Arrhythmias and EKG - Pathophysiology

What does this refer

• Are disturbances of the heart rhythm

• Ranges from an occasional “missed” beat or rapid beats to severe disturbances that affect the pumping ability of the heart

• Can be caused by an abnormal rate of impulse generation or an abnormal impulse conduction

Dysrhythmias

What does this refer

• Atrial fib/flutter

• WPW syndrome

• Reentry tachycardia

• Ventricular tach/fib

Tachycardia

What does this refer

• Bundle branch blocks

• AV node block

Bradycardia

What does this refer

“Arrhythmias, bradyarrhythmias, tachyarrhythmias”

AV block

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

What does this refer

• Ectopic beats can be normal, particularly when generated within the atria (premature atrial contraction).

• Ventricular premature contractions can also occur sporadically in the absence of myocardial disease

• Ectopic activity is promoted by hypoxia and ischemia, increased sympathetic tone, hyperkalemia

Ectopic Activity Can Generate Extra Beats

What does this refer

• Conduction blocks

• AV node pacemaker cells are vulnerable to aging, hypoxia

• Common site of partial or complete blocks of propagation—can result in bradycardia due to nonconducted beats

• Focal conduction blocks contribute to reentrant arrhythmias

General Mechanisms of Arrhythmias

What does this refer to “Prolonged PR interval” look at image

Atrioventricular Block—First Degree

What does this refer

• P waves are not all followed by QRS complex, temporary failure of AV conduction

• Mobitz I shows progressive PR lengthening before nonconducted P wave

Atrioventricular Block—Second Degree

What does this refer to

“favored by ischemia, sympathetic nervous system stimulation; common during myocardial infarction”

Increased automaticity

What does this refer to

• Increased automaticity: favored by ischemia, sympathetic nervous system stimulation; common during myocardial infarction

• Triggered activity

• Reentry—facilitated by branching and converging pathways, differing rates of propagation, and ectopic foci

Mechanisms of Tachyarrhythmias

What does this refer

• Sinus beat is conducted along fast pathway to bundle of His

• Slow pathway has refractory section, impulse is blocked

• Ectopic impulse stimulates slow pathway, travels anterograde along His–Purkinje path AND retrograde along fast pathway

• Also known as “circus rhythm”

Reentry in AV nodal reentrant tachycardia (AVNRT)

What does this refer

• Accessory pathway between atria and ventricles can bypass AV node completely, setting up large reentrant circuit

• Without extrasystole, impulse moves anterograde between atria and ventricles—creating delta wave (early rise of QRS complex)

• With ectopic beat, circus rhythm creates tachycardia

Reentry in Wolf–Parkinson–White syndrome

What does this refer

• Most common chronic rhythm disturbance

• No discernible P waves

• Irregularly irregular QRS complexes and pulse

• Associated with aging, atrial enlargement due to hypertension, heart failure, valve disorders

• Common triggers: caffeine, alcohol, lung disease

• Initiated by ectopic foci at junction of atria with pulmonary veins

Atrial Fibrillation

What does this refer

• Inadequate cardiac output—loss of atrial “kick” completing ventricular filling, vulnerability to activity intolerance

• Tachycardia shortens diastole and filling, compromises myocardial oxygenation, vulnerability to ischemia

• Clot formation promoted by atrial blood stasis—major risk factor for transient ischemic attack [TIA] and stroke, managed with anticoagulants

Pathological consequences of atrial fibrillation

What does this refer

• Short runs may be self-limiting

• If sustained—predisposes to ventricular fibrillation

• Mechanisms: increased automaticity, triggered activity, reentry

• Life-threatening consequence of heart disease, ischemia, infarction

• Can occur as a complication of genetic syndromes of ion channel dysfunction

Ventricular Tachycardias

What does this refer

• Congenital dysfunction of fast sodium channel (SCN5A)

• ECG with varying ST elevation

• Potentially life-threatening, may require implanted defibrillator

Brugada Syndrome

What does this refer

• Arise from genetic mutations affecting fast sodium channel or delayed potassium channel—enhancing excitability or delaying repolarization of nonpacemaker action potentials

• Many subtypes with varying degrees of vulnerability to sudden death

• Can precipitate the torsades de pointes form of ventricular tachycardia

• Contraindication to certain medications

Long QT Syndrome

What does this refer to

Atrial fibrillation (Irregularly irregular rhythm, absent P waves)

What does this refer “Sawtooth flutter waves, typically regular”

Atrial flutter

What does this refer to “narrow QRS, rapid rhythm”

Supraventricular Tachycardia (SVT)

What does this refer “Originating near the AV node, absent or inverted P waves”

Junctional Rhythms

What does this refer

“PVCs, Ventricular Tachycardia, Ventricular Fibrillation”

Ventricular Dysrhythmias

What does this refer “Wide and bizarre QRS complexes”

Premature Ventricular Contractions (PVCs)

What does this refer “PVCs alternating with sinus beats”

Ventricular Bigeminy

What does this refer to “sinus rhythm with pairs of PVC’s”

Couplets

What does this refer to “rapid, wide QRS complexes”

Ventricular Tachycardia (VTach)

What does this refer to “Chaotic, irregular waveform with no organized QRS”

Ventricular Fibrillation (VFib)

What does this refer to

Ventricular fibrillation to asytole

What does this refer to “Flatline- no electrical activity”

Asystole

What does this “First, Second (Mobitz I & II), and Third-degree AV blocks”

Heart blocks overview

What does this refer to “Prolonged PR interval, all impulses conducted”

First-Degree AV Block

What does this refer to “Progressive PR prolongation then dropped beat”

Second-Degree AV Block Type I

What does this refer to “Dropped beats without PR prolongation”

Second-Degree AV Block Type II

What does this refer to “Complete dissociation between atria and ventricles”

Third-degree AV block

What does this refer to Electrical activity without mechanical contraction

Pulseless Electrical Activity (PEA)

What does this refer to

• Special vascular system picks up excess fluid and returns it to the venous circulation.

• Moving lymphocytes and leukocytes between different components of hte immune system is another important function

• Has lymph nodes an vessels

• Valves allow one way flow

• Lymphatic veins and venules

• Right lymphatic duct

• Thoracic duct

• Both duct drain into the subclavian

• Afferent and efferent lymphatic vessels

Lymphatic System

What carries lymph to the nodes

Afferent vessels

What carries lymph away from the nodes

efferent

What is a spontaneous impulse generation from a source outside the SA node

Ectopy