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22 PART I PATIENT EVALUATION
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82. What is visceral pain?
Visceral pain occurs when hollow abdominal organs such as the intestine or biliary tree contract
forcefullyorwhentheyaredistendedorstretched.Solidorganssuchasthelivercanbecomepainful when their capsules are stretched. Visceral pain may be difficult to localize and varies in quality.
It may be gnawing, burning, cramping, or aching.
83. What is parietal pain?
Parietal pain originates in the parietal peritoneum and is caused by inflammation. It is a steady ach-
ing pain that is usually more severe than visceral pain and more precisely localized over the involved
structure.
84. What is a positive Murphy’s sign?
Tenderness in palpating the right upper quadrant while the patient is deeply inspiring, which is a
sign of acute cholecystitis.
85. What are the indications for a definitive airway in a patient who has sustained
severe trauma?
Unconsciousness, maxillofacial injuries, aspiration risk, obstruction risk, apnea, poor respiratory
effort,closedheadinjury,andGCS<8.5.
86. What are the 5 P’s of compartment syndrome?
1. Pulselessness
2. Pallor
3. Poikilothermia
4. Pain
5. Paresthesia
87. What is the definition of anemia?
A hemoglobin concentration of less than 14 g/dL in males and 12.3 g/dL in females.
88. What factors influence the decision to transfuse a surgical patient?
1. Estimated blood loss of the procedure
2. Underlying risk factor for ischemic heart disease
89. Define each class of hemorrhage and describe symptoms associated with each
class.
• ClassIhemorrhage:Lessthan15%oftotalbloodvolumehasbeenlost.Therearenochangesin
blood pressure or heart rate. Typically, no treatment is indicated.
• ClassIIhemorrhage:Approximately15%to30%oftotalbloodvolumeislost.Typicalsigns
include tachypnea, tachycardia, and an increased diastolic blood pressure (narrowing of pulse
pressure). Urine output may be affected. Resuscitation with crystalloid fluids is recommended.
• ClassIIIhemorrhage:Approximately30%to40%oftotalbloodvolumeislost.Signicanttachy-
cardia and tachypnea is present. The patient is hypotensive and pulse pressure is decreased.
Hypoperfusion is evident including delayed capillary refill, decreased urine output, and changes in
mental status. Blood transfusion and/or crystalloid resuscitation is indicated.
• ClassIVhemorrhage:Approximately40%orgreatertotalbloodvolumeislost.Thepatientisseverely
hypotensivewithtachycardiaandtachypnea.SignsofclassIIIaremagnied.Rapidtransfusionof
blood is indicated along with emergent surgery to identify and address the source of bleeding.
90. The American Society of Anesthesiologists (ASA) suggests that the preanesthesia visit include the following:
1. An interview with the patient or guardian to establish a medical, anesthesia, and medication history
2. An appropriate physical examination
3. Indicated diagnostic testing
4. Review of diagnostic data (laboratory, ECG, radiographs, consultations)
5. AssignmentofanASAstatusscore
6. A formulation and discussion of anesthesia plans with the patient or responsible adult before
obtaining informed consent
91. What is included in the preanesthetic evaluation?
1. Examination of airway, heart, lungs
2. Review of vital signs including oxygen saturation
3. Measurement of height and weight
CHAPTER 2 PREOPERATIVE EVALUATION 23
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92. What are the two key features of the airway exam?
They are the oropharynx and mental space.
The oropharynx is examined with the patient in the sitting position, with the neck extended,
tongue out, and phonating. The four classes of oropharynx, originally described by Mallampati, are
grouped according to visualized structures (Fig. 2-1).
