Search

The MITRAL (Mitral Implantation of Transcatheter Valves) trial is the first prospective study for valve-in-mitral annular calcification (ViMAC), mitral valve-in-ring (MViR), and mitral valve-in-valve (MViV) using balloon-expandable aortic transcatheter heart valves. Procedural outcomes beyond 1 year are not well described.This study evaluated 2-year outcomes in ViMAC, MViR, and MViV in the MITRAL trial.This multicenter prospective study enrolled patients with severe MAC, prior failed mitral annuloplasty ring repair, or prior failed bioprosthetic MV replacement who were at high surgical risk at 13 U.S. sites.Between February 1, 2015, and December 31, 2017, 91 patients were enrolled (31 with ViMAC, 30 with MViR, and 30 with MViV). In the ViMAC group, 2-year all-cause mortality was 39.3%, 66.7% were New York Heart Association (NYHA) functional class I-II, and mean MV gradient was 5.6 ± 2.0 mm Hg. In the MViR group, 2-year all-cause mortality was 50%, 65% were NYHA functional class I-II, and mean MV gradient was 6.5 ± 2.7 mm Hg. In the MViV group, 2-year all-cause mortality was 6.7%, 85% were NYHA functional class I-II, and mean MV gradient was 6.9 ± 2.4 mm Hg. At 2 years, all patients had ≤mild mitral regurgitation and survivors in all 3 arms showed sustained improvement in Kansas City Cardiomyopathy Questionnaire scores compared to baseline.Use of balloon-expandable aortic transcatheter heart valves in selected patients with severe MAC, failed annuloplasty ring, and bioprosthetic MV dysfunction is associated with improvements in symptoms, quality of life, and stable prosthesis function at 2-year follow-up. Between 1 and 2 years, the MViR group experienced higher mortality rates than the MViV and ViMAC groups.

Implantation of a transcatheter valve-in-mitral annular calcification (ViMAC) has emerged as an alternative to traditional surgical mitral valve (MV) replacement. Previous studies evaluating ViMAC aggregated transseptal, transapical, and transatrial forms of the procedure, leaving uncertainty about each technique's advantages and disadvantages. Thus, we sought to evaluate clinical outcomes specifically for transatrial ViMAC from the largest multicenter registry to-date.Patients with symptomatic MV dysfunction and severe MAC who underwent ViMAC were enrolled from 12 centers across the United States and Europe. Clinical characteristics, procedural details, and clinical outcomes were abstracted from the electronic record. The primary end point was all-cause mortality.We analyzed 126 patients who underwent ViMAC (median age 76 years [interquartile range {IQR}, 70-82 years], 28.6% female, median Society of Thoracic Surgeons score 6.8% [IQR, 4.0-11.4], and median follow-up 89 days [IQR, 16-383.5]). Sixty-one (48.4%) had isolated mitral stenosis, 25 (19.8%) had isolated mitral regurgitation (MR), and 40 (31.7%) had mixed MV disease. Technical success was achieved in 119 (94.4%) patients. Thirty (23.8%) patients underwent concurrent septal myectomy, and 8 (6.3%) patients experienced left ventricular outflow tract obstruction (7/8 did not undergo myectomy). Five (4.2%) patients of 118 with postprocedure echocardiograms had greater than mild paravalvular leak. Thirty-day and 1-year all-cause mortality occurred in 16 and 33 patients, respectively. In multivariable models, moderate or greater MR at baseline was associated with increased risk of 1-year mortality (hazard ratio, 2.31; 95% confidence interval, 1.07-4.99, P = .03).Transatrial ViMAC is safe and feasible in this selected, male-predominant cohort. Patients with significant MR may derive less benefit from ViMAC than patients with mitral stenosis only.

