Terms in this set (37)
Normal rhythm but rate over >100
It can be Appropriate and Inappropriate
If you just ran up stairs or drank coffee, that would be appropriate
Paroxysmal Atrial Tachycardia (PAT)
Paroxysmal means "off and on"
It comes on quickly and goes off
This is one of the most common things you see
If we wore a holter moniter, 30-40% of us would have this
SVT General Characteristics
Supraventricular tachycardia:It comes from above the ventricles
Narrow QRS Complex (common)
Wide QRS Complex (uncommon): Aberrant conduction in bundle branches. Can Be confused with Ventricular Tachycardia.
Sinus tachycardia will come on gradually:
- this is the key point
Vagal Maneuvers and Adenosine are helpful in diagnosis and treatment.
Supraventricular Tachycardia: Website
The term supraventricular tachycardia (SVT), whilst often used synonymously with AV nodal re-entry tachycardia (AVNRT), can be used to refer to any tachydysrhythmia arising from above the level of the Bundle of His.
Different types of SVT arise from or are propagated by the atria or AV node, typically producing a narrow-complex tachycardia (unless aberrant conduction is present).
Paroxysmal SVT (pSVT) describes an SVT with abrupt onset and offset — characteristically seen with re-entrant tachycardias involving the AV node such as AVNRT or atrioventricular re-entry tachycardia (AVRT).
How are Supraventricular Tachycardias categorized?
SVTs can be classified based on site of origin (atria or AV node) or regularity (regular or irregular).
Carotid Sinus Massage
A massage performed posterior to the mandible
One side only, not bilateral
This presses the vagus nerve which slows the SA node
Slowing down the rate revealed atrial flutter.
Diagnosing Narrow Complex Tachycardia
Irregular rhythm is usually A-fib
1. First step in diagnosing narrow complex tachycardia is seeing if the rhythm is regular or irregular.
2. Further delineation of supraventricular tachycardias can be established according to onset (sudden or gradual), heart rate, and response to vagal maneuvers or administration of adenosine.
AF: atrial fibrillation
AFL: Atrial Flutter
APC: Atrial Premature Contraction
AT: Atrial Tachycardia
AVNRT: Atrioventricular Nodal Reentrant Tachycardia
AVRT: Atrioventricular Reciprocating Tachycardia
HR: Heart Rate
MAT: Multifocal Atrial Tachycardia
NSR: Normal sinus rhythm
ST: Sinus tachycardia
Sinus Rhythm definition
1. Upright P-wave in Leads I, II, aVF
2. Biphasic in III, aVL, V1, V2
3. First half of P-wave represents Right Atrial, second half represents Left Atrial electrical activity.
4. Rate 60-100 bpm
5. Sinus rate varies with respiration slightly
6. Maximum rate = 220 - age: When a stress test is performed, this is how rate is calculated
Intrinsic Rate: SA node
Determined by a mere 1% of SA Node cells. There are few cells, but there is a lot of redundancy in the system.
Rate 60-100 bpm
P-wave on EKG is summation of SA node, atrial muscle, and AV nodal depolarization.
As shown by the colours of the different waves included in a P wave in the image below
Calcium Channels predominate
The wall between the atria is insulated
Buchmann's bundle carries electrical activity from the right to the left atrium
Intrinsic Rate: AV node
Intrinsic Rate 40-60 bpm
If the Sinus node stops working, the AV node can take over
Fast & Slow Pathway: Within the AV node is a fast and a slow pathway. This refers to the rapidity with which they conduct the signal.
Intrinsic Rate: Ventricular Myocytes
Intrinsic Rate < 40 bpm
This paces the heart if the AV and SA nodes stop working
Sinus Tachycardia: Appropriate
Appropriate: (220 - Age= maximal heart rate)
Gradual Onset and termination
1. Inhibition of vagal tone
2. Sympathetic Nervous system activation: Hypovolemia/Shock, Anemia, Fever, Pain, Thyrotoxicosis,
Sinus Tachycardia: Inappropriate
1. Abnormalities in Vagal Tone (dysautonomia)
2. Postural Orthostatic Tachycardia Syndrome (POTS): When standing, the Heart rate is elevated, but blood pressure normal. This is an autonomic problem.
3. Denervated Hearts: Post Heart Transplant. Chronic Sinus tachycardia due to severing of vagus nerve during transplant surgery.
