Cardiac Rhythm Disturbances Flashcards
***What does MAP stand for? What MAP value is necessary to maintain perfusion of major body organs, such as the kidneys and brain. What happens when the map is decreased?
- Mean Arterial Pressure
- 60 to 70 mm Hg
- When map is below 60 the heart hurts
What is Cardiac output ? What is the equation for Cardiac output?
Amount of blood pumped out in a given time.
Cardiac Output = Stroke volume X heart rate
What does the SA NODE do? Where is it located? What is the intrinsic rate of the SA node? How is the SA NODE reflected on the ECG?
- Chief Pacemaker - generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood
- SA Node Upper portion of the Right Atrium
- 60 - 100 bpm
- P wave - atrial depolarization - contraction of the atria
What does the AV node do? How is the slowing process of the AV node reflected on the ECG? What is the AV node’s intrinsic rate? In the case that the SA nodes fails, impulses may start at the level of the AV node, What are rhythms called that begin at the AV node?
The AV node serves as an electrical relay station, slowing the electrical current sent by the SA node before the signal is permitted to pass down through to the ventricles. Short delay allows atria to contract and ventricles to fill.
- Reflected in the PR segment
- 40-60 bpm
- Junctional rhythms- they start at the “junction” between the atria and ventricles. The actual pacer cells in this area are in the bundle of his just below the av node
What is the intrinsic rate of the Bundle of His ? What does the bundle of his do? What makes up the bundle of his, bundle branches and terminal purkinje fibers?
- 40-60 bpm
- The bundle of His connects with the distal portion of the AV node and continues through the interventricular septum branching to the right (one branch) and left ventricle (2 branches).
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What do Purkinje fibers do? What is the intrinsic rate? What is it called when the purkinje fibers initiate the heart beat and when would this occur?
- Provide electrical conduction to the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval.
- 20 - 40 bpm
- Ventricular rhythms - In the case that both the SA node and AV node stop working.
Normal Cardiac output
4 to 8 L/min
**What is PRELOAD? What drugs are aimed at decreasing preload?
- degree of myocardial fiber stretch at the end of diastole and just before contraction- Vasodilators, Diuretics
****What is AFTERLOAD? What determines afterload? Disease states that affect Afterload? Drugs used to improve?
Amount resistance that the ventricles must overcome to eject blood through the semilunar valves and into the peripheral blood vessels.
- Systemic arterial resistance
- More resistance makes it harder for the heart to pump blood
- Hypertension, aortic stenosis, blood viscosity, arteriolar constriction
**Antihypertensives - Beta Blockers, Vasodilators
What is a normal stroke volume?
70ml/beat
*****What is ATRIAL KICK ? What happens when Atrial Kick is lost? What percent of cardiac output is Atrial Kick is responsible for? What are the manifestations when Atrial Kick is lost?
- Contraction of the Atria that helps fill the ventricles
- Atrial Kick is lost when the SA Node is not the chief dominant pacemaker in the heart (afib, aflutter)
- 25 - 30% of CO
- When Atrial Kick is lost Manifestations Hypotension, shortness of breath, chest pain, increase pulse rate (to make up for cardiac output)
How do Baroreceptors affect blood pressure?
- Located in the aorta arch and carotid sinus. They recognize a change in tension and pressure and will kick in to help raise or lower BP according to need
Chemoreceptors
Increased carbon dioxide or decreased pH level causes the chemoreceptors to signal the heart to beat faster.
*** How do the kidneys help regulate cardiovascular activity?
- When renal blood flow or pressure decreases, the kidneys retain sodium and water. BP tends to rise because of fluid retention and activation of the renin-angiotensin-aldosterone mechanism. This mechanism results in vasoconstriction and sodium retention (and thus fluid retention).
** External factors that also affect BP ? Emotional , physical activity, temperature
- Emotional behaviors (e.g., excitement, pain, anger) stimulate the sympathetic nervous system to increase blood pressure (BP) and heart rate (HR).
- Increased physical activity such as exercise also increases BP and HR during the activity.
- Hypothermia, tissues require fewer nutrients and blood pressure falls.
- Hyperthermia, the metabolic requirement of the tissues is greater and BP and pulse rate rise.
What is Automaticity?
-the ability of cardiac cells that alone can generate and create an electrical discharge
What is EXCITABILITY?
Excitability is the ability of non-pacemaker heart cells to respond to an electrical impulse that begins in pacemaker cells and to depolarized.
- All cardiac cells have the ability to respond to electrical stimulation.
What is CONDUCTIVITY?
the ability to send an electrical stimulus from one cell to another.
What is Depolarization? What is the hearts to response to Depolarization?
- Depolarization occurs when the normally negatively charged cells within the heart muscle develop a positive charge.
