Total thyroidectomy in patients with amiodarone-induced thyrotoxicosis and severe left ventricular systolic dysfunction

Cardiac evaluation in amiodarone-induced thyroid dysfunction with suspected cardiac ischemia?: a case report and review of the literature

BACKGROUND

Amiodarone-induced thyroid dysfunction (AIT) is a side-effect associated with the use of Amiodarone for the treatment of refractory arrythmias. Resulting hyperthyroidism can precipitate cardiac complications, including cardiac ischemia and myocardial infarction, although this has only been described in a few case reports.

CASE PRESENTATION

We present here a clinical scenario involving a 66-year-old male Caucasian patient under Amiodarone for atrial fibrillation, who developed AIT. In the presence of dyspnea, multiple cardiovascular risk factors and ECG abnormalities, a transthoracic echocardiogram was performed, showing inferobasal hypokinesia. This led to further investigations through a cardiac PET-CT, where cardiac ischemia was suspected. Ultimately, the coronary angiography revealed no abnormalities. Nonetheless, these extensive cardiologic investigations led to a delay in initiating an emergency endovascular revascularization for acute-on-chronic left limb ischemia. Although initial treatment using Carbimazole was not successful after three weeks, the patient reached euthyroidism after completion of the treatment with Prednisone so that eventually thyroidectomy was not performed. Endovascular revascularization was finally performed after more than one month.

CONCLUSIONS

We discuss here cardiac abnormalities in patients with AIT, which may be due to relative ischemia secondary to increased metabolic demand during hyperthyroidism. Improvement of cardiac complications is expected through an optimal AIT therapy including medical therapy as the primary approach and, when necessary, thyroidectomy. Cardiac investigations in the context of AIT should be carefully considered and may not justify delaying other crucial interventions. If considered mandatory, diagnostic procedures such as coronary angiography should be preferred to functional testing.

Amiodarone-induced thyrotoxicosis: Should surgery be considered?

Amiodarone is the most widely prescribed antiarrhythmic drug worldwide, but induces thyrotoxicosis or hypothyroidism in 15 to 20% of patients. Hyperthyroidism is less frequent than hypothyroidism, and two types of thyrotoxicosis are distinguished according to presence of underlying thyroid disease. Diagnosis is made in case of low TSH and high levels of T3 and T4. Initial treatment is based on anti-thyroid drugs and/or glucocorticoids. Some patients do not respond to medication, which increases the time spent with hyperthyroidism. A long interval between diagnosis and euthyroidism and low left ventricular ejection fraction (LVEF) are predictive of major adverse cardiovascular events. Here, after describing the current state of knowledge of amiodarone-induced thyrotoxicosis, we analyze the literature on the impact of surgery. We suggest that early surgery should be the first option in case of ineffective medical treatment or LVEF<40%. In expert centers, surgical morbidity is no longer different than in other indications for thyroidectomy.

The roles of thyroidectomy in patients with amiodarone-induced thyrotoxicosis: A systematic review

The principal management of Amiodarone-induced-thyrotoxicosis (AIT) is balancing cardiac-thyroid conditions. However, the role of thyroidectomy is still contentious. This systematic review aims to provide insights into the roles of thyroidectomy in the management of AIT. This systematic review encompasses 303 AIT patients who underwent thyroidectomy from 14 studies. The indication of thyroidectomy can be due to cardiac factors, thyrotoxicosis conditions, and patient-physician considerations. Thyroidectomy is more effective in improving thyroid hormone status, cardiac function, and mortality compared to optimal medical therapy, especially in those with left ventricular ejection fraction < 40 %. Thyroidectomy is effective in improving cardiac function and mortality due to shorter duration for achieving euthyroid. Thyroidectomy and medical therapy have comparable side effects. However, the identification of high-risk patients may reduce thyroidectomy complications. Thus, thyroidectomy should not be viewed as the last resource and should be performed immediately when indicated.

Short review: novel concepts in the approach to patients with amiodarone-induced thyrotoxicosis

INTRODUCTION

Amiodarone-induced thyrotoxicosis is associated with high morbidity and mortality rates. The approach to this condition is widely variable across different medical specialists and even among expert endocrinologists. As a matter of fact, the approach to amiodarone-induced thyrotoxicosis has always been considered difficult, due to diagnostic uncertainties easily resulting in missteps, and therapeutic challenges easily resulting in unresponsiveness or slow-responsiveness to the administered drugs.

