I. INTRODUCTION. Echocardiography is an important component of the design and success of cardiovascular procedures in patients with structural heart disease. In this context, intraprocedural echocardiography (IPE) refers to imaging in the setting of procedures, including cardiac operations or transcatheter interventions. It is useful for defining the abnormal anatomy and physiology, guiding alignment and position of implanted devices, assessing valve regurgitation and stenosis after device deployment or surgery is done, and identifying postprocedural complications.
Intraoperative echocardiography (IOE) began in the early 1980s with left ventricular (LV) monitoring during noncardiac surgery. In the next decade, it expanded exponentially, spearheaded by its utility in valve repair for mitral regurgitation (MR). At this time, IOE is utilized in most cases of valve and congenital heart surgery. In adults, the method is mostly transesophageal echocardiography (TEE), and the majority of the persons doing the imaging are anesthesiologists. IOE is mandatory when unusual anatomic challenges or complex anatomic decisions are needed.
Similarly, the more recent advent of transcatheter structural interventions has introduced a new need for guidance by IPE. In most cases, TEE is used in a complementary tandem with fluoroscopy and angiography to achieve the desired goals. Echocardiographic images, fluoroscopic images, and pressure waveform data should all be easily viewable by all members of the multidisciplinary team.
TEE is useful in many transcatheter applications, including implantation of a prosthesis or device, and anatomic interventions such as balloon dilation, ablation, or puncture. Valve interventions and valve surgery benefit from imaging that can characterize soft tissue, which cannot be done with fluoroscopy alone. Table 18.1
lists a variety of procedures in the catheterization lab or operating room for which IPE has value, the most common of which will be described in this chapter. In transcatheter procedures done under light sedation (rather than general anesthesia), transthoracic echocardiography (TTE) may be of some limited value. However, TTE has reduced image quality and more potential to interfere with the sterile field. Because frequently the patient cannot be rolled onto their left side during these procedures, TTE is usually of insufficient quality to provide the precise assessments needed for IPE.
II. BASIC CONCEPTS OF INTRAPROCEDURAL ECHOCARDIOGRAPHY FOR GUIDANCE OF CARDIOVASCULAR PROCEDURES
For patients undergoing surgery involving cardiopulmonary bypass with cardioplegia, IPE is usually done before (prepump) and after (postpump) the heart is stopped. For most transcatheter procedures and off-pump surgeries performed with the heart beating, IPE is feasible throughout the procedure, including before (pre-IPE), during (intra-IPE), and after (post-IPE) the actual implantation or anatomic change. Its important ability is to guide the intervention and define its success or failure.
TABLE 18.1 Procedures or Problems for Which Intraprocedural Echocardiography Is Useful
Surgical or transcatheter valve repair
Surgical or transcatheter valve replacement
Closure of defect or fistula, including paraprosthetic leak
Hypotension or hemodynamic derangement of uncertain etiology
Congenital heart surgery
Complex procedures, which are new to the current interventional/operative team
A. Before the procedure, whether the surgical or transcatheter change in the patient’s anatomy is made by implantation of a device or some other method, IPE has a role in defining the therapeutic plans. This includes determining the feasibility of the intervention, measuring the space where that intervention may occur, documenting the pretreatment magnitude of dysfunction, and defining other cardiovascular abnormalities that coexist with the primary problem(s). In most patients, IPE confirms the diagnoses made before the procedure. The imager should look carefully for changes in the anatomy that may have occurred since the preoperative imaging. This includes dysfunction of other valves, unexpected myocardial dysfunction, superimposed problems, or spontaneous improvement in the lesion(s) of importance. Incorporating these new findings into the procedural plans helps to avoid foibles and unintended outcomes.
Even when the patient is already in the procedure room or operating room, the pre-IPE may change the ratio of risk versus benefit of performing the procedure at all. Even if the patient is already anesthetized or the incision is made, it is better to do the right thing, even if it is a new plan not anticipated preoperatively. The likely success and clinical outcome of doing the planned procedure may be altered if new abnormalities are found by the echocardiogram.
