The Electrocardiogram and Arrhythmias Flashcards
Regarding abnormalities of the cardiac pacemaker (true or false):
Sinus tachycardia is a normal physiological phenomenon
True. Sinus tachycardia is a physiological response to sympathetic stimulation of the sinus node. It can occur due to exercise, emotional distress, fever or illness.
Regarding abnormalities of the cardiac pacemaker (true or false):
Wolff-Parkinson-White syndrome is known as an atrioventricular nodal re-entrant tachycardia
False. It is an AV re-entrant tachycardia, because the accessory bundle, known as the bunlde of Kent, is structurally separate from the AV node. A Type A accessory pathway connects the left atrium and ventricle, whereas a Type B connects the right atrium and ventricle.
Regarding abnormalities of the cardiac pacemaker (true or false):
The PR interval is short in WPW due to increased speed of conduction of depolarization through the accessory bundle of Kent
False. The short PR interval is not due to increased speed of conduction through the bundle of Kent, but rather due to the lack of intrinsic inhibition of impulse conduction provided by the AV node.
Regarding abnormalities of the cardiac pacemaker (true or false):
Depolarization in AV re-entrant tachycardia can occur from atria to ventricle via the accessory bundle and ventricle to atria via the AV node and vice versa
True. If the impulse passes through AV node first, depolarizing the ventricles normally and passing retrogradely through the accessory pathway, it is known as Orthodromic flow. If the impulse passes through the accessory pathway first, the retrograde flow through the AVN is known as Antidromic flow.
Regarding abnormalities of the cardiac pacemaker (true or false):
Re-entrant circuits contained within the atria cause atrial tachycardia
True. Atrial fibrillation is caused by re-entrant circuits or ‘wavelets’ of depolarization, which do not originate in the SAN, but in ectopic areas of myocardium, commonly around the pulmonary veins in the left atrium.
Regarding the ECG trace (true or false):
A right bundle branch block is characterised by a broad QRS (>0.12 seconds or 3 mm on the ECG) with a large initial negative deflection in lead V1 (describes as QS) or a small initial positive followed by a large negative deflection (described as a rS complex)
False. This describes a left bundle branch block pattern. In RBBB, the normal depolarization of the LV means that the early part of the QRS complex appears normal, but the later part of the QRS is abnormal.
Regarding the ECG trace (true or false):
Ventricular fibrillation is characterised by the presence of fusion and capture beats on the ECG
False. In VF there is uncoordinated electrical activity with no discernible QRS complexes.
Regarding the ECG trace (true or false):
Polymorphic VT describes beat-to-beat variability in the shape or axis of the QRS complexes
True. Polymorphic VT results from multiple ventricular foci of impulses so each QRS can have different axis, duration and amplitude. It is often a consequence of myocardial ischaemia.
Regarding the ECG trace (true or false):
Wide QRS complexes are always ventricular in origin
False. A wide QRS can originate in the atria, but be widened by aberrant conduction below the AV node, e.g. a bundle branch block.
Regarding the ECG trace (true or false):
Narrow QRS complexes with an increasing PR interval followed by a dropped beat is usually a benign phenomenon which does not require treatment
True. This is second-degree heart block, Mobitz Type 1 or Wenckebach, and is usually caused by suppression of electrical transmission at the AV node itself. It rarely causes haemodynamic compromise and can be a normal variant or secondary to myocardial infarction or a drug side effect.
Regarding artificial pacemakers (true or false):
In the international pacemaker code, AAI describes a pacemaker which paces the atria, senses the atria and is inhibited when it senses an endogenous beat
True. Such a pacemaker may be inserted for sinus node disease such as sick sinus syndrome.
Regarding artificial pacemakers (true or false):
Dual chamber pacing means both the right and left ventricles are paced
False. Dual chamber pacing means that both the right atrium and right ventricle have pacing leads.
Regarding artificial pacemakers (true or false):
Pacing wires deliver the energy to the left atrium and ventricle due the greater muscle mass
False. Transvenous pacing leads are inserted fluroscopically via a central vein and therefore to the right side of the heart, where they are in contact with the endocardium of the right atrium and/or ventricle.
Regarding artificial pacemakers (true or false):
VOO mode is a safe mode for surgery
True. This asynchronous mode paces the ventricle at a fixed rate without sensing either chamber. There is no interference to sensing from diathermy, which could be interpreted by the pacemaker as an innate electrical impulse, and which could result in inappropriate inhibit pacing.
