ECG’s, Dysrhythmias Flashcards
How do cardiac dysrhythmias occur?
Problem with initiation or conduction affecting rate, rhythm, or both. The rhythm and impulse is generated somewhere other than the SA node. All heart muscle is able to generate an electrical signal, so the dysrhythmia causing impulse can happen anywhere. Cause by muscle irritability.
Dysrhythmia treatment?
Oxygen, meds, cardioversion or defibrillation, CPR when someone is pulseless to keep blood flowing. Ablation to kill problem tissues and for long term fixing (not for emergent situations). Identify and treat the underlying cause.
Oxygen for dysrhythmias with respiratory distress?
Always give 100% O2, never withhold. Always given with SOB, chest pain, and dysrhythmias. Acute chest pain may be due to cardiac ischemia, lack of blood decreases O2 for tissues.
Prompt treatment of hypoxia may prevent cardiac arrest. Pulse oximetry is unreliable during codes due to lack of perfusion in the periphery, like cardiopulmonary arrest.
Wave that represents the electrical impulse starting in the SA node and spreading through the atria. Atrial depolarization.
P wave. Normally 2.5 mm or less in height and 0.11 sec or less in duration.
Wave that represents ventricular depolarization. Normally less than 0.12 seconds in duration.
QRS complex. Not all have three waveforms. Q is normally less than 0.04 sec and less than 25% of the R wave amplitude.
When a wave is less than 5mm in height small letters (qrs) are used, taller than 5 is capital letters.
Wave that represents ventricular repolarization (when the cells regain a negative charge, also called a resting state). Usually the same direction as the QRS complex.
T wave. Atrial repolarization also occurs but is not visible of the QRS complex.
Wave that represents repolarization of the Purkinje fibers. Rare, sometimes appears in pts with hypokalemia, HTN, or heart disease.
The U wave. Follows the T wave and is usually smaller than the P wave. If tall, may be mistaken for an extra P wave.
Measured from the beginning of the P wave to the beginning of the QRS. Represents the time needed for sinus node stimulation, atrial depolarization, and conduction through the AV node before ventricular depolarization
PR interval. 0.12 to 0.20 seconds in duration.
Represents early ventricular repolarization, lasting from the end of the QRS complex to the beginning of the T wave. Normally isoelectric.
ST segment. Usually identified by a change in thickness or angle of the terminal portion of the QRS complex. May be difficult to identify because it merges into the T wave.
Represents the total time for ventricular depolarization and repolarization. Varies with HR, gender, and age. If it becomes prolonged the pt may be at risk for torsades de pointes.
QT interval. Measured from the beginning of the QRS complex to the end of the T wave. Usually 0.32 to 0.40 sec if the HR is 65-95 bpm.
Because it varies the measured interval needs to be corrected through specific calculations.
Interval that is used to determine atrial rate and rhythm.
Interval that is used to determine ventricular rate and rhythm.
PP interval. Measured from the beginning of one P wave to the beginning of the next P wave.
RR interval. Measured from one QRS complex to the next QRS complex
What are methods for determining HR on an ECG?
One method when the rhythm is regular is to count the number of small boxes within an RR interval and divide 1500 by that number. Ex: 10 small boxes between two R waves, HR is 1500/10, or 150 bpm.
Another that is used for irregular rhythms is to count the number of RR intervals in six seconds and multiply that number by 10.
The same methods may be used for determining atrial rare using the PP interval instead of the RR.
Effective in tachydysrhythmias with a pulse. Electrical conduction synchronized with the QRS to stop the tachy. Timed electrical current discharged during the QRS. Goal is to help the SA node take back control of the rhythm.
Cardioversion. Afib with rapid ventricular response (RVR), vent tach with a pulse, superventricular tachy (SVT).
Synchronization prevents discharge from occurring during the vulnerable period of repolarization (T wave) which could result in VT or vfib. When the synchronizer is on, no electrical current is delivered if the defibrillator does not discern a QRS complex.
Explain the cardioversion process
Pt must have a pulse. Place electrode pads to chest. Press synchronized mode. Start with low joules (50-100 joules/biphasic). May use moderate sedation cause pain, moderate sedation IV with analgesic or anesthesia. Respiration is then supported with supplemental O2 via bag-valve mask with suction. Intubation equipment needs to be available.
Explain procedures for elective cardioversion?
