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16 Cards in this Set
- Front
- Back
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Describe normal QRS morphology
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initial depolarization is left-to-right across septum (r in V1 and q in V6; absent in LBBB!)
followed by LV and RV free wall depolarization, with LV dominating (RV depolarization later and visible in RBBB) |
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Describe RBBB morphology |
1. QRS 120 or greater (110-119 incomplete) 2. rSR' in right precordial leads (V1, V2) 3. wide S waves in I and V6 4. +/- ST depressions or TWI in right precordial leads |
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Describe LBBB morphology |
1. QRS 120 or greater (110-119 incomplete) 2. broad, slurred, monophasic R in I, aVL, V5-V6 (+/- RS in V5-V6 if cardiomegaly) 3. absence of Q in I, V5, and V6 4. Displacement of ST & T wave opposite major QRS deflection 5. +/- PRWP, LAD, Q waves in inferior leads |
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The components of a systematic approach to EKG assessment |
rate (?tachy/brady) rhythm (P : QRS) intervals (PR, QRS, QT) axis (?LAD or RAD) chambers (?LAA/RAA/LVH/RVH) QRST changes (?Q waves, poor R wave progression, V1-V6 STE/STD or T wave changes)
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8 causes of poor R wave progression |
1. old anterior MI 2. lead misplacement (?obese woman) 3. LBBB or LAFB 4. LVH 5. WPW 6. dextrocardia 7. tension pneumothorax with mediastinal shift 8. congenital heart disease |
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LAD: definition |
axis beyond -30, (S > R in lead II) |
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LAD: etiologies |
LVH, LBBB, inferior MI, WPW |
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define LAFB |
LAD (-45 to -90) + (rS in I and aVL) + qR in III and aVF + QRS < 120 msec + no other cause of LAD (e.g., inferior MI) |
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RAD: definition |
axis beyond +90 (S > R in lead I) |
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RAD: etiologies |
RVH PE COPD (usually not > +110) septal defects, lateral MI, WPW |
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LPFB: definiton |
RAD (+90-+180) + rS in I and aVL + qR in III and aVF + QRS <120 msec + no other cause of RAD |
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Drugs that promote/exacerbate long QT |
antiarrhythmics (class Ia, class III) psychotropes (antipsychotics, Li, TCA, ?SSRI) antimicrobials (macrolides, quinolones, azoles, pentamidine, atovaquone, atazanavir) others (antiemetics: droperidol, 5-HT3 antagonists; alfuzosin, methadone, ranolazine) |
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Electrolyte disturbances that promote/exacerbate long QT |
hypo-Ca2+ (note: hypercalcemia a/w *shortened* QT) ?hypo-K+ ?hypo-Mg2+ |
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General etiologies of long QT |
drugs electrolyte disturbances autonomic dysfunction congenital misc (CAD, CMP, bradycardia, high-grade AVB, hypothyroid, hypothermia, BBB) |
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EKG criteria for left atrial abnormality (LAA) |
lead II: bimodal P > 120 ms V1: sinusoid P > 1mm below baseline |
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EKG criteria for right atrial abnormality (RAA) |
lead II: P wave taller than 2.5mm above baseline V1: sinusoid P >1.5 mm above baseline |
