Novel coronavirus 19 (COVID-19) associated sinus node dysfunction: a case series

BACKGROUND

Novel coronavirus-19 disease (COVID-19) is associated with significant cardiovascular morbidity and mortality. To date, there have not been reports of sinus node dysfunction (SND) associated with COVID-19. This case series describes clinical characteristics, potential mechanisms, and short-term outcomes of COVID-19 patients who experience de novo SND.

CASE SUMMARY

We present two cases of new-onset SND in patients recently diagnosed with COVID-19. Patient 1 is a 70-year-old female with no major past medical history who was intubated for acute hypoxic respiratory failure secondary to COVID-19 pneumonia and developed new-onset sinus bradycardia without a compensatory increase in heart rate in response to relative hypotension. Patient 2 is an 81-year-old male with a past medical history of an ascending aortic aneurysm, hypertension, and obstructive sleep apnoea who required intubation for COVID-19-induced acute hypoxic respiratory failure and exhibited new-onset sinus bradycardia followed by numerous episodes of haemodynamically significant accelerated idioventricular rhythm. Two weeks following the onset of SND, both patients remain in sinus bradycardia.

DISCUSSION

COVID-19-associated SND has not previously been described. The potential mechanisms for SND in patients with COVID-19 include myocardial inflammation or direct viral infiltration. Patients diagnosed with COVID-19 should be monitored closely for the development of bradyarrhythmia and haemodynamic instability.

Genetic Determinants of Glycemic Traits and the Risk of Gestational Diabetes Mellitus

Many common genetic polymorphisms are associated with glycemic traits and type 2 diabetes (T2D), but knowledge about genetic determinants of glycemic traits in pregnancy is limited. We tested genetic variants known to be associated with glycemic traits and T2D in the general population for associations with glycemic traits in pregnancy and gestational diabetes mellitus (GDM). Participants in two cohorts (Genetics of Glucose regulation in Gestation and Growth [Gen3G] and Hyperglycemia and Adverse Pregnancy Outcome [HAPO]) underwent oral glucose tolerance testing at 24-32 weeks' gestation. We built genetic risk scores (GRSs) for elevated fasting glucose and insulin, reduced insulin secretion and sensitivity, and T2D, using variants discovered in studies of nonpregnant individuals. We tested for associations between these GRSs, glycemic traits in pregnancy, and GDM. In both cohorts, the fasting glucose GRS was strongly associated with fasting glucose. The insulin secretion and sensitivity GRSs were also significantly associated with these traits in Gen3G, where insulin measurements were available. The fasting insulin GRS was weakly associated with fasting insulin (Gen3G) or C-peptide (HAPO). In HAPO (207 GDM case subjects), all five GRSs (T2D, fasting glucose, fasting insulin, insulin secretion, and insulin sensitivity) were significantly associated with GDM. In Gen3G (43 GDM case subjects), both the T2D and insulin secretion GRSs were associated with GDM; effect sizes for the other GRSs were similar to those in HAPO. Thus, despite the profound changes in glycemic physiology during pregnancy, genetic determinants of fasting glucose, fasting insulin, insulin secretion, and insulin sensitivity discovered outside of pregnancy influence GDM risk.

Identification of HKDC1 and BACE2 as genes influencing glycemic traits during pregnancy through genome-wide association studies

Maternal metabolism during pregnancy impacts the developing fetus, affecting offspring birth weight and adiposity. This has important implications for metabolic health later in life (e.g., offspring of mothers with pre-existing or gestational diabetes mellitus have an increased risk of metabolic disorders in childhood). To identify genetic loci associated with measures of maternal metabolism obtained during an oral glucose tolerance test at ∼28 weeks' gestation, we performed a genome-wide association study of 4,437 pregnant mothers of European (n = 1,367), Thai (n = 1,178), Afro-Caribbean (n = 1,075), and Hispanic (n = 817) ancestry, along with replication of top signals in three additional European ancestry cohorts. In addition to identifying associations with genes previously implicated with measures of glucose metabolism in nonpregnant populations, we identified two novel genome-wide significant associations: 2-h plasma glucose and HKDC1, and fasting C-peptide and BACE2. These results suggest that the genetic architecture underlying glucose metabolism may differ, in part, in pregnancy.