Pandemics have different phases and transition scenarios. Regardless of the phase, health service providers must be prepared, have strategic response plans, and implement specific measures with the ultimate goal of continuing to provide essential services while protecting patients, staff, and the public to prevent the spread of disease.1

The American Society of Nuclear Cardiology (ASNC) along with the Society of Nuclear Medicine and Molecular Imaging (SNMMI) have previously published two documents on guidance and best practices for nuclear cardiology laboratories during the COVID-19 pandemic.2,3 The first document provided recommendations when early containment measures, such as lockdowns, quarantines, and curfews were adopted. The second document (which was also authored by The International Atomic Energy Agency [IAEA] and endorsed by the Infectious Diseases Society of America) primarily dealt with reopening laboratories following the lockdown period and issues such as the prioritization of cases. Other medical societies have published similar advice documents.4,5,6 As the COVID-19 pandemic evolves, we have seen the emergence of several variants with changes in disease severity and transmissibility. Vaccination rates have increased, as have rates of post-infection immunity. However, scientists are in a race to identify how virus mutations could affect our immunity and the effectiveness of vaccines available. Cases of people experiencing break-through infections and re-infections are on the rise. On the positive side, newer oral and intravenous therapeutics have shown promise in treating patients with mild to moderate disease who are at high risk, as well as for certain high-risk patients pre-exposure.7,8,9

Around the world, there remains a disparity in availability of resources. Particularly during times of increasing infection rates, the availability of personal protective equipment (PPE), mechanical ventilation systems, testing equipment, medical staff, and hospital beds—especially ICU beds—becomes more tenuous. Given these factors, we present updated guidance for best practices in nuclear cardiology as we move from a pandemic to a chronic endemic state.

The approach to nuclear stress testing should be flexible

A major takeaway from this guidance is that there is no status quo during this pandemic. Local case rates will be variable and may change rapidly. The decision to proceed with nuclear testing, as well as with any other cardiac imaging test, and the approach should include risk/benefit assessments for both the patient as well as analysis of the impact on the local healthcare system, including risk to the medical staff. Laboratories should also continue to vary their approach based on levels of infection in the community as well as local institutional and governmental policies.4 Please see Figure 1. Table 1 lists practice recommendations that should be employed when case rates of COVID-19 are high or rising, and Table 2 lists the U.S. Centers for Disease Control definitions of levels of rates of transmission.10

Figure 1
figure 1

Recommendations: as the level of COVID-19 transmission severity increases in a community, laboratories should enhance levels of screening, PPE, social distancing practices, and hygienic measures, and perform stress testing predominantly with vasodilator pharmacologic agents rather than exercise. However, as levels of transmission are low and stable, these measures can and should be relaxed. See Table 2 for the U.S. Centers for Disease Control and Prevention definitions for the 4 levels of severity of transmission9

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Table 1 Recommended nuclear cardiology practices when COVID-19 cases are high or rapidly rising in a community
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Table 2 CDC Definitions of County Transmission Severity10
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Healthcare team wellbeing

Nuclear cardiology laboratories continue to be impacted by major staffing issues. In prior guidance statements, COVID-19 best practices focused on methods to operate safely and efficiently.2,3 During this stage of the pandemic, even greater attrition of healthcare personnel has been seen secondary to both the physical and mental stress of working during the pandemic.11,12 In addition, more recent variants, such as Omicron, are highly infectious and have the capability to incapacitate large numbers of healthcare workers resulting in acute staffing shortages and test cancellations. Not only do laboratories need to optimize safety practices to prevent transmission to and from patients and try to mitigate service disruption to allow access for needed diagnostic tests, but they also need to manage the demands upon the general working environment for the healthcare providers. Thus, some practices to enhance access and social distancing, such as extending hours of operation, may not be advisable if it will tax the already stressed or short-handed workforce. Also, even if the level of COVID-19 infections in a community is low, services may nonetheless need to be restricted if the nuclear cardiology staff is inadequate. It is imperative that healthcare workers have proper supplies of PPE and have priority for vaccinations (and comply with appropriate local COVID-19 vaccine mandates). A workflow should be established at all testing locations for enforcing masking requirements, so the primary burden does not fall on the nuclear cardiology staff. In the long run, medical facilities will likely need to be designed and built to better accommodate features of sanitation and social distancing that have been developed during this pandemic.