• ClassI:Softpalate,faucesuvula,anteriorandposteriortonsillarpillars
• ClassII:Softpalate,fauces,uvula
• ClassIII:Softpalate,baseofuvula
• ClassIV:Softpalateonly
The Mallampati classification of the oropharynx
The mental space is the distance from the thyroid cartilage to the inside of the men-
tum, measured while the patient sits with the neck in the sniff position. A correlation is found
between higher oropharyngeal class and decreased glottic exposure at laryngoscopy. The higher
oropharyngeal class combined with a mental space <2 fingerbreadths better predicts increased
difficulty with intubation. Other features include diminished neck extension, decreased tissue
compliance, large tongue, overbite, large teeth, narrow, high-arched palate, decreased temporomandibular joint mobility, and a short, thick neck.
Figure 2-1. Mallampati classification of the oropharynx. (From Phillips N: Berry and Kohn’s operating room technique, ed
12, St Louis, 2013, Mosby.)
93. What are the recommendations for taking home medications prior to surgery?
1. Generally all regular medications are continued.
2. Beta blockers should be continued for patients who use them to treat angina, symptomatic arrhythmias, or hypertension.
3. Hold oral hypoglycemic agents 8 hours preoperatively or AM dose.
4. Hold diuretics AM dose unless prescribed for CHF.
5. Hold ACE/ARB AM dose unless prescribed for CHF.
6. Hold insulin AM dose.
24 PART I PATIENT EVALUATION
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94. What comprises the preoperative evaluation of a diabetic patient?
How long has the patient had diabetes mellitus? How good is the glycemic control? Patients with
frequent insulin reactions and episodes of ketoacidosis (i.e., “brittle” diabetics) are more likely to be
metabolically unstable perioperatively. Diabetics with a long history of poor control are also more likely to
haveend-organdisease.Specically,theanesthesiologistshouldlookforevidenceofcoronarydisease
(often “silent”), hypertension, autonomic neuropathy (check for orthostatic changes in vital signs), renal
insufficiency, cardiomyopathy, and gastroparesis (ask about reflux and early satiety). Find out what medi-
cationsthepatienttakesforthediabetes,themostrecentdose,andcurrentbloodsugar.Somediabetics
may have diminished neck extension owing to atlantooccipital involvement with the stiff joint syndrome.
Seriouspreoperativemetabolicderangementsareseenmoreoftenininsulin-dependent
diabetic patients, especially in the setting of trauma or infection. Look for high or low glucose levels,
electrolyte abnormalities, ketoacidosis, hypovolemia, and hyperosmolarity.
Preoperative testing should include, at a minimum, glucose, electrolytes, blood urea nitrogen,
creatinine, urinalysis, and electrocardiogram. Additional lab work might include arterial blood gas,
ketones, osmolarity, calcium, phosphorus, and magnesium.
95. What are the recommendations for diabetic patients?
1. Type 1 and type 2 diabetics should discontinue intermittent short-acting insulin.
2. Patients with insulin pumps continue their lowest basal rate.
3. Type 1 diabetics take a small amount (⅓ to ½) of their intermediate to long-acting morning
insulin on the day of surgery to avoid ketoacidosis.
4. Type 2 diabetics take none or up to ½ dose of intermediate to long-acting insulin the day of the
operation.
5. Ultrashort-acting insulin such as glargine insulin can be taken as scheduled.
6. Metformin does not need to be discontinued before the day of surgery and will not cause hypoglycemia during fasting periods of 1 to 2 days. There is no risk for lactic acidosis in patients with
functioning liver and kidneys.
7. Oral hypoglycemic drugs are generally withheld on the day of surgery to avoid hypoglycemia.
96. What are some of the cardiac assessments for preoperative evaluation?
For predicting perioperative events, poor exercise tolerance has been defined as the inability to walk
fourblocks,climbtwoightsofstairs,ormeetfourMETS(carrying15to20lbs)duetodyspnea,
angina, or fatigue.
