SYNTHESIS/CRITICAL CARE NURSING EXAM #2
CHAPTER 7: DYSTHYMIAS
Sinus Rhythm
• Represents normal electrical conduction from the SA node through the atria and
ventricles
• Rate: atrial and ventricular rates are equal, typically 60–100 bpm
• Rhythm: regular or essentially regular
• Intervals: PR interval 0.12–0.20 sec; QRS 0.06–0.10 sec
• Waveform characteristics: consistent P waves and QRS complexes
o P waves are rounded and uniform
o Each P wave is followed by a QRS complex and T wave
• Clinical status: patient is generally hemodynamically stable
Sinus Bradycardia
• Heart rate is below 60 bpm for both atrial and ventricular activity
• May be normal in some individuals or cause instability depending on cardiac output
• Rhythm: regular or nearly regular
• Intervals: generally normal; QT interval may be prolonged
• Waveforms: normal-appearing P and QRS complexes
• Clinical effects: may be asymptomatic or cause poor perfusion (hypotension, dizziness,
syncope, SOB, diaphoresis, decreased organ perfusion)
Causes:
• Vagal stimulation (vomiting, gagging, straining)
• Medications (digoxin toxicity, calcium channel blockers, beta blockers)
• High athletic conditioning
• Physiologic response to MI, hypothyroidism, increased ICP, or hypothermia
Treatment:
• Assess perfusion status and symptoms
o If stable: monitor only
o If symptomatic with poor perfusion:
▪ Atropine 0.5–1 mg IV every 3–5 minutes (max 3 mg; ACLS often uses
1 mg doses)
▪ Avoid atropine in hypothermia and AV blocks (may worsen condition)
• If ineffective:
o Transcutaneous pacing
o Dopamine infusion (2–20 mcg/kg/min)
o Epinephrine infusion (2–10 mcg/min, titrated)
Sinus Tachycardia
• Heart rate exceeds 100 bpm, usually 100–160 bpm (can reach 180 bpm)
• Often a normal sympathetic response
• Common in children under 6
• Rhythm: regular with gradual onset
, • Intervals: PR 0.12–0.20 sec; QT may shorten; P waves may be harder to see at high rates
• Waveforms: normal P before each QRS, consistent morphology
Clinical effects:
• Reduced cardiac output due to shortened ventricular filling time
• Especially harmful in patients with coronary artery disease due to reduced diastolic
coronary perfusion
Causes:
• Fever, pain, anxiety, exercise
• Hypovolemia, anemia, heart failure
• Hyperthyroidism
• Stimulant use or sympathetic activation
Treatment:
• Underlying cause is treated rather than the rhythm itself
o Example: antipyretics for fever, analgesics for pain
• Beta blockers or calcium channel blockers may be used in some cases to slow rate
Sinus Arrhythmia
• Common normal variation, especially in children and young adults
• Heart rate fluctuates with respiration:
o Increases during inspiration
o Decreases during expiration
• Rhythm: cyclically irregular but predictable
• Rate: 60–100 bpm
• Waveforms: normal P and QRS complexes
Clinical significance:
• Usually indicates healthy autonomic regulation
• No treatment required
First-Degree AV Block
• Delayed conduction through AV node or atrial pathways
• Seen as prolonged PR interval on ECG
• Common in older adults or cardiac disease
• Rate: depends on underlying rhythm
• Rhythm: regular based on underlying rhythm
• PR interval: >0.20 sec consistently
• QRS: normal duration
• Waveforms: normal P before each QRS
Clinical significance:
• Typically well tolerated
, • No specific treatment required
• Associated with ischemic, valvular, or age-related conduction changes
Atrial Fibrillation
• Most common clinical dysrhythmia
• Caused by multiple ectopic atrial foci leading to chaotic atrial activity
• AV node receives rapid, disorganized impulses
• Atrial rate: may exceed 700 bpm (not measurable)
• Ventricular response: irregularly irregular
• Rhythm: completely irregular
• PR interval: absent
• Waveforms: no distinct P waves; fibrillatory baseline present
Clinical presentation:
• May be asymptomatic or cause decreased cardiac output
• Rapid ventricular response worsens symptoms
Causes:
• Heart failure, ischemic disease, valvular disorders
• Hyperthyroidism, lung disease, aging
Treatment:
• Anticoagulation to prevent thromboembolism
