A Multi-Omics Atlas of Sex-Specific Differences in Obstructive Hypertrophic Cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is a common genetic heart disease. Women with HCM tend to have a later onset but more severe disease course. However, the underlying pathobiological mechanisms for these differences remain unknown.

Methods

Myectomy samples from 97 patients (53 males/44 females) with symptomatic obstructive HCM and 23 control cardiac tissues were included in this study. RNA-sequencing was performed on all samples. Mass spectrometry-based proteomics and phosphoproteomics was performed on a representative subset of samples.

Results

The transcriptome, proteome, and phosphoproteome was similar between sexes and did not separate on PCA plotting. Overall, there were 482 differentially expressed genes (DEGs) between control females and control males while there were only 53 DEGs between HCM females and HCM males. There were 1963 DEGs between HCM females and control females compared to 1064 DEGs between HCM males and control males. Additionally, there was increased transcriptional downregulation of hypertrophy pathways in HCM females and in HCM males. HCM females had 119 differentially expressed proteins compared to control females while HCM males only had 27 compared to control males. Finally, the phosphoproteome showed females had 341 differentially phosphorylated proteins (DPPs) compared to controls while males only had 184. Interestingly, there was hypophosphorylation and inactivation of hypertrophy pathways in females but hyperphosphorylation and activation in males.

Conclusion

There are subtle, but biologically relevant differences in the multi-omics profile of HCM. This study provides the most comprehensive atlas of sex-specific differences in the transcriptome, proteome, and phosphoproteome present at the time of surgical myectomy for obstructive HCM.

Temporal Association Between Vaping and Risk of Cardiac Events

OBJECTIVE

To describe our early observations with sudden cardiac arrest (SCA) and sudden death (SD) in patients using vape products.

PATIENTS AND METHODS

A retrospective analysis of Mayo Clinic's Windland Smith Rice Genetic Heart Rhythm Clinic and Sudden Death Genomics Laboratory was performed on all SCA survivors and decedents who presented between January 1, 2007, and December 31, 2021, to identify patients/decedents with a history of vaping. Data abstraction included patient demographics, clinical characteristics, and documented use of vape products.

RESULTS

Among 144 SCA survivors and 360 SD victims, there were six individuals (1%; 3 females) with unexplained SCA (n=4) or SD (n=2) that was temporally associated with vaping use with a mean age at sentinel event of 23±5 years. The SCA survivors include a 19-year-old male who was resuscitated from documented ventricular fibrillation 40 minutes after vaping and a 19-year-old male who was resuscitated from ventricular fibrillation a few hours post vaping. The first SD victim was a 19-year-old female with exercise-induced asthma who died in her sleep after vaping that evening. Autopsy results showed eosinophilic infiltrates in the lung tissue and death was attributed to bronchial asthma. The second vaping-associated death involved a 26-year-old male whose autopsy attributed the death to acute respiratory distress syndrome.

CONCLUSION

We have identified six young individuals with a history of vaping who experienced a near fatal episode or a tragic SD. Although larger cohort studies are needed to quantify the actual risk of SD, it seems prudent to sound an early warning about vaping's potential lethality.

Cardiac fludeoxyglucose-18 positron emission tomography in genotype-positive arrhythmogenic cardiomyopathy

BACKGROUND

Myocardial inflammation contributes to the pathogenesis of arrhythmogenic cardiomyopathy (ACM), a clinically and genetically heterogenous disorder. Due to phenotypic overlap, some patients with genetic ACM may be evaluated for an underlying inflammatory cardiomyopathy. However, the cardiac fludeoxyglucose (FDG) positron emission tomography (PET) findings in ACM patients have not been elucidated.

METHODS

All genotype-positive patients in the Mayo Clinic ACM registry (n = 323) who received a cardiac FDG PET were included in this study. Pertinent data were extracted from the medical record.

RESULTS

Collectively, 12/323 (4%; 67% female) genotype-positive ACM patients received a cardiac PET FDG scan as part of their clinical evaluation (median age at scan 49 ± 13 years). Amongst these patients, pathogenic/likely pathogenic variants were detected in LMNA (n = 7), DSP (n = 3), FLNC (n = 1) and PLN (n = 1). Of note, 6/12 (50%) had abnormal myocardial FDG uptake, including diffuse (entire myocardium) uptake in 2/6 (33%), focal (1-2 segments) uptake in 2/6 (33%) and patchy (3+ segments) in 2/6 (33%). Median myocardial standardized uptake value ratio was 2.1. Interestingly, LMNA-positive patients accounted for 3 out of 6 (50%) positive studies (diffuse uptake in 2 and focal uptake in 1).

