Prognostic factors in severe twin-twin transfusion syndrome treated by endoscopic laser surgery.
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OBJECTIVE: The aim of this study was to investigate clinical and sonographic parameters, in particular Doppler blood flow measurements, in severe second-trimester twin-twin transfusion syndrome before and after endoscopic laser coagulation of the placental vascular anastomoses, to correlate these data with fetal outcome and to determine whether fetal blood flow measurements could help to estimate the probability of fetal survival. METHODS: In 121 cases of severe twin-twin transfusion syndrome examined between 17 and 26 weeks of gestation, the following investigations were performed: fetal biometry, placental location, deepest pool of amniotic fluid, echocardiography and Doppler sonography of the umbilical arteries and the ductus venosus of both twins before and after fetoscopic laser ablation of the placental anastomoses. RESULTS: The overall survival rate was 64% (156/242). Both fetuses survived in 48% (58/121) and one fetus survived in 33% (40/121), resulting in 81% (98/121) of pregnancies with at least one survivor. Gestational age at the time of the procedure and placental location had no significant influence on fetal survival. The amniotic fluid volume drained after laser coagulation correlated significantly (p = 0.038) with the risk of miscarriage or extremely premature delivery within 4 weeks of the procedure. Intertwin discrepancy in abdominal circumference showed a significant negative correlation (p = 0.004) with the probability for survival of donor fetuses. Before the procedure, 19% (23/121) of donor twins and 5% (6/121) of recipient twins showed absent or reversed end-diastolic flow in the umbilical artery (p = 0.001). This finding had no significant influence on the survival rate of donors. An increase of waveform indices in the umbilical artery 1 day after the procedure compared to immediately after the procedure correlated significantly with a lower probability for survival of donors (p = 0.042) and recipients (p = 0.018). Before the procedure, 37% (45/121) of recipient twins and 9% (10/113) of donor twins showed absent or reversed flow during atrial contraction in the ductus venosus (p < 0.0001). This finding had a significant negative influence on the survival rate of recipient fetuses (p = 0.02). Furthermore, an increase of waveform indices in the ductus venosus 1 day after the procedure compared to immediately after the procedure correlated significantly with a lower probability of survival in recipients (p = 0.005). CONCLUSIONS: Fetoscopic laser coagulation of the placental vascular anastomoses in severe mid-trimester twin-twin transfusion is a potentially corrective and effective, minimally invasive procedure. Doppler investigation of the umbilical and fetal circulations provides important information on the fetal condition, prognosis and therapeutic effects of the intervention. Signs of congestive heart failure in the recipient may reduce the probability of survival, whereas increased placental resistance in the donor before the procedure is not necessarily associated with a reduction in the probability of survival after laser coagulation. (+info)
Antenatal visualization of vascular anastomoses in monochorionic twins using color Doppler sonography: the protective function of these anastomoses and the phenomenon of interference beating.
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This report concerns the antenatal visualization and velocimetry of an arterioarterial and a venovenous anastomosis in a monochorionic twin pregnancy using color Doppler sonography. The phenomenon of 'interference beating' occurs when two flow velocity waveforms are superimposed in one blood vessel. This characteristic image can be generated antenatally to confirm the existence of a vascular communication. We were able to reveal these anastomoses postnatally using the dye injection technique. (+info)
Microvascular arteriovenous shunting is a probable pathogenetic mechanism in erythromelalgia.
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Erythromelalgia is a condition consisting of red, warm, and burning painful extremities. Symptoms are relieved by cold and aggravated by heat. A wide variety of etiologic conditions can cause erythromelalgia, but one common pathogenetic mechanism, microvascular arteriovenous shunting, has been hypothesized. The aim of this study was to test this hypothesis. Quantification of skin microvascular perfusion using laser Doppler perfusion imaging and skin temperature at rest and after central body heating was performed in 14 patients with erythromelalgia and 11 controls. Attacks of erythromelalgia were induced in eight patients after heat provocation. In the plantar region of the foot, the location of numerous anatomical arteriovenous shunts, these patients significantly increased the skin perfusion as compared with asymptomatic patients with erythromelalgia and controls. In the dorsal region with few arteriovenous shunts no significant differences between the groups were demonstrated. The results show a relation between clinical symptoms and increased perfusion in the region of numerous anatomical arteriovenous shunts, and support the hypothesis of increased thermoregulatory arteriovenous shunt flow during attacks in primary erythromelalgia. (+info)
Doppler sonographic demonstration of arterio-venous anastomosis in monochorionic twin gestation.
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Arterio-venous connections, which are known to occur in monochorionic twin placentae and are a mechanism for the development of twin-to-twin transfusion syndrome, can be demonstrated in utero by means of targeted sonography with the use of spectral and color flow Doppler techniques. (+info)
Identification of arterio-venous anastomoses in vivo in monochorionic twin pregnancies: preliminary report.
