, 31 S wave, 42 2nd-degree AV heart block, 111–114 Sinus arrest, 65–66 Sinus bradycardia, 59–60 Sinus dysrhythmias, 56, 63–64 Sinus rhythm, 57–58 Sinus tachycardia, 61–62 6-second X 10 method, heart rate using, 21 ST segment, 47 T wave, 48 Tachycardia, 25, 26 Thin lines, to determine heart rate, 23 3rd-degree AV heart block, 115–116 300, 150, 100, 75, 60, 50 method, heart rate using, 22 U waves, 48 Ventricular dysrhythmias, 96 Ventricular tachycardia, 105–106 Wandering atrial pacemaker, 69–70 Waveforms, ECG, 8, 41–54, 119 Wenckebach, 111–112 Wolff-Parkinson-White syndrome, 135 Index sha19766_idx.indd 154 2/28/07 12:03:02 PM ... tachycardia that cannot be clearly identified as atrial or junctional tachycardia is referred to as supraventricular tachycardia Figure 4-8 Summary of characteristics of atrial tachycardia Chapter... quadrigeminal PACs Chapter sha19766_cp04.indd 75 Atrial Dysrhythmias 75 7 /24 /06 11: 52: 58 AM Chapter Normal PAC Normal Normal PAC Normal Atrial Dysrhythmias Normal 76 PAC b) Normal Normal PAC Normal Normal... Normal Normal PAC c) sha19766_cp04.indd 76 7 /24 /06 11: 52: 58 AM Atrial tachycardia characteristics Narrow complex tachycardia that has a sudden, witnessed onset and abrupt termination is called paroxysmal