97. What are the definitions for risk stratification?
1. Surgicalrisk:
a. Lowrisk:Endoscopicprocedure,supercialprocedure,cataractsurgery,breastsurgery
b. Intermediaterisk:Peritoneal/thoracicsurgery,carotidendarterectomy,headandnecksurgery,
orthopedic surgery, prostate surgery
c. Highrisk:Emergent,aortic/majorvascular,peripheralvascular,anticipatedprolongedproce-
dure associated with large fluid shifts and/or blood loss
2. Patientrisk:
a. Lowrisk:Healthwithnomedicalproblems(ASAI)orwell-controlledchronicconditions(ASAII)
b. Highrisk:Multiplemedicalcomorbiditiesnotwellcontrolled(ASAIII)orextremelycompro-
misedfunctionsecondarytocomorbidities(ASAIV)
98. Which tests are needed prior to surgery?
1. Patients who are scheduled for outpatient surgery or low-risk surgery generally do not require
any preoperative testing.
2. Forpatientsscheduledforloworintermediaterisksurgery:
a. Hb/HCT only if there are clinical signs of anemia or anticipated major intraoperative blood loss
(>500 cc)
b. Urine pregnancy test the morning of surgery on any menstruating female
c. ECGonanypatientwiththefollowinghistory:ischemicheartdisease,compensatedorprior
heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease, and the
patient is having intermediate- or high-risk surgery
d. No CXR unless a history of significant pulmonary dysfunction with no previous CXR for one year
e. No PT/PTT unless a history of bleeding, easy bruising, or known liver disease
*
*ReprintedfromRolePA,GallowayFM:Thepreoperativeevaluation.InDukeJ,editor:Anesthesia secrets, ed 2, Philadel-
phia, 2000, Hanley & Belfus.
CHAPTER 2 PREOPERATIVE EVALUATION 25
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99. What is the American Society of Anesthesiologists (ASA) Classification?
• ASAI:Healthypatient
• ASAII:Apatientwithmildsystemicdisease
• ASAIII:Apatientwithseveresystemicdisease
• ASAIV:Apatientwithseveresystemicdiseasethatisaconstantthreattolife
• ASAV:Moribund,notexpectedtolive>24hoursregardlessoftheoperation
• ASAVI:Adeclaredbrain-deadpatientwhoseorgansarebeingremovedfordonorpurposes
100. Which conditions identified at preoperative evaluation most commonly result in
changes in the anesthetic care plan?
The conditions identified at preoperative evaluation that most commonly result in changes in the
anesthetic care plan are gastric reflux, Type 1 diabetes mellitus, asthma, and suspected difficult
airway.
101. Which patients are at higher risk for aspiration?
Higher risk patients are those with any degree of gastrointestinal obstruction, a history of gastro-
esophageal reflux, diabetes (gastroparesis), recent solid-food intake, abdominal distention (obesity,
ascites), pregnancy, depressed consciousness, or recent opioid administration (decreased gastric
emptying). In addition, nasooropharyngeal or upper gastrointestinal bleeding, airway trauma, and
emergency surgery are high-risk settings.
102. How are patients with Gastroesophygeal Reflex Disease (GERD) managed?
• NPO6to8hoursprior
• Carefulanesthesiaplanningtoavoidaspiration
• PoorlycontrolledGERDshouldbedelayeduntilbettercontrol
• PreanesthesiaH2blockers
• Rapidsequenceintubationwithcricoidpressure
• PostoperativesuctioningwithanNGtube
103. What is the role of renal disease in perioperative management of the patient?
Renal disease is associated with hypertension, cardiovascular disease, excessive intravascular
volume, electrolyte disturbances, and metabolic acidosis, and oftentimes the amount and type of
drugs administered must be altered.
104. When should dialysis be performed in elective cases?
Dialysis should be performed within 24 hours of surgery, but not immediately before to avoid acute
volume depletion and electrolyte alterations.
105. What are the perioperative considerations for diabetic patients?
1. Diabetic patients are at risk for multiorgan dysfunction, with renal insufficiency, strokes, periph-
eral neuropathies, visual impairment, and cardiovascular disease.
