Electrolyte EKG lecture

Question 1

List 2 groups of Electrolyte disturbances. Are they common?

Answer 1

Potassium disorders
Calcium disorders

Common and may profoundly alter the EKG

Question 2

What is referred to as “The imitator” bc it can do most anything to the EKG?
What is the classic presentation?

Answer 2

“The imitator” – can do most anything to the EKG
Classic presentation - progressive evolution of changes in EKG that end in V-fibrillation

Question 3

Hyperkalemia: Describe the EKG as K+ begins to rise

Answer 3

Peaking of T waves
Diffuse – all leads
Symmetric

Question 4

What is a DDX for hyperkalemia?

Answer 4

ACS hyperacute T waves confined to specific coronary distribution

Question 5

Hyperkalemia: What happens to the EKG after peaking of T waves?

Answer 5

PR interval prolonged , then P wave gradually flattens & then disappears, T waves are even more peaked

Question 6

Hyperkalemia:
1) What ultimately forms as K+ continues to rise?
2) Is there axis deviation?

Answer 6

1) Ultimately the QRS complex widens until merging with T wave forming a sine wave
2) RAD develops; the presence of RAD may be an important clue that the wide QRS complexes are the result of hyperkalemia

Question 7

List some causes of RAD

Answer 7

RVH
Left posterior fascicular block
Chronic and acute pulmonary disease
Hyperkalemia
Ventricular ectopy/V-tach
Old lateral MI – electrical activity moves away from left lateral wall toward the right
Misplaced leads
Dextrocardia with situs inversus

Question 8

Hyperkalemia: What are some other changes you may see?

Answer 8

May also see high degree AV block and BBB
Asystole or V-Fib may eventually develop

Question 9

Hyperkalemia: Are the EKG changes always in the same order? Explain

Answer 9

Classic changes often occur in the above order – but they don’t have to as progression to V-fib can occur acutely

Question 10

Wide QRS, RAD, slow junctional escape rhythm may describe a pt with what?

Answer 10

Hyperkalemia

Question 11

Hypokalemia:
1) What are ECG changes a measure of?
2) What does hypokalemia rarely cause?
3) What can severe hypoK+ also cause?

Answer 11

1) ECG changes are better measure of serious toxicity than serum K+ levels
2) Rarely causes ST segment elevation
3) Prolonged QT interval, SVT and V-Tach

Question 12

Hypokalemia: Several changes occur in no specific order; list them

Answer 12

1) ST segment depression
2) Flattening of T wave with prolonged QT interval
3) Appearance of U wave: Best seen in anterior leads; not specifically diagnostic of hypo K+

Question 13

Describe U Waves

Answer 13

Appear after T waves in cardiac cycle
Normal or pathologic
U wave usually same axis as T wave
Often best seen in V2 & V3
May resemble biphasic T wave or large P wave
Besides hypokalemia, U waves may develop secondary to CNS disease and antiarrhythmic drugs, normal hearts and normal K+ levels usually when 60-65 bpm

Question 14

Calcium disorders: Alterations in serum calcium primarily affect what?

Answer 14

the QT interval

Question 15

Differentiate between hypercalcemia and hypocalcemia on an ECG

Answer 15

1) Hypocalcemia = prolongs QT interval
-Increased risk for Torsades de Pointes
2) Hypercalcemia = shortens QT interval

Question 16

Describe QT intervals

Answer 16

QT interval is proportional to HR
Faster HR = shorter QT
Slower HR = longer QT
QT = ~40% of the R to R duration or measure
R-R interval and QT should end prior to mid-point

Question 17

Hypothermia: EKG changes associated with very low body temp can mimic other cardiac conditions; explain

Answer 17

1) Everything slows down - Sinus bradycardia & all segments and intervals become prolonged
2) Specific type of ST segment elevation may be seen called a J wave or Osborn wave
Abrupt ascent at J point with equally sudden plunge back to baseline
Disappear as the patient is re-warmed

Question 18

Hypothermia: What types of arrhythmias may it cause?
2) What can mimic AF/AFL?

Answer 18

1) Other slow arrhythmias: slow A. fib or junctional rhythm
2) Muscle tremor artifact from shivering
& can mimic AF/AFL

Question 19

Give examples of drugs that can cause arrythmias

Answer 19

Digitalis
Sodium channel blockers
Medications that prolong the QT interval

Question 20

Digitalis:
1) What is it? Is it used often?
2) What can it cause?
3) When?

Answer 20

1) + inotrope Not used much anymore
2) Can cause almost any arrhythmia
3) Therapeutic levels or toxic levels

Question 21

Digitalis: What can therapeutic blood levels cause? Why?

Answer 21

1) “Dig effect” – normal and predicable characteristic changes to the EKG
2) Negative chronotrope
Positive inotrope

Question 22

Describe the changes digitalis causes on an EKG

Answer 22

1) ST segment depression with flattening or inversion of T wave
Gradual down slope vs symmetric ST depression from cardiac ischemia, sometimes more difficult DDX from LVH with repol abnormality (Digitalis sometimes used in HF with LVH)
2) More prominent in leads with tall R waves
3) ST segment depression very gradual

Question 23

Toxic manifestations of digitalis can cause what?

Answer 23

1) conduction blocks and tachyarrhythmias

Question 24

Toxic manifestations of digitalis: Describe the suppression and conduction

Answer 24

Sinus node suppression/exit block, especially in sick sinus syndrome
Slowed conduction through the AV node – result in any degree or AVB
Dig can be useful in slowing conduction of AVB at rest but lost during exertion

Question 25

Toxic manifestations of digitalis: Describe the tachyarrhythmias

Answer 25

Tachyarrhythmias – Dig enhances autonomic behavior of all cardiac conducting cells PAT & PVC are most common arrhythmia, but junctional rhythms, AF, and AFL are also seen

Question 26

Sodium channel blockers: 1) What are they important in? 2) Give an example of these 3) What do EKG findings include?

