Brady and tachy dysrhythmias Flashcards
What does altered impulse formation with enhanced automaticity lead to?
Tachyarrhythmias
What does altered impulse formation with decreased automaticity lead to?
Bradyarrhythmias
What does altered impulse conduction with reentry (stimulation of different portions of cardiac tissue) lead to?
Tachyarrhythmias
What does altered impulse conduction with conduction blocks lead to?
Bradyarrhythmias
What is the definition of bradycardia?
HR <60bpm
What are some aetiologies of sinus bradycardia?
Normal aging
AMl, especially those affecting the inferior wall of the heart
Hypothyroidism, infiltrative diseases (sarcoid, amyloid)
Hypothermia, hypokalemia
Situational (micturation, coughing)
Drugs (beta-blockers, digitalis, calcium channel
blockers, amiodarone, lithium)
Describe extreme bradycardia and likely pt presentation
HR <40
Rarely physiological this requires immediate rx
Presentation would include ALOC, poor perfusion, and hypotension
What is the presentation of symptomatic bradycardia?
Syncope/pre-syncope Dizziness SOB Chest pain ALOC
When externally pacing is it important to ensure the pulse correlates with or opposes the paced rhythm?
Correlates with
External pacing is only considered when…
Pharmacological agents are ineffective
What is the rate of less severe bradycardia?
HR 40-60
When does less severe bradycardia require immediate rx?
Systolic BP <90mmHg
Ventricular dysrhythmia
Hx of heart failure
Describe bradycardia due to 1st degree AV block
PR interval >0.2 seconds
High risk of progression to 2nd/3rd degree block if accompanied by a wide QRS
Benign if asymptomatic
What drug can cause 1st degree AV block?
Calcium channel blockers
What is 2nd degree AV block type 1? (Mobitz type 1; Wenckebach)?
Progressive PR longation with eventual non-conduction of a P wave (may be 2:1 or 3:1)
Describe the effect of Mobitz type 1 on patient presentation
Usually asymptomatic but with accompanying bradycardia can cause angina and syncope (may need pacing)
What are some risk factors/causes of Mobitz type 1?
Elderly Long distance runners Beta blockers Calcium channel blockers Digoxin
What is the ECG effect of 2nd degree AV block type 2 (Mobitz type 2)?
Normal PR intervals with sudden failure of a P wave to conduce
What is Mobitz type 2 usually accompanied by?
Bundle branch or fascicular block
Mobitz type 2 often causes ___.
Syncope
What worsens the signs of Mobitz type 2?
Exercise
Does Mobitz type 2 generally need pacing?
Yes
What is 3rd degree AV block?
Completely AV dissociation
The HR in 3rd degree AV block is ____.
Note: word, not bpm
Ventricular
What are some common results of 3rd degree AV block?
Dizziness
Syncope
Angina
HF
3rd degree AV block can degenerate into…
VT and VF
Does 3rd dergee AV block need pacing?
Yes
What are some aetiologies of sinus tachycardia?
Fever Hyperthyroidism Effective volume depletion Anxiety Pheochromocytmoa (adrenal tumour) Sepsis Anaemia Stimulant exposure Illicit drugs Hypotension Shock Pulmonary embolism Acute coronary ichaemia AMI HF Chronic pulmonary disease Hypoxia
What are the S&S of tachycardia?
Syncope/near syncope (depending on the rate)
Dizziness
SOB
Chest pain/palpitations
What is ‘paroxysmal’ SVT?
Unpredictable
True or false: Onset and termination of paroxysmal SVT is usually gradual
False: both are abrupt
What does AVNRT stand for?
Atrioventricular nodal reentrant tachycardia
Describe the pathway of AVNRT
SA node fires normally
Charge splits into two pathways at the AV node, one fast that goes through the ventricles and one slower that cannot follow into the refractory period so it circles back up into the AV node
AVNRT has a ____ QRS and a HR of ____.
Narrow, >100
The abnormal circuit in AVNRT directly involves the ____ ____.
AV node
What is a ‘typical’ AVNRT pathway?
Impulse travels over the slow pathway towards the ventricles and returns via the fast pathway
What happens to the retrograde P wave in AVNRT?
It is lost in the QRS complex
What are the AVNRT mx points?
Valsalva manoeuver
Pharmacological agents (adenosine)
Cardioversion (CCP)
Ablation (cauterising the pathway; dependent on frequency)
How does the valsalva manoeuvre assist AVNRT?
Stimulates the vagus nerve to enter reflex bradycardia
What does AVRT stand for?
Atrioventricular re-entry tachycardia
What is AVRT?
A normal pathway and an abnormal loop of electricity/circuit
What are the ECG changes in AVRT?
Shortened PR interval Delta wave (slow rise of QRS)
What are the two pathways of AVRT?
AV conduction pathway
Accessory pathway between the atria and ventricles
What is an example of AVRT?
Wolff-Parkinson White syndrome
What other arrhythmias can use an accessory pathway for conduction of tachycardia origin to other heart regions?
AF and atrial flutter
What is the rx for a pulseless tachycardic pt?
Rx as CA
What are the two possible rhythms behind regular broad complex tachycardia?
Ventricular origin or SVT with aberrant conduction (BBB)
What do you do if you cannot determine which underlying rhythm is behind broad complex tachycardia, and why?
Treat as VT, because it is less harmful than incorrectly rx VT as SVT
What is the most likely cause of irregular broad complex tachycardia?
Uncontrolled AF with a BBB
What is it important not to rule out with irregular broad complex tachycardia?
AF with WPW, and Torsades de Pointes
Regular narrow complex tachycardias include what three rhythms?
Sinus tachycardia
AVNRT
AVRT
What is the rx for regular narrow complex tachycardia?
Valsalva manoeuvre
Adenosine (some services)
Cardioversion (CCP)
What rhythms are likely to be the cause of irregular narrow complex tachycardia?
Controlled AF, or atrial flutter with a variable AV block
