NORMAL SINUS RHYTHM
Definition Reflects normal conduction of the sinus impulse through the atria and ventricles
Rate Atrial and ventricular rates are the same and range from 60–100 bpm
Rhythm Rhythm is regular or essentially regular
P Wave Normal
PR Interval Normal
QRS Complex Normal
QT Interval Normal
T Wave Normal
Conduction Normal
Causes Occurs in healthy cardiac systems
Symptoms
No symptoms; patient is hemodynamically stable
Medication None required
Treatment None required
Distinguishing N/A
feature
SINUS TACHYCARDIA
Definition Sinus tachycardia results when the SA node fires faster than 100 bpm. It is a normal
response to stimulation of the sympathetic nervous system
Rate Both atrial and ventricular rate >100 bpm, my even be as fast as 180 bpm
Rhythm Gradual onset; Regular or essentially regular
P Wave Normal; may be hidden in T wave is rate is too fast
PR Interval Normal
QRS Complex Normal
QT Interval May shorten
T Wave Normal; may overcome the P waves in rapid rates
Conduction Normal
Causes Hyperthyroidism, hypovolemia, HF, anemia, exercise, use of stimulants, fever,
sympathetic response to fear/pain, anxiety, inotropic meds, caffeine
Symptoms HR may CO d/t shorter filling times for the ventricles
Medication None specifically (antipyretics if caused by fever, pain medication if caused by pain)
Treatment Tx depends on context (Sinus tachy may be a normal response). Treat underlying
cause (ceasing/starting medication, replacing blood or fluids, etc.)
Distinguishing This is a normal fast rate. P’s may not be present and that’s ok, they may just be
feature hiding within a T wave
SINUS BRADYCARDIA
Definition Sinus bradycardia may be normal for athletes or may occur during sleep. Although
this may be asymptomatic, it may cause instability. Assess for instability in pt
Rate Both atrial and ventricular rates <60 bpm
Rhythm Regular or essentially regular
P Wave Normal
PR Interval Normal
QRS Complex Normal
QT Interval Might be prolonged
T Wave Normal
Conduction Decreased in SA node (looks like NSR but at a slower rate)
Causes [Normal in athletes and during sleep]  ICP, hypoxia, hypothermia, heart disease,
excessive inhibitory vagal (vomiting, BM), drug induced (digoxin, Inderal), Ca
channel blockers, Beta Blockers
Symptoms A slowed heart rhythm may cause a decrease in CO, resulting in hypotension and
decreased organ perfusion; changes in LOC, chest discomfort, SOB/resp. distress,
pulmonary congestion/crackles, rapid/slow/weak pulse, dizziness, syncope, fatigue,
restlessness
Medication Atropine (IVP, most common drug for low HR, one-time dose); Isuprel (IV drip, cont.
infusion, not a permanent fix)
Treatment None if mild; observation; pacing/pacemaker
Distinguishing A normal slow
feature
SINUS ARRYTHMIA
Definition A cyclical change in heart rate that s associated with respiration. HR increases with
inspiration, slows with expiration d/t changes in vagal tone.