If it’s elective and the dysrhythmia has lasted longer than 48 hours, anticoagulation for a few weeks before cardioversion may be indicated. Digoxin is usually withheld for 48 hours before to ensure the resumption of normal sinus rhythm with normal conduction. Pt is NPO for at least 4 hours before.
What are the indications of a successful cardioversion? What must be assessed?
Conversion to sinus rhythm, adequate peripheral pulses, adequate BP. Because of sedation, airway latency must be maintained and pt’s LOC assessed.
Used with pulseless vtach and vfib, which are the most common causes of abrupt loss of cardiac function and sudden cardiac death. Not used for those who are conscious. Must still have electrical activity.
Defibrillation. Electrical shock to stop chaotic asynchronous electrical activity. Doesn’t have to be timed with the QRS or anything else. Goal is to have the SA node regain control.
Explain the defibrillation process?
Perform CPR until defibrillator ready. Place electrode pads on chest (hair decreases conductivity). Charge up to 120-200 joules for biphasic, 360 for monophasic. No sedation is needed because pt is unconscious.
Meds used with defibrillation?
Epinephrine or vasopressin after defibrillation to make it easier to convert the dysrhythmia to a normal rhythm with the next defibrillation, also may increase cerebral and coronary artery blood flow.
Antiarrhythmics such as amiodarone, lidocaine, is mag may be given if ventricular dysrhythmia persists.
Explain defibrillation safety?
Make sure to unplug the defibrillator when retrieving it. First verify the EKG tracing in 2 leads. Prior to delivering the shock, make sure that no one is touching anything. They usually work on battery so keep it plugged in when not in use.
Electronic device that provides electrical stimuli to the heart muscle. Usually used when pt has a symptomatic bradycardia, 2/3 degree AVB, bundle branch block (BBB), atrial overdrive to terminate afib or flutter with RVR. May also be used to control some tachydysrhymias that don’t respond to meds.
Pacemakers. Consist of an electronic pulse generator and pacemaker electrodes, which are located on leads or wires. Generator measures rate and output (in milliamps). Can also detect the intracardiac electrical activity to cause an appropriate response, termed sensitivity (in millivolts)
Explain lead and wire placement in pacemakers?
Leads, which carry the impulse created by the generator, can be threaded through a major vein to the heart, usually the right atrium and ventricle (endocardial leads). Or they can be lightly sutured onto the outside of the heart and brought through the chest wall during open heart surgery (epicardial wires).
Epicaridal wires are always temporary, while endocardial may be permanent or temporary.
The pacemaker paces the atrium and then the ventricle when no ventricular activity is sensed for a period of time. Explain capturing and pacing?
A P wave should follow an atrial pacing spike, and a QRS complex should follow a ventricular pacing spike. Because the impulse starts in a different place than the pt’s normal rhythm, the complex or wave that responds to the pacing looks different from the pt’s normal EKG complex.
What are the two main types of pacing for pacemakers?
Generally set to sense and respond to intrinsic activity, called on-demand pacing.
When the pacemaker fires at a constant rate, independent of pt’s rhythm, it’s set to pace but not sense. This is fixed or asynchronous. AOO or VOO. VOO may indicate battery failure.
This type of pacing can cause loss of AV synchrony and atrial kick, which may cause a decrease in CO and an increase in atrial distinction and venous congestion.
VVI (V, paces the ventricle. V, senses ventricular activity. I, paces only if the ventricles do not depolarize). Pacemaker syndrome (chest discomfort, SOB, fatigue, activity intolerance, postural hypotension) is most common with VVI.
What kind of pacing is recommended over VVI in pts with sinus node dysfunction (sick sinus syndrome) and a functioning AV node?
Single-chamber atrial pacing (AAI) or dual-chamber pacing (DDD).
AAI pacing ensures synchrony between atrial and ventricular stimulation, and therefore contraction, as long as the pt has no conduction disturbances in the AV node. Dual-chamber pacemakers are recommended for pts with AV conduction disturbances.
This type of pacing has been found to modify the intraventricular, interventricular, and artioventricular conduction defects associated with symptomatic moderate to severe left ventricular dysfunction and HF. May be used with an ICD.
Synchronized biventricular pacing, also called cardiac resynchronized therapy. Improves cardiac function, resulting in decreased HF symptoms.
Three leads: right atrium, right ventricle, left ventricle.
Failure of the pacemaker to cause contraction.
Failure to capture. Causes in life threshold rise (electrolytes, drugs), lead dislodgment, lead fracture, RV infarction, myocardial ischemia.
