Cardiac Rhythms Well Explained 100% Accuracy, 2024
Sinus bradycardia
Rate: <60 bpm, regularity: regular, P-wave: normal, QRS complex: narrow, PR interval:
0.12-0.20 sec. Common causes: Cardiomyopathy, inferior wall MI, SA node pathology,
vagal stimulation, hyperkalemia, hypothermia, increased ICP. Effects: Asymptomatic (if
patient able to compensate), hypotension and subsequent hypoperfusion (if patient
unable to compensate), pulmonary edema, acute kidney injury, altered mental status,
decreased level of consciousness, dizziness.
Sinus tachycardia
Rate: >100 bpm, regularity: regular, P-wave: normal, QRS complex: narrow, PR
interval: 0.12-0.20 sec. Common causes: Shock, heart failure, anemia, hypovolemia,
hyperthyroidism, respiratory failure, pulmonary embolism, infection and sepsis,
exercise, fever, stress, alcohol, stimulant recreational drugs (such as caffeine, cocaine,
methamphetamine). Effects: May be asymptomatic in early phases, hypertension (if
increased sympathetic input and ventricles have adequate filling time), hypotension with
associated tissue hypoperfusion (as heart rate increases, ventricle filling time
decreases), chest pain, blurred vision, syncope.
Junctional rhythm
Rate: 40-60 bpm, possibly faster, regularity: regular, P-wave: absent or inverted, QRS
complex: narrow, PR interval: <0.12 sec (if P wave present). Common causes:
Cardiomyopathy, beta-blockers, calcium channel blockers, electrolyte disturbances,
heart failure, hypoxia, vagal stimulation, SA node damage, ischemia, cardiac valve
disease. Effects: May be asymptomatic, possible slow pulse rate with associated
hypotension, hypoperfusion, blurred vision, pain, syncope.
Atrial fibrillation
Rate: atrial rate is indiscernible but may be >400 bpm. Ventricular rate is variable - may
be bradycardic or profoundly tachycardic, usually <150 bpm. Regularity: irregularly
irregular. P-wave: unclear, not discernible; may resemble multiple P-waves or no P-
Sinus bradycardia
Rate: <60 bpm, regularity: regular, P-wave: normal, QRS complex: narrow, PR interval:
0.12-0.20 sec. Common causes: Cardiomyopathy, inferior wall MI, SA node pathology,
vagal stimulation, hyperkalemia, hypothermia, increased ICP. Effects: Asymptomatic (if
patient able to compensate), hypotension and subsequent hypoperfusion (if patient
unable to compensate), pulmonary edema, acute kidney injury, altered mental status,
decreased level of consciousness, dizziness.
Sinus tachycardia
Rate: >100 bpm, regularity: regular, P-wave: normal, QRS complex: narrow, PR
interval: 0.12-0.20 sec. Common causes: Shock, heart failure, anemia, hypovolemia,
hyperthyroidism, respiratory failure, pulmonary embolism, infection and sepsis,
exercise, fever, stress, alcohol, stimulant recreational drugs (such as caffeine, cocaine,
methamphetamine). Effects: May be asymptomatic in early phases, hypertension (if
increased sympathetic input and ventricles have adequate filling time), hypotension with
associated tissue hypoperfusion (as heart rate increases, ventricle filling time
decreases), chest pain, blurred vision, syncope.
Junctional rhythm
Rate: 40-60 bpm, possibly faster, regularity: regular, P-wave: absent or inverted, QRS
complex: narrow, PR interval: <0.12 sec (if P wave present). Common causes:
Cardiomyopathy, beta-blockers, calcium channel blockers, electrolyte disturbances,
heart failure, hypoxia, vagal stimulation, SA node damage, ischemia, cardiac valve
disease. Effects: May be asymptomatic, possible slow pulse rate with associated
hypotension, hypoperfusion, blurred vision, pain, syncope.
Atrial fibrillation
Rate: atrial rate is indiscernible but may be >400 bpm. Ventricular rate is variable - may
be bradycardic or profoundly tachycardic, usually <150 bpm. Regularity: irregularly
irregular. P-wave: unclear, not discernible; may resemble multiple P-waves or no P-
