Post-COVID-19 illness trajectory: a multisystem investigation.

Background: The pathophysiology and trajectory of multiorgan involvement in post-COVID-19 syndrome is uncertain. Methods: A prospective, multicenter, longitudinal, cohort study involving post-COVID-19 patients enrolled in-hospital or early post-discharge (visit 1) and re-evaluated 28-60 days post-discharge (visit 2). Multisystem investigations included chest computed tomography with pulmonary and coronary angiography, cardiovascular and renal magnetic resonance imaging, digital electrocardiography, and multisystem biomarkers. The primary outcome was the adjudicated likelihood of myocarditis. Results: 161 patients (mean age 55 years, 43% female) and 27 controls with similar age, sex, ethnicity, and vascular risk factors were enrolled from 22 May 2020 to 2 July 2021 and had a primary outcome evaluation. Compared to controls, at 28-60 days post-discharge, patients with COVID-19 had persisting evidence of cardio-renal involvement, systemic inammation, and hemostasis pathway activation. Myocarditis was adjudicated as being not likely (n=17; 10%), unlikely (n=56; 35%), probable (n=67; 42%) or very likely (n=21; 13%). Acute kidney injury (odds ratio, 95% condence interval: 3.40 (1.13, 11.84); p=0.038) and low hemoglobin A1c (0.26 (0.07, 0.87); p=0.035) were multivariable associates of adjudicated myocarditis. During convalescence, compared to controls, COVID-19 was associated with worse health-related quality of life (EQ5D-5L) (p<0.001), illness perception (p<0.001), anxiety and depression (p<0.001), physical activity (p<0.001) and predicted maximal oxygen utilization (ml/kg/min) (p<0.001). These measures were associated with adjudicated myocarditis. Conclusions: The illness trajectory of COVID-19 includes persisting cardio-renal inammation, lung damage and hemostasis activation. Adjudicated myocarditis occurred in associated with in physical and psychological convalescence. and, third, adjudicated myocarditis post-COVID-19 associates with persisting impairments in health status, physical and psychological wellbeing. Disease mechanisms were investigated using multisystem imaging and biomarkers and their changes over time. Health status and physical function were serially assessed using validated patient reported outcome measures. This study involved a prospective, observational, multicenter, longitudinal, secondary care cohort design to assess the time-course of multiorgan injury in survivors of COVID-19 during convalescence. Clinical information, a 12-lead digital ECG, blood and urine biomarkers, and patient reported outcome measures were acquired at enrolment (visit 1) and again during convalescence, 28–60 days post-discharge (visit 2). Chest computed tomography (CT), including pulmonary and coronary angiography, and cardio-renal MRI were acquired at the second visit. myocarditis included relevant clinical ndings and test results (Supplement) 17 . Positive clinical ndings included chest pain, pericarditic or pseudo-ischemic in nature, new onset breathlessness, subacute/chronic breathlessness, palpitations, unexplained arrhythmia, syncope, aborted sudden cardiac death, or unexplained cardiogenic shock. Positive test ndings included 1) ECG features, 2) elevated troponin I (sex-specic >99 th percentile upper reference limit: female: >16 ng/L, male: >34 ng/L; Abbott Architect STAT TnI assay); 3) functional and structural abnormalities on cardiac imaging (echocardiography, angiography, or MRI), and 4) tissue characterization MRI, including myocardial edema and late gadolinium enhancement with a distribution in alignment with the modied Lake Louise diagnostic criteria for myocarditis 29 . Acute and chronic myocardial pathology can be identied, discriminated, and quantied using MRI. associate of worse physical and mental health post-COVID-19, cardio-renal involvement could be considered a therapeutic target (endpoint) in clinical trials to prevent post-COVID-19 syndrome. The RECOVERY Trial is currently investigating the effects of immunomodulatory therapies in acute COVID-19, including baricitinib and dimethyl fumarate, and the sodium-glucose cotransporter-2 inhibitor, empagliozin, which reduces the progression of kidney disease and lower rates of clinically relevant renal events in patients with type 2 diabetes at high cardiovascular risk 48

Patients who received hospital care for COVID-19, with or without admission, and were alive, were prospectively screened in real time using an electronic healthcare information system (TrakCare®, InterSystems®, USA) and daily hospital reports identifying inpatients with laboratory-positive results for COVID-19.

