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WVC Cardiac Chpt 36

Med Surg/ Iggy chapter 36 Cardiac

What are the abnormal rhythms of the heart's electrical system that can affect its ability to effectively pump OXYGENATED blood throughout the body called: Cardiac dysrhythmias are the result of disturbances of cardiac electrical impulse formation, conduction, or both.
How is circulation affected by dysrythmias? When the heart does not work effectively as a pump, perfusion to vital organs and peripheral tissues can be impaired, resulting in organ dysfunction or failure
What specialized cardiac muscle cell properties regulate heart rhythms? (Hint 3 properties) Specialized cardiac muscle cells possess unique properties: automaticity, excitability, conductivity, and contractility.
What is the name of cardiac property that has the ability to generate an electrical impulse spontaneously and repetitively (depolarization without stimulation from the nervous system) Automaticity
What heart cells undergo spontaneous depolarization the fastest and are responsible to set the heart's REGULAR rhythm? PRIMARY PACEMAKER cells
Where is automaticity most often demonstrated? In the sinoatrial node (SA), the so called "Pacemaker of the Heart."
How is automaticity possible? Plasma membranes within the heart that have reduced permeability to potassium (K+) but still allow passive transfer of calcium ions, allowing a net charge to build.
What are the Primary Pacemaker cells? (Pacemaker of the Heart) sinoatrial [SA] node, atrioventricular [AV] junction
What property has the ability of non-pacemaker heart cells to respond to an electrical impulse generated from pacemaker cells and to depolarize? Excitability
This occurs when the normally negatively charged cells within the heart muscle develop a positive charge. Depolarization
What property has the ability to transmit an electrical stimulus from cell membrane to cell membrane. As a result, excitable cells depolarize in rapid succession from cell to cell until all cells have depolarized. Conductivity
What waves (P,Q,R,S,T)are caused by depolarization? P wave and QRS complex
What property has the ability of atrial and ventricular muscle cells to shorten their fiber length in response to electrical stimulation, generating sufficient pressure to propel blood forward. (AKA mechanical activity of the heart) Contractility
What provides provides a graphic representation, or picture, of cardiac electrical activity ECG electrocardiogram
Where is the SA node located? close to the surface of the right atrium near its junction with the superior vena cava.
The conduction system consists of the? sinoatrial node, atrioventricular junctional area, and bundle branch system (Bundle of His)
How many BPM does the SA node generate? 60 to 100 beats per minute
The SA node is richly supplied by the Sympathetic and parasympathetic nervous system
The SA node depolarizes and can be seen in which wave? P wave- it's the sign of a normal sinus rhythm
The atrioventricular (AV) junctional area consists of? a transitional cell zone, the AV node itself, and the bundle of His.
Where is the AV node located? just beneath the right atrial endocardium, between the tricuspid valve and the ostium of the coronary sinus.
What is the function of the transitional cells (T-cells) in the AV node? To slow down or delay the impulses before they proceed to the ventricles.
How is the AV node identified on an ECG? What is the purpose of the slow down? This delay is reflected in the PR segment on the ECG. This slow conduction provides a short delay, allowing the atria to contract and the ventricles to fill.
Where is the Bundle of His located? It connects with the distal portion of the AV node and continues through the interventricular septum
What is the measurement of ONE small square on the ECG graph paper? 1 mm in height and width.
ECG recorders and monitors are standardized at a speed of? 25 mm/sec
Time is measured on the? Horizontal axis Electrocardiographic waveforms are measured in amplitude (voltage) and duration (time)
At the standard speed, each small block represents how much time on a standard sheet? 0.04 OF A SECOND
Five small blocks make up one large block, defined by darker bold lines and representing how much time on a standard ECG sheet? 0.20 of a second
Five large blocks represent how much time on a standard ECG sheet? 1 second
30 large blocks represent how much time on a standard ECG sheet 6 seconds
Vertical lines in the top margin of the graph paper are usually... 15 large blocks apart, representing 3-second segments
Complexes that make up a normal ECG consist of? P wave, a QRS complex, a T wave, and possibly a U wave. Segments include the PR segment, the ST segment, and the TP segment.
To arrive at a minute estimate for the ventricular rate, count the QRS complexes in a 6-second strip and then multiply that number by 10
The _______ wave is a deflection representing atrial depolarization. P wave
The P wave is generated from the _______ node. SA node
What is an indication that the P wave has been initiated from a node other than the SA node? It will be inconsistent in shape. (Remember that the property of Automacity makes any cardiac cell capable of an action potential)
What is the isoelectric line from the end of the P wave to the beginning of the QRS complex called? The PR segment
The _______ wave is a deflection representing atrial depolarization. P wave
The P wave is generated from the _______ node. SA node
What is an indication that the P wave has been initiated from a node other than the SA node? It will be inconsistent in shape. (Remember that the property of Automacity makes any cardiac cell capable of an action potential)
What is the isoelectric line from the end of the P wave to the beginning of the QRS complex called? The PR segment.