Rate Atrial and ventricular rates between 60–100 bpm
Rhythm Regularly irregular; pattern of increasing and decreasing
P Wave Normal
PR Interval Normal
QRS Complex Normal
QT Interval Normal
T Wave Normal
Conduction Normal
Causes Usually associated with respirations
Symptoms This rhythm is tolerated well
Medication None necessary
Treatment None necessary
Distinguishing Alternating patterns of slow and fast HR (within the 60-100 range)
feature
PREMATURE ATRIAL CONTRACTIONS (PAC)
Definition A single ectopic beat arising from atrial tissue, not the SA node. The PAC occurs
earlier than the next normal beat and interrupts the regularity of the underlying
rhythm. PACs are common, but denote an irritable area in the atria that has
developed the property of automaticity
Rate The rate matches that of the underlying rhythm (usually within normal range)
Rhythm Irregular d/t early beat; usually the pause is noncompensatory (doesn’t resume
original rhythm after the funny little beat)
P Wave Usually different than normal because it arises from a different area of the atria; It
may follow or be in the T wave
PR Interval Usually shorter
QRS Complex Normal or wide; a non-conducted P wave may not be followed by a QRS (the
ventricles may not have been able to full repolarize before the ectopic beat occurred,
therefore not firing and producing a QRS complex)
QT Interval Normal, unless the T wave has been affected by a premature P wave
T Wave Usually normal unless the P wave occurs within the T wave, then the T wave will
present abnormal
Conduction Originates from a different location other than the SA node; a different area in the
atria has been irritated and is producing automaticity
Causes HF, anxiety, caffeine, nicotine, tobacco, enlarged atria, electrolyte imbalances,
digoxin, Low K or Mg myocardial hypertrophy/dilation, ischemia, lung disease, may
be a normal variant
Symptoms Usually well tolerated, though the pt may complain of palpitations
Medication None necessary
Treatment Not usually necessary; increasing numbers of PACs (Paroxysmal Atrial Tachycardia:
3+ PACs in a row, a run; pt bursts in and out of this) can evolve into A fib or A flutter
– observe and assess
Distinguishing The beat comes in earlier, and the rhythm comes back noncompensated
feature
ATRIAL FLUTTER
Definition Arises from a single irritable focus in the atria; extremely fast
Rate Atrial rate is between 240-320 bpm, typically 300 bpm; Ventricular rate is
determined by the conduction ratio of the flutter waves, usually 150 bpm
Rhythm Atrial rhythm regular, ventricular may or may not be
P Wave Flutter waves, sawtooth; rapid fire, usually a pattern of P waves to QRS 2:1, 3:1, 4:1,
5:1
PR Interval No PR interval present
QRS Complex May not be regular (depends on if any conduction comes thru the AV node from the
P wave)
QT Interval Normal, unless distorted by a flutter wave
T Wave May not be regular (depends on if any conduction comes thru the AV node from the
P wave)
Conduction Possible rapid-fire ectopic focus (hijacks electrical activity of heart)
Causes Lung disease, ischemic heart disease, hyperthyroidism, hypoxemia, HF, alcoholism,
digoxin toxicity, SA or atrial damage
Symptoms Atrial quivering: doesn’t fill properly, 25% decrease in CO and loss of atrial kick; pt is
usually asymptomatic
Medication Anticoagulant therapy (quivering doesn’t push all blood out of atrium, blood pools
and can clot); beta blockers (slows/controls HR); digoxin; Ca channel blockers
Treatment Cardioversion, ablation
Distinguishing Sawtooth pattern
feature
ATRIAL FIBRILLATION
Definition The most common dysrhythmia. Atrial fibrillation arises from multiple ectopic foci in
the atria, causing chaotic quivering of the atria and ineffectual atrial contraction. AV
node is bombarded with hundreds of atrial impulses and conducts these impulses in
an unpredictable manner to the ventricles. When A fib occurs sporadically, it is
called Paroxysmal Atrial Fibrillation
Rate If the rate is normal it is called “controlled A fib,” Otherwise, 150-300 bpm. Atrial
rate may be as high as 700 bpm
Rhythm Totally irregular (irregularly irregular)
P Wave Wavy isoelectric line, no discernable P waves
PR Interval None
QRS Complex Normal; wide if a bundle branch block exists
QT Interval Normal; wide if a bundle branch block exists
T Wave Should be present, visible in a different lead perspective
Conduction Chaotic conduction. AV node conducts hundred of impulses sporadically
Causes Ischemic heart disease, valvular heart disease, hyperthyroidism, lung disease, heart
failure, aging, stress, alcohol, caffeine, COPD
Symptoms Poor ventricular filling d/t loss of atrial kick, stable or decreased CO, possible
dizziness, clots may form in atria, Pt may or may not be aware of A fib., worsening of
heart failure symptoms
Medication Anticoagulants, amiodarone, digoxin, Inderal, verapamil, beta blockers,
antithrombotic
Treatment Cardioversion, ablation
Distinguishing Isoelectric line with QRS/T present
feature
JUNCTIONAL RHYTHMS (ESCAPE, ACCELERATED, & TACHY)
Definition Junctional rhythms are dysrhythmias of the AV node d/t disease or impairment of
the SA node.
