Pulmonary Hypertension and the Gut Microbiome.

The gut microbiome and its associated metabolites are integral to the maintenance of gut integrity and function. There is increasing evidence that its alteration, referred to as dysbiosis, is involved in the development of a systemic conditions such as cardiovascular disease (e.g., systemic hypertension, atherosclerosis). Pulmonary hypertension (PH) is a condition characterised by progressive remodelling and vasoconstriction of the pulmonary circulation, ultimately leading to right ventricular failure and premature mortality if untreated. Initial studies have suggested a possible association between dysbiosis of the microbiome and the development of PH. The aim of this article is to review the current experimental and clinical data with respect to the potential interaction between the gut microbiome and the pathophysiology of pulmonary hypertension. It will also highlight possible new therapeutic targets that may provide future therapies.

Identifying patients at risk of post-discharge complications related to COVID-19 infection.

SARS-CoV-2 infection is a multisystem disease with post-discharge sequelae. We report early follow-up data from one UK hospital of the initial 200 hospital inpatients with slow recovery from the condition. At 4 weeks post-discharge, 321/957 survivors (34%) had persistent symptoms. A structured outpatient clinical assessment protocol was designed, and outcomes from the first 200 patients seen 4-6 weeks post-discharge are presented here. In 80/200 (40%), we identified at follow-up a cardiorespiratory cause of breathlessness, including persistent parenchymal abnormality (64 patients), pulmonary embolism (four patients) and cardiac complications (eight patients). These findings occurred both in patients who had intensive care unit (ICU) admissions and those who had been managed on the ward, although patients requiring ICU admissions were more likely to have a significant cardiorespiratory cause found for their breathlessness, risk ratio 2.8 (95% CI 1.5 to 5.1).

Perioperative management of patients with pulmonary hypertension undergoing non-cardiothoracic, non-obstetric surgery: a systematic review and expert consensus statement.

BACKGROUND: The risk of complications, including death, is substantially increased in patients with pulmonary hypertension (PH) undergoing anaesthesia for surgical procedures, especially in those with pulmonary arterial hypertension (PAH) and chronic thromboembolic PH (CTEPH). Sedation also poses a risk to patients with PH. Physiological changes including tachycardia, hypotension, fluid shifts, and an increase in pulmonary vascular resistance (PH crisis) can precipitate acute right ventricular decompensation and death. METHODS: A systematic literature review was performed of studies in patients with PH undergoing non-cardiac and non-obstetric surgery. The management of patients with PH requiring sedation for endoscopy was also reviewed. Using a framework of relevant clinical questions, we review the available evidence guiding operative risk, risk assessment, preoperative optimisation, and perioperative management, and identifying areas for future research. RESULTS: Reported 30 day mortality after non-cardiac and non-obstetric surgery ranges between 2% and 18% in patients with PH undergoing elective procedures, and increases to 15-50% for emergency surgery, with complications and death usually relating to acute right ventricular failure. Risk factors for mortality include procedure-specific and patient-related factors, especially markers of PH severity (e.g. pulmonary haemodynamics, poor exercise performance, and right ventricular dysfunction). Most studies highlight the importance of individualised preoperative risk assessment and optimisation and advanced perioperative planning. CONCLUSIONS: With an increasing number of patients requiring surgery in specialist and non-specialist PH centres, a systematic, evidence-based, multidisciplinary approach is required to minimise complications. Adequate risk stratification and a tailored-individualised perioperative plan is paramount.

Persistent Post-COVID-19 Interstitial Lung Disease. An Observational Study of Corticosteroid Treatment.

Rationale: The natural history of recovery from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains unknown. Because fibrosis with persistent physiological deficit is a previously described feature of patients recovering from similar coronaviruses, treatment represents an early opportunity to modify the disease course, potentially preventing irreversible impairment.Objectives: Determine the incidence of and describe the progression of persistent inflammatory interstitial lung disease (ILD) following SARS-CoV-2 when treated with prednisolone.Methods: A structured assessment protocol screened for sequelae of SARS-CoV-2 pneumonitis. Eight hundred thirty-seven patients were assessed by telephone 4 weeks after discharge. Those with ongoing symptoms had outpatient assessment at 6 weeks. Thirty patients diagnosed with persistent interstitial lung changes at a multidisciplinary team meeting were reviewed in the interstitial lung disease service and offered treatment. These patients had persistent, nonimproving symptoms.Results: At 4 weeks after discharge, 39% of patients reported ongoing symptoms (325/837) and were assessed. Interstitial lung disease, predominantly organizing pneumonia, with significant functional deficit was observed in 35/837 survivors (4.8%). Thirty of these patients received steroid treatment, resulting in a mean relative increase in transfer factor following treatment of 31.6% (standard deviation [SD] ± 27.6, P < 0.001), and forced vital capacity of 9.6% (SD ± 13.0, P = 0.014), with significant symptomatic and radiological improvement.Conclusions: Following SARS-CoV-2 pneumonitis, a cohort of patients are left with both radiological inflammatory lung disease and persistent physiological and functional deficit. Early treatment with corticosteroids was well tolerated and associated with rapid and significant improvement. These preliminary data should inform further study into the natural history and potential treatment for patients with persistent inflammatory ILD following SARS-CoV-2 infection.

