ECG Strip Interpretation EXAM(470 QUESTIONS WITH VERIFIED EXPERT SOLUTIONS 2024

Normal PR segment length 0.12 - 0.2 sec 3 - 5 small boxes Normal QRS interval 0.06 - 0.1 sec 1 - 3 small boxes Brainpower Read More Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:01 / 0:15 Full screen Normal P amplitude & duration < 0.12 sec (3 small boxes) < 0.25 mV (2.5 small boxes) causes of arrhythmias HISDEBS: hypoxia, ischemia/irritability, SNS, drugs, electrolytes, bradycardia, stretch (hypertrophy/enlargement) symptoms of arrhythmias none, "palpitations," light-headedness, syncope, angina, HF, sudden death Arrhythmias - 4 quick questions 1. Normal P waves? 2. Wide QRS? (> 0.12 sec indicates pacemaker below Bundle of His) 3. One P for every QRS? 4. Normal rate & rhythym? Sinus arrhythmia Appearance is ALMOST NORMAL: Respiratory - Circulatory interaction Rate INCREASES with INSPIRATION (IN=IN) Sinus arrest - criteria Rate: Regular or Bradycardia P wave: Normal QRS: Normal Conduction: Normal Rhythm: Irregular: length of pause ≠ multiple of normal rate (random) Junctional Escape Beat/Rhythym - criteria Rate: Bradycardia P wave: Absent or Inverted P; if present, may occur during or after the QRS QRS: Normal Conduction: Escape beat: P-R interval < 0.12 seconds (if P present) Rhythm: Irregular when it occurs (late) If occurs 3 or more times in a row, is considered junctional escape rhythm Sinus exit block - criteria Rate: Regular or Bradycardia P wave: Normal QRS: Normal Conduction: Normal Rhythm: Irregular: length of pause = multiple of normal rate (Signal blocked leaving SA node; block is exactly equal to multiple of rate - one or more impulses "missed") PACs (premature atrial contractions/atrial premature beats) - criteria Rate: Regular underlying rate P wave: Abnormal - they originate from an ectopic pacemaker QRS: Normal Conduction: Normal (except for PACs) Rhythm: Irregular when PACs occur (early) PJCs (Premature Junctional Contractions) AKA: Junctional Premature Beats Rate: Regular underlying rate P wave: Absent or Inverted (like junctional escape) QRS: Normal Conduction: PJC: P-R interval < 0.12 seconds (if P waves are present) Rhythm: Irregular when PJCs occur (early) PSVT (Paroxysmal Supraventricular Tachycardia) AKA: AV nodal Re-entrant Tachycardia Rate: Tachycardia (usually 150 - 200) P wave: Absent or Inverted (like junctional escape) QRS: Normal (may be wide, pseudo R') Conduction: P-R interval < 0.12 seconds (if P) Rhythm: Regular (abrupt onset and termination) Carotid massage: slows or terminates Atrial flutter Rate:Atrial 250-350 Ventricular: 100 -175 P: Irregular or absent, often "saw tooth" QRS: Normal Conduction: AV Block (2:1 > 3:1, 4:1) Rhythm: Regular (usually) - Often underlying cardiac disease Carotid massage: increases block Atrial fibrillation Rate: Atrial 400-650; Ventricular usually 120 - 180 P wave: Not present; often wavy baseline QRS: Normal Conduction: Variable AV conduction Rhythm: Irregularly Irregular - chaotic, unpredictable depolarizations w/i atrium, no atrial kick - CAD, HTN, COPD, etc. Carotid massage: may slow ventricular rate MAT (Multifocal Atrial Tachycardia): Rate: Atrial varies, Ventricular 100-200 P wave: ≥ 3 different 'P' waves QRS: Normal Conduction: AV conduction, P-R intervals vary Rhythm: Irregularly irregular Carotid massage: no effect Etiology: longstanding COPD, etc. PAT (Paroxysmal (episodic) Atrial Tachycardia) Rate: 100 - 200; Ventricular 1:1 (or 2:1, 3:1, 4:1) P wave: Usually present, abnormal QRS: Normal Conduction: P-R interval varies (dt ectopic sites) Rhythm: Regular (warm up &/or cool down) Carotid massage: no effect, or only mild slowing bigeminy? 1:1 ratio of normal:PVC trigeminy? 