NRSG 441 - Exam 1

What are the 2 types of cardiac cells, and what are their properities?

Pacemaker cells: specialized cells of conduction system that can spontaneously generate and conduct impulses

• Automaticity: ability to generate an impulse spontaneously

Myocardial/Working Cells: mechanical cells responsible for contraction

• Excitability: ability to respond to outside stimulus

• Conductivity: ability to transmit an impulse to adjacent cells

• Contractility: ability to shorten and contract in response to stimulus

What are the 6 steps of the cardiac cycle?

1. Atrial diastole: atria fill; all valves close

2. Early atrial systole: ventricles fill, increased atrial pressure opens AV valves

3. Atrial systole/atrial kick: atria contract and empty, ventricles finish filling

4. Early ventricular systole: ventricles begin contraction and atria relax, pressure closes AV valves

5. Ventricular systole: ventricles contract and increased pressure opens SL valves, blood is ejected into aorta/pulmonary arteries

6. Early atrial diastole: ventricles empty and relax, SL valves close

What are the 6 steps of the heart’s conduction cycle, and what are the characteristics of each part?

1. SA Node: Generates impulse that starts the cardiac cycle

   • Located high in right atrium where SVC meets the RA

2. Internodal pathways (Bachmann’s Bundle): stimulates right then left atria (atrial stimulation)

3. AV Node: Delays the conduction of impulse from atria to ventricles to allow for ventricular filling

   • Located at floor of RA near septum

4. Bundle of His: Connects AV node with L/R bundle branches

5. Left and Right Bundle Branches: Conducts impulse to ventricles

   • Left bundle branch splits into fascicles

6. Purkinje Fibers: Receive impulse from BB and relay to ventricles

   • Fibers at very end of BB

What are the 3 pacemakers of the heart, and what are their intrinsic rates?

1. SA Node: Main pacemaker because it has the fastest rate of discharge (60-80bpm) and meets threshold faster (-65mV) → sets normal HR

2. AV node: latent/backup pacemaker → 40–60 bpm

3. Purkinje fibers: last-resort pacemaker → ~20–40 bpm

What are dysrhythmias and the 3 potential causes?

Abnormal cardiac rhythm that deviates from normal sinus rhythm (impulses generated from SA node)

1. Disorders of impulse formation

2. Disorders of impulse conduction

3. Impulse formation and conduction

What are ECG electrodes, and how do they transmit cardiac electrical activity to the ECG monitor?

1. Applied to specific locations on the chest wall and extremities.

2. One end of the monitoring cable attaches to the electrode.

3. The other end attaches to the ECG machine.

4. The cable conducts the detected electrical current/activity from the heart back to the cardiac monitor.

What is an ECG lead, and what determines the portion of the heart it “sees”?

1. A lead is a recording/tracing of the voltage difference between positive and negative electrodes.

   • Impulse toward the positive electrode → positive (upward) QRS

   • Impulse away from the positive electrode → negative (downward) QRS

2. The position of the positive electrode determines the portion of the heart viewed by that lead.

What 4 leads are used for bedside monitoring?

1. 3-lead and 5-lead systems → continuous monitoring

2. Lead II → best P-wave visibility; commonly used for rhythm monitoring

3. V1 → useful for distinguishing wide-complex rhythms

4. 5-lead system → includes Leads I, II, III + a chest lead

What are the positive/negative electrodes and heart surfaces viewed by Leads I, II, and III?

Lead	+ Electrode	− Electrode	Views

I

Left arm

Right arm

Lateral

II

Left leg

Right arm

Inferior

III

Left leg

Left arm

Inferior

Where do aVR, aVL, and aVF view the heart, and which heart walls do they assess?

1. aVR → right shoulder/right arm → no specific LV wall; normally mostly negative (inverted QRS)

2. aVL → left shoulder/left arm → lateral wall

3. aVF → left foot/leg → inferior wall

Where are V1–V6 placed, and what areas of the heart do they view?

