EKG interp, Ventricular dysrhythmias, AV blocks and med mgmt Flashcards
Atrioventricular Blocks (AV blocks)
- A delay or failed conduction of impulses from atria to ventricles
- Can occur in the AV node, Bundles of HIS and the bundle branches
- QRS will be normal at or above the bundles of his
- It is common to see rabbit ears in these patients: LBBB, can have a notching, or second peak of the R wave
Normal QT interval
0.4-0.43 sec
Normal R-R interval
0.6-1.0 seconds
60-100 bpm
AV blocks: Left bundle branch block
- Notching of the R wave can hide a STEMI
- Treat as if they have ACS unless proven otherwise
First degree block
- Signals are delayed in the AV node but are conducted to the ventricles
- PR interval over 0.2 seconds, consistent
- QRS is normal (0.1 or less)
- Atrial and ventricular rate is the same
Second degree block
- Mobitz I and Mobitz II, some impulses are conducted to the ventricles and some are blocked
*
Third degree AV block
All impulses are blocked and non are conducted to the ventricles
* P wave and QRS are independent of each other
* P waves appear across the rhythm strip hiding in QRS, ST or T wave, Consistent across the strip
* Inconsistent PR interval
* Atria rate higher than ventricular rate
* regular atrial and ventricular rhythm, just not together
How to determine the AV block
- Look for the P waves: (Is there one for each QRS or is there more than one?)
- Measure the regularity of the atrial rhythm (P-P interval) and the ventricular rhythm (R-R interval)
- Measure the PR interval (is it consistent?)
3.5 The PR is key to identifying the type of block - Measure the QRS complex
- Is it narrow or wide
- The lower the block in the conduction system, the wider the QRS and the slower the rate
How do you manage a first degree block
- You don’t, you just watch them to make sure they dont get worse, note in the chart
- Make sure the pt is stable
Second degree AV block: Mobitz I
- longer, longer, longer, drop now you have a wenckebach
- Each impulse has increasing difficulty passing through the AV node, until one impulse does not pass through and is blocked (PR interval increases more and more until a QRS complex is dropped)
- P wave is regular and occurs on schedule
- After a beat is dropped, the cycle repeated
- Ventricular rhythm is irregular due to the beat being dropped
- AV block is conducted through the AV node so QRS duration is normal
Mobitiz I mgmt
- If stable, no treatment
- Seen as intermittent benign rhythm
- Usually temp and resolves spontaneously
Causes of Mobitz I
- Acute inferior wall MI: From ischemia of the AV node
- Meds affecting rate and rhythm (CCB, BB, Dig)
- Hyperkalemia
Second Degree AV block: Mobitz II
- Failure of some SA impulses to be conducted through the AV node to the ventricles
- More than one P wave for each QRS complex
- PR ratio is the consistent however some impulses do not conduct resulting in more than one P wave per QRS complex
- Conduction disorder may be located in bundles of his or bundle branches
The PR ratio is huge
Mobitz II: Block is located in bundles of His
QRS complex is normal duration
Mobitz II: Block is located in the bundle branches
QRS is wide
Complications of Mobitz II
Potential to progress to third degree AV block or ventricular standstill with little to no warning
Causes of Mobitz II
- Anterior wall MI
- Acute myocarditis
- Degeneration of electrical conduction system occurring with aging
Mgmt of Mobitz II
- Address reversible causes first
- Pacemaker therapy, due to this block often being perm and its progression to third degree AV block
- External pacing is done for symptomatic Mobitz II until transversal pacing can be done
Atropine is not recommended especially if the QRS complexes are wide as it can further slow down rate
Reversible causes of nodal blocks: Mobitz II
- Medications: Dig, beta adrenergic blockers, CCB
- Electrolyte imbalances (hyperkalemia
- AV block due to a heart condition would make you adress the heart condition
Atropine
- Works on the SA node to increase HR in bradycardic patients
- Does not work on Mobitz II and below with the bundle branches , as it can worsen heart blocks
Third Degree AV Block: Block is located in the AV node or bundles of His
- QRS will be narrow
- Ventricular rate between 40-60
Third Degree AV Block: Block is located in the R/L bundle branches
- QRS is wide
- Ventricular rate less than 40
Atropine is not recommended
mgmt of third degree heart block
- External pacing can be used for Temp treatment of symptomatic complete heart block until transvenous pacing
- Perm pacemaker may be required for unresolved third degree AV block (due to anterior wall MI)
- Atropine is not recommended for a complete heart block with wide QRS complexes, can slow ventricular rate down further
- Vasopressors may be used to treat hypotension
Inferior MI: Third Degree AV block
- Can resolve on it own
Anterior MI: Third degree block
May require perm pacemaking
Causes of third degree AV block
- MI
- Lyme disease
- Dig tox
- Aging
Supraventricular arrhythmias
- Originates above the ventricles
- Above the bundle branches
- Sinus, atrial and junctional rhythms
- Simultaneous depolarization of left and right ventricles occur, resulting in a narrow QRS complex
Atrial dysrhythmia
Ventricular arrhythmias
- Below bundle of His in the ventricles
- Async depolarization of left and right ventricle occur, resulting in a wide QRS
- More dangerous, potential to limit cardiac out put Severely
Premature ventricular contraction (PVC)
V-Tach
V-Fib
Ventricular standstill
Premature ventricular contraction (PVC)
- Premature, beat originating in an ectopic site in the ventricles
- The premature beat (PVC) occurs in addition to a basic underlying rhythm
