Doctoral Degrees (Cardiology)

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Browsing Doctoral Degrees (Cardiology) by Subject "Cardiovascular system -- Diseases"

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    Prospective evaluation of the presence, profile and evolution of asymptomatic cardiovascular disease in treatment naïve, HIV infected patients using cardiac magnetic resonance imaging after initiation on antiretroviral therapy
    (Stellenbosch : Stellenbosch University, 2022-12) Robbertse, Pieter-Paul Strauss; Herbst, Philip G; Doubell, Anton F.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine: Cardiology.
    ENGLISH ABSTRACT: HIV-associated cardiovascular disease (CVD) exists on a spectrum, is poorly understood, and may be highly heterogenous. In low- and middle income countries, HIV-associated cardiomyopathy (HIVAC) remains prevalent; yet, little research is available on antiretroviral treatment (ART) naïve persons from these regions. The study of subclinical CVD may increase our appreciation of HIV-related pathology. Purpose and methods The dissertation’s purpose was to explore subclinical HIV-associated CVD. Our experience with the diagnosis and management of symptomatic HIVAC, and the questions that arose from this, served as motivation for the development of this prospective research project assessing for subclinical HIVAC in people living with HIV (PLWH). Cardiovascular magnetic resonance imaging (CMR), supplemented by additional modalities, was employed in a cohort study of newly diagnosed, ART naïve PLWH in South Africa. Contemporary, HIV uninfected persons were recruited as a control group. Cardiovascular findings were compared between the research groups at enrolment and at 9 months after the initiation of ART. Key findings Distinct similarities exist between symptomatic and subclinical HIVAC, characterised by dilated and thickened left ventricles (LV), decreased systolic function, and tissue characterisation suggesting myocardial oedema. ART improved but did not normalise these abnormalities. The finding of inflammation in our asymptomatic cohort suggests that HIVAC exists along a spectrum, ranging from asymptomatic cardiac inflammation to end stage dilated cardiomyopathy. Inflammation is therefore likely to be the central pathology as supported by CMR imaging biomarkers, biochemical markers of inflammation, and highly prevalent pericardial effusions in our HIV cohort. The cross-sectional analysis of the cohort study revealed altered structure, function, tissue characteristics, biochemical signatures, and aortic stiffness in PLWH compared with controls. The features of dilated ventricles in PLWH with increased LV mass and deceased biventricular systolic function were associated with myocardial tissue abnormalities. These included elevated native T1, T2, and extracellular volume mapping (ECV). Furthermore, PLWH had a high prevalence of cardiac fibrosis and aortic stiffness, already present at the time of HIV diagnosis. Significant associations with the HIV viral load were demonstrable between the LV and right ventricular (RV) ejection fractions and markers of myocardial oedema. Cardiac biochemical biomarkers of myocardial stretch, remodelling, and fibrosis showed promise as surrogates for CMR imaging biomarkers. The prospective data of PLWH showed that, despite the decrease in systemic inflammation and myocardial oedema, the LV size and systolic function did not improve. Coupled with tissue characterisation evidence of persistent myocardial fibrosis, this suggests irreversible cardiac injury, partially to ART. Conclusion At the time of HIV diagnosis, the hearts of PLWH demonstrated subclinical abnormalities. ART improved, but did not completely normalise these abnormalities. Myocardial oedema and fibrosis were present, supporting the current inflammatory hypothesis of HIV. The subclinical myocardial abnormalities resemble cases of symptomatic HIVAC, and may represent a stage in the evolution towards more advanced CVD. In the absence of long-term clinical outcomes, the aortic stiffness and cardiac biomarker findings suggest increased cardiovascular risk in our cohort. This body of work provides robust data that lays the foundation for further research on the cardiovascular risk and clinical outcomes of subclinical CVD in PLWH.
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    Renal denervation restores autonomic imbalance and prevents atrial fibrillation in patients with hypertensive heart disease : a pilot study
    (Stellenbosch : Stellenbosch University., 2020-03) Heradien, Marshall Jacobus; Brink, Paul A.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine. Cardiology.
    ENGLISH ABSTRACT: Background: Atrial fibrillation (AF) is associated with increased cardiovascular morbidity and mortality, but it is uncertain if catheter-based renal denervation (RD) can reduce AF in patients with hypertensive heart disease (HHD). Methods: Patients who were ≥ 55 years old, in sinus rhythm, taking ≥ 3 anti-hypertensive drugs including a diuretic, with echocardiogram-confirmed HHD and suspected coronary artery disease, were randomised to undergo RD or sham procedure. Patients with renal impairment, significant valvular heart disease and untreated thyroid disease were excluded. The primary endpoint, the first episode of subclinical AF (SAF) lasting ≥ 6 minutes, was detected using an implantable loop recorder which was scanned every six months. Six-month follow-up (6MFU) office systolic blood pressure (SBP), cardiovascular mortality and restoration of autonomic imbalance were secondary endpoints. Results: Eighty patients were randomised: 42 underwent RD and 38 a sham procedure. After an average follow-up of three years, fewer RD patients experienced SAF: 6 of 42 patients (14.3%) vs 15 of 38 (39.5%) sham patients (odds ratio (OR), 0.26; 95% CI, 0.1 to 0.71, p = 0.01). Fast AF (ventricular rate ≥ 100 bpm) occurred in 10 sham patients (26.3%) vs 1 RD patient (2.4%): OR, 14.64; 95% CI, 1.77 to 120.91; p = 0.002). The incidence of cardiovascular death was higher in the sham than RD group (6 of 38 (15.8%) vs 1 of 42 (2.4%): OR, 7.69; 95% CI, 0.88 to 67.12; p = 0.049). Non-ST elevation myocardial infarction (NSTEMI) incidence was lower in the RD than sham group (2.3% vs 18.4%: OR, 0.108; 95% CI, 0.01–0.92; p = 0.02). The 6MFU between-group SBP difference was not significant (−3.8 mmHg; p = 0.49). Resting and one-minute recovery heart rate did not differ between groups at 6MFU. Conclusion: In patients with HHD, RD reduces subclinical and fast AF, NSTEMI and cardiovascular death independent of lowering blood pressure. RD was not associated with improvement of surrogate markers of autonomic imbalance.