Angiography is useful to investigate congenital heart diseases but has recently been superseded, to a large extent, by Doppler echocardiography. Angiography can also be used for the diagnosis of some acquired heart diseases (e.g. feline hypertrophic cardiomyopathy).

• Non-selective angiography is an easy procedure to perform, with minimal costs involved; selective angiography is a more expensive and specialist procedure.
• Humans often feel a burning sensation in the chest, and vomit following the procedure - particularly with Conray. Cats sometimes vomit.
• It is essential to avoid movement. Thus general anaesthesia is preferred for non-selective angiography, and is essential for selective angiography.
• Contrast medium can be introduced into the heart directly (selective) or indirectly (non-selective) to outline the cardiac chambers and great vessels.
• Plain radiography with rapid film changing, or fluoroscopy taped on video are used to record the images.

Direct (selective) angiography

• Direct (selective) angiography involves introducing the contrast medium directly into the heart using appropriate cardiovascular catheters ( Fig. 2.6 ).
• Fluoroscopy is required to pre-place the catheter in the desired chamber or vessel.
• Access to the right heart is normally via the jugular or a femoral vein either by direct surgical cut-down and exposure, or by cardiovascular introducers (through which catheters can be inserted and passed).
• Access to the left side of the heart is via either the carotid or the femoral arteries, and often a cut-down exposure is preferred to ensure haemostasis on withdrawal of the catheter/s.
• The femoral artery can be ligated (sacrificed) in small animals.

• Non-selective (indirect) angiography is performed by injecting contrast medium into a peripheral vein (usually the jugular, but the cephalic can also be used) and taking serial radiographs.
• The injection needs to be very rapid and requires a 14-18G catheter to achieve this.
• The amount of contrast medium required for a non-selective cardiac study is O.5 - 1.Oml/kg.
• As many radiographs as possible are taken over a lO-15s period following injection - usually three to five radiographs (2-3s for right-sided lesions and 4-10s for left-sided lesions).
• Non-selective angiography is usually more than satisfactory for highlighting abnormalities of the right heart, but can sometimes also be effective for abnormalities of the left heart and left to right shunts.
• One disadvantage of non-selective angiography is the superimposition of the left and right cardiac chambers or structures (e.g. the right atrium and pulmonary valve).

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