2:1 ratio of normal:PVC PVCs (Premature Ventricular Contractions) Rate: Regular underlying rate (usually) P wave: Absent (or abnormal) in PVC QRS: PVC: wide > 0.12 seconds; shape is bizarre; T wave inversion Conduction: Normal before & after PVC Rhythm: Irregular; may occur in singles, couplets or triplets Reasons to worry about PVCs? - Frequency increasing - Runs of 3 or more consecutively - Multiple PVC foci - R-on-T Phenomenon - PVC in acute MI Multiple PVC foci Beats 1 and 4 are sinus in origin. The other three beats are PVCs. The PVCs differ from each other in shape (multiform), and two occur in a row. PVC - R on T A PVC falls on the T wave of the second sinus beat, initiating a run of ventricular tachycardia. Ventricular tachycardia Rate: 120 - 200 usually P wave: Usually absent (unrelated to the QRS) QRS: Wide & bizarre shape (PVCs) Conduction: No correlation between 'P' if present and QRS Rhythm: Regular or Irregular * Cannon A waves may be present Carotid massage: no effect Ventricular Fibrillation Rate: Not attainable P wave: Obscured by ventricular waves QRS: No true QRS Conduction: Chaotic electrical activity Rhythm: Irregularly Irregular Torsades de Pointes Rate: 120 - 200 usually P wave: Obscured by ventricular waves QRS: Wide QRS - "Twisting of the Points" Conduction: Ventricular only Rhythm: Slightly irregular 1º AV block Rate: Normal (usually) P wave: Normal QRS: Normal Conduction: P-R interval is > 0.2 seconds (delay) Rhythm: Regular 2º AV Block - Wenckebach/Mobitz Type I Rate: Normal or Bradycardia P wave: Normal & constant P-P interval QRS: Normal Conduction: P-R interval is progressively longer until P wave is blocked; the cycle begins again Rhythm: Irregular 2º AV Block - Mobitz Type II Rate: Bradycardia P wave: Normal & constant P-P interval QRS: Normal or widened (usually associated with a bundle branch block) Conduction: P-R interval normal or prolonged (constant); some P waves are not conducted to ventricles (varies) 3º AV Block Rate: Atrial 60-100; Ventricular 30-45 P wave: Normal with constant P-P interval ("marching through") QRS: Usually widened (depends on location of escape pacemaker) Conduction: Atrial & Ventricular activities are unrelated (complete block) Rhythm: Irregular Bundle branch blocks - general criteria Due to changes related to the block, cannot say there is hypertrophy - BBB will make it look like hypertrophy Rate: Regular or Bradycardia P wave: Normal usually QRS: Wide > 0.12 seconds Conduction: Block occurs in the right or left bundle branches (or both) Rhythm: Regular usually Right bundle branch block (RBBB) Right ventricular depolarization is delayed Criteria: - QRS complex > 0.12 seconds - RSR′ in V1 and V2 (rabbit ears) with ST segment depression and T wave inversion - Reciprocal changes in V5, V6, I, and aVL. Left bundle branch block (LBBB) LV depolarization is delayed Criteria: - Wide QRS > 0.12 - Broad (+/- notched) R waves, ST depression & T-wave inversion in I, aVL, V5, V6 - Broad S waves in V1, V2 - Left axis deviation may be present Ischemic signs - ST elevation or ST depression: > 1mm related to baseline (0.08 s (2 boxes) after QRS) - Also symmetric T-wave inversion in multiple precordial leads Other causes of ST elevation evolving transmural MI, Prinzmetal's angina, J point elevation, acute pericarditis, acute myocarditis, hyperkalemia, PE, Brugada syndrome, hypothermia RBBB - underlying May be otherwise normal (sometimes in athletes) LBBB - underlying Usually underlying cardiac disease Wolff-Parkinson-White Syndrome (WPW) - Bypass pathway (bundle of Kent) between atria & ventricles - No pause at AV node - short PR interval - Delta Wave: Slurred initial upstroke of R Short PR interval < 0.12 seconds Wide QRS > 0.1 second with delta wave WPW risks - PSVT dt reentrant pathway present; may be narrow QRS if via AV node & back up Kent, or wide (& hard to distinguish from V tach) if via Kent & back up AV node - a fib - Kent acts as free conduit for chaotic atrial activity; may lead to V fib Hyperkalemia - Evolution of (1) peaked T waves, (2) PR prolongation & P wave flattening, & (3) QRS widening. - Ultimately, the QRS complexes and T waves merge to form a sine wave, and ventricular fibrillation may develop. Hypokalemia - ST segment depression - Flattening (or inversion) of the T wave - Appearance of a U wave. Hypercalcemia shortened QT Hypocalcemia Prolonged QT - risk of R on T leading to Torsades de Points causes of long QT - Medications: many antiarrhythmics, tricyclic antidepressants, quinolone antibiotics, etc. - hypocalcemia - Inherited disorder: Long QT Syndromes Digitalis/Digoxin - indications - Increase contractility - Slows AV junction conduction - Used to tx HF Digitalis effect - therapeutic levels Asymmetric ST depression, flat/inverted T-wave Digitalis toxicity - enhances