2. Chronically poor control increases comorbid conditions such as vascular disease, heart failure,
and infections.
3. Targeting control in the immediate perioperative period likely will not have a substantial impact
on outcomes in a diabetic having surgery.
4. Diabetic ketoacidosis and hypoglycemia are the only conditions that absolutely warrant periop-
erative intervention.
106. What is the significance of runny nose and postnasal drip in a child before an
elective surgery with general anesthesia or deep sedation? Should you postpone
surgery?
It has been shown that viral upper respiratory tract infections (URIs) are associated with intraopera-
tive and postoperative bronchospasm, laryngospasm, and hypoxia because of their effect on the
quality and quantity of airway secretions and increased airway reflexes to mechanical, chemical,
or irritant stimulation. In addition, there is evidence that the risk of pulmonary complications may
remain high for at least 2 weeks, and possibly 6 to 7 weeks, after a URI. Accordingly, some recommend avoiding anesthesia whenever possible for at least several weeks after a URI. However, in most
children, it is generally agreed that chronic nasal discharge poses no significant anesthesia risk. In
contrast, children with severe URI or lower respiratory tract infections almost always have their elective surgery postponed. Probably most anesthesiologists will proceed to surgery with a child with a
resolving, uncomplicated URI, unless the child has a history of asthma or other significant pulmonary
disease.
26 PART I PATIENT EVALUATION
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107. What particular medical and anesthetic problems are associated with obesity?*
Obesity is defined as excess body weight >20% over the predicted ideal body weight. Obese
patients have a higher incidence of diabetes, hypertension, and cardiovascular disease. There is
a higher incidence of difficulty with both mask ventilation and intubation. They have a decreased
functional residual capacity, increased O2 consumption and CO2 production, and, often, diminished
ventilation ranging from mild ventilation-perfusion mismatch to actual obesity-hypoventilation and
obstructive sleep apnea (pickwickian syndrome). These changes result in more rapid apneic desaturation. If the patients are pickwickian, they may have pulmonary hypertension with or without right
ventricular failure. Increased intraabdominal pressure is associated with hiatal hernia and reflux.
Because of their higher gastric volume and lower pH, obese patients are at greater risk for aspiration. Pharmacokinetics for many anesthetic agents are altered in them. Finally, regional anesthesia is
more difficult and more often unsuccessful.
108. How long should a patient fast before surgery?
Current guidelines for adults with no risk factors for aspiration include no solid food for 6 to 8 hours;
oral preoperative medications may be taken up to 1 to 2 hours before anesthesia with sips of water.
Currentfastingguidelinesforpediatricpatientsare:
• Clearliquidsupto2hourspreoperativelyinnewbornstoage6months
• Solidfoods,includingmilk,upto4hourspreoperativelyinnewbornstoage6months;upto
6 hours in children ages 6 months to 3 years; and up to 8 hours in children older than age 3
BiBliography
AbramsJ:Physicalexaminationoftheheartandcirculation.InRosendorffC,editor:Essential cardiology: principles and
practice,ed2,Totowa,NJ,2005,HumanaPress.
Awtry EH,LoscalzoJ:Evaluationofthepatientwithcardiovasculardisease.InAndreoliTE, Carpenter CCJ, Griggs RC,
LoscalzoJ,editors:Cecil essentials of medicine,ed6,Philadelphia,2004,Saunders.
Barber HD,MathesonJD, Fonseca R:Oral and maxillofacial surgery,ed2,St.Louis,2009,SaundersElsevier.
Bates B, Bickley L, Hoekelman R:A guide to physical examination and history taking,ed6,Philadelphia,1995,J.B.Lip-
pincott.
Bickley L:Bates guide to physical examination & history taking, ed 8, Philadelphia, 2003, Lippincott Williams & Wilkins.