Eligibility criteria
The inclusion criteria were: (1) age ≥18 years old; (2) history of an unplanned hospital visit e.g., emergency department, or hospitalization >24 hours for COVID-19 con rmed by a clinical diagnosis, laboratory test (e.g., polymerase chain reaction (PCR)), and/or a radiological test (e.g. CT chest or chest radiograph); (3) ability to comply with study procedures; and (4) ability to provide written informed consent. The imaging results were reported by accredited radiologists according to contemporary, national guidelines 20 .

Screening
A screening log was prospectively completed. The reasons for being ineligible, including lack of inclusion criteria and/or presence of exclusion criteria, were recorded.

Diagnosis of COVID-19
A diagnosis of COVID-19 was based on either laboratory evidence of SARS-CoV-2 infection using a PCR test (Roche Cobas 6800 or Seegene SARS-CoV-2 PCR) on a biospecimen or a radiological and clinical diagnosis of COVID-19 but biospecimen negative 21 .

Diagnosis of myocardial injury
The diagnosis of myocardial injury aligned with the Fourth Universal De nition of Myocardial Infarction 22 . Troponin I was measured in hospitalized patients using the Abbott Architect STAT TnI assay (sex-speci c >99 th percentile upper reference limit: female: >16 ng/L, male: >34 ng/L.

Diagnosis of acute kidney injury
Acute kidney injury (AKI) was de ned as any stage of AKI (1-3) during COVID-19 hospitalization using categorization with the Kidney Disease: Improving Global Outcomes (KDIGO) criteria (Supplement) 23 .

Research schedule
The protocol involved two visits. The rst visit involved informed consent and baseline assessments during the initial hospitalization, or as soon as possible after discharge. The second visit occurred 28-60 days post-discharge. This window was positioned to re ect the convalescent phase and give su cient scope to schedule the patients.
The procedures involved prospective collection of clinical data and a time-course of research investigations. Clinical data included demographics, medical and cardiovascular history, ndings from clinical examinations, laboratory and radiological tests, cardiology tests (including an electrocardiogram (ECG) and an echocardiogram if available) and treatment. The research investigations at both visits included blood and urine samples, a 12-lead digital ECG (Beneheart R3, Mindray, Huntingdon, UK), health status questionnaires, and assessments of adverse events (Supplement). Heart, lung, and kidney imaging were acquired at the second visit. Electrocardiology SARS-CoV-2 infection and treatment may cause alterations in heart rate and rhythm, and ventricular repolarization. The changes may be speci c for myocarditis e.g., concave ST-elevation, or non-speci c e.g., ventricular arrhythmias. Digital ECGs were acquired, de-identi ed and provided to the University of Glasgow Electrocardiology Core Laboratory for automated analysis and adjudication. The ECG features of myopericarditis were prede ned according to contemporary criteria 17 .