CONCLUSION

Abnormal myocardial FDG uptake is common in genetic ACM patients undergoing cardiac FDG PET. This study further supports the role of myocardial inflammation in ACM. Further investigation is needed to determine role of FDG PET in diagnosis and management of ACM and investigate the role of inflammation in ACM.

Proteomic and phosphoproteomic analyses of myectomy tissue reveals difference between sarcomeric and genotype-negative hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetically heterogenous condition with about half of cases remaining genetically elusive or non-genetic in origin. HCM patients with a positive genetic test (HCMSarc) present earlier and with more severe disease than those with a negative genetic test (HCMNeg). We hypothesized these differences may be due to and/or reflect proteomic and phosphoproteomic differences between the two groups. TMT-labeled mass spectrometry was performed on 15 HCMSarc, 8 HCMNeg, and 7 control samples. There were 243 proteins differentially expressed and 257 proteins differentially phosphorylated between HCMSarc and HCMNeg. About 90% of pathways altered between genotypes were in disease-related pathways and HCMSarc showed enhanced proteomic and phosphoproteomic alterations in these pathways. Thus, we show HCMSarc has enhanced proteomic and phosphoproteomic dysregulation observed which may contribute to the more severe disease phenotype.

Clinical course of patients with hypertrophic cardiomyopathy away from tertiary referral care

AIMS

Data on the clinical course of hypertrophic cardiomyopathy (HCM) are mainly derived from tertiary HCM centre studies, and knowledge of clinical outcomes of patients leaving specialty care and returning to local physicians is limited due to gaps between clinical encounters or complete loss of follow-up. This survey aims to describe the clinical course of HCM in patients following their evaluation at a tertiary referral centre.

METHODS AND RESULTS

A comprehensive outcomes survey was developed and sent to 4495 eligible patients with HCM previously evaluated at Mayo Clinic. Questions assessed general well-being, New York Heart Association class, procedures performed, and probable HCM-triggered ventricular arrhythmic events (VAEs) since last visit. In total, 2058 patients (mean age 63 ± 15 years; 42% female) responded to the survey covering a total of 10 510 patient-years with an average of 5.4 ± 6.4 years of follow-up since their last on-campus/virtual visit to Mayo Clinic. During their time away from specialty care, 20% of patients reported having cardiac-related hospitalizations and 25% reported having cardiac-related procedures. Similar to high-risk referral cohorts, 5% of patients reported VAEs with an event rate of 0.98 events/100 patient-years. The prevalence of atrial fibrillation, syncope, pre-syncope, cardiac-related hospitalizations, and VAEs during time away from specialty care increased significantly with increasing New York Heart Association class (P < 0.001).

CONCLUSIONS

Acknowledging ascertainment bias, the clinical course of patients away from tertiary care may be more severe than previously anticipated. Among those with exertional symptoms, HCM-related morbidity increased substantially. Higher risk HCM patients should remain in contact with HCM specialty care.

Multi-Omic Architecture of Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is characterized by asymmetric left ventricular hypertrophy. Currently, hypertrophy pathways responsible for HCM have not been fully elucidated. Their identification could serve as a nidus for the generation of novel therapeutics aimed at halting disease development or progression. Herein, we performed a comprehensive multi-omic characterization of hypertrophy pathways in HCM.

METHODS

Flash-frozen cardiac tissues were collected from genotyped HCM patients (n=97) undergoing surgical myectomy and tissue from 23 controls. RNA sequencing and mass spectrometry-enabled deep proteome and phosphoproteomic assessment were performed. Rigorous differential expression, gene set enrichment, and pathway analyses were performed to characterize HCM-mediated alterations with emphasis on hypertrophy pathways.

RESULTS

We identified transcriptional dysregulation with 1246 (8%) differentially expressed genes and elucidated downregulation of 10 hypertrophy pathways. Deep proteomic analysis identified 411 proteins (9%) that differed between HCM and controls with strong dysregulation of metabolic pathways. Seven hypertrophy pathways were upregulated with antagonistic upregulation of 5 of 10 hypertrophy pathways shown to be downregulated in the transcriptome. Most upregulated hypertrophy pathways encompassed the RAS-MAPK signaling cascade. Phosphoproteomic analysis demonstrated hyperphosphorylation of the RAS-MAPK system suggesting activation of this signaling cascade. There was a common transcriptomic and proteomic profile regardless of genotype.

