LPN Questions

• The heart's electrical conduction system starts an impulse stimulating mechanical cells to contract.
• Electrical activity is seen on a cardiac monitor/ ECG tracing.
• ECG activity does not prove mechanical cells contracted, physical data (blood pressure, apical/peripheral pulses) verifies if contraction/perfusion occurred.

Cardiac Cycle Components

• The electrical representation of the cardiac cycle is a P wave, QRS complex, and a T wave.
• Small squares on ECG graph paper are 0.04 seconds wide and one-half of a square is 0.02 seconds wide.
• Intervals of a cardiac cycle tracing are measured in seconds on ECG graph paper.
• Waveforms are measured horizontally and height measured vertically
• The isoelectric line (baseline) appears when there's no electrical current.
• The paper shows a straight line if there are no positive (upward) or negative (downward) electrical wave deflections present.

Cardiac cycle waves

• P wave represents atrial depolarization
• Electrical impulse spreads from the SA node from the right to the left atrium.
• A normal P wave is rounded and looks like a small hill.
• Disorders altering atrial size change P-wave shape/size.
• The PR interval (PRI) measures the time for the electrical impulse to travel from the SA node to the AV node, typically 0.12-0.20 seconds.
• One can calculate PRI by multiplying the number of small squares horizontally that the PRI covers, by 0.04.
• To remember PR interval of 0.12 to 0.20 seconds, use the R to recall normal respiratory rate of 12-20 breaths per minute.

Waves measurement

• Place a straight-edged item along the isoelectric line to measure waveforms.
• The QRS complex represents ventricular depolarization
• It consists of Q, R, and S waves but all waves are not always present

QRS waves

• The Q wave is the first downward deflection after the P wave.
• The R wave is the first upward deflection after the P wave.
• The S wave is the first negative deflection after the R wave.
• The normal QRS interval is 0.06 to 0.10 seconds (1.5 to 2.5 boxes).
• It measures the time for the electrical impulse to travel from the AV node rapidly through the ventricles.
• The QRS complex is larger than the P wave due to the ventricles having larger muscle mass.
• The T wave represents ventricular repolarization and is a rounded wave with positive deflection.
• An inverted T wave can indicate cardiac ischemia.

Wave Time Frames

• The QT interval of 0.34 to 0.43 seconds measures ventricular depolarization and repolarization.
• QT intervals vary based on gender, heart rate, and age. Prolonged/shortened QT intervals can cause ventricular arrhythmias.
• ST segment reflects the time from completion of contraction (depolarization) to myocardial muscle recovery (repolarization).
• The ST Elevation indicates transmural ischemia.
• The ST segment is checked when patients experience chest pain and ends at the beginning of the T wave.

Rhythm interpretation

• A systematic method increases understanding and avoids overlooking items of measure.
• Six steps identify the ECG rhythm and measure the QT interval.
• Rhythm regularity is determined by the R-to-R spacing, where the same spacing indicates normal rhythm.
• Calipers measure R-to-R spacing with accuracy
• Regularity is determined by counting the number of small squares between each R wave which should be the same number in a regular rhythm.
• If a caliper isn't available, make marks at the peak of one R wave and the following R wave on a piece of paper, then determine rhythm regularity.

Heart Rate

• Count small squares between two R waves and divide that number into 1,500 to determine one minute heart rate for regular rhythms.
• Multiply the number of R waves in a 6-second ECG strip by 10 to obtain bpm for irregular rhythms.
• Assess P waves to see if there is one P wave in front of every QRS, if they are regularly occurring, and if they look alike. If so, they are normal.
• All PR intervals are measured to determine if they are normal- 0.12-0.20 seconds.
• Measure QRS complexes to determine whether all complexes fall in normal range (0.06- 0.10 seconds).

Sinus Rhythms

• Normal sinus rhythm(NSR) originates in the SA node. The NSR has complete regular cardiac cycles at 60 to 100 bpm.
• An arrhythmia is an abnormal heart rhythm due to disturbances in impulse formation or conduction.
• Impulses may arise from the atria, AV node, or ventricles, leading to increased/decreased heart rate or fibrillation if impulse formation is disturbed.
• SA node rhythms are referred to as sinus rhythms: disturbances can cause irregular heart rhythms/rates, rarely dangerous, and may require treatment if heart, lung, or kidney disease is present.
• Use the origin and problem to name an arrhythmia.
• Sinus bradycardia has the same cardiac cycle components as NSR but has a heart rate of less than 60 bpm
• Well-conditioned athlete's hearts can have slow heart rates.
• Electrolyte imbalances, digoxin, or MI can cause bradycardia.

Bradycardia symptoms

• Decreased blood pressure, respiratory distress, diminished/absent peripheral pulses, fatigue, or syncope indicates symptomatic bradycardia
• Asymptomatic bradycardia requires observation and identification/correction of cause.
• Treatment includes IV atropine or infusions of dopamine/epinephrine.
• Transcutaneous pacing is used if atropine is ineffective, and transvenous pacing can be considered.
• Sinus tachycardia is a heart rate greater than 100 bpm originating from the SA node, where the heart rate is: 101 to 180 bpm.
• Tachycardia: P waves are rounded, upright, precede each QRS complex alike, PRI: 0.12 to 0.20 seconds, QRS Interval: 0.06 to 0.10 seconds.
• A very rapid and sustained rate (usually greater than 150 bpm) causes angina, dyspnea, syncope, or tachypnea.
• Older patients can become symptomatic more rapidly and may not tolerate a rapid heart rate
• Medications, such as adenosine, beta blockers, and calcium channel blockers, slow the elevated heart rate when equal to or greater than 150 bpm.

