Question 121#

A 47-year-old man is admitted to hospital following an acute coronary syndrome. He has a history peptic ulcer disease and his cardiologist decides to use clopidogrel.

What is the mechanism of action of clopidogrel?

A. Non-selective phosphodiesterase inhibitor

Correct Answer D:

Clopidogrel inhibits ADP binding to platelet receptors.

Clopidogrel:

Clopidogrel is an antiplatelet agent used in the management of cardiovascular disease. It was previously used when aspirin was not tolerated or contraindicated but there are now a number of conditions for which clopidogrel is used in addition to aspirin, for example in patients with an acute coronary syndrome. Following the 2010 NICE technology appraisal clopidogrel is also now first-line in patients following an ischaemic stroke and in patients with peripheral arterial disease. 

Mechanism:

• Inhibits ADP binding to its platelet receptor

Interactions:

• Concurrent use of proton pump inhibitors (PPIs) may make clopidogrel less effective (MHRA July 2009)
• This advice was updated by the MHRA in April 2010, evidence seems inconsistent but omeprazole and esomeprazole still cause for concern. Other PPIs such as lansoprazole should be OK

Question 122#

A 72-year-old man presents to the Emergency Department with a broad complex tachycardia.

Which of the following features would make it more likely that this was due to a supraventricular tachycardia rather than a ventricular tachycardia?

A. History of ischaemic heart disease

Correct Answer D:

Positive QRS concordance in the chest leads is associated with ventricular tachycardia.

Broad complex tachycardia:

Features suggesting VT rather than SVT with aberrant conduction:

• AV dissociation
• Fusion or capture beats
• Positive QRS concordance in chest leads
• Marked left axis deviation
• History of IHD
• Lack of response to adenosine or carotid sinus massage
• QRS > 160 ms

Question 123#

A 66-year-old man presents with shortness-of-breath on exertion. On examination his blood pressure is 128/76 mmHg, pulse 78 / min and regular. Auscultation of his chest reveals an early diastolic murmur.

Which one of the following conditions is most associated with this kind of murmur?

A. Atrial septal defect

Correct Answer D:

Murmurs:

Ejection systolic:

• Aortic stenosis
• Pulmonary stenosis, HOCM
• ASD, Fallot's

Pan-systolic:

• Mitral regurgitation
• Tricuspid regurgitation
• VSD

Late systolic:

• Mitral valve prolapse
• Coarctation of aorta

Early diastolic:

• Aortic regurgitation
• Graham-Steel murmur (pulmonary regurgitation) 

Mid diastolic:

• Mitral stenosis
• Austin-Flint murmur (severe aortic regurgitation) 

Question 124#

A 76-year-old woman is admitted with palpitations. During the cardiovascular examination you notice irregular cannon 'a' waves.

Which one of the following would account for this finding?

A. Atrio-ventricular nodal re-entry tachycardia

Correct Answer D:

JVP: cannon waves:

Caused by the right atrium contracting against a closed tricuspid valve. May be subdivided into regular or intermittent.

Regular cannon waves:

• Ventricular tachycardia (with 1:1 ventricular-atrial conduction)
• Atrio-ventricular nodal re-entry tachycardia (AVNRT)  

Irregular cannon waves:

• Complete heart block

Question 125#

A 57-year-old man presents to the Emergency Department with a 15 minute history of severe central chest pain radiating to his left arm. ECG shows T-wave inversion in leads I, V5 and V6.

Which coronary artery is most likely to be affected?

A. Left circumflex

Correct Answer A:

This is most typical of a left circumflex occlusion although may rarely be seen if the left anterior descending is affected.

ECG: coronary territories:

The table below shows the correlation between ECG changes and coronary territories: