Subclinical Hypothyroidism Might Increase the Risk of Postoperative Atrial Fibrillation after Aortic Valve Replacement

Impact of subclinical hypothyroidism on in-hospital outcomes and long-term mortality among acute myocardial infarction patients with diabetic mellitus

BACKGROUND

Thyroid-stimulating hormone (TSH) has been regarded as a predictor of poor outcomes in patients with acute myocardial infarction (AMI). AMI complicated by diabetes mellitus (DM) tends to have a high prevalence and a worse prognosis. We aim to evaluate the association between thyroid dysfunction and in-hospital outcomes and short- and medium-term mortality in diabetic patients with AMI.

METHODS

From January 2017 to November 2020, a total of 432 patients with AMI were included in this study, including 209 DM patients and 223 non-DM patients. Baseline characteristics, medical history, and laboratory parameters of patients were recorded after admission. In-hospital outcomes and 30-day mortality were recorded, and long-term mortality was recorded with a median follow-up of 34.2 ± 5.6 months.

RESULTS

Subclinical hypothyroidism (SCH) was defined as an elevated TSH level of more than with a normal range of circulating thyroid hormones. In AMI with DM group, 26/209 (12.4%) patients were complicated with SCH, these patients tend to be older and experienced worse in-hospital outcomes compared to patients without SCH, including higher rates of acute heart failure, acute kidney injury, and atrial fibrillation. Moreover, patients with SCH had a higher prevalence of 30-day mortality and long-term mortality, compared with patients without SCH.

CONCLUSIONS

Diabetic AMI patients with SCH had worse in-hospital outcomes and higher 30-day and long-term mortality. Patients with diabetic AMI should pay attention to thyroid function, and SCH is an independent risk factor for short-term and long-term mortality in diabetic AMI patients.

Thymoquinone improved redox homeostasis in the heart and aorta of hypothyroid rats

OBJECTIVES

Propylthiouracil (PTU) is a common drug that is used in medicine for treating hyperthyroidism. Furthermore, hypothyroidism can also be induced with PTU. Considering the antioxidant effects of thymoquinone (TMQ), this study was designed to find out whether TMQ could counteract the oxidative damage in the heart and aorta tissues induced by hypothyroidism in rats.

METHODS

Animals were arranged into four groups: (1) Control, (2) PTU, (3) PTU-TMQ 5, and (4) PTU-TMQ 10. Hypothyroidism was induced in rats by giving 0.05% PTU in drinking water. PTU and TMQ (5 and 10 mg/kg, ip) treatments were done for 42 days. Finally, the animals were sacrificed and the serum of the rats was collected for thyroxine level assessment. The heart and aorta tissues were also removed for biochemical oxidative stress markers measurement.

RESULTS

A lower serum thyroxine level was observed after PTU treatment compared to the control group. Hypothyroidism also was accompanied by a decrease of thiol content, and superoxide dismutase (SOD), and catalase (CAT) activities in the heart and aorta tissues while increased malondialdehyde (MDA). Furthermore, a significant reduction in oxidative damage was noted in the heart and aorta following the administration of TMQ (5 and 10 mg/kg) which was indicated by the reduction in MDA and improved activities of SOD, CAT, and thiol.

CONCLUSION

In this study, TMQ was found to improve oxidative damages in the heart and aorta tissues of hypothyroid rats.

Cardiovascular protective effects of PPARγ agonists in hypothyroid rats: protection against oxidative stress

Hypothyroidism disturbs redox homeostasis and takes part in cardiovascular system dysfunction. Considering antioxidant and cardio-protective effects of PPAR-γ agonists including pioglitazone (POG) and rosiglitazone (RSG), the present study was aimed to determine the effect of POG or RSG on oxidants and antioxidants indexes in the heart and aorta tissues of Propylthiouracil (PTU)-induced hypothyroid rats.

MATERIALS AND METHODS

The animals were divided into six groups: (1) Control; (2) propylthiouracil (PTU), (3) PTU-POG 10, (4) PTU-POG 20, (5) PTU-RSG 2, and (6) PTU-RSG 4. Hypothyroidism was induced in rats by giving 0.05% propylthiouracil (PTU) in drinking water for 42 days. The rats of PTU-POG 10 and PTU-POG 20 groups received 10 and 20 mg/kg POG, respectively, besides PTU, and the rats of PTU-RSG 2 and PTU-RSG 4 groups received 2 and 4 mg/kg RSG, respectively, besides PTU. The animals were sacrificed, and the serum of the rats was collected to measure thyroxine level. The heart and aorta tissues were also removed for the measurement of biochemical oxidative stress markers.