Innovations in treatment of valvular heart disease are very much the purview of IPE. When the experience of the surgeon or interventionalist is less for a given procedure, especially when the procedure is new or the disease state is uncommon or complicated, IPE helps define the territory, clarify the feasibility, and avoid complications of the procedure. The accuracy of diagnosis at any phase depends on the ability to image the relevant anatomy and physiology and understand them.
B. IPE at the moment of the intervention (intra-IPE): Most transcatheter procedures, similar to on-pump cardiac surgery, are done with the heart beating, and so the imaging guidance provided by IPE includes the moment of implantation. The specific role of IPE is to guide the therapeutic activity to the correct location, at exactly the right angle and orientation. Many of these imaging objectives are specific for each procedure and will be discussed later in this chapter.
C. Immediately after the procedure. IPE is helpful in documenting the anatomic and physiologic success of the procedure(s), or determining the need for more work. Before leaving the operating room or procedure laboratory, it is useful to know about the new state of myocardial function, blood flow, and valve function. The frequency of treatment failure on the initial procedure varies with the mechanism and complexity of the original problem. If further interventional or surgical treatment is needed, the IPE is instrumental in defining and directing the available remedies. For surgery done on cardiopulmonary bypass, this entails a “second pump run.” Another venue of IPE is identification of unanticipated emergencies. When patients have sudden hypotension, shock, or alteration of electrical or mechanical activity, online assessment can immediately define the nature of the aberration.
D. Completeness of study including 3DE: In most patients who are undergoing intraprocedural imaging, we recommend performing a complete TEE study, including a long- and short-axis view of every valve and each chamber, using structural imaging (black and white), color Doppler, and relevant spectral Doppler recordings for each valve or lesion. This enthusiasm for completeness must be tempered by the realities of clinical urgency and numerous patient-specific issues. Three-dimensional echocardiography (3DE) is now part of the technologic armamentarium of IPE. However, 3DE is sometimes cumbersome and time-consuming and is not always as versatile for making quick online decisions as 2D imaging. Still, 3DE has great utility in communicating anatomic details to a surgeon or interventionalist with less experience in tomographic imaging. It facilitates understanding the location and dynamic anatomy of the abnormal valve, sharpens expectations, and enhances success. 3DE often requires offline analysis of stored three-dimensional data sets.
E. Choice of echocardiographic imaging modalities: TEE is the most commonly used modality for IPE of valve procedures in the catheterization lab or operating room, but intraprocedural TTE, epicardial echocardiography, or intracardiac echocardiography (ICE) may be used in some cases. Rarely, these other modalities may be preferred, especially when there are contraindications or difficulties in placement of the TEE probe (such as esophageal disease), or when working on an anterior structure like the pulmonary valve. The inherent risks and potential adverse effects vary with each procedure, including potential esophageal trauma resulting from TEE, vascular trauma from ICE, or incomplete data from any of them. Epicardial echocardiography, placing a transducer on the surface of the heart, is an adequate substitute in open chest surgeries and may be superior to TEE in certain indications, such as assessment of hypertrophic cardiomyopathy or atheroma of the ascending aorta. Computerized tomography and magnetic resonance imaging would also be useful during valve procedures and operations; however, cost, space, speed, and radiation exposure presently make them impractical. A novel method has been developed that integrates echocardiography and fluoroscopy (EchoNavigator, Philips Healthcare, Best, the Netherlands) by marrying the two coordinate systems to visualize both modalities on one screen simultaneously. By tracking markers on specific points of interest on these combined images, guidance of transcatheter procedures is facilitated. What imaging modalities are chosen depends on the abilities and experience of the imaging team, and especially the ability of the surgeon or interventionalist to incorporate this information into decisions that will improve outcome.