GiglioJA, Abubaker AO:Preoperativeevaluation.InAbubakerAO, Benson KJ,editors:Oral and maxillofacial surgery
secrets,ed2,StLouis,Missouri,2007,Mosby/Elsevier.
Handler B:Historyandphysicalexamination.InKwonPH, Laskin DM,editors:Clinician’s manual of oral and maxillofacial
surgery,ed2,CarolStream,Ill,1997,Quintessence.
Longo D, Fauci A,etal.:Harrisons Principles of internal medicine, ed 18, New York, 2011, McGraw-Hill Professional.
Miller RD, Pardo M:Basics of anesthesia,ed6,Philadelphia,2011,ElsevierSaunders.
PowellJ,MoeJ,SteedMB:Surgicalophthalmologicexamination,Oral Maxillofac Surg Clin North Am24:557–572,2012.
Role PA, Galloway FM:Thepreoperativeevaluation.InDukeJ,editor:Anesthesia secrets, ed 2, Philadelphia, 2000, Hanley
& Belfus.
SarinEL,MooreJB:Initialassessment.InHarkenAH, Moore EE,editors:Abernathy’s surgical secrets, ed 5, Philadelphia,
2005, Mosby.
SeidelHM,BallJW,DainsJE,etal.:Mosby’s guide to physical examination,ed7,St.Louis,2011,MosbyElsevier.
SeidelHM,BallJW,DainsJE,etal.:Mosby’s guide to physical examination,ed6,StLouis,2006,Mosby.
SwankKM:Preoperativeevaluation.InDukeJ,editor:Anesthesia secrets, ed 3, Philadelphia, 2006, Mosby.
*ReprintedfromRolePA,GallowayFM:Thepreoperativeevaluation.InDukeJ,editor:Anesthesia secrets, ed 2, Philadel-
phia, 2000, Hanley & Belfus.
ELECTROCARDIOGRAM
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Richard D’Innocenzo, Ruben Figueroa, T.J. Dyer
1. What are the components of an electrocardiogram (ECG)? How do they relate to
the physiology of the myocardium?
The ECG tracing is a recording of the summed electrical vectors produced during depolarization and
repolarization of the heart. Electrical forces directed toward an electrode are represented as positive
forces (upward deflections), whereas forces directed away from an electrode are represented as
negative forces (downward deflections).
The standard representation of the cardiac cycle is seen in the ECG as the P wave, the QRS
complex, and the T wave. These waves and complexes are separated by regularly occurring intervals.
The P wave represents atrial depolarization and contraction. It originates in the sinoatrial
(SA) node. Usually, depolarization is noted on an ECG with repolarization usually too small or
obscured by other waves. Normal is <0.12 seconds. The PR interval represents conduction of an
impulse through the atrioventricular (AV) node. Normal is <0.2 seconds. The QRS complex represents the electrical activity of ventricular depolarization and contraction. Normal is <0.12 seconds. The ST segment represents the maintenance depolarization of the ventricles. The T wave
represents electrical repolarization of the ventricles and is not associated with any physical event
(Fig. 3-1).
2. How does the ECG pattern relate to the cardiac cycle?
The electrical impulse that is generated precedes the myocardial contraction that it stimulates (Fig. 3-2).
S1: Closure of the mitral valve
S2: Closure of the aortic valve
S3: In older adults, usually indicates a change in ventricular compliance that is pathologic
S4: Usually not heard but marks atrial contraction in normal healthy patients. It can also represent a
pathologic change in ventricular compliance.
P wave: Atrial depolarization
QRS complex: Ventricular depolarization
T wave: Ventricular repolarization
3. What is the function of the sinus node (SA), atrioventricular node (AV), and conduction fibers?
The SA node is the main pacemaker of the heart. The SA node fires at the beginning of the P wave
in the ECG, and we assume that atrial contraction begins at the peak of the P wave. The intrinsic SA
node rate is 60 to 100 beats/min. The atrial electrical conduction reaches the AV node and is insulated
from the rest of the ventricles.
