This is a cross-sectional and natural history study in which we seek to 1) estimate the burden of cardiac disease in 250 consecutive participants newly diagnosed with PTB and 2) explore the natural history of cardiac pathology in patients with PTB over the course of standard TB treatment, expected to last approximately six months.

Participants will be recruited at a large district-level hospital in Lusaka, Zambia, that serves a a high-density township with high levels of poverty and has an estimated TB incidence of 850/100,000 in patients aged > 15 and an HIV prevalence of 20% among adults aged 18–44 [Zambart, unpublished data, 2020]. We expect approximately 50% of our participants to be PLHIV.

We aim to recruit age- and sex-matched comparators on a 2:1 ratio, or approximately 125 comparators. Comparators will be participants living with and without HIV where TB disease has been excluded and will provide an estimate of prevalent cardiac pathology in the general outpatient population attending Kanyama Hospital.

Selection criteria for PTB patients

Participants with PTB will be identified by the study team onsite at the TB clinic at Kanyama Hospital, where all newly diagnosed patients are enrolled for treatment initiation. All patients who meet inclusion criteria will be eligible for recruitment and will be appropriately sensitised prior to obtaining written informed consent for participation in the study.

Inclusion criteria

Participants with PTB must be aged ≥ 18, provide signed informed consent (or witnessed thumb-printed informed consent if illiterate) for study participation, and present with a new diagnosis of PTB and/or PTB with extrapulmonary TB (EPTB) defined as a) bacteriologically confirmed disease on sputum, positive by Xpert MTB/RIF® (Cepheid, Sunnyvale, CA, USA) polymerase chain reaction (PCR) test and/or b) radiologically-confirmed disease within the preceding two weeks. 

Exclusion criteria

Participants will be excluded if they 1) decline or are unable to provide consent, 2) if they are current hospital inpatients, 3) if they are pregnant, 4) if they have tuberculosis disease without pulmonary involvement 5) if they are diagnosed with Rifampicin-resistant TB.

Selection criteria for comparator population

HIV-negative comparator participants will be approached within the healthcare facility whilst comparator participants who are PLHIV will be individuals established on anti-retroviral therapy (ART) for more than 6 months recruited from HIV outpatient clinics.

Comparator participants must be aged ≥ 18, able to provide signed informed consent (or witnessed and thumb-printed informed consent if illiterate) and have a documented negative World Health Organization (WHO) four symptom screen for TB (WHO 4SS) and a negative Xpert MTB/RIF® PCR test. Comparator participants living with HIV must have been established on anti-retroviral therapy (ART) for longer than six months with documented HIV viral load suppression.

Comparator participants will be excluded if they 1) refuse or are unable to provide informed consent, 2) have one or more clinical symptoms of TB during WHO 4SS, 3) are clinically unwell at the time of recruitment, 4) are hospital inpatients, 5) have a documented history of cardiovascular disease, 6) have not been established on ART for > 6 months, or 7) refuse or are unable to provide sputum for Xpert MTB/RIF® PCR.

Study activities

Recruitment to the TB-HEART studies commenced in November 2023. Participants with PTB will be followed up longitudinally until they complete TB treatment at six months in accordance with Zambian TB treatment guidelines. The natural history study is expected to be completed in February 2025, or six months after the last participant with PTB is recruited to the cross-sectional study.

The study procedures for the cross-sectional prevalence study and natural history study are described in Fig. 1A and B.

Fig. 1

A Study Diagram: Cross-sectional Study to determine the prevalence of cardiac pathology in consecutively recruited participants with PTB in Lusaka, Zambia. 250 consecutively recruited participants with PTB will be matched to comparator participants without PTB on a 2:1 basis. Participants and comparators will undergo a comprehensive clinical assessment; functional assessments including Bandim TB score, WHO Performance status and six-minute walk test; point-of-care echocardiography; and 2D-echocardiography. B Study Diagram: Natural history study where participants with PTB will be followed up at 2- and 6-months to a) evaluate TB outcomes and b) determine change in functional status over time and c) biomarkers of inflammation and cardiac pathology in those with PTB with and without echocardiographic evidence of cardiac pathology at diagnosis. Legend: 6MWT = 6-min walk test

Clinical and functional assessments

We will use study-specific electronic questionnaires to capture the following data at enrolment and subsequent study visits: 1) sociodemographic details including age, sex, household income, address and contact details 2) focused medical and drug history to capture type and duration of TB symptoms; past medical and cardiovascular disease history and, where applicable, HIV diagnosis and treatment history 3) clinical observations including blood pressure, heart rate, respiratory rate, pulse oximetry, and temperature and 4) detailed cardiac, respiratory and abdominal examination.

Functional assessment of TB disease severity at baseline and follow-up visits will be assessed using 1) the Bandim TB score, a standardised questionnaire to identify patients at highest risk of treatment failure and/or death following TB diagnosis [22] 2) WHO Performance status and 3) six-minute walk test (6MWT), a standardised protocol to assess functional respiratory capacity [23].

Cardiac ultrasoundPoint of care echocardiography

A study-specific protocol adapted from the Society of Intensive Care Medicine Focused Ultrasound for Intensive Care (FUSIC) Heart protocol will be used to rapidly assess cardiac anatomy and function including presence or absence of pericardial disease and/or left ventricular systolic dysfunction in all participants at their baseline visit using a Clarius® phased-array handheld cardiac ultrasound probe (Clarius Mobile Health, Vancouver, BC, Canada) [24].