Guidance on exercise testing

In the pre-COVID era, the guidance generally had been to utilize exercise as the preferred stress modality for SPECT imaging when (a) the patient was able to exercise adequately, and (b) there were no electrocardiographic or medical contraindications. During the COVID-19 pandemic, this approach has often been modified to limit exercise stress in favor of pharmacological testing,2,3 reasoning that pharmacologic stress myocardial perfusion imaging (MPI) risk stratifies as well as exercise stress,13 and it likely leads to less aerosolization. To date, there has been no evidence to support an increased risk of COVID transmission to patients who underwent exercise testing. Rather, the concern has been the potential increased risk to the healthcare team. Respiratory patterns change when patients undergo treadmill or bicycle exercise testing, and data support an increased risk of droplet spread, with a potential increase in the associated risk of infection to the healthcare team in the exercise/nuclear laboratory.14,15,16 The functional assessment, hemodynamic, and electrocardiographic data obtained from exercise testing has value, and the benefit of this approach must be weighed against the potential risk to the healthcare team. In selecting a stress method, and in particular whether or not to perform exercise, we recommend consideration of several factors, including (a) availability of PPE; (b) room ventilation systems—laminar flow ventilation and appropriate air filters;17,18,19 (c) availability of pre-test COVID-19 screening; (d) current local COVID-19 infection rates; (e) current local vaccination rates and individual vaccination status (patient and staff) to help balance the localized lab approach to utilization of exercise testing.

There are clinical scenarios where exercise stress is indeed needed. For example, the utility of exercise testing is widely accepted in the management of patients with asymptomatic aortic valve stenosis, anomalous coronary arteries, myocardial bridging, and some patients with cardiac arrhythmias. In these cases, pharmacologic stress testing may not be an appropriate substitute. Moreover, vasodilator pharmaceutical stress agents are not available in some countries and add to the cost structure of the test. Where COVID-19 testing is available, appropriate PPE is worn, and other infection prevention and control policies apply, exercise testing can be performed with reasonable safety, in particular when rates of COVID-19 infections in a community are low. Patient screening can be done in several ways: questionnaires, temperature checks, and rapid antigen testing. Conditions in a community can change very quickly, and health insurance companies should give medical decision makers latitude in choosing the best testing strategy and should not mandate exercise stress.

Nuclear cardiology testing in COVID-positive patients

Myocardial perfusion imaging is generally an elective test, and for most patients who are ill with an acute COVID-19 respiratory infection, the test can be postponed until their quarantine period has ended, at the discretion of the testing physician. Those who test positive for COVID-19 and have non-urgent cardiovascular symptoms usually should have their stress test postponed until their quarantine period has ended. Emergency room and hospital-based patients should be assessed on a case-by-case basis to balance the risk of the procedure to the patient and staff versus the benefit of the information obtained. There are also patients who are COVID-19-positive (including virus asymptomatic patients), who urgently need MPI (e.g., preoperative testing prior to urgent vascular surgery), or those who need other types of nuclear cardiology tests, such as 18F-FDG metabolic imaging to evaluate possible endocarditis, device infections, myocardial viability, or cardiac sarcoidosis. In cases when a patient who has an active case of COVID-19 needs a nuclear cardiology test, laboratory-based protocols must be established, including the timing of the test (i.e., last test of the day to minimize exposure to other staff/patients), thorough cleaning and ventilation protocols, limiting the number of staff involved in the test, and use of appropriate PPE, which should include high-filtration masks (N95, FFP2, KN95, or KF94, as locally available), gloves, surgical gowns, and eye protection.20

Affirmation of previously recommended best practices for nuclear cardiology

It seems clear that some of the modifications laboratories have made to their standard operating procedures over the past two years will continue to be necessary. For example, COVID-19 screening, efforts at social distancing (including extra waiting room space), and increased use of PPE will remain very important. Also, the use of rapid and reliable COVID-19 testing, especially when prevalence rates are high, should be assessed locally on a case-by-case basis. Likewise, laboratory schedules must include time and resources for enhanced cleaning. The safety of healthcare workers and maintenance of high-quality imaging is critical. To emphasize, specific protocols that enhance social distancing and limit the exposure of patients and staff will remain important.

