Novel role of cardiovascular MRI to contextualise tuberculous pericardial inflammation and oedema as predictors of constrictive pericarditis.

Tuberculosis (TB) and human immunodeficiency virus/acquired immunodeficiency syndrome have reached epidemic proportions, particularly affecting vulnerable populations in low- and middle-income countries of sub-Saharan Africa. TB pericarditis is the commonest cardiac manifestation of TB and is the leading cause of constrictive pericarditis, a reversible (by surgical pericardiectomy) cause of diastolic heart failure in endemic areas. Unpacking the complex mechanisms underpinning constrictive haemodynamics in TB pericarditis has proven challenging, leaving various basic and clinical research questions unanswered. Subsequently, risk stratification strategies for constrictive outcomes have remained unsatisfactory. Unique pericardial tissue characteristics, as identified on cardiovascular magnetic resonance imaging, enable us to stage and quantify pericardial inflammation and may assist in identifying patients at higher risk of tissue remodelling and pericardial constriction, as well as predict the degree of disease reversibility, tailor medical therapy, and determine the ideal timing for surgical pericardiectomy.

The incidence and outcomes of high-risk acute coronary syndromes in Western Cape Province, South Africa: A prospective cohort study.

BACKGROUND: Tygerberg Hospital (TBH) is a tertiary-level hospital in Western Cape Province, South Africa, that provides healthcare to a large low- to middle-income population with services including centralised advanced cardiac care. Acute coronary syndrome (ACS) remains an important cause of death in the region despite a high burden of communicable diseases, including HIV. OBJECTIVES: To describe the incidence of ST-elevation myocardial infarction (STEMI) and high-risk non-ST-elevation ACS (HR-NSTEACS) in the TBH referral network, describe the in-hospital and 30-day mortality of these patients, and identify important high-risk population characteristics. METHODS: The Tygerberg Acute Coronary Syndrome Registry database is an ongoing prospective study that enrols all STEMI and HR-NSTEACS patients in the TBH referral network. All patients aged >18 years presenting with STEMI or HR-NSTEACS were treated in accordance with current European Society of Cardiology guidelines and were included prospectively over a 9-month surveillance period. A waiver of consent was granted to include patients who died before giving informed consent. Data collected included a demographic profile, risk factors for cardiovascular disease, in-hospital therapy and 30-day mortality. RESULTS: A total of 586 patients were enrolled, with a male predominance (64.5%) and incidence rates of STEMI and HR-NSTEACS of 14.7 per 100 000 and 15.6 per 100 000, respectively. The mean patient age was 58 years, and STEMI patients tended to be younger than HR-NSTEACS patients (56 v. 58 years; p=0.01). Cardiovascular risk factors were prevalent overall, but hypertension (79.8% v. 68.3%; p<0.01) and pre-existing IHD (29.1% v. 7.0%; p=0.03) were more prevalent in the HR-NSTEACS group. HIV was present in 12.6% of patients tested, similar to the background population rate. The overall 30-day all-cause mortality rate was 6.1%, with an in-hospital mortality rate of 3.9%. The 30-day mortality rates were similar for STEMI (1.8%) and HR-NSTEACS (2.6%) (p=0.75). HIV did not affect mortality rates. CONCLUSION: Use of a guideline-based approach to treating ACS in a low- to middle-income country setting yields mortality rates comparable to those in high-income countries. However, the lower-than-expected incidence rates of both STEMI and HR-NSTEACS in a relatively young population with a high prevalence of traditional cardiovascular risk factors, and a relatively high proportion of STEMI, suggest potential under-recording of ischaemic heart disease in the region. The rate and outcomes of coronary artery disease (CAD) in people living with HIV were similar to those in people without HIV, suggesting that traditional risk factors still drive CAD outcomes in the region.

Echocardiographic features of infective endocarditis in South Africa: A prospective cohort study.

