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Chapter 20 Test — Electrolyte and Drug Effects on ECG
26 questions · 26 min · +4 / -1
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Question 1
Question 1
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A 62-year-old man with chronic kidney disease and hypertension attends the emergency department with weakness, palpitations and chest discomfort. Which ECG finding appears
earliest
in hyperkalaemia?
A.
Tall tented T wave
B.
ST elevation
C.
Absent P wave
D.
Broad QRS complex
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Question 2
Question 2
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A 55-year-old man on maintenance haemodialysis missed his last session and comes to the emergency department feeling dizzy and unwell. His ECG is shown. The most likely diagnosis is:
A.
Hyperkalaemia
B.
Hypernatraemia
C.
Hypercalcaemia
D.
Hypocalcaemia
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Question 3
Question 3
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A patient's ECG shows tall, tented T waves, a wide QRS complex and absent P waves. Which condition is most likely?
A.
Bundle branch block
B.
Acute myocardial infarction
C.
Hyperkalaemia
D.
Ventricular ectopic
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Question 4
Question 4
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All of the following are electrocardiographic features of severe hyperkalaemia EXCEPT:
A.
Sine-wave pattern
B.
Loss of P waves
C.
Peaked T waves
D.
Presence of U waves
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Question 5
Question 5
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A 68-year-old man with stage 4 CKD and diabetes presents with weakness. Serum potassium is 7.2 mEq/L and his ECG shows peaked T waves, a widened QRS and an evolving sine-wave pattern. What is the most appropriate
immediate
intervention?
A.
IV insulin with dextrose
B.
IV calcium gluconate
C.
IV sodium bicarbonate
D.
Immediate haemodialysis
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Question 6
Question 6
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A patient is found to have hyperkalaemia but the ECG shows no changes at all. All of the following are appropriate treatments EXCEPT:
A.
Glucose + insulin
B.
Sodium bicarbonate
C.
Calcium gluconate
D.
Potassium-binding resins
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Question 7
Question 7
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A patient with chronic kidney disease presents with palpitations. The 12-lead ECG shown demonstrates tall, narrow, pointed T waves with a preserved narrow QRS. What is the most likely diagnosis?
A.
Hyperkalaemia
B.
Hypokalaemia
C.
Hypercalcaemia
D.
Hypocalcaemia
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Question 8
Question 8
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A 55-year-old man on long-term furosemide has an ECG showing flattened T waves, prominent U waves best seen in V2-V3, mild ST depression and an apparently prolonged QT interval. Which electrolyte abnormality is most likely responsible?
A.
Hypocalcaemia
B.
Hypokalaemia
C.
Hyperkalaemia
D.
Hypercalcaemia
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Question 9
Question 9
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The 12-lead ECG shown is from a patient on thiazide diuretics with muscle weakness. It shows flattened T waves followed by prominent U waves, best seen in the mid-precordial leads. What is the likely diagnosis?
A.
Hypokalaemia
B.
Hyperkalaemia
C.
Hypothermia
D.
Hypocalcaemia
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Question 10
Question 10
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A 55-year-old smoker diagnosed two months ago with squamous cell carcinoma of the lung presents with polyuria, polydipsia, nausea and confusion. His ECG, shown here, is unremarkable apart from a strikingly short QT interval with an almost absent ST segment. Which metabolic abnormality is most likely?
A.
Hypernatraemia
B.
Hypercalcaemia
C.
Hypokalaemia
D.
Hyponatraemia
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Question 11
Question 11
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Which ECG change is characteristic of hypocalcaemia?
A.
ST-segment depression
B.
Prolongation of the ST segment
C.
Inversion of the T wave
D.
Prolongation of the PR segment
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Question 12
Question 12
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Identify the underlying metabolic disorder from the ECG shown, which demonstrates a long, flat, isoelectric ST segment pushing a normally shaped T wave late, with an overall prolonged QT interval.
A.
Hypokalaemia
B.
Hyperkalaemia
C.
Hypercalcaemia
D.
Hypocalcaemia
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Question 13
Question 13
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ST-segment elevation on the ECG is NOT seen in:
A.
Pericarditis
B.
Hyperkalaemia
C.
Hypocalcaemia
D.
Hypothermia
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Question 14
Question 14
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Torsades de pointes is precipitated by all of the following EXCEPT:
A.
Hyponatraemia
B.
Hypocalcaemia
C.
Hypomagnesaemia
D.