RESULTS

Hypothyroidism was induced by PTU administration, which was indicated by lower serum thyroxine levels. Hypothyroidism also was accompanied by a decrease of catalase (CAT), superoxide dismutase (SOD) activities, and thiol concentration in the heart and aorta tissues while increased level of malondialdehyde (MDA). Interestingly, administration of POG or RSG dramatically reduced oxidative damage in the heart and aorta, as reflected by a decrease in MDA and increased activities of SOD, CAT, and thiol content.

CONCLUSION

The results of this study showed that administration of POG or RSG decreased oxidative damage in the heart and aorta tissues induced by hypothyroidism in rats.

The bidirectional relationship of thyroid disease and atrial fibrillation: Established knowledge and future considerations

Atrial fibrillation (AF) tends to occur frequently in patients with thyroid disease, primarily hyperthyroidism. In hyperthyroidism, increased levels of thyroid hormones, via intra- and extranuclear mechanisms, have profound effects on cardiac electrophysiology. Hypothyroidism carries a lower risk for AF and is mainly associated with the overtreatment of hypothyroid patients. New-onset AF is frequently the only manifestation of thyroid disease, which renders screening for thyroid dysfunction in that scenario clinically useful. Managing thyroid disease and comorbid AF is essential. This includes thyroid hormones control along with conventional AF therapy. However, there are several open issues with this comorbid duo. The optimal management of thyroid disease and its impact on AF burden remains obscure. There is scanty information on clear-cut benefits for therapy of subclinical thyroid disease and screening of asymptomatic patients. Furthermore, the immunogenetic overlap between the autoantibodies in Graves' disease and AF genesis may lead to novel therapeutic implications. The objective of this review is to summarize the up-to-date epidemiology, pathogenesis, pathophysiology and management of interacting thyroid disease and AF.

New aspects of endocrine control of atrial fibrillation and possibilities for clinical translation

Hormones are potent endo-, para-, and autocrine endogenous regulators of the function of multiple organs, including the heart. Endocrine dysfunction promotes a number of cardiovascular diseases, including atrial fibrillation (AF). While the heart is a target for endocrine regulation, it is also an active endocrine organ itself, secreting a number of important bioactive hormones that convey significant endocrine effects, but also through para-/autocrine actions, actively participate in cardiac self-regulation. The hormones regulating heart-function work in concert to support myocardial performance. AF is a serious clinical problem associated with increased morbidity and mortality, mainly due to stroke and heart failure. Current therapies for AF remain inadequate. AF is characterized by altered atrial function and structure, including electrical and profibrotic remodelling in the atria and ventricles, which facilitates AF progression and hampers its treatment. Although features of this remodelling are well-established and its mechanisms are partly understood, important pathways pertinent to AF arrhythmogenesis are still unidentified. The discovery of these missing pathways has the potential to lead to therapeutic breakthroughs. Endocrine dysfunction is well-recognized to lead to AF. In this review, we discuss endocrine and cardiocrine signalling systems that directly, or as a consequence of an underlying cardiac pathology, contribute to AF pathogenesis. More specifically, we consider the roles of products from the hypothalamic-pituitary axis, the adrenal glands, adipose tissue, the renin–angiotensin system, atrial cardiomyocytes, and the thyroid gland in controlling atrial electrical and structural properties. The influence of endocrine/paracrine dysfunction on AF risk and mechanisms is evaluated and discussed. We focus on the most recent findings and reflect on the potential of translating them into clinical application.

Should cardiac surgery be delayed in patients with uncorrected hypothyroidism?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: 'should cardiac surgery be delayed in patients with uncorrected hypothyroidism?' A total of 1412 papers were found using the reported search, of which 7 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. There was limited high-quality evidence with the majority of the studies being retrospective. One propensity-matched analysis and 6 cohort studies provided the evidence that there was no significant difference in the rate of major adverse cardiac events including mortality based on thyroid status. However, hypothyroidism and subclinical hypothyroidism were associated with higher rates of postoperative atrial fibrillation. Based on the available evidence, we conclude that cardiac surgery should not be delayed to allow achievement of euthyroid status.

Head and neck radiotherapy - A risk factor for anaesthesia?

BACKGROUND

The aim was to study perioperative management in head and neck cancer, the commonest cancer in Indian men, after radiation therapy. Radiotherapy (RT) targets the tumour and the neck including the thyroid gland. RT induced physical effects (on the airway) and physiological effects (on the thyroid) impact perioperative care. Patients with RT-induced subclinical and mild clinical hypothyroidism are often asymptomatic. Cancer surgery is time-sensitive. Given that parenteral levothyroxine is not available, is a TSH of 15 acceptable for cancer surgery?