- Characterized by wide QRS, ST segment and T wave which slope in the direction opposite the main QRS deflection
- P wave is not associated with PVC
- Occurs on a rhythm, with it occuring after x amount of beats (Can occur every 2, 3, 4 beats)
Essentially it looks like the heart skipped a beat
PVC: look the same on the same lead
Unifocal PVC: only one focal point
PVC: look different on the same lead
Multifocal PVC: Coming from multiple ectopic sites
Causes of PVC
- May occur following reperfusion procedures
- Thrombolytic therapy or angioplasty
- Basically anything that causes irritation to the heart (Abnormal K, Hypoxia, Low EF)
- May occur in individuals with a healthy heart but are more common in people with heart disease
Mgmt of PVC
- If infrequent, without symptoms, No treatment
- 6 or more PVC per min (Significant) , multifocal paired R-on T runs of three or more should be treated withAntiarrhythmic meds especially after cardiac surg
- Increased risk of V-tach or V fib
- Make sure Mg and K levels are normal
V-Tach
- Originates in an ectopic pacemaker site in the ventricles at a rate of 140-250
- Impulse originates in the ventricles, meaning no p wave and Qrs is wide
- VT occurs as a continuous rhythm or intermittently in short runs of 3 or more beats
- 3 or more CONSECUTIVE PVC is considered to be V-tach. Rhythm is usually reg by may be slightly irreg
- VT may be precipitated by PVC
What is V-tach precipitated by
It can be significant runs of PVC
Causes of V-Tach
- Underlying heart disease
- Electrolyte imbalances and hypoxia
- following stimulation of the endocardium during invasive cardiac procedures (Pacing lead insertion or swan cath)
- Following reperfusion procedures (PCI and thrombolytics)
Why is sustained V-tach life threatening
- Rapid ventricular rate and loss of atrial kick significantly reduces CO
- Sustained V-tach has the potential to be come v-fib or asystole
Treatment of V-tach: Stable monomorphic V-tach
- Amiodarone bolus, followed by amiodarone drip
- Synchronized cardioversion: once completed maintenance amiodarone infusion is started
Treatment of V-tach: Unstable monomorphic V-tach
- Immediate synchronized cardioversion: once there is a rhythm we give a maintenance dose of amiodarone, and an oral after acute period
V-fib
- Disorganized chaotic electrical focus that originates in the ventricles
- No, P or QRS, no contraction
- Ventricles quivers, irregular chaotic waves that have no pattern
- Shockable
V-fib: With large fib waves
Coarse V-fib, usually more irregular and distinctive than fine V-fib waves
V-fib:with small fib waves
Fine V-fib: can resemble asystole, should be confirmed in 2 leads
Most common cause of cardiac death in pt with acute MI
V-fib
What precedes V-fib
- Significant PVC, V-tach
- Can occur spontaneously without any precipitating rhythms
Causes of V-fib
- PVC/V-tach
- Myocardial ischemia
- Hypoxia
- Electrolyte imbalances
- Stimulation of the endocardium during invasive cardiac procedures (Pacing leads and swan cath)
- Following reperfusion procedures (Thrombolytic therapy and angio)
Pt in V-fib is unresponsive, apneic and pulseless
Death is imminent without treatment
Mgmt of V-fib:
- Attach monitor, check responsiveness and pulse
- If no pulse and pt is unresponsive defib once at highest energy level
- Start CPR, Establish IV line, intubate
- Admin EPI
- Continue CPR for 5 cycles (Circulate drug) and then defib at highest energy level
- Admin amiodarone or lidocaine
- Continue CPR for 5 cycles to circulate drug and defib at highest energy level
- Continue Drug,CPR,shock until rhythm resolves or a decision is made to stop
Mgmt of V-fib: Arrest is unwitnessed
Perform CPR for 5 cycles before initial shock
P waves without QRS
Asystole
Ventricular standstill
- Asystole
- Absence of all electrical activity in the ventricles
- When the ventricles are inactive there is no QRS, but there can be electrical activity in the atria, producing P waves
Two presentations of Asystole
- P waves without QRS
- Straight line
What precedes asystole
- Mobitz II
- Third degree heart block (complete)
- V-tach
- V-fib
- Defib or cardioversion procedures
- myocardial ischemia or infarction
- electrolyte imbalances
- hypoxia
- Drug overdose
- Cardiac trauma
How to determine asystole from fine V-fib at the bedside without cardiac monitoring
You cant, death is immediate without treatment
Asystole prognosis
Extremely poor despite resuscitation efforts
Amiodarone
- Class 3 antiarrhythmic, acting on K channels
- During arrest this can be given 2 times in adult
- 1st dose is 300mg
- 2nd is 150 mg
- V tach with pulse
- 150 mg bolus given over ten min
- Followed by a continuous drip of 1mg/hr for 6hr followed by 0.5 mg for 18hr
Amiodarone side effects
- It has an extremly long half life
- worsening AV Blocks
- Pulmonary fibrosis
- Increased liver enzymes
Better to have these side effects than dead
Epi
- Catecholamine which acts to support vascular tone and increase HR
- Acts on Alpha and beta receptors
- Used during complete asystole
- 1mg q 3-5 min
Mgmt of Asystole
CPR, until a smidge of electrical activity is returned then defib
* Start CPR, call a code
* Attach monitor
* Check responsiveness and pulse
* Establish IV lines and intubate
* Admin epi
* Consider causes of rhythm
* Continue CPR and epi unti rhythm is resolved or decision is made to stop
Bradycardia med mgmt
- None if not symptomatic
- If symptomatic
- Atropine
- Dopamine or Epi if atropine does not work
A-Fib med mgmt
- Amiodarone
- Adenosine
SVT med mgmt
- Amiodarone
- Adenosine
V-tach, with pulse med mgmt
- Amiodarone
- Adenosine
V-tach without pulse, med mgmt
- Amiodarone
- Lidocaine
- Epi
V-fib med mgmt
- Amiodarone
- Lidocaine
- Epi