PURPOSE

Our purpose is to review novelties emerged during the last years about this condition, with the aim to provide novel insights on the diagnostic and therapeutic management of this challenging condition.

Mortality After Total Thyroidectomy for Amiodarone-Induced Thyrotoxicosis According to Left Ventricular Ejection Fraction

OBJECTIVE

To report cardiac outcomes after total thyroidectomy for amiodarone-induced thyrotoxicosis according to the baseline left ventricular ejection fraction in a tertiary referral center.

STUDY DESIGN

Retrospective, monocentric.

SETTING

The tertiary health care system.

METHODS

Patients who underwent total thyroidectomy for amiodarone-induced thyrotoxicosis between 2010 and 2020 with age >18 and available preoperative left ventricular ejection fraction were included in this study. Patients were dichotomized into: group 1 with left ventricular ejection fraction ≥40% (mildly reduced/normal ejection fraction), and group 2 with left ventricular ejection fraction <40% (reduced ejection fraction).

RESULTS

There were 34 patients in group 1 and 17 to group 2. The latter were younger (median 58.4 [Q1-Q3 48.0-64.9] vs. 69.8 years in group 1 [59.8-78.3], p = .0035) and they presented more cardiomyopathy (58.8 vs. 26.5%, p = .030). Overall, the median time until surgery referral was 3.1 [1.9-7.1] months and 47.1% underwent surgery after restoration of euthyroidism. Surgical complications accounted for 7.8%. In group 2, the median left ventricular ejection fraction was significantly improved after surgery (22.5 [20.0-25.0] vs. 29.0% [25.3-45.5], p = .0078). Five-year cardiac mortality was significantly higher in group 2 (p < .0001): 47.0% died of cardiac causes versus 2.9% in group 1. A baseline left ventricular ejection fraction <40% and a longer time until surgery referral were significantly associated with cardiac mortality (multivariable Cox regression analysis, p = .015 and .020, respectively).

CONCLUSION

These results reinforce the idea that surgery, if chosen, should be performed quickly in patients with left ventricular ejection fraction <40%.

Anaesthetic management of thyroid storm in a patient with Friederich's ataxia. A case report

A 26-year-old patient with Friederich's ataxia with hypertrophic obstructive cardiomyopathy undergoing total thyroidectomy due to persistent amiodarone-induced thyrotoxicosis (despite high doses of antithyroid drugs and corticosteroids), presented an intraoperative episode suggestive of thyroid storm. Thyroid storm is an endocrine emergency that is associated with high morbidity and mortality. Early diagnosis and treatment, which is of vital importance to improve survival, includes symptomatic treatment, treatment of cardiovascular, neurological, and/or hepatic manifestations and thyrotoxicosis, measures to suppress or avoid triggering stimuli, and definitive treatment.

Total thyroidectomy in a patient awaiting heart transplant with amiodarone-induced thyrotoxicosis: A case report

Thyroid function may have a severe impact in cardiac function. Herein, we present the case report of a 53-year-old male patient awaiting heart transplant with amiodarone induced thyrotoxicosis that presented a marked improvement of his cardiac function after total thyroidectomy.

Real-life data on the impact of medical therapy for amiodarone-induced thyrotoxicosis on CV events and hospitalizations

CONTEXT

Patients with amiodarone-induced thyrotoxicosis (AIT) often receive the initial therapy for thyrotoxicosis in several different medical settings before admission to a referral center. Whether the first-line medical therapy (i.e. therapies for thyrotoxicosis at first diagnosis of AIT) affects the outcome of AIT patients is unknown.

STUDY DESIGN

Single-center historical-prospective cohort study of 313 AIT patients.

METHODS

Clinical and biochemical data were collected at first diagnosis, at a referral center, and during the course of AIT. Primary outcomes were cardiovascular events and hospitalizations. First-line therapies were considered appropriate when they included glucocorticoids for type 2 AIT and methimazole for type 1 AIT at the approved dosage, either alone (optimal medical therapy, OMT) or in combination (right-dose combination therapy, RCT). Other therapies were considered not appropriate, including no therapy. Duration of exposure to thyrotoxicosis was the time from first diagnosis of AIT to its remission.