Biomarkers
Blood and urine samples were collected at enrolment (visit 1) and 28-60 days post discharge (visit 2). Circulating biomarkers of cardiac injury (troponin I, Nterminal (NT)-pro hormone brain natriuretic peptide (NT-proBNP), in ammation (C-reactive protein, ferritin), thrombosis (TCT ratio, D-Dimer, brinogen, Factor VIII, antithrombin, protein C, protein S), endothelial activation (von Willebrand factor (vWF):GP1bR, VWF:Ag) and renal function (serum creatinine, glomerular ltration rate (GFR) was estimated using the Chronic Kidney Disease Epidemiology (CKD-EPI) equation 24 ) and urinary albumin: creatinine ratio), and their changes over time, were investigated. The measurements were undertaken in a central laboratory, blinded to the other clinical data. The methodology is described in the Supplement.
Multimodality imaging CT A 320-detector CT scanner (Aquilion ONE, Canon Medical Systems Corp.) provided full heart coverage within a single heartbeat. Intravenous metoprolol was used where required to control the heart rate (target 60 beats/min) and sublingual glyceryl trinitrate was given to all patients immediately before the scan acquisition. An initial low radiation dose helical scan of the thorax was acquired for comprehensive assessment of the lungs. A contrast bolus timing scan was acquired to provide information on cardiopulmonary transit times. Non-contrast and contrast-enhanced angiographic breath-hold ECG-gated volumes were acquired and timed for optimum pulmonary and systemic arterial (coronary) opaci cation. Patients with severe renal dysfunction underwent noncontrast CT.
Coronary CT angiography provided information on the presence and extent of coronary calci cation (calcium score), coronary artery disease, and whether any coronary artery disease was obstructive ( ow-limiting) including the Coronary Artery Disease -Reporting and Data System (CAD-RADS) score 25 . The functional signi cance of coronary artery disease was evaluated using fractional ow reserve CT (FFR CT ; HeartFlow, Redwood City, CA). A FFR CT ≤0.80 de ned obstructive coronary artery disease, taking the lowest value in the vessel. FFR CT measurements were taken at prespeci ed points using standard coronary segment de nitions as a reference 26 . Median FFR CT values were calculated for the left anterior descending, circum ex, and right coronary arteries, respectively, in combination with subsidiary vessels (i.e., diagonal arteries, obtuse marginal arteries). Patient-level FFR CT values included all these coronary arteries.
Pulmonary vascular imaging assessed arterial thrombus (embolism) 27 . CT was used to delineate pulmonary features associated with COVID infection e.g., atelectasis, reticulation and/or architectural distortion, ground-glass opacity, and pre-existing lung damage e.g., emphysema. Cardiac and extra-cardiac incidental ndings were reported and managed according to local standards of care.

Cardiovascular MRI
Cardiovascular MRI was undertaken to measure heart structure and function and assess for persisting evidence of myocardial injury and/or myocardial infarction using multi-parametric techniques 28 . MRI was acquired in a single reference site for all patients using a research-dedicated 3.0 Tesla (3T) scanner (MAGNETOM Prisma, Siemens Healthineers, Erlangen, Germany) with two 18-channel surface coils placed anteriorly and a 32-channel spine coil placed posteriorly. All patients underwent protocol-directed MRI in the convalescent phase, 28-60 days after discharge. The scan protocol included cine-imaging of cardiac anatomy and function and myocardial tissue characterization using multiparametric techniques. They included 1) mapping myocardial native longitudinal relaxation time (T1 in milliseconds) using the modi ed Look-Locker inversion recovery technique (T1-mapping) before and after intravenous administration of gadolinium contrast media (0.15 mmol/kg of Magnevist, Bayer Healthcare), 2) mapping transverse relaxation time (T2 in milliseconds), 3) rst pass contrast-enhanced perfusion and 4) late gadolinium-enhancement imaging. Speci c details on the MRI protocol are provided in the Supplement.
The expert consensus recommendations for the MRI diagnostic criteria of non-ischemic myocardial in ammation (modi ed Lake Louise criteria) were used to diagnose de nite myocardial in ammation (abnormal T2 and T1 (native T1, late gadolinium enhancement or extracellular volume)) or probable myocardial in ammation (abnormal: T2 or T1) 17,29 (Supplement). Reference ranges derived from the UK Biobank were used to interpret cardiac structure and function 30 , and contemporary local reference ranges speci cally derived using the 3T MRI scanner (MAGNETOM Prisma) were used to de ne thresholds for localized abnormalities in myocardial T1-and T2-relaxation times. To limit selection bias, patients with severe renal dysfunction (GFR <45 ml/kg/m 2 ) were not excluded. They were eligible for MRI with or without contrast media according to the site Radiology protocol.

