Pulmonary hypertension in majority countries: opportunities amidst challenges

The prevalence of pulmonary hypertension in post-tuberculosis and active tuberculosis populations: a systematic review and meta-analysis

BACKGROUND

The prevalence of tuberculosis (TB)-associated pulmonary hypertension (PH) has not previously been quantified, resulting in an underappreciated burden of disease. We aimed to estimate the prevalence of PH in post-TB and active TB populations.

METHODS

In this systematic review and meta-analysis, we searched PubMed/Medline, Cochrane Library, EBSCOhost, Scopus, African Journals Online and Google Scholar, with no language restriction, for available literature published after 1950. Eligible studies described adult participants (≥16 years), with documented evidence of active or prior TB, diagnosed with PH. Study quality was assessed using a risk of bias tool specifically developed for prevalence studies. Aggregate prevalence estimates with 95% confidence intervals were synthesised using a random-effects meta-analysis model, incorporating the Freeman-Tukey transformation. Subgroup analysis was conducted to ascertain prevalence estimates in specific patient populations.

RESULTS

We identified 1452 unique records, of which 34 met our inclusion criteria. 23 studies, with an acceptable risk of bias and where PH was diagnosed at right heart catheterisation or echocardiography, were included in the meta-analysis. In post-TB studies (14/23), the prevalence of PH was 67.0% (95% CI 50.8-81.4) in patients with chronic respiratory failure, 42.4% (95% CI 31.3-54.0) in hospitalised or symptomatic patients and 6.3% (95% CI 2.3-11.8) in nonhealthcare-seeking outpatients (I2=96%). There was a lower estimated prevalence of PH in studies of populations with active TB (9.4%, 95% CI 6.3-13.0), I2=84%).

CONCLUSION

Our results highlight the significant burden of PH in post-TB and active TB populations. We emphasise the need for increased recognition of TB-associated PH and additional high-quality prevalence data.

Prevalence and Impact of HIV Infections in Patients with Rheumatic Heart Disease: A Systematic Review and Meta-Analysis

Socioeconomic factors such as poor health and poor nutrition in low- and middle-income countries (LMICs) may favour inflammatory reactions, thus contributing to the recurrence of rheumatic fever (RF) and thereby modifying trends in rheumatic heart disease (RHD). Apart from epidemiological studies, studies of HIV infections in RHD patients are limited. This systematic review synthesises data on the prevalence and impact of HIV infections or AIDS on RHD from PubMed, Scopus, Web of Science databases up to April 2021. The outcomes were managed using PRISMA guidelines. Of a total of 15 studies found, 10 were eligible for meta-analyses. Meta-analysis found that 17% (95 % CI 8-33, I2 = 91%) of adults in cardiovascular disease (CVD) cohorts in Southern Africa are HIV positive. The proportion of RHD diagnosed among people living with HIV was 4% (95% CI 2-8, I2 = 79%) for adults but lower [2% (95% CI 1-4, I2 = 87%)] among perinatally infected children. Despite limited reporting, HIV-infected patients with RHD are prone to other infections that may enhance cardiac complications due to poor immunological control. PROSPERO registration number: CRD42021237046.

Gut microbiota crosstalk mechanisms are key in pulmonary hypertension: The involvement of melatonin is instrumental too

The microbiota refers to a plethora of microorganisms with a gene pool of approximately three million, which inhabits the human gastrointestinal tract or gut. The latter, not only promotes the transport of nutrients, ions, and fluids from the lumen to the internal environment but is linked with the development of diseases including coronary artery disease, heart failure, and lung diseases. The exact mechanism of how the microbiota achieves crosstalk between itself and distant organs/tissues is not clear, but factors released to other organs may play a role, like inflammatory and genetic factors, and now we highlight melatonin as a novel mediator of the gut-lung crosstalk. Melatonin is present in high concentrations in the gut and the lung and has recently been linked to the pathogenesis of pulmonary hypertension (PH). In this comprehensive review of the literature, we suggest that melatonin is an important link between the gut microbiota and the development of PH (where suppressed melatonin-crosstalk between the gut and lungs could promote the development of PH). More studies are needed to investigate the link between the gut microbiota, melatonin and PH. Studies could also investigate whether microbiota genes play a role in the epigenetic aspects of PH. This is relevant because, for example, dysbiosis (caused by epigenetic factors) could reduce melatonin signaling between the gut and lungs, reduce subcellular melatonin concentrations in the gut/lungs, or reduce melatonin serum levels secondary to epigenetic factors. This area of research is largely unexplored and further studies are warranted.

