Answers for Medical Finals Quiz - March 2007

Below are the authors' answers and teaching points for this Quiz.

Question 1

A 75 year old gentleman is admitted via ambulance to A & E. He gives a 4 hour history of vague upper abdominal discomfort. There is no radiation. He also complains of feeling dizzy.

Relevant past medical history includes: an abdominal aortic aneurysm repair/stenting performed 3 months previously via percutaneous technique. He tells you he was admitted 2 weeks ago for 2 days of observation as follow up ultrasound scan had revealed a small leak at the site of repair. He has never been treated for ischaemic heart disease.

On examination he is fully conscious and alert. Heart rate is 70bpm regular and BP is 110/68. Heart sounds one and two are present and normal in character. There are no additional heart sounds or murmurs. Auscultation of the chest is clear. His left femoral pulse is very difficult to palpate.

You perform an ECG:

ECG 1
ECG image from: ecglibrary.com

What is the diagnosis?

(a) Acute Anteroseptal Myocardial Infarction
(b) Complete heart block
(c) Acute pericarditis
(d) Infero-posterior myocardial infarction
(e) Acute Inferior myocardial infarction
Answer: (d) Infero-posterior myocardial infarction

The ECG is in sinus rhythm. There is ST segment elevation in the inferior leads (II, III and aVF), with marked reciprocal ST segment depression in leads V2 and V3.

Question 2

What is your initial management of the above patient?
(a) Aspirin 300mg, clopidrogrel 300mg, reteplase, enoxaparin 60mg, metoprolol 5mg IV
(b) Aspirin 75mg, clopidrogrel 75mg, reteplase, enoxaparin 60mg, metoprolol 5mg IV
(c) Aspirin 300mg, clopidrogrel 300mg, enoxaparin 60mg, metoprolol 5mg IV, transfer for primary angioplasty and stenting
(d) Aspirin 300mg, clopidrogrel 300mg, reteplase, enoxaparin 100mg, metoprolol 5mg IV
(e) Aspirin 300mg, reteplase, enoxaparin 60mg, metoprolol 25mg PO
Answer: (c) Aspirin 300mg, clopidrogrel 300mg, enoxaparin 60mg, metoprolol 5mg IV, transfer for primary angioplasty and stenting

The patient has recently had a major vascular procedure performed, and therefore thrombolysis with reteplase is contra-indicated. The patient should be transferred to the cardiac catheterization laboratory for primary angioplasty.

Question 3

Which coronary artery do you think is affected in the above patient?
(a) The left anterior descending artery (LAD)
(b) The circumflex artery (Cx)
(c) The right coronary artery (RCA)
(d) Left main stem
(e) The LAD and RCA together
Answer: (c) The right coronary artery (RCA)

This is usually the culprit artery in infarcts of this type.

Question 4

During transfer to the ward he suddenly loses consciousness. You immediately note the ECG defibrillator/monitor rhythm has changed. (see below)

ECG 2
ECG image from: images.emedicinehealth.com

What is your immediate treatment?

(a) Further bolus of reteplase
(b) Commence immediate CPR at a rate of 15:2
(c) Commence immediate CPR at a rate of 30:2
(d) Administer 200 J DC biphasic shock
(e) Administer 360 J DC biphasic shock
Answer: (d) Administer 200 J DC biphasic shock

The rhythm strip shows ventricular fibrillation (VF). The most effective treatment for this is a DC shock. The most recent advanced life support guidelines (Resuscitation Council UK) would suggest that a 150-200 J shock from a biphasic defibrillator would be most appropriate.

Quoting from section 5 of the current (2005) in-hospital resuscitation guidelines:

"5. If the patient has a monitored and witnessed cardiac arrest:
  • Confirm cardiac arrest and shout for help.
  • If a defibrillator is not immediately to hand consider giving a single precordial thump immediately after confirmation of VF/VT cardiac arrest. The precordial thump should be given only by healthcare professionals trained in the technique.
  • If the initial rhythm is VF/VT and a defibrillator is immediately available, give a shock first. [Italics added]
  • Start CPR immediately after the shock is delivered as described above.
  • Continue resuscitation in accordance with the ALS algorithm (see adult ALS section)."

As this patient is already connected to a defibrillator/monitor, giving an immediate shock is best option.

(Note: CPR at 15:2 is for Pediatrics, whereas 30:2 is used for adults.)

Question 5

Your treatment is successful and he regains consciousness. He is treated in the cardiology department, makes a successful recovery and is discharged. He returns 6 months later complaining of syncope. His ECG has changed again. (see below)

ECG 3
ECG image from: sprojects.mmi.mcgill.ca

What is the diagnosis?

(a) Complete heart block
(b) Left bundle branch block
(c) Old infero-posterior infarct, and trifasciular block
(d) Acute posterior infarct
(e) 2nd degree heart block
Answer: (c) Old infero-posterior infarct, and trifascicular block

The presence of Q waves in the inferior leads with small R waves, and the presence of a dominant R wave in V1 suggests an old infero-posterior myocardial infarction. The presence of right bundle branch block, left axis deviation and first degree atrio-ventricular block indicates tri-fascicular block.

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