Abnormal left ventricular function in hyperthyroidism: evidence for a possible reversible cardiomyopathy

Cardio-Thyrotoxicosis Syndrome: A Review of Thyrotoxic Cardiovascular Disease

Thyrotoxicosis, an endocrine disorder characterized by elevated serum thyroid hormone levels of tri-iodothyronine (T3) and/or thyroxine (T4), can impact cardiovascular health in several ways. The cardiovascular system is often severely targeted by the thyrotoxic state, and the term "Cardio-thyrotoxic syndrome" has been proposed to encompass the various cardiovascular disease states resulting from thyrotoxicosis. In this review, we discuss various cardiovascular disorders resulting from the effects of thyrotoxicosis. It is important to keep a high index of suspicion for thyroid disorder in the setting of new atrial fibrillation, heart failure, and tachycardia-induced cardiomyopathy. Management of cardio-thyrotoxicosis involves control of heart rate and blood pressure and treatment of acute cardiovascular complications. Thyroid-specific therapy to achieve a euthyroid state will not only improve but even potentially reverse cardiovascular abnormalities.

Thyrotoxicosis-Induced Cardiogenic Shock: Acute Management Using a Multidisciplinary Approach

The development of heart failure and cardiomyopathy has been identified as an infrequent but life-threatening complication of thyrotoxicosis or thyroid storm. Thyrotoxicosis-induced cardiomyopathy and cardiogenic shock have been shown to be one of the major causes of sudden mortality in adults. However, the treatment of thyrotoxicosis with non-cardioselective beta-blockers has been implicated in the development of severe decompensation and even cardiogenic shock if cardiac function is not known and often requires a multidisciplinary care team to address it. Here, we have reported the case of a 63-year-old male with a past medical history of hyperthyroidism who presented to the emergency room with persistent shortness of breath. Vital signs were notable for hypotension, tachycardia with an irregular heartbeat, with ECG suggestive of atrial fibrillation with a rapid ventricular rate. The thyroid function test was significant for severely suppressed TSH, and the Burch-Wartofsky Score was >45. The patient rapidly decompensated shortly after being given IV metoprolol, subsequently requiring intubation and pressor support. Two-dimensional (2D) echocardiography (or echo) done afterward was significant for four-chamber dilation with mild global hypokinesis and reduced left ventricular ejection fraction. Endocrinology, Cardiology, and Pulmonary Critical Care teams were consulted to assist in multi-modality management. The administration of a non-cardioselective beta-blocker in decompensated heart failure was suggested as the cause of the rapid deterioration. Through a multi-modality management approach, the patient subsequently improved and was eventually discharged with the resolution of thyroid storm and cardiogenic shock, and with close follow-up with the primary care provider, endocrinologist, and cardiologist. This case illustrates the significance of a multidisciplinary team approach in the acute management of thyrotoxicosis-induced cardiogenic shock, as recommendations from the team were instrumental in helping the patient recover from the acute phase of the illness. Also, this case further highlights the significance of assessing the cardiac function, preferably performing echo before starting the patient on beta-blockers.

Cardiovascular Collapse Secondary to Beta-Blocker Administration in a Setting of Coexisting Thyroid Storm and Atrial Fibrillation: A Case Report

A thyroid storm is a rare endocrinological emergency caused by severe hyperthyroidism. Reducing circulating levels of free T3 in blood and beta-adrenergic inhibition are the basis of medical treatment for thyroid storms. Propranolol, due to its additional effect of preventing the peripheral conversion of dormant T4 to active form T3, is the chosen drug for blockade in hyperthyroidism and thyroid storm. We describe a rare clinical case of cardiovascular collapse following propranolol administration in a setting of thyroid storm. The patient presented with symptoms of dyspnea and palpitations and had an ejection fraction of 10%. He was started on a calcium channel blocker (diltiazem). Further investigations revealed that the patient also had a thyroid storm and was immediately shifted to methimazole and propranolol. However, following the administration of a beta-blocker, the patient developed circulatory failure as a result of cardiac arrest, necessitating the use of vasopressors and inotropes. This implores the need for further investigations and treatment regimens for cardiovascular conditions, especially atrial fibrillation arising in thyrotoxicosis, as there are no solid treatment guides in the literature to the best of our knowledge.

Thyroid Storm Patients With Elevated Brain Natriuretic Peptide Levels and Associated Left Ventricular Dilatation May Require Percutaneous Mechanical Support

OBJECTIVES

To determine the characteristics of thyroid storm patients with acute decompensated heart failure who should be candidates for temporary percutaneous mechanical circulatory support in addition to beta-blocker treatment to prevent cardiogenic shock.

DESIGN

A single-center, retrospective review of treatment details and data collected from electronic medical records.

SETTING

Thyrotoxicosis complicated with acute decompensated heart failure.

PATIENTS

Eight consecutive patients who were admitted to our hospital for acute decompensated heart failure with thyroid storm between December 2011 and August 2020 were retrospectively reviewed. Of the eight patients, four were treated with percutaneous mechanical circulatory support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Compared with thyroid storm patients who did not require percutaneous mechanical circulatory support, those who did had a significantly higher initial plasma brain natriuretic peptide level (1,231 [911-3,387] vs 447 pg/mL [243-653 pg/mL], respectively; p = 0.015), as well as a significantly larger left ventricular end-diastolic diameter (56 [54-63] vs 48 mm [38-48 mm], respectively; p = 0.029) and end-systolic diameter (50 [49-58] vs 28 mm [28-30 mm], respectively; p = 0.029) on echocardiogram. In terms of thyroid storm severity, the Burch-Wartofsky score was higher in patients with percutaneous mechanical circulatory support than in those without, although the difference was not significant. All patients survived this index admission.