Renal MRI
Multi-parametric renal MRI included anatomical imaging and tissue characterization by measurement of native T1 and T2. The volume (ml), and native T1 (ms) and T2 (ms) in regions of interest obtained within the cortex and medulla of each kidney were recorded, and the averaged value of these parameters for both kidneys was then determined. Corticomedullary differentiation re ects a difference in tissue contrast on T1-weighted imaging due to a shorter T1 relaxation time of the cortex relative to the medulla, this being attributed to differences in water content between the two tissues 31,32 . Corticomedullary differentiation, reported here as a ratio of T1 cortex divided by T1 medulla 32 , may diminish in kidney disease 31 .

Blinding
The patients and the outcome assessors were blinded. Outcome assessments, including laboratory, MRI and CT analyses, and endpoint adjudication were undertaken by blinded researchers. The patients completed the health status questionnaires before undergoing the scans and they were unaware of the test results.

Primary outcome
The prede ned primary outcome was a diagnosis of myocarditis (myocardial in ammation), an endotype of acute myocardial injury.
The diagnostic criteria for myocarditis included relevant clinical ndings and test results (Supplement) 17 . Positive clinical ndings included chest pain, pericarditic or pseudo-ischemic in nature, new onset breathlessness, subacute/chronic breathlessness, palpitations, unexplained arrhythmia, syncope, aborted sudden cardiac death, or unexplained cardiogenic shock. Positive test ndings included 1) ECG features, 2) elevated troponin I (sex-speci c >99 th percentile upper reference limit: female: >16 ng/L, male: >34 ng/L; Abbott Architect STAT TnI assay); 3) functional and structural abnormalities on cardiac imaging (echocardiography, angiography, or MRI), and 4) tissue characterization MRI, including myocardial edema and late gadolinium enhancement with a distribution in alignment with the modi ed Lake Louise diagnostic criteria for myocarditis 29 . Acute and chronic myocardial pathology can be identi ed, discriminated, and quanti ed using MRI.
Myocarditis was clinically suspected if at least 1 clinical nding and at least 1 diagnostic test criterion from different categories, in the absence of: (1) angiographically detectable coronary artery disease (coronary stenosis ≥ 50%); (2) known pre-existing cardiovascular disease or extra-cardiac causes that could explain the syndrome (e.g., valve disease, congenital heart disease, hyperthyroidism, etc.). Suspicion increases with a rising number of ful lled criteria. If the patient was asymptomatic, at least 2 diagnostic criteria were required.
Adjudication of the primary outcome A diagnosis of myocarditis is susceptible to confounding through ascertainment bias. Recent studies in COVID-19 have not implemented the modi ed Lake Louise diagnostic criteria 18, 19 . Accordingly, we pre-speci ed an adjudication procedure for the primary outcome, involving a panel of cardiologists with specialty accreditation. The reviews were undertaken according to a prespeci ed charter.
Consultant cardiologists (n=14) who were independent of the research team were invited as assessors. They were initially provided with information on the Each cardiologist independently assessed the clinical data, including the medical history, biomarkers, ECG, and radiology reports for the CT chest, CT pulmonary angiogram, coronary CT angiogram, and cardiac MRI. Deidenti ed source clinical data e.g., scan images, were made available on request. The cardiologists determined the likelihood (not likely / unlikely / probable / very likely) of myocardial in ammation (myocarditis). The nal diagnosis was based on the median likelihood based on the adjudications of 5 cardiologists. Their determinations were also categorized in binary form (not/unlikely = no; probable/very = yes).

Secondary outcomes
The differential etiology of myocardial injury/in ammation was adjudicated as a secondary outcome. The potential endotypes were: The endotypes of acute myocardial injury, including the type of myocardial infarction according to the 4 th Universal De nition of MI 22 , and myocarditis (myocardial in ammation, ischemia or stress cardiomyopathy) 17,29 , were secondary outcomes.

