CPT® Code 0332T

1. Indications

The myocardial sympathetic innervation imaging procedure is indicated for various clinical scenarios where assessment of the sympathetic nervous system's influence on cardiac function is necessary. The following conditions may warrant this imaging technique:

• Heart Failure Assessment of sympathetic innervation can help evaluate the severity and prognosis of heart failure.
• Cardiac Arrhythmias Identification of sympathetic nerve activity may assist in understanding the underlying mechanisms of arrhythmias.
• Coronary Artery Disease Evaluation of sympathetic innervation can provide insights into the impact of coronary artery disease on cardiac function.
• Risk Stratification The imaging can be used to assess mortality risk in patients with known cardiac conditions.

2. Procedure

The myocardial sympathetic innervation imaging procedure involves several key steps to ensure accurate assessment of cardiac sympathetic innervation. The following procedural steps are performed:

• Step 1: Patient Preparation The patient is prepared for the procedure by ensuring they are at rest and have been instructed on the process. It is essential to confirm that the patient has not consumed any substances that may interfere with the imaging results, such as certain medications or foods.
• Step 2: Administration of I-mIBG Radiolabeled metaiodobenzylguanidine (I-mIBG) is administered intravenously to the patient. This compound is crucial for visualizing the sympathetic innervation of the heart.
• Step 3: Imaging Acquisition After the administration of I-mIBG, imaging is conducted. Initially, planar views of the chest are obtained 10-30 minutes post-injection, followed by additional imaging at 3-4 hours. In this procedure, both planar imaging and tomographic single-photon emission computed tomography (SPECT) are utilized to capture comprehensive data regarding the heart's sympathetic innervation.
• Step 4: Qualitative Assessment A qualitative assessment of the images is performed, focusing on the visual interpretation of I-mIBG uptake and distribution within the heart muscle. This step is critical for identifying any abnormalities in sympathetic innervation.
• Step 5: Quantitative Assessment A quantitative or semi-quantitative assessment is conducted by identifying specific regions of interest in the heart and mediastinum. The uptake of mIBG is quantified by calculating the heart to mediastinum (H/M) ratio, which provides insight into norepinephrine retention by sympathetic neurons.
• Step 6: Image Review and Reporting The physician reviews the acquired images, calculates the mIBG uptake heart to mediastinum ratio, and compiles a written report detailing the findings. This report is essential for guiding further clinical decision-making.

3. Post-Procedure

After the myocardial sympathetic innervation imaging procedure, patients are typically monitored for any immediate reactions to the I-mIBG administration. There are generally no specific post-procedure care requirements, and patients can resume normal activities unless otherwise instructed by their healthcare provider. The physician will review the imaging results and discuss the findings with the patient, which may include recommendations for further evaluation or treatment based on the assessment of sympathetic innervation and its implications for cardiac health.