Sudden infant death syndrome and cardiac arrhythmias

Bacterial toxins and heart function: heat-labile Escherichia coli enterotoxin B promotes changes in cardiac function with possible relevance for sudden cardiac death

Bacterial toxins can cause cardiomyopathy, though it is not its most common cause. Some bacterial toxins can form pores in the membrane of cardiomyocytes, while others can bind to membrane receptors. Enterotoxigenic E. coli can secrete enterotoxins, including heat-resistant (ST) or labile (LT) enterotoxins. LT is an AB5-type toxin that can bind to specific cell receptors and disrupt essential host functions, causing several common conditions, such as certain diarrhea. The pentameric B subunit of LT, without A subunit (LTB), binds specifically to certain plasma membrane ganglioside receptors, found in lipid rafts of cardiomyocytes. Isolated guinea pig hearts and cardiomyocytes were exposed to different concentrations of purified LTB. In isolated hearts, mechanical and electrical alternans and an increment of heart rate variability, with an IC50 of ~0.2 μg/ml LTB, were observed. In isolated cardiomyocytes, LTB promoted significant decreases in the amplitude and the duration of action potentials. Na+ currents were inhibited whereas L-type Ca2+ currents were augmented at their peak and their fast inactivation was promoted. Delayed rectifier K+ currents decreased. Measurements of basal Ca2+ or Ca2+ release events in cells exposed to LTB suggest that LTB impairs Ca2+ homeostasis. Impaired calcium homeostasis is linked to sudden cardiac death. The results are consistent with the recent view that the B subunit is not merely a carrier of the A subunit, having a role explaining sudden cardiac death in children (SIDS) infected with enterotoxigenic E. coli, explaining several epidemiological findings that establish a strong relationship between SIDS and ETEC E. coli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01100-6.

Optimise the microbial flora with milk and yoghurt to prevent disease

Pathogenic bacteria, which are temporary or permanent members of our microbial flora, cause or contribute to a wide range of human disease at all ages. Conditions include Alzheimer's disease, atherosclerosis, diabetes mellitus, obesity, cancer, autoimmunity and psychosis, amongst others. The mechanism of damage is inflammation which can be chronic or acute. An optimal microbial flora includes a wide range of pathogenic bacteria in low dose. This allows specific immunity to be developed and maintained with minimal inflammatory damage. Human milk has evolved to deliver an optimal microbial flora to the infant. Cow's milk has the potential, following appropriate fortification, to maintain an optimal human microbial flora throughout life. Yoghurt is a fermented milk product in which bacteria normally present in milk convert sugars to lactic acid. The acid suppresses the growth of pathogens in the oral cavity, oropharynx and oesophagus. Thus yoghurt can restore an optimal flora in these regions in the short term. Since bacteria are transported between epithelial surfaces, yoghurt will also optimise the flora elsewhere. The judicious use of milk and yogurt could prevent a high proportion of human disease.

Assessing the knowledge of sudden unexpected death in the young among Canadian medical students and recent graduates: a cross-sectional study

OBJECTIVE

To determine the level of knowledge concerning Sudden Unexpected Death in the Young (SUDY) among Canadian medical students and recent graduates (≤5 years after graduating).

DESIGN

A cross-sectional study was conducted by distributing a standardised, multiple choice, online questionnaire which assessed basic knowledge of SUDY.

SETTING

Canadian medical schools and residency training programmes.

PARTICIPANTS

614 Canadian medical students (in either their penultimate or final year) and recent graduates (≤5 years after graduating) completed an anonymous online questionnaire.

PRIMARY AND SECONDARY OUTCOME MEASURES

The level of knowledge regarding molecular aetiology, clinical presentation, pharmacological management and modes of inheritance of six of the commonest conditions causing SUDY, including hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQT) and Wolff-Parkinson White syndrome (WPW), were compared between medical students and recent graduates. Questions were broken down into basic knowledge and advanced categories and analysed as a secondary outcome measure.

RESULTS

Of 614 responses, approximately two-thirds were answered by recent graduates, who generally scored 10% higher on all subject categories than medical students. Overall, questions regarding HCM were best answered (40%), followed by WPW syndrome (32%), CPVT (30%), ARVC (23%), Brugada syndrome (21%) and LQT syndrome (17%). Questions categorised as basic knowledge were answered 30% and 39% correctly in medical student and recent graduate groups, respectively, and those in the advanced category were answered 20% and 25% correctly.

CONCLUSIONS

Survey respondents fared poorly when answering questions regarding SUDY, which may be a reflection of inadequate medical education regarding these disorders. Standardised teaching regarding SUDY needs to occupy a stronger focus in Canadian medical curricula in order to prevent more unnecessary deaths by these syndromes in the future.

Ljungan virus: a commentary on its association with fetal and infant morbidity and mortality in animals and humans

Epidemiologic and experimental data support the notion that Ljungan virus (LV), endemic in some rodent populations in Sweden, Denmark, and the United States, can cause morbidity and mortality in animals and humans. LV infection can cause type I diabetes mellitus, myocarditis, and encephalitis in bank voles and experimental mice, and lemmings. Mouse dams infected with LV experience high rates of stillbirth that may persist across generations, and their fetuses may develop cranial, brain, and limb malformations. In humans, epidemiologic and serologic data suggest that LV infection correlates with intrauterine fetal death, malformations, placental inflammation, myocarditis, encephalitis, and Guillain-Barré syndrome. The proposed role of LV infection in SIDS is unconvincing. Further research is necessary to clarify the role of LV infection in animal and human disease.