Lead	Placement	Views
V1	4th ICS, right sternal border	Septum
V2	4th ICS, left sternal border	Septum
V3	Midway between V2 & V4	Anterior
V4	5th ICS, midclavicular line	Anterior
V5	Level with V4, anterior axillary line	Lateral
V6	Level with V4, midaxillary line	Lateral

Which ECG leads correspond to each area of the heart (5)?

1. Septal: V1, V2

2. Anterior: V3, V4

3. Lateral: I, aVL, V5, V6

4. Inferior: II, III, aVF

5. aVR: Right-sided view; does not correspond to a specific LV wall

What is ECG graph paper used for, and how are time and voltage measured?

ECG graph paper is used to standardize ECG tracings.

Horizontal = TIME

• 1 small box (1 mm) = 0.04 sec

• 1 large box (5 mm) = 0.20 sec

• 5 large boxes = 1 sec

• Standard paper speed = 25 mm/sec

Vertical = VOLTAGE / AMPLITUDE

• 1 small box (1 mm) = 0.1 mV

• 1 large box (5 mm) = 0.5 mV

• 10 mm (2 large boxes) = 1 mV → standard calibration (look for rectangular wave)

What are the baseline, waveform, segment, interval, and complex on an ECG?

1. Baseline (isoelectric line): straight line when electrical activity is not detected

2. Waveform: movement above (+) or below (−) the baseline

3. Segment: line between waveforms (ST segment)

4. Interval: waveform + segment (PR interval)

5. Complex: several waveforms grouped together (QRS complex)

What are the 8 major ECG sections and what does each waveform, segment, and interval represent?

1. P wave → atrial depolarization

2. PR interval → atrial depolarization + AV conduction/delay

3. QRS complex → ventricular depolarization

4. ST segment → early ventricular repolarization

5. T wave → ventricular repolarization

6. QT interval → total ventricular activity (depolarization + repolarization)

7. U wave → late Purkinje repolarization

8. TP segment → electrical baseline between cardiac cycles

What does the P wave represent, what are 5 characteristics of a normal P wave, and what are 2 indications of abnormalities?

P wave represents atrial depolarization (impulse spread through R/L atria)

1. Normal wave indicates impulse was initiated from the SA node

2. Smooth and rounded in shape

3. Positive in I, II, aVF

4. Duration: < 0.12 sec (<3 small boxes)

5. Amplitude: ≤ 0.25 mV (≤2.5 small boxes)

Abnormalities

1. Duration ≥0.12 sec → consider left atrial enlargement / aberrant conduction

2. Tall P wave >2.5 mm → consider right atrial enlargement (P pulmonale)

What does the PR interval represent, what are 3 characteristics of a normal PR interval, and what are 2 indications of abnormalities?

PR interval = atrial → ventricular conduction time (AV nodal delay)

1. Measured from beginning to P wave to beginning of QRS

2. Normal: 0.12–0.20 sec = 3–5 small boxes

Abnormalities

1. Short PR (<0.12 sec) → pre-excitation/WPW

2. Long PR (>0.20 sec) → delayed AV conduction / 1st-degree AV block

What does the QRS complex represent, what are 4 characteristics of a normal QRS complexl, and what are 1 indication of abnormalities?

QRS = ventricular depolarization → represents spread of the electrical impulse through the ventricles/Purkinje system.

1. Normal: 0.06–0.12 sec (1.5–3 small boxes)

2. Q = first negative deflection

3. R = first positive deflection

4. S = negative deflection after R

   • Not every QRS has all 3 waves

Abnormalities

1. Long/wide QRS ≥0.12 sec → bundle branch block, ventricular rhythm, Pre-excitation

How are the Q, R, and S waves identified within the QRS complex?

• Q wave: first negative/downward deflection → represents interventricular septal depolarization

• R wave: first positive/upward deflection

  • Tall and positive in all limb leads except for aVR and V1

• S wave: negative/downward deflection following the R wave

• R + S waves: represent depolarization of the right and left ventricles

How do normal and pathologic/abnormal Q waves differ?

