Deep venous thrombosis after surgery for Achilles tendon rupture: a provoked transient event with minor long-term sequelae.

BACKGROUND: Deep venous thrombosis (DVT) occurs frequently in patients undergoing orthopedic surgery, but there is a lack of knowledge regarding long-term sequelae of DVT after different types of surgical procedures. OBJECTIVE: To describe the long-term effect of symptomatic (SDVT) and asymptomatic (ADVT) deep venous thrombosis on venous function and subsequent incidence of post-thrombotic syndrome (PTS) in patients who have undergone surgery for Achilles tendon rupture. PATIENTS/METHODS: This observational follow-up study includes 83 patients with postoperative DVT, examined after a mean of 7 years. There were two series of patients: 45 with SDVT and 38 with ADVT. In both series, more than 90% of the DVTs were limited to calf veins. Follow-up examinations comprised color duplex ultrasonography (CDU), strain-gauge plethysmography (SGP), clinical examination including scoring for venous disease and questionnaires for quality of life (QOL). RESULTS: A mild degree of PTS was found in 11% of the patients: 13% in SDVT and 8% in ADVT patients. The rate of recurrent ipsilateral DVT was 2%. Deep venous reflux was more common in patients with SDVT than in ADVT patients (84% vs. 55%, P < 0.01). Only a few patients had plethysmograpically abnormal findings without difference between the two groups. CONCLUSION: DVT after surgery for Achilles tendon rupture consists mainly of distal DVTs and are associated with a low risk for PTS. Deep venous reflux was more common in SDVT than in ADVT patients, probably as an effect of larger DVTs in the former group.

Asymptomatic deep venous thrombosis is associated with a low risk of post-thrombotic syndrome.

UNLABELLED: Post-thrombotic syndrome (PTS) is a well-recognized condition that develops after symptomatic deep venous thrombosis, but the clinical significance and late complications of asymptomatic deep venous thrombosis (ADVT) are unclear. OBJECTIVE: To determine whether ADVT following minor surgery affects venous function and contributes to the later development of PTS. PATIENTS/METHODS: The study included 83 patients operated on for Achilles tendon rupture; 38 patients with postoperative ADVT and 45 patients without (control group). The follow-up examinations five years after the operation comprised computerised strain-gauge plethysmography, colour duplex ultrasonography, clinical scoring of venous disease, and quality of life (QOL). RESULTS: Villalta scores, CEAP classification and QOL did not differ between groups. PTS (=Villalta score > or =5) was found in three ADVT patients (8%) and in two controls (4%). Ultrasonography revealed post-thrombotic changes in 55% of ADVT patients and in none of the controls. Deep venous reflux occurred in 22 ADVT patients and in three controls (P<0.001). There was no difference between groups in plethysmographic variables, demonstrating that the ultrasonographic abnormalities were of negligible haemodynamic significance. CONCLUSIONS: PTS is not a common sequel to ADVT after minor surgery. Although more than 50% of patients with ADVT developed post-thrombotic changes according to ultrasound, these changes did not result in haemodynamically significant venous dysfunction.

Dynamics of intramolecular contact formation in polypeptides: distance dependence of quenching rates in a room-temperature glass.

Quenching of the triplet state of tryptophan by cysteine is an important new tool for measuring the rate of forming a specific contact between amino acids in a polypeptide chain. To determine the length scale associated with this contact, tryptophan was embedded in a room-temperature glass containing a high concentration of cysteine. The decay of the triplet population is extended in time, consistent with a rate coefficient that decreases exponentially with distance. Solving the diffusion equation with this distant-dependent rate reproduces the observed bimolecular rates in water and shows that quenching at low viscosities takes place less than or similar to A from van der Waals contact between the tryptophan and cysteine.

Fast kinetics and mechanisms in protein folding.

This review describes how kinetic experiments using techniques with dramatically improved time resolution have contributed to understanding mechanisms in protein folding. Optical triggering with nanosecond laser pulses has made it possible to study the fastest-folding proteins as well as fundamental processes in folding for the first time. These include formation of alpha-helices, beta-sheets, and contacts between residues distant in sequence, as well as overall collapse of the polypeptide chain. Improvements in the time resolution of mixing experiments and the use of dynamic nuclear magnetic resonance methods have also allowed kinetic studies of proteins that fold too fast (greater than approximately 10(3) s-1) to be observed by conventional methods. Simple statistical mechanical models have been extremely useful in interpreting the experimental results. One of the surprises is that models originally developed for explaining the fast kinetics of secondary structure formation in isolated peptides are also successful in calculating folding rates of single domain proteins from their native three-dimensional structure.

Measuring the rate of intramolecular contact formation in polypeptides.

Formation of a specific contact between two residues of a polypeptide chain is an important elementary process in protein folding. Here we describe a method for studying contact formation between tryptophan and cysteine based on measurements of the lifetime of the tryptophan triplet state. With tryptophan at one end of a flexible peptide and cysteine at the other, the triplet decay rate is identical to the rate of quenching by cysteine. We show that this rate is also close to the diffusion-limited rate of contact formation. The length dependence of this end-to-end contact rate was studied in a series of Cys-(Ala-Gly-Gln)(k)-Trp peptides, with k varying from 1 to 6. The rate decreases from approximately 1/(40 ns) for k = 1 to approximately 1/(140 ns) for k = 6, approaching the length dependence expected for a random coil (n(-3/2)) for the longest peptides.