REF002 - Radionuclide Ventriculography

The purpose of this document is to assist clinicians in deciding on the appropriateness of a Nuclear Medicine ventriculography investigation and to give guidance on the mechanism of referral.

Radionuclide ventriculography is a reproducible technique for assessing left ventricular function and left ventricular ejection fraction. The role of radionuclide ventriculography is falling, however, with the continued development of more reliable echocardiographic techniques. There are problems with echocardiography, however, and the quality of results is very dependent on the skill of the operator. Echocardiography studies are technically difficult in approximately 10% of patients, such as those with lung disease, and imaging is less than ideal in 30%. Evaluation of the inferior wall of the left ventricle is difficult and echocardiography is forced to make assumptions about ventricular geometry for a quantitative assessment of function which yields only semiquantitative results that are considerably worse in badly impaired ventricles. Radionuclide ventriculography does not require assumptions to be made about geometry and its strength is in its reproducibility, especially in impaired ventricles.

The radiopharmaceutical used for this investigation is in vivo labelled technetium-99m red blood cells. Non-radioactive stannous ions are injected into the bloodstream and act as a reducing agent. Tc^99m pertechnetate is then injected approximately 20-30 minutes later and passively diffuses into red blood cells, but is prevented from diffusing back by the reduction process which causes binding to the beta chain of haemaglobin.

Multiple gated imaging uses the R wave of the patient ECG to identify the start of a cardiac cycle. The period between each R wave is divided into a number of frames, usually 16, and the counts occurring in the same frame of each cycle are summed into a single image. Studies are acquired for several hundred cardiac cycles. Multiple gated studies have the advantage that images can be acquired in several projections, but the disadvantage that the study will be unsuccessful in patients with a highly variable RR interval.

• Any clinician holding a current valid medical qualification currently employed Secondary care (Or Primary care if a Secondary care specialist has recommended it).

Referring clinicians are reminded of the requirement to avoid unnecessary exposure to ionising radiation. The investigation may already have been requested at this hospital or elsewhere and clinicians are asked to be particularly vigilant to ensure that their request is not a double request.

Requests will only be accepted if the diagnostic question fulfills one of the referral criteria below. Appropriate clinical information must be supplied to allow the investigation to be justified. It is not acceptable to simply request the investigation without appropriate clinical information.

Requests will be returned to the referrer if:

• The diagnostic question is unclear.
• The diagnostic question cannot be answered by the investigation.
• Insufficient clinical information is supplied to justify the investigation.

Requests must be submitted electronically via WebV. Clinical Details, Diagnostic Question and Medication should be fully and appropriately completed.

Sufficient clinical information must be provided to justify the investigation proceeding.

The clinical indications are detailed below.

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