It has been demonstrated that heart rate variability (HRV) is predictive of all-cause and cardiovascular mortality using clinical ECG recordings. This is true for rest, exercise and ambulatory HRV clinical ECG device recordings in prospective cohorts. Recently, there has been a rapid increase in the use of mobile health technologies (mHealth) and commercial wearable fitness devices. Most of these devices use ECG or photo-based plethysmography and both are validated for providing accurate heart rate measurements. This offers the opportunity to make risk information from HRV more widely available. The physiology of HRV and the available technology by which it can be assessed has been summarised in Part 1 of this review. In Part 2 the association between HRV and risk stratification is addressed by reviewing the current evidence from data acquired by resting ECG, exercise ECG and medical ambulatory devices. This is followed by a discussion of the use of HRV to guide the training of athletes and as a part of fitness programmes.

The autonomic nervous system plays a major role in optimising function of the cardiovascular (CV) system, which in turn has important implications for CV health. Heart rate variability (HRV) is a measurable reflection of this balance between sympathetic and parasympathetic tone and has been used as a marker for cardiac status and predicting CV outcomes. Recently, the availability of commercially available heart rate (HR) monitoring systems has had important CV health implications and permits ambulatory CV monitoring on a scale not achievable with traditional cardiac diagnostics. The focus of the first part of this two-part review is to summarise the physiology of HRV and to describe available technologies for HRV monitoring. Part two will present HRV measures for assessing CV prognosis and athletic training.

Objective:To identify if the incidence of hypothyroidism in infants with Down syndrome is higher than previous childhood estimates (15%) when examined prior to the standard retesting at 6 months of age.Study design:A retrospective observational cohort study of 122 children with Down syndrome admitted to a university-based birthing hospital between May 2000 and March 2012. Demographic data (for example, date of birth, gender, gestational age, inborn) and diagnostic data (Down syndrome, congenital heart disease and gastrointestinal disease) were cross-linked with thyroid hormone laboratory tests (total thyroxine, free thyroxine and thyroid stimulating hormone) to determine incidence of identified hypothyroidism and thyroid testing prior to 4 months of age (n=80).Result:In all, 32.5% were found to have any hypothyroidism. Of these, 14 were primary hypothyroidism (17.5%) needing supplemental T4 therapy, 12 were compensated hypothyroidism (15%) and euthyroid was identified in 54 infants (67.5%).Conclusion:Despite normal newborn screens, the incidence of any hypothyroidism (early compensated hypothyroidism and primary hypothyroidism) was higher than previously reported.

We report an audit of nine cases of subclinical or normotensive pheochromocytoma managed in our department. This is the first report from India of such a series. During the period 1990-2003 a total of 45 patients of pheochromocytoma were diagnosed and managed in the Department of Endocrine Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences. Among them, nine patients were diagnosed as having subclinical or normotensive pheochromocytoma. Inclusion criteria for normotensive pheochromocytoma were: no previous history of hypertension clinically and, in the previous treatment documents, any episode of symptoms suggesting high blood pressure. The demographic profile, clinical presentation, biochemical investigations, imaging results, surgical notes, and follow-up record were reviewed retrospectively. All patients had a primary complaint of flank/abdominal pain and were normotensive. Seven had elevated urinary metanephrine levels, and one patient had normal values. One patient did not undergo the urinary metanephrine assay. Imaging of the abdomen showed seven adrenal and two extra-adrenal masses (eight had computed tomography scans of the abdomen, and one underwent ultrasonography). After selective alpha-adrenergic blockade (prazosin), surgery was performed. Six patients required infusion of sodium nitroprusside intraoperatively. The final histopathology was pheochromocytoma in all patients. Metanephrine levels were normal during the follow-up. Normotensive pheochromocytomas are a distinct entity, and all adrenal incidentalomas should be investigated for catecholamine hypersecretion. We support the use of preoperative alpha-adrenergic blockade, and these patients should be treated along the same lines as hypertensive pheochromocytoma.

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Prompt airway protection followed by total thyroidectomy within the same hospital admission should be recommended and can be associated with favourable outcome.

Background: High sensitivity troponin-T (hs-TnT) has been associated with mortality in patients hospitalized with COVID-19. We aimed to determine if hs-TnT levels and their timing are independent predictors of adverse events in these patients. Design: Retrospective chart review was performed for all patients hospitalized at our institution between March 23 rd and April 13 th , 2020 who were found to be COVID-19-positive. Clinical, demographic, and laboratory variables including initial and peak hs-TnT were recorded. Univariable and multivariable analyses were completed for a primary composite endpoint of inhospital death, intubation, need for critical care, or cardiac arrest. Results: In the 276 patients analyzed, initial hs-TnT above the median (17ng/L) was associated with increased length of stay, need for vasoactive medications, and death, along with the composite endpoint (OR 3.92, p < 0.001). Multivariable analysis demonstrated that elevated initial hs-TnT was independently associated with the primary endpoint (OR 2.92, p = 0.01). Latepeaking hs-TnT (OR 2.19 for each additional day until peak, p < 0.001) was also independently associated with the composite endpoint. Conclusions: In patients hospitalized with COVID-19, hs-TnT identifies patients at high risk for adverse in-hospital events, and trends of hs-TnT over time, particularly during the first day, provide additional prognostic information.

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