How to image?

a.     Protocols

Cardiac imaging is performed by a wide variety of operators using a wide variety of machines employing a wide variety of protocols. Ultrasound assisted physical examination (UAPE), point of care cardiac ultrasound (POCUS), critical care echocardiography (CCE), limited and comprehensive traditional TTE, TEE and stress echocardiography all can play a role in caring for patient with suspected or confirmed COVID-19. UAPE and POCUS exams performed by the clinicians who are already caring for these patients at bedside presents an attractive option to screen for important cardiovascular findings, elucidate cardiac contributions to symptoms or signs, triage patients in need of full feature echocardiographic services and even, perhaps, identify early ventricular dysfunction during COVID-19 infection, all without exposing others and utilizing additional resources. Depending on the capabilities of the machines used, images obtained by UAPE, POCUS and CCE practitioners can often be saved to allow remote interpretive assistance from more experienced echocardiographers. Archiving these images for review should help to focus future imaging studies and provide comparisons of cardiac structure and function over time. In some cases, review of these images by a consulting cardiovascular specialist may obviate the need for an echocardiogram (and therefore reduce staff exposure), as pertinent clinical questions will be answered (e.g. etiology of hypotention).  In other cases, they will indicate the need for more advanced imaging (e.g. wall motion and quantitative valvular assessment).  Therefore, these images should be saved and archived whenever possible.  Some devices use a camera that allows a sonographer or other imaging expert to remotely guide probe placement.

Along the same lines, echocardiographic studies performed on patients with suspected or confirmed COVID-19 should be as focused as necessary to obtain diagnostic views but should also be comprehensive enough to avoid the need to return for additional images. Each study should be tailored to the indication and planned in advance, after review of images from past exams and other imaging modalities. Complete exams may be necessary in some circumstances. Plans for ultrasound enhancing agent (UEA) utilization should be made in advance in order to prevent a sonographer having to wait for the agent to be delivered or having to use more personal protective equipment to exit the patient’s room to obtain the agent. While the safety of UEAs specifically in COVID-19 cases has not yet been determined, they have been used and proved safe in ICU patients. The use of UEAs may therefore be considered in such cases as long as the benefits in terms of diagnostic yield and scan time are favorable.

Regardless of the type of study (UAPE, POCUS, CCE or comprehensive echo), prolonged scanning can expose these clinicians to added risk. An additional consideration when performing a limited transthoracic echo exam is the limitations that may be posed by layers of protective equipment on image quality. Therefore, these studies should not be performed by a sonography student or any other novice/inexperienced practitioner, in order to minimize scanning time while obtaining images of the highest possible quality.

Finally, the results of the exam should be rapidly reviewed and key findings recorded immediately on the patient’s record and communicated to the primary care team to allow hemodynamic management to be optimized.

The group therefore recommends the following:

  • Echocardiographic exams be planned ahead, based on indications, clinical information, laboratory data and other imaging findings to allow for a focused sequence of images that help with management decisions.
  • The use of UEAs should be considered prior to the exam to avoid the need to prolong scan time while awaiting preparation of the agent.
  • Scan times should be minimized by excluding students or novice practitioners from performing imaging.
  • Imaging team should ensure rapid review and reporting of key findings in the patient’s record and communicating them with the primary care team.

a.     Protection

                                 i.     Personnel

Imaging should be performed according to local standards for the prevention of virus spread. Meticulous and frequent hand washing is crucial. In some institutions, the level of PPE required may depend on the risk level of the patient with regard to COVID-19 (minimal risk=not suspected, moderate risk=suspected, high risk=confirmed). In some institutions, suspected and confirmed cases are treated similarly. The types of PPE can be divided into levels or categories (see Table).

  • Standard care involves handwashing or hand sanitization and use of gloves. The use of a surgical face mask in this setting may also be considered.
  • Droplet precautions include gown, gloves, headcover, facemask and eye shield.
  • Airborne precautions add special masks (e.g. N-95 or N-99 respirator masks, or powered air purifying respirator – PAPR systems), and shoe covers.

The local application of each component of PPE can vary according to level or type of risk for TTEs and stress echo exams, but airborne precautions are required during a TEE for suspected and confirmed cases, due to the increased risk for aerosolization. A surgical face mask for patients is recommended for those who are symptomatic, undergoing surface echo examination  provided institutional resources allow this strategy for source control.10

It is important to reiterate that the type of PPE to be used on specific cases will depend on local institutional policy and resources. The US Centers for Disease Control (CDC) provides updated guidelines for PPE use for healthcare workers.4

                                ii.     Equipment

Equipment care is critical in the prevention of transmission. Some institutions cover probes and machine consoles with disposable plastic and forego the use of ECG stickers. It is important to note that the benefit of using protective covers must be balanced against the risk of potential for suboptimal images and prolongation of scan time. Some institutions set aside certain machines or probes for use on patients with suspected or confirmed infection. Although SARS-CoV-2 is sensitive to most standard viricidal disinfectant solutions, care must be taken when cleaning. Local standards vary, but echocardiogram machines and probes should be thoroughly cleaned, ideally in the patient’s room and again in the hallway. Smaller, laptop-sized portable machines are more easily cleaned, but use of these machines should be balanced against potential tradeoffs in image quality and functionality. Please consult vendors’ disinfecting guidelines available on their websites, as procedures vary and could affect the functionality of machines. TEE probes should undergo cleaning in the room (including the handle and chord), then be transferred in a closed container to be immediately disinfected according to the manufacturer’s recommendations. The exact steps to be followed for disinfection of the TEE probe and equipment will depend on local institutional protocols that usually are guided by infectious disease experts and resource availability. The American Institute for Ultrasound in Medicine (AIUM) has specific guidelines for disinfection of ultrasound equipment.11

                              iii.     Role of learners

The performance and interpretation of echocardiographic studies, especially those in suspected or confirmed COVD-19 cases, should be limited to essential personnel. For TEEs, practices may vary, but there should be at most one person to handle the probe and another to operate the machine controls, along with another to administer sedation. Medical education remains important, and echocardiographic practitioners play a crucial role in teaching essential components of cardiovascular medicine, as well as scanning and interpretation skills, to a wide variety of learners. Medical and sonography students, residents, fellows and practicing physicians gain knowledge and experience through rotations on echocardiography services, through observing the performance of studies, hands on scanning and reading with experts. In the current environment, however, elective rotations should be suspended, and restrictions should be placed on trainees who are not essential to clinical care. In many institutions, advanced trainees (e.g., fellows) provide crucial off-hours scanning and interpretation but must follow all applicable procedures to reduce infection transmission. Training and education can be moved “on-line”. The ASE and others provide multiple educational offerings, including webinars and lectures. A variety of simulators are available to teach scanning skills without involving patients.

                              iv.     Other considerations

In addition to limiting the number of echocardiography practitioners involved in scanning, consideration should be given to limiting the exposure of staff who may be particularly susceptible to severe complications of COVID-19. Staff who are >60 years old, have chronic conditions, are immunocompromised or are pregnant may wish to avoid contact with patients suspected or confirmed to have COVID-19, depending on local procedures.

The risk of transmission also occurs in reading rooms. Keyboards, monitors, mice, chairs, phones, desktops, and door knobs should be frequently cleaned, and ventilation provided wherever possible. In some institutions the echo lab reading room is a place where many clinical services congregate to review images. In the current environment, it may be advisable to ask these services to review images remotely while speaking with the echocardiographer-consultant by phone, or review images together via a webinar.