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M6 13-005
Exam 4: Cardiovascular System; Cardiac Dysrhythmias
Term | Definition |
---|---|
Conduction system of the heart | Autonomic Nervous System |
Autonomic Nervous System | Sympathetic & Parasympathetic |
Conduction System Heart Muscle Characteristics | Automaticity & Irritability |
Automaticity & Irritability | Characteristics that affect the conduction system |
SA Node | Site of normal impulse origin |
Bachmann's | Impulse leaves the SA node, traveling through the atria via ____ |
40-60 BPM | Impulse wave continues to the AV node of the heart @ |
Bundle of His | Divides into the right and left bundle branches that extend down either side of the interventricular septum |
Purkinjie Fibers | Generates in impulse of 20-40 BPM |
20-40 BPM | Pukinjie Fibers impulse rate |
Flow of electricity through hearts conduction system | SA node> AV node> Bundle of his, (right and left bundle branches) Purkinjie Fibers |
EKG (ECG) | Graphic study of the recording of the electrical activity of the myocardium |
Depolarization | the conducted cardiac impulse transiently reverses membrane polarity. In this depolarized phase the myocardium is incapable of further contraction. |
Repolarization | The process whereby the membrane, cell, or fiber, after depolarization, is polarized again, with positive charges on the outer and negative charges on the inner surface. |
EKG Machine | Records the heart's electrical activity from electrode sensors placed on the skin |
Hoizontal axis | Represents time |
Vertical Axis | Represents voltage |
.02 Seconds | 1 square on rhythm strip equals |
1 second | 1 Block (5 squares) on rhythm strip equals |
3 seconds | 15 blocks on rhythm strip equals |
Rate Determination Methods (4) | Cardiac Ruler Method, Six second Tracing Method, 300 Method, 1500 Method |
P, Q, R, S, and T Waves | Components of the Normal ECG Complex |
P Wave | First positive deflection representing depolarization of the atria. (0-0.2 seconds) |
Q Wave | First NEGATIVE deflection after the P wave |
R Wave | First POSITIVE deflection after the P wave |
S Wave | NEGATIVE deflection after the R wave |
QRS Complex | Represents ventricular depolarization. (0.06-0.12 Seconds) |
PR Interval | Represents the time it takes an impulse to travel from the SA node across the atria t the AV node fibers (0.12-0.20) |
T Wave | Represents repolarization of the ventricle |
ST Segment | Represents early repolarization of the ventricular muscle. |
Steps for interpreting the EKG | Systemic analysis, Determine Heart Rate, Determine Rhythm |
Rhythm Strip | Find P waves, measure P-R interval, Measure the QRS complex, Find the T waves, Evaluate the ST segment, Measure the QT interval |
Dysrhythmia | Any cardiac rhythm that deviates from normal conduction with normal intervals. Results from irritability of myocardial cells that generate impulses. |
Normal Sinus Rhythm (NSR) (StriP) | Rate: 60-100 bpm Rhythm: Regular (Consistent R-R & P-P) P Wave: Present for each QRS complex, Normal config, normal P-R interval, Normal QRS interval, T wave upright |
Types of Dysrhythmias | Sinus Tachycardia, Sinus Bradycardia, Supraventricular Tachycardia, Atrial Flutter/Fibrillation, Atrioventricular Block, Premature Ventricular Contracions, Ventricular Tachycardia, Ventricular Fibrillation |
Dysrhythmias are a result of what? | Either an alteration of the formation of the impulse through the SA node to the rest of the myocardium or irritability of the myocardium cells. |
Sinus Tachycardia (Strip) | Rate: greater than 100 Rhythm: Regular P Wave: present for each QRS complex, normal config, and each P wave is identical P-R interval: normal QRS Complex: Normal T Wave: Normal |
Sinus Tachycardia (Etiology) | Sympathetic Nervous System stimulates the heart, increasing the rate. Increase is gradual. |
Sinus Tachycardia (Causes) | Anxiety Exercise Fever Shock, hypotension Medications (i.e. vasopressors, albuterol) Hyperthyroidism. Heart failure, angina Stimulants (caffeine, nicotine, amphetamines) Hypothermia, Pain |
Sinus Tachycardia (Manifestations) | Many Pt's asymptomatic, occasional palpitations, Hypotension, Angina, SOB, Diaphoresis, HF |
Sinus Tachycardia (Medical Management) | Directed at treating the underlying cause, normally not caused by cardiac problem |