BACKGROUND: Historically, infective endocarditis (IE) in South Africa (SA) was associated with the viridans group of streptococci affecting patients with underlying rheumatic heart disease (RHD). A changing IE bacteriological profile raises the question of whether the profile of underlying valvular abnormality has changed. OBJECTIVES: To investigate the prevalence of underlying structural valve abnormalities and their aetiologies associated with IE in SA, and describe the typical imaging findings. METHODS: The Tygerberg Endocarditis Cohort study prospectively enrolled patients with IE between November 2019 and April 2021. Patients underwent detailed transthoracic and transoesophageal echocardiography to assess their underlying cardiac and valvular structure. RESULTS: Among 71 patients included, a predisposing endocardial abnormality was detected in 49.3%, with RHD the most common single identifiable aetiology (16.9%). The in-hospital mortality rate was similar in patients with and without a predisposing endocardial abnormality (20% v. 16.7%; p=0.72), as was the rate of embolic events (20% v. 27.2%; p=0.58). Significantly more patients with a predisposing endocardial abnormality had an indication for surgery (94.3% v. 69.4%; p<0.01). The viridans group of streptococci was more prevalent in patients with a predisposing endocardial abnormality (25.7% v. 2.7%; p<0.01). Left-sided linear vegetation size >10 mm was associated with an increased risk of in-hospital mortality (24% v. 5%; p=0.05). CONCLUSION: We observed a marked decrease in the prevalence of RHD in this cohort of patients with IE. The viridans group of streptococci was an uncommon cause of IE in patients with no predisposing endocardial abnormality detected. The presence of a predisposing endocardial abnormality was not associated with an increased risk of in-hospital mortality or embolic events. Linear vegetation length >10 mm was associated with an increased risk of in-hospital mortality in patients with left-sided IE.

TYPICAL VALUES OF DOSIMETRIC DATA FOR CARDIAC FLUOROSCOPY-GUIDED PROCEDURES IN A SOUTH AFRICAN TEACHING HOSPITAL.

Currently there are limited diagnostic reference level (DRL) data for South African (SA) public sector cardiac fluoroscopy-guided procedures (FGPs). A 4-y retrospective study of dosimetric data on 6265 patients determined typical values (50th percentile) of dosimetric data for the seven most frequent cardiac FGPs at a SA teaching hospital. Kerma-area-product (KAP), reference point air Kerma (Ka,r) and fluoroscopy time (FT) were, respectively, calculated for coronary angiography (CA) (n = 1935; 61Gy.cm2, 624 mGy, 5 min); CA with left ventriculography (n = 1687; 85Gy.cm2, 840 mGy, 3.9 min), valve screening (n = 129; 6Gy.cm2, 164 mGy, 2.3 min), percutaneous coronary intervention (n = 1922; 145Gy.cm2, 1569 mGy, 11.9 min), pacemaker implantation (n = 432; 9Gy.cm2, 100 mGy, 6.5 min), pericardial tap (n = 115; 1.9Gy.cm2, 18 mGy, 1.5 min) and transcatheter aortic valve implantation (n = 45; 65Gy.cm2, 658 mGy, 14.1 min). This work presents the largest SA public sector cardiac FGP dosimetric data to date and provides a key resource for future work in this domain.