Rate Junctional escape rhythm: 40-60 bpm; Accelerated Junctional: 60-100 bpm;
Junctional Tachycardia: >100 bpm
Rhythm Regular
P Wave P wave will be inverted (before the QRS), absent (hidden in the QRS), or late and
inverted (after the QRS)
PR Interval < 0.12 sec. if present
QRS Complex Usually normal
QT Interval Normal
T Wave Normal
Conduction The SA node may be impaired, so the impulse originates from the AV node. This
impulse may jump back into the atria
Causes The escape rhythm may be caused by loss of SA node activity. Accelerated/Tachy
may be caused by sinoatrial node disease, ischemic heart disease, electrolyte
imbalances, digitalis toxicity, hypoxemia
Symptoms Escape: when it’s bradycardia, not dangerous on its own. Assess pt tolerance.
Accelerate/Tachy: Pt my have decreased CO and hemodynamic instability,
depending on the rate
Medication Escape: if symptomatic, give atropine, dopamine, epinephrine infusions
Treatment Escape: transcutaneous pacing
Accelerate/Tachy: assess and treat the tachycardia if the pt is hemodynamically
unstable
Distinguishing Inverted or absent P waves
feature
PREMATURE JUNCTIONAL CONTRACTIONS (PJC)
Definition Irritable areas in the AV node and junctional tissue can generate premature beats
that are earlier than the next expected beat. Like PACs but with characteristics of a
junctional beat
Rate The rate is that of the underlying rhythm
Rhythm Premature beat, interruption of rhythm (may or may not be compensatory)
P Wave May be before/inverted, within, or after QRS
PR Interval Short on the PJC beat
QRS Complex Normal
QT Interval Normal
T Wave Normal; followed very closely by the PJC beat
Conduction AV node usurps and gains control of conduction
Causes May be a normal variant, increased vagal tone, digitalis toxicity, HF, edema, ischemic
or valvular heart disease, response to endogenous or exogenous catecholamines,
such as epinephrine
Symptoms This rhythm is well tolerated, but the patient may experience palpitations if the PJCs
occur frequently
Medication Quinidine, hold Dig
Treatment Stop stimulants; No treatment usually necessary
Distinguishing Like a PAC, except the P is inverted
feature
PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA (SVT)
Definition Occurs above the ventricles and it has an abrupt onset and cessation. It is initiated by
either a PAC or a PJC. An abnormal conduction pathway around the AV node or an
accessory pathway around the AV node results in extreme tachycardia. Paroxysmal:
abrupt onset and end
Rate HR is 150-250 bpm
Rhythm Regular
P Wave Absent, cannot be visualized. If present, it shortens the PR interval
PR Interval If P wave present, the PR interval is shortened
QRS Complex Narrow, normal
QT Interval Normal
T Wave Normal
Conduction Above the ventricles
Causes Catecholamines, heart disease, stimulants, anatomic abnormalities, electrolyte
imbalance, congenital. Can occur in healthy, young adult w/o structural heart disease
Symptoms Patient may be asymptomatic or symptomatic, dizzy, hypotensive
Medication Adenosine (IVP, rapid action)
Treatment Vagal maneuvers (causes decrease in HR), cardioversion
Distinguishing Rapid pace, absent P
feature
PREMATURE VENTRICULAR CONTRACTIONS (PVC)
Definition A common ventricular dysrhythmia. PVCs are early beats that interrupt the
underlying rhythm. Originating from one focus: identical PVCs. Originating from
multiple foci: unidentical PVCs. Bigeminy: every other beat. Unifocal: just one beat.
Couplets/Pair: two paired together. Runs: grouping of a few (6+ can cause VTach).
Fused: simultaneous with a normal beat. Multifocal: frequent, rare, occasional. R on
T phenomenon: when the R wave of PVC falls on the T wave of a normal beat
Rate Not significant, doesn’t matter. The underlying rhythm doesn’t change
Rhythm PVC is a premature beat; The PVC doesn’t interrupt the underlying rhythm
(compensatory rhythm).