The PR segment normally measures? (time) 0.12 to 0.20 second (five small blocks)
This complex represents ventricular depolarization. QRS complex
The PR segment represents? The time required for atrial depolarization as well as the impulse delay in the AV node and the travel time to the Purkinje fibers.
This wave is the first negative deflection and is not present in all leads. The Q wave
This wave is the first positive deflection. The R wave
This wave is a negative deflection following the R wave and is not present in all leads The S wave
This duration represents the time required for depolarization of both ventricles. The QRS duration
The QRS duration normally measures (time) 0.04 to 0.10 second (up to three small blocks).
This segment is normally an isoelectric line and represents early ventricular repolarization. The ST segment
ST elevation or depression can be caused by ? myocardial injury, ischemia or infarction, conduction abnormalities, or the administration of medications.
This wave follows early ventricular repolarization T wave
If an ectopic stimulus excites the ventricles during this time (T wave), it may cause ventricular irritability, lethal dysrhythmias, and possible cardiac arrest in the vulnerable heart,
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.
when present, follows the T wave and may result from slow repolarization of ventricular Purkinje fibers u wave
This interval represents the total time required for ventricular depolarization and repolarization QT interval
The QT interval is measured from the beginning of the ______ complex to the end of the T wave. QRS
What is interference seen on the monitor or rhythm strip, which may look like a wandering or fuzzy baseline Artifact
Normal heart rates fall between 60 and 100 beats/min.
A rate less than ________ is called bradycardia. 60 beats/min
A rate greater than ________ is called tachycardia. 100 beats/min
Ask these five questions when analyzing P waves: • Are P waves present? • Are the P waves occurring regularly? • Is there one P wave for each QRS complex? • Are the P waves smooth, rounded, and upright in appearance, or are they inverted? • Do all the P waves look similar?
Ask these three questions about the PR interval: •Are PR intervals greater than 0.20 second? •Are PR intervals less than 0.12 second? •Are PR intervals constant across the ECG strip?
The QRS duration normally measures between 0.04 and 0.10 second.
When the QRS is narrow (0.10 second or less), this indicates that the impulse was not formed in the ventricles and is referred to as supraventricular or above the ventricles.
Ask these questions to evaluate QRS intervals: • Are QRS intervals less than or greater than 0.12 second? • Are the QRS complexes similar in appearance across the ECG paper?
When the QRS complex is wide (greater than 0.10 second), this indicates that the impulse is either of ventricular origin or of supraventricular origin with aberrant conduction, meaning deviating from the normal course or pattern.
More than one QRS complex pattern or occasionally missing QRS complexes may be observed, indicating a ______________ dysrhythmia.
Normal sinus rhythm (NSR) is the rhythm originating from the sinoatrial (SA) node (dominant pacemaker) that meets these ECG criteria 1. RATE: Atrial and ventricular rates of 60 to 100 BPM AND RHYTHMS REGULAR 2. P WAVES Present, consistent configuration, one P wave before each QRS complex 3. PR INTERVVAL: 0.12 to 0.20 second and constant 4. QRS DURATION: 0.04 to 0.10 second and const
This rhythm is a variation of NSR and results from changes in intrathoracic pressure during breathing (the heart rate increases slightly during inspiration and decreases slightly during exhalation) Sinus arrhythmia (the term arrhythmia does not mean an absence of rhythm)
How is SINUS ARRHYTHMIA characterized •Rate: Atrial and ventricular rates are between 60 and 100 beats/min. •Rhythm: Atrial and ventricular rhythms are irregular, with the shortest PP or RR interval varying at least 0.12 second from the longest PP or RR interval.
Sinus arrhythmias occasionally are due to nonrespiratory causes, such as Vomitting, digitalis or morphine. These enhance vagal tone and cause decreased heart rate and irregularity unrelated to the respiratory cycle.
Signs of sustained Tachydysrhythmias •Palpitations •Chest discomfort (pressure or pain from myocardial ischemia or infarction) •Restlessness and anxiety •Pale, cool skin •Syncope (“blackout”) from hypotension
Tachydysrhythmias are serious because they: •Shorten the diastolic time and therefore the coronary perfusion time •Initially increase cardiac output and BP, then reduce aortic pressure resulting in coronary perfusion pressure
Presenting symptoms of heart failure may include dyspnea, lung crackles, distended neck veins, fatigue, and weakness
Two benefits of bradycardia rhythms •Myocardial oxygen demand is reduced from the slow heart rate, which can be beneficial. •Coronary perfusion time may be adequate because of a prolonged diastole, which is desirable
Bradycardia can be serious because.. •Coronary perfusion pressure may decrease if the heart rate is too slow to provide adequate cardiac output and blood pressure; this is a serious consequence.
What are Premature complexes They occur when a cardiac cell or cell group, other than the sinoatrial (SA) node, becomes irritable and fires an impulse before the next sinus impulse is produced.
Dysrhythmias are classified according to their site of origin
The sites of origin for SINUS dysrhythmias are atrial, junctional, or ventricular tissue.
Increased sympathetic stimulation of the SA is a normal response to physical activity but may also be caused by anxiety, pain, stress, fear, fever, anemia, hypoxemia, hyperthyroidism, and pulmonary embolism.