RESULTS

34.5% patients received appropriate therapies (28.1% OMT, 6.4% RCT), whereas the remaining (65.5%) received non-appropriate therapies. Cardiovascular events, and hospitalizations were more frequent in patients who received non-appropriate therapies (33.2% vs 4.5%, and 24.9% vs 6.5%, respectively; p<0.0001 for both). Appropriate therapies reduced serum thyroid hormone concentrations (p=0.018) from first diagnosis to referral, unlike the non-appropriate therapies. The duration of exposure to thyrotoxicosis was longer in patients receiving non-appropriate therapies and was a risk factor for arrhythmias (HR 1.004, p=0.0008), MACEs (HR 1.004, p=0.020) and hospitalizations (HR 1.006, p<.0001).

CONCLUSIONS

The first medical therapy of AIT influences the exposure time to thyrotoxicosis and the occurrence of cardiovascular events and hospitalizations.

Early surgery: a favorable prognosticator in amiodarone-induced thyrotoxicosis-a single-center experience with 53 cases

Fewer than 100 cases of amiodarone-induced thyrotoxicosis (AIT) managed surgically have been reported worldwide. This study aims to assess the outcome of thyroidectomy under general anesthesia in a relatively large case series. A retrospective analysis of the clinical records of 53 patients who underwent thyroidectomy for AIT between 1995 and 2019 was conducted. There were 48 (90%) males and 5 females with an average age of 63.7 years. Type 1 and 2 AIT were present in 35 (66%) and 18 (34%) of patients, respectively. The mean preoperative ejection fraction (EF) was 45 ± 13%. Salvage surgery was performed in 6 (11%) patients due to decompensating heart failure and/or malignant arrhythmias. 35 (66%) patients underwent urgent surgery due to a predicted late response to medical therapy and/or the need to discontinue it. Elective surgery was performed in the remainder. A considerable improvement in mean EF occurred 12 months post-surgery (44% vs. 49%; p < 0.001). The overall survival rate following thyroidectomy was 96% at 12 months, and 83% at 5 years. No survival differences were observed based on systolic function. Cardiac-specific mortality was 11%, and these patients demonstrated a considerably shorter survival post-surgery compared to those who died of a non-cardiac cause (27 ± 18 vs. 77.5 ± 54 months; p < 0.05). Total thyroidectomy can be safely performed under general anesthesia despite severe cardiac disease. It considerably improves cardiac function and confers a survival advantage. Therefore, it should be considered early in the treatment plan of select cases.

Thyroid dysfunction on the heart: clinical effects, prognostic impact and management strategies

Thyroid hormones have a considerable influence on cardiac function and structure. There are direct and indirect effects of thyroid hormone on the cardiovascular system, which are prominent in both hypothyroidism and hyperthyroidism. In this review, we discuss how thyroid dysfunction impacts cardiovascular pathophysiology and the underlying molecular mechanisms.

Cardiovascular Involvement in Thyrotoxicosis Resulting in Heart Failure: The Risk Factors and Hemodynamic Implications

Thyrotoxicosis is a clinical syndrome with persistently elevated concentrations of free triiodothyronine, free thyroxine, or both, which correlates with an increased thyroid metabolic function. This article has discussed the direct effect of increased thyroid hormone on the heart, as the thyroid hormone physiologically exhibits a close harmony with hormones of the cardiovascular system. This action can lead to disturbances in hemodynamic stability, exacerbating the possibility of developing complications such as heart failure and life-threatening arrhythmias. This article has also explored the multifaceted pathogenesis of thyrotoxicosis and various pharmacological treatment options, including beta-blockers and anti-thyroid drugs. This article has reviewed numerous studies that have concluded that the main goal of therapy should always aim to normalize thyroid hormone levels based on the etiology of the thyrotoxicosis, although cardiovascular conditions are associated with a higher rate of mortality.