P Wave Usually not identified. May be buried in the QRs or the T
PR Interval None
QRS Complex Longer than 0.12 seconds. The QRS complex of the PVC is wide and bizarre
QT Interval May be distorted or unidentified if warped by the PVC. Would be normal in the other
normal beats
T Wave T wave may be oriented opposite direction of the QRS. If a PVC occurs during a T
wave, VTach may occur. The peak of the T wave through the downslope of the T
wave is considered the vulnerable period, which coincides with partial
repolarization of the ventricles
Conduction Impulse arises from a single ectopic foci or multiple foci within the ventricles
Causes HF, MI, increased catecholamine, stimulants, hypoxia, excessive digoxin, decreased K
or MG (electrolyte imbalances), acid base imbalance, ischemic heart disease
Symptoms Occasional or rare, usually well tolerated in patients. PVCs may be experienced as
palpitations, pt may become symptomatic if the PVCs occur frequently. Can be a
precursor of VTach and no CO. Risking R on T. Lightheadedness
Medication Beat blockers, Ca channel blockers, antiarrhythmics (amiodarone, flecainide)
Treatment Chart how often PVCs are seen (frequent, rare, occasional). Treat underlying cause if
increasing in frequency
Distinguishing Compensatory (the PVC doesn’t interrupt the underlying rhythm). Wide, bizarre QRS
feature complex.
VENTRICULAR TACHYCARDIA
Definition A rapid, life-threatening dysrhythmia originating from a single ectopic focus in the
ventricles. Characterized by three PVCs in a row
Rate > 100 bpm. Usually 150 bpm up to 250 bpm. >250 can be fatal d/t decreased
perfusion of the brain. Pt may or may not have a pulse
Rhythm The rhythm is regular unless capture beats occur and momentarily interrupt the VT
P Wave May be absent b/c the wave of depolarization associated with VT rarely reaches the
atria. If present, P waves have no association with QRS. P waves may be firing at a
normal rate and show up randomly throughout the strip (AV dissociation). A P wave
could “capture” the ventricle b/c of the timing of atrial depolarization, interrupting
VT with a single beat, producing an apparently normal QRS; then VT recurs. This
helps differentiate VT from wide complex tachycardias
PR Interval None
QRS Complex Wide, bizarre d/t abnormal depolarization of the ventricles. Greater than 0.12 sec.,
wider than 0.16 sec.
QT Interval None
T Wave The polarity of the T wave is opposite to that seen in the QRS
Conduction Originates from a single ectopic focus in the ventricles
Causes CAD, MI, Digoxin toxicity, HF, electrolyte disturbances (low K is very significant),
increased ICP, meth/cocaine, ischemia, chronic sleep apnea, genetic abnormalities,
QT prolongation
Symptoms Life threatening!! Decreased/no perfusion. If there is enough CO, HR/BP may be
present. If CO is impaired, the pt has s/s of low CO and low perfusion. Possible
cardiac arrest. Eyes rolling back, no BP, no HR, vomiting possible
Medication If pulse is present and BP is stable, treat w/ drugs. IV amiodarone or lidocaine.
Mexiletine, sotalol. Drug cardioversion: decreases HR
Treatment No pulse: call code, BLS, defibrillate (defib fast and early for best results).
Electrocardioversion (delivered on R wave, T wave is avoided)
Distinguishing Wide ups and downs. Rapid rate, poor pt tolerance, life threatening!
feature
VENTRICULAR FIBRILLATION
Definition A chaotic rhythm characterized by a quivering of the ventricles, which results in total
loss of cardiac output and pulse. Wavy baseline with no PQRST complex. V Fib may
be coarse or fine
Rate May not be discernable. Could be 300-600 bpm
Rhythm Rapid irregular succession of chaotic, bizarre waves, oscillation of baseline
P Wave None identifiable
PR Interval None identifiable
QRS Complex None identifiable
QT Interval None identifiable
T Wave None identifiable
Conduction Uncoordinated muscle fiber contractions. Quivering of ventricles
Causes Ischemic and valvular heart disease, electrolyte or acid-base imbalances, QT
prolongation, excessive medications (quinidine, procainamide, digoxin),
electrocution
Symptoms Life-threatening!! This pt is in cardiac arrest. Absent CO, fatal if not corrected within
minutes
Medication Drugs used during a code (epi, etc.). Meds are taken to decrease future episodes
Treatment The more immediate the treatment, the better the odds are for survival. Must assess
pt and leads first, as this rhythm may be caused by loose leads or electrical
interference. Call code, BLS, defibrillation. May implant ICD (implanted cardioverter
defibrillator)
Distinguishing Complete chaos, no distinguishable PQRST complex, life threatening!!
feature
IDIOVENTRICULAR (ESCAPE) RHYTHM
Definition An escape rhythm that is produced by the Purkinje fibers. Emerges only when SA
and AV nodes fail to initiate an impulse. Because this last pacemaker cell is in the
ventricles, the QRS complex appears wide and bizarre with a slow rate. Considered a
lethal dysrhythmia b/c if the Purkinje cease firing, the pt will go into asystole.