Answer 26

1) Important in nerve conduction, affect the EKG 2) TCA are common Rx – amitriptyline, but also antiarrhythmics such as sotalol, amiodarone …. 3) EKG findings include a tachycardia, a wide QRS complex, a right axis, a long QT interval, and a tall R wave in the right sided leads – aVR and V1

Question 27

Give examples of abx that can prolong QT interval

Answer 27

Macrolides and fluoroquinolones Antifungals Psychotropic drugs – antipsychotics, TCA, SSRI, and methadone GI meds, antineoplastic meds Diuretics by causing hypoK and hypoMg

Question 28

What groups of meds prolong QT interval?

Answer 28

1) Antiarrhythmic agents and antidepressants agents – sodium channel blocking agents 2) Abx

Question 29

QT interval: 1) How long is it? 2) What is QTc?

Answer 29

1) 40% of normal cardiac cycle as measured by R-R duration, varies with rate, shorter with faster rates 2) QT duration/square root of R-R interval, most accurate between HR of 50-120/min -Machine does a good job of calculating this as QTc

Question 30

QT interval: 1) When should it not exceed 500ms? Why?

Answer 30

During therapy with meds that may prolong QT interval 550ms if underlying BBB Reduces risk of R on T ventricular arrhythmia

Question 31

QT interval: Explain inherited d/o associated with “prolonged QT interval”

Answer 31

~ 50% - mutation in gene coding for K+ channels, all family members should be checked if found in 1 family member Brugada pattern

Question 32

Causes of prolonged QT interval include what?

Answer 32

1) The tail of the “hypos”……… Hypocalcemia Hypokalemia Hypomagnesemia hypothermia 2) Congenital/inherited d/o Brugada pattern 3) Medications 4) Cardiac ischemia

Question 33

Pericarditis: Describe the ST changes

Answer 33

ST segment elevation Diffuse ST segments tends to be saddle shaped or concave up Reciprocal ST depression in NOT seen STE greater in lead III than II = probably STEMI

Question 34

Pericarditis: 1) Describe the T waves 2) Describe the Q waves

Answer 34

1) T wave flattening/inversion Pericarditis – T wave inversion only occur after STE has returned to baseline STEMI – T wave inversion usually preceds normalization of the STE 2) No Q waves

Question 35

PR segment and TP segment depression may be seen with what?

Answer 35

Pericarditis

Question 36

The spodick sign: Describe this

Answer 36

Down sloping TP segment – end of T wave to the start of P wave If you see this sign in a patient, you suspect has pericarditis …. Unlike angina, pain of pericarditis is sharp, worse with inspiration and coughing, and felt diffusely across the chest often radiating to upper back. Eased when sitting and leaning forward May auscultate a friction rub May generate low voltage EKG

Question 37

Low voltage EKG: What are the most sensitive criteria?

Answer 37

1) Total QRS voltage in leads I, II, III is < 15 mm 2) Sum of all QRS voltage in leads V1-3 < 30 mm

Question 38

Low voltage EKG: What are the most specific criteria?

Answer 38

1) QRS voltage in all limb leads < 5 mm 2) QRS voltage in all V leads < 10 mm

Question 39

When can electrical alterans occur?

Answer 39

Sufficient pericardial effusion that cause the heart to rotate within the fluid filled sac

Question 40

Myocarditis: 1) Define it 2) What are the most common EKG changes?

Answer 40

1) Diffuse inflammation of the myocardium 2) Conduction blocks and hemiblocks

Question 41

COPD: 1) What can it cause? 2) What can it do to EKGs?

Answer 41

1) Chronic cor-pulmonale and RV HF 2) Right atrial enlargement – P pulmonale Right ventricular hypertrophy with repole abnormality – cor pulmonale

Question 42

What are some EKG findings in acute massive PE?

Answer 42

1) RV dilation with repole anbl (takes time so may not see early) 2) RBBB 3) S1Q3 – large S wave in lead I, deep Q wave in lead III (Q wave limited to lead III, unlike inferior MI) 4) S1Q3T3 – T wave may also be inverted in lead III

Question 43

Sleep disorders like sleep apnea put you at increased risk for what? Why?

Answer 43

1) Atrial (a leading cause of AF) and ventricular arrhythmias, heart block and nocturnal angina, MI, systemic and pulmonary hypertension, & RHF 2) Transient hypoxia and altered autonomic function

Question 44

Athlete’s heart may be seen in who?

Answer 44

Distance runners/cyclist/cross country skiing – endurance training

Question 45

What are some EKG changes in athlete's heart?

Answer 45

1) Sinus bradycardia – may be profound 2) NSST-T wave changes -ST segment elevation in precordial leads with T wave flattening or inversion -T wave inversion in V1-4 especially common in black athletes -Voltage criteria for LVH and sometimes RVH -Incomplete RBBB -Junctional rhythms and wandering atrial pacemaker -1st degree or 2nd degree Wenckebach AV block -Notched QRS in V1

Question 46

Pre-participation sports exam looks for what? Explain

Answer 46

1) Obstructive Hypertrophic CardioMyopathy V-tach/fib 2) H/O symptoms: dyspnea, dizziness, syncope, CP, palpitations Family h/o congenital heart disease, sudden death or obstructive HCM 3) 12 lead EKG, TTE, stress testing, etc.