METHODS

A retrospective study was conducted in a tertiary cancer centre. The records of elective surgery (72 patients) were scrutinised. Data on thyroid profile, airway, treatment of clinical and subclinical hypothyroidism, airway access, recovery and perioperative haemodynamic parameters were retrieved. Correlation of age, sex, RT, chemotherapy with hypothyroidism was done by Chi-square test. The perioperative course was studied.

RESULTS

Hypothyroidism (subclinical and clinical) was diagnosed in 39% of patients. All were asymptomatic. There was a significant association between RT and hypothyroidism. In 50% of patients, we encountered a difficult airway. In subclinical hypothyroidism (TSH less than 15), after levothyroxine initiation, the course of anaesthesia, extubation, recovery and postoperative stay was uneventful.

CONCLUSIONS

Hypothyroidism and difficult airways are a common sequel of RT. Selected cancer patients with subclinical hypothyroidism had a smooth perioperative course.

Subclinical Hypothyroidism Affects the Long-Term Outcomes of Patients Who Undergo Coronary Artery Bypass Grafting Surgery but Not Heart Valve Surgery

BACKGROUND

The aim of this study was to determine the associations between subclinical hypothyroidism (SCH) and long-term cardiovascular outcomes after coronary artery bypass grafting (CABG) or heart valve surgery (HVS).

METHODS

We retrospectively reviewed and compared all-cause mortality, cardiovascular mortality, and cardiovascular events in 461 patients who underwent CABG and 104 patients who underwent HVS.

RESULTS

During a mean±standard deviation follow-up duration of 7.6±3.8 years, there were 187 all-cause deaths, 97 cardiovascular deaths, 127 major adverse cardiovascular events (MACE), 11 myocardial infarctions, one unstable angina, 70 strokes, 30 hospitalizations due to heart failure, 101 atrial fibrillation, and 33 coronary revascularizations. The incidence of all-cause mortality after CABG was significantly higher in patients with SCH (n=36, 55.4%) than in euthyroid patients (n=120, 30.3%), with a hazard ratio of 1.70 (95% confidence interval, 1.10 to 2.63; P=0.018) after adjustment for age, sex, current smoking status, body mass index, underlying diseases, left ventricular dysfunction, and emergency operation. Interestingly, low total triiodothyronine (T3) levels in euthyroid patients who underwent CABG were significantly associated with increased risks of all-cause mortality, cardiovascular mortality, and MACE, but those associations were not observed in HVS patients. Both free thyroxine and thyroid-stimulating hormone levels in euthyroid patients were not related with any cardiovascular outcomes in either the CABG or HVS group.

CONCLUSION

SCH or low total T3 might be associated with a poor prognosis after CABG, but not after HVS, implying that preoperative thyroid hormonal status may be important in ischemic heart disease patients.

Impact of Hypothyroidism on Echocardiographic Characteristics of Patients With Heart Valve Disease: A Single-Center Propensity Score-Based Study

Background: Hypothyroidism is known to be correlated with multiple heart diseases. However, the influence of hypothyroidism on the patients with heart valve disease (HVD) is still unclear. The purpose of our study was to investigate the impact of hypothyroidism on echocardiographic characteristics of patients with heart valve disease. Methods: We conducted a retrospective cohort study which included 2,128 patients with HVD, and they were divided into euthyroid, subclinical hypothyroidism (SCHypoT), and overt hypothyroidism (OHypoT) group. Echocardiographic characteristics before and after valve surgery between groups were compared by using propensity score (PS) analysis. Kaplan-Meier analysis was used to compare the percent of recovery of left atrial (LA) enlargement between groups. Results: Overall, 463 patients had hypothyroidism (404 SCHypoT patients and 59 OHypoT patients), and 1,665 patients were euthyroid. At baseline, hypothyroidism was associated with significantly higher left atrial diameter (LAD), interventricular septum thickness, left ventricular posterior wall thickness, pulmonary artery systolic pressure, and lower left ventricular ejection fraction. After valve surgery, only LAD remained significantly higher in the patients with hypothyroidism. Additionally, patients with hypothyroidism had a significantly lower recovery rate of LA enlargement after valve surgery compared with euthyroid patients. Conclusion: Hypothyroidism was associated with a larger LAD in patients with HVD before and after surgery, which may suggest that hypothyroidism is a risk factor of LA enlargement of HVD. Besides, hypothyroidism was associated with a significantly lower recovery rate of LA enlargement after valve surgery.

Predictors of Atrial Fibrillation in Patients With Cryptogenic Stroke

Background and Purpose

Many patients diagnosed with cryptogenic stroke or transient ischemic attack are subsequently found to have atrial fibrillation (AF) on outpatient cardiac telemetry monitoring. Identification of predictive factors for the detection of AF could assist with patient selection to increase the yield of telemetry and hasten initiation of appropriate secondary stroke prevention.

