Assessing myocardial perfusion with Albunex during coronary artery bypass surgery: technical considerations and safety of aortic root injections

Safety of ultrasound contrast agents in patients with known or suspected cardiac shunts

Contrast-enhanced ultrasound imaging is a radiation-free diagnostic tool that uses biocompatible ultrasound contrast agents (UCAs) to improve image clarity. UCAs, which do not contain dye, often salvage "technically difficult" ultrasound scans, increasing the accuracy and reliability of a front-line ultrasound diagnosis, reducing unnecessary downstream testing, lowering overall health care costs, changing therapy, and improving patient care. Two UCAs currently are approved and regulated by the US Food and Drug Administration. They have favorable safety profiles and risk/benefit ratios in adult and pediatric populations, including compromised patients with severe cardiovascular diseases. Nevertheless, these UCAs are contraindicated in patients with known or suspected right-to-left, bidirectional, or transient right-to-left cardiac shunts. These patients, who constitute 10% to 35% of the general population, typically receive no UCAs when they undergo echocardiography. If their echocardiographic images are suboptimal, they may receive inappropriate diagnosis and treatment, or they may be referred for additional diagnostic testing, including radiation-based procedures that increase their lifetime risk for cancer or procedures that use contrast agents containing dye, which may increase the risk for kidney damage. An exhaustive review of current peer-reviewed research demonstrated no scientific basis for the UCA contraindication in patients with known or suspected cardiac shunts. Initial safety concerns were based on limited rodent data and speculation related to macroaggregated albumin microspheres, a radioactive nuclear imaging agent with different physical and chemical properties and no relation to UCAs. Radioactive macroaggregated albumin is not contraindicated in adult or pediatric patients with cardiac shunts and is routinely used in these populations. In conclusion, the International Contrast Ultrasound Society Board recommends removal of the contraindication to further the public interest in safe, reliable, radiation-free diagnostic imaging options for patients with known or suspected cardiac shunts and to reduce their need for unnecessary downstream testing.

Contrast-enhanced ultrasound for myocardial perfusion imaging

Ultrasound contrast agents are gas-filled microbubbles that enhance visualization of cardiac structures, function and blood flow during contrast-enhanced ultrasound (CEUS). An interesting cardiovascular application of CEUS is myocardial contrast echocardiography, which allows real-time myocardial perfusion imaging. The intraoperative use of this technically challenging imaging method is limited at present, although several studies have examined its clinical utility during cardiac surgery in the past. In the present review we provide general information on the basic principles of CEUS and discuss the methodology and technical aspects of myocardial perfusion imaging.

The Role of Transesophageal Echocardiography in Perfusion Management

Intraoperative transesophageal echocardiography (TEE) has been a valuable tool in cardiac surgery. The TEE probe can easily be inserted after endotracheal intuba tion to provide continuous monitoring and diagnosis during surgery. The role of TEE in the operating room is always expanding. This article examines the role of TEE specifically for cardiopulmonary bypass and perfusion management.

Identifying the cause of left ventricular systolic dysfunction after coronary artery bypass surgery: the role of myocardial contrast echocardiography

OBJECTIVE

Intraoperative myocardial contrast echocardiography was used to determine whether the identification of regional myocardial flow patterns during revascularization could predict myocardial contractile function immediately after separation from cardiopulmonary bypass (CPB) and at 1 month after coronary artery bypass grafting (CABG) surgery.

DESIGN

A prospective, open-labeled, longitudinal analysis.

SETTING

Two independent university hospitals.

PARTICIPANTS

Twenty patients, during and up to 1 month after CABG.

INTERVENTIONS

The contrast agent Albunex (Mallenckrodt Medical, Inc, St Louis, MO) was injected into the aortic root during CPB.

MEASUREMENTS AND MAIN RESULTS

Myocardial contrast echocardiography opacification of flow was graded from intraoperative transesophageal echocardiographic images of the left ventricle in the short-axis, midpapillary view. The same myocardial images were also evaluated for regional wall motion abnormalities at 15, 30, and 60 minutes, 24 hours, 5 to 8 days, and 1 month after CPB. Logistic regression analysis was used to analyze the flow scores and regional function data from identical segments. Regional flow represented by contrast enhancement was assessed in 70% of the myocardial regions (55 of 80 possible segments; 95% confidence interval [CI], 61 to 76). Flow was more easily evaluated in the posterior region (95%) than in the anterior (70%) or septal regions (60%), and least likely evaluated in the lateral regions (50%). Regional wall motion was scored in 84% of the myocardial regions (469 of 560 possible regions). Function (segmental wall motion) was assessed in all regions with equal success. Segmental function and flow scores were matched to the same regions 66% of the time (53 of 80 possible series; 95% CI, 55 to 76). Regional myocardial contrast flow patterns did not predict myocardial function at 15, 30, or 60 minutes after separation from CPB. However, contrast opacification of flow did predict regional myocardial function at 1 week (p < or = 0.05) and at 1 month (p < or = 0.01) after CABG surgery. The probability that myocardial function would be normal at 1 month was 0.62 when intraoperative flow opacification was abnormal and 0.98 when flow opacification was normal. For patients with normal flow, the estimated odds of having normal myocardial function were 3.33 times those of patients with abnormal flow at 1 week (odds ratio, 3.33; 95% CI, 1.09 to 10.19) and 18.5 times those of patients with abnormal flow at 1 month (95% CI, 2.44 to 140.48).

CONCLUSION

Intraoperative application of myocardial contrast echocardiography to determine regional flow patterns after revascularization may help differentiate conditions of left ventricular systolic dysfunction immediately after separation from CPB for CABG surgery and appear to predict myocardial function at 1 month.