CONCLUSIONS

In thyroid storm patients, the presence of a high brain natriuretic peptide level, "left ventricular dilatation," or both may necessitate hemodynamic assessment to determine the indication of percutaneous mechanical circulatory support before beta-blocker administration.

Thyroid Hormone Plays an Important Role in Cardiac Function: From Bench to Bedside

Thyroid hormones (THs) are synthesized in the thyroid gland, and they circulate in the blood to regulate cells, tissues, and organs in the body. In particular, they exert several effects on the cardiovascular system. It is well known that THs raise the heart rate and cardiac contractility, improve the systolic and diastolic function of the heart, and decrease systemic vascular resistance. In the past 30 years, some researchers have studied the molecular pathways that mediate the role of TH in the cardiovascular system, to better understand its mechanisms of action. Two types of mechanisms, which are genomic and non-genomic pathways, underlie the effects of THs on cardiomyocytes. In this review, we summarize the current knowledge of the action of THs in the cardiac function, the clinical manifestation and parameters of their hemodynamics, and treatment principles for patients with hyperthyroid- or hypothyroid-associated heart disease. We also describe the cardiovascular drugs that induce thyroid dysfunction and explain the mechanism underlying the thyroid toxicity of amiodarone, which is considered the most effective antiarrhythmic agent. Finally, we discuss the recent reports on the involvement of thyroid hormones in the regulation of myocardial regeneration and metabolism in the adult heart.

Incidence, risk factors, natural history and outcomes of heart failure in patients with Graves' disease

OBJECTIVE

Graves' disease (GD) can both aggravate pre-existing cardiac disease and cause de novo heart failure (HF), but large-scale studies are lacking. We aimed to investigate the incidence, risk factors and outcomes of incident GD-related HF.

METHODS

Patients with GD (2009-2019) were retrospectively included. HF with reduced ejection fraction (HFrEF) was defined by left ventricular ejection fraction <50% and Framingham criteria, while HF with preserved ejection fraction (HFpEF) was defined according to the HFA-PEFF criteria. HF due to ischaemia, valve disorder or other structural heart disease was excluded. Proportional hazards regression was used to analyse risk factors and outcomes.

RESULTS

Of 1371 patients with GD, HF occurred in 74 (5.4%) patients (31 (2.3%) HFrEF; 43 (3.1%) HFpEF). In HFrEF, atrial fibrillation (AF) (HR 10.5 (3.0-37.3), p<0.001) and thyrotropin receptor antibody (TRAb) level (HR 1.05 (1.01-1.09) per unit, p=0.007) were independent risk factors. In HFpEF, the independent risk factors were chronic obstructive pulmonary disease (HR 7.2 (3.5-14.6), p<0.001), older age (HR 1.5 (1.2-2.0) per 10 years, p=0.001), overt hyperthyroidism (HR 6.4 (1.5-27.1), p=0.01), higher body mass index (BMI) (HR 1.07 (1.03-1.10) per unit, p=0.001) and hypertension (HR 3.1 (1.3-7.2), p=0.008). The risk of cardiovascular hospitalisations was higher in both HFrEF (HR 10.3 (5.5-19.4), p<0.001) and HFpEF (HR 6.7 (3.7-12.2), p<0.001). However, only HFrEF was associated with an increased risk of all-cause mortality (HR 5.17 (1.3-19.9), p=0.02) and ventricular tachycardia/fibrillation (HR 64.3 (15.9-259.7), p<0.001).

CONCLUSION

De novo HF occurs in 5.4% of patients with GD and is associated with increased risk of cardiovascular hospitalisations and mortality. Risk factors include AF, higher TRAb, higher BMI and overt hyperthyroidism.

Is There Any Relationship between TSH Levels and Prognosis in Acute Coronary Syndrome?

Background

Some small studies have related higher levels of thyrotropin (TSH) to potentially worse prognosis in acute coronary syndromes. However, this relationship remains uncertain.

Objective

To analyze the outcomes of patients with acute coronary syndromes in relation to the value of TSH at admission.

Methods

Observational and retrospective study with 505 patients (446 in group I [TSH ≤ 4 mIU/L] and 59 in group II [TSH > 4 mIU/L]) with acute coronary syndromes between May 2010 and May 2014. We obtained data about comorbidities and the medications used at the hospital. The primary endpoint was in-hospital all-cause death. The secondary endpoint included combined events (death, non-fatal unstable angina or myocardial infarction, cardiogenic shock, bleeding and stroke). Comparisons between groups were made by one-way ANOVA and chi-square test. Multivariate analysis was determined by logistic regression. Analyses were considered significant when p < 0.05.

Results

Significant differences between groups I and II were observed regarding the use of enoxaparin (75.2% vs. 57.63%, p = 0.02) and statins (84.08% vs. 71.19%, p < 0.0001), previous stroke (5.83% vs. 15.25%, p = 0.007), combined events (14.80% vs. 27.12%, OR = 3.05, p = 0.004), cardiogenic shock (4.77% vs. 6.05%, OR = 4.77, p = 0.02) and bleeding (12.09% vs. 15.25%, OR = 3.36, p = 0.012).

Conclusions

In patients with acute coronary syndromes and TSH > 4 mIU/L at admission, worse prognosis was observed, with higher incidences of in-hospital combined events, cardiogenic shock and bleeding.

Propranolol-Induced Circulatory Collapse in a Patient With Thyroid Crisis and Underlying Thyrocardiac Disease: A Word of Caution

Thyrotoxic crisis or thyroid storm is a severe form of hyperthyroidism and a rare endocrinological emergency. The cornerstones of medical therapy in thyroid storm include decreasing the levels of circulating T3 in the blood as well as inhibiting the hormone's peripheral effects through β-adrenergic blockade. Propranolol is the preferred agent for β-blockade in hyperthyroidism and thyroid storm due to its additional effect of blocking the peripheral conversion of inactive T4 to active form T3. We report a typical clinical scenario where propranolol was administered in treatment of thyroid storm but an uncommon adverse outcome: circulatory failure from cardiogenic shock warranting vasopressor and inotropic support. Caution with regard to the use long-acting β-blocking agents in patients with underling thyrocardiac disease may prevent this life-threatening adverse effect. Ultra-short-acting β-blockers that are easy to titrate maybe a suitable alternative in this subset of patients.

