Frequency comb metrology with an optical parametric oscillator.

We report on the first demonstration of absolute frequency comb metrology with an optical parametric oscillator (OPO) frequency comb. The synchronously-pumped OPO operated in the 1.5-µm spectral region and was referenced to an H-maser atomic clock. Using different techniques, we thoroughly characterized the frequency noise power spectral density (PSD) of the repetition rate frep, of the carrier-envelope offset frequency fCEO, and of an optical comb line νN. The comb mode optical linewidth at 1557 nm was determined to be ~70 kHz for an observation time of 1 s from the measured frequency noise PSD, and was limited by the stability of the microwave frequency standard available for the stabilization of the comb repetition rate. We achieved a tight lock of the carrier envelope offset frequency with only ~300 mrad residual integrated phase noise, which makes its contribution to the optical linewidth negligible. The OPO comb was used to measure the absolute optical frequency of a near-infrared laser whose second-harmonic component was locked to the F = 2→3 transition of the 87Rb D2 line at 780 nm, leading to a measured transition frequency of νRb = 384,228,115,346 ± 16 kHz. We performed the same measurement with a commercial fiber-laser comb operating in the 1.5-µm region. Both the OPO comb and the commercial fiber comb achieved similar performance. The measurement accuracy was limited by interferometric noise in the fibered setup of the Rb-stabilized laser.

Successful repair of a right ventricular rupture at the atrioventricular groove.

We report a patient who presented with a delayed spontaneous right ventricular rupture at the anterior atrioventricular groove after open heart operation. Successful surgical repair consisted of reestablishing anterior atrioventricular groove continuity by pericardial patch placement on the arrested heart. We discuss the risk factors that could initiate the primary tear and contribute to the extension of this type of right ventricular rupture.

[Impact of organ shortage on the transplantation program]. / Impact de la pénurie d'organes sur un programme de transplantation.

The purpose of the study was to evaluate the consequences of a recent progressive shortage of donor organs on our different transplant programs. Although the waiting time before transplantation remained in general relatively short (4.6 [mean], 0-3, 0-10 months for renal, liver and heart transplantation, respectively), patients started to accumulate on our waiting list during the last year (1990) of the study (kidney transplantation). Furthermore some patients clearly deteriorated, other died awaiting transplantation (18% and 15% of the patients listed for liver and heart transplantation, respectively). In emergency, organs were provided most often by neighbouring foreign centers. Given these facts adhesion to supranational donor networks should be considered.

[Aortoiliac occlusive disease: yesterday and today]. / Les oblitérations aorto-iliaques: hier et aujourd'hui.

The surgical management of aortoiliac atherosclerotic occlusive disease includes endarterectomy and prosthetic by-pass in either the anatomical or extraanatomical position. Aortoiliac endarterectomy is only indicated in localized disease which spares the external iliac artery and does not exhibit aneurysmal changes. Prosthetic by-pass is easier to perform, but carries graft-related risks including anastomotic pseudoaneurysms in 5 to 10% of cases at 10 years. Extraanatomical shunts are performed when there are general or abdominal contraindications to an anatomical by-pass. Simultaneous revascularisation of the aortic visceral branches mainly involves the renal, inferior mesenteric and hypogastric arteries. Correction of celiac and superior mesenteric artery stenosis is less frequently indicated. The appropriate approach and surgical technique depend on the artery and the lesion involved. Suprarenal implantation of aortoiliac by-passes is performed at the celiac, descending aortic and ascending aortic levels. Indications include suprarenal coarctation of the aorta, reoperation following ligature of the juxtarenal aorta, and some cases of extensive thoracoabdominal atherosclerosis. The surgical management of aortoiliac occlusive disease in 353 patients treated in our clinic between 1976 and 1986 is reported. Mean follow-up exceeded 5 years. Operative mortality for endarterectomy (15 patients) was nil, and was 3.9% for by-pass graft. Early complication rate was 6.5% and late complication rate 23.2%. Half of the late complications were due to progression of the atherosclerotic process. Pseudoaneurysms at the aortic (3.1%) and femoral (9.9%) levels occurred between the fifth and tenth years. Prosthesis infection occurred shortly after operation in 3 patients and much later in 2 patients.

Indications for pericardial glutaraldehyde-preserved xenograft in repair of congenital heart disease.

A glutaraldehyde-preserved equine pericardial xenograft was implanted in 370 patients between 1981 and 1987; pericardial sac closure in 320 (mainly over Dacron implants), atrial repairs in 19, arterial reconstructions in 22 (right outflow tract in 19, Konno's procedure in three), control of bleeding after surgery for thoracic aneurysms in seven, control of plasma leaking PTFE graft in one, and repair of diaphragmal agenesia in one. Overall infection rate was 3/370 (0.8%). Epicardial adhesions (12) at reoperation for orthotopical implants were graded 1.3 +/- 0.9 on a scale of 6 (0 = no adhesions, 5 = calcified or ossified adhesions) after 4 +/- 2 months. Shrinkage of xenograft occurred in 3/19 (16%) atrial repairs and lesser degree aneurysmal dilatation appeared in 1/19 (5%) reconstructions of the right outflow tract. No complications occurred in the implants without direct exposure to the blood stream. We recommend pericardial xenograft for Konno's procedure and control of bleeding. It should not be used routinely in the low pressure side.

Repeat sternotomy after reconstruction of the pericardial sac with glutaraldehyde-preserved equine pericardium.

The risk of repeat sternotomy is higher than that of the initial sternotomy, especially if the pericardial sac was left open at the first intervention. In 200 consecutive patients with a pericardial defect after open heart operations, the pericardium was closed with a glutaraldehyde-preserved equine pericardial patch. Precardiac adhesions at reoperation were assessed in four groups of patients on a scale of 6, ranging from 0 (no adhesions) to 5 (calcified or ossified adhesions). Group I comprised 13 patients in whom the pericardium was left open at the first operation and an equine pericardial patch was implanted at reoperation. Group Ia included the first five Group I patients who underwent reoperation less than 1 year (early reoperation) after the initial procedure. Group Ib included the other eight patients of Group I, who underwent reoperation more than 1 year (late reoperation) after the first procedure. Group II comprised nine patients who were reoperated on after reconstruction of the pericardial sac with a glutaraldehyde-preserved equine pericardial patch. After a mean follow-up of 20.2 months, the incidence of patch-related complications was 1%. Statistical analysis shows less severe adhesions on reoperation in Group II patients (pericardial defect patched) than in Group I patients (pericardial defect left open): mean grade of adhesions 1.6 +/- 0.9 (Group II) versus 3.2 +/- 0.6 (Group I), p less than 0.001. Precardial adhesions with the pericardium left open were similar in patients having early and late reoperations: mean grade of adhesions 3.0 +/- 0.7 (Group Ia) versus 3.4 +/- 0.5 (Group Ib), no significant difference. Therefore, the glutaraldehyde-preserved equine pericardial patch can be considered a suitable material for primary closure of the pericardial sac in patients with inadequate autologous pericardium.