Diagnostic images will be stored securely on a password-protected tablet linked to the handheld probe. Point-of-care echocardiography results will be shared with the patient and their treating clinician in Zambia to ensure appropriate management according to local clinical guidelines, if necessary.

Standard echocardiography

All participants will undergo two-dimensional (2D) echocardiography which will capture images in parasternal long- and short-axis; four-chamber; two-chamber; five-chamber; and subcostal views followed by doppler assessment and assessment for pericardial pathology.

Echocardiography assessments will take place at the Echocardiography Department at University Teaching Hospital and are performed by trained echocardiographers using a GE Logiq S7 Expert Ultrasound Machine® (General Electric, Boston, MA, USA). The minimum image acquisition dataset adheres to British and European Society for Echocardiography standards.

Participants with PTB will be given appointments at least two weeks after starting anti-tuberculous therapy in compliance with infection control procedures to minimise cross-infection risk.

All participants with echocardiographic evidence of cardiac pathology will be referred for further assessment in line with local guidelines and will be offered a repeat echocardiogram following completion of TB treatment.

Image acquisition, storage, and analysis

Images will be captured in Digital Imaging and Communications in Medicine (DICOM®) format, anonymised, and stored on an encrypted and password protected study computer and secure cloud-based server.

Echocardiography assessments will be reported in real-time and results shared with the participant and their responsible clinical team. To minimise reporter bias, a proportion of participant DICOM® cine loops and images will be externally reviewed by expert members of the study team.

Blood sample testing including cardiac and inflammatory biomarkers

The study team will collect up to 10 millilitres (ml) whole blood in Ethylene-Diamene-Tetra-Acetic (EDTA) from each participant at baseline and endline assessments ensuring appropriate aseptic non-touch technique.

Blood samples will be tested for: 1) C-reactive protein (CRP) on the Abbott Afinion® point-of-care analyser (Abbott Laboratories, Abbott Park, IL, USA); and 2) high-sensitivity cardiac troponin I (hs-cTnI) and N-terminal pro B-type natriuretic peptide (NT pro-BNP) on Abbott Architect® (Abbott Laboratories, Abbott Park, IL, USA). Remaining sera will be aliquoted and stored in -80 degree freezers.

We will offer HIV testing to any participant who has not undergone an HIV test in the preceding six months, unless the participant is already living with HIV. If the test is reactive, the participant will be referred to the local HIV team.

All blood samples of participants who are PLHIV will be tested for CD4 count on the PIMA™ CD4 point-of-care analyser (Abbott Laboratories, Abbott Park, IL, USA) and HIV viral load on the Xpert® HIV-1 Viral Load point-of-care analyser (Cepheid, Sunnyvale, CA, USA).

Study visitsBaseline assessment

The baseline assessment comprises of two study visits: study visit 1 is the comprehensive clinical and functional assessment where we capture anthropometric and socio-economic data; standardised clinical observation and clinical examination findings; 12-lead electrocardiogram; functional assessment including Bandim TB score, WHO performance status and 6MWT; point-of-care echocardiography; and blood sampling.

Participants are then invited to study visit 2 to undergo 2D-echocardiography at University Teaching Hospital. Comparator participants are not routinely followed-up beyond this visit, however, any participant where abnormalities are found on echocardiography is referred for further investigation and management with the local cardiology team.

Two- and six-month follow up assessments

All participants with PTB will be followed-up at two months – study visit 3, to coincide with expected step-down from intensive to continuation phase anti-tuberculous treatment – when the study team will repeat clinical and functional assessments only.

Participants with PTB will be reviewed at approximately six months to coincide with the expected completion of TB treatment as per local standard of care – study visit 4. Clinical and functional assessments and blood sampling will be repeated. We will record TB treatment outcomes in line with standard WHO definitions and all participants with PTB will be invited to undergo a repeat 2D-echocardiography assessment at UTH.

Study visits are summarised in Fig. 2 – Study Visits flow diagram.

Fig. 2

Study Flow Diagram. Describes the study visits that participants will attend over the course of six months from enrolment. *Clinical assessment is history and examination, functional assessment (Bandim TB, WHO Performance Status, and six-minute walk test). Blood draws are cardiac biomarkers including high-sensitivity troponin I and non-terminal pro-B type natriuretic peptide, and inflammatory biomarkers including C-reactive protein. POC Echo = point-of-care echocardiography; TTE = transthoracic echocardiogram; PTB = pulmonary TB

Long-term follow-up

Participants with PTB will be followed up until they complete TB treatment, or approximately six months following recruitment.

No further follow-up visits are planned beyond six months, but we plan to keep a record of all participants recruited to the study to enable the study team to evaluate longer-term health consequences of TB disease and cardiovascular health in the future.

Loss to follow-up

Detailed participant locator forms listing two contact numbers will be completed where possible, and participants will be encouraged to contact the study team at any point during the study if necessary.

Participants will be provided with a two- and six-month appointment date and will receive a reminder telephone call from the research team to confirm the validity of demographic information and enquire as to the participant’s ongoing consent to remain in the study.

Participants who remain uncontactable after two months will receive a home visit. If no further contact can be made beyond this time, the participant will be recorded as lost to follow-up.