Premature Junctional Contraction (PJC)

• Supraventricular rhythms involve junctional/nodal rhythms, heart blocks, premature junctional contraction (PJC), junctional rhythm, and paroxysmal junctional tachycardia.
• Heart blocks are categorized as first-degree, second-degree (Type I/Wenckebach or Mobitz type I, Type II/Mobitz type II), third-degree (complete AV heart block), and bundle branch block (BBB) with Right BBB and Left BBB.

Nodal/Junctional Arrhythmias

• Nodal or Junctional Arrhythmias consists of premature junctional complex/contraction, junctional rhythm, and junctional tachycardia.

Premature Junctional Contraction (PJC)

• Premature impulses arise from the AV node in PJCs.
• Similar to PACs, yet the P wave is absent, inverted, or retrograde, following the QRS complex instead of preceding it.
• The QRS duration is usually identical 0.04-0.10 seconds, but may be slightly widened.
• R-R interval remains regular, except during the premature beat.

PJC Signs, Symptoms and Treatment

• Possible causes of PJC include decreased automaticity and conductivity of the SA node, irritable AV node or junctional tissue, cardiac disease, or MV disease, and it may even be a precursor to abnormal rhythms.
• Treatment is not needed unless there are symptoms of clinical relevance and addressing the underlying cause.

Junctional Rhythm

• The AV node takes over as the pacemaker.
• Junctional rhythm is also known as Junctional Escape Rhythm
• P wave is absent prior to the QRS or may present as retrograde.
• QRS appears normal with a duration of 0.04-0.10 seconds.
• R-R interval remains regular, with a rate of 40-60 bpm.

Junctional Rhythm Symptoms, Causes and Treatment

• Symptoms and causes of junctional rhythm can include SA node disease, increased vagal tone, digoxin toxicity, myocardial infarction to conduction system, decreased cardiac output due to slow rate, dizziness, or fatigue.
• Treatment can include identifying and treating the underlying problem, medications to increase heart rate, and PPM

(Paroxysmal) Junctional Tachycardia

• Similar to junctional rhythm but with a higher rate.
• P waves are absent except for retrograde conduction.
• QRS is identical with a duration of 0.04-0.10 seconds, and may be slightly widened.
• R-R interval is regular, with a rate usually greater than 100 bpm (Dubin: 150-250 bpm).
• AVNRT (AV Nodal Reentry Tachycardia) presentation is possible.
• Signs, symptoms involving hyperventilation, CAD or myocardial infarction, digoxin toxicity, caffeine, nicotine, overexertion or emotional states.
• Decreased CO leads to lightheadedness or fatigue.
• Treatment involves identifying and addressing the cause, digoxin if the cause is not identified, vagal stimulation, and beta blockers.

Heart Blocks

• Heart Blocks fall under Atrioventricular (AV) Conduction Blocks
• Degrees are first-degree AV heart block, second-degree AV heart block (Type I/Wenckebach or Mobitz type I, Type II/Mobitz type II), third-degree AV heart block ("Complete heart block"), bundle branch block with Right BBB and Left BBB.

First Degree AV Heart Block

• SA node fires, however, the impulse is delayed to the AV node, which is initiated at the AV node and conduction is prolonged.
• Lengthened PR interval is measured at >0.20 seconds.
• P wave is present for every QRS complex and the QRS is normal at 0.04-0.10 seconds.
• R-R intervals are regular, with a heart rate of 60-100 bpm or can be below 60.
• Causes can include CAD, RHD, MI, or reaction to medications.
• Benign, but should be monitored to prevent furthering development.
• Treatment is usually not needed unless due to medications where discontinuation is advised.

Second Degree AV Block, Type I

• Second Degree AV block is also known as Wenckebach or Mobitz I
• It is considered a relatively benign disturbance that occurs in the AV node, particularly high in the AV junction. It prevents some impulses from getting through.
• A P wave precedes a QRS, with a possible P wave alone.
• Progressive lengthening of the PR interval occurs, until a QRS gets dropped.
• Consistent P: QRS ratio (often 3:2, 4:3, with 1 less QRS than P waves in the series).
• QRS normal and between 0.04-0.10 seconds.
• R-R is irregular

2nd Degree AV block, Type I (Wenckebach) Signs, Symptoms, Treatment

• Heart diseases like heart failure or CHD/CAD and Digoxin toxicity coupled with the excessive use of B blocker levels can be a possible cause
• Patient generally asymptomatic, but fainting, dizziness, fatigue or shortness of breath, and chest pain is possible
• Treatment may be unnecessary and can me managed with atropine or a temporary PPM placement when needed, and may resolve with correction of ischemia in RCA
• It rarely progress to higher degrees of block

Second Degree AV block, Type II

• Mobitz II originates below the AV node, specifically the Bundle of His/Branches.
• Impulse usually is not transmitted regularly to the ventricles without PR interval lengthening.
• A dropped QRS with fixed PR intervals
• Ratio of P waves to QRS complexes is >1:1, varying from 2 to 4 P waves for every QRS complex.
• QRS may be normal but is slightly widened as it originates below the AV node.
• R-R intervals are irregular depending on block frequency
• HR<100 can also be less
• Possible causes can be ischemia or infarction of the AV node or digoxin toxicity following a myocardial infarction
• Reduced CO and HR with fatigue and chest pains are possible
• Management is most often PPM and meds like atropine and B blocker
• Prone to progressing to 3rd degree

