Data interpretation Flashcards
Consider the following statements regarding this ECG:
The normal speed the paper travels at is 50 mm/s
False. The normal speed for an ECG to travel is 25 mm/s. Therefore 5 large squares (each 5 mm wide) represent 1 second.
Consider the following statements regarding this ECG:
The length of the QRS complex increases with increasing LV muscle mass
False. The amplitude (mV) of the QRS complex increases with LV muscle mass (hypertrophy). Prolongation of the QRS complex indicates a conduction delay (Bundle Branch Block).
Consider the following statements regarding this ECG:
One volt is usually represented by a 10 mm vertical deflection of the ECG
False. 10 mm on the y axis represents 1 mV.
Consider the following statements regarding this ECG:
The QT interval is measured from the start of the QRS complex to the beginning of the T wave
False. The QT Interval is measured from the start of the QRS to the end of the T wave. When considering if it is prolonged it should also be corrected for heart rate.
Consider the following statements regarding this ECG:
The smallest square on an ECG represents 0.2 s
False. The smallest square is 0.04 s, or 40 ms.
Consider the following statements about the ECG:
U waves represent sinoatrial (SA) node repolarization
False. The P wave represents atrial depolarization. The U wave is a small deflection following the T wave, which probably represents repolarization of the papillary muscles and is most commonly seen in hypokalaemia.
Consider the following statements about the ECG:
The T wave represents ventricular repolarization
True
Consider the following statements about the ECG:
The QT interval reflects the duration of the ventricular refractory period
True. The refractory period is divided into the absolute and relative refractory period. During the absolute refractory period another action potential can not be elicited. In the relative refractory period a action potential can be elicited in certain circumstances.
Consider the following statements about the ECG:
The PR interval represents AV nodal conduction delay
True
Consider the following statements about the ECG:
The height of a normal P wave is 0.3 mV
False. The normal P wave is less than 2.5 mm which represents 0.25 mV.
Consider the following statements about the QRS complex:
It is associated with ventricular repolarization
False. The QRS complex is associated with ventricular depolarization. The T wave is associated with ventricular repolarization.
Consider the following statements about the QRS complex:
It is absent in 3rd Degree Heart Block
False. 3rd Degree Heart Block is Complete Heart Block, where there is complete dissociation between atrial and ventricular depolarization.
Consider the following statements about the QRS complex:
It is normally longer that 200 ms
False. The normal QRS duration is less than 0.12 s (3 small squares). Greater than this indicates presence of a bundle branch block.
Consider the following statements about the QRS complex:
It is associated with isovolumetric ventricular relaxation
False. The QRS occurs just prior to isovolumetric contraction as ventricular contraction follows ventricular depolarization.
Consider the following statements about the QRS complex:
It is prolonged in conduction defects such as Bundle Branch Blocks
True. The normal QRS duration is less than 0.12 s (3 small squares). Greater than this indicates presence of a Bundle Branch Block.
Now, consider the following statements about using ECG monitoring intraoperatively:
In a patient with a permanent pacemaker an alternative method to the ECG for measuring heart rate should be employed (e.g. pulse oximeter)
True. A patient with a pacemaker is at risk of Pulseless Electrical Activity (PEA) which would not be detected unless an alternative method of measuring heart rate is employed.
Now, consider the following statements about using ECG monitoring intraoperatively:
The electrodes consist of silver and silver chloride
True
Now, consider the following statements about using ECG monitoring intraoperatively:
CM5 is more sensitive at detecting arrhythmias
False. CM5 is more sensitive at detecting ventricular ischaemia.
Now, consider the following statements about using ECG monitoring intraoperatively:
When utilising CM5 monitoring, electrodes are placed on the manubrium, clavicle and at the V5 position
True. C = Clavicle, M = Manubrium, 5 = V5.
Now, consider the following statements about using ECG monitoring intraoperatively:
Diathermy is frequently a problem causing interference
True. Diathermy will cause interference with ECG monitoring.
Consider the following statements about QT prolongation:
It is seen in patients with hypercalcaemia
False. This is seen in patients with hypocalcaemia. Hypercalcaemia shortens the QT interval.