Predictors of 1-year survival in South African transcatheter aortic valve implant candidates.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) has undergone rapid expansion internationally over the past 15 years. In view of resource constraints in developing countries, a major challenge in applying this technology lies in identifying patients most likely to benefit. The development of a risk prediction model for TAVI has proved elusive, with a reported area under the curve (AUC) of 0.6 - 0.65. The available models were developed in a First-World setting and may not be applicable to South Africa (SA). OBJECTIVES: To evaluate novel indicators and to develop a TAVI risk prediction model unique to the SA context. The current work represents the important initial steps of derivation cohort risk model development and internal validation. METHODS: Seven-year experience with 244 successive TAVI implants in three centres in Western Cape Province, SA, was used to derive risk parameters. All outcomes are reported in accordance with the Valve Academic Research Consortium definitions. Multiple preprocedural variables were assessed for their impact on 1-year survival using univariate and multivariate models. RESULTS: Factors found not to correlate with 1-year survival included age, renal function and aortic valve gradients. The commonly used surgical risk prediction models (Society of Thoracic Surgeons score and EuroSCORE) showed no correlation with outcomes. Factors found to correlate best with 1-year survival on multivariate analysis were preprocedural body mass index (BMI) (favouring higher BMI), preprocedural left ventricular end-diastolic dimension (LVED) and ejection fraction (EF) (favouring smaller LVED and higher EF), absence of atrial fibrillation, and three novel parameters: independent living, ability to drive a car, and independent food acquisition/cooking. Discriminant analysis of these factors yielded an AUC of 0.8 (95% confidence interval 0.7 - 0.9) to predict 1-year survival, with resubstitution sensitivities and specificities of 72% and 71%, respectively. CONCLUSIONS: Apart from existing predictors, we identified three novel risk predictors (independent living, ability to drive a car, and independent food acquisition/cooking) for 1-year survival in TAVI candidates. These novel parameters performed well in this early evaluation, with an AUC for predicting 1-year survival higher than the AUCs for many of the internationally derived parameters. The parameters are inexpensive and easy to obtain at the initial patient visit. If validated prospectively in external cohorts, they may be applicable to other resource-constrained environments.

Evaluating the time interval from diagnosis to fibrinolysis at centres in the drainage area of Tygerberg Hospital, Cape Town, South Africa.

BACKGROUND: ST-segment elevation myocardial infarction (STEMI) is one of the main contributors to morbidity and mortality in South Africa (SA). Timeous intervention by means of percutaneous coronary intervention (PCI) or fibrinolysis can significantly improve the outcome of STEMI. OBJECTIVES: To determine the median time interval between diagnosis and fibrinolysis in patients presenting to centres within the drainage area of Tygerberg Hospital, Cape Town, SA, and compare it with the European Society of Cardiology (ESC) recommendation of 10 minutes. METHODS: A retrospective medical record review of patients presenting to the abovementioned centres between 1 March 2017 and 28 February 2018 was performed. The primary presenting centre, time between diagnosis and fibrinolysis and discharge medication were recorded, in addition to other relevant demographic information. RESULTS: A total of 492 patients were identified, of whom 447 were included in the study. Three hundred and eighteen patients received fibrinolysis, of whom 18 (5.7%) were treated within 10 minutes of diagnosis. The median time interval between diagnosis and fibrinolysis was 67 (interquartile range (IQR) 32.5 -122.5) minutes. CONCLUSIONS: Most patients received fibrinolysis >10 minutes after diagnosis, which indicates suboptimal therapy when compared with the ESC guidelines. Future studies should investigate the factors prolonging this therapeutic delay.

Prominent inter-scallop separations of the posterior leaflet of the mitral valve: an important cause of 'pathological' mitral regurgitation.

The 2012 World Heart Federation (WHF) criteria for echocardiographic diagnosis of rheumatic heart disease (RHD) identify that the finding of 'pathological' mitral regurgitation (MR) in a screened individual increases the likelihood of detecting underlying RHD. Cases of isolated "pathological MR are thus identified as 'borderline RHD'. A large-scale echocardiographic screening program (Echo in Africa) in South Africa has identified that inter-scallop separations of the posterior mitral valve leaflet (PMVL) can give rise to 'pathological' MR. The authors propose that this finding when associated with isolated 'pathological' MR is unrelated to the rheumatic disease process. In this case report, we present two examples of 'pathological' MR related to inter-scallop separation from the Echo in Africa image database. We provide additional screening tips to accurately identify this entity.

Screening for rheumatic heart disease: is a paradigm shift required?