• Rate control (beta blockers, calcium channel blockers, digoxin)
• Cardioversion after anticoagulation when appropriate
• Ablation may be considered
• Emergency cardioversion if unstable
Complications:
• High risk of clot formation → stroke or pulmonary embolism
• Loss of atrial kick reduces cardiac output
• Monitor for stroke symptoms (FAST: face, arms, speech, time)
Atrial Flutter
• Caused by a single irritable atrial focus
• Atrial rate: 240–320 bpm (often ~300)
• Characteristic sawtooth flutter waves
• Rhythm: atrial regular; ventricular rhythm may vary
• Conduction ratios (e.g., 2:1, 3:1) determine ventricular rate
• No PR interval
• QRS usually normal unless conduction abnormality
, Clinical presentation:
• Often asymptomatic unless rapid ventricular response develops
Causes:
• COPD, ischemic heart disease, hyperthyroidism
• Alcohol use, hypoxemia, heart failure
Treatment:
• Anticoagulation if indicated
• Rate control (beta blockers, calcium channel blockers, digoxin, amiodarone)
• Elective cardioversion after anticoagulation period
Asystole
• Complete absence of electrical cardiac activity
• Flatline ECG without P, QRS, or T waves
• No pulse or cardiac output → cardiac arrest
• Must confirm in multiple leads to rule out artifact or equipment failure
Causes (5 H’s and 5 T’s):
• Hypovolemia, hypoxia, acidosis, potassium imbalance, hypothermia
• Toxins, tamponade, tension pneumothorax, thrombosis (coronary or pulmonary),
trauma
Treatment:
• Immediate CPR (BLS/ACLS)
• Epinephrine 1 mg IV/IO every 3–5 minutes
• Airway management and rhythm reassessment every 2 minutes
Pulseless Electrical Activity (PEA)
• Organized electrical rhythm present but no mechanical pulse
• No consistent ECG pattern
Key point:
• Electrical activity exists, but cardiac output is insufficient
Treatment:
• Identify and treat underlying cause
• CPR and ACLS protocol
• Epinephrine administration
• Airway management and continuous resuscitation
Ventricular Tachycardia (With or Without Pulse)
• Life-threatening ventricular rhythm originating from ectopic focus
CHAPTER 7: DYSTHYMIAS
Sinus Rhythm
• Represents normal electrical conduction from the SA node through the atria and
ventricles
• Rate: atrial and ventricular rates are equal, typically 60–100 bpm
• Rhythm: regular or essentially regular
• Intervals: PR interval 0.12–0.20 sec; QRS 0.06–0.10 sec
• Waveform characteristics: consistent P waves and QRS complexes
o P waves are rounded and uniform
o Each P wave is followed by a QRS complex and T wave
• Clinical status: patient is generally hemodynamically stable
Sinus Bradycardia
• Heart rate is below 60 bpm for both atrial and ventricular activity
• May be normal in some individuals or cause instability depending on cardiac output
• Rhythm: regular or nearly regular
• Intervals: generally normal; QT interval may be prolonged
• Waveforms: normal-appearing P and QRS complexes
• Clinical effects: may be asymptomatic or cause poor perfusion (hypotension, dizziness,
syncope, SOB, diaphoresis, decreased organ perfusion)
Causes:
• Vagal stimulation (vomiting, gagging, straining)
• Medications (digoxin toxicity, calcium channel blockers, beta blockers)
• High athletic conditioning
• Physiologic response to MI, hypothyroidism, increased ICP, or hypothermia
Treatment:
• Assess perfusion status and symptoms
o If stable: monitor only
o If symptomatic with poor perfusion:
▪ Atropine 0.5–1 mg IV every 3–5 minutes (max 3 mg; ACLS often uses
1 mg doses)
▪ Avoid atropine in hypothermia and AV blocks (may worsen condition)
• If ineffective:
o Transcutaneous pacing
o Dopamine infusion (2–20 mcg/kg/min)
o Epinephrine infusion (2–10 mcg/min, titrated)
Sinus Tachycardia
• Heart rate exceeds 100 bpm, usually 100–160 bpm (can reach 180 bpm)
• Often a normal sympathetic response
• Common in children under 6
• Rhythm: regular with gradual onset
, • Intervals: PR 0.12–0.20 sec; QT may shorten; P waves may be harder to see at high rates
• Waveforms: normal P before each QRS, consistent morphology
Clinical effects:
• Reduced cardiac output due to shortened ventricular filling time
