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?
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")
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
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
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.
Wandering Atrial Pacemaker
Rate: Atrial & Ventricular 45 - 100 (slow MAT) P wave: ≥ 3 different 'P' waves QRS: Normal Conduction: P-R intervals vary Rhythm: Irregularly irregular Carotid massage: no effect
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
1:1 ratio of normal:PVC
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.
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
Rate: Not attainable P wave: Obscured by ventricular waves QRS: No true QRS Conduction: Chaotic electrical activity Rhythm: Irregularly Irregular
Accelerated Idioventricular Rhythm
Rate: 50 - 100 (usually slow) P: Obscured by V waves - SA node is slower than faster ventricular pacing QRS: Wide QRS Conduction: Ventricular only Rhythm: Regular - benign rhythm sometimes seen in acute MI/early after reperfusion. Rarely sustained, does not progress to vfib, rarely requires treatment
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
MI evolution: three phases
Acute Onset: T-wave Peaking (Hyperacute T)(T > ½ R wave) A Few Hours Later: T-wave Inversion; ST Elevation (STEMI)/NSTEMI; "tombstone sign" Last: (days/weeks) Significant Q-wave (true infarct)
- 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
no Q wave or ST elevation - T wave inversion - ST DEPRESSION - elevated cardiac enzymes (CPK-MB, troponin) - high risk for later infarction!
Other causes of T-wave inversion?
LBBB: asymmetrical (with wide, upsloping +/- notched QRS); may mask ischemia & bury Q or P LVH: asymmetrical
ST segment and T wave merge into each other without a clear demarcation between them.
- ST elevation w/o infarction & ischemia - Angina that occurs unprovoked at rest (coronary artery spasm) +/- underlying CAD - Provide nitroglycerin & ST returns to baseline
Significant Q waves?
1) Q wave depth ≥ 1/3 the height of the R in the same QRS 2) Q wave duration > 0.04 seconds (1mm)
Ignore Q waves in?
aVR - almost always has significant-appearing Q waves!
Insignificant Qs common in?
Small Qs in I, AVL, V5 & V6 , II, III - Due to depolarization of septum
Posterior infarct - reciprocal changes in?
V1 (poss. V2) - large R = large Q - upright T (T inversion)
Inferior infarct - arteries & leads?
RCA or distal LAD II, III, aVF - Reciprocal changes in anterior and left lateral leads.
Inferior infarct - with time?
May lose Q-wave significance within 6 months
Lateral infarct - arteries & leads?
LCX or diagonal branch of LAD I, aVL, V5, V6 - Reciprocal changes in inferior leads.
Anterior infarct - arteries & leads?
LAD I, V2, V3, V4 - Reciprocal changes in inferior leads.
Posterior infarct - arteries & leads?
- RCA distal branches - Reciprocal changes in V1 (poss. V2) ST-segment depression, tall R wave
RVH v. posterior MI
Both may have tall R waves in V1 & V2, but only RVH will have right axis deviation
conduction block of 1 of 3 LBB fascicles aka fascicular block
L anterior hemiblock
L axis deviation (dt impulse wrapping around from behind) - Normal QRS duration, ST & T-wave - Left axis deviation (-30º & -90º) - No other causes of axis deviation (LVH, LBBB)
L posterior hemiblock
R axis deviation dt flow from anterior fascicle (wrapping around behind) - Normal QRS duration, ST and T-wave - Right axis deviation (+90º & +180º) - No other cause of axis deviation (RVH, MI)
RBBB + either L hemiblock: RBBB - wide QRS, RSR' V1 & V2 (RBBB by itself, usually no axis deviation) + - L Anterior - Left axis deviation - L Posterior - Right axis deviation
RBBB - underlying
May be otherwise normal (sometimes in athletes)
LBBB - underlying
Usually underlying cardiac disease
Bundle blocks evident?
All the time, or only w/ increased HR
no QRS & lead changes - not quite meeting criteria
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
- 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
Intranodal James fibers bypass AV node - PR interval less than 0.12 seconds - Normal QRS width - No delta wave.
Risks of LGL
Not really; mostly reduced CO during stress as no time for atrial kick, impaired filling
- 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.
- ST segment depression - Flattening (or inversion) of the T wave - Appearance of a U wave.
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
- enhances automaticity --> tachyarrhythmias - slowed AV conduction --> AV blocks - PAT with block MC
DIFFUSE flat or concave ST elevation - A large effusion can cause low voltage and electrical alternans.
1) low voltage - diffuse smaller waves 2) electrical alternans - axis changes w/ each beat; large QRS then small QRS
- 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)
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)
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.
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.