This focused review presents a critical appraisal of the World Heart Federation criteria for the echocardiographic diagnosis of rheumatic heart disease (RHD) and its performance in African RHD screening programmes. It identifies various logistical and methodological problems that negatively influence the current guideline's performance. The authors explore novel RHD screening methodology that could address some of these shortcomings and if proven to be of merit, would require a paradigm shift in the approach to the echocardiographic diagnosis of subclinical RHD.

Clinical features and outcome of lupus myocarditis in the Western Cape, South Africa.

BACKGROUND: African American ethnicity is independently associated with lupus myocarditis compared with other ethnic groups. In the mixed racial population of the Western Cape, South Africa, no data exists on the clinical features/outcome of lupus myocarditis. OBJECTIVES: The objective of this study was to give a comprehensive description of the clinical features and outcome of acute lupus myocarditis in a mixed racial population. METHODS: Clinical records (between 2008 and 2014) of adult systemic lupus erythematosus (SLE) patients at a tertiary referral centre were retrospectively screened for a clinical and echocardiographic diagnosis of lupus myocarditis. Clinical features, laboratory results, management and outcome were described. Echocardiographic images stored in a digital archive were reanalysed including global and regional left ventricular function. A poor outcome was defined as lupus myocarditis related mortality or final left ventricular ejection fraction (LVEF) <40%. RESULTS: Twenty-eight of 457 lupus patients (6.1%) met inclusion criteria: 92.9% were female and 89.3% were of mixed racial origin. Fifty-three per cent of patients presented within three months after being diagnosed with SLE. Seventy-five per cent had severely active disease (SLE disease activity index ≥ 12) and 67.9% of patients had concomitant lupus nephritis. Laboratory results included: lymphopenia (69%) and an increased aRNP (61.5%). Treatment included corticosteroids (96%) and cyclophosphamide (75%); 14% of patients required additional immunosuppression including rituximab. Diastolic dysfunction and regional wall motion abnormalities occurred in > 90% of patients. LVEF improved from 35% to 47% (p = 0.023) and wall motion score from 1.88 to 1.5 (p = 0.017) following treatment. Overall mortality was high (12/28): five patients (17.9%) died due to lupus myocarditis (bimodal pattern). Patients who died of lupus myocarditis had a longer duration of SLE (p = 0.045) and a lower absolute lymphocyte count (p = 0.041) at diagnosis. LVEF at diagnosis was lower in patients who died of lupus myocarditis (p = 0.099) and in those with a persistent LVEF < 40% (n = 5; p = 0.046). CONCLUSIONS: This is the largest reported series on lupus myocarditis. The mixed racial population had a similar prevalence, but higher mortality compared with other ethnic groups (internationally published literature). Patients typically presented with high SLE disease activity and the majority had concomitant lupus nephritis. Lymphopenia and low LVEF at presentation were of prognostic significance, associated with lupus myocarditis related mortality or a persistent LVEF < 40%.

An approach to the patient with suspected pericardial disease.

Diseases of the pericardium commonly manifest in one of three ways: acute pericarditis, pericardial effusion and constrictive pericarditis. In the developed world, the most common cause of acute pericarditis is viral or idiopathic disease, while in the developing world tuberculous aetiology, particularly in sub-Saharan Africa, is commonplace owing to the high prevalence of HIV. This article provides an approach to the diagnosis, investigation and management of these patients.

Application of Laser Doppler Vibrometery for human heart auscultation.

In this study the potential of a Laser Doppler Vibrometer (LDV) was tested as a non-contact sensor for the classification of heart sounds. Of the twenty participants recorded using the LDV, five presented with Aortic Stenosis (AS), three were healthy and twelve presented with other pathologies. The recorded heart sounds were denoised and segmented using a combination of the Electrocardiogram (ECG) data and the complexity of the signal. Frequency domain features were extracted from the segmented heart sound cycles and used to train a K-nearest neighbor classifier. Due to the small number of participants, the classifier could not be trained to differentiate between normal and abnormal participants, but could successfully distinguish between participants who presented with AS and those who did not. A sensitivity of 80 % and a specificity of 100 % were achieved a test dataset.

