key: cord-0748146-h2xmxwd1
authors: Rali, Aniket S; Ranka, Sagar; Shah, Zubair; Sauer, Andrew J
title: Mechanisms of Myocardial Injury in Coronavirus Disease 2019
date: 2020-05-25
journal: Card Fail Rev
DOI: 10.15420/cfr.2020.10
sha: 91590e22b6d261f71d1756047a8dc32fb0a68f9e
doc_id: 748146
cord_uid: h2xmxwd1

Coronavirus disease 2019 (COVID-19) predominantly presents with symptoms of fever, fatigue, cough and respiratory failure. However, it appears to have a unique interplay with cardiovascular disease (CVD); patients with pre-existing CVD are at highest risk for mortality from COVID-19, along with the elderly. COVID-19 contributes to cardiovascular complications including arrhythmias, myocardial dysfunction and myocardial inflammation. Although the exact mechanism of myocardial inflammation in patients with COVID-19 is not known, several plausible mechanisms have been proposed based on early observational reports. In this article, the authors summarise the available literature on mechanisms of myocardial injury in COVID-19.

public health predictive models, these numbers are expected to continue to rise in the upcoming weeks, leading to a nationwide shortage of hospital beds and especially intensive care unit (ICU) beds.

Owing to its predominantly respiratory manifestations, including acute respiratory distress syndrome (ARDS), one of the treatment modalities that is expected to run short is mechanical ventilators.

A case series of 138 COVID-19 patients from Wuhan, China showed that a total of 36 (26%) patients required ICU level care, of whom 22 (61%) developed ARDS and 17 (47.2%) required invasive mechanical ventilation. 1 Other retrospective analyses have reported similarly that 20-31% of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) patients develop ARDS and require ICU care. [2] [3] [4] Therefore, it is critical that we explore the utility and safety of other forms of respiratory support devices, including high-flow nasal cannula oxygenation (HFNCO) in the treatment of acute respiratory failure. In the above mentioned case series from China, 4 (11%) of the patients admitted to the ICU were successfully treated with HFNCO ( Figure 1 ). 1 Similarly, in other case series of 191 COVID-19 patients, 41 (21%) were treated with HFNCO (33 in ICU and 8 in non-ICU). 4 We present a case of a SARS-CoV-2-positive patient with acute respiratory failure who was successfully treated with HFNCO. We also discuss the mechanisms of action, clinical effects, and available literature on the efficacy and safety of HFNCO, including the risk of aerosolising SARS-CoV-2 particles.

A 51-year-old man presented to the emergency department (ED) with a 1-week history of worsening dyspnoea, fevers and non-productive cough in light of negative influenza testing at his primary care physician's office. The patient had no travel history, but reported contact with international clients through his work.

His vital signs at the time of presentation were oral temperature of 99.7°C, heart rate of 105 BPM, respiratory rate of 35, blood pressure of 113/99 mmHg and oxygen saturation of 80% of room air. His physical examination was significant for respiratory distress, with use of accessory muscles and crackles in bilateral lung bases upon auscultation.

Chest X-ray showed bilateral multifocal hazy interstitial opacities ( Figure 2) . Respiratory viral panel, including influenza, was negative, but a SARS-CoV-2 polymerase chain reaction test that was sent while the patient was in the ED returned positive on day 4.

The patient was initially admitted to the progressive care unit under droplet and contact precautions pending SARS-CoV-2 test results, and ceftriaxone and azithromycin were initiated for presumed communityacquired pneumonia. On day 3, his hypoxic respiratory failure worsened, requiring high-flow nasal cannula at 40 l/min and 90% fractional inspired oxygen, (FiO 2 ) and he was transferred to the medical ICU. The infectious diseases team was consulted and the patient commenced a 5-day course of lopinavir/ritonavir and hydroxychloroquine once the SARS-CoV-2 test was confirmed to be positive. Over the next 5 days, the patient was gradually weaned to room air. When he was haemodynamically stable, he was discharged with instructions to continue self-isolation at home for 14 additional days.

Our report discusses a COVID-19 patient who presented with acute respiratory failure with moderate ARDS, in whom endotracheal intubation was prevented; the patient was successfully treated on 

Aniket S Rali, Krishidhar R Nunna, Christopher Howard, James P Herlihy and Kalpalatha K Guntupalli Therefore, patients with hypercarbia, in addition to hypoxaemia, gain benefit from HFNCO, not only through reduction in anatomic dead space but also through reduced CO 2 production via lowered metabolic demand.

Third, HFNCO further reduces the work of breathing by optimally conditioning the delivered gas by warming and humidifying it to physiological conditions. This spares the body the energy cost of warming and humidifying inspired gas. Warm humid gas is also associated with better conductance and pulmonary compliance compared to dry and cooler gas. It also improves mucociliary function, thereby facilitating secretion clearance, decreasing risk of atelectasis and improving the ventilation/perfusion ratio and oxygenation. One potential concern that has been raised about the use of HFNCO in COVID-19 patients is that it could aerosolise the respiratory tract pathogen. Using evidence from several recently published studies, the WHO concluded that HFNCO does not create widespread dispersion of exhaled air, and therefore, should be associated with low risk of transmission of respiratory viruses. 9 They do recommend wearing a standard medical face mask if a medical provider is within 2 m of the patient. However, a newer study showed that the distance of droplet dispersion from coughing increases by an average of 0.42 m with highflow nasal cannula, and travelled further than the WHO-recommended 2-m safe exclusion zone. 10 Based on this evidence, at our institution we ensure that COVID-19 patients on HFNCO are at the least in singleoccupancy rooms with either negative pressure or high-efficiency particulate air filtration systems, and that all our healthcare workers caring for those patients wear full airborne personal protective equipment (i.e. N95 masks or equivalent, gown, gloves, goggles, hair covers and face shields).

HFNCO is an effective treatment modality for COVID-19-associated acute respiratory failure. Particularly in patients with mild to moderate ARDS and in negative pressure rooms, it could be a viable initial alternative to mechanical ventilation. 

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