Normal: <0.03 sec; may not always be present

Pathologic Q wave: Width >0.04 sec; Depth >¼ the height of the following R wave

• May be seen on the ECG of a patient with a history of acute MI.

What does the ST segment represent, what are 3 characteristics of a normal ST segment, and what are 2 indications of abnormalities?

ST segment = early ventricular repolarization

1. Located between the QRS complex and T wave

2. Normally isoelectric (flat/baseline)

3. J point = junction where the QRS ends and ST segment begins

Abnormalities

1. ST elevation → myocardial injury/STEMI

   • 1mm or more

   • 2mm or more in men and 1.5mm or more in women

2. ST depression → myocardial ischemia or digoxin

What does the T wave represent, what are 4 characteristics of a normal T wave, and what are 3 indications of abnormalities?

T wave = ventricular repolarization

1. Follows the QRS

2. Slightly asymmetric

3. Usually upright/positive (2-5mm)

4. Typically larger than the P wave

Abnormalities

1. Inverted/flattened T wave → consider ischemia

2. Tall, peaked T wave → consider hyperkalemia

3. Changes can occur with electrolyte disturbances, myocardial ischemia, or injury

What does the QT interval represent and what are 4 characteristics of a normal QT interval

QT interval = total ventricular electrical activity (depolarization and repolarization)

1. Measures beginning of QRS to end of T wave

2. Includes QRS + ST segment + T wave

3. Varies with HR

   • Faster HR → shorter QT (short if <0.39sec)

   • Slower HR → longer QT (long if >0.46 in women or 0.45 in male)

4. QT is generally <½ the R–R interval

Why is a prolonged QT/QTc clinically important?

• QTc corrects the QT for variations in HR to determine whether ventricular repolarization is truly shortened/prolonged

  • Male: <0.47 sec

  • Female: <0.48 sec

• Prolonged QT means ventricular repolarization is taking too long → increasing the risk for fatal ventricular dysrhythmias.

  • QTc >500 ms(>0.50sec) = HIGH risk for Torsades

What does the U wave represent, what are 3 characteristics of a normal U wave, and what are 3 indications of abnormalities?

U wave = Represents late repolarization of Purkinje fibers

1. Small wave sometimes seen after the T wave (and same direction)

2. More easily seen with a slow HR

3. Usually <2 mm in height (2 small boxes)

Abnormalities (prominent U waves)

1. Hypokalemia

2. Cardiomyopathy

3. Digoxin toxicity

What is the TP segment and what are 3 characteristics of it?

TP segment: from the end of the T wave → beginning of the next P wave

1. Represents a period of no detected electrical activity

2. Normally isoelectric

3. Often used as the reference baseline when determining ST-segment elevation or depression

What is an ECG artifact?

Distortion of an ECG tracing. caused by electrical activity that is non-cardiac in origin

• Can mimic cardiac dysrhythmias

• Always assess the patient before treating a dysrhythmia (may be an artifact)

What are 5 causes of a muscle (EMG) artifact, what does it look like, and how is it corrected?

Type: Internal artifact

Causes:

• Patient movement

• Shivering

• Muscle tremors

• Tense muscles

• Coughing

Appearance:

• Irregular, high-frequency fuzzy baseline

• Can mimic AFib or VF

Fix:

1. Reposition electrodes away from muscle

2. Reduce patient movement

3. Calm patient

4. Treat shivering

What are 2 causes of 60-Hz electrical artifact, what does it look like, and how is it corrected?

Type: External artifact

Causes:

1. Electrical equipment interference

   • IV pumps

   • Ventilators

   • Lighting

2. Equipment/connection problems

Appearance:

• Regular, uniform, fine oscillations on the baseline

• Occur at 60 cycles/sec

Fix:

• Check equipment connections

• Ensure proper grounding

• Eliminate crossed wires

• Replace electrodes if needed

What are 4 causes of wandering baseline artifact, what does it look like, and how is it corrected?