Drugs that can cause SINUS tachycardia are catecholamines, atropine, caffeine, alcohol, nicotine, aminophylline, and thyroid medications may also increase the heart rate.
What are the s/s of SINUS tachycardia? Usually asymptomatic. decreased BP, SOB, fatigue, JVD, decreased O2 SAT
heart rate, 110 beats/min; PR interval, 0.12 second; QRS complex, 0.08 second Sinus tachy or brady? Tachy
the drug used to treat sinus bradycardia, when symptoms are present & the cause cannot be determined Atropine
Why does bearing down (as in a bowel movement) or excessive vomiting slow the HR It puts pressure on the vagus nerve. Common cause of bradycardia among the elderly
What drugs can induce brady beta-adrenergic blocking agents, calcium channel blockers, and digitalis.
Atropine A tropane alkaloid extracted from deadly nightshade, jimsonweed, mandrake and other plants of the family Solanaceae.
What is the classification of atropine an anticholinergic drug that is a competitive antagonist of the muscarinic acetylcholine receptors
What is atropine's action increases firing of the sinoatrial node (SA) and conduction through the atrioventricular node (AV) of the heart, opposes the actions of the vagus nerve, blocks acetylcholine receptor sites, and decreases bronchial secretions.
The most common atrial dysrhythmias are premature atrial complexes, supraventricular tachycardia, atrial flutter, and atrial fibrillation.
The causes of atrial irritability include: •Stress •Fatigue •Anxiety •Inflammation •Infection •Caffeine, nicotine, or alcohol •Drugs such as catecholamines, sympathomimetics, amphetamines, digitalis, or anesthetic agents
A premature atrial complex (PAC) occurs when atrial tissue becomes irritable such as myocardial ischemia, hypermetabolic states, electrolyte imbalance, or atrial stretch.
What teaching would you use for PAC Teach the patient measures to manage stress and substances to avoid that are known to increase atrial irritability.
Atrial stretch can result from congestive heart failure, valvular disease, and pulmonary hypertension with cor pulmonale.
How do you treat PAC No treatment, just treat the underlying condition (CHF)
Supraventricular tachycardia (SVT) involves the rapid stimulation of atrial tissue at a rate of __________ in adults and ______________ in children. 100 to 280 beats/min (adults) 200 to 300 beats/min (children)
What would an ECG look like with SVT No detectable P waves (they get buried in the T wave)
The preferred treatment for recurrent SVT is radiofrequency catheter ablation.
What are the drugs used in SVT Administer oxygen and prescribed antidysrhythmic drugs, such as diltiazem (Cardizem) or adenosine (Adenocard), which slow the ventricular rate by increasing the AV block
This is the most common dysrhythmia seen in clinical practice Atrial fibrillation (AF)
Risk factors for AF are hypertension (HTN) (the biggest risk factor), diabetes mellitus, male gender, congestive heart failure, and valvular disease
Risks associated with AF are Pulmonary embolism, systemic emboli, particularly an embolic stroke, which may cause severe neurologic impairment or death.
Signs of AF fatigue, weakness, shortness of breath, distended neck veins, dizziness, decreased exercise tolerance, anxiety, syncope, palpitations, chest discomfort or pain, and hypotension.
AF resistant to medical therapies may be treated with radiofrequency catheter ablation.
the goals of treating atrial fibrillation are to: Reset the rhythm or control the rate and prevent blood clots
What is cardioversion a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs
What are the drugs used in cardioversion Digoxin, atropine,quinidine, adenosine, beta blockers & calcium channel blockers
Beta-Adrenergic Antagonists, or Beta Blockers are used for angina, irregular HB, HTN and to prevent additional heart attacks
How do beta blockers work They decrease the heart's need for blood and oxygen and reduce its workload.
Calcium Antagonists, or Calcium Channel Blockers are used for These drugs help to slow abnormally rapid heartbeats. They also widen the blood vessels and may decrease the heart's pumping strength.
what diseases are calcium channel blockers used in high blood pressure, They may be used to treat heart faliure caused by a thickened heart muscle, hypertrophic obstructive cardiomyopathy
ACE inhibitors or angiotensin-converting enzyme inhibitors are used for primarily in treatment of HTN CHF cardiac failure, renal disease or systemic sclerosis
Atrial flutter is rapid atrial depolarization occurring at a rate of 250 to 350 times per minute
Atrial flutter may be caused b rheumatic or ischemic heart disease, heart failure (HF), AV valve disease, pre-excitation syndromes, septal defects, pulmonary emboli, thyrotoxicosis, alcoholism, or pericarditis.
How do you assess for atrial flutter Assess the patient for palpitations, weakness, fatigue, shortness of breath, nervousness, anxiety, syncope (loss of consciousness), angina, and evidence of heart failure and shock.
If the patient is severely compromised with atrial flutter what is the treatment Cardioversion. Rapid atrial overdrive pacing may be attempted or radiofrequency catheter ablation may be necessary if the patient does not respond to these therapies.
Created by: wvc