Renal outcomes
Renal function was assessed using convalescent eGFR (CKD-EPI 24 ) and albuminuria. Multi-parametric renal MRI at 28-60 days provided information on renal parenchymal disease.
Health status and patient reported outcome measures Questionnaires were completed by participants at enrolment (visit 1) and 28-60 days after the last episode of hospital care (visit 2), blind to the other research data. Self-reported health status was assessed using the generic EuroQOL EQ-5D-5L questionnaire and the Brief Illness Perception Questionnaire (Brief-IPQ) 33,34 . The Patient Health Questionnaire-4 (PHQ-4) was utilized to assess for anxiety and depressive disorders 35 . The Duke Activity Status Index (DASI) was used to assess predicted maximal oxygen utilization (ml/kg/min), a measure of aerobic capacity, and functional capacity, a higher score re ects greater physical function 36 . The International Physical Activity Questionnaire -Short Form (IPAQ-SF) measures the types and intensity of physical activity and sitting time that people do as part of their daily lives. The score re ects total physical activity in metabolic equivalent minutes per week 37 .

Longitudinal follow-up
The participants were invited to give consent for clinical outcome assessment during follow-up using electronic health record linkage without direct contact.

Statistics
The statistical analyses were pre-de ned in a Statistical Analysis Plan.

Sample size calculation
The primary outcome was myocarditis (myocardial in ammation), and the primary analysis determined the proportion of patients with the primary outcome by visit 2. The likelihood of myocarditis was determined based on the median likelihood from the clinical adjudication committee. To detect an association between a history of pre-existing cardiovascular disease and incident myocardial in ammation (myocarditis), we assumed a 25% prevalence of prior cardiovascular disease in the study population, and the incidence of myocardial in ammation in those with/without prior cardiovascular disease to be 33% and 10%, respectively 38 . To have 80% power to detect this difference we calculated that 140 participants (35 with cardiac problems, 105 without) with complete data would be required. Anticipating that 10-15% of the participants may have incomplete imaging e.g., artefact or claustrophobia, the target sample size was 160 to complete the imaging visit.
Cardiovascular disease status was prespeci ed and de ned by (1) a prior history of cardiovascular disease, and (2)

Ethics
The study was approved by the UK National Research Ethics Service (Reference 20/NS/0066).

Sources of Funding
This was an investigator-initiated clinical study that was funded by the

Data and code availability
The datasets that support the ndings of this study are available from the corresponding author upon reasonable request. Statistical code will be made available by the corresponding author upon reasonable request.

Results
One thousand three hundred and six patients were screened between 22 May 2020 and 16 March 2021 and 267 patients provided written informed consent.
The ow diagram is shown in Figure 1 and clinical cases are illustrated in the Supplement.
One hundred and sixty-one patients were evaluated at 28-60 days after the last episode of hospital care. Their average age was 55 years, 88% were white, 43% were female, 47% had a history of cardiovascular disease or treatment, 40% were in the highest quintile of deprivation and 22% were healthcare workers (Table   1 and Supplement). Clinical disease severity scores are described in Table 1. Two (1.2%) patients had received a single dose of SARS-CoV-2 vaccine prior to hospitalization (Supplement, Table 2). Regarding COVID-19 therapy, 68.9% received oxygen, 55.3% received steroids, 26.1% received antiviral drug therapy, 19.3% received non-invasive respiratory support and 8.7% received invasive ventilation.

Comparison with controls
Twenty-seven control patients with similar age, sex, ethnicity, and cardiovascular risk factors underwent the same research procedures during a single visit between 13 April to 2 July 2021. Their characteristics are described in Table 1. Compared to controls, COVID-19 patients had multisystem differences in keeping with acute illness.