Investigation of imbalances in essential/toxic metal levels in the blood of laryngeal cancer patients in comparison with controls

Laryngeal carcinoma is one of the common types of head and neck cancer, with men being more likely than women to develop it. Diet, age, gender, smoking habits, and environmental factors play important roles in its development. The goal of this study was to ascertain if there were imbalances in essential and toxic trace metals owing to the initiation and progression of laryngeal cancer. Atomic absorption spectrometry was employed to quantify selected macroelements, and essential/toxic trace metals in blood of the cancerous patients and matching controls. Significantly higher concentrations of Pb, Cu, Fe, and Sr while substantially lower levels of Na, K, Ca, and Mg were observed in the cancer patients compared with the controls. Considerably disparate mutual relationships among the macroelements, and essential/toxic trace metals in the patients and controls were manifested by their correlation coefficients. Similarly, multivariate apportionment of the metal levels showed appreciably diverse associations and grouping in the patients and controls. The laryngeal cancer patients exhibited significant disparities in the metal levels among various sub-types (supraglottic, subglottic, transglottic, and glottic cancer) and stages (I, II, III, and IV) of the disease. Most of the metals revealed distinct differences based on the gender, habitat, age, eating preferences, and smoking habits in both donor groups. Overall, the study demonstrated significant imbalances among the macroelements, and essential/toxic trace metal levels in the blood of laryngeal cancer patients compared to the controls.

Parasitic lung diseases

Parasitic lung diseases are caused by a number of parasites as a result of transient passage in the lung or as a result of an immunologic reaction. The clinical presentation may be in the form of focal or cystic lesions, pleural effusion or diffuse pulmonary infiltrates. With increasing globalisation, it is important to consider parasitic infections in the differential diagnosis of lung diseases. This is particularly important since early identification and prompt therapy result in full cure of these conditions. In this review, we summarise the most common parasitic lung diseases.

Mice with humanized immune system as novel models to study HIV-associated pulmonary hypertension

People living with HIV and who receive antiretroviral therapy have a significantly improved lifespan, compared to the early days without therapy. Unfortunately, persisting viral replication in the lungs sustains chronic inflammation, which may cause pulmonary vascular dysfunction and ultimate life-threatening Pulmonary Hypertension (PH). The mechanisms involved in the progression of HIV and PH remain unclear. The study of HIV-PH is limited due to the lack of tractable animal models that recapitulate infection and pathobiological aspects of PH. On one hand, mice with humanized immune systems (hu-mice) are highly relevant to HIV research but their suitability for HIV-PH research deserves investigation. On another hand, the Hypoxia-Sugen is a well-established model for experimental PH that combines hypoxia with the VEGF antagonist SU5416. To test the suitability of hu-mice, we combined HIV with either SU5416 or hypoxia. Using right heart catheterization, we found that combining HIV+SU5416 exacerbated PH. HIV infection increases human pro-inflammatory cytokines in the lungs, compared to uninfected mice. Histopathological examinations showed pulmonary vascular inflammation with arterial muscularization in HIV-PH. We also found an increase in endothelial-monocyte activating polypeptide II (EMAP II) when combining HIV+SU5416. Therefore, combinations of HIV with SU5416 or hypoxia recapitulate PH in hu-mice, creating well-suited models for infectious mechanistic pulmonary vascular research in small animals.

Reviewing the suitability of mitochondrial transplantation as therapeutic approach for pulmonary hypertension in the era of personalised medicine

Pulmonary hypertension (PH) is a fatal disease, defined as a mean pulmonary artery pressure ≥ 25 mm Hg. It is caused, in part, by mitochondrial dysfunction. Among the various biological therapies proposed to rescue mitochondrial dysfunction, evidence going back as far as 2009, suggests that mitochondrial transplantation is an alternative. Although scant, recent PH findings and other literature supports a role for mitochondrial transplantation as a therapeutic approach in the context of PH. In experimental models of PH, it confers beneficial effects that include reduced pulmonary vasoconstriction, reduced pulmonary vascular remodelling, and improved right ventricular function. It also reduces the proliferation of pulmonary artery smooth muscle cells. However, first, we must understand that more research is needed before mitochondrial transplantation can be considered an effective therapy in the clinical setting, as many of the mechanisms or potential long-term risks are still unknown. Second, the current challenges of mitochondrial transplantation are surmountable and should not deter researchers from further investigating its effectiveness and trying to overcome these challenges in creative ways.