automaticity --> tachyarrhythmias - slowed AV conduction --> AV blocks - PAT with block MC pericarditis DIFFUSE flat or concave ST elevation - A large effusion can cause low voltage and electrical alternans. pericardial effusion 1) low voltage - diffuse smaller waves 2) electrical alternans - axis changes w/ each beat; large QRS then small QRS COPD - Low voltage, - Right axis deviation (RVH), - poor R wave progression - P pulmonale (right atrial enlargement; tall P >2.5 in II) & abnormal P in V1) - "barrel chest" - increase AP diameter Acute pulmonary embolism Signs may include: - RVH, RBBB (blood not getting through dt clot) - Arrhythmias (s. tach & a fib MC) - S1Q3: large S in lead I, deep Q wave ONLY in lead III (if deep Q in several, then infarct) Brugada syndrome structurally normal hearts - autosomal dominant, M > W - Resembles RBBB; ST elevation & RSR' in leads V1, V2, and V3. - can cause fast polymorphic V tach (looks like torsades de pointes). - ICD required (b-blockers no help) Common in athletes - sinus bradycardia as low as <30 bpm - ST elevation in precordial w/ T flattening or inversion. - LVH, sometimes RVH criteria - Incomplete RBBB - 1º or Wenckebach AV block. - Arrhythmias (junctional, wandering atrial pacemaker) Hypothermia Osborne waves (ST elevation- abrupt ascent at J point & sudden plunge back to baseline) prolonged intervals, sinus bradycardia, slow atrial fibrillation. Beware of muscle tremor artifact. CNS disease Diffuse T wave inversion, with T waves typically wide and deep; U waves. Indications for stress test - eval CP/ro CAD - eval >40 w/ risk factors for CAD - assess pt response to interventions - ?eval asx adults who want to start vigorous exercise (lots of false +) criteria for selection of pts for stress test - sx classic, atypical, or not at all angina-like? - established CAD? - functional tolerance to exercise? stress test - contraindications - angina at rest - uncontrolled HF - acute systemic illness - severe aortic stenosis - hypertrophic cardiomyopathy (sudden death) - ability to walk/exercise - caution if systolic > 200 or diastolic > 120; risk of hemorrhagic stroke! normal physiological response to stress test - incr SNS - incr CO - incr skeletal mm perfusion - incr O2 extraction - decr PVR - incr systolic BP stress test - pt preparation - DC meds which may interfere (b-blockers, CCBs, digoxin, nitrates) - no food, smoking, drink 2-4 hrs before - pretest EKG - pretest BP stress test - finished when? 1) pt cannot tolerate dt compliance or sx 2) 90% of max HR reached 3) Significant EKG changes stress test - positive when? Horizontal or down-sloping ST depression (> 1mm & > 0.08 sec); earlier occurrence in test, more significant; or exercise-induced hypotension, severe arrhythmia, or areas of heart w/ reduced blood ST segment elevation - reasons - With an evolving infarction - In Prinzmetal's angina. ST segment depression - With typical exertional angina - In a non-Q wave infarction. Also: - positive stress test. - J point elevation - Acute pericarditis - Acute myocarditis - Hyperkalemia - Pulmonary embolism (S1Q3) - Brugada syndrome - Hypothermia coronary cath - reasons? testing & interventions; can be used w/ balloon angioplasty or stenting echocardiogram Transesophageal or transthoracic - 2D or 3D, Doppler, basically ultrasound of heart; can see movement of blood, valve regurgitation - can see valves & cardiomyopathies very well Ashman phenomenon Aberrant conduction of a supraventricular beat commonly seen in patients with atrial fibrillation; wide SV beat after a QRS complex that is preceded by a long pause. How to interpret an EKG 1) Identify all waves & segments 2) Calculate rate 3) Determine intervals (PR, QT, QRS) 4) QRS axis 5) Hypertrophy & enlargement 6) Rhythm (normal P, wide QRS, P:QRS ratio, regular rhythm?) 7) Coronary artery disease 8) Other weird stuff anterior leads V2, V3, V4 left lateral leads I, aVL, V5, V6 inferior leads II, III, aVF right ventricular leads aVR, V1 Lead I - angle +0º left lateral Lead II - angle +60º inferior Lead III - angle +120º inferior Lead aVF - angle +90º inferior Lead aVR - angle -150º - "la la land" right ventricular Lead aVL - angle -30º left lateral Normal PR segment length 0.12 - 0.2 sec 3 - 5 small boxes