Perspectives on mitral-valve prolapse

Chromatin Accessibility of Human Mitral Valves and Functional Assessment of MVP Risk Loci

RATIONALE

Mitral valve prolapse (MVP) is a common valvopathy that leads to mitral insufficiency, heart failure, and sudden death. Functional genomic studies in mitral valves are needed to better characterize MVP-associated variants and target genes.

OBJECTIVE

To establish the chromatin accessibility profiles and assess functionality of variants and narrow down target genes at MVP loci.

METHODS AND RESULTS

We mapped the open chromatin regions in nuclei from 11 human pathogenic and 7 nonpathogenic mitral valves by an assay for transposase-accessible chromatin with high-throughput sequencing. Open chromatin peaks were globally similar between pathogenic and nonpathogenic valves. Compared with the heart tissue and cardiac fibroblasts, we found that MV-specific assay for transposase-accessible chromatin with high-throughput sequencing peaks are enriched near genes involved in extracellular matrix organization, chondrocyte differentiation, and connective tissue development. One of the most enriched motifs in MV-specific open chromatin peaks was for the nuclear factor of activated T cells family of TFs (transcription factors) involved in valve endocardial and interstitial cell formation. We also found that MVP-associated variants were significantly enriched (P<0.05) in mitral valve open chromatin peaks. Integration of the assay for transposase-accessible chromatin with high-throughput sequencing data with risk loci, extensive functional annotation, and gene reporter assay suggest plausible causal variants for rs2641440 at the SMG6/SRR locus and rs6723013 at the IGFBP2/IGFBP5/TNS1 locus. CRISPR-Cas9 deletion of the sequence including rs6723013 in human fibroblasts correlated with increased expression only for TNS1. Circular chromatin conformation capture followed by high-throughput sequencing experiments provided evidence for several target genes, including SRR, HIC1, and DPH1 at the SMG6/SRR locus and further supported TNS1 as the most likely target gene on chromosome 2.

CONCLUSIONS

Here, we describe unprecedented genome-wide open chromatin profiles from human pathogenic and nonpathogenic MVs and report specific gene regulation profiles, compared with the heart. We also report in vitro functional evidence for potential causal variants and target genes at MVP risk loci involving established and new biological mechanisms. Graphic Abstract: A graphic abstract is available for this article.

Imaging of Mitral Valve Prolapse: What Can We Learn from Imaging about the Mechanism of the Disease?

Mitral valve prolapse (MVP) is the most common mitral valve disorder affecting 2%-3% of the general population. Two histological forms for the disease exist: Myxomatous degeneration and fibroelastic disease. Pathological evidence suggests the disease is not confined solely to the valve tissue, and accumulation of proteoglycans and fibrotic tissue can be seen in the adjacent myocardium of MVP patients. MVP is diagnosed by demonstrating valve tissue passing the annular line into the left atrium during systole. In this review we will discuss the advantages and limitations of various imaging modalities in their MVP diagnosis ability as well as the potential for demonstrating extra associated valvular pathologies.

Mitral valve prolapse syndrome as cause of sudden death in young adults

Mitral valve prolapse syndrome (MVPS) is a relatively common disorder of the mitral valve and most cases take a benign clinical course. Only a subset of patients develop severe clinical symptoms such as arrhythmia, insufficiency of the mitral valve or infective endocarditis. As a consequence, sudden death might occur in these patients, thought to be caused by an arrhythmogenic event. By presenting six cases of sudden unexpected death in young female adults, we point at clinical and pathological data from the literature, which are of interest from the viewpoint of legal medicine. The incidence of MVPS in autopsy series has been reported to be about 4-5%, while clinical data hint at an incidence of about 2.5%. The presented cases suggest that even clinically benign cases of MVPS in young adults might result in sudden unexpected death. Such cases are not included in hospital based studies on the topic. This might lead to an underestimation of the fatal risk associated with the disease, even if sudden death might be a rare event in MVPS.

Antithrombotic and interventional treatment options in cardioembolic transient ischaemic attack and ischaemic stroke

Peer-reviewed data pertaining to anti-thrombotic and interventional therapy for transient ischaemic attack (TIA) or ischaemic stroke patients with non-valvular atrial fibrillation, atrial flutter, interatrial septal abnormalities, or left ventricular thrombus were reviewed. Long-term oral anticoagulant therapy with warfarin is the treatment of choice for secondary stroke prevention following TIA or minor ischaemic stroke in association with persistent or paroxysmal non-valvular atrial fibrillation or atrial flutter. If warfarin is contraindicated, long-term aspirin is a safe, but much less effective alternative treatment option in this subgroup of patients with cerebrovascular disease. Management of young patients with TIA or stroke in association with an interatrial septal defect is controversial. Various treatment options are outlined, but readers are encouraged to include these patients in one of the ongoing randomised clinical trials in this area. It is reasonable to consider empirical anticoagulation in patients with TIA or ischaemic stroke in association with left ventricular thrombus formation following myocardial infarction or in association with idiopathic dilated cardiomyopathy. If warfarin is prescribed, one should aim for a target international normalised ratio of 2.5 (range 2-3) to achieve the best balance between adequate secondary prevention of cardioembolic events and the risk of major haemorrhagic complications.