Hypokalaemia
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Question 15
Question 15
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A 70-year-old woman with chronic kidney disease on long-term loop diuretic therapy collapses after complaining of palpitations and dizziness. Her ECG captures a run of polymorphic ventricular tachycardia twisting around the baseline, on a background of a prolonged QT. Which electrolyte abnormality must be considered?
A.
Hypermagnesaemia
B.
Hypomagnesaemia
C.
Hypernatraemia
D.
Hyponatraemia
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Question 16
Question 16
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A 72-year-old woman with permanent atrial fibrillation has been taking digoxin 0.125 mg daily. She is asymptomatic, her serum digoxin is 1.1 ng/mL (therapeutic 0.5-2.0) and potassium is 4.3 mEq/L. Her ECG is shown, with downsloping 'scooped' ST depression in the lateral leads, a mildly long PR interval and a short QT. This is best interpreted as:
A.
Digoxin toxicity requiring digoxin-specific Fab fragments
B.
Hypokalaemia-induced ST depression requiring potassium replacement
C.
Lateral subendocardial ischaemia requiring urgent coronary angiography
D.
The expected therapeutic digoxin effect, requiring no change in therapy
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Question 17
Question 17
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Digitalis at therapeutic levels produces which of the following ECG changes?
A.
Tall T waves
B.
ST-segment elevation
C.
Prolonged QT interval
D.
Prolonged PR interval
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Question 18
Question 18
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Which of the following drugs does NOT prolong the QT interval?
A.
Amiodarone
B.
Quinidine
C.
Digitalis
D.
Amitriptyline
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Question 19
Question 19
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An ECG is performed on a patient suspected of digoxin toxicity. Which of the following would you NOT expect to see?
A.
Ventricular bigeminy from frequent ectopic beats
B.
Paroxysmal atrial tachycardia with a fast ventricular rate
C.
Regularisation of a previously irregular atrial fibrillation
D.
Bidirectional ventricular tachycardia
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Question 20
Question 20
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In a patient with chronic atrial fibrillation whose pulse becomes regular at 60/min, the most probable cause is:
A.
Sleep
B.
Digitalis toxicity
C.
Sinoatrial block
D.
Hypothyroidism
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Question 21
Question 21
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A 60-year-old man on digoxin, recently started on spironolactone, presents with anorexia, nausea, yellow-green vision and confusion. ECG shows scooped ST depression, sinus bradycardia at 38/min and ventricular bigeminy. Serum digoxin is 4.2 ng/mL, potassium 6.4 mmol/L and creatinine 1.8 mg/dL. Which intervention specifically reverses life-threatening digitalis toxicity by binding the drug in plasma?
A.
Activated charcoal 50 g orally every 4 hours
B.
IV calcium gluconate for the hyperkalaemia
C.
Phenytoin loading dose for the digitalis-induced arrhythmia
D.
IV digoxin-specific Fab antibody fragments (DigiFab)
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Question 22
Question 22
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A young woman on antidepressants arrives in the emergency department with altered sensorium and hypotension. Her ECG, shown here, demonstrates sinus tachycardia with a broad QRS, a rightward terminal axis and a tall terminal R wave in aVR. The next best step is:
A.
IV sodium bicarbonate
B.
Haemodialysis
C.
Fomepizole
D.
Flumazenil
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Question 23
Question 23
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The cardiac conduction defects seen with tricyclic antidepressants are due to:
A.
Noradrenaline and serotonin reuptake inhibition
B.
Antimuscarinic action on the heart
C.
Blockade of fast myocardial Na
+
channels
D.
Both noradrenaline reuptake inhibition and antimuscarinic action
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Question 24
Question 24
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A patient on an antiarrhythmic develops marked QT prolongation and a run of polymorphic ventricular tachycardia. Which agent is most strongly associated with this proarrhythmic effect?
A.
Quinidine
B.
Amiodarone
C.
Magnesium sulphate
D.
Lignocaine
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Question 25
Question 25
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Which statement best describes the mechanism by which sotalol prolongs the QT interval?
A.
It enhances potassium efflux, accelerating ventricular repolarisation
B.
It opens potassium channels, shortening the QT interval
C.
It blocks potassium channels, inhibiting ventricular repolarisation and prolonging the QT
D.
It increases sodium influx, accelerating depolarisation and shortening the QT
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Question 26
Question 26
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A 55-year-old man presents with chest pain and diaphoresis 30 minutes after using cocaine. Pulse 94/min, BP 161/92 mmHg. His ECG shows inverted T waves in I, aVL and V5-V6, and urine toxicology is positive for cocaine. Which drug is CONTRAINDICATED in his management?
A.
Propranolol
B.
Phentolamine
C.
Diazepam
D.
Nitroglycerine
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