A novel modification of frozen elephant trunk technique: unique protocol from one institution.

OBJECTIVE: We aim to present a novel surgical technique of Frozen Elephant Trunk (FET) to treat complex thoracic aortic diseases in one stage and report its short-term outcomes. PATIENTS AND METHODS: Between December 2019 and 30 April 2021, twenty-five patients underwent FET operation at Viet Duc University Hospital. The mean age of the patients was 55.9 (±9.9, range 33-72) years. Eighteen (72%) of the patients were men. Thoracic aortic aneurysm was presented in three (12%) patients. Among seventeen (68%) of the patients undergoing the aortic dissection, eleven (44%) were treated acute type A aortic dissection. Type A intramural hematoma was presented in three (12%) patients. Four (16%) of the patients had undergone previous aortic operations, four (16%) of them had Marphan syndrome and two (11.1%) of them had stage 3 chronic kidney disease. All patients underwent FET procedure by unique protocol. Brain protection was achieved by antegrade bilateral selective cerebral perfusion and moderate hypothermia (28°C) in all cases; besides cerebral tissue oximetry monitoring was used to control brain oxygenation. RESULTS: There were no perioperative deaths, and all patients are still alive during mild-term follow-up period. Sixteen (88.9%) patients received isolated FET, while a Bentall procedure during FET was performed in two (8%) patients and right coronary artery bypass was in one (4%) case. The duration of cardiopulmonary bypass, cross-clamping, circulatory arrest, and total operation were 176.7 (±48.1, range 102-330), 106 (±39.8, range 63-205), 32.7 (±9.6, range 20-58), and 365.6 (±53.6, range 270-480) min, respectively. There was no bleeding following surgery. Prolonged ventilation required tracheotomy was documented in two (8%) patients, hemodialysis caused acute renal failure was in five (20%) patients, cerebral shock was in one (4%) patient, and type 1A endoleak in 2 (8%) patients. CONCLUSIONS: Our modification of FET technique was feasible, effective, and safe, with good postoperative outcomes.

Power stabilization of a diode laser with an acousto-optic modulator.

Laser power fluctuations can significantly reduce the device performances in various applications. High frequency fluctuations impact the signal-to-noise ratio, while slow variations can reduce the device repeatability or accuracy. Here we report experimental investigations on the power stabilization of a diode laser with an acousto-optic modulator. In the frequency domain, the relative power noise is reduced at the level of 2.2 × 10-8 Hz-1/2 in the range 1-100 kHz. The slow variations are studied in the time domain. The relative Allan standard deviation is measured at the level of 6 × 10-7 at 100 s averaging time. Above 100 s, the instability increases and reaches 2 × 10-6 at 10 000 s.

Note: Efficient diode laser line narrowing using dual, feed-forward + feed-back laser frequency control.

We have achieved distributed feedback laser diode line narrowing by simultaneously acting on the diode current via a feed-back loop and on an external electrooptic phase modulator in feed-forward actuator. This configuration turns out to be very efficient in reaching large bandwidth in the phase correction: up to 15 MHz with commercial laser control units. About 98% of the laser power undergoes narrowing. The full width at half maximum of the narrowed optical spectrum is of less than 4 kHz. This configuration appears to be very convenient as the delay in the feed-forward control electronics is easily compensated for by a 20 m optical fiber roll.