100 ECG’s
Conduction Defects: (17 questions)

Questions

• 1
  As a medical student, you attend a teaching session with your cardiology consultant who has prepared an exciting case for you to discuss today. He starts off by handing you the following ECG and asks you to make a diagnosis. Which of the following is the diagnosis ?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  First degree heart block

  b

  Left bundle branch block

  c

  Right bundle branch block

  d

  Trifascicular block

  e

  Dextrocardia
  Explanation: The patient has a normal PR interval with a broad QRS complex. The pattern of the QRS complex in V1 and V6 is consistent with left bundle branch block (LBBB). The Normal PR interval excludes first degree heart block and Trifascicular block (First degree heart block, LBBB and Left Axis deviation).
• 2
  You are revising for your finals and you bump into a strange ECG on one of your lecture slides with no annotations (shown). You attempt to interpret it. What are the abnormalities in this ECG ?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Right bundle branch block

  b

  First Degree Heart block with NSTEMI

  c

  Second degree heart block with left bundle branch block

  d

  First degree heart block with left bundle branch block

  e

  Paced rhythm
  Explanation: This ECG is showing mutiple abnormalities. The most obvious one is the fixed prolonged PR interval indicative of first degree heart block. The second abnormality is a left axis deviation (note leads I, II and aVF). And the third abnormalities is a wide QRS complex (>120ms) in a left-bundle branch block morphology.
• 3
  As you are approaching your final exams, you are revising the different types of cardiac arrhythmias when you stumble upon this ECG (shown). What type of arrhythmia is this?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  First degree heart block

  b

  Second degree heart block (Mobitz I)

  c

  Second degree heart block (Mobitz II)

  d

  Third Degree heart block

  e

  Trifascicular block
  Explanation: This ECG shows regular P-waves that are not related to the QRS complexes; which are in turn regular in nature as well. The rate is slow. This is consistent with a diagnosis of third (or complete) heart block.
• 4
  A new patient is being assessed in the emergency department for chest pain. The doctor reviews the patient who complains of central chest pain, tender chest wall, and pain that increases on inspiration. The doctor asks a medical student to perform base line investigations including observations and an ECG. The medical student runs back to the doctor with an ECG and is worried about anterior ST elevations. What is the likely diagnosis ?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Dual chamber pacing

  b

  ST-elevation MI

  c

  Non-ST-elevation MI

  d

  LBBB

  e

  RBBB
  Explanation: This ECG shows a dual chamber pace maker in action. The pace maker has two leads, one in the atria (sensing) and one in the ventricle (pacing). This is visible with a pacing spike after the p-waves but before the QRS complex. Because the ventricle pacing lead is in the right ventricle, the right ventricle depolarises first, which gives a LBBB pattern on the ECG when there's actually no bundle branch block.
• 5
  A 51 year old lady is being assessed at the pre-op clinic for an upcoming hysterectomy. She is a non-smoker, with no past medical history except for peri-menopausal bleeding. She takes norethisterone and tranexamic acid. A routine ECG is performed (shown). What is the most likely diagnosis ?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  Right bundle branch block

  b

  Left bundle branch block

  c

  Hyperkalaemia

  d

  Rate-controlled Ventricular tachycardia

  e

  Atrial fibrillation with right bundle branch block
  Explanation: This ECG shows a broad QRS complex in a left-bundle branch block (LBBB) morphology (Note V1 and V6). In this scenario, it is an incidental finding and it is prudent to examine previous ECGs to determine if this is a pre-existing pattern. If the patient had presented with chest pain, it is important to consider the diagnosis of an acute MI which could have led to a new-onset LBBB (which in turn masks ischaemic changes).
• 6
  During the 8am ward round with your consultant, you review a patient 14 hours post admission to the coronary care unit with the following initial ECG and chest pain. During your review, the patient develops severe shortness of breath, a pansystolic murmur at the left lower sternal edge and hypotension. What is the diagnosis ?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Ventricular septal rupture

