Although the risk of deep vein thrombosis (DVT) is increased in any situation involving prolonged immobility of the limbs, the recent occurrence of several well-publicized cases of DVT in long-haul air line passengers who have been sitting in relatively cramped conditions for extended periods has focused attention on the so-called "economy class syndrome." Relatively straightforward preventive measures, such as carrying out simple exercises to avoid venous stasis, have even led some commentators to suggest that "economy class syndrome" is a misnomer, since the increased comfort of first class or club class seats is a disincentive for the passenger to move. According to this theory, the sheer lack of comfort of economy class seating results in passengers constantly moving as they try to get more comfortable, thereby assisting venous return to the legs.
More justifiably, it could be claimed that those flying first class or club class tend to be older, more affluent, have had more surgical operations and overall to have acquired more of the known risk factors for DVT. Despite the considerable publicity which has accompanied the situation, there are few reliable statistics or studies regarding rates of occurrence of travel-associated DVT, although one study found that 18% of all sudden deaths in long-distance air passengers were due to pulmonary embolism, making this the second-most-common cause of such deaths, after ischemic heart disease.
Simple in vitro diagnostic tests can play a significant role in screening patients for DVT, or more importantly, in definitively ruling it out. Of the parameters available the measurement of D-dimer has been suggested as being potentially the most useful, with a number of rapid immunochromatography tests having recently been launched in Europe.
Roche Diagnostics (Mannheim, Germany) has one of the earliest tests available, the Cardiac d-dimer which will rapidly rule out DVT or PE in patients with inconclusive symptoms. Using the Roche desktop Cardiac reader system, a result is available in eight minutes. Teco (Neufahrn, Germany) has recently launched an 80-second quantitative assay using an optical laser instrument and agglutinating latex particles, and Biopool (Umea, Sweden) has developed Auto.Dimer reagents which were originally designed for use on clinical chemistry analyzers. Applications have been developed for use of the reagents with a number of coagulation analyzers, including the Thrombolyzer RackRotor/Compact XR, the Sysmex CA-7000, BCT and ACL Futura models.
Because of the relatively ill-defined nature of the D-dimer antigen itself, results from different commercially available tests can be difficult to compare. Biopool says that excellent correlations between different analyzer systems have been obtained for tests using their reagents on the Hitachi 911 clinical chemistry analyzer, the Thrombolyzer XR, BCT and Sysmex CA-7000. Positive D-dimer test results will require further testing before a DVT diagnosis can be confirmed. Lower limb compression ultrasonography or helical CT scan is common in Europe as a second-stage test on positive D-dimer results.
Shortage of cardiologists in France
The Soci t Francaise de Cardologie has reported concern over a report issued at the end of last year by the Ministry of Health predicting that the number of practicing cardiologists in France is likely to remain stable at its current level of about 5,600 until 2005, and then slowly decline by 3.5% to 2010, and more rapidly by 13.4% by 2015 and 23.1% by 2020, reducing by then to the level existing in 1990, at 4,265 specialists. Just under 58% of French cardiologists are in private practice and 40.7% work exclusively in hospitals, three-quarters of them in government-financed institutions with only one-quarter in private for-profit clinics. There are currently about 300,000 cath lab procedures each year in France, and 700,000 new thrombotic episodes, of which 20,000 evolve to fatal pulmonary embolisms.
Central venous catheters and infection
There are approximately, 6,000 patients each year in Britain who acquire a catheter-related blood stream infection associated with the use of a central venous catheter, according to Professor David Williams of the department of clinical engineering at the University of Liverpool (Liverpool, UK). This can have a significant effect on their overall prognosis, it lengthens their stay in hospital and significantly increases the cost of their treatment.
This risk of infection, Williams said, has been the focus of a number of studies attempting to identify factors controlling susceptibility to infection, and in particular whether catheter material can effect catheter-related blood stream infections. Last year the UK Department of Health issued guidelines for preventing infections associated with central venous catheters," which confirmed that there was no evidence that such infections were material-related. Williams pointed out that microorganisms are far more likely to accumulate in, and pass through, the channel in the tissue created by the catheter. In reality, he said, few of the microorganisms will come into contact with the catheter material and the nature of the material will not affect most of them.
The search for a microorganism-resistant material may therefore be an irrelevance, according to Williams. He suggests that antimicrobial agents used in impregnating or coating catheters may reduce the risk of infections in patients at high risk in short- or long-term cases, but that in situations where there is a generally low risk, there was no perceptible difference.
Cardiovascular rehab system from Poland
Aspel (Zahierzow, Poland) has developed the Aster rehabilitation system for cardiac patients that can offer a group program, but with individual treatment protocols for each patient. The system consists of a central processing unit complemented by treadmills or ergometers. Training programs can be controlled by heart rate or load with ECG, heart rate and blood pressure continuously monitored and screen displayed. The Giotto Holter ECG analysis system from H&C Medical Devices (Sesto S. Giovanni, Italy) can download and analyze 24 hours of patient data in under two minutes with the software program operating in the MS Windows (98/ME and 2000) environment. Up to 200 complexes of ventricular, supraventricular and normal events can be visualized and edited. Also from Italy, a digital ECG acquisition module from Ates Medical Devices (Colognola ai Colli, Italy) can be connected to a PC via a standard serial port for data analysis, so equipping a personal computer with ECG functionalities. The Easy ECG Plus is the 12-lead acquisition module.
MRI during stress testing
Lode (Groningen, the Netherlands) has developed a line of MRI-compatible ergonometers that can be used with MR scanners from GE Medical Systems (Waukesha, Wisconsin), Philips (Best, the Netherlands) and Siemens (Erlangen, Germany). The electromagnetically braked ergometer can be placed on the examination table so that the time between stress induction and imaging is minimized. The company says that it is possible to gather MR images yielding information about ventricular function, valvular function, wall motion and myocardial perfusion during stress testing with heart rates above 100 bpm.
Ultrasound and ECG
Fukuda Denshi (Toyko) has launched in Europe its FCU-2000 unit, combining diagnostic ultrasound capabilities with interpretive ECG functionalities in a single system. At the touch of a button, users are offered the possibility to select either modality with separate dedicated keypads for each function. For cardiovascular diagnosis, a high-frame mode permits detailed observation of rapid valvular movements both in real time and from cine memory images.