Certain specific testing protocols (in addition to other benefits) can result in shorter test time and, therefore, limit COVID-19 related risk. For example, stress-first/stress-only SPECT imaging can shorten the test duration in some patients by more than 50%, and two-day SPECT MPI protocols can enhance social distancing. Also, PET MPI can be performed more quickly than SPECT and is routinely performed in one location rather than having the patient move between several rooms.

Finally, in the case of SPECT-CT and PET-CT, it remains good practice to examine the CT images prior to the patient leaving the medical facility to detect possible occult COVID pneumonia as soon as possible to limit further transmission from the infected patient.

Table 3 lists best practices that should endure even in times of relatively low levels of COVID activity in a community or if COVID-19 becomes an endemic disease.

Table 3 Recommended nuclear cardiology practices regardless of whether COVID-19 cases are low, intermediate, or high in a community
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Conclusion

Much has changed since the COVID-19 pandemic was declared in March 2020. Emphasis has been placed on protecting the lives and livelihoods of people around the world. Global efforts were made to have vaccines, specific treatments, and improved access to PPE. The global pandemic is not yet over; there is considerable uncertainty about the path the pandemic will take. Scientists predict that over time COVID-19 will become endemic, and there will continue to be sporadic outbreaks in which it spirals out of control. The transition from pandemic to endemic is likely to play out differently in different parts of the world.

Nuclear cardiology laboratories have adapted in many ways and will continue to provide high-quality, patient-centered, and optimized care. This can be accomplished with a continued focus on efficient screening, implementation of infection prevention and control measures, such as physical social distancing and sharing best practices. Proper care of the healthcare workforce and dealing with staffing shortages has risen as a key focus. As we move forward, it will be important to continue to have a flexible approach, adjusting levels of caution based on local health and regulatory conditions. Many of the lessons learned during the first two years of the pandemic will continue to be valuable going forward.21

Disclosures

Dr. Al-Mallah has served as a consultant to Pfizer, Philips, and Jubilant; he has received grant support from Siemens. Dr. Bateman holds intellectual property rights in and receives royalties from Cardiovascular Imaging Technologies; he has served as a consultant to AIM, AstraZeneca, Curium, and GE Healthcare; and he has received grant support from Bracco, JDI Solutions, and GE Healthcare. Dr. Dilsizian has received grant support from GE Healthcare. Dr. Dorbala has received grant support from Pfizer, GE Healthcare, and Attalus; she serves on the advisory board for Pfizer, GE healthcare, Janssen, and Eidos; she serves on the speakers’ bureau for Ionetix. Dr. Einstein has received speaker fees from Ionetix; has received consulting fees from W. L. Gore & Associates; has received authorship fees from Wolters Kluwer Healthcare – UpToDate; and has received grants or grants pending to his institution from Attralus, Canon Medical Systems, Eidos Therapeutics, GE Healthcare, Pfizer, Roche Medical Systems, and W. L. Gore & Associates, and XyloCor Therapeutics. Dr. Ghesani serves on the advisory board for GE Healthcare; he serves on the speakers’ bureau for Blue Earth and Novartis. Dr. Gimelli serves on the advisory board for Pfizer and GE Healthcare. Dr. Phillips serves as a consultant to NovoNordisk. Dr. Skali serves as a consultant to Astellas and has received research support form ABT Associates. The following contributors have nothing relevant to disclose: Dennis A. Calnon, MD, MASNC; Suzanne F. Crews, MPA, RT, NMTCB; Maurizio Dondi, MD; Felix Keng Yung Jih, MBBS, MASNC; Diana Paez Gutierrez, MD; Randall C. Thompson, MD, MASNC.