- Contraction
Purkinje cells
- make up the bundle of His, bundle branches, and terminal Purkinje fibers. These cells are responsible for the rapid conduction of electrical impulses throughout the ventricles, leading to ventricular depolarization and the subsequent ventricular muscle contraction.
What is the immediate priority for patients in VF or pulseless VT?
Defibrillate, then CPR is resumed
PR INTERVAL
- Measurement from the beginning of the P wave to the end of the PR segment.
- Time required for atrial depolarization as well as the impulse delay in the AV node and the travel time to the Purkinje fibers.
** It normally measures from 0.12 to 0.20 second (five small blocks).
ST SEGMENT
What does an elevate ST mean?
What does depression mean?
- Measures time between ventricular depolarization and early VENTRICULAR REPOLARIZATION (rest).
Elevation = Injury or death to myocardial tissue Depression = ischemia
- Its length varies with changes in the heart rate, the administration of medications, and electrolyte disturbances.
- The distance from the S wave to the beginning of the T wave.
T WAVE
VENTRICULAR REPOLARIZATION. It is usually positive, rounded, and slightly asymmetric.
** PEAKED T WAVE IS AN INDICATION FOR HYPERKALEMIA (INCREASED POTASSIUM)
- T waves may become tall and peaked, inverted (negative), or flat as a result of myocardial ischemia, POTASSIUM or calcium imbalances, medications, or autonomic nervous system effects.
- The T wave follows the ST segment and represents
U WAVE
The U wave, when present, follows the T wave and may result from slow repolarization of ventricular Purkinje fibers.
** Hypokalemia
What does the QRS INTERVAL represent? What is the normal time frame?
- Time required for depolarization of both ventricles.
***It normally measures from 0.04 to 0.12 second (up to three small blocks).
Rhythm Interpretation Steps
- Determine heart rate - Atrial - P waves; Ventricular - QRS
- Determine heart rhythm
- Analyze P waves
- Measure PR interval
- Measure QRS
- Identify the rhythm
Digoxin
- increases vagal tone, slowing AV nodal conduction.
Uses: Chronic Afib
Sinus Bradycardia can be normal in which patients?
Athletes during sleep; increase vagal tone (vomiting , valsalva maneuver); beta blockers
Treatment for Bradycardia (if symptomatic)?
- Atropine 0.5mg IV
- IV Fluids
- Oxygen
- temporary pacing - increase conduction
Sinus Tachycardia can be normal in which patients?
Increased sympathetic tone, CHF, hypoxia, fever, pain, stimulants, Increased myocardial workload and 02 demand
Causes of Sinus Tachycardia?
Caffeine, narcotics, amphetamines, cocaine, or thyroid issues
What are PREMATURE ATRIAL CONTRACTIONS? How does it affect the rhythm, rate, P waves?
- Ectopic atrial tissue fires a n impulse before sinus impulse is due. May signify impending AFIB
- HR is normal but rhythm is irregular
- Inconsistent P wave - may occur rarely or be buried in prior T wave
- Significance - PT should avoid caffeine, anxiety, could lead to more serious dysrhythmias
**
What happens in ATRIAL FLUTTER? How is the P WAVE affected? What role does the AV node play? What are patients with ATRIAL FLUTTER at risk for? Classic sign of A Flutter on a EKG?
- SA NODE is no longer in charge thus we end up with a very high atrial rate
- Atrial rhythm is normal (occur in a rhythmic fashion) but the P waves resemble a “saw-tooth pattern,
- A/V node protects the ventricles from beating at the same increased rate as the atrium
- At risk for thrombi due to the pooling of blood. etc. pulmonary embolism and embolic stroke
- Treatment - Antidysrhythmics, anticoagulants, if unstable cardioversion.
- SAW TOOTH
***What is ATRIAL FIBRILLATION? Rhythm? P waves? What is AFib usually associated with? Signs and Symptoms ?
- No P waves and a very irregular rhythm (wavy baseline)
- Treatment - Antidysrhythmics, anticoagulants, beta blockers, if unstable cardioversion. (Lifetime medicine = anti coagulant)
- Associated with Heart disease or COPD, can precipitate decreased cardiac output
***Assess for thromi,
Signs and Symptoms: irregular rapid heart rate, lower blood pressure, ortho-hypotension, low 02 stat, anxious, change in level of consciousness
Radiofrequency Catheter Ablation
Invasive procedure that may be used to destroy an irritable focus causing a supraventricular or ventricular tachydysrhythmia.
What is a 1st Degree HEART BLOCK? How does this appear on the strip? Typical cause? Treatment?