Dysthyroidism and Chronic Heart Failure: Pathophysiological Mechanisms and Therapeutic Approaches

Among comorbidity in chronic heart failure (CHF), dysthyroidism represents a relevant problem especially in the ageing CHF patients worldwide. Thyroid greatly affects many cardiovascular activities and its dysfunction may worsen a CHF condition. In particular, hypothyroidism has a relative high prevalence in patients with heart failure and it plays a key role in influencing CHF onset, progression and prognosis. Hyperthyroidism, is less frequent in this clinical context but it necessitates of immediate treatment because of its negative effects on cardiovascular balance. Also, it must be considered that dysthyroism may also be iatrogenic and the main responsible drug is Amiodarone.Based on the best available evidence and our cumulative clinical experience, this manuscript analyzes the prevalence, the pathophysiology and the prognostic impact of thyroid disorders in chronic heart failure.

The IGF1-PI3K-Akt Signaling Pathway in Mediating Exercise-Induced Cardiac Hypertrophy and Protection

Regular physical activity or exercise training can lead to heart enlargement known as cardiac hypertrophy. Cardiac hypertrophy is broadly defined as an increase in heart mass. In adults, cardiac hypertrophy is often considered a poor prognostic sign because it often progresses to heart failure. Heart enlargement in a setting of cardiac disease is referred to as pathological cardiac hypertrophy and is typically characterized by cell death and depressed cardiac function. By contrast, physiological cardiac hypertrophy, as occurs in response to chronic exercise training (i.e. the 'athlete's heart'), is associated with normal or enhanced cardiac function. The following chapter describes the morphologically distinct types of heart growth, and the key role of the insulin-like growth factor 1 (IGF1) - phosphoinositide 3-kinase (PI3K)-Akt signaling pathway in regulating exercise-induced physiological cardiac hypertrophy and cardiac protection. Finally we summarize therapeutic approaches that target the IGF1-PI3K-Akt signaling pathway which are showing promise in preclinical models of heart disease.

Thyroid Storm with Heart Failure Treated with a Short-acting Beta-adrenoreceptor Blocker, Landiolol Hydrochloride

Beta-adrenoreceptor blockers are essential in controlling the peripheral actions of thyroid hormones and a rapid heart rate in patients with thyroid storm, although they should be used with great caution when there is the potential for heart failure. A 67-year-old woman was diagnosed as having thyroid storm in addition to marked tachycardia with atrial fibrillation and heart failure associated with a reduced left ventricular function. The administration of an oral beta blocker, bisoprolol fumarate, induced hypotension and was not tolerable for the patient, whereas landiolol hydrochloride, a short-acting intravenous beta-adrenoreceptor blocker with high cardioselectivity and a short elimination half-life, was useful for controlling the patient's tachycardia and heart failure without causing hemodynamic deterioration.

Graves' disease presenting as bi-ventricular heart failure with severe pulmonary hypertension and pre-eclampsia in pregnancy--a case report and review of the literature

Background

Graves’ disease, a well-known cause of hyperthyroidism, is an autoimmune disease with multi-system involvement. More prevalent among young women, it appears as an uncommon cardiovascular complication during pregnancy, posing a diagnostic challenge, largely owing to difficulty in detecting the complication, as a result of a low index of suspicion of Graves’ disease presenting during pregnancy. Globally, cardiovascular disease is an important factor for pregnancy-related morbidity and mortality. Here, we report a case of Graves’ disease detected for the first time in pregnancy, in a patient presenting with bi- ventricular heart failure, severe pulmonary hypertension and pre- eclampsia. Emphasis is placed on the spectrum of clinical presentations of Graves’ disease, and the importance of considering this thyroid disorder as a possible aetiological factor for such a presentation in pregnancy.

Case presentation

A 30-year-old Bangladeshi-Bengali woman, in her 28th week of pregnancy presented with severe systemic hypertension, bi-ventricular heart failure and severe pulmonary hypertension with a moderately enlarged thyroid gland. She improved following the administration of high dose intravenous diuretics, and delivered a premature female baby of low birth weight per vaginally, twenty four hours later. Pre-eclampsia was diagnosed on the basis of hypertension first detected in the third trimester, 3+ oedema and mild proteinuria. Electrocardiography revealed sinus tachycardia with incomplete right bundle branch block and echocardiography showed severe pulmonary hypertension with an estimated pulmonary arterial systolic pressure of 73 mm Hg, septal and anterior wall hypokinesia with an ejection fraction of 51%, grade I mitral and tricuspid regurgitation. Thyroid function tests revealed a biochemically hyperthyroid state and positive anti- thyroid peroxidase antibodies was found. ^99mTechnetium pertechnetate thyroid scans demonstrated diffuse toxic goiter as evidenced by an enlarged thyroid gland with intense radiotracer concentration all over the gland. The clinical and biochemical findings confirmed the diagnosis of Graves’ disease.

Conclusions

Graves’ disease is an uncommon cause of bi-ventricular heart failure and severe pulmonary hypertension in pregnancy, and a high index of clinical suspicion is paramount to its effective diagnosis and treatment.