Cardiopulmonary exercise testing demonstrates maintenance of exercise capacity in patients with hypoxemia and pulmonary arteriovenous malformations.

BACKGROUND: Patients with pulmonary arteriovenous malformations (PAVMs) are unusual because hypoxemia results from right-to-left shunting and not airway or alveolar disease. Their surprisingly well-preserved exercise capacity is not generally appreciated. METHODS: To examine why exercise tolerance is preserved, cardiopulmonary exercise tests were performed while breathing room air in 21 patients with radiologically proven PAVMs, including five restudied 3 to 12 months after embolization when their PAVMs had regressed. Where physiologic matching was demonstrable, comparisons were made with 12 healthy control subjects. RESULTS: The majority of patients achieved their predicted work rate despite a resting arterial oxygen saturation (SaO2) of 80% to 96%. Peak work rate and oxygen consumption (VO2) were no lower in patients with more hypoxemia. Despite higher SaO2 following embolization (median, 96% and 90%; P = .009), patients achieved similar work rates and similar peak VO2. Strikingly, treated patients reset to virtually identical peak oxygen pulses (ie, VO2 per heart beat) and in many cases to the same point on the peak oxygen pulse/work rate plot. The 21 patients had increased minute ventilation (VE) for given increases in CO2 production (VE/VCO2 slope), but perceived dyspnea was no greater than in the 12 control subjects or in the same patients before compared to after embolization comparison. Overall, work rate and peak VO2 were associated not with oxygenation parameters but with VE/VCO2 slope, BMI, and anaerobic threshold. CONCLUSIONS: Patients with hypoxemia and PAVMs can maintain normal oxygen delivery/VO2 during peak exercise. Following improvement of SaO2 by embolization, patients appeared to reset compensatory mechanisms and, as a result, achieved similar peak VO2 per heart beat and peak work rates.

Combination therapy in pulmonary arterial hypertension: do we have the right strategy?

The management of pulmonary hypertension has already incorporated the use of multiple therapies into routine practice. Available therapies act principally through vasodilatation of the pulmonary arterial circulation through well-delineated mechanisms, although right ventricular function determines function and prognosis. Therefore, the goal of these therapies is effectively to preserve right ventricular function through reducing right ventricular afterload. The clinical trial experience of combination therapy is limited and the optimal combinations and administration strategies have yet to be clarified.

Mapping of the cerebral response to acetazolamide using graded asymmetric spin echo EPI.

Cerebral vascular reactivity in different regions of the rat brain was quantitatively characterized by spatial and temporal measurements of blood oxygenation level-dependent (BOLD)-fMRI signals following intravenous administration of the carbonic anhydrase inhibitor acetazolamide: this causes cerebral vasodilatation through a cerebral extracellular acidosis that spares neuronal metabolism and vascular smooth muscle function, thus separating vascular and cerebral metabolic events. An asymmetric spin echo-echo planar imaging (ASE-EPI) pulse sequence sensitised images selectively to oxygenation changes in the microvasculature; use of a surface coil receiver enhanced image signal-to-noise ratios (SNRs). Image SNRs and hardware integrity were verified by incorporating quality assurance procedures; cardiorespiratory stability in the physiological preparations were monitored and maintained through the duration of the experiments. These conditions made it possible to apply BOLD contrast fMRI to map regional changes in cerebral perfusion in response to acetazolamide administration. Thus, fMRI findings demonstrated cerebral responses to acetazolamide that directly paralleled the known physiological actions of acetazolamide and whose time courses were similar through all regions of interest, consistent with acetazolamide's initial distribution in brain plasma, where it affects cerebral haemodynamics by acting at cerebral capillary endothelial cells. However, marked variations in the magnitude of the responses suggested relative perfusion deficits in the hippocampus and white matter regions correlating well with their relatively low vascularity and the known vulnerability of the hippocampus to ischaemic damage.