Editorial commentary: Cardiovascular imaging in COVID-19: Focus on safety, value, and clinical relevance

The novel coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has disrupted the global order. The disease has affected the health of millions and has disrupted billions of lives due to its social, economic, and psychological impact. COVID-19 and cardiovascular diseases have shown a bidirectional relationship. Underlying pre-existing cardiovascular risk factors and disease appear to be at an increased susceptibility and severity of COVID-19 [1,2]. In addition, de-novo cardiovascular involvement in various forms (type II myocardial infarction, arrhythmia, myocarditis, heart failure, and venous thromboembolism) is reported in a high proportion of patients with severe COVID-19, which is also associated with adverse outcomes [3], [4], [5]. While the exact mechanisms of cardiovascular involvement with COVID-19 are not well understood, several potential mechanisms such as direct toxicity through the myocardial viral invasion (myocarditis), angiotensin-converting enzyme-2 (ACE-2) receptor-mediated myocardial and endothelial injury, microvascular dysfunction and thrombosis as well as cytokine release syndrome (mainly IL-6 mediated) and stress cardiomyopathy due to the imbalance in myocardial supply and demand have been implicated [6,7].

While several studies have shown myocardial injury in patients with severe COVID-19, based upon elevation in myocardial necrosis biomarker [1,6,8], performing an extensive cardiac workup in patients with COVID-19 is challenging not just because of their clinical status but also due to the need of limiting exposure of health care personnel [9]. Non-invasive imaging remains the backbone for the diagnosis and risk stratification as well as to guide the management of cardiovascular disease [8,10,11]. The review by Citro et al. [12] in this issue of the Journal describes the role of various imaging modalities for the identification of various COVID-19 associated cardiovascular manifestations as well as how to efficiently utilize these tests during the pandemic to minimize the risk of infection transmission to healthcare workers and patients.

The authors provide a concise summary of practically useful recommendations based upon the evolving knowledge of COVID-19 as well as the mechanisms of cardiovascular system involvement and its implications. While the review article by Citro et al. [12] has mainly focused on cardiovascular imaging in patients with COVID-19, cardiovascular imaging amidst the pandemic, even in patients without COVID-19, needs thoughtful consideration and special attention [5]. The role of multimodality imaging in the context of COVID-19 is important on several fronts i) for diagnosis and risk stratification as well as to guide management of acute COVID-19 associated cardiovascular issues, ii) for assessment of non-COVID associated cardiovascular problems during the pandemic, iii) to study the long-term cardiovascular consequences of those affected with COVID-19, iv) screening and surveillance imaging of the high-risk patient population, e.g., patients with cancer undergoing potentially cardiotoxic chemotherapy for guideline-recommended surveillance [13]. Various societal guidelines and position papers have outlined the critical role of imaging and have laid out management pathways concerning cardiovascular care [13], [14], [15].

The authors describe that in COVID-19 patients with abnormal cardiac biomarkers or cardiovascular symptoms, a 2-Dimensional transthoracic echocardiogram (2D-TTE) used as a point of contact ultrasound (POCUS) is the first-line imaging modality given that it is an easily available, portable, and high-value, low-cost intervention [12,15]. A dedicated team of sonographers and machines in the emergency room and COVID-19 designated units can help diagnose and differentiate various common cardiovascular conditions in patients with COVID-19 such as acute coronary syndrome (ACS) with wall motion abnormalities, type II myocardial infarction due to supply-demand mismatch, or stress cardiomyopathy [5]. It can also be utilized to assess left ventricular function and differentiate non-cardiogenic shocks from cardiogenic. Acute pulmonary embolism, which is reported in a significant proportion of critically ill patients with COVID-19, may lead to right ventricular dysfunction, and TTE may help prompt diagnosis as well as prognostication [11].

