Study note
MedicineCardiology

Cardiac catheterisation: left and right heart assessment

THE CONTEXT
Cardiac catheterisation passes a specialised catheter through a peripheral vein or artery into the heart under X-ray guidance to obtain haemodynamic measurements and angiographic images.

General capabilities

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Blood pressure and oxygen saturation can be measured in cardiac chambers and great vessels.
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Injection of contrast medium into a chamber or blood vessel allows angiography.

Left heart catheterisation

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Arterial access is usually through the radial artery, allowing catheterisation of the aorta, left ventricle and coronary arteries.
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Coronary angiography selectively images the left and right coronary arteries to assess the extent and severity of stenoses, thrombus and calcification.
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Intravascular ultrasound and optical coherence tomography provide additional anatomical assessment, while pressure wire assessment provides functional information. These assessments help define plaque characteristics and severity and support planning of percutaneous coronary intervention or coronary artery bypass graft surgery.
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Left ventriculography assesses left ventricular size and function and can demonstrate mitral regurgitation.
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Aortography defines aortic root and thoracic aortic size and can help quantify aortic regurgitation.
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Left heart catheterisation is a day-case procedure; serious complications occur in approximately 1 in 1000 cases.

Right heart catheterisation

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Right heart catheterisation measures right heart and pulmonary artery pressures and detects intracardiac shunts by comparing oxygen saturations in different chambers.
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An oxygen saturation step-up from 65% in the right atrium to 80% in the pulmonary artery indicates a large left-to-right shunt, which might be due to a ventricular septal defect.
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Cardiac output can be measured using thermodilution.

Left atrial and wedge pressures

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Left atrial pressure can be measured directly by passing a special catheter through the interatrial septum from the right atrium.
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For most purposes, wedging an end-hole or balloon catheter in a pulmonary artery branch provides a satisfactory approximation of left atrial pressure.
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Swan–Ganz balloon catheters are often used to monitor pulmonary wedge pressure as a guide to left heart filling pressure in critically ill patients.
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