Multisystem investigations: comparisons with controls
In post-COVID-19 patients, compared to controls, the heart, lung and kidney imaging, electrocardiography and multisystem biomarkers revealed multiple persisting abnormalities (Table 2).
At 28-60 days post-discharge (visit 2), CT chest abnormalities were common: 44.7% had ground glass opacities and/or consolidation, 23.9% had ≥20% of the total lung area abnormal by visual estimation and 3.3% had pulmonary arterial thrombus. In the post-COVID-19 patients, the minimum patient-level FFR CT was lower than in the control group (minimum FFR CT : 0.80 (0.10) vs. 0.85 (0.08); p<0.001) consistent with ow-limiting coronary artery disease. MRI revealed persisting differences for left and right ventricular ejection fraction, contractility (strain), volumes, myocardial tissue characteristics, including late gadolinium enhancement in one in ve patients mainly with a non-ischemic distribution, increased myocardial extracellular volume and pericardial thickening ( Table 2).
Circulating concentrations of C-reactive protein, ferritin, D-Dimers, brinogen, Factor VIII, and von Willebrand factor were higher in post-COVID-19 patients at enrolment compared to controls consistent with hemostatic pathway activation (Table 2). At 28-60 days post-discharge, Factor VIII concentration remained high. Circulating concentrations of NT-proBNP were higher in COVID-19 patients at enrolment and 28-60 days post-discharge. Urine albumin: creatine ratio and eGFR were not statistically different between the groups.

Multisystem phenotyping and adjudicated myocarditis
Electrocardiology Premature ventricular contractions associated with the likelihood of myocarditis (Table 2).

CT chest, coronary and pulmonary angiography
Myocarditis did not appear to be associated with the extent or nature of lung involvement or coronary artery disease (Table 2).

Cardiovascular magnetic resonance imaging
Evidence was found of associations between the adjudicated likelihood of myocarditis and reduced left ventricular ejection fraction in females, myocardial in ammation, extracellular volume, late gadolinium enhancement (non-ischemic distribution) and the diagnostic criteria (Lake Louise) for myocardial in ammation (Table 2). Distinct patterns of myocardial pathology revealed by late gadolinium enhancement imaging are shown in the Supplement.
Renal magnetic resonance imaging The adjudicated likelihood of myocarditis was associated with acute kidney injury during the initial admission. The average renal medulla T1 (ms), an imaging marker of in ammation in the left and right kidneys, associated with adjudicated myocarditis. No differences were observed for the averaged renal volumes, cortex tissue characteristics (T1, T2 ms), or renal function at 28-60 days.
Biochemical and hematological markers At 28-60 days, protein S was inversely associated with the adjudicated likelihood of myocarditis. We found no other evidence of associations between the adjudicated myocarditis and biochemical and hematological markers of in ammation, hemostatic pathway activation, myocardial injury, or left ventricular dysfunction ( Table 2).

Adjudicated cause of myocarditis
The etiology of myocardial in ammation was also adjudicated. SARS-COV-2 myocarditis was determined as being probable (66.7%) or very likely (33.3%) in all patients with adjudicated myocarditis (p<0.001) (Supplement, Table 3). Impaired myocardial blood ow as a stressor of in ammation was determined as probable in 6 (6.8%) patients with myocarditis adjudicated to be either probable or very likely (p<0.001).

Multivariable associates of adjudicated myocarditis
Univariate and multivariable associations between selected demographic and clinical measures at baseline (visit 1) and an adjudication of myocarditis being probable or very likely were assessed with logistic regression models ( Health status Compared to controls, at enrolment and 28-60 days post-discharge, post-COVID-19 patients had lower health-related quality of life, enhanced illness perception, higher levels of anxiety and depression, lower levels of physical activity and lower predicted maximal oxygen utilization (ml/kg/min) ( Table 4).

Serious adverse events
One patient died following consent, before discharge from hospital. A further patient died within 60 days of discharge (prior to visit 2). The causes of death and hospital readmission are listed in the Supplement.

