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Drug-associated pulmonary arterial hypertension

INTRODUCTION

While pulmonary arterial hypertension remains an uncommon diagnosis, various therapeutic agents are recognized as important associations. These agents are typically categorized into "definite", "likely", "possible", or "unlikely" to cause pulmonary arterial hypertension, based on the strength of evidence.

OBJECTIVE

This review will focus on those therapeutic agents where there is sufficient literature to adequately comment on the role of the agent in the pathogenesis of pulmonary arterial hypertension.

METHODS

A systematic search was conducted using PubMed covering the period September 1970- 2017. The search term utilized was "drug induced pulmonary hypertension". This resulted in the identification of 853 peer-reviewed articles including case reports. Each paper was then reviewed by the authors for its relevance. The majority of these papers (599) were excluded as they related to systemic hypertension, chronic obstructive pulmonary disease, human immunodeficiency virus, pulmonary fibrosis, alternate differential diagnosis, treatment, basic science, adverse effects of treatment, and pulmonary hypertension secondary to pulmonary embolism. Agents affecting serotonin metabolism (and related anorexigens): Anorexigens, such as aminorex, fenfluramine, benfluorex, phenylpropanolamine, and dexfenfluramine were the first class of medications recognized to cause pulmonary arterial hypertension. Although most of these medications have now been withdrawn worldwide, they remain important not only from a historical perspective, but because their impact on serotonin metabolism remains relevant. Selective serotonin reuptake inhibitors, tryptophan, and lithium, which affect serotonin metabolism, have also been implicated in the development of pulmonary arterial hypertension. Interferon and related medications: Interferon alfa and sofosbuvir have been linked to the development of pulmonary arterial hypertension in patients with other risk factors, such as human immunodeficiency virus co-infection. Antiviral therapies: Sofosbuvir has been associated with two cases of pulmonary artery hypertension in patients with multiple risk factors for its development. Its role in pathogenesis remains unclear. Small molecule tyrosine kinase inhibitors: Small molecule tyrosine kinase inhibitors represent a relatively new class of medications. Of these dasatinib has the strongest evidence in drug-induced pulmonary arterial hypertension, considered a recognized cause. Nilotinib, ponatinib, carfilzomib, and ruxolitinib are newer agents, which paradoxically have been linked to both cause and treatment for pulmonary arterial hypertension. Monoclonal antibodies and immune regulating medications: Several case reports have linked some monoclonal antibodies and immune modulating therapies to pulmonary arterial hypertension. There are no large series documenting an increased prevalence of pulmonary arterial hypertension complicating these agents; nonetheless, trastuzumab emtansine, rituximab, bevacizumab, cyclosporine, and leflunomide have all been implicated in case reports. Opioids and substances of abuse: Buprenorphine and cocaine have been identified as potential causes of pulmonary arterial hypertension. The mechanism by which this occurs is unclear. Tramadol has been demonstrated to cause severe, transient, and reversible pulmonary hypertension. Chemotherapeutic agents: Alkylating and alkylating-like agents, such as bleomycin, cyclophosphamide, and mitomycin have increased the risk of pulmonary veno-occlusive disease, which may be clinically indistinct from pulmonary arterial hypertension. Thalidomide and paclitaxel have also been implicated as potential causes. Miscellaneous medications: Protamine appears to be able to cause acute, reversible pulmonary hypertension when bound to heparin. Amiodarone is also capable of causing pulmonary hypertension by way of recognized side effects.

CONCLUSIONS

Pulmonary arterial hypertension remains a rare diagnosis, with drug-induced causes even more uncommon, accounting for only 10.5% of cases in large registry series. Despite several agents being implicated in the development of PAH, the supportive evidence is typically limited, based on case series and observational data. Furthermore, even in the drugs with relatively strong associations, factors that predispose an individual to PAH have yet to be elucidated.

Data-driven respiratory gating for ventilation/perfusion lung scan

BACKGROUND

Ventilation/perfusion lung scan is subject to blur due to respiratory motion whether with planar acquisition or single photon emission computed tomography (SPECT). We propose a data-driven gating method for extracting different respiratory phases from lung scan list-mode or dynamic data.