Hyperthyroidism and thyrotoxicosis

Hyperthyroidism and thyrotoxicosis are hypermetabolic conditions that cause significant morbidity and mortality. The diagnosis can be difficult because symptoms can mimic many other disease states leading to inaccurate or untimely diagnoses and management. Thyroid storm is the most severe form of thyrotoxicosis, hallmarked by altered sensorium, and, if untreated, is associated with significant mortality. Thyroid storm should be considered in the differential of any patient presenting with altered mental status. The emergency medicine physician who can rapidly recognize thyrotoxicosis, identify the precipitating event, appropriately and comprehensively begin medical management, and facilitate disposition will undoubtedly save a life.

Pitting type of pretibial edema in a patient with silent thyroiditis successfully treated by angiotensin II receptor blockade

Patient: Female, 56

Final Diagnosis: Thyroiditis – silent

Symptoms: Palpitations • pretibial pitting edema • short of breath • sweating

Medication: —

Clinical Procedure: —

Specialty: Endocrinology and Metabolic

Graves' thyrotoxicosis-induced reversible cardiomyopathy: a case report

The objective of this report is to present a case of Graves' thyrotoxicosis-induced cardiomyopathy. This is a case of a 26 year old woman that presented with severe symptomatic congestive heart failure and was subsequently diagnosed with dilated cardiomyopathy secondary to Graves' disease. Despite an initial left ventricular systolic ejection fraction of 20% on echocardiography, treatment with anti-thyroid agents led to rapid improvement of her clinical status and normalization of her ejection fraction. The proposed mechanisms underlying the development of systolic dysfunction in thyrotoxicosis are discussed and the literature on similar cases previously reported is highlighted. Cardiomyopathy should be considered even in young patients with Graves' thyrotoxicosis.

Mechanisms in endocrinology: Heart failure and thyroid dysfunction

CONTEXT

Heart failure (HF) is a major cause of morbidity and mortality in Europe and in the United States. The aim of this review article was to assess the results of the prospective studies that evaluated the risk of HF in patients with overt and subclinical thyroid disease and discuss the mechanism of this dysfunction.

EVIDENCE ACQUISITION

Reports published with the following search terms were searched:, thyroid, hypothyroidism, hyperthyroidism, subclinical hyperthyroidism, subclinical hypothyroidism, levothyroxine, triiodothyronine, antithyroid drugs, radioiodine, deiodinases, clinical symptoms, heart rate, HF, systolic function, diastolic function, systemic vascular resistance, endothelial function, amiodarone and atrial fibrillation. The investigation was restricted to reports published in English.

EVIDENCE SYNTHESIS

The outcome of this analysis suggests that patients with untreated overt thyroid dysfunction are at increased risk of HF. Moreover, persistent subclinical thyroid dysfunction is associated with the development of HF in patients with serum TSH <0.1 or > 10 mU/l.

CONCLUSIONS

The timely recognition and effective treatment of cardiac symptoms in patients with thyroid dysfunction is mandatory because the prognosis of HF may be improved with the appropriate treatment of thyroid dysfunction.

Severe transient left ventricular dysfunction induced by thyrotoxicosis

We report on a 44-year-old woman presenting with chest pain and dyspnoea without previous stress-related events. By means of echocardiography severe left ventricular dysfunction and wall motion abnormalities resembling stress-induced cardiomyopathy (Tako Tsubo) were seen. Laboratory investigation revealed thyrotoxicosis and elevated cardiac markers. Six days after starting medical treatment, complete restoration of the left ventricular function was observed. The transient left ventricular dysfunction was induced by thyrotoxicosis resembling stress-induced cardiomyopathy that resolved completely after medical treatment.

Abnormal cardiac contractility in long-term exogenous subclinical hyperthyroid patients as demonstrated by two-dimensional echocardiography speckle tracking imaging

BACKGROUND

Subclinical hyperthyroidism is associated with cardiovascular morbidity. Recent advances in echocardiography imaging have allowed sophisticated evaluation of myocardial tissue properties.

OBJECTIVE

To investigate the myocardial effects of long-term exogenous subclinical hyperthyroidism using two-dimensional speckle tracking echocardiography imaging (2D-STE).

DESIGN

Prospective, single-blinded, placebo-controlled randomized trial of 6 months duration with two parallel groups.

PATIENTS AND METHODS

Totally 25 patients with a history of differentiated thyroid carcinoma on long-term TSH-suppressive levothyroxine (l-T(4)) substitution were randomized to persistent TSH-suppressive l-T(4) substitution (low-TSH group) or restoration of euthyroidism. Additionally 40 euthyroid controls were studied. RESULTS (PROPOSAL): At baseline, the group of patients showed normal left ventricular (LV) systolic function but impaired diastolic function as assessed with conventional echocardiographic parameters. Importantly, 2D-STE analysis demonstrated the presence of subclinical LV systolic and diastolic dysfunction with impaired circumferential and longitudinal strain and strain rate at the isovolumic relaxation time. After restoration of euthyroidism, a significant improvement in LV systolic and diastolic function as assessed with 2D-STE strain was observed.

CONCLUSION

Prolonged subclinical hyperthyroidism leads to systolic and diastolic dysfunction, which is reversible after restoration of euthyroidism. 2D-STE is a more sensitive technique to evaluate subtle changes in LV performance of these patients.

Cardiovascular involvement in patients with different causes of hyperthyroidism

Various clinical disorders can cause hyperthyroidism, the effects of which vary according to the patient's age, severity of clinical presentation and association with other comorbidities. Hyperthyroidism is associated with increased morbidity and mortality from cardiovascular disease, although whether the risk of specific cardiovascular complications is related to the etiology of hyperthyroidism is unknown. This article will focus on patients with Graves disease, toxic adenoma and toxic multinodular goiter, and will compare the cardiovascular risks associated with these diseases. Patients with toxic multinodular goiter have a higher cardiovascular risk than do patients with Graves disease, although cardiovascular complications in both groups are differentially influenced by the patient's age and the cause of hyperthyroidism. Atrial fibrillation, atrial enlargement and congestive heart failure are important cardiac complications of hyperthyroidism and are prevalent in patients aged > or = 60 years with toxic multinodular goiter, particularly in those with underlying cardiac disease. An increased risk of stroke is common in patients > 65 years of age with atrial fibrillation. Graves disease is linked with autoimmune complications, such as cardiac valve involvement, pulmonary arterial hypertension and specific cardiomyopathy. Consequently, the etiology of hyperthyroidism must be established to enable correct treatment of the disease and the cardiovascular complications.

