Conduction disorders pt. 1 - Clin Med

What does this refer to “Orderly passage of electrical current sequentially through the heart muscle”

Depolarization

What is the Process allowing the muscle cells of the ventricles to regain their ability to depolarize again

Repolarization

What does this refer to

• Cell is more negative inside

• Na+ outside/ K+ inside

Rest

What does this refer to

• Na+ enters

• K+ exits

Depolarization (contraction)

What does this refer to

• Na+ exits

• K+ returns

Repolarization (relaxation)

What is the direction of movement of depolarization

• Measured in degrees, from 0 (horizontal) to +90 (vertical) and -90 (inverted)

• Remember – the ventricles depolarize simultaneously

  • Contraction = QRS

• Look at leads I and aVF

EKG Axis

What does this refer to

• Represents an average of the instantaneous electrical charge during the sequence of ventricular depolarization

• Movement of electrical charge

• Tells us the average direction of the depolarization wave

• Spreading wave of electrical activity in the heart

  • Causes ventricular activation

QRS Axis

What does this refer to? R>S

Positive

What does this refer to ? R = S

Equiphasic

What does this refer to S > R

Negative

What is the Axis if Lead 1 is positive and aVF is positive

Normal

What is the Axis if Lead 1 is positive and aVF is negative

LAD

What is the Axis if Lead 1 is Negative and aVF is positive

RAD

What is the Axis if Lead 1 is negative and aVF is negative

Extreme RAD or extreme LAD

What does this refer to

• Normal variant in young, healthy people

• Often due to changes in vagal influence on the sinus node

• Irregularity of the normal heart rate

• Variation in the PP interval of > 120 ms

Sinus arrhythmia

What does this refer to

• Heart rate slower than 60 beats per minute

• May be due to vagal influence on the SA node

• May be due to organic disease of the sinus node

• Significance

  • Young people?

  • Elderly?

• Severe bradycardia

  • AV node or Bundle of His take over

    • Rates 35-60

Sinus Bradycardia

What does this refer to

and TSH

Workup for Sinus Bradycardia

What does this refer to

Event monitoring

What are you looking at

Loop recorder

What does this refer to

• Varies based on etiology BUT important question to ask is MEDICATION LIST?

• May be as simple as stopping a medication that has SE of bradycardia OR

• May require pacemaker or other device

Clinical management of Sinus Bradycardia

What does this refer to

Pacemaker

What does this refer to

Left ventricular assist device (lvad)

What does this refer to

• Heart rate faster than 100 beats per minute

• Due to rapid impulse formation from the SA node

• In line with physiologic demands —> appropriate

• Inappropriate

Sinus Tachycardia

What does this refer to

Appropriate tachycardia triggers

What does this refer to

• Sensation of a rapid heartbeat (palpitations), which may be uncomfortable

• Shortness of breath

• Dizziness

• Fainting

• Chest pain

• Anxiety

• Headaches

• Decreased ability to exercise

Clinical history of Inappropriate Sinus Tachycardia

What does this refer to

• EKG

• Continuous monitoring of the heart rhythm (Holter/patch)

• CBC w. diff, CMP, thyroid panel

• Echocardiogram

• Chest X-ray

Workup for Sinus Tachycardia

What does this refer to

• Eliminate potential triggers or stimulants —> lifestyle changes

• Beta-blockers

  • Metoprolol 1st line

• Catheter ablation

  • Refractory cases - persistent symptomatic inappropriate sinus tachycardia despite optimal pharmacologic therapy, radiofrequency catheter ablation

    • Rarely performed

Clinical management of Sinus tachycardia

What does this refer to

• Not a specific disease, but rather a group of signs or symptoms + EKG changes that indicate the sinus node, the heart's natural pacemaker, is not functioning properly

