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EKG - Supraventricular Arrhythmias
Terms in this set (46)
A tachy arises above the Bundle of His is referred to as......
The QRS complex of a SVT is NORMALLY.......
narrow complex or normal complex
Examples of SVT:
Paroxysmal Atrial Tachy (PAT)
Multifocal Atrial Tachy (MAT)
AV Nodal Reentrant Tachy (AVNRT)
Atrio-Ventricular Reentrant TAchy (AVRT)
In a normal tachy - if the QRS is "broad" or greater than 3 small boxes, this would generally indicate what?
In a normal tachy, if the QRS is "normal", or less than 3 small boxes, this would indicate ......
Once we determine an SVT is present, how can we find out where it originated within the atria?
By analyzing the axis and rhythm
Sinus tachy will come on _______________.
___________ & ___________ can be helpful in the dx and tx or SVT's
Vagal maneuvers & adenosine
methods to stimulate teh vagus nerve in an attempt to slow conduction through the AV node, resulting in slowing of the heart rate
Carotid Sinus Massage
used because carotid sinus so close to anterior surface of neck and baroreceptors can be stimulated by applying pressure, done by physicians when they carefully massage the neck over the carotid sinus in order to slow heart rate in a person who has paraoxysmal superventricular tachycardia which orginates in the atria
- upright P wave in Leads I, II, aVF
- biphasic in III, aVL, V1, V2
- first half of P wave represents right atrial, second half represents left atrial electrical activity
- Rate = 60-100 bpm
- max rate = 220 - age
The intrinsic rate of the SA node is determined by a _____% of SA node cells. ________ channels predominate.
What is the intrinsic rate of the AV node?
*fast and slow pathway
What is the intrinsic rate of ventricular myocytes
What are the two ways to determine rate?
1. when counting between R waves, using the big boxes... --> 300. 150 100. 75, 60, 50....
2. Rate also = # of beats per rhythm strip x 6 (because the full strip should be 10 seconds worth)
Sinus Tachy - appropriate:
- gradual onset and termination
- inhibition of vagal tone
- sympathetic nervous system activation
- caused by hypovolemic shock, anemia, fever, pain, etc
Sinus Tachy - inappropriate:
- abnormalities of vagal tone (dysautonomia)
- postural othrostatic tachy syndrome (POTS): heart rate elevated, bp normal
Sinus Tachy - Denervated Hearts: Post Heart Transplant
- chronic sinus tachy due to severing of the vagus nerve during transplant surgyer
What is focal atrial tachy?
Tachy that does NOT originate with the SA node cells, but rather is of ectopic atrial origin.
1. Rate: 130-250 bpm
2. Rhythm: normal
3. Etiology: enhanced automaticity
Unlike Aflutter, the baseline after a P wave in Atach is.......
isoelectric (gets flat)
Where do most ATACH's originate from?
- the right side
- specifically, the Cristae Terminalis
When the focal point in ATACH originates elsewhere from the SA node (which is higher up in the right atrium), this will cause a depolarization targeted back towards the AV node (superiorly). This will lead to negative P waves in .......
the inferior leads: II, III, aVF
To determine the difference b/t Sinus Tachy and ATACH, what can we look @?
The direction / axis of the P waves!
Specifically look for NEGATIVE P waves:
1. look @ the inferior leads II, III, aVF --> which can indicate that the focal point is coming from the lower part of an atria
2. Look @ the Lateral Leads I, V5, V6 --> which would indicate that the focal ectopic point is within the left atrium!
Multifocal Atrial Tachy is can be characterized by ____________________ P-waves.
three morphologically distinct P waves!
*as well as irregular P-P intervals
Multifical Atrial Tachy:
- rate > 100
- 3 morphologically distinct P waves
- irregular PP intervals
- commonly seen in pt's w/ COPD
AV Nodal Reentrant Tachycarida:
- narrow QRS
- regular rhythm
- sudden onset and termination
- rate = 150-250 bpm
- NO visible P-waves
- responds to vagal maneuvers & adenosine
AV node Pathways:
1. Fast conduction, LONG refractory period
2. Slow conduction, short refractory period
In a normal conduction circuit through the AV node, the impulse travels down the fast pathway and across the AV node, then goes back up the slow pathway where it ......
meets the forward depolarization from that pathway, in effect blocking it from moving further upwards (and back at the atria)
What causes a AVNRT to be initiated?
- Premature Atrial Contraction
- will encounter the refractory period of the fast AV pathway, but will be able to get through the other which has a very short refractory period
- By the time the impulse moves slowly down that pathway, the normal conduction pathway is repolarized and can now go UP this "fast" pathway"
- this can cause a circuit that continues on
We would describe __________ as noting the rhythm is "irregularly irregular", with a lack of clear P waves
*P waves are not really truly visible. We see the presence of small, irregular, fibrillatory oscillations in the atria.
*looks just like a wavy baseline wave b/t QRS complexes
Clinical importance of Afib:
Decreased blood flow in atrium and atrial appendage:
- emoblic stroke
- totally erratic rhythm caused by continuous, rapid rate discharged from numerous automaticity foci
- bpm = 350-450
- ventricular response is controlled by the AV node and if often irregular, with a rate that is variable
Afib's usually arise from.....
parasystolic foci in the pulmonary vein ostia of the left atrium
Aflutter is a rapid, regular, atrial rhythm at an atrial rate of ......
Aflutter P wave oscillations can be described as.....
What is the typical ventricular response to Aflutter?
Common 2:1, but many also 4:1, 3:1
Aflutter waves are best seen in what leads?
II, III, aVF (inferior leads)
Typical Aflutter rotation =
Atypical Aflutter rotation =
Typical Aflutter rotation = counter clockwize
Atypical Aflutter rotation = clockwise
Wolf Parkinson White Syndrome
A pre-exitation syndrome that involves the Bundle of Kent, an accessory pathway of tissue that allows for conduction to pass directly from the atrium to the ventricle, bypassing the AV node
WPW EKG characterisitcs:
- short PR interval, <.12 ms
- "Delta Wave"
- Type A Left Sided: Tall R waves in V1-V3 are Positive Delta Waves
- Type B Right Sided: QS in V1-V3, Negative Delta waves
- QRS seems extended
We can see a delta wave by.....
the SLANT on the initial stroke of the wave in the QRS complex
The detla wave in WPW is recording......
the area of ventricular pre-excitation
Atrioventricular Reentrant Tachycardia (AVRT)
Involves a pathway of impulse conduction outside the AV node and bundle of His. Preexcitation is a term to descibe rhythms that originate from above the ventricles bun travels by a pathway other than the AV node and bundle of His.
Impulse travels anterograde (normally) down AV node and then retrograde back up the accessory pathway to the atria.
- narrow QRS
- retrograde P waves may be visible
Impulse travels anterograde down accessory pathway and then retrograde back up the AV node to the atria.
- wide complex QRS
- Delta waves may be present
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