Molecular distinction between physiological and pathological cardiac hypertrophy: experimental findings and therapeutic strategies

Cardiac hypertrophy can be defined as an increase in heart mass. Pathological cardiac hypertrophy (heart growth that occurs in settings of disease, e.g. hypertension) is a key risk factor for heart failure. Pathological hypertrophy is associated with increased interstitial fibrosis, cell death and cardiac dysfunction. In contrast, physiological cardiac hypertrophy (heart growth that occurs in response to chronic exercise training, i.e. the 'athlete's heart') is reversible and is characterized by normal cardiac morphology (i.e. no fibrosis or apoptosis) and normal or enhanced cardiac function. Given that there are clear functional, structural, metabolic and molecular differences between pathological and physiological hypertrophy, a key question in cardiovascular medicine is whether mechanisms responsible for enhancing function of the athlete's heart can be exploited to benefit patients with pathological hypertrophy and heart failure. This review summarizes key experimental findings that have contributed to our understanding of pathological and physiological heart growth. In particular, we focus on signaling pathways that play a causal role in the development of pathological and physiological hypertrophy. We discuss molecular mechanisms associated with features of cardiac hypertrophy, including protein synthesis, sarcomeric organization, fibrosis, cell death and energy metabolism and provide a summary of profiling studies that have examined genes, microRNAs and proteins that are differentially expressed in models of pathological and physiological hypertrophy. How gender and sex hormones affect cardiac hypertrophy is also discussed. Finally, we explore how knowledge of molecular mechanisms underlying pathological and physiological hypertrophy may influence therapeutic strategies for the treatment of cardiovascular disease and heart failure.

Short-term overt hypothyroidism induces sympathovagal imbalance in thyroidectomized differentiated thyroid carcinoma patients

CONTEXT

Thyroid hormone impacts on the cardiovascular system. (Subclinical) hyperthyroidism results in sympathovagal imbalance due to decreased vagal tone. However, conflicting data have been reported on the effects of hypothyroidism on the activity of the autonomic nervous system (ANS). In hypothyroidism, both increased and decreased sympathetic activity and increased vagal tone have been found.

OBJECTIVE

To study the effects of acute short-term overt hypothyroidism and thyroxine replacement therapy on the ANS by measuring urinary excretion of catecholamines and heart rate variability (HRV).

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

We studied 11 patients, previously treated with thyroidectomy for differentiated thyroid carcinoma, during hypothyroidism caused by cessation of thyroxine substitution for 4 weeks and during thyroxine replacement therapy, and 21 matched healthy controls.

MAIN OUTCOME MEASURES

The activity of the ANS was assessed by measuring urinary excretion of catecholamines and HRV at rest and during a challenge of the ANS by a mental stress test.

RESULTS

Urinary dopamine excretion was significantly lower during hypothyroidism. Although in the patients total variability was unchanged, HRV analysis showed a significantly lower low frequency/high frequency ratio, indicating sympathovagal imbalance with sympathetic withdrawal. The mental stress test in the patients resulted in a significant increase in heart rate to the extent of 16-18%. This response was not different between the hypothyroid state and during thyroxine replacement therapy suggesting that cardiovascular reflexes in these patients remain intact.

CONCLUSION

Acute short-term overt hypothyroidism results in sympathovagal imbalance with sympathetic withdrawal, with preservation of the cardiovascular reflexes to (mental) stress.

How to manage perioperative endocrine insufficiency

Patients with endocrinopathies frequently present to the operating room. Although many of these disorders are managed on a chronic basis, patients may have acute changes in the perioperative period that, if left unrecognized, can have a negative effect on perioperative morbidity and mortality. It is imperative that anesthesiologists understand the implications of the surgical stress response on hormonal flux. This article focuses on the 4 most commonly encountered endocrinopathies: diabetes mellitus, hyperthyroidism, hypothyroidism, and adrenal insufficiency. Specific challenges pertaining to patients with pheochromocytoma are also discussed.

Thyroid storm and lymphocytic myocarditis

Cardiac failure is the leading cause of mortality in patients with thyroid storm. But the underlying cardiac pathology is unclear. Here, we report a 46-year-old woman who presented with hyperpyrexia and sinus tachycardia subsequent to accidental neck contusion. Her hyperthyroidism was verified by abnormal biochemical changes. Despite vigorous antithyroid treatment including a beta-blocker, glucocorticoid and potassium iodide, the patient eventually succumbed to refractory congestive heart failure in 4 days. Autopsy revealed lymphocytic myocarditis. We propose that lymphocytic myocarditis played a prominent role in her demise.

Surgery in the patient with endocrine dysfunction

Patients with preoperative endocrinopathies represent a particular challenge not only to anesthesiologists but also to surgeons and perioperative clinicians. The "endocrine axis" is complex and has multiple feedback loops, some of which are endocrine and paracrine related, and others that are strongly influenced by the surgical stress response. Familiarity with several of the common endocrinopathies facilitates management in the perioperative period. This article focuses on 4 of the most common endocrinopathies: diabetes mellitus, hyperthyroidism, hypothyroidism, and adrenal insufficiency. Perioperative challenges in patients presenting with pheochromocytoma are also discussed.