Amiodarone-Induced Thyrotoxicosis - Literature Review & Clinical Update

Amiodarone is widely used in treating atrial and ventricular arrhythmias; however, due to its high iodine concentration, the chronic use of the drug can induce thyroid disorders. Amiodarone-induced thyrotoxicosis (AIT) can decompensate and exacerbate underlying cardiac abnormalities, leading to increased morbidity and mortality, especially in patients with left ventricular ejection fraction <30%. AIT cases are classified into two subtypes that guide therapeutic management. The risks and benefits of maintaining the amiodarone must be evaluated individually, and the therapeutic decision should be taken jointly by cardiologists and endocrinologists. Type 1 AIT treatment is similar to that of spontaneous hyperthyroidism, using antithyroid drugs (methimazole and propylthiouracil) at high doses. Type 1 AIT is more complicated since it has proportionally higher recurrences or even non-remission, and definitive treatment is recommended (total thyroidectomy or radioiodine). Type 2 AIT is generally self-limited, yet due to the high mortality associated with thyrotoxicosis in cardiac patients, the treatment should be implemented for faster achievement of euthyroidism. Furthermore, in well-defined cases of type 2 AIT, the treatment with corticosteroids is more effective than treatment with antithyroid drugs. In severe cases, regardless of subtype, immediate restoration of euthyroidism through total thyroidectomy should be considered before the patient progresses to excessive clinical deterioration, as delayed surgery indication is associated with increased mortality.

[Clinical practice guidelines for acute and chronic thyroiditis (excluding autoimmune thyroiditis)]

Острые и хронические заболевания щитовидной железы занимают второе место по выявляемости после сахарного диабета. Всемирная организация здравоохранения отмечает ежегодную тенденцию к увеличению числа заболеваний щитовидной железы. В настоящих клинических рекомендациях будут рассмотрены вопросы этиологии, клинического течения, диагностики и лечения острых и хронических (за исключением аутоиммунного) воспалительных заболеваний щитовидной железы.Клинические рекомендации — это основной рабочий инструмент практикующего врача, как специалиста, так и врача узкой практики. Лаконичность, структурированность сведений об определенной нозологии, методов ее диагностики и лечения, базирующихся на принципах доказательной медицины, позволяют в короткий срок дать тот или иной ответ на интересующий вопрос специалисту, добиваться максимальной эффективности и персонализации лечения.Клинические рекомендации составлены профессиональным сообществом узких специалистов, одобрены экспертным советом Министерства здравоохранения РФ. Представленные рекомендации содержат максимально полную информацию, которая требуется на этапе диагностики острых и хронических тиреоидитов, этапе выбора тактики ведения пациентов с тиреоидитом, а также на этапе лечения пациента.Рабочая группа представляет этот проект в профессиональном журнале, посвященном актуальным проблемам эндокринологии, с целью повышения качества оказываемой медицинской помощи, повышения эффективности лечения острых и хронических тиреоидитов путем ознакомления с полным тестом клинических рекомендаций по острым и хроническим тиреоидитам (исключая аутоиммунный тиреоидит) максимально возможного количества специалистов в области не только эндокринологии, но и медицины общей (семейной) практики.

Thyroid effects of amiodarone: clinical update

PURPOSE OF REVIEW

Amiodarone-induced thyroid dysfunction is well established and commonly encountered but is associated with several diagnostic and management challenges. The present review discusses recent evidence published related to the effects of amiodarone on the thyroid gland and thyroid function.

RECENT FINDINGS

Retrospective studies to evaluate amiodarone-induced thyroid dysfunction in children show the occurrence of potential clinically significant changes within 2 weeks of amiodarone initiation that may not be detected if standard adult guidelines for thyroid hormone monitoring are followed. A small study evaluating beta-glucuronidase activity in amiodarone-induced thyrotoxicosis (AIT) demonstrated higher levels in patients with AIT type 2 compared to type 1. New data have suggested the incidence of agranulocytosis may be higher in patients on thionamides with AIT compared to hyperthyroidism because of other causes. In a small study, investigators demonstrated the use of a combination of intravenous and oral steroids to treat refractory AIT which needs to be evaluated in further controlled trials. Finally, recent data demonstrated a possible mortality benefit of surgery over medical therapy for AIT in patients with moderate to severe reduction in left ventricular ejection fraction.

SUMMARY

Recent research regarding the prevalence, diagnosis, and management of amiodarone-induced thyroid dysfunction were reviewed.

Duration of Exposure to Thyrotoxicosis Increases Mortality of Compromised AIT Patients: the Role of Early Thyroidectomy

CONTEXT

Patients with amiodarone-induced thyrotoxicosis (AIT) and severely reduced left ventricular ejection fraction (LVEF) have a high mortality rate that may be reduced by total thyroidectomy. Whether in this subset of patients thyroidectomy should be performed early during thyrotoxicosis or later after restoration of euthyroidism has not yet been settled.

OBJECTIVES

Mortality rates, including peritreatment mortality and 5-year cardiovascular mortality, and predictors of death, evaluated by Cox regression analysis.