Focal Atrial Tachycardia (ATACH)
Ectopic Atrial Rhythm, Regular Rhythm: Ectopic meaning in the atria but not the SV node
Rate of 130-250 bpm
2. Narrow QRS, normally (can be wide complex): Usually unless there is a bundle branch block. There is also "rate-related bundle branch block" where the heart is going so fast that the bundle branches can't keep up because of their refractory period and develop a left-bundle branch block.
1. Enhanced Automaticity
2. Triggered Activity: Early Afterdepolarization (EAD's)
3. Microreentry Circuit: "don't worry about this stuff"
Isoelectric Baseline between P-waves, unlike Atrial Flutter
This is an important thing
Flutter waves have no flat part between them
distribution of focal points that can become activated in atrial tachycardias
Don't memorize all the percents
Two thirds are from the RA
The remaining third are from the LA
The Crista terminalis is the most common place for atrial tachycardias to orginate from
atrial tachycardia: EKG
Why isn't it SV pacing?
There are P waves but they are inverted
The P waves are coming from low
The rate is about 120 and the rhythm is regular
ATACH with Variable AV Block
1. There are numerous P waves, they are inverted: Note the arrows
2. It's not a flutter because there are flat spaces between them: Some rare flutters can present like this
3. Note the double peaks in V1, V2, V3: This is an AV block, It is a right bundle block.
How do we know these are p waves and not t waves? The p waves are the same and equally spaced
Multifocal Atrial Tachycardia (MAT): Definition, who is it commonly seen in, how do you treat it?
MAT is a rhythm of patients with COPD, the heart rate is over 100 per minute with P' waves of various shapes, since three or more atrial foci are involved.
3 morphologically distinct P-waves: Multiple foci in the atria are pacing
Irregular P-P intervals: This can be confused with A-fib sometimes
Commonly seen in patients with acute pulmonary issues (COPD)
Treat the underlying cause
Betablockers, Calcium channel blockers
AV Nodal Reentrant Tachycardia (AVNRT): What is it?
This one is easy to fix. Giving adenosine corrects the problem. "you will feel good" when you treat a patient with this due to the ease.
A theoretical "reentry circuit" may continuously circle (like perpetual motion) through the AV junctional region, giving off a depolarization stimulus to the atria and to the ventricles with each pass in the circuit rapidly pacing the atria and the ventricles.
AV Nodal Reentrant Tachycardia (AVNRT): EKG
1. Narrow QRS Complex
3, Sudden onset and termination
4. Coughing can cause or break it: Give adenosine and the problem is fixed
5. Rate: 150-250 bpm
6. No visible P-waves, except possible retrograde P-waves present.
7. Look at baseline EKG for Pre-excitation (Wolf-Parkinson-White)
8. Responds to vagal maneuvers and Adenosine
Normal AV-node conduction
In the image below on the left, the normal AV-node conduction is illustrated. The AV node has a fast and a slow pathway, both of which conduct downward. In normal conduction, an impulse travels down the fast pathway first. Concurrently, it also begins to conduct down the slow pathway. In the ventricle, the impulse from the fast pathway tries to go up the slow pathway but is blocked by the impulse coming down.
AV Nodal Reentrant Tachycardia (AVNRT): Mechanism
Down the SLOW, up the FAST
Slow Pathway: Short refractory
Fast Pathway: Long refractory
Narrow QRS complex, 150-250 bpm, Possible Retrograde P-waves
Rapid onset and termination
The impulse travels down the slow pathway first. It then travels up the fast pathway. During this time, the slow pathway has already gone through its short refractory period. Back in the atrium, it travels back down the slow pathway. The slow pathway gives the fast pathway time for its long refractory period.
Atrial Fibrillation (AFIB)
Caused by continuous rapid-firing of multiple atrial automaticity foci. No single impulse depolarizes the atria completely, and only an occasional, random atrial depolarization reaches the AV node to be conducted to the ventricles, this produces an irregular ventricular rhythm. NO P waves.
Disorganized, No P waves visible and "Irregularly Irregular" - there is no rhythm. Presence of small, irregular, fibrillatory oscillations in the atria.
Arise from Pulmonary veins in significant portion of patients. Somehow, atrial tissue develops in the pulmonary veins. Ventricular rate variable, 30-200 based on AV nodal conduction (Medications...).
If the ventricular response is regular, think of high grade AV Block (Junctional Escape Rhythm)
"this is why they created cardiologists"
Clinical Importance of AFIB:
Decreased blood flow in atrium and atrial appendage.
