Right atrial pressure torsades de pointes.

A 39-year-old man with non-ischemic cardiomyopathy presented for routine right heart catheterization.

A humanized knockin mouse model of Duchenne muscular dystrophy and its correction by CRISPR-Cas9 therapeutic gene editing.

Duchenne muscular dystrophy (DMD) is a lethal neuromuscular disease caused by mutations in the X-linked dystrophin (DMD) gene. Exon deletions flanking exon 51, which disrupt the dystrophin open reading frame (ORF), represent one of the most common types of human DMD mutations. Previously, we used clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) gene editing to restore the reading frame of exon 51 in mice and dogs with exon 50 deletions. Due to genomic sequence variations between species, the single guide RNAs (sgRNAs) used for DMD gene editing are often not conserved, impeding direct clinical translation of CRISPR-Cas therapeutic gene-editing strategies. To circumvent this potential obstacle, we generated a humanized DMD mouse model by replacing mouse exon 51 with human exon 51, followed by deletion of mouse exon 50, which disrupted the dystrophin ORF. Systemic CRISPR-Cas9 gene editing using an sgRNA that targets human exon 51 efficiently restored dystrophin expression and ameliorated pathologic hallmarks of DMD, including histopathology and grip strength in this mouse model. This unique DMD mouse model with the human genomic sequence allows in vivo assessment of clinically relevant gene editing strategies as well as other therapeutic approaches and represents a significant step toward therapeutic translation of CRISPR-Cas9 gene editing for correction of DMD.

Biomarkers in Duchenne Muscular Dystrophy.

PURPOSE OF REVIEW: This review highlights the key studies investigating various types of biomarkers in Duchenne muscular dystrophy (DMD). RECENT FINDINGS: Several proteomic and metabolomic studies have been undertaken in both human DMD patients and animal models of DMD that have identified potential biomarkers in DMD. Although there have been a number of proteomic and metabolomic studies that have identified various potential biomarkers in DMD, more definitive studies still need to be undertaken in DMD patients to firmly correlate these biomarkers with diagnosis, disease progression, and monitoring the effects of novel treatment strategies being developed.

Long-term maintenance of dystrophin expression and resistance to injury of skeletal muscle in gene edited DMD mice.

Duchenne muscular dystrophy (DMD) is a lethal muscle disease caused by mutations in the dystrophin gene. CRISPR/Cas9 genome editing has been used to correct DMD mutations in animal models at young ages. However, the longevity and durability of CRISPR/Cas9 editing remained to be determined. To address these issues, we subjected ΔEx44 DMD mice to systemic delivery of AAV9-expressing CRISPR/Cas9 gene editing components to reframe exon 45 of the dystrophin gene, allowing robust dystrophin expression and maintenance of muscle structure and function. We found that genome correction by CRISPR/Cas9 confers lifelong expression of dystrophin in mice and that corrected skeletal muscle is highly durable and resistant to myofiber necrosis and fibrosis, even in response to chronic injury. In contrast, when muscle fibers were ablated by barium chloride injection, we observed a loss of gene edited dystrophin expression. Analysis of on- and off-target editing in aged mice confirmed the stability of gene correction and the lack of significant off-target editing at 18 months of age. These findings demonstrate the long-term durability of CRISPR/Cas9 genome editing as a therapy for maintaining the integrity and function of DMD muscle, even under conditions of stress.

Development of a standard of care for patients with valosin-containing protein associated multisystem proteinopathy.

Valosin-containing protein (VCP) associated multisystem proteinopathy (MSP) is a rare inherited disorder that may result in multisystem involvement of varying phenotypes including inclusion body myopathy, Paget's disease of bone (PDB), frontotemporal dementia (FTD), parkinsonism, and amyotrophic lateral sclerosis (ALS), among others. An international multidisciplinary consortium of 40+ experts in neuromuscular disease, dementia, movement disorders, psychology, cardiology, pulmonology, physical therapy, occupational therapy, speech and language pathology, nutrition, genetics, integrative medicine, and endocrinology were convened by the patient advocacy organization, Cure VCP Disease, in December 2020 to develop a standard of care for this heterogeneous and under-diagnosed disease. To achieve this goal, working groups collaborated to generate expert consensus recommendations in 10 key areas: genetic diagnosis, myopathy, FTD, PDB, ALS, Charcot Marie Tooth disease (CMT), parkinsonism, cardiomyopathy, pulmonology, supportive therapies, nutrition and supplements, and mental health. In April 2021, facilitated discussion of each working group's conclusions with consensus building techniques enabled final agreement on the proposed standard of care for VCP patients. Timely referral to a specialty neuromuscular center is recommended to aid in efficient diagnosis of VCP MSP via single-gene testing in the case of a known familial VCP variant, or multi-gene panel sequencing in undifferentiated cases. Additionally, regular and ongoing multidisciplinary team follow up is essential for proactive screening and management of secondary complications. The goal of our consortium is to raise awareness of VCP MSP, expedite the time to accurate diagnosis, define gaps and inequities in patient care, initiate appropriate pharmacotherapies and supportive therapies for optimal management, and elevate the recommended best practices guidelines for multidisciplinary care internationally.

