Mircea CINTEZA and Cristina DAIAN

Mankind evolution is towards progress. Sometimes, contrary to the wish, progress may bring regress and problems for a period, instead of a better life.

House dust mites are a good example. Parallel to the development of better living conditions in houses, they multiply and bring a pathology more and more spread and annoying. Asthma caused by house mites is more spread in economically developed countries and in people living in the best hygienic conditions. On the contrary, poor people living in bad houses and in the general conditions of a less developed country have much more rare asthma due to mites. One aspect of this apparent paradox is worth to be discussed.

Mites are minuscule arthropods belonging to the Arachnid class. They are spread almost in all human houses in humid, warm and temperate climate. Their dimensions — about one quarter of a millimeter — make them impossible to be perceived by common eyes. They live in the dust of a room (be it as clean as possible) and, especially, in beddings, pillows and mattresses, carpets and upholstered furniture.

The general rule is that they prefer a humid climate and a temperature level better towards warm than cold. In these conditions every female lays up to 100 eggs in her second half of life (5 out of 10 weeks). In 1 gram of dust there are up to 500 animals and each animal produces during its life more than 2000 fecal particles and much more enzyme covered dust particles, which are all highly allergenic. In these conditions it is believed that more than 1 billion people worldwide suffer of a form of chronic sensitization to house dust mites.

There are four main species of mites: Dermatophagoides pteronyssinus (Dp), mainly in Europe, Dermatophagoides farinae (Df), mainly in the USA, Blomia tropicalis (Bt), mainly in warm climates and Euroglyphus maynei, everywhere. Although there could be differences in their biology, the asthma symptoms produced are common and the therapeutic measures do not differ.

The main issue in treating asthma is prevention (primary prevention to avoid development of asthma and secondary prevention to avoid exacerbations). In respect to the house dust mite allergens, prevention may have the best results, but may be complicate.

One aspect is choosing the best material for beddings and pillows. It was thought that the feather filled pillows and duvets are a better habitat for mites. Recent studies showed the contrary. Kempt et al showed in their study polyester fiber pillows contained 8 times more mite antigen than feather pillows (1). Other studies found that unprocessed feather pillows contain important mite allergens, while processed feather filled pillows do not (2). New processed feather pillows put in a bedroom with high content of mite allergens did not become contaminated (2). Lots of offers for other material fillings for pillows and duvets are available, from which wool and cotton had most different types of offers. Finally, regarding these materials, it seems that unprocessed feathers are not adequate, while all others — processed feathers, polyester fibers, wool, cotton — are under debate.

Some advices may be however given. Use of encased mattresses, pillows and duvets has shown inconclusive results in adequate reduction in dust mite exposure. The humidity created between the warm body surface and the bedding is an excellent ambient for mites; in this respect it is discouraged to sleep with wet hair on the pillow. Bedding (sheets, pillowcases and blankets) should be washed weekly in hot water and ironed if possible.

Another advice is to put the pillows weekly in a cloth dryer at 105 degrees C, or in a cold dryer (3). Few people have these machines over the other many electronic machines in their houses. An alternative would be to wash the pillows in hot water at a few weeks interval. This is another impractical alternative, thinking only of the way to dry them. And in all cases, the same actions cannot be accomplished for duvets. We have to look for other possible measures against mites.

One measure is to use a good HEPA (highefficiency particulate air) filter vacuum cleaner in the house for floors and mattresses. This is a common alternative, but for dust mites there are also some other advices. It is better to avoid carpets, which are an important source of dust mites. Hard surfaces (wood, linoleum or tile) are preferred for flooring as are leather or vinyl furniture. It is not good to use humidification, because mites survive and multiply better in humid ambient. Indoor humidity should be kept between 35-40%. It was previously advised to use HEPA filters. These have higher prices than the common filters and the machine has to have a strong power necessary to circulate the air flow through a very dense filter. The vacuum machines clean the floor and the furniture, but not the air, or the bedding. However, the HEPA filters have minimal effect on dust mites particles, which are heavy and stay airborne only for a short period of time. They are more effective for pet dander, that is light and remains airborne for a longer time.

The question of humidification and filter is similar for air conditioners. Humidification is not good to stop mite development and HEPA filters have higher prices. Air conditioners mainly bring air into the room, while the inside air, which may contain mite particles from the floor and furniture, is not filtered. Split air conditioners have longer conducts in which bacteria, fungi and other microorganisms may develop and bring new allergens into the room . The cleaning and disinfection of such conducts is not very simple. So, common air condi tioners are only partially effective against indoor allergens in the rooms and particularly against house dust mites. They only help in humid climates by decreasing the indoor humidity below 40%.

Once the asthma due to dust mites develops, it is necessary to use medical therapies, various and efficient in different ways. It means some are acute therapies for crisis (exacerbations), some are long term therapies to treat chronic inflammation (inhaled corticosteroids, leukotriene modifiers), but some are long term therapies trying to desensitize. Subcutaneous immunotherapy (SCIT) is effective in decreasing dust mite sensitization, but gives some pain and necessitates precautions, carrying a small risk of anaphylaxis. Sublingual immunotherapy (SLIT) is developed more and more (Cytos Biotechnology, Stallergenes, ALK together with Merck and Torii Pharmaceuticals and many other). Sublingual immunotherapy tablets or sublingual drops may be used, and there are studies in which asthma went into complete remission in children even after 5 years after completing the sublingual immunotherapy (4). In another study 95% remission of dust mite induced asthma exacerbations in children was obtained by SLIT (5). SLIT appears safer and more accepted than SCIT, at least in Europe. In United States it is still under investigation, awaiting Food and Drug Administration approval.

