Cardiology

Question 1

why is the cardiac axis deviated in newborns

Answer 1

marked right ventricular hypertrophy, as the right ventricle pumps blood against a high-resistance collapsed lung in utero.

Question 2

Normal HR, BP (systolic), RR in babies <1 year

Answer 2

HR- 110-160 BP- 80-90mmHg RR- 30-40

Question 3

Normal HR, BP (systolic), RR in 2-5 year olds

Answer 3

HR- 95-140 BP- 85-100mmHg RR- 25-30

Question 4

Normal HR, BP (systolic), RR in 5-12 year olds

Answer 4

HR- 80-120 BP- 90-110mmHg RR- 20-25

Question 5

Normal HR, BP (systolic), RR in 12-18 year olds

Answer 5

HR- 60-100 BP- 90-120mmHg RR- 15-20

Question 6

corrected QT <6 months

Answer 6

<0.49s

Question 7

corrected QT >6 months

Answer 7

<0.44s

Question 8

How to correct for axis deviation in the newborn

Answer 8

The right ventricle is captured by placing an additional lead (V4R) in the fifth intercostal space, at the mid clavicular line on the right. V1 (looking directly at the right ventricle) and V2-V3 often have a dominant R wave.

Question 9

Why do babies have sinus arrhythmia

Answer 9

because the heart rate varies dramatically with breathing.

Question 10

give some abnormal ECG features that are normal in paediactric ECGs

Answer 10

• Normal heart rate is much higher.
• Normal marked sinus arrhythmia.
• Cardiac axis is deviated to the right in the newborn. T
• ​Possible partial right bundle branch block. This manifests as a normal QRS complex, plus an RSR pattern (M shape) in V1.
• T wave inversion. This is normal in leads V1-3 and potentially V4 as well.
• Q waves. These are normal in the inferior (AVF, II, II) and left precordial leads (V5-6).

Question 11

Give some reasons for tachycardia in a paed

Answer 11

• Physiological
  
  • excessive activity
  • crying/being upset
  • pain
  • stress
• Pathological
  
  • fever
  • infection
  • hyperthyroid
  • anaemia

It’s very rarely a cardiac cause. Primary tachycardia is more likely if an isolated finding, or particularly high and the child is well

Question 12

causes of paediactric bradycardia

Answer 12

• Athletes
• sleep
• drugs e.g. beta blockers
• cushing reflex- The combination of bradycardia, hypertension, reduced consciousness and irregular respiration is a sign of raised intracranial pressure.
• shock/sepsis
• heart block

Question 13

what is SVT?

Answer 13

narrow complex tachycardia originating at or above the atrioventricular node. It is the most common tachyarrhythmia encountered by paediatricians and can be difficult to differentiate from a simple sinus tachycardia.

Question 14

Causes of paeds SVT

Answer 14

A re-entry mechanism is the most common cause of an SVT, and this can occur anywhere along the atrioventricular junction. This mechanism results in rapid acceleration of the heart rate, as it does not rely on a new impulse to be generated by the sino-atrial node.

An example of this is the Bundle of Kent in Wolff-Parkinson-White syndrome.

Question 15

Presentation of Paeds SVT

Answer 15

Question 16

Investigations in SVT

Answer 16

• ECG. This is the primary diagnostic test. The ECG will show narrow complex tachycardia. The rate will generally be above 220 bpm for an infant and above 180 bpm for an older child. There will be no discernible P-waves and there will be no rate variability.
• ​Chest X-ray. This investigation can serve as a useful indicator of heart failure as it may show plethoric lungs. It can also help to exclude pulmonary causes of shortness of breath (e.g. consolidation, pneumothorax, pleural effusion).
• Blood gas. This is a good investigation to do for an unwell child, as it can indicate how systemically compromised they are with lactate levels, carbon dioxide and base excess. Electrolyte levels, including potassium and calcium, are often available from the blood gas machine.
• Blood glucose. It is very important to check this value in any unwell child, as hyper- or hypoglycaemia can cause or worsen many presentations.
• Haematology and biochemistry tests. These are useful in determining the underlying health of the patient and the effect their condition is having on the rest of their body. Anaemia, infection or dehydration may exacerbate a tachycardia. Imbalances of electrolytes (e.g. potassium, magnesium, calcium) or thyroid dysfunction may also trigger an arrhythmia. Magnesium levels have to be specifically requested as they are not part of a normal electrolyte work up.
• ​Echocardiogram. This is used to identify any underlying structural cardiac abnormalities.

Question 17

How to differentiate SVT from sinus tachycardia

Answer 17

• Sudden onset.
• No rate variation.
• Very fast rate (>220 bpm in an infant and >180 bpm in a child)
• Not responsive to a fluid bolus
• No P waves visualised on the ECG reading

Question 18

Management of stable SVT in a child

Answer 18

• Can try vagal manouvers if cooperative
• In children, a Valsalva manoeuvre can be attempted. One way of getting children to successfully comply with this is by asking them to blow into an empty 10 mL syringe.
• The child must be attached to a heart monitor/ECG so that cardioversion can be captured and sent to the local tertiary unit.
• In infants, ice immersion can be attempted. This involves wrapping the infant and immersing its face into a basin of ice for approximately 10 seconds. This stimulates the diving reflex and can trigger the heart rate to return to normal.
  
  • A variation of this is placing a bag containing crushed ice onto an infant’s face for 15–30 seconds.

Question 19

Management of unstable SVT in a paed

Answer 19

In patients that are more acutely compromised or in those in whom initial vagal manoeuvres don’t work, adenosine may be given or DC cardioversion may be needed.

Question 20

complications of SVT

Answer 20

In the acute setting, SVT can lead to cardiovascular compromise, insufficient cardiac output, shock and ultimately death. Treatment also has complications. Vagal manoeuvres and adenosine can lead to asystole and should be done under careful monitoring, with full resuscitation facilities available. Following resolution of SVT, further ECG abnormalities may be detected. An example of this would be Wolff-Parkinson-White syndrome. This is characterised by a slurred R wave, known as a delta wave, across all leads. The delta wave is caused by an accessory conduction system which bypasses the AV node, thereby shortening the PR interval and making the patient prone to episodes of re-entry tachycardia.

Question 21

SVT prognosis

Answer 21

In general, patients that have a single episode of SVT have a good prognosis, particularly with an uncomplicated presentation. SVT episodes may be recurrent. In the long-term, particularly if a patient has frequent episodes, prophylactic measures should be considered under the advice of a paediatric cardiologist. This would initially involve advice with regard to vagal manoeuvres and when to summon help. The patient may also be commenced on anti-arrhythmic medication. Those on longer term medications may suffer side effects, although SVTs can generally be well controlled, and medications are stopped after having an ablation. Patients may undergo radiofrequency ablation of their accessory pathway when they are teenagers, which renders that pathway nonfunctional.