Consider the following statements about QT prolongation:
It can seen in patients receiving penicillin
False. It is associated with macrolide antibiotics. It is also associated with Class III antiarrhythmics (e.g. amiodarone), anti-histamines and tricyclic antidepressants.
Consider the following statements about QT prolongation:
It is seen in patients with Romano-Ward syndrome
True. Romano Ward syndrome is an example of hereditary prolonged QT syndrome.
Consider the following statements about QT prolongation:
It predisposes patients to Torsade-de-pointes
True. Torsade-de-pointes is a form of Ventricular Tachycardia with a changing axis. It can present as syncope, or deteriorate into VF and sudden death. Treatment is as per ALS algorithm, with the addition of intravenous magnesium.
Consider the following statements about QT prolongation:
It is seen in patients with hypomagnesaemia
True. Also in patients with hypokalaemia. In both cases more likely in patients with heart failure.
Which of the following is considered an indication for pacemaker insertion?
1st Degree Heart Block
False. This is indicated on the ECG by prolongation of the PR interval. It represents an increased delay of conduction at the AVN.
Which of the following is considered an indication for pacemaker insertion?
2nd Degree Heart Block with fixed 2:1 conduction in a patient who is complaining of pre-syncopal episodes
True. This is Mobitz Type 2 2nd Degree Heart Block. In essence every other P wave (atrial contraction) is transmitted to the ventricles. It carries the risk of progressing to a higher degree block such as complete heart block and as this patient is describing significant symptoms it would be reasonable to consider pacemaker insertion.
Which of the following is considered an indication for pacemaker insertion?
RBBB with LAD and PR interval prolongation on a preoperative ECG
True. These finding on an ECG represent trifasicular block, there is a conduction delay at the AVN, the right bundle and the left anterior hemifascicle. This represents widespread disease of the cardiac conduction system and this patient is at risk of ventricular asystole.
Which of the following is considered an indication for pacemaker insertion?
Complete Heart Block
True. This represents complete dissociation of the conduction in the atria and the ventricles. The patients symptoms will depend on the rate of the escape rhythm that has developed. In general the higher up the conducting system the origin of the escape pacemaker the faster the rate.
Which of the following is considered an indication for pacemaker insertion?
Mobitz Type 1 2nd Degree Heart Block
False. This is Wenckebach. It can be a normal finding and is not usually associated with deterioration to higher degree conduction defects and is therefore not an indication for pacemaker insertion.
Which rhythms may be an indication for insertion of a permanent pacemaker?
1st degree heart block
False
Which rhythms may be an indication for insertion of a permanent pacemaker?
2nd degree heart block–type 1
False
Which rhythms may be an indication for insertion of a permanent pacemaker?
3rd degree heart block
True. 3rd degree heart block is also known as Complete Heart Block. There is a risk of asystole or decreased cardiac output from the bradycardia.
Which rhythms may be an indication for insertion of a permanent pacemaker?
Left bundle branch block
False. Although severe left ventricular failure with wide left bundle branch block may be an indication for Cardiac Resynchronization and Biventricular pacing.
Which rhythms may be an indication for insertion of a permanent pacemaker?
Trifasicular block
True. A patient with this rhythm is at risk of progressive worsening heart block and already has widespread disease of their conduction system.
The following ECG changes are manifestations of coronary ischaemia.
Q waves found in leads II, III and aVF
True. Q waves represent an old full thickness infarct. The changes in Leads II, III and aVF indicate that it is in the inferior surface of the heart, normally supplied by the right coronary artery.
The following ECG changes are manifestations of coronary ischaemia.
Saddle shaped ST elevation
False. This is typical of pericarditis.
The following ECG changes are manifestations of coronary ischaemia.
Decreased QTc
False
The following ECG changes are manifestations of coronary ischaemia.
Widespread T wave inversion
True. Widespread T wave inversion may be a sign of global cardiac ischaemia or a subendocardial infarct. The more proximal the lesion (e.g. left main stem) the wider spread the ECG changes will be i.e. the more leads they will be demonstrated in.
The following ECG changes are manifestations of coronary ischaemia.