Type: Can have internal and external causes

Internal causes:

• Respiratory movement

• Patient movement

• Diaphoresis

External cause:

• Loose electrodes

Appearance:

• Baseline drifts up and down

• Can make ST-segment analysis unreliable

Fix:

• Re-prep skin

• Replace/resecure electrodes

• Move leads away from respiratory movement

• Reduce patient motion

What are 3 causes of loose lead/lead-off artifact, what does it look like, and how is it corrected?

Type: External artifact

Causes:

• Electrode detachment/loose electrode

• Broken lead wire

• Dry electrode

Appearance:

• Flat line or chaotic activity in ONE lead

• Other leads remain normal

Fix:

• Check all connections

• Replace/resecure electrode

• Inspect lead wires

How do you determine whether the atrial and ventricular rhythms are regular or irregular?

1. Ventricular regularity: compare R–R intervals

2. Atrial regularity: compare P–P intervals

   • Regular: intervals are equal

   • Irregular: intervals are unequal

3. Variation of approximately ±10% is acceptable

Patterns:

• Regularly irregular: irregularity follows a repeating pattern

• Irregularly irregular: no pattern to the irregularity → classic example: AFib

Which method should be used to calculate heart rate based on rhythm regularity?

Regular rhythm:

• 300/large box method → 300 ÷ large boxes between 2 consecutive R or P waves

• 1500/small box method → 1500 ÷ small boxes between 2 consecutive R or P waves

  • More accurate but time-consuming

Irregular rhythm:

• 6-second method → count QRS × 10 in 6 second strip

  • Calculate atrial and ventricular rates separately

What should 5 things should you assess about the P waves when analyzing a rhythm strip?

Look to the left of each QRS and ask:

1. Are P waves present?

2. Are they upright and uniform?

3. Do they look alike in size, shape, and position (round and smooth)?

4. Is there one P wave before every QRS?

5. Do P waves occur regularly?

How is the PR interval assessed during rhythm interpretation?

Measure from the:

Beginning of P wave → beginning of QRS

Normal: 0.12–0.20 sec

Then determine whether PR intervals are:

1. Constant → same throughout strip

2. Progressively lengthening

3. Variable → changing with no pattern

What 4 things should you assess about the QRS complexes when interpreting a rhythm strip?

1. Identify each QRS

2. Measure QRS duration (0.06-0.10)

3. Compare QRS complexes for shape/consistency

4. Determine whether QRS is narrow or wide

What 5 things should you assess about the ST segment and T wave during rhythm interpretation?

ST segment:

• Normally isoelectric

• Look for ST elevation or depression

T wave:

• Upright?

• Normal height?

• Flat, inverted, or peaked?

What 8 things should be assessed systematically when interpreting an ECG rhythm strip?

1. Rhythm/regularity → compare R–R and P–P

2. Rate → atrial and ventricular

3. P waves → present? upright? uniform? one per QRS?

4. PR interval → measure and determine if constant

5. QRS → measure duration; narrow or wide?

6. ST segment/T wave → elevation/depression? T-wave abnormalities?

7. Identify the rhythm

8. Assess the patient → correlate rhythm with symptoms/stability

What is enhanced automaticity, and are 5 causes?

Enhanced automaticity: a cardiac cell other than the SA node spontaneously fires at a faster rate, allowing it to compete with or override the SA node.

Ex. PACs, PVCs, Accelerated junctional rhythm

Causes

1. Hypoxia

2. Ischemia

3. Digitalis toxicity

4. Catecholamines

5. Electrolyte imbalances

Treatment principle: Correct the underlying cause of the increased automaticity.

What is re-entry, what 3 conditions are required for it to occur, and are 3 examples?

Re-entry: an electrical impulse travels repeatedly in a circular loop, re-exciting cardiac tissue.

