Cardiac Imaging

What Imaging Is Best for Redo Noncoronary Cardiac Surgery? An ACR-Guided Workflow

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What Imaging Is Best for Redo Noncoronary Cardiac Surgery? An ACR-Guided Workflow

A 68-year-old male with a history of coronary artery bypass grafting (CABG) a decade ago now presents with severe, symptomatic mitral regurgitation. His cardiologist and cardiothoracic surgeon agree that a mitral valve replacement is necessary. During the preoperative consultation, the surgeon expresses concern about the risks of sternal re-entry, specifically the proximity of the heart and prior bypass grafts to the sternum. You need to order imaging that will not only re-evaluate his valve and cardiac function but also provide a clear anatomical roadmap for the surgical approach. This article details the American College of Radiology (ACR) recommended imaging workflow for this specific scenario: an adult with a history of cardiothoracic surgery needing preprocedural planning for noncoronary cardiac surgery. For this patient, a transesophageal echocardiogram is rated Usually Appropriate.

Who Fits This Clinical Scenario?

This guidance applies specifically to adult patients undergoing preoperative planning for noncoronary cardiac surgery who have a history of previous cardiothoracic surgery. The key elements are the “re-do” nature of the operation and the noncoronary target of the new procedure.

Inclusion Criteria:

  • Patient: Adult.
  • History: Prior surgery involving sternotomy or thoracotomy (e.g., CABG, valve replacement, aortic repair).
  • Current Plan: A planned noncoronary cardiac procedure, such as valve repair/replacement, arrhythmia surgery (e.g., MAZE procedure), septal myectomy for hypertrophic cardiomyopathy, or ascending aorta repair.
  • Indication: Preprocedural planning to assess anatomy, function, and surgical risk.

This workflow is distinct from other similar clinical situations. You should seek different guidance if your patient:

  • Has no history of cardiothoracic surgery: A first-time cardiac surgery patient has a different risk profile and anatomical considerations.
  • Is undergoing coronary surgery: Patients planned for a primary or re-do CABG fall under a separate ACR variant, as the focus is on graft planning and target vessel assessment.
  • Is undergoing non-cardiac thoracic surgery: A patient with prior CABG now needing a lobectomy for lung cancer requires a different imaging strategy focused on pulmonary and pleural anatomy.

What Anatomic and Functional Questions Are You Working Up?

In a re-do cardiac surgery scenario, imaging is less about discovering a new diagnosis and more about answering critical questions to ensure surgical safety and success. The “differential” consists of potential anatomical hazards and functional states that will dictate the operative plan.

Proximity of Vital Structures to the Sternum
This is the paramount concern. After a prior sternotomy, dense adhesions can form, tethering the right ventricle, ascending aorta, or a patent internal mammary artery (LIMA) graft directly to the posterior surface of the sternum. An oscillating saw during sternal re-entry can catastrophically injure these structures, leading to massive hemorrhage. Imaging must precisely delineate this relationship.

Updated Valvular and Ventricular Assessment
The primary reason for surgery (e.g., mitral regurgitation, aortic stenosis) must be thoroughly re-evaluated. This includes quantifying the severity of the lesion, assessing leaflet morphology, and measuring annular dimensions. Concurrently, an updated evaluation of left and right ventricular systolic function (e.g., ejection fraction) is essential for risk stratification and planning cardiopulmonary bypass.

Aortic Atherosclerosis (Atheroma)
The ascending aorta and arch must be carefully inspected for mobile or ulcerated atherosclerotic plaque. Aortic cannulation and cross-clamping can dislodge this debris, causing a perioperative stroke. Identifying severe “shaggy” aorta may lead the surgeon to alter the cannulation strategy or perform the operation off-pump or with deep hypothermic circulatory arrest.

Status of Prior Grafts and Repairs
While the current surgery is noncoronary, the patency and location of previous bypass grafts are crucial. A patent LIMA graft crossing the midline is at high risk during sternal re-entry. The status of previously repaired valves or aortic conduits also needs to be confirmed.

Why Is Transesophageal Echocardiography a Recommended Study?

For preoperative planning in a patient with prior cardiothoracic surgery undergoing a noncoronary procedure, the ACR rates US echocardiography transesophageal (TEE) as Usually Appropriate. It provides a unique combination of high-resolution anatomical imaging and dynamic functional assessment with no ionizing radiation (0 mSv).

TEE excels at visualizing posterior cardiac structures, which are often the target in noncoronary surgery (e.g., mitral valve, left atrium, aortic valve). Its proximity to the heart, unimpeded by the chest wall, sternal wires, or lung tissue, yields superior image quality for assessing valvular morphology, quantifying regurgitant jets with color Doppler, and measuring pressure gradients. It is also highly sensitive for detecting aortic atheroma, especially in the ascending aorta and arch, which is a critical part of the preoperative risk assessment.

However, several other studies are also rated Usually Appropriate, and the choice often depends on the primary surgical question.