ST depression
True. This is the classical finding in reversible ischaemia seen with angina and demonstrated in a positive exercise tolerance test used to risk stratify patients presenting with chest pain.
Hyperkalaemia is associated with:
Flattening of the P waves on the ECG
True. Flattened or absent P waves is one of the findings in hyperkalaemia.
Hyperkalaemia is associated with:
A history of administration of an ACE inhibitor
True. History of administration of an ACE inhibitor is often contributive to renal failure in critically ill patients and in patients with renal artery stenosis may be a direct cause of acute kidney injury.
Hyperkalaemia is associated with:
Similar ECG changes to hypomagnesaemia
False. The ECG findings are more similar to those found with hypermagnesaemia.
Hyperkalaemia is associated with:
Widened QRS complexes seen on the ECG
True. This is a sign of severe hyperkalaemia, eventually the QRS becomes so widened that the ECG trace looks sinusoidal.
Hyperkalaemia is associated with:
Tall U waves in the ECG
False. Prominent U waves are seen in hypokalaemia.
The presence of the following would make you consider a broad complex tachycardia was more likely to be ventricular in origin (VT) rather than an SVT with RBBB.
A capture beat
True. This indicates independent atrial and ventricular activity and that the coincidental timing of the P wave at the AV Node ‘captured’ the conduction system for a beat producing a narrow complex amongst the broad QRS complexes.
The presence of the following would make you consider a broad complex tachycardia was more likely to be ventricular in origin (VT) rather than an SVT with RBBB.
A 30-year-old patient
False. Ventricular tachycardia has increasing incidence with age.
The presence of the following would make you consider a broad complex tachycardia was more likely to be ventricular in origin (VT) rather than an SVT with RBBB.
A pre-existing history of IHD
True. Myocardial ischaemia or myocardial scarring from previous infarcts predispose to ventricular tachycardia.
The presence of the following would make you consider a broad complex tachycardia was more likely to be ventricular in origin (VT) rather than an SVT with RBBB.
Visible J waves
False. J waves are seen in hypothermia.
The presence of the following would make you consider a broad complex tachycardia was more likely to be ventricular in origin (VT) rather than an SVT with RBBB.
A normal preoperative ECG
True. If there is a normal preoperative ECG then there is no evidence of a pre-existing bundle branch block.
Which of the following commonly causes atrial fibrillation.
Dehydration
True. Intravascular depletion, electrolyte disturbances and sepsis are common causes of atrial fibrillation (AF) in the acutely unwell patient.
Which of the following commonly causes atrial fibrillation.
Thyrotoxicosis
True
Which of the following commonly causes atrial fibrillation.
Mitral valve disease
True. Both the atrial pressure overload of mitral stenosis and the atrial volume overload of mitral regurgitation cause AF.
Which of the following commonly causes atrial fibrillation.
Hypertension
True
Which of the following commonly causes atrial fibrillation.
Digoxin
False. Digoxin is a treatment for AF. When compared to alternative treatments (Beta-blockers/Amiodarone) it is less likely to aid return to sinus rhythm. In general all anti-arrhythmics have the potential to cause arrhythmias.
The following ECG changes may occur in a patient with severe mitral stenosis.
P pulmonale
False. P pulmonale (right atrial hypertrophy), is found with causes of high right sided heart pressures. E.g. tricuspid stenosis or chronic lung disease.
The following ECG changes may occur in a patient with severe mitral stenosis.
Right Axis Deviation
True. If the mitral stenosis is severe and longstanding it may lead to pulmonary hypertension, right ventricular hypertrophy and therefore, right axis deviation.
The following ECG changes may occur in a patient with severe mitral stenosis.
An increased P wave duration and height
True. This describes the findings of P mitrale (left atrial hypertrophy). Mitral Stenosis causes increased left atrial pressures and leads to the hypertrophy, this also predisposes to AF.
The following ECG changes may occur in a patient with severe mitral stenosis.
Absence of P waves
True. This is AF
The following ECG changes may occur in a patient with severe mitral stenosis.
Left ventricular hypertrophy
False. Left ventricular hypertrophy is seen in response to raised afterload to left ventricular ejection, most commonly seen in hypertension or aortic stenosis.