- Conduction delay from the Atria to the Ventricle which is evidenced by the PR interval being longer than .20 sec
- Rhythm is regular, P waves are normal, QRS normal, PR intervals prolonged, rate is typically normal
- More than likely caused by medications that prolong AV conduction such as digoxin, calcium channel blockers, and beta blockers.
- See if patients are symptomatic, find cause and reviewing patient medication
What are ECTOPIC BEATS? PAC’s ? PJC’s? PVC’s ?
- Small changes in a heartbeat that is otherwise normal
- PACs are generated in the atria and have a P wave (full contraction right after a full contraction)
- PJCs are generated from the AV node and usually have a short PR or no P at all (contraction (heartbeat) with a narrow QRS complex, less than 0.12 sec, but you have no P waves.)
*******What are PREMATURE VENTRICULAR COMPLEXES? How does it appear on the EKG? What are the typical causes when OVC is frequent and sustained? PVC may be a warning for the impending onset of ….? Treatment
Results from increased irritability of ventricular cells and are seen as early ventricular complexes followed by a pause. - PVC’s are generated from the ventricles and are wide (Contraction (heartbeat) with a wide QRS complex that is greater than 0.12 seconds.)
Rate = variable; Rhythm= atrial regular, ventricular irregular; P waves= normal with sinus QRS wide (.12 sec or more), bizarre appearance (uniform or multiform)
- Frequent and sustained PVC often indicates ventricular irritability due to hypoxia, heart disease or drug toxicities; may result in decreased cardiac output , may be a warning for the impending onset of, or precipitate V-tach or V-fib
- Treatment = antidysrhythmics if symptomatic (amiodarone, lidocaine, procainamide, B-blockers)
What is VENTRICULAR TACHYCARDIA? What does it look like on the strip? Causes? What does the patient look like? Treatment ?
- Repetitive firing of ventricular (MAJOR IRRITABILITY)
- 100 - 250 bpm, regular rhythm, P waves usually obscured by QRS complex, no PR interval, QRS wide, bizarre appearance
- Almost always occurs in diseased hearts especially with acute MI, drug toxicities, heart failure, hypoxia, acidosis, ventricular aneurysms
- Pt is often symptomatic w/ sudden , profound heart failure; VT is unstable and may deteriorate into VF
- Treatment
Pharm: antidysrhythmics amiodarone, procainamide, lidocaine
Pulse present: cardiovert
Pulseless: defibrillation
What is VENTRICULAR FIBRILLATION? What is happening in the heart? How long can VF go on before death? Causes? What does the pt look like? Priority care
- Electrical chaos in the ventricles; totally disorganized ventricular contractions; ventricles are quivering
- HEART = ventricles merely quiver, consuming a tremendous amount of oxygen, No cardiac output or pulse thus no cerebral, myocardial, or systemic perfusion.
- This rhythm is rapidly fatal if not successfully ended within 3-5 minutes
- Pt’s with coronary artery disease, MI, hypokalemia, hypomagnesemia, hemorrhage, drug therapy, rapid SVT, shock or Trauma
- Pt presentation: Faint, lose consciousness, pulseless, apneic, not BP
- Priority care = DEFIBRILLATE THE PATIENT IMMEDIATELY. Do CPR until defibrillation is ready (heart needs to be shocked into some kind of rhythm)
Polarization
Cardiac cells at rest, no electrical activity.
Repolarization
Return of the ions to a resting state, causing relaxation of cardiac muscle.
NA+ - What is the normal range? Intracellular ion or extracellular?
- 135-145 - extracellular
K+- Normal range? What cells are particularly sensitive to potassium? Intracellular ion or extracellular?
- 3.5-5; Intracellular
- pacemaker cells
Ca++ Normal range? Intracellular ion or extracellular?
- 5 to 10.2 mg/dL
- extracellular
When do you DEFIBRILLATE (Asynchronous) ?
-Asynchronous countershock that depolarizes critical mass
- Pulseless VTACH
- VFIB
What is Asystole? How do you Verify Asystole? Priority Care?
- Complete absence of any rhythm.
Verification: Check the leads and check the patient; Consider another EKG monitor to determine if asmystole or fine V-FIB.
Treatment: CPR; External temporary pacing, epinephrine, atropine
*****When do you do CARDIOVERSION (synchronized) ? What test should you do before cardioversion on a pt with AFIB, AFLUTTER?
- VTACH with pulse ; Unstable AFIB or AFLUTTER electively for stable tachydysrhythmias
- Trans Esophageal Ecocardiogram - (TEE) - check to see if there are any clots that can be dislodged
What is TEMPORARY PACING? INDICATIONS? What are the two basic types? What are the modes of pacing?
WHAT: Used to maintain heart rate and perfusion until more permanent method of pacing is used
INDICATIONS: Symptomatic Bradydysrhythmias, 2nd or 3rd degree heart block, Asystole
TYPES: Transcutaneous (temporary - used until better method of pacing can be done) of Transvenus
What is PERMANENT PACING? INDICATIONS?
