Translation-covariant Markovian master equation for a test particle in a quantum fluid

A recently proposed master equation in the Lindblad form is studied with respect to covariance properties and existence of a stationary solution. The master equation describes the interaction of a test particle with a quantum fluid, the so-called Rayleigh gas, and is characterized by the appearance of a two-point correlation function known as dynamic structure factor, which reflects symmetry and statistical mechanics properties of the fluid. In the case of a free gas all relevant physical parameters, such as fugacity, ratio between the masses, momentum transfer and energy transfer are put into evidence, giving an exact expansion of the dynamic structure factor. The limit in which these quantities are small is then considered. In particular in the Brownian limit a Fokker-Planck equation is obtained in which the corrections due to quantum statistics can be explicitly evaluated and are given in terms of the Bose function $g_0 (z)$ and the Fermi function $f_0 (z)$.Comment: 18 pages, revtex, no figures, to appear in J. Math. Phy

Subdynamics as a mechanism for objective description

The relationship between microsystems and macrosystems is considered in the context of quantum field formulation of statistical mechanics: it is argued that problems on foundations of quantum mechanics can be solved relying on this relationship. This discussion requires some improvement of non-equilibrium statistical mechanics that is briefly presented.Comment: latex, 15 pages. Paper submitted to Proc. Conference "Mysteries, Puzzles And Paradoxes In Quantum Mechanics, Workshop on Entanglement And Decoherence, Palazzo Feltrinelli, Gargnano, Garda Lake, Italy, 20-25 September, 199

A classical appraisal of quantum definitions of non-Markovian dynamics

We consider the issue of non-Markovianity of a quantum dynamics starting from a comparison with the classical definition of Markovian process. We point to the fact that two sufficient but not necessary signatures of non-Markovianity of a classical process find their natural quantum counterpart in recently introduced measures of quantum non-Markovianity. This behavior is analyzed in detail for quantum dynamics which can be built taking as input a class of classical processes.Comment: 15 pages, 6 figures; to appear in J. Phys. B, Special Issue on "Loss of coherence and memory effects in quantum dynamics

Surgical "elephant trunk" arch replacement with a branched arch prosthesis: two alternative operative techniques

Introduction: Elephant trunk repair of the aortic arch cannot be performed with a branched prosthesis. Aim: We conceived two different modifications of the original technique to perform an arch replacement with a branched graft, while arranging an adequate landing zone for a subsequent thoracic endovascular aortic repair, without the need of dedicated material. Material and methods: Eight consecutive patients underwent arch replacement with one of our techniques. Five were emergency patients with acute aortic dissection, and 3 suffered chronic expansive disease. The "modified elephant trunk" includes a separate anastomosis of an endo-luminal prosthetic segment in the descending aorta. Subsequently, the branched arch prosthesis is anastomosed to the distal aortic stump with the attached trunk. In the "prophylactic debranching", a tail is left on the distal end of the arch prosthesis, so that the branches for the supra-aortic vessels will remain displaced proximally, allowing a "zone 1" available for landing. Results: Three patients experienced transient cerebral deficits (1 transient ischemic attack and post-operative delirium in 2 cases), 1 required re-operation for bleeding and 2 needed prolonged intubation. One died of multi-organ failure. Conclusions: Both techniques proved to be easily reproducible, and allow an adequate landing zone for a subsequent endovascular procedure, while retaining the advantages of using a tetra-furcated prosthesis. They are a viable alternative when a hybrid prosthesis cannot be implanted

Reply to Comment on "Completely positive quantum dissipation"

This is the reply to a Comment by R. F. O'Connell (Phys. Rev. Lett. 87 (2001) 028901) on a paper written by the author (B. Vacchini, ``Completely positive quantum dissipation'', Phys.Rev.Lett. 84 (2000) 1374, arXiv:quant-ph/0002094).Comment: 2 pages, revtex, no figure

Long-term follow-up of device-assisted clampless off-pump coronary artery bypass grafting compared with conventional on-pump technique

