Lecture 5 8/23/24 Flashcards
How does the shape of the QRS complex vary based on origin?
supraventricular origin: narrow
ventricular origin: wide, bizarre
What is tachyarrhythmia?
any deviation from sinus rhythm that is characterized by rapid rate
What does the term supraventricular refer to?
atrial and junctional depolarizations
Why does supraventricular tachyarrhythmia present with a narrow QRS?
depolarization arises proximal to the bifurcation of the bundle of His
What are the characteristics of supraventricular premature complexes?
-occur early
-have a narrow QRS
-associated with diseases that cause atrial distention
What are the characteristics of supraventricular tachycardia?
-usually regular
-start and stop abruptly
-QRS narrow
-3 or more early complexes
-pathologic, not physiologic
What are the characteristics of atrial fibrillation?
-rapid
-irregular
-monomorphic w/ narrow QRS
-no P waves
-abrupt RR interval changes w/ no pattern
-associated with diseases that result in atrial distention
Why is atrial fibrillation only seen in larger animals?
the heart has to be large in order for atrial fib. to develop
What are the characteristics of ventricular premature complexes?
-occur early
-wide and bizarre QRS
-associated with structural heart disease or non-cardiac disease (dogs)
-no P wave
What are the characteristics of ventricular tachycardia?
-three or more successive ventricular ectopic complexes at a rapid rate
-regular
-initiated by a ventricular premature complex
-associated with structural disease
What is the significance of ventricular tachycardia?
-can cause signs of low output
-can degenerate to ventricular fib.
-prodrome of severe myocardial dysfunction
What extra-cardiac diseases can cause ventricular tachyarrhythmia?
-trauma
-GDV
-splenic disease
-neurologic disease
-sepsis
What are the potential etiologies of ventricular tachyarrhythmia in extra-cardiac disease?
-autonomic factors
-electrolyte disturbances
-acid-base disturbances
How do ventricular tachyarrhythmias in extra-cardiac disease differ from those caused by cardiac disease?
-slow/less than 160 bpm
-initiated by late diastolic ventricular complexes
-well tolerated by patient
-electrically benign
-resolve spontaneously
What is a 1st degree AV block?
PR interval prolongation
What is a 2nd degree AV block?
-intermittent failure of AV conduction
-one or more P waves fails to conduct to ventricles
What is a 3rd degree AV block?
-complete failure of AV conduction
-slow idioventricular “escape rhythm” is responsible for wide QRS complexes that are independent of atrial depolarizations
What are the potential types of 2nd degree AV block?
-functional/related to elevated vagal tone
-AV node disease
What are the characteristics of high grade 2nd degree/3rd degree AV block?
-results from intrinsic conduction system disease
-causes syncope and/or exercise intolerance
-can cause CHF and sudden death
-results from idiopathic fibrosis
-associated with myocardial disease and aortic valve endocarditis
-important indication for cardiac pacing
What are the characteristics of sick sinus syndrome?
-sinus pauses or bradycardia
-manifest as syncopal episodes
How does severe hyperkalemia impact the heart?
-bradyarrhythmia
-wide QRS
-low amplitude/absent P waves
-peaked T waves
What are the consequences of arrhythmias?
-syncope and possible sudden death
-poor perfusion in critically ill patients
How are arrhythmias treated?
-pharmacologically for tachyarrhythmias
-cardiac pacing for bradyarrhythmias