WHAT: Device inserted to treat conduction disorders that are not temporary?
INDICATIONS: Complete heart block, Unstable AFIB
What INFORMATION ABOUT A PERMANENT PACER do you want to collect from a patient?
- Which chamber is being paced? (atria, ventricle, both)
- Which chamber is being sensed (atria, ventricle, both)
- Type of response (inhibit or trigger)
- Rate adaptiveness ( Can it fluctuate as needed based on metabolic demands)
Types of IMPLANTABLE DEVICES?
- Single Chamber (how many chambers of the heart)
- Dual Chamber
- Rate Responsive (responds based on rate)
- Tachyarrhythmia modes
- ICD (Implantable Cardiac Defibrillator) - for people at high risk for cardiac death
- Bi-Ventricular (coordinates right and Left Ventricle contractions)
- Reveal Implantable Loop Recorders - used to diagnose and treat dysrhythmias
What are the two MODES OF PACING?
- Synchronous (demand)
2. Asynchronous (fixed-rate)
***Pacemaker/ICD EDUCATION:
- Report skin irritation at pacemaker site, report fever,
- Don’t apply pressure over your generator. Avoid tight clothing
- Follow activity restrictions
- Avoid external electrical fields
- Record daily pulse (1min) at the same time every day. (or if they patient is having symptoms of P/M failure)
- Teach patient S/S of pacemaker failure
- Report hiccups, weight gain, difficulty breathing, dizziness, fainting, chest pain.
Post - OP PACEMAKER CARE INSTRUCTIONS?
- Avoid getting incision wet for 1st week (no shower/steam)
- Don’t raise arm on the side of the device above shoulder for 3 weeks
- No lifting more than the weight of a Gallon of milk for 3 weeks
- Report twitching sensations in the chest
- Report Strong jolt to chest
What should a person with a PACEMAKER AVOID do to INTERFERENCE?
- Arc welding
- MRI scans
- Magnetic anti-theft exits at stores
- Airport security (hand wand as well)
What should a person with a PACEMAKER AVOID do to INTERFERENCE which at HOME ?
- Keep small hand held appliances 6 inches from device while in use
- Use and store cell in opposite side of device
- Keep 12 inches between P/M and power tools or small running engines
- Ground all power tools
- Try to avoid chain saws (if necessary use ELECTRIC)
How can you stop the pacemaker from working during an EKG to figure out what the patients intrinsic rate is?
Placing a magnet on the Pacemaker will temporarily stop the P/M from working
Where will you see the pacing spike on the EKG of a patient being A PACED versus a patient being V PACED?
In an A PACED patient, the spike will be before the P wave while in a V PACED patient the Pacer spike will be before the QRS wave (wave will be deflected down which is a normal finding)
What is Undersensing? Causes?
- Pacemaker fails to sense the patients intrinsic beat. PACING CAN’T OCCUR WHEN IT IS SUPPOSED TO IF THE PACEMAKER CAN’T SENSE INTRINSIC BEAT
- Results in asynchronous pacing
- increased stimulation threshold at electrode site (exit block), poor lead contact, new bundle branch block or programming problems.
What is? Failure to Capture? Causes?
- Failure to capture occurs when paced stimulus does not result in myocardial depolarization. Not responding to a pacing stimulus
CAUSES: electrode displacement, wire fracture, electrolyte disturbance, MI or exit block.
What might you NOTICE if the patient is experiencing inadequate oxygenation and tissue PERFUSION as a result of dysrhythmias?
- Report of chest discomfort or pain
- Report of dizziness or syncope
- Shortness of breath
- Weakness and fatigue
- Decreased urine output
- Pale, cool skin
- Diaphoresis
- Anxiety or restlessness
What should you assess when a patient is experiencing inadequate oxygenation and PERFUSION as a result of dysrhythmias?
- Taking vital signs (may have hypotension and weak pulse)
- Checking for pulse deficit
- Asking if patient has palpitations
- Checking capillary refill (decreased)
- Listening to lung and heart sounds
- Assessing cognition
- Taking an ECG
- Checking oxygen saturation
How should you RESPOND to a patient experiencing inadequate oxygenation and PERFUSION as a result of dysrhythmias?
- Apply Oxygen and get the MONITOR on
- Keeping the head of the bed elevated unless patient is very hypotensive
- Maintaining or starting an IV line
- Notifying the health care provider or Rapid Response Team
- Giving drug therapy as prescribed
- Initiating CPR for asystole
- Defibrillation if the patient in VF
How do we measure the EKG?
- little box = 0.04
- big box = 0.20