Thyroid dysfunction and incident heart failure phenotypes among older adults: the atherosclerosis risk in communities (aric) study

Background/Introduction

Abnormal thyroid hormone concentrations have been associated with adverse cardiovascular outcomes, but the relationship between thyroid dysfunction and specific heart failure phenotypes is less clear.

Purpose

To examine the association of thyroid dysfunction with the risk of incident HF in older adults without pre-existing HF.

Methods

We analyzed participants enrolled in the Atherosclerosis Risk in Communities (ARIC) study who attended the visit 5 examination (2011–2013). Participants with previous HF history, and participants treated with amiodarone, levothyroxine, and antithyroid medication were excluded. We used Cox regression models to assess the associations between serum thyroid indices (free thyroxine [FT4], total triiodothyronine [TT3], or thyroid stimulating hormone [TSH]) and incident adjudicated HF with reduced (HFrEF) and preserved (HFpEF) left ventricular ejection fraction. Continuous associations between TT3 and outcome were further assessed via Cox model using restricted cubic spline.

Results

Among 3349 participants (mean age 75±5 years, 56% women, 20% black), subclinical hypothyroidism was prevalent in 12% of participants and low T3 syndrome in 3%. Those with overt hypothyroidism (<1%) or hyperthyroidism (<1%) were not included in the analysis given the low prevalence. Over a median follow-up of 5.5 years, incident HF occurred in 198 subjects (5.9%) at a rate of 11.1 per 1000 person-years. Of these, 86 were HFrEF, 83 HFpEF, and 29 were unclassified HF. We observed an inverse association of TT3 level with risk of incident HFpEF, but not overall incident HF or incident HFrEF, after adjustment for clinical confounders and baseline NT-proBNP levels (HR per 1 SD 0.70, 95% CI 0.54–0.92; P 0.010) (Figure). Similar results were observed for the composite endpoint of incident HFpEF or all-cause death. No statistically significant associations were found between TSH or T4 levels and incident HF. Low T3 syndrome was associated with incident HFpEF, but not overall incident HF or incident HFrEF, after adjustment for clinical confounders (HR 2.71, 95% CI 1.08–6.82; P 0.035); however, its association was significantly attenuated after adjustment with NT-proBNP (HR 2.25, 95% CI 0.87–5.79; P 0.09). No statistically significant association was found between subclinical hypothyroidism and incident HF.

Conclusions

In a contemporary biracial cohort of older adults, serum T3 level was inversely associated with incident HFpEF hospitalization. T3 administration could be considered as a potential target in future clinical trials preventing HFpEF hospitalization.

Figure 1

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): The Atherosclerosis Risk in Communities Study is performed as a collaborative study supported by National Heart, Lung, and Blood Institute contracts

Masked nocturnal hypertension--a novel marker of risk in type 2 diabetes

AIMS/HYPOTHESIS

This study was designed to evaluate the prevalence of masked nocturnal hypertension (MNHT) and its impact on arterial stiffness and central blood pressure in patients with type 2 diabetes.

METHODS

Middle-aged patients (n = 414) with type 2 diabetes underwent clinic and ambulatory BP measurements and applanation tonometry.

RESULTS

MNHT (clinic BP < 130/80 mmHg and night-time BP > or = 120/70 mmHg) was found in 7.2% of patients (n = 30). Compared with patients with both clinical and nocturnal normotension (n = 70), patients with MNHT had higher aortic pulse wave velocity (PWV) (10.2 +/- 1.8 m/s vs 9.4 +/- 1.7 m/s; p = 0.03) and higher central BP (117.6 +/- 13.9/74.0 +/- 9.1 mmHg vs 110.4 +/- 16.4/69.7 +/- 9.6 mmHg, p = 0.04). In patients with clinical normotension, night-time systolic BP correlated significantly with PWV.

CONCLUSIONS/INTERPRETATION

Thirty per cent of patients with clinical normotension had nocturnal hypertension. This was accompanied by increased arterial stiffness and higher central BP. We conclude that in clinically normotensive patients with type 2 diabetes, ambulatory BP measurement may help clinicians to identify patients with increased cardiovascular risk.

Characterisation of the signal transduction cascade caused by propofol in rat neurons: from the GABA(A) receptor to the cytoskeleton

The anaesthetic propofol interacts with the GABA(A) receptor, but its cellular signalling pathways are not fully understood. Propofol causes reorganisation of the actin cytoskeleton into ring structures in neurons. Is this reorganisation a specific effect of propofol as apposed to GABA, and which cellular pathways are involved? We used fluorescence-marked actin in cultured rat neurons to evaluate the percentage of actin rings caused by propofol or GABA in combination with rho, rho kinase (ROK), PI3-kinase or tyrosine kinase inhibitors, with or without the presence of extracellular calcium. Confocal microscopy was performed on propofol-stimulated cells and changes in actin between cellular compartments were studied with Western blot. Propofol (3 microg x ml-1), but not GABA (5 microM), caused transcellular actin ring formation, that was dependent on influx of extracellular calcium and blocked by rho, ROK, PI3-kinase or tyrosine kinase inhibitors. Propofol uses rho/ROK to translocate actin from the cytoskeleton to the membrane and its actin ring formation is dependent on an interaction site close to the GABA site on the GABA(A) receptor. GABA does not cause actin rings, implying that this is a specific effect of propofol.