Dysrhythmias Flashcards
Where is the PR interval?
from the beginning of the P wave to the beginning of the Q wave– 0.12-0.2 seconds
Where is the QRS complex?
from the beginning of the Q wve to the end of the S wave– less than 0.12 seconds
Where is the QT interval?
measure from the beginning of the Q wave to the end of the T wave– 0.34-0.43 seconds (if HR is 60-100)
-prolonged QT intervals is a risk for sudden death
What is the R-R interval?
the measure between R waves– 0.6-1 second
What are the 5 things that you ask yourself when interpreting an ECG?
1) is the rhythm regular or irregular?
2) what is the rate?
3) is there a P wave for every QRS complex?
4) are the QRS complexes normal or wide?
5) is there an elevation in ST segments?
Which type of MI can not be diagnosed with an ECG?
non-ST elevation MI (NSTEMI) because there is no change to the ECG
–a STEMI (MI with ST elevation) signals a more serious MI with full thickness infarction and treatment can be guided by this finding alone (but troponin will still be done)
Define pericarditis
inflammation of the pericardium (sac surrounding the heart)
– most common cause is a viral infection, but it is also seen in pts with autoimmune conditions like SLE or RA, or after an MI
What are the manifestations of pericarditis?
-fever
-pleuritic chest pain (meaning it is worse on inspiration and improved upon sitting up/forward)
-pericardial friction rub (superficial scratchy or squeaking sound best heard on left sternal border)
-widespread ST-segment elevation
-evidence of pericardial effusion (build up of extra fluid around the heart)
Define pericardial effusion
build up of extra fluid around the heart– seen in pericarditis
What is the treatment for pericarditis?
-NSAIDS (Ex. ibuprofen or ASA) and colchicine
-corticosteroids
these meds help with inflammation, which is what pericarditis is
What affects does hyperkalemia have on heart rhythm?
-produces peaked T waves– exaggerated due to the increased excitability
What affect does hypokalemia have on heart rhythm?
-produces a shallow T wave and an extra U wave not usually seen
How does a potassium imbalance affect the heart?
-affects the resting membrane potential (RMP) making nerves either more (hyperkalemia) or less (hypokalemia) excitable
What treatment is used to treat hyperkalemia?
-IV calcium is used to offset the difference between the RMP and the threshold potential in the case of hyperkalemia– this does NOT lower the K+ levels, so treatment for this is still needed
-if life threatening arrhythmias is present, IV calcium is the priority but will not be used for everyone (like if the hyperkalemia is mild with only subtle ECG changes)
What treatment is used to treat hypokalemia?
-K+ supplement
-if a pt is on a loop diuretic causing hypokalemia, they usually are put on a supplement but may also have a potassium sparing diuretic added to reduce K+ wasting
How do you assess if a rhythm is regular on an ECG?
-compare the distances between R-R intervals
-when wanting to be precise, a pair of calipers will be used
-for less precise, you can right tallies on a strip of paper at the R-R interval and then compare to the next interval
How many seconds is on a strip?
6
How do you get an estimate of rate from an ECG?
-count the number of large squares between R-R interval (ex. 5)
-divide 300 by the number (5)
300/5= 60bpm
Define sinus arrhythmia
-a normal physiological phenomenon, most commonly seen in young, healthy people
-the HR varies due to reflex changes in vagal tone during the different stages of the respiratory cycle
-inspiration increases the HR by decreasing vagal tone
Define sinus tachycardia
-sinus node firing at >100bpm
-associated with psychological/physiological stressors as a compensatory mechanism or d/t various drugs
What is the clinical significance of sinus tachycardia?
-will result in increased myocardial oxygen demand, decreased supply, and decreased ventricle filling time
What is the immediate actions and treatments done for sinus tachycardia?
-ensure pt is safe and has IV access, apply O2 as per policy
-in stable pts, treat the underlying cause (such as fluids, treating pain, fever, etc)
-beta blockers may be used
Define sinus bradycardia
-sinus node fires at a rate of <60bpm
-can also be the result of drugs (beta blockers), hypothermia, Valsalva maneuver, hypothyroidism, hypercalcemia, or injury to SA node (inferior MI)
What is the clinical significance of sinus bradycardia?
-may result in decreased BP and decreased CO, which can lead to symptoms
What are the immediate actions and treatments for sinus bradycardia?
-asymptomatic is not normally treated
-ensure pt is safe and has IV access
-atropine IV (anticholinergic)– will increase SA node firing
-long term tx may include pacemaker insertion
When is sinus bradycardia normal?
-sleeping patients
-conditioned athletes
-as a result of some medications
What are the symptoms of symptomatic sinus brady?
hypotension– dizziness, nausea, syncope, and SOBOE (shortness of breath on expiration?)