A consolidated AAV system for single-cut CRISPR correction of a common Duchenne muscular dystrophy mutation.

Duchenne muscular dystrophy (DMD), caused by mutations in the X-linked dystrophin gene, is a lethal neuromuscular disease. Correction of DMD mutations in animal models has been achieved by CRISPR/Cas9 genome editing using Streptococcus pyogenes Cas9 (SpCas9) delivered by adeno-associated virus (AAV). However, due to the limited viral packaging capacity of AAV, two AAV vectors are required to deliver the SpCas9 nuclease and its single guide RNA (sgRNA), impeding its therapeutic application. We devised an efficient single-cut gene-editing method using a compact Staphylococcus aureus Cas9 (SaCas9) to restore the open reading frame of exon 51, the most commonly affected out-of-frame exon in DMD. Editing of exon 51 in cardiomyocytes derived from human induced pluripotent stem cells revealed a strong preference for exon reframing via a two-nucleotide deletion. We adapted this system to express SaCas9 and sgRNA from a single AAV9 vector. Systemic delivery of this All-In-One AAV9 system restored dystrophin expression and improved muscle contractility in a mouse model of DMD with exon 50 deletion. These findings demonstrate the effectiveness of CRISPR/SaCas9 delivered by a consolidated AAV delivery system in the correction of DMD in vivo, representing a promising therapeutic approach to correct the genetic causes of DMD.

Identifying Discordance of Right- and Left-Ventricular Filling Pressures in Patients With Heart Failure by the Clinical Examination.

BACKGROUND: In ≈25% of patients with heart failure and reduced left-ventricular ejection fraction, right-ventricular (RV), and left-ventricular (LV) filling pressures are discordant (ie, one is elevated while the other is not). Whether clinical assessment allows detection of this discordance is unknown. We sought to determine the agreement of clinically versus invasively determined patterns of ventricular congestion. METHODS: In 156 heart failure and reduced LV ejection fraction subjects undergoing invasive hemodynamic assessment, we categorized patterns of ventricular congestion (no congestion, RV only, LV only, or both) based on clinical findings of RV (jugular venous distention) or LV (hepatojugular reflux, orthopnea, or bendopnea) congestion. Agreement between clinically and invasively determined (RV congestion if right atrial pressure [RAP] ≥10 mm Hg and LV congestion if pulmonary capillary wedge pressure [PCWP] ≥22 mm Hg) categorizations was the primary end point. RESULTS: The frequency of clinical patterns of congestion was: 51% no congestion, 24% both RV and LV, 21% LV only, and 4% RV only. Jugular venous distention had excellent discrimination for elevated RAP (C=0.88). However, agreement between clinical and invasive congestion patterns was poor, к=0.44 (95% CI, 0.34-0.55). While those with no clinical congestion usually had low RAP and PCWP (67/79, 85%), over one-half (24/38, 64%) with isolated LV clinical congestion had PCWP <22 mm Hg, most (5/7, 71%) with isolated RV clinical congestion had PCWP ≥22 mm Hg, and ≈one-third (10/32, 31%) with both RV and LV clinical congestion had elevated RAP but PCWP <22 mm Hg. CONCLUSIONS: While clinical examination allows accurate detection of elevated RAP, it does not allow accurate detection of discordant RV and LV filling pressures.

Ascites and Edema After Bicaval Orthotopic Heart Transplant.

