Each one of the following is associated with right axis deviation on ECG, except:
Correct Answer C: Wolff-Parkinson-White syndrome is associated with a short PR interval and a wide QRS complex with a slurred upstroke, termed a delta wave. Axis deviation depends on the position of the accessory pathway.
Causes of left axis deviation (LAD):
Causes of right axis deviation (RAD):
*in the majority of cases, or in a question without qualification, Wolff-Parkinson-White syndrome is associated with left axis deviation
A 28-year-old intravenous drug user is brought into the Emergency Department as a stand-by call following a cardiac arrest. He has been using methadone for the past 3 months. Unfortunately attempts to resuscitate him fail.
Which one of following underlying problems is most likely to have caused his sudden death?
Correct Answer A: Methadone is a common cause of QT prolongation.
Long QT syndrome: Long QT syndrome (LQTS) is an inherited condition associated with delayed repolarization of the ventricles. It is important to recognize as it may lead to ventricular tachycardia and can therefore cause collapse/sudden death.
The most common variants of LQTS (LQT1 & LQT2) are caused by defects in the alpha subunit of the slow delayed rectifier potassium channel. A normal corrected QT interval is less than 430 ms in males and 450 ms in females.
Causes of a prolonged QT interval:
Features:
Management:
*the usual mechanism by which drugs prolong the QT interval is blockage of potassium channels. See the link for more details
**a non-sedating antihistamine and classic cause of prolonged QT in a patient, especially if also taking P450 enzyme inhibitor, e.g. Patient with a cold takes terfenadine and erythromycin at the same time
***note sotalol may exacerbate long QT syndrome
A 60-year-old man is transferred from the local psychiatric unit to the Emergency Department. Throughout the day he has complained of palpitations and feeling light-headed. The psychiatry consultant noted he was tachycardic and requested a transfer. An ECG taken following admission shows a broad complex tachycardia consistent with torsades de pointes, rate 120/min. His blood pressure is 122/80 mmHg and there are no signs of heart failure.
What is the most appropriate management?
Correct Answer B: Torsades de pointes ('twisting of the points') is a rare arrhythmia associated with a long QT interval. It may deteriorate into ventricular fibrillation and hence lead to sudden death.
Causes of long QT interval:
A 50-year-old man is admitted to Resus with a suspected anterior myocardial infarction. An ECG on arrival confirms the diagnosis and thrombolysis is prepared. The patient is stable and his pain is well controlled with intravenous morphine. Clinical examination shows a blood pressure of 140/84 mmHg, pulse 90 bpm and oxygen saturations on room air of 97%.
What is the most appropriate management with regards to oxygen therapy?
Correct Answer B: NICE produced guidelines in 2010 on the management of unstable angina and non-ST elevation myocardial infarction (NSTEMI). They advocate managing patients based on the early risk assessment using a recognized scoring system such as GRACE (Global Registry of Acute Cardiac Events) to calculate a predicted 6 month mortality.
Acute coronary syndrome management: All patients should receive:
Whilst it is common that non-hypoxic patients receive oxygen therapy there is little evidence to support this approach. The 2008 British Thoracic Society oxygen therapy guidelines advise not giving oxygen unless the patient is hypoxic.
Antithrombin treatment. Fondaparinux should be offered to patients who are not at a high risk of bleeding and who are not having angiography within the next 24 hours. If angiography is likely within 24 hours or a patients creatinine is > 265 μmol/l unfractionated heparin should be given.
Clopidogrel 300mg should be given to patients with a predicted 6 month mortality of more than 1.5% or patients who may undergo percutaneous coronary intervention within 24 hours of admission to hospital. Clopidogrel should be continued for 12 months.
Intravenous glycoprotein IIb/IIIa receptor antagonists (eptifibatide or tirofiban) should be given to patients who have an intermediate or higher risk of adverse cardiovascular events (predicted 6- month mortality above 3.0%), and who are scheduled to undergo angiography within 96 hours of hospital admission.
Coronary angiography should be considered within 96 hours of first admission to hospital to patients who have a predicted 6-month mortality above 3.0%. It should also be performed as soon as possible in patients who are clinically unstable.
The table below summaries the mechanism of action of drugs commonly used in the management of acute coronary syndrome:
A 60-year-old man is admitted with palpitations to the Emergency Department. An ECG on admission shows a broad complex tachycardia at a rate of 150 bpm. His blood pressure is 124/82 mmHg and there is no evidence of heart failure.
Which one of the following is it least appropriate to give?
Correct Answer E: Ventricular tachycardia -> verapamil is contraindicated
Verapamil should never be given to a patient with a broad complex tachycardia as it may precipitate ventricular fibrillation in patients with ventricular tachycardia. Adenosine is sometimes given in this situation as a 'trial' if there is a strong suspicion the underlying rhythm is a supraventricular tachycardia with aberrant conduction.
Ventricular tachycardia management:
Whilst a broad complex tachycardia may result from a supraventricular rhythm with aberrant conduction, the European Resuscitation Council advise that in a peri-arrest situation it is assumed to be ventricular in origin.
If the patient has adverse signs (systolic BP < 90 mmHg, chest pain, heart failure or rate > 150 beats/min) then immediate cardioversion is indicated. In the absence of such signs antiarrhythmics may be used. If these fail, then electrical cardioversion may be needed with synchronized DC shocks.
Drug therapy:
Verapamil should NOT be used in VT
If drug therapy fails:
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