The influence of leaflet skin friction and stiffness on the performance of bioprosthetic aortic valves.

Leaflet skin friction and stiffness were found to have a significant influence on the systolic performance of a 19 mm diameter bioprosthetic aortic valve based on fluid-structure interaction simulations at a heart rate of 72 bpm. Four different leaflet skin friction coefficients (0.0, 9.2 × 10(-4), 4.8 × 10(-2) and 4.8 × 10(-1)) were simulated along with three different leaflet elastic moduli (3.0 × 10(6), 3.5 × 10(6), 4.0 × 10(6) N m(-2)). Higher leaflet skin friction was found to increase the magnitude of the systolic transvalvular pressure gradient and the peak velocity through the valve, as well as decrease the valve orifice area. The results for the leaflet opening and closing kinematics also showed that higher leaflet skin friction combined with higher leaflet stiffness produces longer rapid valve opening, closing and ejection times, as well as smaller valve orifice areas. These results are consistent with clinical findings for calcified aortic valves and suggest that valve performance under stenotic conditions is strongly influenced by the combined effect of increasing leaflet stiffness and surface roughness caused by calcification.

Experimental validation of the fluid-structure interaction simulation of a bioprosthetic aortic heart valve.

Experiments performed on a 19 mm diameter bioprosthetic valve were used to successfully validate the fluid-structure interaction (FSI) simulation of an aortic valve at 72 bpm. The FSI simulation was initialized via a novel approach utilizing a Doppler sonogram of the experimentally tested valve. Using this approach very close quantitative agreement (≤12.5%) between the numerical predictions and experimental values for several key valve performance parameters, including the peak systolic transvalvular pressure gradient, rapid valve opening time and rapid valve closing time, was obtained. The predicted valve leaflet kinematics during opening and closing were also in good agreement with the experimental measurements.

QTc prolongation prior to angiography predicts poor outcome and associates significantly with lower left ventricular ejection fractions and higher left ventricular end-diastolic pressures.

BACKGROUND: QT prolongation on the surface ECG is associated with sudden cardiac death. The cause of QT prolongation in ischaemic heart disease (IHD) patients remains unknown, but may be due to a complex interplay between genetic factors and impaired systolic and/or diastolic function through as yet unexplained mechanisms. It was hypothesised that QT prolongation before elective coronary angiography is associated with an increased mortality at six months. METHODS: Complete records of 321 patients who underwent coronary angiography were examined for QT interval corrected for heart rate (QTc), left ventricular ejection fraction (LVEF), left ventricular end-diastolic pressure (LVEDP) and known ischaemic heart disease risk factors. Patients were designated long QTc (LQTc) when they had prolonged QTc intervals or normal QTc (NQTc) when the QTc interval was normal. Patients with atrial fibrillation, bundle branch blocks, no ECG in the 24 hours before angiography, or a creatinine level > 200 µmol/l were excluded. Survival was determined telephonically at six months. RESULTS: Twenty-eight per cent of the total population had LQTc. During follow up, 15 patients (4.7%) died suddenly, 73% of whom had a LQTc. LQTc was significantly associated with mortality (LQTc 12% vs NQTc 1.7%; p < 0.01), and with lower but normal LVEF (LQTc 52.9 ± 15.4% vs NQTc 61.6 ± 13.6%; p < 0.01), higher LVEDP at LVEF > 45% (LQTc 19.2 ± 9.0 mmHg vs NQTc 15.95 ± 7.5 mmHg; p < 0.05), hypercholesterolaemia and a negative family history of IHD. CONCLUSION: In patients with sinus rhythm and normal QRS width, QTc prolongation before coronary angiography predicted increased mortality at six months. QTc also associated strongly with left ventricular systolic and diastolic dysfunction, hypercholesterolaemia and a negative family history of IHD.