  b

  Papillary muscle rupture

  c

  Free ventricular wall rupture

  d

  First degree heart block

  e

  Cardiac tamponade
  Explanation: The ECG shows Left Bundle Branch Block, which when accompanied by a history of acute coronary syndrome (chest pain) makes the diagnosis an ST-elevation myocardial infarction (STEMI). Patients are normally treated with revascularisation in the form of angioplasty. All the listed options are recognized complications of myocardial infarctions. However, acute pulmonary oedema (shortness of breath), decreased cardiac output (hypotension) and a pansystolic murmur suggest either acute mitral regurgitation (papillary muscle rupture), whose murmur is audible most at the Apex, or a ventricular septal defect (ventricular wall rupture), whose murmur is heard at the left lower sternal edge (flow is from left ventricule to right)
• 7
  24 hours after an inferior infarct, a patient develops a sudden reduction in the blood pressure and a collapse on the coronary care unit. His heart rate is noted to be 30bpm. His blood pressure is 80/38 and he is very short of breath. What is the most appropriate long-term treatment ?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Aspirin and Clopidogrel

  b

  Atropine

  c

  Cardiopulmonary resuscitation

  d

  Transcutaneous pacing

  e

  Permanent Pacemaker
  Explanation: The patient has developed complete heart block, a recognized complication of myocardial infarction affecting the AV node. The best long-term solution is a permanent (transvenous) pacemaker. In the interim, Atropine and Transcutaneous pacing could be attempted as the patient is haemodynamically unstable.
• 8
  A sixty-two year old patient 48 hours after being admitted with a NSTEMI has a routine in patient ECG. He is asymptomatic and pain-free and is due to be discharged tomorrow. His ECG (partial) is shown. What is the best course of management ?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Permanent pacemaker

  b

  Temporary pacing wire

  c

  cardiac resynchronisation therapy (CRT)

  d

  Do Nothing

  e

  AV node ablation
  Explanation: The PR interval is prolonged (>0.20seconds) suggesting a diagnosis of first degree heart block, which could be coincidental or secondary to the infarction (NSTEMI). If the patient is asymptomatic (no collapses, no hypotension) then it would be best to manage them conservatively. If the patient is symptomatic, then a permanent pacemaker would be the treatment of choice.
• 9
  During ward round, you see a patient 12 hours post admission to the coronary care unit with the following initial ECG and chest pain. He has had the appropriate treatment and is being monitored on the unit. As you are reviewing him, he develops severe shortness of breath, a pansystolic murmur at the apex and hypotension. What is the diagnosis ?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  Ventricular septal rupture

  b

  Papillary muscle rupture

  c

  Free ventricular wall rupture

  d

  First degree heart block

  e

  Cardiac tamponade
  Explanation: The ECG shows Left Bundle Branch Block, which when accompanied by a history of acute coronary syndrome (chest pain) makes the diagnosis an ST-elevation myocardial infarction (STEMI). Patients are normally treated with revascularisation in the form of angioplasty. All the listed options are recognized complications of myocardial infarctions. However, only Papillary muscle rupture, which leads to severe acute mitral regurgitation, will give you acute pulmonary oedema (shortness of breath), decreased cardiac output (hypotension) and a pansystolic murmur at the apex.
• 10
  73 year old man complains of chest pain while gardening. He has a past medical history of essential hypertension and smoking, but no family history of heart disease. He phones the ambulance which does an ECG on route to hospital. The student paramedic is challenged by the ECG findings and asks his senior for advice to make a decision on whether this patient should go for primary angioplasty or not. What is the most appropriate description for the ECG findings?
  
  Difficulty: Hard     Topic: Conduction defects
  a

  Inferolateral ST-elevation

  b

  LVH and ST elevation in anterior leads

  c

  LBBB

  d

  Left Axis Deviation and LVH

  e

  Left Axis Deviation, LVH and LBBB
  Explanation: Most of these answers are correct, with the exception of A. There is obvious Left Bundle Branch block (negative wide QRS in V1); therefore, answer B is not appropriate as it is not possible to comment on ST segment elevation with a LBBB pattern. The ECG also clearly shows LVH by Sokolow-Lyon index (S in V1 + R in V5/V6 >35mm or 7 large boxes), and finally it is likely from leads I,II and aVF that the ECG has left axis deviation.
• 11
  A 60 year old patient attends the emergency department with sudden onset central crushing chest pain of 45 minute duration. He has a history of hypertension and smoking. The triage nurse has doubts over the ECG as “it doesn’t seem to have a normal pattern”. You review the ECG (shown) and make which of the following decisions ?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  Give IV Amiodarone