IVC stenosis is a rare complication of bicaval orthotopic heart transplant. IVC stenosis can occur at either the cavo-atrial anastomosis, or the caval cannulation site, with presentations ranging from acute shock early post transplant to a more indolent course. Causes include extensive hemostatic suturing, fibrous contraction, and donor-recipient size mismatch. Treatment strategies include percutaneous balloon angioplasty, stenting, and surgical revision. Evaluating for IVC stenosis is recommended for unexplained lower-extremity edema, new-onset ascites, or liver abnormalities after bicaval heart transplant.

A novel phonetic approach to continuous flow left ventricular assist device auscultation.

BACKGROUND: The dominant sound generated by continuous flow left ventricular assist devices (cf-LVADs) has generically been referred to as a "hum". This term, however, implies that despite distinct engineering designs, all cf-LVADs generate the same quality of sound. Furthermore, no structured method for auscultation of cf-LVADs exists. We hereby report a novel and simple phonetic approach to device auscultation, the aims of which are to improve recognition, understanding, and teaching of sound produced by normally functioning cf-LVADs. We sought to evaluate whether clinically relevant pump or person related events can produce changes in the expected audio fingerprint of a particular cf-LVAD, and whether these changes in sound can be identified by auscultation and translated phonetically. METHODS: Sound recordings were made on 7 people implanted with one of 3 U.S. Food and Drug Administration (FDA) approved cf-LVADs. Of the 7, 3 were considered to have normal device function and stable condition. The remaining 4 people had a clinically relevant pump or person related event. Recordings were made with a stethoscope attachment that allows digital recording of sound and provides a real time phonocardiogram. RESULTS: The main findings were the following: 1.) each cf-LVAD generates a unique audio fingerprint 2.) the audio fingerprint can be phonetically translated in a simple manner. 3.) pump or patient related events result in changes in device sound, that can be appreciated phonetically. CONCLUSIONS: Phonetics offer a novel and easily reproducible method for evaluation and teaching normal cf-LVAD sounds by auscultation. Additionally, clinically relevant pump or person related events can produce changes in the expected audio fingerprint of a particular cf-LVAD. These changes in sound can be identified by auscultation and translated phonetically. Auscultation is an important component of the physical examination of people supported with cf-LVADs.

The nuclear envelope protein Net39 is essential for muscle nuclear integrity and chromatin organization.

Lamins and transmembrane proteins within the nuclear envelope regulate nuclear structure and chromatin organization. Nuclear envelope transmembrane protein 39 (Net39) is a muscle nuclear envelope protein whose functions in vivo have not been explored. We show that mice lacking Net39 succumb to severe myopathy and juvenile lethality, with concomitant disruption in nuclear integrity, chromatin accessibility, gene expression, and metabolism. These abnormalities resemble those of Emery-Dreifuss muscular dystrophy (EDMD), caused by mutations in A-type lamins (LMNA) and other genes, like Emerin (EMD). We observe that Net39 is downregulated in EDMD patients, implicating Net39 in the pathogenesis of this disorder. Our findings highlight the role of Net39 at the nuclear envelope in maintaining muscle chromatin organization, gene expression and function, and its potential contribution to the molecular etiology of EDMD.

Heterozygous Cystic Fibrosis Transmembrane Regulator Gene Missense Variants Are Associated With Worse Cardiac Function in Patients With Duchenne Muscular Dystrophy.

Background Duchenne muscular dystrophy (DMD) is a neuromuscular disorder caused by mutations within the dystrophin gene. DMD is characterized by progressive skeletal muscle degeneration and atrophy and progressive cardiomyopathy. It has been observed the severity of cardiomyopathy varies in patients with DMD. Methods and Results A cohort of male patients with DMD and female DMD carriers underwent whole exome sequencing. Potential risk factor variants were identified according to their functional annotations and frequencies. Cardiac function of 15 male patients with DMD was assessed by cardiac magnetic resonance imaging, and various cardiac magnetic resonance imaging parameters and circulating biomarkers were compared between genotype groups. Five subjects carrying potential risk factor variants in the cystic fibrosis transmembrane regulator gene demonstrated lower left ventricular ejection fraction, larger left ventricular end-diastolic volume, and higher NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels compared with 10 subjects who did not carry the potential risk factor variants (P=0.023, 0.019 and 0.028, respectively). Conclusions This study revealed heterozygous cystic fibrosis transmembrane regulator gene missense variants were associated with worse cardiac function in patients with DMD. The cystic fibrosis transmembrane regulator gene may serve as a genetic modifier that accounts for more severe cardiomyopathy in patients with DMD, who would require more aggressive management of the cardiomyopathy.