Accelerated Idioventricular Rhythm (AIVR): 40-100 bpm; may be seen after
reperfusion of a coronary artery by thrombolytics, after angiography, stent
placement, or cardiac surgery
Rate 20-40 bpm; 40-100 bpm is accelerated idioventricular rhythm
Rhythm Atrial: non or irregular. Ventricle: regular
P Wave Usually not present. If present, normal, irregular, or abnormal
PR Interval None
QRS Complex Wide and bizarre
QT Interval None
T Wave Follows QRS and shows opposite polarity
Conduction Rhythm by default, slow inherent rate of the ventricles. Still base electrical activity
but no emptying or filling is happening
Causes Failure of the SA/AV nodes, common with MI, heart disease, drug induced
(narcotics)
Symptoms May have enough rate to maintain perfusion, may progressively worsen. The
extreme bradycardia may cause the same s/s as any severe bradycardia. Asystole
may occur
Medication Atropine, Isuprel
Treatment Treat underlying cause, pacing (but pacing only works if there is something to pace –
can’t pace dead heart tissue), BLS/ACLS
Distinguishing Extremely slow rate, wide QRS
feature
VENTRICULAR ASYSTOLE (STANDSTILL)
Definition Characterized by complete cessation of electrical activity. A flat baseline is seen,
without evidence of PQRST complex. Absent pulse, no CO, cardiac arrest has
occurred. Occurs following VF. If following Ventricular Escape Rhythm (VER), the
asystole is referred to as ventricular standstill
Rate None
Rhythm None
P Wave None
PR Interval None
QRS Complex None
QT Interval None
T Wave None
Conduction Cessation of electrical activity
Causes Lead displacement, electrode coming off (assess pulse)
Symptoms Patient is in cardiac arrest. Severe MI, dying heart, severe hypoxia, drug overdose,
hyperkalemia, acidosis (always check electrolytes), VF, VER
Medication Epinephrine bolus, Vasopressin
Treatment ACLS/BLS, call code, CPR
Distinguishing Flat line
feature
FIRST DEGREE AV BLOCK
Definition Consistent delayed conduction through the AV node or the atrial conductive tissue.
Represented on the ECG as a prolonged QT interval. Common in older adults and in
cardiac patients.
Rate Normal
Rhythm Regular
P Wave Normal
PR Interval Prolonged PR interval is the key feature of 1st degree AV block
QRS Complex Normal
QT Interval Normal
T Wave Normal
Conduction Conduction is delayed at the AV node. An impulse from the SA node has trouble
passing through the AV node and to the rest of the ventricles.
Causes MI of the inferior wall; dig toxicity. Aging and ischemic and valvular heart disease
can cause AV block
Symptoms This block is well tolerated. No s/s but can progress to type II or III. Adequate
perfusion still exists
Medication None required
Treatment None required. Possible to treat underlying cause (monitor electrolyte imbalances,
medicinal causes, etc.). Observe for possible progression
Distinguishing “If the R is far from P, then you have a first degree”
feature
SECOND DEGREE AV BLOCK TYPE I (MOBITZ I/WENCKEBACH)
Definition Mobitz I is a progressive lengthening of the PR Interval until there is a P wave
without a QRS. The AV node progressively delays conduction to the ventricles
resulting in progressively longer PR intervals until the QRS complex is finally
dropped. The PR interval following the dropped QRS is shorter and returns to the
original rhythm. The AV node can recover and conduct the next atrial impulse. If the
dropped beat occurs frequently, describe the conduction ratio (2:1, 3:1, 4:1, etc.)