Define supraventricular dysrhythmias
-a problem within the atria, the AV node, or the bundle of His
-characterized by the absence of normal P waves and are typically associated with fast heart rates
-QRS complexes are usually normal in appearance
Ex. Afib, atrial flutter and supraventricular tachycardia
Define supraventricular tachycardia
-also called SVT and atrial tachycardia
-irritated areas on atria take over as pacemaker– impulses are caught in a “re-entry loop”
-associated with underlying cardiac disease, SNS stimulation
-most often paroxysmal (periodic and resolving)– pt has “runs” of SVT in between normal rhythm
What is the clinical significance of supraventricular tachycardia?
-if prolonged, may cause myocardial ischemia, decrease ventricle (decreased CO)
What immediate actions and treatments should be done for supraventricular tachycardia?
-if stable, valsalva maneuver or carotid massage, CCMs, BBs, adenosine
-if unstable, synchronized cardioversion
Describe the modified valsalva maneuver used in treatment for SVT
While in the semi-fowler position the patient is instructed to blow forcefully into a 10 mL
syringe to move the plunger for about 15 sec then is lowered into the supine position and
passive leg raises are performed for another 15 sec
Describe the medications used for treatment of SVT
Medications: calcium channel and beta blockers as well as adenosine to slow conduction at the AV
node.
▪ adenosine causes bronchoconstriction, so may be contraindicated in pts with asthma/COPD
Define Afib
-atrial fibrillation
-Rapid and irregular depolarizations from multiple ectopic areas of the atria
-irregular & rapid ventricular response
-Usually occurs d/t injured or stretched atrial tissue (MI, HF, pericarditis) or d/t
stimulants or electrolyte imbalances
What is the clinical significance of afib?
- May be asymptomatic but can also result in ↓CO
- Chronic afib significantly increases the risk of embolic stroke
What immediate actions and treatments are used for afib?
- If present for <48h, antiarrhythmic drugs (amiodarone) or cardioversion → NSR
- If chronic- anticoagulation and rate control (ventricular response <100bpm)
will be based on symptoms and HR
What does the ECG look like for afib?
-irregular
-p waves are chaotic
-v rate 75-150
What does the ECG look like for SVT?
-regular
-p waves are “hidden” in the t waves
-rate of around 230
What should be done before cardioversion?
-assess for risk of embolization and treat with anticoagulants if needed prior to cardioversion– the longer the afib is present the more likely that a clot will be dislodged
Describe atrial flutter
- Impulse is generated from a single place in the right atrium (not SA node) that fires rapidly
- Not as common as afib, can occur d/t MI, HF, pericarditis, or d/t stimulants or electrolyte
imbalances
What is the clinical significance of atrial flutter?
- May be asymptomatic but can also result in ↓CO
- Chronic aflutter significantly increases the risk of embolic stroke
What immediate actions and treatments are done for atrial flutter?
similar approach as afib
- If present for <48h, antiarrhythmic drugs or cardioversion → NSR
- If chronic- anticoagulation and rate control (ventricular response <100bpm)
based on symptoms and HR
Describe an atrial flutter ECG
-regular (can be irregular)
-4:1 ratio
-p waves look like a saw tooth
-A rate about 270-300
-V rate about 70
Describe a ventricular dysrhythmia
Premature ventricular contractions (PVCs)
* Impulse originating in the ventricles (a premature QRS with no associated P wave)
* Single instances are normal and associated with stimulants (caffeine, alcohol, nicotine).
Also d/t fever, exercise, MI, and electrolyte imbalances
If an impulse originates below the AV node and bundle of His it is considered a ventricular
dysrhythmia. This may be a benign “add on” rhythm such as with occasional PVCs, or a life-
threatening rhythm such as V-tach and V-fib
What is the clinical significance of ventricular dysrhythmia?
- Single or couplets can cause feeling of palpitations (but often asymptomatic)
- Multiple PVCs in a row can decrease CO
What are the immediate actions and treatments for ventricular dysrhythmia?
- Remove/treat the cause (if symptomatic)
- Amiodarone used to prevent runs of V-tach
Describe ventricular dysrhythmia on an ECG
A PVC is a premature occurrence of a QRS complex.
* HR varies according to intrinsic rate and number of PVCs.
* Although the rhythm may be irregular because of premature beats, if the underlying rhythm is
sinus, it is considered “a sinus rhythm with PVCs”.
* The P wave is rarely visible and is usually lost in the QRS complex of the PVC. Retrograde
conduction may occur, and the P wave may be seen following the ectopic beat.
* The PR interval is not measurable.
* The QRS complex is wide and distorted in shape, lasting longer than 0.12 second. The T wave
is generally large and opposite in direction to the major direction of the QRS complex
What is a PVC?
-premature ventricular contraction (premature QRS complex)
-impulse originating below the AV node and bundle of His
-ventricular dysrhythmia
-p wave rarely visible and usually lost in the QRS complex
-PR interval not measurable
-QRS is wide and distorted
-often asymptomatic but can feel like palpations and cause dizziness
What electrolyte imbalances can cause PVCs?
-hypokalemia
-hyperkalemia
-hypomagnesemia
-hypocalcemia