However, the general primary and secondary prevention methods are at least as important as medical therapy, if they are efficient. Modern houses are built to be energy efficient. It means windows are very compact and often do not open, with minimal air exchange with the outdoor air. Indoor human activity generates high humidity. Heating, cooling and humidification are accomplished by dual function air conditioners. During winter this process is less active and high temperatures are often preferred, obtained by modern heating systems, with humidifying the indoor air for comfort. These measures lead to dust mite exposure all year round. Prevention of house dust mite allergy implies often refreshing of air, especially in winter, when the outdoor air is cold and dry. In warm season with humid climates and during of periods of high pollen season, it preferable to keep the windows closed and the air conditioners running. In summer in dry climates, dry air, which also comes free from outside, is to be preferred. The paradox is that the modern technologies do not easily fulfill the conditions. And the grand pa and ma advice, to largely open the widow of your bedroom two times a day, probably overpasses all the modern means of fight against house dust mite, along with ironing of sheets and pillowcases.

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Mircea CINTEZA

More than one year before I put a question in our journal (1): what is our goal in treating coronary disease: actual ischemia or future devastating ischemia? Actual ischemia is detected by usual tests, which are either not accurate (stress ECG, echocardiography, scintigraphic methods) or not directly linked to the risk of future infarction or coronary death (contrast coronarography). On the contrary, future devastating coronary ischemic events are demonstrated to come from angiographically non-critical stenosis (2). It is logical, because ”positive” remodelling of the vessel makes diseased coronary to enlarge when an atherosclerotic plaque grows. In this way stenosis does not increase, but the disease of the coronary is increasing. In an excellent paper, Aursulesei described in extenso the methods used today to identify the vulnerability of the coronary plaques to future major thrombosis and major coronary events (3).

In the last years the problem of the vulnerable plaque developed more and more. In the PubMed database there is a total of almost 2000 full text papers on this subject, from which 778 in the last five years. In the main congresses of cardiology and atherosclerosis the detection and the therapeutic ways to stabilize vulnerable plaques occupy central position. As far as atherothrombosis is the main killer in most countries and as far as a revolutionary way to cure it is developing, the eyes should be closely kept on this issue.

In fact, the concept of vulnerable plaque is not so young (4). In 1844 the first autopsy aspect of a ruptured atherosclerotic plaque was described and in 1858 Virchow developed the concept of a cyst of fatty material encapsulated in a fibrous cap. After 1987, when Glagov introduced the concept of positive remodeling in the exterior of the coronary lumen, the attention of research fell on the insignificant hemodinamically but dangerous in consequences small atherosclerotic plaques, called vulnerable plaques since 1989 (4). In 2000 Virmani and colleagues described this type of plaques as being thin-cap fibroatheroma (TCFA).

Today the TCFA are examined by multiple techniques applied in the humans in order to demonstrate the features which may give a precise risk evaluation and the consecutive therapeutic approach. There are invasive and noninvasive methods,

The most spread invasive method today is intravascular ultrasound (IVUS). There are several technical varieties: radiofrequency integrated backscatter, wavelet analysis, IVUS guided photoacoustic imaging and even more (5). Tissue penetration is good (about 10 mm), but the resolution is not as good as other techniques. It was the first technique to create a virtual histopathology of the plaque.

Optical coherence tomography is in an asto nishing rapid progress, as far as the technology permitted the use of less than 3 French catheters in any large and medium coronaries. The resolution is the best in the field (less than 15 micrometers), but the tissue penetrance is weaker (less than 2.5 mm). The sensitivity versus histopathology to detect thin cap plaque atheroma is about 80%, but the specificity is 90% (5).

Coronary angioscopy necessitates a 4 or 5 French catheter, which makes it available for large and medium coronaries. A baloon is used to block bood flow for a few seconds and a flush is performed before the angioscopic evaluation of the coronaries. Several clinical studies regarding the role of therapy (statins) to stabilize plaques were conducted by angioscopy (5).

From the noninvasive methods, coronary computed tomography is a robust approach, with an accuracy of more than 90% in respect of the IVUS virtual histopathology in evaluating the vulnerable plaque.

Magnetic resonance imaging (MRI), with the use of paramagnetic particles when necessary is, as in many other fields, the most promising method in coronary atherosclerosis evaluation, because has the potential to offer high quality functional histopathologic imaging.

Positron emission tomography (PET) is still in search of its role, because very many radiotracers are checked in order to be detected after accumulating in the atherosclerotic plaque.

Noninvasive termography developed recently, trying to identify differences in temperature between various vascular atherosclerotic targets. Invasive termography, used in the past, seems to loose its importance.

Hybrid methods are also developed, like the combination of functional histology methods of PET and MRI. Such methods could answer more quickly to the question which parameter has more value in defining the risk of developing acute atherothrombosis.

Multiple clinical trials were accomplished or are in development (3). One of the most interesting is The High-Risk Plaque intiative, which includes the Bio Image Study (6). A more than 7000 subjects are already checked byvarious methods, including, for selected groups, evaluation by contrast enhanced tomography, MRI, PET and multiple biomarkers. The protocol is serious and very ellaborated (6). Now the follow up is in progress, with the goal is to develop a powerfull indicator of major adverse athero thrombotic events after a medium term evolution.

New complex indicators for major atherothrombotic events in asymptomatic population are developing. The technical difficulties and the costs are high. However the moment when we will use them in clinical practice seems to be not so far.

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