Thursday, 28 November 2013

Pulmonary vascular disease – Pulmonary veno-occlusive disease – The Diagnosis

Pulmonary veno-occlusive disease (PVOD) is an extremely rare form of pulmonary hypertension, affecting mostly in children and young adults as a result of a progressive obstruction of small pulmonary veins that leads to elevation in pulmonary vascular resistance and right ventricular failure.
B. Diagnosis
Patients in the early stage with early pulmonary veno-occlusive disease (PVOD) may experience no symptoms at all, but the progression of diseasse may attributable to pulmonary hypertension and right-sided heart failure supervene(32).
B.1. Noninvasive diagnosis to detect PVOD(33)
A noninvasive diagnostic approach may include
1. Chest high-resolution computed tomographymay be helpful for clinical differential diagnosis of PVOD and PCH
In the study to examine chest HRCT images for four patients with idiopathic pulmonary arterial hypertension (IPAH), three patients with PVOD and three patients with PCH, and to evaluate pulmonary vascular casts of lung tissues obtained from those patients at lung transplantation or autopsy, found that
Measurement of the sizes of centrilobular GGOs in HRCT is a simple and useful method for clinical differential diagnosis of PVOD and PCH(34).
2. Arterial blood gas analysis(ABG)
The aim of the blood withdrawn from an artery, involving puncturing an artery with a thin needle and syringe is to determine the pH of the blood, the partial pressure of carbon dioxide and oxygen, the bicarbonate level and gas exchange which reflect gas exchange across the alveolar-capillary membrane(35).
3. Pulmonary function tests (PFT)
It is a complete evaluation of the respiratory system including patient history, physical examinations, chest x-ray examinations, arterial blood gas analysis, and tests of pulmonary function(36).
4. Bronchoalveolar lavage
Bronchoalveolar lavage has a well established role in the diagnosis of pulmonary infections, particularly those due to opportunistic organisms in an immunocompromised host with an aim to assess a number of pulmonary components of whchi may be useful in this regard, particularly if combined with new methods for examining inflammatory responses, such as those utilising the polymerase chain reaction to assess cellular expression for inflammatory cytokines and growth factors.(37).
5. Transthoracic Echocardiography
Transthoracic echocardiography is an important initial non-invasive diagnostic tool with aim to evaluate patients in whom pulmonary hypertension is suspected, according to the ACCF/AHA 2009 Expert Consensus Document on Pulmonary Hypertension(38).
6. Flow cytometry
Pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease (PVOD) both display occlusive remodeling of the pulmonary vasculature responsible for increased pulmonary vascular resistances. Cytotoxic T (CTL), natural killer (NK), and natural killer T (NKT) cells play a critical role in vascular remodeling in different physiological and pathological conditions. According to study, a
decrease in GNLY demethylation in the gDNA extracted from peripheral blood mononuclear cells and explanted lungs was found specifically in PVOD but not in PAH. This was associated with a decrease in populations and subpopulations of CTL and NKT and an increase of NK populations. Despite the reduced granulysin-containing cells in patients with PVOD, GNLY serum levels were higher, suggesting these cells were wasting their content. Furthermore, the increase of GNLY concentration in the serum of PVOD was significantly higher than in patients with PAH(39).
B.2. Surgical biopsy
Since surgical biopsy represents a high-risk procedure in these patients, it is contraindicated. lung biopsy or pathologic examination of pulmonary explants or postmortem lung samples. However, lung biopsy is hazardous in patients with severe pulmonary hypertension, and there is a need for noninvasive diagnostic tools in this patient population. Patients with PVOD may be refractory to pulmonary arterial hypertension (PAH)-specific therapy and may even deteriorate with it. It is important to identify such patients as soon as possible, because they should be treated cautiously and considered for lung transplantation if eligible(39).
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