The mechanistic pathways of oxidative stress in aortic stenosis and clinical implications

Despite the elucidation of the pathways behind the development of aortic stenosis (AS), there remains no effective medical treatment to slow or reverse its progress. Instead, the gold standard of care in severe or symptomatic AS is replacement of the aortic valve. Oxidative stress is implicated, both directly as well as indirectly, in lipid infiltration, inflammation and fibro-calcification, all of which are key processes underlying the pathophysiology of degenerative AS. This culminates in the breakdown of the extracellular matrix, differentiation of the valvular interstitial cells into an osteogenic phenotype, and finally, calcium deposition as well as thickening of the aortic valve. Oxidative stress is thus a promising and potential therapeutic target for the treatment of AS. Several studies focusing on the mitigation of oxidative stress in the context of AS have shown some success in animal and in vitro models, however similar benefits have yet to be seen in clinical trials. Statin therapy, once thought to be the key to the treatment of AS, has yielded disappointing results, however newer lipid lowering therapies may hold some promise. Other potential therapies, such as manipulation of microRNAs, blockade of the renin-angiotensin-aldosterone system and the use of dipeptidylpeptidase-4 inhibitors will also be reviewed.

The obesity paradox: association of obesity with improved survival in medically managed severe aortic stenosis

INTRODUCTION

The obesity paradox, where obesity is associated with improved survival, has been described in patients undergoing haemodialysis and in those with heart failure. It was also demonstrated in patients undergoing valve replacement for aortic stenosis (AS). We explored this phenomenon in medically managed severe AS.

METHODS

154 patients with medically managed severe AS (aortic valve area index [AVAi] < 0.6 cm2/m2; mean pressure gradient > 40 mmHg and peak velocity > 400 cm/s) and preserved left ventricular ejection fraction (> 50%) were categorised into the obese (body mass index [BMI] Asian cut-off ≥ 27.5 kg/m2) and non-obese groups. Their clinical and echocardiographic profiles were compared.

RESULTS

24 (15.6%) patients were obese. Obese patients were similar to non-obese patients in age (68.5 ± 11.6 years vs. 68.9 ± 13.1 years) but had higher prevalence of cardiovascular risk factors. Left atrial diameter (43.7 ± 6.7 mm vs. 38.5 ± 10.2 mm) was larger in obese patients, while left ventricular outflow tract diameter (19.5 ± 1.7 mm vs. 20.4 ± 2.1 mm) was smaller. Despite lower AVAi in obese patients (0.36 ± 0.10 cm2/m2 vs. 0.43 ± 0.11 cm2/m2), there was lower mortality (37.5% vs. 41.0%, log-rank 4.06, p = 0.045) on follow-up (8.0 ± 5.7 years). After adjusting for age and AVAi, higher BMI ≥ 27.5 kg/m2 remained protective for mortality (hazard ratio 0.38, 95% confidence interval 0.15 to 0.98, p = 0.046).

CONCLUSION

We demonstrated that obesity was associated with improved survival in severe AS despite lower AVAi and increased prevalence of cardiovascular risk factors.

Effects of Sodium/Glucose Cotransporter 2 (SGLT2) Inhibitors on Cardiac Imaging Parameters: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Recent studies have shown that sodium/glucose cotransporter 2 (SGLT2) inhibitors might exert favourable changes on cardiac parameters as observed on cardiovascular imaging. We conducted a systematic review and meta-analysis to determine the effects of SGLT2 inhibitors on cardiac imaging parameters. Four electronic databases (PubMed, Embase, Cochrane, Scopus) were searched for studies in which the effects of SGLT2 inhibitors on cardiac imaging parameters were examined. Studies in which a population was administered SGLT2 inhibitors and analysed by echocardiography and/or cardiac magnetic resonance (CMR) imaging were included. Random-effects pair-wise meta-analysis models were utilized to summarize the studies. A total of 11 randomized controlled trials was included with a combined cohort of 910 patients. Comparing patients receiving SGLT2 inhibitors with subjects receiving placebo, the mean change in CMR-measured left ventricular mass (LVM) was −3.87 g (95% confidence interval [CI], −7.77 to 0.04), that in left ventricular end-systolic volume (LVESV) was −5.96 mL (95% CI, −10.52 to −1.41) for combined LVESV outcomes, that in left atrial volume index (LAVi) was −1.78 mL/m² (95% CI, −3.01 to −0.55) for combined LAVi outcomes, and that in echocardiography-measured E/e′ was −0.73 (95% CI, −1.43 to −0.03). Between-group differences were not observed in LVM and LVESV after indexation. The only between-group difference that persisted was for LAVi. Treatment with SGLT2 inhibitors resulted in reduction in LAVi and E/e′ on imaging, indicating they might have an effect on outcomes associated with LV diastolic function.

Sleep position and infant care practices in an urban community in Kuala Lumpur

Several modifiable risk factors for sudden infant death syndrome (SIDS) have been identified such as sleeping prone or on the side, sleeping on a soft surface, bed-sharing, no prenatal care and maternal ante-natal smoking. A cross-sectional survey of infant sleep and care practices was conducted among parents of babies aged below 8 months to determine the prevalence and predictors of non-supine sleep position and the prevalence of other high-risk infant care practices for SIDS. Of 263 infants, 24.7% were placed to sleep in the non-supine position and age of infants was a factor positively associated with this (adjusted odds ratio 1.275, 95% CI=1.085, 1.499). The most common modifiable risk factor was the presence of soft toys or bedding in the infants' bed or cot (89.4%). Results from this study indicate that although the predominant sleep position of Malaysian infants in this population is supine, the majority of infants were exposed to other care practices which have been shown to be associated with SIDS.