METHODS

Retrospective cohort study of 64 consecutive patients with AIT selected for total thyroidectomy from 1997 to 2019. Four groups of patients were identified according to serum thyroid hormone concentrations and LVEF: Group 1 (thyrotoxic, LVEF <40%), Group 2 (thyrotoxic, LVEF ≥40%), Group 3 (euthyroid, LVEF < 40%), Group 4 (euthyroid, LVEF ≥40%).

RESULTS

Among patients with low LVEF (Groups 1 and 3), mortality was higher in patients undergoing thyroidectomy after restoration of euthyroidism (Group 3) than in those submitted to surgery when still thyrotoxic (Group 1): peritreatment mortality rates were 40% versus 0%, respectively (P = .048), whereas 5-year cardiovascular mortality rates were 53.3% versus 12.3%, respectively (P = .081). Exposure to thyrotoxicosis was longer in Group 3 than in Group 1 (112 days, interquartile range [IQR] 82.5-140, vs 76 days, IQR 24.8-88.5, P = .021). Survival did not differ in patients with LVEF ≥40% submitted to thyroidectomy irrespective of being thyrotoxic (Group 2) or euthyroid (Group 4): in this setting, peritreatment mortality rates were 6.3% versus 4% (P = .741) and 5-year cardiovascular mortality rates were 12.5% and 20% (P = .685), respectively. Age (hazard ratio [HR] 1.104, P = .029) and duration of exposure to thyrotoxicosis (HR 1.004, P = .039), but not presurgical serum thyroid hormone concentrations (P = .577 for free thyroxine, P = .217 for free triiodothyronine), were independent predictors of death.

CONCLUSIONS

A prolonged exposure to thyrotoxicosis resulted in increased mortality in patients with reduced LVEF, which may be reduced by early thyroidectomy.

Management of Cardiogenic Shock due to Thyrotoxicosis: A Systematic Literature Review

Background

A grave complication of thyrotoxicosis, or thyroid storm, is the development of heart failure and cardiomyopathy. Recognizing this condition is imperative in preventing further left ventricular dysfunction and cardiogenic shock. This manuscript aims to review the literature on cardiogenic shock associated with thyrotoxicosis and present management recommendations on this rare condition.

Methods

A literature search was performed in December of 2018, using the PubMed medical search engine. A systematic search was carried out using the keywords Thyroid Storm AND Cardiogenic Shock and Thyrotoxicosis AND Shock.

Management

Decrease of thyroid hormone levels using therapeutic plasma exchange LV Unloading and ventilation by Impella and Extracorporeal Mechanical Ventilation (ECMO).

Conclusion

Patients presenting with thyroid storm-induced shock may not be suitable candidates for traditional management with β-adrenergic blockers (β-blockers). The use of β-blockers could exasperate their condition. Through extensive literature review on this rare condition, the most effective management was found to be therapeutic plasma exchange in order to decrease thyroid hormone levels, which have direct toxic effect on the heart. Furthermore, the use of ECMO and Impella is advised to reduce pressure on the heart and ensure the patient’s organs are well oxygenated and perfused while the left ventricle is recovering.

Comparison Between Total Thyroidectomy and Medical Therapy for Amiodarone-Induced Thyrotoxicosis

CONTEXT

It is not known whether total thyroidectomy is more favorable than medical therapy for patients with amiodarone-induced thyrotoxicosis (AIT).

OBJECTIVE

To compare total thyroidectomy with medical therapy on survival and cardiac function in AIT patients.

METHODS

Observational longitudinal cohort study involving 207 AIT patients that had received total thyroidectomy (surgery group, n = 51) or medical therapy (medical therapy group, n = 156) over a 20-year period. AIT types and left ventricular ejection fraction (LVEF) classes were determined at diagnosis of AIT. Cardiac and thyroid function were reevaluated during the study period. Survival was estimated using the Kaplan-Meier method.

RESULTS

Overall mortality and cardiac-specific mortality at 10 and 5 years, respectively, were lower in the surgery group than in the medical therapy group (P = 0.04 and P = 0.01, respectively). The lower mortality rate of the surgery group was due to patients with moderate to severely compromised LVEF (P = 0.005 vs medical therapy group). In contrast, mortality of patients with normal or mildly reduced LVEF did not differ between the 2 groups (P = 0.281 and P = 0.135, respectively). Death of patients with moderate to severe LV systolic dysfunction in the medical therapy group occurred after 82 days (interquartile range, 56-99), a period longer than that necessary to restore euthyroidism in the surgery group (26 days; interquartile range, 15-95; P = 0.038). Risk factors for mortality were age (hazard ratio [HR] = 1.036) and LVEF (HR = 0.964), whereas total thyroidectomy was shown to be a protective factor (HR = 0.210). LVEF increased in both groups after restoration of euthyroidism, above all in the most compromised patients in the surgery group.

