QuestionSBA
QuestionChoice
Incorrect, this is used to visualise the structure of the heart and lungs. As it is a static image taken at one moment in time, it cannot measure cardiac output.
10007088
c
Chest x-ray
QuestionChoice
Transoesophageal doppler involves a flexible ultrasound probe that is inserted into the oesophagus. Whilst this can accurately measure cardiac output, it is more invasive and so would be tried after doppler ultrasound.
10007089
d
Transoesophageal doppler
QuestionChoice
CT can be used to visualise the structure of the heart and lungs. As it is a static image taken at one moment in time, it cannot measure cardiac output.
10007090
e
CT thorax
QuestionChoice
Incorrect, this is used to measure the electrical signals from the heart. It is useful in detecting cardiac ischaemia, however cannot measure cardiac output.
10007087
b
Electrocardiography
QuestionChoice
This method uses ultrasound and the doppler effect. Blood velocity through the first part of the aorta causes a doppler shift in the frequency of returning ultrasound waves. This shift can be used to calculate flow velocity. The cross-sectional area of the tract can be measured by ultrasound, thus obtaining cardiac output (heart rate x stroke volume).
10007086
a
Doppler ultrasound
Concept
Chapter
2693
4218
Cardiac Volumes and Arterial Pressure
Topic
159
Cardiovascular physiology
13964
A 32-year-old woman is being investigated for recurrent syncope. As part of a full workup, the doctor wants to measure her cardiac output.

Which of the following investigations is most suitable initial method for measuring cardiac output?
a