Study objective: To evaluate the long-term outcomes of clampless off-pump coronary artery bypass grafting (C-OPCAB) compared with conventional on-pump double clamping coronary artery bypass grafting (C-CABG). Methods: From October 2006 to December 2011, 366 patients underwent isolated coronary artery bypass grafting. After propensity score matching of preoperative variables, 143 pairs were selected who received C-OPCAB with the use of device-assisted PAS-Port proximal venous graft anastomoses or C-CABG, performed by the same surgeon experienced in both techniques. Data of the two groups of patients were retrospectively analyzed up to 14 years of follow-up. Results: As compared with C-OPCAB, in the C-CABG patients, the performed number of grafts per patient was higher (2.9 +/- 0.5 vs. 2.6 +/- 0.6, p-value 0.0001). At 14 years, overall survival, including in-hospital death, was 64 +/- 4.7% for the C-OPCAB vs. 55 +/- 5.5% for the C-CABG, freedom from overall MACCEs 51 +/- 6.2% vs. 41 +/- 7.7%, and from late cardiac death 94 +/- 2.4% vs. 96 +/- 2.2% (p-value not significant, for all comparisons). No significant statistical differences were observed in the actual rates of adverse events during follow-up. Independent predictors of survival were advanced age at operation (p-value 0.001) and a lower mean value of preoperative left ventricular ejection fraction (p-value 0.015). Conclusions: Our single-center study analysis suggests that clampless OPCAB using device-assisted proximal anastomoses proved to be not inferior to double-clamping CABG in the long-term follow-up, provided that involved surgeons are familiar with both techniques. These conclusions are supported by a large and long-term follow-up period, eliminating potential bias, i.e., by means of the propensity score matching and analyzing single-surgeon experience

The effects of DeBakey type acute aortic dissection and preoperative peripheral and cardiac malperfusion on the outcomes after surgical repair

Introduction: Emergent surgical repair of DeBakey type I and II acute aortic dissection represents the standard of care to prevent lethal complications. Aim: Evaluation of the effect of extension of aortic dissection (AAD) according to DeBakey classification, type I and II AAD, and the relationship with preoperative peripheral and myocardial malperfusion on early outcome and the mid-term follow-up period. Material and methods: A total of 135 patients who underwent AAD surgery between January 2015 and October 2019 were analysed. Results: In total 103 patients were affected by DeBakey type I AAD and 32 by DeBakey type II; 56 patients preoperatively showed peripheral, cardiac malperfusion, or both. Intra-operative mortality was 11%. Postoperative peripheral, cardiac malperfusion, and intraoperative and postoperative mortality were lower for type II AAD. The protective factor for intra- and postoperative 60-day mortality was type II AAD (RR = 0.03, p = 0.001); independent predictors were hypertension, and preoperative cardiac and renal-visceral malperfusion. At 5 years the overall survival was 74 ±6.9%. Independent predictors of reduced survival were major extension of type I AAD (RR = 5.37, p < 0.05) and preoperative cardiac malperfusion (RR = 5.78, p < 0.05). Five-year freedom from cardiac death, redo surgical operation, and new vascular procedures on the thoracic and abdominal aorta was 92 ±5.7%, 99 ±1.2%, and 81 ±7.2%, respectively. Extension of DeBakey type I AAD into the thoracic-abdominal aorta segment was also a predictor of the need for new vascular procedures (RR = 1.66, p = 0.05). Conclusions: A more favourable anatomy of DeBakey type II AAD is associated with better early and late outcomes after aortic repair. This is due to a lower incidence of peripheral and cardiac malperfusion

The impact of dual antiplatelet therapy administration on the risk of bleeding complications during coronary artery bypass surgery

Introduction: Dual antiplatelet therapy reduces the risk of cardiovascular death, myocardial infarction and recurrence of adverse ischemic events in patients affected by acute coronary syndromes, but in patients urgently needing coronary artery surgery it can increase the risk of severe perioperative bleeding complications. Aim: We evaluated the impact of dual antiplatelet therapy (DAPT) based on acetylsalicylic acid plus clopidogrel or ticagrelor in patients undergoing coronary artery bypass grafting (CABG). Material and methods: Three hundred and thirty-three patients underwent coronary artery bypass grafting with DAPT discontinuation > 72 hours or 3-4 days (group A, n = 159), 48-72 hours or 2-3 days (group B, n = 126), < 24 hours or 0-1 day (group C, n = 24) prior to CABG. Results: Operative mortality was 1.87% (group A), 0.79% (group B), absent (group C). The incidence of mediastinal re-exploration was 1.25% or 2 patients (group A), 1.59% or 2 patients (group B), 8.33% or 4 patients (group C) (p = 0.01). Group C showed postoperatively a greater incidence of a blood loss greater than 500 ml at 6 hours and a blood loss from chest tube drainages significantly higher at 6 and 24 hours (p < 0.01). Multivariate analysis showed that ongoing ticagrelor intake in group C (HR = 42.4; p = 0.02) and group C (HR = 6.9; p = 0.04) were the only independent predictors of surgical re-exploration. In group C, surgical re-exploration was 2.56% or 1/39 patients taking clopidogrel, 33.3% or 3/9 patients taking ticagrelor (p = 0.002). Conclusions: Dual antiplatelet therapy ongoing until 1 day or 24 hours before CABG showed a significantly increased risk of bleeding complications in comparison with its discontinuation at 2-3 and > 3-4 days before, respectively. Major blood loss and surgical re-exploration were not associated with increased risk of operative all-cause or bleeding-related mortality. As expected, taking ticagrelor compared with clopidogrel in the short interval confers a higher risk of bleeding complications