Surgery in the patient with endocrine dysfunction

Patients with preoperative endocrinopathies represent a particular challenge not only to anesthesiologists but also to surgeons and perioperative clinicians. The "endocrine axis" is complex and has multiple feedback loops, some of which are endocrine and paracrine related, and others that are strongly influenced by the surgical stress response. Familiarity with several of the common endocrinopathies facilitates management in the perioperative period. This article focuses on 4 of the most common endocrinopathies: diabetes mellitus, hyperthyroidism, hypothyroidism, and adrenal insufficiency. Perioperative challenges in patients presenting with pheochromocytoma are also discussed.

Cardiac performance in hyperthyroidism assessed by systolic time intervals and radionuclide ventriculography

Systolic time intervals (STI) and radionuclide ventriculography (RNV) were used in the assessment of cardiac performance in 22 patients with hyperthyroidism before and after antithyroid treatment. STI as well as RNV showed enhanced myocardial contractility which was normalized after antithyroid treatment. Beta-blocker treatment did not influence the hypercontractility in hyperthyroidism. This implies that beta-blockers alone cannot be regarded as satisfactory long-term treatment and that mechanisms other than increased sympathoadrenal drive are involved in the hypercontractility in hyperthyroidism. RNV suggested valvular regurgitation, probably of the mitral valve, in 11 patients. Possible hemodynamic consequences are discussed.

Short-term overt hypothyroidism induces discrete diastolic dysfunction in patients treated for differentiated thyroid carcinoma

BACKGROUND

Thyroid hormone has important effects on the cardiovascular system. The consequences of episodes of acute hypothyroidism on cardiac function have been investigated in only a few studies, and their results are inconclusive. Our objective was to investigate the effects of acute hypothyroidism on cardiac function in patients with iatrogenically induced subclinical hyperthyroidism after treatment for differentiated thyroid carcinoma.

MATERIAL AND METHODS

Fourteen patients with a history of differentiated thyroid carcinoma on thyroid-stimulating hormone (TSH)-suppressive thyroxine replacement therapy were studied. We assessed cardiac function before, and 1 and 4 weeks after withdrawal of thyroxine substitution. We measured serum levels of free thyroxine, triiodothyronine and TSH and used a new sophisticated Doppler echocardiography technique, tissue Doppler imaging (TDI), to assess detailed and quantitative assessment of systolic and diastolic cardiac function. Echocardiographic parameters in patients were compared to controls.

RESULTS

Compared to controls, patients had higher left ventricular mass and wall thickness and decreased diastolic function during TSH-suppressive l-thyroxine substitution therapy. Thyroxine withdrawal resulted in a decrease in both early (E) and late (A) diastolic mitral inflow velocities, without impact on E/A ratio. Using TDI, late diastolic velocity (A') decreased without impact on E'/A' ratio. Left ventricular dimensions, wall thickness and mass did not change during thyroxine withdrawal.

CONCLUSIONS

Subclinical hyperthyroidism is accompanied by diastolic dysfunction. Subsequent acute hypothyroidism induces only subtle changes in diastolic function.

Hyperthyroid heart disease

The heart is an organ sensitive to the action of thyroid hormone, and measurable changes in cardiac performance are detected with small variations in thyroid hormone serum concentrations. Most patients with hyperthyroidism experience cardiovascular manifestations, and the most serious complications of hyperthyroidism occur as a result of cardiac involvement. Recent studies provide important insights into the molecular pathways that mediate the action of thyroid hormone on the heart and allow a better understanding of the mechanisms that underlie the hemodynamic and clinical manifestations of hyperthyroidism. Several cardiovascular conditions and drugs can interfere with thyroid hormone levels and may pose a difficulty in interpretation of laboratory data in patients with suspected thyroid heart disease. The focus of this report is a review of the current knowledge of thyroid hormone action on the heart and the clinical and hemodynamic laboratory findings as well as therapeutic management of patients with hyperthyroid heart disease.

Thyrotoxic cardiac disease

The most recognizable features of hyperthyroidism are those that result from the effects of triiodothyronine (T3) on the heart and cardiovascular system: decreased systemic vascular resistance and increased resting heart rate, left ventricular contractility, blood volume, and cardiac output. Although these measures of cardiac performance are enhanced in hyperthyroidism, the finding of clinical cardiac failure can be somewhat paradoxical. About 6% of thyrotoxic individuals develop symptoms of heart failure, but less than 1% develop dilated -cardiomyopathy with impaired left ventricular systolic function. Heart failure resulting from thyrotoxicosis is due to a tachycardia-mediated mechanism leading to an increased level of cytosolic calcium during diastole with reduced ventricular contractility and diastolic dysfunction, often with tricuspid regurgitation. Pulmonary artery hypertension in thyrotoxicosis is gaining awareness as a cause of isolated right-sided heart failure. In both cases, older individuals are more likely to be affected. Treatment needs to be directed at management of the acute cardiovascular complications, control of the heart rate, and thyroid-specific therapy to restore a euthyroid state that will lead to resolution of the signs and symptoms of heart failure.

Prolonged Ventilation in Thyroid Storm

Thyroid storm (crisis) is uncommon but may be life threatening and is recognised by an exaggeration of the clinical features of thyrotoxicosis. Proximal myopathy is a well recognised presenting feature of Graves disease. Respiratory muscle weakness may also commonly occur in thyrotoxicosis but is often undiagnosed. We report a case of thyroid storm with rapid atrial fibrillation, severe agitation and extreme widespread muscle weakness. The respiratory muscles were so compromised that a respiratory arrest occurred. Ventilation was required for 7 weeks until full recovery occurred.

