LCD L38786: Echocardiography for Myocardial Perfusion

Overview

This is a coverage policy for contrast (also known as ultrasound enhancing agent-UEA) administration for purposes of echocardiographic myocardial perfusion evaluation.

Decades of work have been invested in the refinement of microbubble technology for UEAs. Much focus has also been brought to bear on optimization of echocardiographic settings, software and hardware to facilitate this technology. Huge advances have been made over these many years.

Commercially available UEAs that are approved for use by the United States Food and Drug Administration are composed of encapsulated microbubbles. The use of these microbubbles is based on their ability to undergo volumetric oscillation in the pressure fluctuations of the ultrasound field. Microbubble vibration can occur without compromise of its integrity (stable cavitation) or can be accompanied by either sudden or gradual destruction from exaggerated non-linear oscillation when ultrasound is delivered at high ultrasound pressure amplitude. This process allows for a strong acoustic signature that can be separated from tissue with specially designed and commercially available imaging protocols.

There are currently 3 UEAs approved by the FDA. The only FDA-approved use in cardiovascular disease is for left ventricular opacification (LVO) using IV injections. LVO is used to better define endocardial borders when accurate dimensions and volumes cannot be readily obtained because of the poor quality of endocardial visualization. Suboptimal images limit unenhanced echocardiographic interpretation in a substantial percentage of studies.

Many off-label uses for UEAs exist and have been investigated for years. These uses include, but are not limited to, applications related to myocardial perfusion and viability. This LCD addresses the issue of coverage for some of these off-label uses.

Noncovered Services

• Use of non-FDA approved UEAs

• The administration of UEAs for myocardial perfusion evaluation strictly for screening purposes

Myocardial Perfusion

A study was done to prospectively compare patient outcomes after echocardiography for simultaneous myocardial perfusion and wall motion analysis (also called real-time myocardial contrast echocardiography-RTMCE) and conventional stress echocardiography. There had been no other prospective randomized studies prior to this one looking at this issue. The authors for this study looked to determine whether the differences in the test led to differences in the rate of angiography and revascularization, as well as predicting death. The patients were recruited from consecutive patients coming to the University of Nebraska Medical Center echo lab between 2007 and 2011 who had intermediate to high pre-test probability for coronary artery disease (CAD). This included patients hospitalized for chest pain. Mean age for study patients was 60 with a nearly equal male:female ratio. Follow up was captured for 2,014 patients for a median of 2.6 years. An abnormal RTMCE occurred more often than an abnormal conventional stress echo (p 1

In a 1997 study, 28 patients were given a single IV injection of an UEA and then harmonic transient response imaging was used to view the heart in multiple different imaging planes. Perfusion abnormalities were evident in the secondary and tertiary views only with 1 frame every multiple cardiac cycles. The conclusion was that an enhancing agent could accurately identify regional myocardial perfusion abnormalities. Sensitivity of 92% was noted and specificity of 84%. 2

In 2001, a comparative study was done to examine the feasibility and accuracy of RTMCE in detecting abnormal myocardial perfusion during an exercise echo compared with radionuclide tomography. One hundred patients (2:1 men:women with median age of 57) with intermediate to high CAD probability underwent exercise echocardiography and had segmental perfusion assessed in real time before the test and at peak exercise using low mechanical index (0.3) and 0.3 mL bolus injections of the enhancing agent. All patients had rest thallium, stress sestamibi studies done during the same exercise. Forty-four of these patients had subsequent coronary angiography. Compared with angiography, sensitivity of RTMCE and tomography was comparable (75%) with a specificity ranging from 81-100%. The combination of RTMCE and wall motion had the best matching between sensitivity and specificity at 86% and 88% respectively with the highest accuracy (86%). The conclusions were described as “promising” with regard to adding RTMCE to conventional stress echo. 3