CONCLUSIONS

Total thyroidectomy could be considered the therapeutic choice for AIT patients with severe systolic dysfunction, whereas it is not superior to medical therapy in those with normal or mildly reduced LVEF.

Thyrotoxicosis: Diagnosis and Management

Thyrotoxicosis is the clinical manifestation of excess thyroid hormone action at the tissue level due to inappropriately high circulating thyroid hormone concentrations. Hyperthyroidism, a subset of thyrotoxicosis, refers specifically to excess thyroid hormone synthesis and secretion by the thyroid gland. We performed a review of the literature on these topics utilizing published data in PubMed and MEDLINE. In this review, we discuss the more common etiologies of thyrotoxicosis, focusing on the current approach to diagnosis and management, new trends in those directions, and potential upcoming changes in the field.

[Challenges in the management of amiodarone-induced thyrotoxicosis]

Amiodarone, a benzofuranic iodine-rich pan antiarrhythmic drug, is frequently associated with thyroid dysfunction. This side effect is heterogeneous and unpredicted, motivating regular evaluation of thyroid function tests. In contrary to hypothyroidism, amiodarone-induced thyrotoxicosis (AIT) is a challenging situation owing to the risk of deterioration of the general and cardiac status of such debilitating patients. Classically, AIT is either an iodine-induced thyrotoxicosis in patients with an abnormal thyroid (type I), or due to a subacute thyroiditis on a "healthy" thyroid (type II). Even if many studies tried to better identify the types of AIT, the diagnostic dilemma of type of AIT could be present, and many patients are treated by an association of antithyroid drugs (useful for type I AIT) with corticoids (useful for type II AIT). Being the main etiological factor in AIT, amiodarone is supposed to be stopped, but it could remain the only anti-arrhythmic option that is needed to be either continued or reintroduced to improve the cardiovascular survival. Recently, many studies demonstrated that amiodarone could be continued or reintroduced in patients with history of type II AIT. Nevertheless, in the other patients, amiodarone maintenance complicates the therapeutic response to the antithyroid drugs and increases the risk of AIT recurrence. Thus, amiodarone therapy is preferred to be interrupted. In such patients, thyroid ablation is recommended once AIT is under control.

Issues in amiodarone-induced thyrotoxicosis: Update and review of the literature

Amiodarone, a benzofuranic iodine-rich pan-anti-arrhythmic drug, induces amiodarone-induced thyrotoxicosis (AIT) in 7-15% of patients. AIT is a major issue due to its typical severity and resistance to anti-thyroid measures, and to its negative impact on cardiac status. Classically, AIT is either an iodine-induced thyrotoxicosis in patients with abnormal thyroid (type 1), or due to acute thyroiditis in a "healthy" thyroid (type 2). Determination of the type of AIT is a diagnostic dilemma, as characteristics of both types may be present in some patients. As it is the main etiological factor in AIT, it is recommended that amiodarone treatment should be stopped; however, it may be the only anti-arrhythmic option, needing to be either continued or re-introduced to improve cardiovascular survival. Recently, a few studies demonstrated that amiodarone could be continued or re-introduced in patients with history of type-2 AIT. However, in the other patients, it is recommended that amiodarone treatment be interrupted, to improve response to thioamides and to alleviate the risk of AIT recurrence. In such patients, thyroidectomy is recommended once AIT is under control, allowing safe re-introduction of amiodarone.

Thyroidectomy for Amiodarone-Induced Thyrotoxicosis: Mayo Clinic Experience

Context

Amiodarone-induced thyrotoxicosis (AIT) is a difficult diagnostic and management challenge, especially during severe thyrotoxicosis accompanied by cardiovascular compromise.

Objective

To evaluate thyroidectomy for the management of AIT.

Design

Retrospective cohort study of adults with noncongenital heart disease with AIT after >3 months of amiodarone who underwent thyroidectomy from 1 November 2002 to 31 December 2016.

Setting

Referral center.

Patients

The group was comprised of 17 patients.