CONCLUSIONS

At time of surgical myectomy, the ventricular proteome, independent of genotype, reveals widespread upregulation and activation of hypertrophy pathways, mainly involving the RAS-MAPK signaling cascade. In addition, there is a counterregulatory transcriptional downregulation of the same pathways. RAS-MAPK activation may serve a crucial role in hypertrophy observed in HCM.

Cardiopulmonary Exercise Testing in Athletes With Hypertrophic Cardiomyopathy

Patients with hypertrophic cardiomyopathy (HCM) have historically been restricted from athletic participation because of the perceived risk of sudden cardiac death. More contemporary research has highlighted the relative safety of competitive athletics with HCM. However, lack of published data on reference values for cardiopulmonary exercise testing (CPET) complicates clinical management and counseling on sports participation in the individual athlete. We conducted a single-center, retrospective cohort study to investigate CPET in athletes with HCM and clinical characteristics associated with objective measures of aerobic capacity. We identified 58 athletes with HCM (74% male, mean age 18 ± 3 years, mean left ventricular (LV) wall thickness 20 ± 7 mm). LV outflow tract obstruction was present in 22 (38%). A total of 15 (26%) athletes were taking a β blocker (BB), but only 4 (7%) reported exertional symptoms. Overall, exercise capacity was mildly reduced, with a peak myocardial oxygen consumption (peak VO₂) of 37.9 ml/min/kg (83% of predicted peak VO₂). Both LV outflow tract obstruction and BB use were associated with reduced exercise capacity. Limited peak heart rate was more common in athletes taking BB (47% vs 9%, p = 0.002). At a mean 5.6 years follow-up, 5 patients underwent myectomy (9%), and 8 (14%) received an implantable cardioverter defibrillator (ICD) for primary prevention. One individual with massive LV hypertrophy experienced recurrent ICD shocks for ventricular fibrillation and underwent myectomy 7 years after initial evaluation and was no longer participating in sports. There were no deaths over the follow-up period. In conclusion, the prognostic role of CPET remains unclear in athletes with HCM. Mildly reduced exercise capacity was common; however, reduced peak VO₂ did not correlate with symptom status or clinical outcomes. A significant proportion went on to require myectomy and/or ICD, thus highlighting the need for close follow-up. These data provide some initial insight into the clinical evaluation of "real world" athletes with HCM; however, further study is warranted to help guide shared decision-making, return-to-play discussions, and the potential long-term safety of competitive athletic participation.

Red herring pathogenic variants: a case report of premature ventricular contraction-triggered ventricular fibrillation with an incidental pathogenic LMNA variant

Background

Pathogenic variants in the lamin A/C gene (LMNA) can lead to a wide range of phenotypes from dilated and arrhythmogenic cardiomyopathies and conduction abnormalities to partial lipodystrophies. This case highlights a coincidental pathogenic LMNA variant identified in a patient with sudden cardiac arrest (SCA). We demonstrate the need for careful interpretation of pathogenic variants identified in cardiomyopathy genes by highlighting a case in which a coincidental pathogenic LMNA variant was found in a patient with premature ventricular complex (PVC)-induced ventricular fibrillation (VF).

Case summary

We present the case of a 16-year-old male with SCA secondary to VF. Genetic testing identified a maternally inherited pathogenic variant in LMNA annotated c.1961dup; p.T655Nfs*49. The patient received an implantable cardiac defibrillator and was discharged on nadolol. The patient's two brothers were also variant-positive. However, the patient and both brothers had normal chamber dimensions on echocardiogram and no late gadolinium enhancement on cardiac magnetic resonance imaging. The family members with the variant were recommended to have prophylactic implantable cardiac defibrillators and thus sought a second opinion. The patient received an appropriate shock and device interrogation identified PVCs. Electrophysiology study identified PVC-induced VF which was ablated with no recurrent ventricular arrhythmias/implantable cardioverter defibrillator therapies over 8 months of follow-up. Although the variant in LMNA could lead to cardiac arrest, the clinical phenotype was consistent with a non-genetic aetiology. The family members were told to have periodic cardiac evaluation.

Discussion

This case demonstrates the identification of a coincidental pathogenic variant in a cardiomyopathy gene in a patient with cardiac arrest. Although this variant could lead to cardiomyopathy, it appears the cardiac arrest was not due to the pathogenic variant. This highlights the need to consider the clinical phenotype when interpreting genetic test results for cardiomyopathies even in the presence of a positive genetic test result.