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OBJECTIVE: To determine whether it is possible to identify in vivo placental arterio-venous anastomoses (AVAs) by color Doppler flow mapping. METHODS: Three monochorionic twin pregnancies (one with and two without twin-to-twin transfusion syndrome) underwent placental mapping by color Doppler ultrasound. Placental vessels along the chorionic plate were recorded together with the direction of blood flow and their location in relation to the cord insertions and to superficial arterio-arterial anastomoses. Suggestive AVAs were mapped topographically and results were compared with the findings of formal postnatal placental injection studies. RESULTS: An AVA was identified in each of the three cases. Injection studies showed multiple AVAs. Each antenatally identified AVA was confirmed at placental injection study. Their placental location correlated to other landmarks as predicted by ultrasound. CONCLUSIONS: This preliminary report demonstrates that AVAs can be identified using color Doppler ultrasound. This may facilitate planning for highly selective ablation of AVAs, and shorter procedure times. Formal studies are now indicated to determine the accuracy of this technique. (+info)
Selective versus non-selective laser photocoagulation of placental vessels in twin-to-twin transfusion syndrome.
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OBJECTIVE: We have recently described a surgical technique for the treatment of twin-to-twin transfusion syndrome (TTTS) that allows precise identification of vascular anastomoses (selective laser photocoagulation of communicating vessels, or S-LPCV). The purpose of this study was to compare S-LPCV with the previous non-selective technique (NS-LPCV) that targeted all vessels crossing the dividing membrane. MATERIALS AND METHODS: Patients with TTTS were treated with NS-LPCV from May 1994 to June 1997 and with S-LPCV from July 1997 to December 1999. TTTS was defined as polyhydramnios of > or = 8 cm maximum vertical pocket (MVP) in the recipient twin and oligohydramnios of < or = 2 cm MVP in the donor twin. Outcome was measured as survival per number of pregnancies and per number of fetuses together with limited morbidity data. RESULTS: NS-LPCV was used in 18 patients and 74 were treated with S-LPCV. Three patients interrupted their pregnancies electively after surgery (S-LPCV) and were removed from further analysis. Survival of at least one fetus was higher in S-LPCV (83.1%) than in NS-LPCV (61.1%) (P = 0.04), mostly due to a lower rate of dual intra-uterine fetal demise in S-LPCV (5.6%) than in NS-LPCV (22%) (P = 0.05). There were more hydropic fetuses in the NS-LPCV group (27%) than in the S-LPCV group (5.4%), but this difference did not account for the results. There was no difference in the survival per number of fetuses between the two groups. CONCLUSIONS: S-LPCV represents an important evolution in the surgical treatment of TTTS. The use of this technique by all centers should allow better comparison of fetal survival and morbidity rates. S-LPCV should be the standard technique in trials comparing amniocentesis versus laser for the treatment of severe TTTS. (+info)
Studies on the structure and permeability of the microvasculature in normal rat lymph nodes.
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The structure and permeability of the microvasculature in normal rat lymph nodes was studied by regional perfusion techniques. The results indicated that characteristic vascular units supplied each cortical lobule of lymphatic tissue. Numerous arteriovenous communications and venous sphincters innervated by unmyelinated nerve fibers were found in this vascular bed. These specialized vascular structures permitted regional control of blood flow through high endothelial venules. Lymphocytes migrated across these venular walls by moving through intercellular spaces in the endothelium and between gaps in the laminated, reticular sheath. No direct anastomoses between blood vessels and lymphatics were seen, but tracer studies with horseradish peroxidase suggested that functional lymph node-venous communications were present in the walls of high endothelial venules. (+info)
Popliteal-crural bypass through the posterior approach with lesser saphenous vein for limb salvage.
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PURPOSE: A review of popliteal-crural bypasses via the posterior approach was done to evaluate the results of this technique. METHODS: During a period of 36 months, 21 patients with limb-threatening ischemia underwent 21 popliteal-crural bypasses via the posterior approach in the prone position with reversed lesser saphenous vein. All patients had limb-threatening ischemia, with rest pain in five patients, ulceration in nine patients, and gangrene in seven patients. Diabetes mellitus was present in 17 patients. RESULTS: The inflow site was the supragenicular popliteal artery in 12 patients and the infragenicular popliteal artery in nine patients. The outflow sites were the tibioperoneal trunk in five patients, the posterior tibial artery in six patients, the peroneal artery in eight patients, and the anterior tibial artery in two patients. Of the seven patients with gangrene, three patients underwent transmetatarsal amputation and four underwent toe amputation. The limb salvage rate for the entire group was 100% at 24 months. No early graft failures were seen, and the 12-month and 24-month primary graft patency rates were 89% and 77%, respectively, with life-table analysis. The primary assisted patency rate was 95% at 12 and 24 months. Patency was determined with duplex scan graft surveillance. CONCLUSION: The posterior approach to popliteal-distal bypass is an acceptable alternative to traditional bypass procedure with excellent early patency and limb salvage results. The approach has the advantage of better utilization of lesser saphenous vein and easier operative exposure in patients with short segment infrapopliteal occlusive disease. (+info)