• Especially harmful in patients with coronary artery disease due to reduced diastolic
coronary perfusion
Causes:
• Fever, pain, anxiety, exercise
• Hypovolemia, anemia, heart failure
• Hyperthyroidism
• Stimulant use or sympathetic activation
Treatment:
• Underlying cause is treated rather than the rhythm itself
o Example: antipyretics for fever, analgesics for pain
• Beta blockers or calcium channel blockers may be used in some cases to slow rate
Sinus Arrhythmia
• Common normal variation, especially in children and young adults
• Heart rate fluctuates with respiration:
o Increases during inspiration
o Decreases during expiration
• Rhythm: cyclically irregular but predictable
• Rate: 60–100 bpm
• Waveforms: normal P and QRS complexes
Clinical significance:
• Usually indicates healthy autonomic regulation
• No treatment required
First-Degree AV Block
• Delayed conduction through AV node or atrial pathways
• Seen as prolonged PR interval on ECG
• Common in older adults or cardiac disease
• Rate: depends on underlying rhythm
• Rhythm: regular based on underlying rhythm
• PR interval: >0.20 sec consistently
• QRS: normal duration
• Waveforms: normal P before each QRS
Clinical significance:
• Typically well tolerated
, • No specific treatment required
• Associated with ischemic, valvular, or age-related conduction changes
Atrial Fibrillation
• Most common clinical dysrhythmia
• Caused by multiple ectopic atrial foci leading to chaotic atrial activity
• AV node receives rapid, disorganized impulses
• Atrial rate: may exceed 700 bpm (not measurable)
• Ventricular response: irregularly irregular
• Rhythm: completely irregular
• PR interval: absent
• Waveforms: no distinct P waves; fibrillatory baseline present
Clinical presentation:
• May be asymptomatic or cause decreased cardiac output
• Rapid ventricular response worsens symptoms
Causes:
• Heart failure, ischemic disease, valvular disorders
• Hyperthyroidism, lung disease, aging
Treatment:
• Anticoagulation to prevent thromboembolism
• Rate control (beta blockers, calcium channel blockers, digoxin)
• Cardioversion after anticoagulation when appropriate
• Ablation may be considered
• Emergency cardioversion if unstable
Complications:
• High risk of clot formation → stroke or pulmonary embolism
• Loss of atrial kick reduces cardiac output
• Monitor for stroke symptoms (FAST: face, arms, speech, time)
Atrial Flutter
• Caused by a single irritable atrial focus
• Atrial rate: 240–320 bpm (often ~300)
• Characteristic sawtooth flutter waves
• Rhythm: atrial regular; ventricular rhythm may vary
• Conduction ratios (e.g., 2:1, 3:1) determine ventricular rate
• No PR interval
• QRS usually normal unless conduction abnormality
, Clinical presentation:
• Often asymptomatic unless rapid ventricular response develops
Causes:
• COPD, ischemic heart disease, hyperthyroidism
• Alcohol use, hypoxemia, heart failure
Treatment:
• Anticoagulation if indicated
• Rate control (beta blockers, calcium channel blockers, digoxin, amiodarone)
• Elective cardioversion after anticoagulation period
Asystole
• Complete absence of electrical cardiac activity
• Flatline ECG without P, QRS, or T waves
• No pulse or cardiac output → cardiac arrest
• Must confirm in multiple leads to rule out artifact or equipment failure
Causes (5 H’s and 5 T’s):
• Hypovolemia, hypoxia, acidosis, potassium imbalance, hypothermia
• Toxins, tamponade, tension pneumothorax, thrombosis (coronary or pulmonary),
trauma
Treatment:
• Immediate CPR (BLS/ACLS)
• Epinephrine 1 mg IV/IO every 3–5 minutes
• Airway management and rhythm reassessment every 2 minutes
Pulseless Electrical Activity (PEA)
• Organized electrical rhythm present but no mechanical pulse
• No consistent ECG pattern
Key point:
• Electrical activity exists, but cardiac output is insufficient
Treatment:
• Identify and treat underlying cause
• CPR and ACLS protocol
• Epinephrine administration
• Airway management and continuous resuscitation
Ventricular Tachycardia (With or Without Pulse)
• Life-threatening ventricular rhythm originating from ectopic focus