Return-to-Play for Athletes With Long QT Syndrome or Genetic Heart Diseases Predisposing to Sudden Death

BACKGROUND

Within the last 5 years, cardiac society guidelines have begun to acknowledge shared decision making (SDM) for the athlete with sudden cardiac death-predisposing genetic heart diseases (GHDs), such as long QT syndrome (LQTS), and the possibility for that athlete's return to play. Previously, international guidelines embraced a de facto disqualification for all such athletes including athletes with solely a positive genetic test in Europe.

OBJECTIVES

This study sought to examine the prevalence and outcomes of athletes with sudden cardiac death-predisposing GHDs, particularly LQTS, after their return to play.

METHODS

A retrospective review of the electronic medical record was performed on all athletes with GHD, with a primary analysis for those with LQTS, who were evaluated, risk stratified, and treated in Mayo Clinic's Windland Smith Rice Genetic Heart Rhythm Clinic by a single genetic cardiologist between July 1, 2000, and July 31, 2020.

RESULTS

There were 672 athletes with GHD overall including 494 athletes with LQTS (231 female athletes [46.8%]; mean age at diagnosis 14.8 ± 10.5 years; mean follow-up 4.2 ± 4.8 years) who were given return-to-play approval. Overall, 79 of 494 athletes with LQTS (16.0%) were symptomatic before diagnosis, and 58 (11.7%) had an implantable cardioverter-defibrillator. In 2,056 combined years of follow-up, there was no GHD-sports associated mortality. Instead, 29 patients (5.9%) had ≥1 nonlethal, LQTS-associated breakthrough cardiac event. Of those, 15 (3.0%) were athletes at the time of the breakthrough cardiac event, with 3 (0.6%) experiencing a sports-related breakthrough cardiac event, and 12 (2.4%) a non-sports-related event. Overall, the event rate was 1.16 nonlethal events per 100 athlete-years of follow-up.

CONCLUSIONS

This 20-year single center experience challenges the status quo of disqualification for all athletes with LQTS and provides additional observational evidence, albeit from a single center, in support of the more contemporary SDM approaches to this complex issue.

Failure to follow up on a medically actionable finding from direct to consumer genetic testing: A case report

BACKGROUND

A 61-year-old woman underwent direct to consumer genetic testing and was found to be homozygous for the C282Y HFE variant (c.845G>A :p.Cys282Tyr) which is classified as pathogenic/likely pathogenic for hereditary hemochromatosis. However, no action was taken by the individual.

METHODS

The individual took part in the Mayo Clinic Return of Actionable Variants Empiric (RAVE) study and the actionable finding was confirmed and results disclosed in person by a genetic counselor with subsequent referral to a hepatologist.

RESULTS

Further testing revealed iron overload with an elevated ferritin level (560 ng/ml) and increased ferritin saturation (74%). Phlebotomy was initiated with subsequent normalization of the ferritin levels (252 ng/ml).

CONCLUSION

This case highlights that actionable genetic results may not be acted on after direct to consumer testing and the need for effective genetic counseling after such testing.

Hypokalemia, metabolic alkalosis, and hypertension: Cushing's syndrome in a patient with metastatic prostate adenocarcinoma

Ectopic adrenocorticotropic hormone (ACTH) and/or corticotropin-releasing hormone (CRH) are associated with a growing list of tumors. We report a 69-year-old white man with a history of high-grade prostate carcinoma and widely metastatic adenocarcinoma who presented with metabolic alkalosis, hypokalemia, and hypertension secondary to ectopic ACTH and CRH secretion. Laboratory values were consistent with hypokalemia and metabolic alkalosis. Markedly elevated serum cortisol (135 microg/dL), ACTH (1,387 pg/dL), CRH (69 pg/dL), and urine free cortisol (16,276 microg/24 h) levels were found. Chest computed tomographic (CT) scan showed small noncalcified parenchymal densities; however, bronchoscopy and bronchoalveolar lavage washings were unremarkable for a neoplastic process. Abdominal CT scan and magnetic resonance imaging showed multiple small liver lesions and multiple thoracic and lumbar intensities consistent with diffuse metastatic disease. Histological analysis of a biopsy specimen from the thoracic spine showed an undifferentiated adenocarcinoma consistent with a prostate primary tumor. The severe metabolic alkalosis secondary to glucocorticoid-induced excessive mineralocorticoid activity was treated with potassium supplements, spironolactone, and ketoconazole. In this case report, we describe an unusual tumor associated with ectopic ACTH and CRH production and the pharmacodynamic relationship of plasma cortisol levels and urinary cortisol excretion with ketoconazole treatment.