Discussion
This prospective multicenter study characterized the illness trajectory of patients who survived hospitalization for COVID-19 during community convalescence. The study provided serial measurements of multisystem pathology coupled with patient-reported health status and aerobic exercise capacity.
Our results bridge a knowledge gap between post-COVID-19 syndromes and objective evidence of disease. We found that the illness trajectory of post-COVID-19 syndrome involved hemostatic pathway activation initially, including increases in circulating concentrations of brinogen and factor VIII and a reduction in  (Table 2). Notwithstanding, the etiology of myocarditis determined by the adjudication committee was predominately SARS-CoV-2 infection and less commonly, myocardial ischemia due to coronary artery disease (Supplement, Table 3).
Distinct from controls, one in ve post-COVID-19 patients had imaging evidence of myocardial brosis indicative of distinct disease mechanisms, including myocarditis, microvascular thrombosis, myocardial infarction, and pre-existing scar (Supplement). Adjudicated myocarditis was also associated with premature ventricular contractions, myocardial brosis, pericardial thickening, and mild differences in left and right ventricular systolic function. On the other hand, hemoglobin A1c (%) was the only baseline characteristic associated with adjudicated myocarditis, but in the opposite direction to what may be expected, and so requiring validation in other cohorts. The mechanism may involve systemic in ammation leading microangiopathic hemolytic anemia and reduced red cell survival 42 , although the lack of association with haptoglobin (Table 2) and other hematological parameters (Supplement, Table 1) does not support this possibility in our population. Reverse causality and residual confounding may be relevant.
Acute kidney injury portends mortality in COVID-19 43,44 . Adjudicated myocarditis was associated with acute kidney injury during admission and the averaged native T1 (ms) in the kidney medulla 28-60 days post-discharge, re ecting multiorgan in ammation during convalescence. These associations may be explained by systemic pathophysiology i.e. in ammation, hemostatic pathway activation, microvascular dysfunction, severe COVID-19 infection, or a combination of these pathologies 43 . Cardio-renal injury associated with persisting impairments in health-related quality of life, and poorer physical and psychological wellbeing during convalescence.
Post-COVID-19 syndrome ('long COVID') predominately affects females 1,6,12,45 . The proportion of women increased with the likelihood of myocarditis and female sex was a univariable associate of adjudicated myocarditis, which in turn was associated with lower mental and physical wellbeing. Adjudicated myocarditis was associated with left ventricular systolic dysfunction in females. Our ndings provide a pathophysiological basis for symptoms burden and exercise limitation in some female patients with myocardial involvement post-COVID-19 45 .
Our ndings support clinical evaluation for myocarditis in patients who are hospitalized with COVID-19, especially in intensive care. Troponin is a cardiac protein that is ubiquitously released from injured cardiomyocytes. A rise in circulating troponin concentration is not cause-speci c and troponin may increase due to hypoxia, hypotension, ischemia, and renal failure as well as from direct myocardial toxicity. On the other hand, cardiac biomarkers are a diagnostic criterion for myocarditis and are informative for prognostication 46 . Outside of intensive care, a selective approach for measuring cardiac biomarkers, informed by clinical ndings, would seem appropriate.
Although there are no evidence-based treatments for the prevention or treatment of myocarditis in COVID-19, acute treatments, such as dexamethasone 47 , should reduce the likelihood of myocarditis occurring. Since our ndings identify myocarditis as an associate of worse physical and mental health post-COVID-19, cardio-renal involvement could be considered a therapeutic target (endpoint) in clinical trials to prevent post-COVID-19 syndrome. The RECOVERY Trial is currently investigating the effects of immunomodulatory therapies in acute COVID-19, including baricitinib and dimethyl fumarate, and the sodiumglucose cotransporter-2 inhibitor, empagli ozin, which reduces the progression of kidney disease and lower rates of clinically relevant renal events in patients with type 2 diabetes at high cardiovascular risk 48 .
To our knowledge, the combination of systematic cardio-renal MRI and chest CT, including pulmonary and coronary angiography with FFR CT , during the same visit, coupled with serial assessments of multisystem biomarkers and patient reported outcome measures, is novel. FFR CT provided a high level of certainty for identifying ow-limiting coronary artery disease (myocardial ischemia) as a confounding associate for myocardial in ammation in this post-COVID-19 population.
Our study was designed to minimize selection bias excepting those who were unable to comply with the protocol. Use of hospital-level electronic health records in real-time facilitated an unbiased approach to screening. Troponin elevation was not an eligibility criterion and renal dysfunction was not an exclusion criterion. Our study stands apart from other studies, including those which had target populations with myocardial injury de ned by troponin elevation (COVID-HEART 49 and COVIDsortium 50 ), retrospective case selection 18,19 or a sample size limiting generalizable conclusions 11 .
Our study minimized ascertainment bias which may have affected prior studies of myocarditis. The diagnosis of each patient was independently adjudicated by a committee of cardiologists and the statistical analysis was undertaken by biostatisticians independent of the research team. Since the study involved a single imaging reference center and central laboratories for biomarkers, measurement variations were minimized. The results may reasonably be considered as representative of post-COVID-19 populations who received hospital care.
This study was designed but not powered to assess clinical outcomes such as rehospitalization and death. In 47,780 individuals (mean age 65 years, 55% men) hospitalized with COVID-19 and discharged alive, during a mean follow-up of 140 days, nearly a third of individuals were readmitted (14,060 of 47,780) and more than one in ten (5875) died after discharge, with these events occurring at rates four and eight times greater, respectively, than in the matched control group 6 .