Leads to thrombus
Leads to Embolic Stroke
Rhythm of Afib
A-fib is irregularly irregular
If the heart rate is high enough, it can appear regular
Atrial Flutter: Definition
Rapid, Regular, atrial rhythm at an atrial rate of 200-400 beats/min.
Ventricular response is commonly 2:1, but may be 4:1,3:1, and rarely 1:1
2:1 meaning that for every 2 P-waves, there is a QRS
1:1 conduction leads to hemodynamic instability.
Flutter waves best seen in II, III, aVF and V1
Atrial flutter is a type of supraventricular tachycardia caused by a re-entry circuit within the right atrium.
The length of the re-entry circuit corresponds to the size of the right atrium, resulting in a fairly predictable atrial rate of around 300 bpm (range 200-400). Ventricular rate is determined by the AV conduction ratio ("degree of AV block"). The commonest AV ratio is 2:1, resulting in a ventricular rate of ~150 bpm. Higher-degree AV blocks can occur — usually due to medications or underlying heart disease — resulting in lower rates of ventricular conduction, e.g. 3:1 or 4:1 block. Atrial flutter with 1:1 conduction can occur due to sympathetic stimulation or in the presence of an accessory pathway — especially if AV-nodal blocking agents are administered to a patient with WPW. Atrial flutter with 1:1 conduction is associated with severe haemodynamic instability and progression to ventricular fibrillation.
Atrial Flutter orginates in an atrial automaticity focus. The rapid succession of identical, back-to-back atrial depolarization waves, "flutter" waves, suggest a reentry origin to some experts. In atrial flutter an extremely irritable atrial automaticity focus fires at a rate of 250-300 per minute, producing rapid series of atrial depolarizations. On EKG, atrial flutter is characterized by consecutive identical "flutter" waves in rapid back-to-back succession. The baseline appears to vanish between the back to back flutter waves.
Typical Atrial Flutter (Common, or Type I Atrial Flutter)
Involves the IVC & tricuspid isthmus in the reentry circuit. Can be further classified based on the direction of the circuit:
Anticlockwise Reentry. This is the commonest form of atrial flutter (90% of cases). Retrograde atrial conduction produces:
Inverted flutter waves in leads II,III, aVF
Positive flutter waves in V1 - may resemble upright P waves
Clockwise Reentry: This uncommon variant produces the opposite pattern:
Positive flutter waves in leads II, III, aVF
Broad, inverted flutter waves in V1
Atypical Atrial flutter (Uncommon, or Type II Atrial Flutter)
Does not fulfill criteria for typical atrial flutter.
Often associated with higher atrial rates and rhythm instability.
Less amenable to treatment with ablation.
ATRIAL FLUTTER 2:1 Conduction
For every two atrial conductions, there is a QRS
Atrial Flutter 3:1 Conduction
ATRIAL FLUTTER 12:1 Conduction
In the ekg below, the patient has a ventricular rate of 24 bpm
This patient needs a pacemaker
Adenosine would cause this patient's blood pressure to drop too low
Wolf-Parkinson-White Syndrome (WPW): Pre-excitation syndrome
Accessory pathway of tissue, The Kent Bundle, that directly connects the atrium and ventricle, bypassing the AV Node
Called a Bypass Tract, remnant of embryonic tissue
Short PR interval (<0.12 ms)
It causes a "Delta Wave"
Wolf-Parkinson-White Syndrome (WPW): Mechanism
Conduction happens through a secondary pathway allowing one ventricle to receive two impulses to contract.
One impulse from the AV node through the bundle of his and a second impulse through the secondary pathway
The PR-interval is very short
Case: 65 yo Male with Palpitations...
The patient has AFIB with WPW
This patient would need to be shocked quickly
Atrioventricular reentrant Tachycardia (AVRT): Notes
This is the largest of all re-entry circuits. AVRT are further divided in to orthodromic or antidromic conduction based on direction of reentry conduction and ECG morphology.
The impulse travels down, through the ventricles, then passes back through a retrograde pathway and starts again
This is orthodromic
Antidromic is the same, but backwards
"Don't lose sleep over these"
"I won't give an ekg of this on the test"
Antidromic vs. Orthodromic
Will be narrow QRS complex
Retrograde P-waves may be visible
Travels down AV Node then retrograde via the bypass tract
Impulse travels down bypass tract first, then retrograde activation of AV Node
Wide complex QRS