Hyperthyroidism as a reversible cause of right ventricular overload and congestive heart failure

We describe a case of severe congestive heart failure and right ventricular overload associated with overt hyperthyroidism, completely reversed with antithyroid therapy in a few week. It represents a very unusual presentation of overt hyperthyroidism because of the severity of right heart failure. The impressive right ventricular volume overload made mandatory to perform transesophageal echo and angio-TC examination to exclude the coexistence of ASD or anomalous pulmonary venous return. Only a few cases of reversible right heart failure, with or without pulmonary hypertension, have been reported worldwide. In our case the most striking feature has been the normalization of the cardiovascular findings after six weeks of tiamazole therapy.

Thyroid disease and the heart

The cardiovascular signs and symptoms of thyroid disease are some of the most profound and clinically relevant findings that accompany both hyperthyroidism and hypothyroidism. On the basis of the understanding of the cellular mechanisms of thyroid hormone action on the heart and cardiovascular system, it is possible to explain the changes in cardiac output, cardiac contractility, blood pressure, vascular resistance, and rhythm disturbances that result from thyroid dysfunction. The importance of the recognition of the effects of thyroid disease on the heart also derives from the observation that restoration of normal thyroid function most often reverses the abnormal cardiovascular hemodynamics. In the present review, we discuss the appropriate thyroid function tests to establish a suspected diagnosis as well as the treatment modalities necessary to restore patients to a euthyroid state. We also review the alterations in thyroid hormone metabolism that accompany chronic congestive heart failure and the approach to the management of patients with amiodarone-induced alterations in thyroid function tests.

Thyroid hormone use, hyperthyroidism and mortality in older women

PURPOSE

Thyroid dysfunction is common, particularly among older women. The safety of thyroid hormone use and long-term prognosis of hyperthyroidism remain controversial. We performed a prospective cohort study to examine the relationship among thyroid hormone use, previous hyperthyroidism, abnormal thyroid function, and mortality.

METHODS

We studied 9449 community-dwelling white women aged > or =65 years followed for 12 years. For analyses of thyroid function, we performed a nested case-cohort in 487 women using a third-generation thyroid-stimulating hormone assay. Causes of death were adjudicated based on death certificates and hospital records.

RESULTS

Twelve percent of the 9449 women took thyroid hormone at baseline, and the mean duration of thyroid hormone use was 15.8 years; 9.4% of participants reported a history of hyperthyroidism. During 12 years of follow-up, 3159 women died (33%). In multivariate analysis, mortality among users of thyroid hormone was similar to that observed for nonusers (relative hazard [RH] 1.11, 95% confidence interval [CI], 0.98-1.24, P=.09). Previous hyperthyroidism was associated with a higher risk of all-cause mortality (RH 1.20, 95% CI, 1.06-1.36), particularly cardiovascular mortality (RH 1.46, 95% CI, 1.20-1.77). Low (< or /=0.5 mU/L) or high (>5 mU/L) thyroid-stimulating hormone levels were not associated with excess total or cause-specific mortality, but the power to detect these relationships was limited.

CONCLUSIONS

Among older women, thyroid hormone use is not associated significantly with excess mortality, but previous hyperthyroidism may be associated with a small increase in all-cause and cardiovascular mortality. Additional long-term studies of hyperthyroidism and its treatment should further explore these findings.

Reversible pulmonary hypertension and isolated right-sided heart failure associated with hyperthyroidism

Hyperthyroidism may present with signs and symptoms related to dysfunction of a variety of organs. Cardiovascular pathology in hyperthyroidism is common. A few case reports describe isolated right heart failure, tricuspid regurgitation, and pulmonary hypertension as the prominent cardiovascular manifestations of hyperthyroidism. Although most textbooks do not mention hyperthyroidism as a cause of pulmonary hypertension and isolated right heart failure, the literature suggests that some hyperthyroid patients may develop reversible pulmonary hypertension and isolated right heart failure. We report a case of hyperthyroidism presenting with signs and symptoms of isolated right heart failure, tricuspid regurgitation, and pulmonary hypertension, which resolved with treatment of hyperthyroidism.

Incidence, clinical characteristics and outcome of congestive heart failure as the initial presentation in patients with primary hyperthyroidism

BACKGROUND

There are limited systematic data on the incidence, clinical characteristics and outcomes of congestive heart failure (CHF) in patients with hyperthyroidism. The aim of this study was to investigate the incidence, clinical characteristics and outcome of CHF as the initial presentation in patients with primary hyperthyroidism.

METHODS

The prevalence, clinical characteristics and outcome of CHF was studied in 591 consecutive patients (mean (SD) age 45 (1) years, 140 men) who presented with primary hyperthyroidism.

RESULTS

CHF was the presenting condition in 34 patients (5.8%) with hyperthyroidism. The presence of atrial fibrillation at presentation (OR 37.4, 95% CI 9.72 to 144.0, p<0.001) was an independent predictor for the occurrence of CHF. Of the 34 patients with CHF, 16 (47%) had systolic left ventricular dysfunction with left ventricular ejection fraction (LVEF)<50%. They were predominantly male (OR 26.6, 95% CI 2.6 to 272.5, p = 0.006) and had a lower serum thyroxine level (OR 0.93, 95% CI 0.87 to 0.99, p = 0.044) than patients with preserved left ventricular systolic function. In these patients, LVEF (55 (4)% vs 30 (2)%, p<0.001) and New York Heart Association functional class (1.2 (0.1) vs 2.5 (0.2), p<0.001) improved significantly 3 months after achieving euthyroid status. Systolic left ventricular dysfunction (mean (SD) LVEF 38 (4)%) persisted on long-term follow-up in five

PATIENTS

no clinical parameter could be identified to predict the occurrence of this persistent cardiomyopathy (p>0.05).

CONCLUSION

CHF was the initial clinical presentation in approximately 6% of patients with hyperthyroidism, and half of them had left ventricular systolic dysfunction. Symptoms of CHF subsided and LVEF improved after treatment for hyperthyroidism. Nonetheless, one-third of these patients developed persistent dilated cardiomyopathy.

