Plasma free thyroxine in the upper quartile is associated with an increased incidence of major cardiovascular events in older men that do not have thyroid dysfunction according to conventional criteria

Minor perturbations of thyroid homeostasis and major cardiovascular endpoints—Physiological mechanisms and clinical evidence

It is well established that thyroid dysfunction is linked to an increased risk of cardiovascular morbidity and mortality. The pleiotropic action of thyroid hormones strongly impacts the cardiovascular system and affects both the generation of the normal heart rhythm and arrhythmia. A meta-analysis of published evidence suggests a positive association of FT4 concentration with major adverse cardiovascular end points (MACE), but this association only partially extends to TSH. The risk for cardiovascular death is increased in both subclinical hypothyroidism and subclinical thyrotoxicosis. Several published studies found associations of TSH and FT4 concentrations, respectively, with major cardiovascular endpoints. Both reduced and elevated TSH concentrations predict the cardiovascular risk, and this association extends to TSH gradients within the reference range. Likewise, increased FT4 concentrations, but high-normal FT4 within its reference range as well, herald a poor outcome. These observations translate to a monotonic and sensitive effect of FT4 and a U-shaped relationship between TSH and cardiovascular risk. Up to now, the pathophysiological mechanism of this complex pattern of association is poorly understood. Integrating the available evidence suggests a dual etiology of elevated FT4 concentration, comprising both ensuing primary hypothyroidism and a raised set point of thyroid function, e. g. in the context of psychiatric disease, chronic stress and type 2 allostatic load. Addressing the association between thyroid homeostasis and cardiovascular diseases from a systems perspective could pave the way to new directions of research and a more personalized approach to the treatment of patients with cardiovascular risk.

Cohort study examining the relationship between remoteness and requirement for surgery to treat peripheral artery disease at a tertiary hospital in North Queensland

OBJECTIVE

To assess whether outcomes of peripheral artery disease (PAD) were related to remoteness from the treating tertiary vascular centre.

SETTING AND PARTICIPANTS

Participants with a variety of types of occlusive and aneurysmal diseases were recruited from a tertiary hospital in North Queensland, Australia. Remoteness was assessed by residence outside Townsville and estimated distance to the vascular centre. Cox proportional hazard analyses were used to examine the association of remoteness with outcome.

DESIGN

Cohort study.

MAIN OUTCOME MEASURES

The primary outcome was requirement for surgery to treat PAD. Secondary outcomes were major adverse cardiovascular events (MACE) and all-cause mortality.

RESULTS

Of 2487 patients recruited, 1274 (51.2%) had at least one PAD surgery, 720 (29.0%) at least one MACE, and 909 (36.6%) died during a median of 4.2 (inter-quartile range 1.3-7.7) years. Compared to Townsville residents (n = 1287), those resident outside Townsville (n = 1200) had higher rates of PAD surgery (hazard ratio, HR 1.55, 95% confidence intervals, CI, 1.39, 1.73) but no increased risk of MACE (HR 1.00, 95% CI 0.86, 1.16) or death (HR 1.03, 95% CI 0.90, 1.17). This association was attenuated when adjusting for distance from the vascular centre (HR 1.31, 95% CI 1.14, 1.51). Patients in the highest quartile of distance presented with lower ankle-brachial pressure index, more severe carotid artery disease and larger aortic diameter.

CONCLUSIONS

People with PAD in North Queensland residing furthest from the tertiary hospital presented with more severe artery disease and had greater rates of PAD surgery.

Predictive Value of Free Triiodothyronine to Free Thyroxine Ratio in Euthyroid Patients With Myocardial Infarction With Nonobstructive Coronary Arteries

BACKGROUND

Thyroid function is closely involved in cardiovascular diseases. The free triiodothyronine (fT3) to free thyroxine (fT4) ratio has been reported as a risk factor for coronary artery disease, but its prognostic value in euthyroid patients with myocardial infarction with nonobstructive coronary arteries (MINOCA) remains unclear.

METHODS

A total of 1162 euthyroid patients with MINOCA were enrolled and divided according to decreased tertiles of fT3/fT4 ratio. The study endpoint was major adverse cardiovascular events (MACE), including all-cause death, nonfatal MI, nonfatal stroke, revascularization, and hospitalization for unstable angina or heart failure. Kaplan-Meier, Cox regression, and receiver-operating characteristic analyses were performed.

RESULTS

Patients with lower fT3/fT4 tertile levels had a significantly higher incidence of MACE (10.0%, 13.9%, 18.2%; p=0.005) over the median follow-up of 41.7 months. The risk of MACE increased with the decreasing fT3/fT4 tertiles even after multivariate adjustment (tertile1 as reference, tertile2: HR 1.58, 95% CI: 1.05-2.39, p=0.030; tertile3: HR 2.06, 95% CI: 1.17-3.11, p=0.006). Lower level of fT3/fT4 ratio remained a robust predictor of MACE in overall (HR 1.64, 95% CI: 1.18-2.29, p=0.003) and in subgroups. When adding fT3/fT4 ratio [area under the curve (AUC) 0.61] into the thrombolysis in myocardial infarction (TIMI) risk score (AUC 0.69), the combined model (AUC 0.74) yielded a significant improvement in discrimination for MACE (ΔAUC 0.05, p=0.023).

CONCLUSIONS

Low level of fT3/fT4 ratio was strongly associated with a poor prognosis in euthyroid patients with MINOCA. Routine assessment of fT3/fT4 ratio may facilitate risk stratification in this specific population.

Survival following abdominal aortic aneurysm repair in North Queensland is not associated with remoteness of place of residence

Objective

To assess whether survival and clinical events following elective abdominal aortic aneurysm (AAA) repair were associated with remoteness of residence in North Queensland, Australia.

Methods

This retrospective cohort study included participants undergoing elective AAA repair between February 2002 and April 2020 at two hospitals in Townsville, North Queensland, Australia. Outcomes were all-cause survival and AAA-related events, defined as requirement for repeat AAA repair or AAA-related mortality. Remoteness of participant’s place of residence was assessed by the Modified Monash Model classifications and estimated distance from the participants’ home to the tertiary vascular centre. Cox proportional hazard analysis examined the association of remoteness with outcome.

Results

The study included 526 participants undergoing elective repair by open (n = 204) or endovascular (n = 322) surgery. Fifty-four (10.2%) participants had a place of residence at a remote or very remote location. Participants' were followed for a median of 5.2 (inter-quartile range 2.5–8.3) years, during which time there were 252 (47.9%) deaths. Survival was not associated with either measure of remoteness. Fifty (9.5%) participants had at least one AAA-related event, including 30 (5.7%) that underwent at least one repeat AAA surgery and 23 (4.4%) that had AAA-related mortality. AAA-related events were more common in participants resident in the most remote areas (adjusted hazard ratio 2.83, 95% confidence intervals 1.40, 5.70) but not associated with distance from the participants’ residence to the tertiary vascular centre

Conclusions

The current study found that participants living in more remote locations were more likely to have AAA-related events but had no increased mortality following AAA surgery. The findings emphasize the need for careful follow-up after AAA surgery. Further studies are needed to examine the generalisability of the findings.