  • Bradycardia

  • Sinus pauses

  • Sinus arrest

Sick Sinus Syndrome

What does this refer to

Sick Sinus Syndrome

What does this refer to

• Occurs as a result of disease in the sinoatrial (SA) node

• May cause tachycardia-bradycardia syndrome

• Rate varies from fast to slow and back again

• May manifest as syncope

Sick Sinus Syndrome

What does this refer to

• Age greater than 65

• 1/600 patients

• Accounts for one-half (1/2) of all pacemaker implantations

Epidemiology Sick Sinus Syndrome

What does this refer to

• Sinus Node Disease

• Scarring

Etiology of Sick Sinus Syndrome

What does this refer to

1. Periods of inappropriate, and often severe bradycardia

2. Sinus pauses, arrest, and sinoatrial (SA) exit block with, and often without, appropriate atrial and junctional escape rhythms

   1. Failure of escape pacemakers may lead to symptoms including syncope

3. Alternating bradycardia and atrial tachyarrhythmia in over 50% of cases

   1. Atrial fibrillation is most common

   2. Atrial flutter and paroxysmal supraventricular tachycardia (ie, due to atrial tachycardia) may also occur

EKG of Sick Sinus Syndrome

What does this refer to

Sick Sinus Syndrome (no consistent P waves)

What does this refer to

Sick Sinus Syndrome

What does this refer to

• Fatigue

• Lightheadedness

• Palpitations

• Presyncope/syncope

Clinical history of Sick Sinus Syndrome

What does this refer to

• CBC w/ diff

• CMP

• Magnesium

• Cardiac biomarkers and EKG

• CXR

• Echocardiogram

• Stress Test

• Left heart cath

Workup for Sick Sinus Syndrome

What does this refer to

• Cardiology referral

• Holter Monitor

• Event Recorders

Clinical intervention of Sick Sinus Syndrome

What does this refer to

• Remote monitoring

• Records electrical activity of the heart

• Sx should correlate with arrhythmias

Event recorders for Sick Sinus Syndrome

What does this refer to

• No tx for asx patients

• Bradycardia

  • Atropine

    • Emergent tx for symptomatic patient

  • Chronic bradycardia

    • Pacemaker

• Tachycardia

  • Beta-blockers OR CCB

  • Antiarrhythmic if symptomatic

Clinical Management of Sick Sinus Syndrome

What does this refer to

• ____________

  • Extra heart beat

  • Originates in the atria

• P wave is present and the QRS is narrow

• P wave usually has a different morphology from sinus node beats

Premature Atrial Contraction (PAC)

What does this refer to

• _____________________

  • Extra heart beat

  • Begins in either the Right or Left Ventricle

• Also known as

  • Ventricular Premature Beats

  • Extrasystoles

  • Premature Ventricular Complexes

Premature Ventricular Contraction (PVC)

What does this refer to

• 1-4% of the general population

• More common (up to 69%) of patients 75 yo or older

• MC African Americans with HTN

• Males > Females

Epidemiology of Premature Beats

What does this refer to

• Alcohol/Tobacco/Illicit drug use

• Anemia

• Anxiety

• Caffeine

• Exercise

• Heart disease/Hypertension

• Some medications → decongestants

• Hypercalcemia/Hypokalemia

• Hypomagnesemia

Etiology of Premature Beats

What does this refer to

Premature Atrial Contraction (PAC)

What does this refer to

Premature ventricular complex

What does this refer to

• Characterized by Frequency

  • Isolated

  • Bigeminy

  • Trigeminy

  • “Runs of V-Tach”

• Characterized by location of origin = morphology

  • Monomorphic PVC

  • Polymorphic PVC

Classification of Premature Ventricular Contractions (PVC)

What does this refer to

Monomorphic PVC

What does this refer to

Polymorphic PVCs

What does this refer to

Polymorphic PVC

What does this refer to

Trigeminy PVC

What does this refer to

Bigeminy PVC

What does this refer to

Run of V-tach (VT) PVC

What does this refer to

Non-sustained V-tach

What does this refer to

• Skipped beat/Palpitations

• Lightheadedness

• Chest Pain

• Near Syncope

• Generalized fatigue

Clinical history of Premature beats

What does this refer to

• May be symptomatic if increased frequency of PVCs

  • Pale

  • Diaphoretic

  • Occasionally irregular heart rate

Physical exam for Premture Beats

What does this refer to

• 12 lead EKG

• CBC with Diff

• CMP

• Cardiac Biomarkers

• Drug Screen

• CXR

• Holter Monitor

  • 24-48 hours

Workup for Premature Beats

What does this refer to

• Elimination of triggers

  • Caffeine/Alcohol/Drugs

• Electrolyte Replacement

• Antiarrhythmics

• Beta-blockers

• Calcium Channel Blockers

• Radiofrequency Catheter Ablation

Clinical management for Premature beats

What does this refer to

• In the absence of severe heart disease/Morbidities

  • Excellent recovery/prognosis

• Asymptomatic with decreased EF have 3.5% increased incidence of sudden cardiac arrest/death

