Autonomic dysregulation as a novel underlying cause of mitral valve prolapse: a hypothesis

Long-term cardiovascular outcomes of gestational diabetes mellitus: a prospective UK Biobank study

BACKGROUND

Previous studies showed that gestational diabetes mellitus (GDM) can be a risk factor for subsequent atherosclerotic cardiovascular disease. However, there is a paucity of information regarding diverse cardiovascular outcomes in elderly women after GDM. In the current study, we examined whether women with a history of GDM have an increased risk for long-term overall cardiovascular outcomes.

METHODS

Among the UK participants, we included 219,330 women aged 40 to 69 years who reported at least one live birth. The new incidence of diverse cardiovascular outcomes was compared according to GDM history by multivariable Cox proportional hazard models. In addition, causal mediation analysis was performed to examine the contribution of well-known risk factors to observed risk.

RESULTS

After enrollment, 13,094 women (6.0%) developed new overall cardiovascular outcomes. Women with GDM history had an increased risk for overall cardiovascular outcomes [adjusted HR (aHR) 1.36 (95% CI 1.18-1.55)], including coronary artery disease [aHR 1.31 (1.08-1.59)], myocardial infarction [aHR 1.65 (1.27-2.15)], ischemic stroke [aHR 1.68 (1.18-2.39)], peripheral artery disease [aHR 1.69 (1.14-2.51)], heart failure [aHR 1.41 (1.06-1.87)], mitral regurgitation [aHR 2.25 (1.51-3.34)], and atrial fibrillation/flutter [aHR 1.47 (1.18-1.84)], after adjustment for age, race, BMI, smoking, early menopause, hysterectomy, prevalent disease, and medication. In mediation analysis, overt diabetes explained 23%, hypertension explained 11%, and dyslipidemia explained 10% of the association between GDM and overall cardiovascular outcome.

CONCLUSIONS

GDM was associated with more diverse cardiovascular outcomes than previously considered, and conventional risk factors such as diabetes, hypertension, and dyslipidemia partially contributed to this relationship.

Respiratory Sinus Arrhythmia as an Index of Cardiac Vagal Control in Mitral Valve Prolapse

Respiratory sinus arrhythmia (RSA), i.e. heart rate (HR) variations during inspiration and expiration, is considered as a noninvasive index of cardiac vagal control. Mitral valve prolapse (MVP) could be associated with increased cardiovascular risk; however, the studies are rare particularly at adolescent age. Therefore, we aimed to study cardiac vagal control indexed by RSA in adolescent patients suffering from MVP using short-term heart rate variability (HRV) analysis. We examined 12 adolescents (girls) with MVP (age 15.9±0.5 years) and 12 age and gender matched controls. Resting ECG was continuously recorded during 5 minutes. Evaluated HRV indices were RR interval (ms), rMSSD (ms), pNN50 (%), log HF (ms(2)), peak HF (Hz) and respiratory rate (breaths/min). RR interval was significantly shortened in MVP group compared to controls (p=0.004). HRV parameters-rMSSD, pNN50 and log HF were significantly lower in MVP compared to controls (p=0.017, p=0.014, p= 0.015 respectively). Our study revealed reduced RSA magnitude indicating impaired cardiac vagal control in MVP already at adolescent age that could be crucial for early diagnosis of cardiovascular risk in MVP.

Sympathetic nervous system and cardiovascular risk in mitral valve prolapse

Mitral valve prolapse (MVP) represents a frequent cardiovascular condition associated with increased cardiovascular risk, which may have progressive course and become malignant. Dysregulation of autonomic nervous system - especially sympathetic overdrive – is one of the factors considered to play a key role in its aetiology and development. There is a growing evidence of a large impact of sympathetic system on the development of MVP. Exaggerated sympathetic activity may lead to morphologic changes in valves tissue such as thickening and redundancy. Nowadays, few investigative methods are known for evaluation of the regulatory state of sympathetic nervous system, which could be, theoretically, used to identify the subjects with sympathetic overactivity associated with an increased cardiovascular risk. Electrodermal activity or blood pressure variability represent promising non-invasive methods for evaluation of the regulatory outputs of sympathetic nervous system. There is a possibility to extend a set of investigative methods in MVP and include the monitoring of sympathetic activity in the assessment of cardiovascular risk. This article summarizes knowledge about pathogenesis, diagnostic and therapeutical approaches of MVP, and brings some novel insights on the parameters of autonomic nervous regulation, which haven’t yet been used in cardiovascular risk assessment in MVP.

Infectious agents is a risk factor for myxomatous mitral valve degeneration: A case control study

BACKGROUND

The etiology of myxomatous mitral valve degeneration (MVD) is not fully understood and may depend on time or environmental factors for which the interaction of infectious agents has not been documented. The purpose of the study is to analyze the effect of Mycoplasma pneumoniae (Mp), Chlamydophila pneumoniae (Cp) and Borrelia burgdorferi (Bb) on myxomatous mitral valve degeneration pathogenesis and establish whether increased in inflammation and collagen degradation in myxomatous mitral valve degeneration etiopathogenesis.

METHODS

An immunohistochemical test was performed to detect the inflammatory cells (CD20, CD45, CD68) and Mp, Bb and MMP9 antigens in two groups. The in situ hybridization was performed to detect Chlamydophila pneumoniae and the bacteria study was performed using transmission electron microscopy. Group 1 (n = 20), surgical specimen composed by myxomatous mitral valve degeneration, and group 2 (n = 20), autopsy specimen composed by normal mitral valve. The data were analyzed using SigmaStat version 20 (SPSS Inc., Chicago, IL, USA). The groups were compared using Student's t test, Mann-Whitney test. A correlation analysis was performed using Spearman's correlation test. P values lower than 0.05 were considered statistically significant.