A recent multicenter study showed that among patients with myocardial injury as noted by elevated cardiac troponin (cTn) during COVID-19 illness, any cardiac structural abnormality such as left ventricular wall motion abnormalities, global left ventricular dysfunction, left ventricular diastolic dysfunction, right ventricular dysfunction, and pericardial effusions noted on TTE was associated with a significantly elevated risk of in-hospital mortality [8]. These findings would argue about routine testing of cardiac biomarkers as well as cardiovascular imaging, at least TTE in all patients with an elevated cardiac biomarker. However, given the rapidly increasing number of COVID-19 associated hospitalizations, the healthcare infrastructure is facing an unprecedented burden on available resources. Additionally, elevated cTn in most critically ill patients is secondary to supply-demand mismatch, and they may have underlying pre-existing cardiovascular disease, which may represent adverse prognosis. Cardiac imaging under these circumstances may not provide any additional actionable information [16]. Universal imaging with TTE or other modalities, while may be tempting, is neither practical nor necessary. Judicious utilization, focused rather than detailed echocardiographic examination, and utilization of appropriate personal protective equipment (PPE) are crucial in minimizing infection transmission from proven or suspected cases of COVID-19, thus balancing patient care and safety [17].

Trans-esophageal echocardiogram (TEE) is a potentially aerosol-generating procedure that necessitates full PPE, and should be avoided without a compelling indication in suspected or proven COVID-19 cases [14]. Alternative imaging modalities should be considered when appropriate. For example, cardiac computed tomography (CT) scan could replace the need for TEE in cases of atrial fibrillation requiring cardioversion for ruling out left atrial appendage clot. While hyperinflammatory response seen with COVID-19 may lead to coronary plaque destabilization and thrombosis leading to ACS, as alluded to above; more often, cTn elevation in COVID-19 patients is secondary to supply-demand ischemia [16]. Coronary computed tomography (CT) angiography has a high negative predictive value to rule out obstructive coronary artery disease. Instead of invasive cardiac catheterization, it could be considered as its rapid acquisition time helps minimize exposure to COVID-19(5). In fact, chest CT (with different sequencings) can be used as a one-stop-shop to evaluate pneumonia, pleural effusions, pulmonary embolism, and even obstructive coronary artery disease.

A prospective study by Puntmann et al. [18] from Germany showed that a significant proportion of patients (60%) had myocardial inflammation detected by cardiac magnetic resonance imaging (CMR) likely due to myocarditis. However, the clinical implication of this remains unknown. Due to its high accuracy for LVEF assessment and the ability for myocardial tissue characterization, including identification of inflammation, fibrosis, and scar burden, CMR is typically a necessary diagnostic test in patients with suspected myocarditis [19]. However, despite the relatively high prevalence of possible myocarditis in one study, in the context of COVID-19, it should be used cautiously and as clinically indicated rather than for screening purposes in all-comers. When needed, abbreviated exams tailored to the specific clinical question should be performed due to decreased exposure time and required down-time of the scanner in between studies for decontamination [20]. When unavailable or difficult to obtain, a cardiac CT scan with myocardial late iodine enhancement (LIE) to detect areas of myocardial fibrosis, inflammation, or diffuse ischemia can be considered, which may help to avoid the need for time-consuming CMR.

Multimodality cardiovascular imaging will remain instrumental in the deceleration phase of this pandemic as well. Cardiovascular imaging will play a pivotal role to better understand the long-term cardiovascular consequences of COVID-19, particularly in those who may have had COVID-19 associated myocarditis, have residual cardiovascular manifestations, and potentially for those who need to resume high-intensity activity, such as professional athletes.

Many non-urgent but required cardiovascular imaging tests for non-COVID-19 associated cardiovascular issues have been significantly delayed due to the pandemic, which may have a long-term adverse impact. As we "re-open", we will have to identify and prioritize high-risk patients so the limited resources can be utilized wisely. One such group is patients undergoing potentially cardiotoxic anti-neoplastic therapy where cardiac surveillance imaging is typically required [21,22]. We will also have to learn to utilize other markers of cardiotoxicity, such as cardiac biomarkers, in case of limited imaging-resource availability. Vigilant follow-up and thorough clinical examination would also likely limit the need for repeat imaging in only selected cases. Additionally, stringent protective measures such as universal testing for SARS-CoV-2 in all patients before any invasive or aerosol-generating procedure regardless of symptoms, masking policy for everyone including patients at all times while in health care facilities, hand hygiene, and use of appropriate PPE by healthcare providers should be continually followed.

Over time, we have relied increasingly on non-invasive imaging tests, which has revolutionized cardiovascular care by enabling us to make a timely diagnosis and individualize the management. While this is helpful in most instances, we as a medical community have also overused such diagnostic testing leading to a plethora of incidental findings of undetermined significance [23]. Amidst the pandemic, it is now more critical than ever before to judiciously and rightfully use these tests to avoid under and overdiagnosis and minimize the risk of bidirectional infection transmission.