The AV node provides the necessary electrical conduction delay to give time for the ventricles to
fill with blood before ventricular contraction. The AV node fires intrinsically at about 60 beats/min.
From the AV node and bundle of His, the electrical current reaches the left and right bundle
branches within the ventricular septum and then to the Purkinje system, depolarizing the entire
ventricle. Ventricles depolarized intrinsically around 30 to 40 beats/min (Fig. 3-3).
4. When analyzing ECGs, what are the five factors to consider?
• Rate
• Rhythm
• Axis
• Hypertrophy
• Infarction
5. What are the markings of an ECG?
1 small square (light lines) = 1 mm = 1 mV = 0.04 seconds
1 large square (dark lines) = 5 mm = 5 mV = 0.2 seconds
Normal paper speed = 25 mm/s
CHAPTER 3
27
28 PART I PATIENT EVALUATION
Atrial
Ventricular
Ventricular
Voltage
Time (s)
0
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Atria Ventricles
+1
R wave
RR interval
ST segmentPR interval
QRS
duration
QT interval
S wave
Q wave
The ECG cannot show
the electrical activity of
these five structures.
T wave
P wave
0
(mV)
AV
SA
node
node
Bundle of His
Bundle branches
Purkinje network
–1
00.2 0.40.6 0.81.0
1.21.4 1.61.8 2.
Figure 3-1. Components of the electrocardiogram (ECG) recording. AV, atrioventricular; SA, sinoatrial. (From Boron WF:
Medical physiology, updated ed 2, Philadelphia, 2011, Saunders.)
depolarization
depolarization
repolarization
R
Atrial
systole
Ventricular
systole
T
P
Q
S
PR
interval
QRS
ST
segment
Figure 3-2. Normal EKG waveforms, intervals, and correlation with events of the cardiac cycle. The P wave represents
atrial depolarization, followed immediately by atrial systole. The QRS represents ventricular depolarization, followed
immediately by ventricular systole. The ST segment corresponds to phrase 2 of the action potential, during which
time the heart muscle is completely depolarized and contraction normally occurs. The T wave represents ventricular
repolarization. The PR interval, measured from the beginning of the P wave to the beginning of the QRS, corresponds to
atrial depolarization and impulse delay in the atrioventricular (AV) node. The QT interval, measured from the beginning of
the QRS complex to the end of the T wave, represents the time from initial depolarization of the ventricles to the end of
ventricular repolarization. (From Urden LD, Stacy KM, Lough ME: Critical care nursing: diagnosis and management, ed 7,
St Louis, 2014, Mosby.)
6. How do I determine the heart rate from an ECG?
The distance between the heavy lines represents 1/300 min. So two 1/300-min units = 2/300 min =
1/150 min (or 150/min rate), and three 1/300 units = 3/300 min = 1/100 min (or 100/min rate). So,
to determine the actual rate, find the R wave nearest the dark line and then count the dark lines
until the next R wave. If the R wave falls on the next dark line, the rate is 300; if it falls on the
second dark line, the rate is 150; if it falls on the third dark line, the rate is 100, and so on
(Fig. 3-4).
QT interval
Internodal tracts
Left posterior fascicle
Sinoatrial node
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Anterior
Middle
Posterior
Aorta
Pulmonary artery
Bachmann's bundle
Left bundle branch
Figure 3-3. Conduction system of the heart. (From Ignatavicious DD, Workman ML: Medical-Surgical Nursing: Critical Thinking for Collabarative Care, ed 5, St. Louis, 2006, Saunders.)