Sinus Bradycardia (Strip) | Rate: Less than 60 BPM. Rhythm: R-R & P-P intervals are regular P Wave: Present for each QRS complex, normal configuration, and each P wave identical PR interval: Normal QRS Complex: Normal T Wave: Normal |
Sinus Bradycardia (Etiology) | Parasympathetic nervous system is stimulated, causing the SA node to slow |
Sinus Bradycardia (Underlying Causes) | Normal in the well-conditioned athlete Medications (B-blockers, digoxin) Hypothyroidism Cardiac diseases; predominately acute MI Sleep Hypothermia Vagal stimulation (i.e., vomiting, bearing down, holding breath) Intracranial tumors |
Sinus Bradycardia (Manifestations) | May be asymptomatic Fatigue Hypotension, Lightheadedness, and syncope |
Sinus Bradycardia (Medical Management) | Atropine (0.6-1.0 mg IVP) Transcutaneous pacing, until transvenous pacer available Dopamine (5-20ug/kg/min) Epinephrine (2-10ug/min) Isoproteronol (2-10ug/min) |
Supraventricular Tachycardia (Strip) | Rate: usually 150-250 Rhythm: Regular P Wave: Present for each QRS complex, normal configuration, and each P wave is identical PR Interval: Normal QRS Complex: Normal T Wave: Normal |
Supraventricular Tachycardia (Etiology) | Cause not typically associated with heart disease |
Supraventricular Tachycardia (Manifestation) | Palpitations, angina, lightheadedness, fatigue SOB, dyspnea Change in LOC |
Supraventricular Tachycardia (Medical Management) | Determine Pt tolerance of dysrhythmia Focus is aimed at decreasing the heart rate and eliminating the underlying cause Adenosine: 6mg-12mg-12mg |
Atrial Flutter (Strip) | Rate: Variable Rhythm: Regular or irregular P Wave: Multiple P's/QRS PR Interval: Varies (have to count it) QRS complex: Varies T Wave: May not be visible |
Atrial Fibrillation (Etiology) | Atherosclerosis Cardiac surgery, acute MI Mitral valve disease, cardiac stretch Digitalis preparations HF, cardiomyopathy, HTN, volume overload COPD (Chronic Obstructive Pulmonary Disease) Thyrotoxicosis |
Atrial Flutter/Fibrillation (Manifestations) | Palpations Lightheadedness Syncope Angina Change in LOC Pulmonary Edema Decreased Cardiac Output Thrombi form that may cause embolism |
Atrial Flutter/Fibrillation (Medical Management) | Focused on controlling rate, converting rhythm and providing anticoagulation. Synchronized cardioversion: if unstable, or unresponsive to meds Calcium channel Blockers Digoxin Amiodarone Heparin/Coumadin |
Amiodarone | used to help keep the heart beating normally in people with life-threatening heart rhythm disorders of the ventricles (the lower chambers of the heart that allow blood to flow out of the heart). |
Atrioventricular Blocks | A defect in the AV slows or impairs conduction |
3 Types of Atrioventricular Blocks | First Degree AV Block Second Degree AV Block (Types I & II) Third Degree AV Block |
First Degree AV Block (Strip) | Delayed conduction through the AV Node causes prolonged PR INterval |
Second Degree AV Block (Type I) | Mobitz I Wenckelbach |
Second Degree AV Block (Type II) | Mobitz II Classical |
Third Degree AV Block | Complete Heart Block complete AV Dissociation |
Premature Ventricular Contractions | Extra, abnormal heartbeats that begin in one of your heart's two lower pumping chambers (ventricles). |
Premature Ventricular Contractions (Etiology) | Irritability of the ventricular musculature |
Premature Ventricular Contractions (Strip) | Rate: Varies Rhythm: Usually regular w/ PVC coming earlier than next expected P Wave: No t visible, hidden in the PVC PR interval: not visible QRS Complex: Wide and bizarre (greater than 0.12 seconds "sore-thumb" appearance) T Wave:dflect opposite QR |
Premature Ventricular Contractions (P Wave) | the SA node continues to transmit impulses- but the impulses does not reach the ventricles because the ventricle is depolarized by the PVC |
Premature Ventricular Contractions (Medical Management) | Focus on treating the underlying cause. Evaluate Electrolytes Assess for hypoxia and treat prn Monitor for effect on hemodynamics |
Ventricular Tachycardia (Strip) | Rate: 140-240 BPM Rhythm: Regular Pwave: not visible QRS Complex: wide and bizarre (Greater than 0.12 secs) T Wave: usually deflected opposite to the QRS complex & difficult to see |