Mid-term results of mitral valve replacement and repair: current clinical experience, technical aspects, and risk factor analysis

Aim: we evaluated the short- and mid-term results of mitral valve replacement (MVR) and mitral valve repair (MV-repair). Methods: in total, 168 patients (mean age 67 ± 11 years) underwent MVR (n = 104) and MV-repair (n = 64). To treat posterior leaflet disease, MV-repair techniques included triangular or quadrangular resection (n = 38), P1-P2 plication (n = 4), side-to side P1-P2 (n = 1), posterior-medial commissure-plasty (n = 1), and annuloplasty (n = 20). A prosthetic ring was implanted in all patients. In the presence of degenerative disease involving the anterior leaflet, extensive myxomatous and/or prolapsing pathology of the entire valve, and/or rheumatic and endocarditis degeneration, surgical orientation was to perform MVR directly. When possible, the sub-valvular apparatus with its papillary muscle was partially preserved. The mean follow-up was 38 ± 22 months. Results: operative mortality (0.96% vs. 1.56%) and six-year survival (94% vs. 100%) were similar in MVR and MV-repair. The only independent predictor of late survival was advanced age at the operation (79.2 years vs. 66.4 years; P = 0.012). Freedom from redo-operation was 100%. Partial preservation of the sub-valvular apparatus with its papillary muscle during MVR allowed postoperatively a better left ventricular function with similar values achieved with MV-repair (P = 0.05), and it was a protective factor against the development of left ventricular dysfunction during follow-up (P = 0.01). Conclusion: MVR and MV-repair are associated with satisfactory results in the short and medium term. MV-repair to treat posterior leaflet disease is associated with a stable and long-lasting result; MVR allows equally satisfactory results in the presence of more extensive and more complex mitral valve disease. Partial preservation of the subvalvular apparatus favors a better left ventricular systolic function

Early and mid-term results in patients undergoing primary CABG in comparison with patients with PCI prior to CABG

Aim: We evaluated the impact of prior percutaneous coronary intervention (PCI) on early and mid-term results in patients undergoing coronary artery bypass grafting (CABG). Methods: Between 2015 and 2020, 938 consecutive patients (mean age 67.4 ± 9.11 years) underwent CABG with prior PCI (n = 121) or primary CABG (n = 817). The mean follow-up was 37 ± 25 (median 36) months. Kaplan- Meier estimates were used to assess survival rates, while Logistic and Cox model analysis regressions assessed the risk of prior PCI and other variables. Results: Six-year survival including in-hospital mortality was 79% ± 6% in CABG with prior-PCI patients vs. 88% ± 2% in primary CABG (P = 0.002). As compared with primary CABG, in prior-PCI patients, clinical presentation (acute coronary syndrome, reduced left ventricular ejection fraction, and previous myocardial infarction, P ≤ 0.01, for all comparisons) was worse, comorbidity increased (Euroscore-2, severe chronic renal dysfunction, P < 0.01), and in-hospital mortality was higher (6.6% or 8 patients vs. 1.6% or 13 patients, P < 0.001). Prior PCI was found to be an independent predictor of mortality (HR = 4.23; P = 0.01). Six-year freedom from late all-cause death and cardiac death were 84% ± 6% vs. 90% ± 2% (P = 0.2) and 96% ± 2% vs. 96% ± 1% (P = 0.5), respectively. Independent predictors of all-cause death were advanced age at the operation (P < 0.0001), reduced left ventricular ejection fraction (P = 0.01), severe chronic renal dysfunction (P = 0.02), prior PCI (P = 0.03), and Euroscore-2 (P = 0.05). Prior PCI did not negatively affect late cardiac death (P = 0.5). Conclusion: Patients undergoing CABG after prior PCI have worse perioperative outcomes. Mid-term reduced survival in the prior-PCI patients is mainly due to the concomitant presence of worse clinical presentation and increased comorbidity. Freedom from cardiac death is comparable and satisfactory in both cohorts, highlighting the positive protective effect of CABG over time