Main Outcome Measures

Thyroid function, left ventricular ejection fraction (LVEF), and surgical complications were the main outcome measures.

Results

Patients had median age of 60 years, 82.4% were male, and 47% had systolic heart failure. At diagnosis, median TSH was 0.005 mIU/L, median free T4 was 3.25 ng/dL, and total T3 was 198.5 ng/dL. We classified five patients as type 1 and type 2 and two patients as mixed; five patients remained undefined. The most common surgical indications were medically refractory disease, worsening cardiac status, and severe thyrotoxicosis requiring prompt resolution. Within 1 week post-thyroidectomy, median TSH was 0.565 mIU/L, and free T4 was 1.8 ng/dL. Median LVEF improved by 8% in patients with systolic heart failure. Seven patients had a complication within 30 days postsurgery (rehospitalization, n = 4; cervical hematoma, n = 2; recurrent arrhythmia, n = 2; symptomatic hypocalcemia, n = 1; death, n = 1). A larger thyroid gland was a risk factor for complications.

Conclusions

Thyroidectomy resulted in rapid resolution of thyrotoxicosis. Its complication rate was higher than for non-AIT indications but lower than previously reported in a similar population of high-risk surgical patients.

Amiodarone-induced thyrotoxicosis in heart failure with a reduced ejection fraction: A retrospective cohort study

BACKGROUND

Amiodarone-induced thyrotoxicosis (AIT) is associated with significant morbidity and mortality. We aimed to describe AIT and its clinical outcomes in patients with heart failure with reduced ejection fraction (HFrEF).

METHODS

We performed a retrospective chart review at a heart failure center in Winnipeg, Canada. We screened 1059 consecutive patients seen over a 12-month period (August 2011 to July 2012) for AIT in patients with HFrEF. Using descriptive and Cox proportional hazard analyses, we explored the association between AIT and mortality.

RESULTS

A total of 110 patients with HFrEF who were exposed to amiodarone were included in the analysis. Of these, 13 (11.8%) were diagnosed with AIT. All AIT patients in our cohort were male. Amiodarone was discontinued in nearly half (46.2%) of patients with AIT. All patients were treated with antithyroid medications, and 5 patients (38.5%) also received prednisone. Euthyroidism was achieved in 2 patients (15.4%), hypothyroidism occurred in 6 patients (46.2%), and 5 patients remained thyrotoxic until death or time of chart review (38.5%).

CONCLUSION

Thyrotoxicosis is common in patients with HFrEF on amiodarone and is challenging to treat. Due to the sample size, while no association was found in mortality for patients with HFrEF with AIT, a real association could have been missed.

2018 European Thyroid Association (ETA) Guidelines for the Management of Amiodarone-Associated Thyroid Dysfunction

Treatment with amiodarone is associated with changes in thyroid function tests, but also with thyroid dysfunction (amiodarone-induced hypothyroidism, AIH, and amiodarone-induced thyrotoxicosis, AIT). Both AIH and AIT may develop in apparently normal thyroid glands or in the presence of underlying thyroid abnormalities. AIH does not require amiodarone withdrawal, and is treated with levothyroxine replacement if overt, whereas subclinical forms may be followed without treatment. Two main types of AIT are recognized: type 1 AIT (AIT 1), a form of iodine-induced hyperthyroidism occurring in nodular goitres or latent Graves disease, and type 2 AIT (AIT 2), resulting from destructive thyroiditis in a normal thyroid gland. Mixed/indefinite forms exist due to both pathogenic mechanisms. AIT 1 is best treated with thionamides that may be combined for a few weeks with sodium perchlorate to make the thyroid gland more sensitive to thionamides. AIT 2 is treated with oral glucocorticoids. Once euthyroidism has been restored, AIT 2 patients are followed up without treatment, whereas AIT 1 patients should be treated with thyroidectomy or radioiodine. Mixed/indefinite forms of AIT are treated with thionamides. Oral glucocorticoids can be added from the beginning if a precise diagnosis is uncertain, or after a few weeks if response to thionamides alone is poor. The decision to continue or to stop amiodarone in AIT should be individualized in relation to cardiovascular risk stratification and taken jointly by specialist cardiologists and endocrinologists. In the presence of rapidly deteriorating cardiac conditions, emergency thyroidectomy may be required for all forms of AIT.