Ventricular Tachycardia (P Wave) | SA node continues to transmit impulses normally, until it becomes hypoxic, but impulses are not transmitted to ventricle, as ectopic focus is depolarizing ventricles |
Ventricular Tachycardia (Etiology) | Acute MI, Hypoxemia, Metabolic Acidiosis (especially lactic acidosis), Electrolyte disturbances (K+ & Mg+), Toxicity to certain drugs, such as digitalis or isoproterenol |
Ventricular Tachycardia (Clinical Manifestations) | Fatigue, SOB, Dyspnea, Lightheadedness, syncope, hyptotension, shock, chest pain, pulselessness |
Ventricular Tachycardia (Medical Management) | Depends on if rhythm os stable or unstable and whether VT is confirmed or suspected. |
Ventricular Tachycardia (Drug Therapy) | Amidarone, Lidocane, Magnesium, Procinamide |
Ventricular Fibrillation | Rapid and disorganized ventricular pulsation. Produces clinical death & must be reversed immediately, or Pt will die. SAWTOOTH!!! |
Ventricular Fibrillation (Strip) | Rate: Unmeasurable Rhythm: Irregular P Wave: Not present PR Interval: Not present QRS Complex: Not measurable (no definable complexes) T Wave: not present |
Ventricular Fibrillation (Etiology) | Myocardial ischemia or infarct Deteriorating ventricular rhythms (such as V-Tach) Acidosis Electrolyte imbalances Hypothermia Digitalis or quinidine toxicity |
Ventricular Fibrillation (Manifestations) | Loss of conciousness Loss of pulse, respiration and blood pressure Death |
Ventricular Fibrillation (Management) | Check pulse Airway: open the airway Breathing Circulation |
Abnormality in ST | Rate too high |
Abnormality in SB | Rate too low |
Abnormality in SVT | Rate too high May also have shortened PR interval |
Abnormality in A Flutter | Atrial rate too high May be irregular Ventricular rate may also be high |
Abnormality in A Fib | No P waves Irregularly irregular Ventricular rate may also be high |
Abnormality in First Degree AV Block | Prolonged PR interval |
Abnormality in Second Degree AV Block (Type I) | Irregular Consecutively prolonged PR interval until a QRS complex is dropped More Ps than QRSs |
Abnormality in Second Degree AV block (Type II) | Irregular P waves are not conducted More Ps than QRSs |
Abnormality in Third Degree AV Block | No relationship between P and QRS More Ps than QRSs Prolonged QRS |
Abnormality in PVC | Prolonged QRS |
Abnormality in V Tach | Rate too high No visible P waves QRS prolonged |
Abnormality in V Fib | No discernible waveforms |
Antiarrhythmic Agents | Suppression of cardiac arrhythmias |
Antiarrhythmic Agents (Action) | Correct arrhythmias bey a variety of mechanisms, depending on the group used |
Antiarrhythmic Agents (Therapeutic Goal) | Dcrease symptomatology and increase hemodynamic performance. |
Antiarrhythmic Agents (Choice) | Depends on etiology of arrhythmia and individual patient characterisitc |
Antiarrhythmic Agents Class 1A (Drug) | Disopyramide Procainamide Quinidine |
Antiarrhythmic Agents Class 1B (Drug) | Lidocane |
Antiarrhythmic Agents Misc (Drug) | Adenosine Digoxin |
Antiarrhythmic Agents 1A (Mechanism) | Depresses Na conductance, increases action Potential duration (APD) and effective refractory period (ERP), decreases membrane responsiveness |
Antiarrhythmic Agents 1B (Mechanism) | Increases K conductance, decreases APD and ERP |
Antiarrhythmic Agents Misc. (Mechanism) | Slows conduction through the AV node. Decreases conduction velocity and prolongs the effective refractory period in the AV node. |
Antiarrhythmic Agents Nursing Implications | Monitor BP, Pulse, and ECG before and routinely throughout therapy. Check Apical pulse before administering meds. Withhold if <50 or >120bpm. Monitor I&Os and daily weights. |
Cardioversion | Used for tachydysrhythmias when pharmacological intervention has been unsuccessful or the patient is compromised by a decreased cardiac output. |
Current is discharged during cardioversion | At the QRS Complex |
Pacemaker | Battery-operated device that initiates and controls the heart rate Used for patients with bradydysrhythmias, tachydysrhythmias, or 2nd and 3rd degree heart block that cannot be controlled with medications alone |
Pacemaker dysfunction S/S | Change in LOC, Bradycardia, Hypotension |