Atrioventricular node
Bundle of His
Right bundle branch
Left anterior fascicle
Purkinje fibers
CHAPTER 3 ELECTROCARDIOGRAM 29
30 PART I PATIENT EVALUATION
Ref. 1
A
B
23
75
123
4
56
7
8
Method 3: 18 small boxes
Method 2:
Method 1:
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300
150
100
Ref. 12334
300
150
100
Figure 3-4. Determining heart rate-sequence method. To measure the ventricular rate, find a QRS complex that falls on
a heavy dark line. Count 300, 150, 100, 75, 50 until a second QRS complex occurs. This will be the heart rate. A, Heart
rate = 100 beats/min. B, Heart rate = 75 bea ts/min. (From Crawford MV, Spence MI: Commonsense approach to coronary
care, rev ed 6, St Louis, 1994, Mosby.)
1234
Figure 3-5. Calculating heart rate. Method 1: Number of R-R Intervals in 6 seconds × 10 (e.g., 8 × 10 = 80/min). Method 2:
Number of large boxes between QRS complexes divided into 300 (e.g., 300 divided by 4 = 75/min). Method 3: Number
of small boxes between QRS complexes divided by 1500 (e.g., 1500 divided by 18 = 84/min). (From Urden LD, Stacy KM,
Lough ME: Critical care nursing: diagnosis and management, ed 7, St Louis, 2014, Mosby.)
Alternatively, the rate can be determined by multiplying the number of beats in 6-second strips
(two 3-second marks) by 10, or through another method in which the number of small boxes between
QRS complexes is divided by 1500 (Fig. 3-5).
7. How do I determine the axis of the heart’s electrical impulse?
Lead I and aVF are perpendicular to each other and are used to determine axis. Lead I flows from
right to left, and lead aVF flows from superior to inferior. Remember, the more positive the deflection
in each lead indicates the axis following in the same direction. A normal axis (−30 to +90 degrees)
will have positive defections in both leads I and aVF. Left axis deviation (−30 to −90 degrees)
CHAPTER 3 ELECTROCARDIOGRAM 31
−
°
+90°
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− 90°
− 60°
LAD
+
aV
L
− 30
150°
aV
− 120°
+
R
Extreme
RAD
±180°
+150°
+
III
+120°
Figure 3-6. Determination of electrical axis. (From Beachey W: Respiratory Care Anatomy and Physiology: Foundations for
Clinical Practice, ed 2, St. Louis, Mosby, 2007.)
aV
+
F
II
+
+60°
+
I
0°
+30°
demonstrates positive deflection in lead I and negative deflection in aVF. Differentials for left axis
deviation may include left ventricular hypertrophy or bundle branch block. Right axis deviation (+90
to ±180 degrees) demonstrates negative deflection in lead I and positive deflection in aVF. Differentials for right axis deviation may include right ventricular hypertrophy, lateral wall MI, or left posterior
fascicular block. Extreme right axis deviation is negative in both leads I and aVF and is rare (Fig. 3-6).
8. Can the ECG provide information about the contractility of the myocardium?
No. To determine the effectiveness of the heart’s mechanical activity, the patient’s blood pressure and
pulse need to be assessed.
9. What do the various types of PR intervals indicate?
The normal PR interval (<0.2 seconds) represents the lag in electrical conduction through the AV node.
It allows time for ventricular filling. A narrow PR interval (<0.12 seconds) may reveal accelerated
AV conduction (as in Wolff-Parkinson-White syndrome) or premature junctional complexes. Wide PR
intervals (>0.2 seconds) indicate first-degree AV block. Progressively lengthening PR intervals indicate
second-degree AV block or multifocal atrial tachycardia.
10. If the AV junction paces the heart, how will the P wave appear on the ECG?
The electrical impulse that is produced will travel in a retrograde direction to activate the atria. In
leads II, III, and aVF, the P wave will be inverted if present, and it will be seen before the QRS complex
if the atria depolarize before the ventricles. If the ventricles and atria depolarize at the same time, the
P wave will not be visualized, as it will be buried in the QRS complex. If the atria depolarize after the
ventricles, the P wave will appear after the QRS complex or can present as a distortion of the end of
the QRS complex (Fig. 3-7).
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