F. Subjective and quantitative diagnosis
1. The images generated and diagnoses made with IPE are mostly interpreted subjectively. Some quantitative measurements can be made quickly at the time of image acquisition, at the cost of minor delay. At the ends of the spectrum of abnormalities (very good or very poor), such quantitation is often not necessary. However, in the moderate range of many abnormalities, specific measurements add substantially to the impact of imaging on procedural decisions. Measurements of diameter, area, or volume by tracing on selected IPE images may derive important information about the valve disease in question. Even when measurements are not accomplished during the procedure, it is often useful to store video clips, still frames, or 3D volume sets that would enable quantitation later. The learning curve of how to obtain the most relevant and reliable information efficiently often results from experience performing and interpreting echocardiography outside the catheterization lab or operating theater.
Before any IPE, the imager should be well versed with the patient’s clinical picture, the current decisions at hand, the plans made by other clinicians, and the procedure that is anticipated. This usually entails direct review of the preprocedural imaging studies and goes way beyond just knowing the central diagnosis or the planned procedure. This working knowledge of the prior
findings helps the imager to identify new information during the pre-IPE, which would affect the plans.
3. When TEE is planned, it is important to be certain that there are no contraindications to esophageal endoscopy such as esophageal stenosis, esophageal cancer, or significant dysphagia. When these issues are raised, preoperative studies such as upper gastrointestinal endoscopy should be performed to decide if the TEE probe can be introduced safely.
4. The patient should be fasting before a TEE study and the risks, benefits, and alternatives to TEE reviewed with either the patient or family, and with the primary doctors involved. Compared with the minor additional risk of TEE probe insertion, much can be gained by online imaging.
5. In procedures where the patient will not have endotracheal intubation or general anesthesia, the decision to do a TEE is much less obvious. For example, procedures done under light sedation may be done with TEE, or with TTE, but the latter provides less value to the success of the procedure. Another issue affecting the decision to do without TEE is the intended position of the patient during the procedure. If the patient will be supine without an endotracheal tube, TEE requires frequent suctioning of the hypopharynx to prevent aspiration of saliva. The team must make a value judgment between the advantages of a less involved form of anesthesia with disadvantages of losing additional guidance that could be provided by TEE. Likewise, valve repair surgery may be done without intraoperative TEE, but the potential for finding problems with TEE still makes it a good choice.
III. INTRAPROCEDURAL ECHOCARDIOGRAPHY IN SPECIFIC OPERATIONS OR TRANSCATHETER PROCEDURES
A. IPE in mitral valve surgery
This is the bedrock of the invasive echocardiography movement of the last three decades (Table 18.2
). The prepump TEE helps to define the mechanism and severity of MR before the surgery (Fig. 18.1
). The surgeon must understand the dysfunction in order to enable successful repair. Pre-IPE contributes to a change in plans (sometimes minor) in about 15% of patients in our experience.
IPE can detect problems after the mitral repair, most commonly persistent MR. In most cases, we accept mild or no MR on the post-IPE and do further surgery if the MR is 3+ (moderately severe) or more. If it is 2+, we do further surgery if there is no contraindication, or we observe without decannulating, while giving an afterload challenge of boluses of phenylephrine to raise blood pressure. Also
occurring with substantial frequency are new systolic anterior motion of the mitral valve and new wall motion abnormalities, particularly in the right coronary artery territory, due to its anterior ostium. A second run of cardiopulmonary bypass, to fix the problem(s) during the same thoracotomy, occurs in 3% to 6% of cases. Mitral valve replacement can be complicated by paravalvular leaks (PVLs) that are discernible by the postpump intraoperative TEE and are fixable on a second pump run.
TABLE 18.2 Utility of Echocardiography in Surgical Repair for Mitral Regurgitation
Prepump Transesophageal Echocardiography (TEE)—The “Road Map”
Severity of regurgitation
Mechanism of regurgitation, repairability
Ventricular function, wall motion
Abnormalities of other valves
Postpump TEE—The “Safety Net”
Severity of mitral regurgitation
Mitral systolic anterior motion
New left ventricular dysfunction
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