Third Degree AV Heart Block

• B-A-D aka COMPLETE HEART BLOCK (CHB) involves complete independence between the atria and ventricles. All impulses initiated above the AV node are not conducted to the ventricle.
• P waves are present and identical, but bear no relationship to QRS, with variable PR intervals.
• QRS complexes are regular
• R-R intervals are regular
• QRS duration may be wider than 0.10 seconds, with a heart rate of 30-50 bpm.
• Can stem from acute MI and conduction system degeneration that leads to decreased HR and a decreased cardiac output. Can stem from Digoxin toxicity
• A person may be symptomatic, and in that case will experience, dizziness, and near or loss of consciousness
• A medical emergency that can be managed w/ temporary use of atropine, followed by B Blockers
• Treatment for more sustainable management is a pacemaker

Bundle Branch Block (BBB)

• Results from a block of conduction in the right or left bundle branch resulting in a delay depolarization of the ventricle
• Depolarization happens simultaneously in the ventricles
• A conduction of ventricles out of synch widens the QRS
• Wide QRS results from superimposing both ventricle QRS of each other
• QRS duration is > 0.12 seconds.
• An EKG can be seen with 2 R waves, R and R1
• R1 delayed depolarization
• Possible treatment is a PPM

RBBB vs LBBB

• Left BBB (LBBB)
  • the right ventricle depolarizes 1st
  • R = right ventricular depol
  • R1= Left Ventricular depol
  • Best seen in V5 and V6
  • Wide bizarre looking QRS
• Right BBB (RBBB)
  • Left Ventricle depolarizes
  • R-Left Ventricular depol
  • R1 = Right Ventricular depol.
  • Best seen in V1 and V2
  • Rabbiet Ear appearance of R wave
• Use "WiLLiaM" vs "MaRRoW" to differentiate between the 2

Ventricular Rhythms

• Ectopic beats that originate in any part of the ventricle. The normal route of depolarization is bypassed. Results in a wide, bizarre-looking QRS, greater than 0.12 seconds.

Ventricular Arrythmias

• Arrythmias originating in the ventricles includes Premature Ventricular Complex/Contraction or PVC such as Unifocal, Multifocal, Couplet, Bigeminy, Trigeminy, Interpolated, Ventricular Tachycardia , Torsades de Pointes, and Ventricular Fibrillation.

Premature Ventricular Contractions (PVCs)

• Ectopic foci are generated in the ventricles
  • UNIFOCAL-from the same focus
  • MULTIFOCAL-from different foci
• Rate is determined by the underlying rhythm
  • Rhythm is usually regular with compensatory pause following the premature beat(s)
• P waves are not visible on abnormal beat
  • Relationship of P to QRS = N/A for premature beat QRS is wide
  • "Bizarre" QRS = 0.12 sec or greater.

PVC Causes, Symptoms, Treatment

• Causes include an irritable site in ventricles causing a change in QRS that stems from stimulants, medication, pH imbalance, electrolyte imbalance, anxiety or stress, and myocardial damage.
• Patient may express a palpation of pulse that feels like a missed beat or pause.
• Frequent episodes of PVCs can cause decreased CO, and a potential to progress to V-tach or V-fib.
• Treatment focuses on the underlying cause

Premature Ventricular Contractions (PVCs) observations to be made

• Observations to be noted in PVCs are the frequency and pattern of occurrence, checking for more than 6 PVCs/min, whether they are multifocal, or if there are patterns:
  • couplement (2 PVC following each other)
  • Bigeminy (ever other beat)
  • Trigeminy (every third beat)
  • interpolated with a PVC occurring early enough be sandwiched between 2 normal beats.
• Observe also the R on T Phenomonem

Ventricular Tachycardia vs Non-Sustained Ventricular Tachycardia

• Ventricular Rate = > 100 bpm
• P: QRS = None, or P waves absent
• Sustained Vtach > 30 sec duration
• Non sustained Vtach is duration less then 30 sec

V Tach

• Defined as three or more PVCs consecutively
• Ventricular Rate >100

Torsades de Pointes as Ventricular Tacchycardia

• A French term: "Twisting of the points" around the isoelectric line, with a rate of 250-350. It is often associated with an elongated GT
• It is seen only because of toxic ammiodarone
• If conscious they may present with lightheadedness or near syncope

Ventricular Fibrillation (V Fib)

• Consist of erratic quivering of the heart, with multifocal ventricular ectopic foci firing, creating asynchrony.
• There is no electrical cardiac output detected, that requires immediate attention
• The process requires beginning CPR then immediately following up with Electrical management

Aystole and Cardiac Arrest

• BAD or Death requires calling a code for any symptoms present from a Cardiac Arrest or Cardiac Flat Rate are electrical components related to the process

Pacemakers

• Has a spike with no deflection of the EKG rate present
• PPM will not fire unless heart rate was lower then set rate
• Check the sensitivity on that heart that if under/over are not setting right, should be calibrated
• Atrial pacing, Ventricular pacing, AV Demand -AICD/ICD = (automatic) internal cardiac defibrillator -May see term CRT (cardiac resynchronization therapy)

Review of EKG: Coronary Arteries

• Three coronary arteries: left anterior descending, left circumflex, and right corner artery.

Review of coronary artery perfusion

• LAD perfuses up to 70% of anterior, lateral, and apical wall of left ventricle. It perfuses the anterior two-thirds of septum. Also, most of the right and left bundle branches + the collateral circulation to ant right ventricle and the posterior part of intraventricular septum.

Left Circumflex Artery

• Most of left atrium and posterior and lateral walls of the left ventricle.

Myocardial Ischemia

• Reduced blood flow, detected as T-wave inversion (classically) by EKG
• ST elevated segments,

Myocardial Infarction

• Death of myocardial tissue, through change in EKG
• It has elevated segments for ST and "significant Q wave

Transmural MI

• Is the Q-wave MI with ST depression and Normal segments for T waves

Systematic Approach to EKG Interpretation

• Rate
• Rhythm
• Wave forms + Intervals
• Infarction and Injury
• Axis