Prognosis of Premature beats

What does this refer to

“If the R is far from P”

1st degree AV Block

What is the max the distance of R and P should be

0.20

What does this refer to

First degree block

What does this refer to

• A 20-year-old man presents to his primary care physician for an annual exam.

• He is currently feeling well but has some concerns since he occasionally has palpitations.

• Medical history is unremarkable and he takes a daily multivitamin.

• He denies any alcohol or smoking history.

• Family history is significant for his paternal grandfather expiring from a fatal arrhythmia.

• He is a college student and part of the school's basketball team, which he continued since he was a student in high school.

• He says that his caffeine intake has increased in these past few weeks due to upcoming final examinations.

• He is requesting an electrocardiogram (ECG) to ensure his heart is healthy since this worry is interfering with his schoolwork.

• An ECG demonstrates a PR interval of 0.25 sec and is otherwise unremarkable.

First degree block

What does this refer to

• Depolarization waves are not conducted normally to the ventricles through the atrioventricular node.

• Types of Blocks

  • First (1st) degree (1°)

  • Second (2nd) degree (2°)

  • Third (3rd) degree (3°)

1st degree block

What does this refer to

• Up to 1.6% of young adults affected

• Higher prevalence in trained athletes

• 5% of persons > 60 yo affected

• AA > Caucasians

• M > F

Epidemiology of 1st Degree Block

What does this refer to

• Physiologic OR Pathologic

• Damage to the AV node

  • Ischemia/infarction

  • Inflammatory disorders

  • Infiltrative disorders

  • Postoperative

• Generally associated with organic heart disease

  • May also be seen in Inferior MI Patients

• Medication induced

  • Digoxin/BB/CCB

• Electrolyte imbalance

Etiology of 1st degree block

What does this refer to

• P wave

  • atrial depolarization

• Upright and rounded

• Normal duration-0.04-0.11 seconds (definitely not greater than_____?)

• P waves that have normal size and shape signal to us that the impulse is originating in the SA node

P wave review of 1st degree block

What does this refer to

• PRI (PR interval)

  • Time to travel from atria through AV node, bundle of His and bundle branches to Purkinje fibers

• Measured from beginning of P wave to beginning of QRS

• Normal duration 0.12-0.20 seconds

PR Interval of 1st degree block

What does this refer to

• May be asymptomatic

• Symptoms usually vague, including palpitations and dizziness

• Bradycardia may present with lightheadedness or syncope

History and physical exam of 1st degree block

What does this refer to

• No pathognomonic physical findings

• Occasional irregular pulse

• Loss of atrial and ventricular synchronization

Pertinent physical exam findings of 1st Degree Block

What does this refer to

• Sinus bradycardia

• Sick sinus syndrome (tachy-brady syndrome)

• Effects of negative chronotropic substances (i.e. beta-blockers)

Differential Diagnosis of 1st degree block

What does this refer to

Workup for 1st degree block

What does this refer to

• EKG is usually diagnostic of atrioventricular conduction disorders.

• 1° block

  • Delayed conduction through the AV node

  • Produces a PR interval greater than 0.20 seconds.

• PR-I should be < 0.20 seconds

• Rate: Typically 60-100

• Rhythm-Typically regular

• QRS-follows each p wave and is typically normal

Diagnostic evaluations of 1st degree block

What does this refer to

First Degree AV Block

What does this refer to

• Consult/referral to cardiology

• Asymptomatic

  • Treatment typically not required

  • Observation of patient???