Atrial Arrhythmias

• Factors increasing the risk of arrhythmias in older adults include Digitalis toxicity, hypokalemia, angina, Coronary insufficiency, sleep apnea, hypothyroidism or hyperthyroidism
• Arrhythmias occurring most often in older adults include atrial fibrillation and sick sinus syndrome.
• Older adults have less ability to adapt to stressors or sudden changes and may be unable to tolerate tachycardia.
• If the atria initiate impulses faster than the SA node (greater than 100 bpm), the atria becomes the primary pacemaker and have faster atrial rhythms.
• A QRS complex measuring 0.06 to 0.10 seconds indicates a problem originating above the ventricles, known Supraventricular arrhythmia while ventricular arrhythmias are greater than 0.10 seconds.

Premature Contractions

• Premature atrial contractions (PACs) occur when the atria fire an impulse before the SA node with early beats.
• Causes of PACs are cigarette smoking, electrolyte imbalances, hypoxia, stress, medications such as digoxin), enlarged atria in valvular disorders
• Rhythm in premature atrial contractions include premature beats interrupting the underlying rhythm, with abnormally shaped P waves.
• An early beat that occurs abnormally can either shorten or prolong PRI.
• PACs can occur in healthy/diseased hearts: patients may report feeling palpitations.
• Frequent PACs indicate atrial irritability which can worsen with other atrial arrhythmias.
• Atrial flutter causes the atria to contract (or flutter) at 250-350 bpm- very rapid P waves that appear as flutter (F) waves that have a sawtooth pattern.
• The ventricular rate and adequacy of cardiac output guide the treatment and conversion measures back to NSR.
• Causes include heart failure, HTN, rheumatic/ischemic heart diseases, post bypass or pulmonary embolism.

Atrial Fibrillation

• Atrial fibrillation increases with age 65 and above, especially in those with heart disease with heart rate of 350 to 600 bpm.
• There are no definable P waves because the atria are fibrillating (quivering).
• AF is identified by lack of identifiable P waves and an irregular rhythm.
• Most patients feel the irregular rhythm.
• Therapeutic measures focus on rate control, prevention of thromboembolism, and normal rhythm restoration.

Heart Blocks

• In third-degree AV block, the SA node impulses are blocked with use of escape pacemakers to stimulate the ventricles to contract or else cardiac arrest will occur.
• Causes includes digoxin toxicity or cardiac ischemia
• The QRS complex will be narrow (junctional) or wide (ventricular).
• P waves march across the ECG strip at a steady rate
• Severe symptoms, such as confusion, dyspnea, severe chest pain, hypotension, or syncope, are seen in Atrioventricular blocks.

Ventricular Arrhythmias

• Premature ventricular contractions (PVCs) originate in the ventricles from an ectopic focus resulting in wide/bizarre QRS complex greater than 0.10 seconds.
• PVC rhythms depends on the underlying rhythm and usually interrupts it and have absent P waves before QRS Complex
• Repetitive cycles of PVCs include bigeminy (every other beat) or trigeminey (every third beat).
• PVCs can trigger life-threatening arrhythmias or are caused by an acute MI
• High PVCs can decrease cardiac output, leading to fatigue/dizziness
• Treatment depends on type and number of PVCs and whether the symptoms are produced. If the PVCs are more than six per minute, consult the HCP.

Ventricular Tachycardia & Fibrillation

• Ventricular tachycardia (VT) includes three or more PVCs in a row with ectopic focus, where VT results from the continuous firing of an ectopic ventricular focus causing dyspnea, palpitations, and lightheadedness.
• The rate is 150 to 250 ventricular bpm
• Ventricular fibrillation (VF) occurs when many ectopic ventricular foci fire at the same time, causing no discernible waves or cardiac output, which leads to death if not corrected immediately with defibrillation.
• The heart is chaotic as it quivers
• Hyperkalemia and hypomagnesemia are main causes of VF
• VF and asystole causes unconsciousness and unresponsiveness, where there are no heart sounds or blood pressure readings.
• CPR/ endotracheal intubation should be conducted.
• Asystole has no electrical activity within the cardiac muscle, no heart sounds, peripheral pulses, blood pressure readings, or respirations.

Pacemakers

• Cardiac pacemakers generate electrical impulses for heart rhythm irregularities.
• Temporary pacemakers are used to treat bradycardia/tachycardia or after an MI through cardiac conduction system stimulating atrial and ventricular contractions.
• They're quick and easy to apply through external generator electrodes on the chest/back.
• Permanent pacemakers treat symptomatic bradycardia/third-degree AV block using fluoroscopy.
• After being implanted subcutaneously, it is hooked to insulated wires into the heart, delivering impulse to the heart wall.
• Problems occurring include the failure to pace due to generator malfunction
• Patients’ incisions and heart rhythm are monitored after implantation of a pacemaker.
• Irregular rhythm or slower rate than the set rate can cause malfunction.
• Pacemakers should not fire during a patient's own beat

Cardioversion and Defibrillation

• Defibrillation is a lifesaving procedure for VT/VF
• Electrical shock to reset rhythm
• Defibrillation requires self-adhesive conductive pads
• Defibrillation is followed by a pulse check and adequate tissue perfusion.
• Nursing care includes providing emotional support for patients, monitoring for burns, rhythm disturbances, vital sign changes, and respiratory problems.
• Cardioversion is performed with a defibrillator in synchronized mode with a sedative.
• Other methods to correct arrhythmias include automatic external defibrillators