  • CT Chest with IV Contrast (☢☢☢ 1-10 mSv): This is arguably the most important complementary study and is often ordered first if the primary concern is the risk of sternal re-entry. CT provides an unambiguous, cross-sectional map of the mediastinum, definitively showing the distance between the sternum and underlying structures like the right ventricle and ascending aorta. It is superior to all other modalities for this specific question.
  • US Echocardiography Transthoracic Resting (0 mSv): A transthoracic echocardiogram (TTE) is almost always performed as an initial, noninvasive screen. However, in postoperative patients, acoustic windows can be poor, limiting a comprehensive evaluation. It is considered a foundational test, but TEE or CT is often required for the detailed planning needed in this high-risk scenario.
  • Radiography Chest (☢ <0.1 mSv): A simple chest X-ray is standard practice. It confirms the position of sternal wires, valve prostheses, and pacemaker leads but provides no detailed information about soft tissue relationships or cardiac function.

An alternative rated lower is Coronary MRA, which is Usually not appropriate. This study is designed to visualize the coronary arteries, which is not the goal of a noncoronary cardiac surgery workup. It does not provide the necessary detail on valvular function or sternal-adhesion relationships.

What’s Next After Imaging? Downstream Workflow

The imaging results directly shape the surgical plan and patient counseling. The downstream workflow depends on which critical findings are identified.

  • If CT shows a “hostile chest” (e.g., RV or patent LIMA adherent to the sternum): The surgeon may alter the approach entirely. Instead of a re-do sternotomy, they might opt for a right thoracotomy, establish peripheral femoro-femoral cardiopulmonary bypass before opening the chest, or use advanced dissection techniques. This finding fundamentally changes the risk profile of the operation.
  • If TEE shows severe, mobile aortic atheroma: The surgical plan for cannulation and aortic cross-clamping will be modified. The surgeon might choose an axillary artery cannulation site to avoid the diseased aorta or perform the procedure under deep hypothermic circulatory arrest to minimize the risk of embolic stroke.
  • If TEE reveals unexpected findings: For instance, if a patient planned for mitral valve surgery is found to have significant tricuspid regurgitation or a patent foramen ovale, the surgeon can plan to address these issues concurrently during the same operation.
  • If imaging is reassuring: When CT shows a safe retrosternal space and TEE confirms the expected pathology without other complicating factors, the team can proceed with a standard re-do sternotomy approach with confidence, having mitigated the major anatomical risks.

Pitfalls to Avoid (and When to Get Help)

Navigating preoperative imaging for re-do cardiac surgery requires careful consideration to avoid common errors.

  • Relying solely on TTE: While a good starting point, TTE often provides incomplete data in postoperative patients. Do not assume a “limited” TTE is sufficient for high-risk surgical planning.
  • Ordering a non-contrast CT: For assessing the relationship of vascular structures (aorta, bypass grafts) to the sternum, intravenous contrast is essential. A non-contrast chest CT is Usually Appropriate but provides significantly less information for this specific surgical question.
  • Forgetting the aorta: Focusing exclusively on the primary pathology (e.g., the mitral valve) and failing to carefully assess the ascending aorta for atheroma on TEE or CT is a major pitfall that can lead to devastating neurologic complications.
  • Miscommunication of key findings: The critical distances (e.g., aorta-to-sternum) and atheroma locations must be clearly and quantitatively communicated from the radiologist/cardiologist to the surgeon.

If there is any ambiguity about the safety of sternal re-entry after noninvasive imaging, direct consultation between the imager and the cardiothoracic surgeon is critical to determine if additional studies or an alternative surgical approach is warranted.

Related ACR Topics and Tools

For a comprehensive overview of imaging recommendations across all cardiothoracic surgery scenarios, refer to our parent guide. For further exploration of specific modalities or adjacent clinical questions, the following resources are available.

Frequently Asked Questions

Why is CT with contrast also ‘Usually Appropriate’ if TEE is recommended?

CT with contrast and TEE answer different primary questions. TEE is superior for assessing dynamic valve function and detecting aortic atheroma. CT is unparalleled for precisely measuring the distance between the sternum and vital structures like the right ventricle or bypass grafts. Often, both are needed to create a complete preoperative plan, with the choice of which to order first depending on whether the surgeon’s main concern is functional assessment or the safety of sternal re-entry.

Is a cardiac MRI useful in this re-do surgery scenario?

According to the ACR, cardiac MRI (e.g., MRI heart function and morphology) ‘May be appropriate’. It can provide excellent data on ventricular function, viability, and morphology, especially when echocardiographic images are poor. However, it is less commonly used for primary surgical planning in this context because it does not assess valve dynamics as well as TEE and is less available and more time-consuming than CT for anatomical mapping.

What if my patient has renal insufficiency and cannot receive IV contrast for a CT?

If IV contrast is contraindicated, a non-contrast chest CT is still rated ‘Usually Appropriate’. While it cannot delineate vascular structures like patent grafts as clearly, it can still show the soft tissue plane (or lack thereof) between the posterior sternal table and the cardiac silhouette, providing valuable information about adhesions and retrosternal space.

Does the type of prior surgery (e.g., valve vs. CABG) change the imaging recommendation?

No, this specific ACR scenario groups all prior cardiothoracic surgeries together. The key factor is the presence of a sternotomy/thoracotomy scar and the potential for mediastinal adhesions. However, the patient’s specific history (e.g., a known LIMA graft from a prior CABG) will heighten the focus on certain anatomical areas during the imaging interpretation.

Is TEE performed awake in the clinic or under anesthesia?

Preoperative TEE for surgical planning is typically performed as an outpatient procedure with the patient under conscious sedation. It is distinct from the intraoperative TEE that is performed after the patient is under general anesthesia to guide the surgical repair and confirm the result.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026