The SNAT2 (SLC38A2) System A amino acid transporter mediates Na+-coupled cellular uptake of small neutral α-amino acids (AAs) and is extensively regulated in response to humoral and nutritional cues. Understanding the basis of such regulation is important given that AA uptake via SNAT2 has been linked to activation of mTORC1; a major controller of many important cellular processes including, for example, mRNA translation, lipid synthesis, and autophagy and whose dysregulation has been implicated in the development of cancer and conditions such as obesity and type 2 diabetes. Extracellular AA withdrawal induces an adaptive upregulation of SNAT2 gene transcription and SNAT2 protein stability but, as yet, the sensing mechanism(s) that initiate this response remain poorly understood although interactions between SNAT2 and its substrates may play a vital role. Herein, we have explored how changes in substrate (AA and Na+) availability impact upon the adaptive regulation of SNAT2 in HeLa cells. We show that while AA deprivation induces SNAT2 gene expression, this induction was not apparent if extracellular Na+ was removed during the AA withdrawal period. Furthermore, we show that the increase in SNAT2 protein stability associated with AA withdrawal is selectively repressed by provision of SNAT2 AA substrates (N-methylaminoisobutyric acid and glutamine), but not non-substrates. This stabilization and substrate-induced repression were critically dependent upon the cytoplasmic N-terminal tail of SNAT2 (containing lysyl residues which are putative targets of the ubiquitin-proteasome system), because “grafting” this tail onto SNAT5, a related SLC38 family member that does not exhibit adaptive regulation, confers substrate-induced changes in stability of the SNAT2-5 chimeric transporter. In contrast, expression of SNAT2 in which the N-terminal lysyl residues were mutated to alanine rendered the transporter stable and insensitive to substrate-induced changes in protein stability. Intriguingly, SNAT2 protein stability was dramatically reduced in the absence of extracellular Na+ irrespective of whether substrate AAs were present or absent. Our findings indicate that the presence of extracellular Na+ (and potentially its binding to SNAT2) may be crucial for not only sensing SNAT2 AA occupancy and consequently for initiating the adaptive response under AA insufficient conditions, but for enabling substrate-induced changes in SNAT2 protein stability.

ObjectiveIschemia-reperfusion injury remains a major cause of mortality and morbidity in clinical lung transplantation. Interaction of activated leukocytes with injured graft endothelial cells participates in the development of ischemia-reperfusion injury. We sought to determine if modification of the reperfusate (with depletion of leukocytes and alteration of its composition) would decrease the incidence of ischemia-reperfusion injury in human lung transplantation when compared with whole blood reperfusion in a historical group of patients.MethodsBetween June 1999 and July 2001, 23 adult patients undergoing lung transplantation consented to modified reperfusion. After implantation, a catheter was inserted into the main or individual pulmonary arteries, and modified reperfusate was administered at a pressure less than 20 mm Hg. The modified reperfusate was depleted of leukocytes, supplemented with nitroglycerin, adjusted for pH and calcium level, and enriched with aspartate, glutamate, and dextrose. After 10 minutes of modified reperfusion, the removal of pulmonary artery clamp or weaning of cardiopulmonary bypass was performed per usual protocol. Age- and diagnosis-matched historical patients served as the control group. Ischemia-reperfusion injury was defined as Pao2/Fio2 < 150 with diffuse infiltrate on the radiograph in absence of other causes.ResultsThere was no difference in donor age or oxygenation indices, recipient age, the number of patients requiring cardiopulmonary bypass, ischemia time, and recipient oxygenation indices between the modified reperfusate group and the control group. However, none of the patients in the modified reperfusate group developed ischemia-reperfusion injury in contrast to 5 patients in the control group (P < .05). The early survival in the modified reperfusate group was 96% versus 81% in the control group (P = NS).ConclusionThis study suggests that modification of the reperfusate content decreases the incidence of ischemia-reperfusion injury in human lung transplantation when compared with whole blood reperfusion in a historical group of patients. Modified reperfusate may allow acceptance of marginal lungs and expansion of the donor pool.