Application of finite element analysis to the design of tissue leaflets for a percutaneous aortic valve.

Percutaneous Aortic Valve (PAV) replacement is an attractive alternative to open heart surgery, especially for patients considered to be poor surgical candidates. Despite this, PAV replacement still has its limitations and associated risks. Bioprosthetic heart valves still have poor long-term durability due to calcification and mechanical failure. In addition, the implantation procedure often presents novel challenges, including damage to the expandable stents and bioprosthetic leaflets. In this study, a simplified version of Fung's elastic constitutive model for skin, developed by Sun and Sacks, was implemented using finite element analysis (FEA) and applied to the modelling of bovine and kangaroo pericardium. The FEA implementation was validated by simulating biaxial tests and by comparing the results with experimental data. Concepts for different PAV geometries were developed by incorporating valve design and performance parameters, along with stent constraints. The influence of effects such as different leaflet material, material orientation and abnormal valve dilation on the valve function was investigated. The stress distribution across the valve leaflet was also examined to determine the appropriate fibre direction for the leaflet. The simulated attachment forces were compared with suture tearing tests performed on the pericardium to evaluate suture density. It is concluded that kangaroo pericardium is suitable for PAV applications, and superior to bovine pericardium, due to its lower thickness and greater extensibility.

Autonomous auscultation of the human heart employing a precordial electro-phonocardiogram and ensemble empirical mode decomposition.

The research presented in this paper serves to provide a tool to autonomously screen for cardiovascular disease in the rural areas of Africa. With this tool, cardiovascular disease can potentially be detected in its initial stages, which is essential for effective treatment. The autonomous auscultation system proposed here utilizes recorded heart sounds and electrocardiogram signals to automatically distinguish between normal and abnormal heart conditions. Patients that are identified as abnormal by the system can then be referred to a specialist consultant, which will save a lot of unnecessary referrals. In this study, heart sound and electrocardiogram signals were recorded with the prototype precordial electro-phonocardiogram device, as part of a clinical study to screen patients for cardiovascular disease. These volunteers consisted of 28 patients with a diagnosed cardiovascular disease and, for control purposes, 34 persons diagnosed with healthy hearts. The proposed system employs wavelets to first denoise the recorded signals, which is then followed by segmentation of heart sounds. Frequency spectrum information was extracted as diagnostic features from the heart sounds by means of ensemble empirical mode decomposition and auto regressive modelling. The respective features were then classified with an ensemble artificial neural network. The performance of the autonomous auscultation system used in concert with the precordial electro-phonocardiogram prototype showed a sensitivity of 82% and a specificity of 88%. These results demonstrate the potential benefit of the precordial electro-phonocardiogram device and the developed autonomous auscultation software as a screening tool in a rural healthcare environment where large numbers of patients are often cared for by a small number of inexperienced medical personnel.

Autonomous detection of heart sound abnormalities using an auscultation jacket.

This paper presents a study using an auscultation jacket with embedded electronic stethoscopes, and a software classification system capable of differentiating between normal and certain auscultatory abnormalities. The aim of the study is to demonstrate the potential of such a system for semi-automated diagnosis for underserved locations, for instance in rural areas or in developing countries where patients far outnumber the available medical personnel. Using an "auscultation jacket", synchronous data was recorded at multiple chest locations on 31 healthy volunteers and 21 patients with heart pathologies. Electrocardiograms (ECGs) were also recorded simultaneously with phonocardiographic data. Features related to heart pathologies were extracted from the signals and used as input to a feed-forward artificial neural network. The system is able to classify between normal and certain abnormal heart sounds with a sensitivity of 84% and a specificity of 86%. Though the number of training and testing samples presented are limited, the system performed well in differentiating between normal and abnormal heart sounds in the given database of available recordings. The results of this study demonstrate the potential of such a system to be used as a fast and cost-effective screening tool for heart pathologies.