RESULTS

By immunohistochemistry, there was a higher inflammatory cells/mm2 for CD20 and CD45 in group 1, and CD68 in group 2. Higher number of Mp and Cp antigens was observed in group 1 and more Bb antigens was detected in group 2. The group 1 exhibited a positive correlation between the Bb and MVD percentage, between CD45 and Mp, and between MMP9 with Mp. These correlations were not observed in the group 2. Electron microscopy revealed the presence of structures compatible with microorganisms that feature Borrelia and Mycoplasma characteristics.

CONCLUSIONS

The presence of infectious agents, inflammatory cells and collagenases in mitral valves appear to contribute to the pathogenesis of MVD. Mycoplasma pneumoniae was strongly related with myxomatous mitral valve degeneration. Despite of low percentage of Borrelia burgdorferi in MD group, this agent was correlated with myxomatous degeneration and this may occour due synergistic actions between these infectious agents likely contribute to collagen degradation.

Effect of Fluoxetine Administration on Clinical and Echocardiographic Findings in Patients with Mitral Valve Prolapse and Generalized Anxiety Disorder: Randomized Clinical Trial

Background

Mitral valve prolapse (MVP) is accompanied by mental disorders including anxiety, which has similar presentations as MVP. It is hypothesised that treatment of anxiety might reduce the symptoms of MVP.

Objective

The aim of this study was to assess the clinical and echocardiographic effects of fluoxetine administration in patients with MVP and anxiety.

Methods

This randomized clinical trial was conducted on patients with documented MVP and generalised anxiety disorder (GAD) who were referred to Mashhad University of Medical Sciences cardiology clinics, Mashhad, Iran in 2015. Subjects were randomly assigned to intervention group who received propranolol and fluoxetine (both at 10 mg/day) and control group who received 10 mg/day propranolol. Assessments included echocardiography and GAD-7 questionnaire and rating of chest pain, that were performed at baseline and then weekly for 4 weeks. Analysis was performed using the Mann-Whitney U test and Two-way Repeated Measures Analysis of Variance (ANOVA).

Results

Sixty patients (25 male/ 35 female) with a mean age of 22.9 ± 2.5 years were studied in two groups of intervention (n = 30) and control (n = 30). GAD score was significantly higher in the intervention group (17.37 ± 1.61) compared with the control group (14.17 ± 0.83) (p<0.001). No significant difference was observed for changes in left atrium diameter, mitral annular diameter, left ventricular diameter or ejection fraction (p>0.05). Pain severity was reduced significantly more in control group (3.27 ± 1.26) compared to intervention group (2.80 ± 0.85) after treatment (p<0.001).

Conclusions

This study revealed that the co-administration of fluoxetine and propranolol may not only have no effective in improving echocardiographic changes of MVP but may also aggravate subjective findings of patients with MVP and GAD.

Trial registration

The trial is registered at the Iranian Clinical Trial Registry (IRCT.ir) with the IRCT identification number IRCT2014102819721N1.

Funding

This research has been financially supported by Research Council of Sabzevar University of Medical Sciences.

A novel role of sympathetic activity in regulating mitral valve prolapse

BACKGROUND

Increased sympathetic activity, commonly reported in mitral valve prolapse, indicates that the sympathetic nervous system might play an important role in regulating mitral interstitial cells. Hence, the aim of this study is to determine the level and pattern of adrenergic receptors expressed in human mitral valve leaflets and to investigate the effect of norepinephrine on physiologic behaviors of mitral interstitial cells.

METHODS AND RESULTS

Immunohistochemistry displayed significantly increased expressions of β1, β2, and α1 adrenergic receptors in mitral valve prolapse. Norepinephrine was found to activate the phenotype of interstitial cells with increased α-SMA expression (2.26 fold). In synthesis, norepinephrine downregulated levels of mRNA for type I to type III collagen in ratio, but increased the elastin gene transcription and glycosaminoglycan levels in valve interstitial cells greatly. In view of the extracellular matrix remodel, sympathetic effects presented catabolic metabolism displaying significantly increased expressions of total, secretory and active MMP-2 protein (matrix metalloproteinase-2), as well as MMP-9 protein. Diminished MMP inhibitor expression, TIMP2, also could reflect this effect in the norepinephrine medium.

CONCLUSIONS

A novel role for the sympathetic effect in influencing physiologic behaviors in mitral interstitial cells was identified. It is indicated that sympathetic activity could promote myxomatous degeneration in mitral valve prolapse, propagating the disease severity, which might identify potential therapeutic targets.

The relationship between atrial septal aneurysm and autonomic dysfunction

BACKGROUND

Systemic thromboembolism is a serious, major complication in patients with an atrial septal aneurysm (ASA). Atrial dysfunction resulting from paroxysmal atrial fibrillation is more common in patients with ASA than in the general population. The autonomic nervous system plays an important role in the initiation of atrial fibrillation.

OBJECTIVE

To investigate autonomic function and its impact on ventricular and atrial arrhythmia in a group of ASA patients compared with a control group of healthy volunteers.

METHODS

The study group consisted of 40 patients with ASA; the control group consisted of 30 age-, sex- and body mass index-matched healthy volunteers. All patients and control subjects underwent echocardiographic examination. Autonomic function was assessed by determining heart rate variability (HRV) indexes.

RESULTS

HRV time and frequency domain indexes were lower in patients with ASA compared with healthy controls (188±32 ms(2) and 323±42 ms(2) for low-frequency HRV; 195±39 ms(2) and 377±43 ms(2) for high-frequency HRV; P<0.001 for all). Statistically significant differences with respect to other HRV indexes were also found between the two groups.

CONCLUSION

ASA appears to be associated with cardiac autonomic dysfunction; however, the mechanisms of this association are not known in detail.