CT scan & MRI of heart

Trans-oesophageal echocardiography

Particularly useful for evaluating mitral valve function. Usually performed in theatre to evaluate mitral valve function pre and post mitral valve repair.

Computed tomography

CT scanning is frequently used to exclude post operative pulmonary emboli (spiral CT of the chest), determine presence of thoracic aortic aneurysms, and confirm or exclude neurological sequalae of cardiac surgical procedures (embolic, haemorhagic, hypoperfusion brain injury). Refer to chapter five (Transport of the critically ill) for safe management of patients requiring this procedure. CT uses thin, fan shaped X-ray beam that pass through the patient. The number of X-rays deleted from the beam is directly proportional to the density of the tissue in its path. Contrast media CT scanning can also be used although special precautions must be followed as contrast media is used (renal impairment, allergy).

Cardiac catheterisation

Cardiac catheterisation involves passing a radiopaque catheter via an artery or vein into the chambers of the heart to obtain chamber pressures, ventricular function and wall motion. Coronary angiography examines abnormalities in coronary artery blood flow via injection of contrast medium directly into the vessels.

Right heart catheter is performed to evaluate:

· valvular disease

· congenital heart disease

· pericardial tamponade

· electrophysiological studies

Left heart catheter

· evaluation of aortic and mitral valve disease

· measurement of left ventricular function

Coronary angiography

· unstable angina

· atypical chest pain

· primary PTCA within first hour of AMI

· to check patency of coronary artery grafts in selected patients with threatened AMI post operatively. Refer to chapter five (Transport of the critically ill) for safe management of patients requiring this procedure.

Magnetic resonance imaging

A non-invasive test that provides high resolution tomographic images. Indications include abnormalities of the aorta, gross patency of myocardial revascularisation conduits and pericardial disease. MRIs generate strong magnetic fields and therefore patients must remove all metal jewellery and appliances before scanning. Very small amounts of metal such as surgical haemoclips and staples are not adversely affected. Larger permanent devices such as pacemakers, physiological support equipment such as ventilators and infusion pumps are affected. The cardiothoracic unit does not have appropriate equipment to transport ventilator dependent patients to the MRI department and the procedure should be co-ordinated with the general ICU.