New-onset acute heart failure after intravenous glucocorticoid pulse therapy in a patient with Graves' ophthalmopathy

A 53-yr-old previously healthy man was admitted to our hospital for thyrotoxicosis without ophthalmopathy. Initial therapy with propylthiouracil caused an acute elevation of liver enzymes. Then, he received a first course of 131I therapy (20 mCi). At the end of 6-mo follow-up after 131I, he was still thyrotoxic and developed moderately severe ophthalmopathy. The patient refused thyroid surgery and decided to undergo second course of 131I therapy (30 mCi). Concomitantly with the 131I, we opted to give high-dose pulse glucocorticoid therapy (PGT) to prevent further deterioration of GO. The patient was started on intravenous methylprednisolone pulse therapy 1 g daily in a cycle (one cycle every 2 wk, each cycle comprising two infusions on alternate days). After the end of the second day of PGT administration, he suddenly developed onset of acute pulmonary edema and hypertension. There was no previous history of cardiac disorder or conditions predisposing to cardiac failure other than thyrotoxicosis. A presumptive diagnosis of fluid overload and/or hypertension- induced acute heart failure was made. After prompt investigations excluding cardiogenic causes, we thought that this condition was triggered by PGT that was superimposed on thyrotoxicosis-related hemodynamic instability. Graves' patients with uncontrolled thyrotoxicosis should be under careful surveillance when PGT is planned. To our knowledge, this is the first reported case of life-threatening acute pulmonary edema caused by PGT in GO.

Thyroid hormone stimulates protein synthesis in the cardiomyocyte by activating the Akt-mTOR and p70S6K pathways

Thyroid hormones affect cardiac growth and phenotype; however, the mechanisms by which the hormones induce cardiomyocyte hypertrophy remain uncharacterized. Tri-iodo-L-thyronine (T3) treatment of cultured cardiomyocytes for 24 h resulted in a 41 +/- 5% (p < 0.001) increase in [(3)H]leucine incorporation into total cellular protein. This response was abrogated by the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin. Co-immunoprecipitation studies showed a direct interaction of cytosol-localized thyroid hormone receptor TRalpha1 and the p85alpha subunit of PI3K. T3 treatment rapidly increased PI3K activity by 52 +/- 3% (p < 0.005), which resulted in increased phosphorylation of downstream kinases Akt and mammalian target of rapamycin (mTOR). This effect was abrogated by pretreatment with wortmannin or LY294002. Phosphorylation of p70(S6K), a known target of mTOR, occurred rapidly following T3 treatment and was inhibited by rapamycin and wortmannin. In contrast, phosphorylation of the p85 variant of S6K in response to T3 was not blocked by LY294002, wortmannin, or rapamycin, thus supporting a T3-activated pathway independent of PI3K and mTOR. 40 S ribosomal protein S6, a target of p70(S6K), and 4E-BP1, a target of mTOR, were both phosphorylated within 15-25 min of T3 treatment and could be inhibited by wortmannin and rapamycin. Thus, rapid T3-mediated activation of PI3K by cytosolic TRalpha1 and subsequent activation of the Akt-mTOR-S6K signaling pathway may underlie one of the mechanisms by which thyroid hormone regulates physiological cardiac growth.

Thyroid hormone action in the heart

The heart is a major target organ for thyroid hormone action, and marked changes occur in cardiac function in patients with hypo- or hyperthyroidism. T(3)-induced changes in cardiac function can result from direct or indirect T(3) effects. Direct effects result from T(3) action in the heart itself and are mediated by nuclear or extranuclear mechanisms. Extranuclear T(3) effects, which occur independent of nuclear T(3) receptor binding and increases in protein synthesis, influence primarily the transport of amino acids, sugars, and calcium across the cell membrane. Nuclear T(3) effects are mediated by the binding of T(3) to specific nuclear receptor proteins, which results in increased transcription of T(3)-responsive cardiac genes. The T(3) receptor is a member of the ligand-activated transcription factor family and is encoded by cellular erythroblastosis A (c-erb A) genes. T(3) also leads to an increase in the speed of diastolic relaxation, which is caused by the more efficient pumping of the calcium ATPase of the sarcoplasmic reticulum. This T(3) effect results from T(3)-induced increases in the level of the mRNA coding for the sarcoplasmic reticulum calcium ATPase protein, leading to an increased number of calcium ATPase pump units in the sarcoplasmic reticulum.

Thyroid disease and increased cardiovascular risk

The effects of thyroid dysfunction are thought to be reversible on restoration of euthyroidism, but postmortem and epidemiologic data suggest that subclinical or treated thyroid disease is associated with increased vascular risk. In order to determine the extent of this risk, and to explore whether the nature and/or treatment of thyroid disease are critical in this relationship, we used medical record linkage to match patients with treated thyroid disease of various etiologies with routinely collected national inpatient and daycase hospital discharge records and death records, and assessed the number of hospitalizations from cardiovascular or cerebrovascular disease or death in patients with thyroid disease and control patients. Patients treated for Graves' disease had more hospitalizations from cardiovascular disease than controls (relative risk, 1.42; 95% confidence interval, 1.20 to 1.67; p < 0.001). Toxic multinodular goiter was also associated with significantly higher rates of cardiovascular disease (relative risk, 1.50; 95% confidence interval, 1.11 to 2.02; p = 0.008). Patients with Hashimoto's thyroiditis aged over 50 years had a threefold increase in cardiovascular admissions compared to controls (23.5% and 6.5%, respectively; 95% confidence interval for difference, 6.0% to 27.9%; p = 0.003). Thus, different forms of thyroid disease were associated with increased long-term vascular risk despite restoration of euthyroidism. The mechanisms that mediate this risk are unclear but may not involve thyroid hormone abnormality.