METHODS

The algorithm derives a surrogate respiratory signal from an automatically detected diaphragmatic region of interest. The time activity curve generated is then filtered using a Savitzky-Golay filter. We tested this method on an oscillating phantom in order to evaluate motion blur decrease and on one lung SPECT.

RESULTS

Our algorithm reduced motion blur on phantom acquisition: mean full width at half maximum 8.1 pixels on non-gated acquisition versus 5.3 pixels on gated acquisition and 4.1 pixels on reference image. Automated detection of the diaphragmatic region and time-activity curves generation were successful on patient acquisition.

CONCLUSIONS

This algorithm is compatible with a clinical use considering its runtime. Further studies will be needed in order to validate this method.

Fluoxetine protects against monocrotaline-induced pulmonary arterial remodeling by inhibition of hypoxia-inducible factor-1α and vascular endothelial growth factor

The selective serotonin re-uptake inhibitor fluoxetine has been shown to protect against monocrotaline (MCT)-induced pulmonary hypertension in rats. To investigate the possible role of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in mediating this protective effect, MCT-treated rats were administered fluoxetine by gavage, at doses of 2 mg/kg body mass or 10 mg/kg once daily for 3 weeks. Changes in pulmonary hemodynamic parameters, pulmonary artery morphologies, and expressions of HIF-1α and VEGF were assessed. Fluoxetine at the 10 mg/kg dose, but not at the 2 mg/kg dose, attenuated the effects of MCT on pulmonary artery pressure, right ventricle index, and medial wall thickness. In addition, 10 mg/kg fluoxetine mitigated the MCT-induced up-regulation of HIF-1α and VEGF protein and reactive oxygen species (ROS) in the lungs. This dosage also decreased pERK1/2 levels and inhibited proliferation of pulmonary arterial smooth muscle cells in MCT-treated rats. In conclusion, fluoxetine can protect against MCT-induced pulmonary arterial remodeling, which linked to reduced ROS generation and decreased HIF-1α and VEGF protein levels via the ERK1/2 phosphorylation pathway.

Influence of the ageing process on the resistive and reactive properties of the respiratory system

INTRODUCTION

In an increasingly old society, the study of the respiratory system changes and new techniques dedicated to older patients are of interest in physiologic studies as well as in the diagnosis of respiratory diseases.

OBJECTIVES

(1) To investigate the impact of ageing on the resistive and reactive properties of the respiratory system, and (2) to compare the easiness of accomplishment of spirometry and forced oscillation for assessing lung function.

METHODS

We conducted a cross-sectional study in which forced oscillation was used to investigate respiratory system resistive and reactive properties, while spirometry was used as a reference test to evaluate 80 normal subjects aged between 20 and 86 years. A questionnaire was used to evaluate the easiness of accomplishment of spirometry and forced oscillation.

RESULTS

There was a significant increase in the respiratory system resonance frequency (p<0.003) and a reduction in the mean reactance (p<0.004) with increasing age. Respiratory system resistance and dynamic compliance were not related to the ageing process. The easiness of accomplishment of forced oscillation measurements was greater than that of spirometry. This result was particularly relevant in subjects over 70 years old (p<0.05).

CONCLUSIONS

Respiratory system resistance and dynamic compliance are not modified with ageing. On the other hand, respiratory system homogeneity decreases during the ageing process. Forced oscillation is easy to perform and provides information complementary to spirometry. This technique may be a promising alternative and/or complement to other conventional exams used to evaluate older people who are unable to adequately perform spirometric tests.

Pathoetiological model of delirium: a comprehensive understanding of the neurobiology of delirium and an evidence-based approach to prevention and treatment

Delirium is the most common complication found in the general hospital setting. Yet, we know relatively little about its actual pathophysiology. This article contains a summary of what we know to date and how different proposed intrinsic and external factors may work together or by themselves to elicit the cascade of neurochemical events that leads to the development delirium. Given how devastating delirium can be, it is imperative that we better understand the causes and underlying pathophysiology. Elaborating a pathoetiology-based cohesive model to better grasp the basic mechanisms that mediate this syndrome will serve clinicians well in aspiring to find ways to correct these cascades, instituting rational treatment modalities, and developing effective preventive techniques.