Methods

This was a retrospective cross-sectional study of patients diagnosed with cryptogenic stroke at a comprehensive stroke center and referred for at least 21 days of prolonged outpatient telemetry. Telemetry reports and data from the patient's stroke hospitalization, including imaging studies, electrocardiogram (EKG), echocardiogram, vital signs, and laboratory data, were reviewed.

Results

Ten percent of the 121 patients included in the study were diagnosed with AF based on outpatient telemetry. There was a strong association between presence of premature atrial contractions (PACs) on admission EKG and subsequent detection of AF (P = .004). Large left atrial diameter on echocardiogram was correlated with AF detection in males (P = .024). However, there was no association between AF and other echocardiographic measurements. Thyroid-stimulating hormone (TSH) levels were significantly higher in patients with cryptogenic stroke having AF (P = .008), with a TSH greater than 4.20 mIU/L predictive of detection of AF (P < .001).

Conclusions

Atrial fibrillation was found by outpatient monitoring in a notable percentage of patients with cryptogenic stroke. Predictors of occult AF in our study population included PACs and higher TSH levels. Although an association between low TSH and AF has been well established, our results suggest that high TSH may be a predictive factor as well.

Effect of Thyroxin Treatment on Carotid Intima-Media Thickness (CIMT) Reduction in Patients with Subclinical Hypothyroidism (SCH): a Meta-Analysis of Clinical Trials

Aim: Research shows that subclinical hypothyroidism (SCH) is related to an increased carotid intima –media thickness (CIMT), a surrogate marker of subclinical cardiovascular disease (CVD). It is controversial whether or not SCH should be treated to reduce CVD morbidity and mortality. This meta-analysis aimed to determine whether SCH is associated with an increase in CIMT as compared to Euthyroidism (EU) and whether thyroxin (T4) treatment in SCH can reverse the change in CIMT.

Methods: Two independent reviewers conducted an extensive database research up to December 2016. A total of 12 clinical trials discussed the effect of Thyroxin on CIMT values at pre- and post-treatment in subjects with SCH.

Results: CIMT was significantly higher among SCH (n = 280) as compared to EU controls (n = 263) at baseline; the pooled weighted mean difference (WMD) of CIMT was 0.44 mm [95% confidence interval (CI) 0.14, 0.74], p = 0.004; I² = 65%. After treatment with thyroxin in subjects with SCH (n = 314), there was a statistically significant decrease in CIMT from pre- to post-treatment; the pooled WMD of CIMT decrease was [WMD −0.32; 95% CI (−0.47, −0.16), p = < 0.0001; I² = 2%], and it was no longer different from EU controls [WMD 0.13 mm; 95% CI (−0.04, 0.30); p = 0.14; I² = 27%]. The total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL) were higher in SCH as compared to EU controls and decreased significantly after treatment with thyroxin.

Conclusion: This meta-analysis shows that thyroxin therapy in subjects with SCH significantly decreases CIMT and improves lipid profile, modifiable CVD risk factors. Thyroid hormone replacement in subjects with SCH may play a role in slowing down or preventing the progression of atherosclerosis.

Risk of Atrial Fibrillation or Flutter Associated with Periodontitis: A Nationwide, Population-Based, Cohort Study

OBJECTIVE

To investigate the risk of atrial fibrillation or atrial flutter in patients with periodontitis (PD) in comparison with individuals without PD.

METHODS

We used the 1999-2010 Taiwanese National Health Insurance Research Database to identify cases of PD in the year 2000 matching (1:1) with persons without PD during 1999-2000 according to sex and individual age as the control group. Using Cox proportional regression analysis adjusting for potential confounders, including age, sex, and comorbidities at baseline, and average annual number of ambulatory visits and dental scaling frequency during the follow-up period, we estimated hazard ratios (HRs) with 95% confidence intervals (CIs) to examine the risk of atrial fibrillation or flutter in PD patients in comparison with the control group. Subgroup analyses according to age, gender, or comorbidities were conducted to study the robustness of the association and investigate possible interaction effects.

RESULTS

We enrolled 393,745 patients with PD and 393,745 non-PD individuals. The incidence rates of atrial fibrillation or flutter were 200 per 105 years among the PD group and 181 per 105 years in the non-PD group (incidence rate ratio, 1.10; 95% CI, 1.06-1.14). After adjusting for potential confounders, we found an increased risk of atrial fibrillation or flutter in the PD group compared with the non-PD group (HR, 1.31; 95% CI, 1.25-1.36). The greater risk of atrial fibrillation or flutter in the PD group remained significant across all disease subgroups except hyperthyroidism and sleep apnea.

CONCLUSION

The present study results indicate an increased risk of atrial fibrillation or flutter in patients with PD. Lack of individual information about alcohol consumption, obesity, and tobacco use was a major limitation.