Mitral valve prolapse in systemic lupus erythematosus patients: clinical and immunological aspects

Mitral valve prolapse (MVP) has been reported to be associated with systemic lupus erythematosus (SLE). The aim of the present study was to determine the prevalence of MVP in SLE patients, assess its clinical significance and examine the possible association of this entity with other autoimmune indices. Eighty-seven consecutive SLE patients attending the rheumatology clinic and 73 normal control subjects were examined by M-mode, two-dimensional color-Doppler echocardiography. Serum samples were examined for various organ and non-organ specific autoantibodies. MVP was detected in 19/87 patients with SLE and in four of the healthy controls(P = 0.0057). SLE patients with MVP were younger (33.6 +/- 12.4 years) than those without MVP (41. +/- 12.9, P = 0.04) and with shorter duration of the disease (P = 0.03). We found a statistically higher prevalence of anticardiolipin antibodies (aCL) in SLE patients with prolapse (11/19) compared with SLE patients without prolapse (15/68, P = 0.04). This association was independent of age. The aCL-lgG levels were significantly higher in SLE patients with MVP (32.37 +/- 43.26) compared with SLE patients without MVP (22.24 +/- 29.95, P = 0.04). Thyroid autoantibodies tended to be more common in S LE patients with MVP. Th e prevalence of MVP is increased in SLE patients. The presence of aCL and of organ-specific autoantibodies in SLE patients with MVP might indicate the autoimmune origin of MVP. The possibility that SLE patients with MVP may be predisposed to further autoimmune diseases should be considered.

Gemcitabine-induced atrial fibrillation: a hitherto unreported manifestation of drug toxicity

BACKGROUND

Gemcitabine is an antimetabolic drug for solid tumors. Although its pharmacokinetics as well as its side-effects are well known, paroxysmal atrial fibrillation associated to the administration of this drug has not yet been described.

PATIENTS AND METHODS

We describe the case of a 78-year-old man with pancreatic adenocarcinoma who presented repeated paroxysmal atrial fibrillation episodes 18-24 hours after every gemcitabine infusion which resolved with antiarrhythmic drugs. This clinical history was positive for a remote brief episode of atrial fibrillation, which resolved spontaneously, and the patient had no predisposing factors for supraventricular arrhythmias (systemic hypertension, diabetes or coronary artery disease).

RESULTS

Cardiac work-up revealed only a mild mitral-valve prolapse and complete right bundle branch block. During the arrhythmia episodes no other precipitating factors were reported. The close temporal relationship of the arrhythmia to drug administration and the recurrence of arrhythmia upon rechallenge allowed to hypothesize an intrinsic pro-arrhythmic effect of gemcitabine or its metabolite 2',2'-difluorodeoxyuridine.

CONCLUSIONS

The occurrence of atrial fibrillation during the administration of gemcitabine may be considered as a cardiac arrhythmia drug-related toxicity. This side-effect of gemcitabine infusion is a previously unreported sign of drug toxicity; therefore, a high level of awareness to this problem is warranted when this drug is administered.

Neuropathology of mitral valve prolapse in man and cardiopulmonary bypass (CPB) surgery in adolescent Yorkshire pigs

We investigated the brains of non-demented individuals with mitral valve prolapse (MVP) and found evidence of Alzheimer-like lesions. This neuropathology consisted of premature presence of beta-amyloid-containing senile plaques (SP) without increased prevalence of neurofibrillary tangles. Low levels of SP occurred in 20 to 45- year-old subjects with MVP, and much greater densities were observed in subjects between 45 and 62 years of age. We also investigated the brains of adolescent Yorkshire pigs undergoing cardiopulmonary bypass surgery and likewise found evidence of Alzheimer-like neuropathology. This took the form of intraneuronal accumulation of beta-amyloid immunoreactivity and increasing numbers of Alz-50 immunoreactive neurons with reduced recovery of cardiac efficiency after the surgery. Based on prevailing concepts in Alzheimer's disease, it is feasible to hypothesize that cognitive dysfunction occurring after cardiopulmonary bypass surgery with coronary artery grafting or valve repair/replacement is a functional sequela of AD-like neuropathology. This postulate is based on the premise that an individual seeking such surgery would have pre-existing, elevated AD-like neuropathology to start with. It is further coupled with the probability that these forms of cardiovascular surgery exacerbate the extent and progression of AD-like neuropathology.