Mitral valve surgery in patients with Marfan syndrome.

OBJECTIVE: To review the pathology of the mitral valve (MV) and long-term outcomes of surgery in patients with Marfan syndrome (MFS). PATIENTS AND METHODS: From 1988 through 2020, 60 patients with MFS had surgery to correct mitral regurgitation (MR): 19 had isolated MV surgery, 32 had combined MV and aortic root surgery, and 9 had MV surgery after aortic root surgery. Follow-up was complete for a median of 16.1 years. RESULTS: MV pathology was myxomatous degeneration in all patients and of advanced degree in 78.6% with bileaflet prolapse in 65.5%, mitral annulus disjunction in 57.5%, and mitral annulus calcification in 8.2% of patients. The MV was repaired in 47 patients and replaced in 13. Kaplan-Meier estimates of cumulative mortality at 20 years 21.3% for all patients, 6.7% after MV repair, and 57.8% after replacement (P < .001). MV reoperations were performed in 5 patients: 2 after repair and 3 after replacement. The cumulative incidence rate of reoperations on the MV was 3.8% at 10 years and 11.0% at 20 years in the entire cohort. Among 47 patients who had MV repair, moderate MR developed in 11 patients and severe in 2. Both patients with severe MR underwent MV reoperation. The cumulative incidence rate of recurrent moderate or severe MR after MV repair was 20.4% at 10 years, and 36.5% at 20 years. CONCLUSIONS: MV repair was associated with better survival than MV replacement, but recurrent MR after repair occurred in approximately one-third of the patients at 20 years after surgery.

Reimplantation of the aortic valve in patients with tricuspid aortic valve: the Toronto General Hospital experience.

Background: Aortic valve sparing operations were introduced three decades ago but controversy remains regarding its appropriateness, reproducibility and durability. This article describes the long-term outcomes of patients who had reimplantation of the aortic valve. Methods: All patients who had reimplantation of a tricuspid aortic valve at Toronto General Hospital from 1989 through 2019 were selected for this study. Patients were followed prospectively with periodical clinical assessments and imaging of the heart and aorta. Results: Four hundred and four patients were identified. The median age was 48.0 [interquartile range (IQR), 35.0-59.0] years and 310 (76.7%) were men. There were 150 patients with Marfan syndrome, 20 with Loeys-Dietz syndrome and 33 with acute or chronic aortic dissections. The median follow-up was 11.7 (IQR, 6.8-17.1) years. There were 55 patients alive and without reoperation at 20 years. The cumulative mortality at 20 years was 26.7% [95% confidence interval (CI): 20.6-34.2%], the cumulative incidence of reoperation on the aortic valve was 7.0% (95% CI: 4.0-12.2%) and the development of moderate or severe aortic insufficiency was 11.8% (95% CI: 8.5-16.5%). We could not identify variables associated with reoperation on the aortic valve or with the development of aortic insufficiency. New distal aortic dissections were common in patients with associated genetic syndromes. Conclusions: Reimplantation of the aortic valve in patients with tricuspid aortic valve provides excellent aortic valve function during the first two decades of follow-up. Distal aortic dissections are relatively common in patients with associated genetic syndromes.

Human cortical interneurons optimized for grafting specifically integrate, abort seizures, and display prolonged efficacy without over-inhibition.

Previously, we demonstrated the efficacy of human pluripotent stem cell (hPSC)-derived GABAergic cortical interneuron (cIN) grafts in ameliorating seizures. However, a safe and reliable clinical translation requires a mechanistic understanding of graft function, as well as the assurance of long-term efficacy and safety. By employing hPSC-derived chemically matured migratory cINs in two models of epilepsy, we demonstrate lasting efficacy in treating seizures and comorbid deficits, as well as safety without uncontrolled growth. Host inhibition does not increase with increasing grafted cIN densities, assuring their safety without the risk of over-inhibition. Furthermore, their closed-loop optogenetic activation aborted seizure activity, revealing mechanisms of graft-mediated seizure control and allowing graft modulation for optimal translation. Monosynaptic tracing shows their extensive and specific synaptic connections with host neurons, resembling developmental connection specificity. These results offer confidence in stem cell-based therapy for epilepsy as a safe and reliable treatment for patients suffering from intractable epilepsy.

Large-Scale Generation and Characterization of Homogeneous Populations of Migratory Cortical Interneurons from Human Pluripotent Stem Cells.

During development, cortical interneurons (cINs) are generated from the ventral telencephalon, robustly migrate to the dorsal telencephalon, make local synaptic connections, and critically regulate brain circuitry by inhibiting other neurons. Thus, their abnormality is associated with various brain disorders. Human pluripotent stem cell (hPSC)-derived cINs can provide unlimited sources with which to study the pathogenesis mechanism of these disorders as well as provide a platform to develop novel therapeutics. By employing spinner culture, we could obtain a >10-fold higher yield of cIN progenitors compared to conventional culture without affecting their phenotype. Generated cIN spheres can be maintained feeder-free up to 10 months and are optimized for passaging and cryopreservation. In addition, we identified a combination of chemicals that synchronously matures generated progenitors into SOX6+KI67- migratory cINs and extensively characterized their maturation in terms of metabolism, migration, arborization, and electrophysiology. When transplanted into mouse brains, chemically matured migratory cINs generated grafts that efficiently disperse and integrate into the host circuitry without uncontrolled growth, making them an optimal cell population for cell therapy. Efficient large-scale generation of homogeneous migratory cINs without the need of feeder cells will play a critical role in the full realization of hPSC-derived cINs for development of novel therapeutics.

Assessment of a mitral valve replacement skills trainer: a simplified, low-cost approach.

OBJECTIVES: Simulated mitral valve replacement may aid in the assessment of technical skills required for adequate performance in the operating room. We sought to design and assess a mitral valve replacement training station that is low-cost, nonperishable, portable, and reproducible as a first step in developing a mitral valve surgical skills curriculum. METHODS: Nineteen physicians (7 general surgery residents, 8 cardiothoracic surgery residents, and 4 attending cardiothoracic surgeons) underwent simulated mitral valve replacement testing. Simulated mitral valve replacement was performed on a training station consisting of a replaceable "mitral annulus" inside a restrictive "left atrium." Eight components of performance were graded on a 5-point scale. A composite score (100 point maximum) was calculated by weighting the grades by procedural time. The effect of training level was evaluated using analysis of variance and post hoc Tukey honestly significant difference. RESULTS: The speed of simulated mitral valve replacement varied among general surgery residents, cardiothoracic surgery residents, and attending cardiothoracic surgeons (52.9 ± 9.0 vs 32.8 ± 4.7 vs 28.0 ± 3.5 minutes, respectively; F = 25.3; P < .001). Level of training significantly affected all 8 evaluation components (P < .001). Composite scores increased with level of training (general surgery residents 32.9 ± 11.4, cardiothoracic surgery residents 65.1 ± 11.5, and attending cardiothoracic surgeons 88.3 ± 7.8 of a possible 100 points; F = 35.7; P < .001). Cardiothoracic surgery residents who reported having performed 10 to 50 mitral valve replacements as the primary surgeon had a composite score of 65.0 ± 2.8 (P < .01 compared with attending cardiothoracic surgeons). CONCLUSIONS: Simulated mitral valve replacement can be performed using this simple, affordable, portable setup. Performance scores correlate with level of training and experience, but residents who performed 10 to 50 mitral valve replacements still failed to reach attending-level proficiency. This training simulator may facilitate skills practice and evaluation of competency in cardiac surgery trainees.