  b

  Send the patient for angioplasty

  c

  Send the patient home as his condition is benign

  d

  Start Cardiopulmonary resuscitation

  e

  Start heparin and fondaparinux
  Explanation: In cases where the patient presents with a history consistent with Acute coronary syndrome (ACS) and there's a new onset Left Bundle Branch Block (LBBB) - which is what is seen on the ECG, then a diagnosis of a STEMI is made and the patient is sent for emergency angioplasty.
• 12
  24 hours after an inferior infarct, a patient develops a sudden reduction in the blood pressure and a collapse on the coronary care unit. His heart rate is noted to be 30bpm. His blood pressure is 80/38 and he is very short of breath. What is the best next step in the treatment of this patient ?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Aspirin and Clopidogrel

  b

  Adenosine

  c

  Cardiopulmonary resuscitation

  d

  Transcutaneous pacing

  e

  Transvenous Pacemaker
  Explanation: The patient has developed complete heart block, a recognized complication of myocardial infarction affecting the AV node. Seeing as this patient is haemodynamically unstable, the best INITIAL step would be to pace transcutaneously. The long term solution is a permanent transvenous pacemaker but until then the transcutaneous pacemaker will serve as the initial bridge.
• 13
  A medical student attends the end of year examination. He is asked to interpret the following ECG. The patient has a history of right coronary artery infarction 6 months ago. What does the ECG show?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Dual chamber pacing

  b

  Temporary pacing wire

  c

  NSTEMI

  d

  LBBB

  e

  RBBB
  Explanation: This ECG shows a dual chamber pace maker in action. The pace maker has two leads, one in the atria (sensing) and one in the ventricle (pacing). This is visible with a pacing spike after the p-waves but before the QRS complex. Because the ventricle pacing lead is in the right ventricle, the right ventricle depolarises first, which gives a LBBB pattern on the ECG when there's actually no bundle branch block.
• 14
  While attending the cardiology outpatient clinic, a medical student stumbles across the ECG shown. What is the ECG pattern showing ?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  Acute ST-Elevation MI

  b

  Atrial Pacing

  c

  Atrial Ectopics

  d

  Atrial Sensing

  e

  Ischaemic P-waves
  Explanation: This ECG clearly shows a pacing spike before every P wave, which in turn is inverted. This suggests that the patient has an atrial pacemaker in-situ which is depolarising the atria in the opposite direction to "normal sinus rhythm" but is still able to relate the signal to the AV node. The pacing rate is 60bpm.
• 15
  A 45 year old man attends the GP new patient clinic. His cardiovascular examination is normal except for an irregular rhythm. The concerned GP performs an ECG (shown). The patient is asymptomatic. What is the best course of management?
  
  Difficulty: Medium     Topic: Conduction defects
  a

  Bisoprolol

  b

  Ivabradine

  c

  Permanent Pacemaker

  d

  Temporary pacing wire

  e

  Watch and wait
  Explanation: This ECG shows Second Degree Heart Block (Mobitz type II); that is: a normal PR interval but with dropped QRS complexes and therefore beats. Unlike Mobitz type I, this rhythm may progress into Complete Heart Block and it is therefore best to refer this patient for a transvenous (permanent) pacemaker, even if they were asymptomatic.
• 16
  A 55 year old immigrant attends the GP clinic for a registration check-up. He has his ECG taken (shown). The GP is puzzled by the ECG. The pulse is irregular. The patient is asymptomatic. What is the best course of action?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  Bisoprolol

  b

  Ivabradine

  c

  Permanent Pacemaker

  d

  Temporary pacing wire

  e

  Watch and wait
  Explanation: The ECG is consistent with Second Degree Heart Block (Mobitz type I); otherwise known as Wenckebach phenomenon. The PR interval prolongs from one beat to the next followed by a drop in a QRS complex and therefore a drop in a beat. If these patients are asymptomatic, they are normally managed conservatively.
• 17
  A patient is admitted to the coronary care unit with troponin positive chest pain. His ECG is shown. What is the diagnosis ?
  
  Difficulty: Easy     Topic: Conduction defects
  a

  Sinus rhythm with NSTEMI

  b

  First Degree Heart block with NSTEMI

  c

  Second degree heart block with NSTEMI

  d

  Complete heart block with NSTEMI

  e

  Left bundle branch block
  Explanation: The PR interval is prolonged (>0.20seconds) and the ST segment is depressed (with a positive troponin) suggesting a diagnosis of NSTEMI with first degree heart block, which could be coincidental or secondary to ischaemia.