Limitations
By designating imaging during the convalescent phase, the community-based participants were not anticipated to be infectious. This approach aligns with the International Severe Acute Respiratory and Emerging Infection Coronavirus Clinical Characterisation Consortium (ISARIC4C) study 51 . Since multi-organ imaging was not performed during the acute phase, some pathologies that might have been detected acutely may have resolved by 28 days. Our ndings may therefore under-estimate disease burden. Most of the patients were unvaccinated. The incidence of myocarditis in hospitalized vaccinated patients warrants investigation. The de nition of acute kidney injury was based on in-hospital blood tests. Endomyocardial biopsy (EMB) was not performed. Longer term follow-up is ongoing.

Conclusions
The illness trajectory of COVID-19 includes persisting cardio-renal in ammation, lung involvement, and hemostatic pathway activation. Adjudicated myocarditis occurred in one in eight patients and was associated with poorer health-related quality of life, psychological wellbeing, physical activity, and predicted aerobic exercise capacity. The results support the rationale for cardio-renal therapy development for prevention of post-COVID-19 syndromes.

Declarations
Disclosures CB is employed by the University of Glasgow which holds consultancy and research agreements with Abbott Vascular, AstraZeneca, Boehringer Ingelheim, Coroventis, GSK, HeartFlow, Menarini, Novartis, Siemens Healthcare and Somalogic. These companies had no role in the design or conduct of the study, or in the data collection, interpretation, or reporting. HeartFlow derived FFR CT . None of the other authors have any relevant disclosures.

Contributors
CB designed the study and wrote the rst draft of the manuscript with KM. AMcI and AMcC developed the statistical analysis plan and performed the statistical analyses. The co-authors reviewed the manuscript drafts. Each author has individually contributed to either the delivery of the study or helped to devise aspects of the study protocol. All authors have given nal approval for the current version to be published. 33. EQ-5D-5L -EQ-5D. https://euroqol.org/eq-5d-instruments/eq-5d-5l-about/.           (20) 63 (14) 58 (15) Table 4. Health status, illness perception, anxiety and depression, and physical function.

Figure 1
Flow diagram of the clinical study. The procedures involved screening hospitalised patients with COVID-19 and obtaining informed consent. Serial investigations were initiated in-hospital or early post-discharge (visit 1) and then repeated in association with multi-organ imaging at 28-60 days postdischarge (visit 2).

Supplementary Files
This is a list of supplementary les associated with this preprint. Click to download. CISCO19Supplement20211105NatMed.docx CISCOSAPv10Signed.pdf