Ex. Afib, SVT, VT

Requires:

1. Two conduction pathways

2. Unidirectional block in one pathway

3. Slow conduction in one pathway, allowing previously refractory tissue time to recover

Treatment principle: Interrupt the re-entry circuit → e.g., adenosine or cardioversion depending on the rhythm/clinical situation.

What 8 findings indicate that a patient with a dysrhythmia is hemodynamically unstable?

1. Hypotension: SBP <90 mmHg or >30 mmHg drop from baseline

2. Altered mental status

3. Shock (sweating, pallor, cool extremities)

4. Angina/chest pain

5. Acute pulmonary edema/severe dyspnea

6. Poor perfusion (oliguria, lactic acidosis)

What 5 findings indicate that a patient with a dysrhythmia is hemodynamically stable, and what 4 things should be done next?

1. Adequate BP

2. Alert/mentally clear

3. No signs of shock

4. Tolerating symptoms

5. No evidence of significant poor perfusion

   • Obtain 12 lead ECG, check labs, review medications, notify provider

What are 3 premature complexes, and where can they originate?

Premature complexes are beats that occur early, before the next expected beat.

1. Atria → PAC (premature atrial contraction)

2. AV junction → PJC (premature junctional contraction)

3. Ventricles → PVC (premature ventricular contraction)

What are 5 patterns of premature complexes?

1. Pair/Couplet: 2 premature beats in a row

2. Run/Burst: ≥3 premature beats in a row

3. Bigeminy: every 2nd beat is premature → normal, premature, normal, premature

4. Trigeminy: every 3rd beat is premature → 2 normal, 1 premature

5. Quadrigeminy: every 4th beat is premature → 3 normal, 1 premature

What ECG changes occur with hyperkalemia, and what are 4 priority nursing interventions?

Hyperkalemia: K⁺ >5 mEq/L; critical >6.5 or ECG changes

ECG Progression

• Tall, peaked T waves → widened QRS → wave pattern → VF

Interventions

1. Continuous cardiac monitoring

2. Dextrose, insulin, calcium gluconate, kayexalate

3. Sodium bicarbonate

4. Dialysis

What 4 ECG changes occur with hypokalemia, and what are 3 priority nursing interventions?

Hypokalemia: K⁺ <3.55 mEq/L; critical <2.5 mEq/L or symptomatic

ECG Changes

1. Prominent U waves after T wave

2. Flattened/inverted T waves

3. Prolonged QU interval

4. → PVCs and torsades risk

Interventions

1. Replace K⁺ PO/IV

2. Continuous cardiac monitoring

3. Replace Mg²⁺ simultaneously when indicated

What 2 ECG changes occur with hypercalcemia, and what are 4 priority nursing interventions?

Hypercalcemia: Ca²⁺ >10.5 mg/dL; Critical >12mg/dL

ECG changes:

1. Shortened QT interval

2. Shortened ST segment

Interventions

1. Aggressive IV fluids

2. Furosemide

3. Bisphosphonates

4. Calcitonin

What 3 ECG changes occur with hypocalcemia, and what are 3 priority nursing interventions?

Hypocalcemia: Ca²⁺ <8.5 mg/dL; Critical: Ca²⁺ <7 mg/dL or symptomatic

ECG changes:

1. Prolonged QT

2. T-wave inversion

3. ↑ risk for Torsades

Interventions:

1. IV calcium gluconate

2. Oral calcium supplementation when appropriate

3. Treat underlying cause

What 2 ECG changes occur with hypomagnesmia, and what are 3 priority nursing interventions?

Hypomagnesemia: Mg²⁺ <1.5 mEq/L; Critical: Mg²⁺ <1.2 mEq/L or symptomatic

ECG changes:

1. Prolonged PR, QRS, QT

2. → PVCs, Torsades, VF risk

Interventions:

1. IV MgSO₄

2. Correct Mg²⁺ and K⁺ together

3. Consider renal function when replacing Mg²⁺