Rate Atria: normal. Ventricle: depends on the AV node and what is able to come through
the AV node
Rhythm Atria: normal. Ventricle: usually irregular
P Wave More frequent than QRS (because the SA node is fine and conducts a proper beat
through the atria)
PR Interval Progressive lengthening, then 1 P wave is blocked by the AV node, not allowed to
pass, and QRS does not occur
QRS Complex Normal when it does appear. The QRS wave will be normal on the complexes that are
produced. One will not appear before a P wave where the impulse was blocked
QT Interval Normal when they do appear
T Wave Normal when it does appear
Conduction Defective conduction of an impulse in the AV node
Causes Aging, AV nodal blocking drugs, acute inferior MI or right ventricular infarction,
ischemic heart disease, digitalis toxicity, excess vagal response
Symptoms Usually well tolerated, unless there is underlying bradycardia, or frequently dropped
beats. Can progress to higher AV block.
Medication None required
Treatment No treatment necessarily needed, unless the dropped beats occur very frequently.
Treat possible underlying cause. Stop possible contributing medications. Rarely are
permanent pacemakers called for
Distinguishing “Longer, longer, longer, drop! Then you have a Wenkebach”
feature
SECOND DEGREE AV BLOCK TYPE II (MOBITZ II)
Definition Mobitz II is a more critical type of second-degree heart block that requires early
recognition and intervention. This block is often associate w/ with a bundle branch
block and a corresponding widened QRS complex; however, QRS complexes can be
narrow. This block can progress to the more clinically significant third block and
may cause symptomatology
Rate HR is slower than the underlying rhythm because of the dropped beats. Ventricular
rate less than atrial and is irregular
Rhythm Atrial: regular. Ventricular: no regularity, sudden drop of complexes
P Wave More numerous than QRS. May not always have an accompanying QRS
PR Interval Normal or prolonged, but remains consistent until suddenly one or more wave may
occur w/o a QRS
QRS Complex Normal or wide. May be missing
QT Interval Normal
T Wave Normal
Conduction The conduction abnormality usually occurs below the AV node, either in the Bundle
of His
Causes Bundle branch damage, anterior wall MI, heart disease, increased vagal tone,
conduction system diseases, ablation of the AV node, inferior and right ventricular
infarctions
Symptoms Like bradycardia. The pt may tolerate one missed beat, but symptoms may occur if
more than one beat is missed
Medication Atropine, Isuprel
Treatment Pacemaker. Transcutaneous or transvenous pacing for emergent treatment
Distinguishing “If some P’s don’t get through (to the ventricles), then you have a Mobitz II)”
feature Every QRS has a P, not every P has a QRS
THIRD DEGREE AV BLOCK
Definition Often called complete heart block b/c no atrial pulses are conducted through the AV
node to the ventricles. The atria and ventricles are beating independently of each
other because the AV node is completely blocked. The sinus impulse is blocked, and
the ventricles receive no impulse. No communication between the atria and ventricle
Rate The atria and ventricles beat at different rates. Atria: sinus rhythm. Ventricle: escape
rhythm. Atrial rate will be faster than the ventricular rate.
Rhythm Each may be regular. Both are firing at random rates. P-P intervals match, R-R
intervals match, but they aren’t associated with each other
P Wave Normal
PR Interval There will be no PR interval in the absence of conduction. If there is one, it happened
by chance
QRS Complex Often widened greater than 0.12 sec. with a ventricular escape rhythm
QT Interval Normal, if not interrupt by a P
T Wave Normal, if not interrupt by a P
Conduction The block of conduction can occur at the level of the AV node, bundle of His, or the
bundle branches
Causes Inferior wall MI, myocarditis, electrolyte imbalance, medication (Dig or Inderol
toxicity), ischemic heart disease, acute myocardial infarction, and conduction system
diseases
Symptoms Pt may become symptomatic b/c of the bradycardia of the escape rhythm. Syncope,
confusion, dyspnea, CP, risk of death
Medication Atropine, Isuprel
Treatment Temporary or permanent pacing, emergent action, identify underlying causes and
treat or eliminate it (meds, infection, etc.). May implant pacemaker if cause is
irreversible
Distinguishing “If P’s and Q’s don’t agree, then you have a third degree”
feature