Understanding cardiovascular diseases
Understanding cardiovascular diseases

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Understanding cardiovascular diseases

11 Additional resources

Bandolier (2005) Statins: when should you take the tablet?

British Red Cross (2007) First aid guidelines in the UK

Cardiac Risk in the Young (2003) When a young person dies suddenly

Clay, R. A. (2001) Research to the heart of the matter

Department of Health (2000) National Service Framework for coronary heart disease, Chapter 4

Department of Health (2007) The coronary heart disease National Service Framework: shaping the future: progress report 2006

The National Assembly for Wales (2001) Tackling coronary heart disease in Wales: implementing through evidence

National Center for Biotechnology Information (2007) PubMed

National Institute for Health and Clinical Excellence (2007) Hypertension: management of hypertension in adults in primary care

World Health Organization (2006) World data tables

Please note that there is an error in Column 1 of the table. The population figure is actually in thousands and not in the millions as stated. So, for example, Afghanistan has a population of 23 million, rather than 23 billion.

Video resource

An ultrasound investigation of the heart

Now watch a video following an unltrasound investigation of the heart.

Download this video clip.Video player: Click to view clip about ultrasound [5 minutes 24 seconds]
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Transcript: Click to view clip about ultrasound [5 minutes 24 seconds]

NARRATOR
This patient has been sent by his GP for an ultrasound investigation of the heart. 
Ultrasound has a number of key advantages; it is quick, cost effective, and has virtually no associated hazards. It is also far more acceptable to many patients than some other modalities.
ECG electrodes are attached to the patient to record the electrical signals from the heart. This allows the ultrasound images to be linked to the heart cycle.
Because even a thin layer of air will reflect the ultrasound signal, a coupling gel is used between the ultrasound transducer and the patient.
Ultrasound is useful for rapid and reliable cardiac investigations, particularly as it is the only technique that can provide information about blood flow. However, as ultrasound doesn’t penetrate bone, the transducer has to be shaped so that the ultrasound beam will pass between the ribs. The transducer being used in this examination is a wide band transducer that transmits ultrasound at 1.75 MHz, a low enough frequency for good penetration of the heart. The images are formed by detecting the reflected second harmonic at 3.5 MHz. This gives a good compromise between spatial resolution and sensitivity.
Paul has produced a parasternal view of the heart. First a standard B mode image. Now he has chosen a direction from the B mode image to look at in M mode. This allows the position of different parts of the heart to be plotted against time.
By moving into colour Doppler mode, the blood flow through the heart can be visualized. Ultrasound reflected by blood flowing away from the transducer returns with a slightly lower frequency and shows up blue on the images. Conversely blood flowing towards the transducer is shown in red.
Moving to the apex of the heart Paul uses a different Doppler technique. The frequency shift depends on the blood flow velocity, so a plot of frequency shift against time indicates flow velocity as a function of time, and this is plotted in yellow. Because the frequency shift is in the audible range it can be sent to a loudspeaker and a trained operator can use the sound for diagnostic purposes.
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