Saved by the VAC: Minimally Invasive Removal of a Surely Fatal Right Heart Thrombus in a Patient with Advanced Heart Failure.

Intracardiac thrombi are associated with an increased morbidity and mortality due to their unpredictability and embolic potential. Right heart thrombus is infrequently encountered in clinical practice outside the scenario of acute pulmonary embolism with hemodynamic compromise, and even more uncommon is the presence of a massive right heart thrombus. Embolic potential is high, and historically, management has revolved around open surgical removal or systemic thrombolysis. We hereby present a case of a massive right heart thrombus in a high surgical risk patient, which was successfully removed using a percutaneous aspiration device.

Enhanced CRISPR-Cas9 correction of Duchenne muscular dystrophy in mice by a self-complementary AAV delivery system.

Duchenne muscular dystrophy (DMD) is a lethal neuromuscular disease caused by mutations in the dystrophin gene (DMD). Previously, we applied CRISPR-Cas9-mediated "single-cut" genome editing to correct diverse genetic mutations in animal models of DMD. However, high doses of adeno-associated virus (AAV) are required for efficient in vivo genome editing, posing challenges for clinical application. In this study, we packaged Cas9 nuclease in single-stranded AAV (ssAAV) and CRISPR single guide RNAs in self-complementary AAV (scAAV) and delivered this dual AAV system into a mouse model of DMD. The dose of scAAV required for efficient genome editing were at least 20-fold lower than with ssAAV. Mice receiving systemic treatment showed restoration of dystrophin expression and improved muscle contractility. These findings show that the efficiency of CRISPR-Cas9-mediated genome editing can be substantially improved by using the scAAV system. This represents an important advancement toward therapeutic translation of genome editing for DMD.

Clinical Care Recommendations for Cardiologists Treating Adults With Myotonic Dystrophy.

Myotonic dystrophy is an inherited systemic disorder affecting skeletal muscle and the heart. Genetic testing for myotonic dystrophy is diagnostic and identifies those at risk for cardiac complications. The 2 major genetic forms of myotonic dystrophy, type 1 and type 2, differ in genetic etiology yet share clinical features. The cardiac management of myotonic dystrophy should include surveillance for arrhythmias and left ventricular dysfunction, both of which occur in progressive manner and contribute to morbidity and mortality. To promote the development of care guidelines for myotonic dystrophy, the Myotonic Foundation solicited the input of care experts and organized the drafting of these recommendations. As a rare disorder, large scale clinical trial data to guide the management of myotonic dystrophy are largely lacking. The following recommendations represent expert consensus opinion from those with experience in the management of myotonic dystrophy, in part supported by literature-based evidence where available.

Impact of induction immunosuppression on patient survival in heart transplant recipients treated with tacrolimus and mycophenolic acid in the current allocation era.

BACKGROUND: The practice of induction therapy with either rabbit anti-thymocyte globulin (r-ATG) or interleukin-2 receptor antagonists (IL-2RA) is common among heart transplant recipients. However, its benefits in the setting of contemporary maintenance immunosuppression with tacrolimus/mycophenolic acid (TAC/MPA) are unknown. METHODS: We compared post-transplant mortality among three induction therapy strategies (r-ATG vs IL2-RA vs no induction) in a retrospective cohort analysis of heart transplant recipients maintained on TAC/MPA in the Organ Procurement Transplant Network (OPTN) database between the years 2006 and 2015. We used a multivariable model adjusting for clinically important co-morbidities, and a propensity score analysis using the inverse probability weighted (IPW) method in the final analysis. RESULTS: In multivariable IPW analysis, r-ATG (HR = 1.23; 95% CI = 1.05-1.46, P = 0.01) remained significantly associated with a higher mortality. There was a trend toward having a higher mortality in the IL2-RA (HR = 1.11; 95% CI = 1.00-1.24, P = 0.06) group. Subgroup analyses failed to show a patient survival benefit in using either r-ATG or IL2-RA among any of the subgroups analyzed. CONCLUSION: In this contemporary cohort of heart transplant recipients receiving TAC/MPA, neither r-ATG nor IL2-RA were associated with a survival benefit. On the contrary, adjusted analyses showed a significantly higher mortality in the r-ATG group and a trend toward higher mortality in the IL2-RA group. While caution is needed in interpreting treatment effects in an observational cohort, these data call into question the benefit of induction therapy as a common practice and highlight the need for more studies.