Clinical Intervention of 1st degree block

What does this refer to

• May be viewed as a warning signal to future development of more serious AV Blocks

Prognosis of 1st degree block

What does this refer to

2nd degree AV Block

What does this refer to

• Conduction through the AV node is intermittent

• Divided into two subclasses

  • Mobitz I —> Wenckebach

  • Mobitz II

• Rate: 30-55 beats a minute

2nd degree block

What does this refer to

• M = F

• 3% of patients with structural heart disease will develop 2nd degree AV block

Epidemiology of 2nd Degree Block

What does this refer to

• Cardioactive drugs are an important cause of AV block

• MS drug Fingolimod (Gilenya)

• Various inflammatory, infiltrative, metabolic, endocrine, and collagen vascular disorders have been associated with AVblock

Etiology of 2nd Degree Block

What does this refer to

• Characterized by a cycle of increasingly lengthened PR intervals followed by a missed QRS complex

• Each P wave gets farther away from its QRS till eventually a P wave is not conducted thru the AV node (Blocked) and a QRS is lost

• Lone wolf P Wave

2nd Degree Mobitz I (Wenckebach)

What does this refer to

Workup for 2nd Degree Mobitz I (Wenckebach)

What does this refer to

Clinical Management for 2nd Degree Mobitz I (Wenckebach)

What is characterized by occasional non-conducted P waves not preceded by lengthened PR intervals

2nd Degree Block Mobitz II

What does this refer to

• PRI prolonged but constant

• Dropped QRS

• Everything seems to be going fine then wham

2nd Degree Block Mobitz II

What does this refer to

• 1st degree AV Block

• 2nd degree AV Block

• 3rd degree AV Block

• SSS

• Sinus bradycardia

Differential Diagnosis of 2nd Degree Block Mobitz II

What does this refer to

• Serious as may lead to Syncope

• Management:

  • Cardiology Consult

  • Atropine

  • Temp. Pacing

• Definitive Treatment: Pacemaker Implantation as may progress to 3rd degree

2nd Degree Block Mobitz II

What does this refer to

“PR intervals gradually elongate until a P-wave is completely blocked

Mobitz Type 1

What does this refer to

“PR Intervals are consistent but some P-waves don’t conduct”

Mobitz Type II

What does this refer to

3rd Degree AV Block

What does this refer to

• No conduction is taking place through the AV node.

• Typically, atrial and ventricular depolarizations take place at their intrinsic firing rates with no relation to one another.

• P waves are not associated with QRS—cardiac output insufficient

3rd Degree AV Block

What does this refer to

• Atria continued to be paced by their respected SA node

• See a typically normal P wave rate but, a slower QRS rate.

3rd Degree AV Block

What does this refer to

• Patients may present with hemodynamic instability secondary to bradycardia.

• Transcutaneous or transvenous pacing should be initiated until a permanent pacemaker can be placed.

Emergency management of 3rd degree AV block

• What does this refer to
  Acute Symptomatic-Temporary Pacing until Permanent Pacemaker placed

• Definitive Treatment: Implantable pacemaker

Clinical Management of 3rd Degree AV Block

What does this refer to

“________ carry the signal from just below the AV node (the junction between the top and bottom chambers of the heart) through the ventricles (bottom of the heart).”

Bundle branches

What does this refer to

Left bundle branch block

What does this refer to

Right bundle branch block

What does this refer to

• Problem with the right branch of the conducting system that sends the electrical signal to the RV

• Impulse still gets to the RV but it has to travel to the left side before getting to the RV

Right Bundle Branch Block (RBBB)

What does this refer to

• The sino-atrial node acts as the initial pacemaker

• Depolarization reaches the atrioventricular node

• Depolarization through the bundle of His occurs only via the left bundle branch.

  • Left branch still depolarizes the septum as normal.

• The left ventricular wall depolarizes as normal.

• The right ventricular walls are eventually depolarized by the left bundle branch, this occurs by a slower, less efficient pathway.

Pathophysiology Right Bundle Branch Block (RBBB)

What does this refer to

• EKG Diagnostic Criteria

  • QRS duration > 120ms

  • RSR’ pattern in V1-3 (“M-shaped” QRS complex)

  • Wide, slurred S wave in lateral leads (I, aVL, V5-6)

EKGRight Bundle Branch Block (RBBB)