Hyperthyroidism and the Heart

Thyroid hormones have a significant impact on cardiac function and structure. Excess thyroid hormone affects cardiovascular hemodynamics, leading to high-output heart failure and, in late stages, dilated cardiomyopathy. In this review, we discuss how hyperthyroidism affects cardiovascular pathophysiology and molecular mechanisms and examine the complications caused by excess thyroid hormone, such as heart failure and atrial fibrillation.

Management of Amiodarone-Induced Thyrotoxicosis at a Cardiac Transplantation Centre

Background: Amiodarone-induced thyrotoxicosis (AIT) is associated with significant morbidity and mortality, particularly in patients with cardiac failure. The aim of the study was to evaluate the management of AIT at a tertiary hospital specialising in cardiac failure and transplantation. Methods: Retrospective audit of 66 patients treated for AIT by Endocrinology (2007-2016), classified as type 1 (T1) or type 2 (T2) based on radiological criteria. Main outcome measurements were response rate to initial treatment, time to euthyroidism, and frequency/safety of thyroidectomy. Results: Mean age was 60 ± 2 years; 80% were male. Sixty-four patients commenced medical treatment: thionamides (THIO) in 23, glucocorticoids (GC) in 17 and combination (COMB) in 24. Median thyroxine (fT4) was 35.1 (31.2-46.7) in THIO, 43.1 (30.4 -60.7) in GC, and 60.0 (39.0 ->99.9) pmol/L in COMB (p = 0.01). Initial therapy induced euthyroidism in 52%: 70% THIO, 53% GC, and 33% COMB (p = 0.045) by 100 (49-167), 47 (35-61), and 53 (45-99) days, respectively (p = 0.02). A further 11% became euthyroid after transitioning from monotherapy to COMB. Thyroidectomy was undertaken in 33%. Patients who underwent thyroidectomy were younger (54 ± 3 vs. 63 ± 2 years; p = 0.03), with higher prevalence of severely impaired left ventricular function prior to diagnosis of AIT (38 vs. 18%; p = 0.08). Despite median American Society of Anaesthesiologists classification 4, no thyroidectomy patient experienced cardiorespiratory complications/death. Conclusions: Patients with AIT had limited response to medical treatment. The poorest response was observed in COMB group, likely related to greater hyperthyroidism severity. Thyroidectomy is safe in patients with severe cardiac failure if performed in a centre with cardiac anaesthetic expertise. There should be low threshold for proceeding to thyroidectomy in patients with severe AIT and/or cardiac failure.

Recovery following Thyroxine Treatment Withdrawal, but Not Propylthiouracil, Averts In Vivo and Ex Vivo Thyroxine-Provoked Cardiac Complications in Adult FVB/N Mice

Persistent cardiovascular pathology has been described in hyperthyroid patients even with effective antithyroid treatment. Here, we studied the effect of a well-known antithyroid drug, propylthiouracil (PTU; 20 mg/kg/day), on thyroxine (T4; 500 µg/kg/day)-induced increase in blood pressure (BP), cardiac hypertrophy, and altered responses of the contractile myocardium both in vivo and ex vivo after 2 weeks of treatment. Furthermore, the potential recovery through 2 weeks of T4 treatment discontinuation was also investigated. PTU and T4 recovery partially reduced the T4-prompted increase in BP. Alternatively, PTU significantly improved the in vivo left ventricular (LV) function with no considerable effects on cardiac hypertrophy or ex vivo right ventricular (RV) contractile alterations subsequent to T4 treatment. Conversely, T4 recovery considerably enhanced the T4-provoked cardiac changes both in vivo and ex vivo. Altogether, our data is in agreement with the proposal that hyperthyroidism-induced cardiovascular pathology could persevere even with antithyroid treatments, such as PTU. However, this cannot be generalized and further investigation with different antithyroid treatments should be executed. Moreover, we reveal that recovery following experimental hyperthyroidism could potentially ameliorate cardiac function and decrease the risk for additional cardiac complications, yet, this appears to be model-dependent and should be cautiously construed.

The clinical value of regular thyroid function tests during amiodarone treatment

OBJECTIVE

Amiodarone is used for the maintenance of sinus rhythm in patients with arrhythmias, but thyroid dysfunction (amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH)) is a common adverse effect. As the onset of AIT and AIH may be unpredictable, the value of long-term regular monitoring of amiodarone treated patients for thyroid dysfunction is still uncertain.

DESIGN

We retrospectively documented the frequency at which overt thyroid dysfunction was preceded by subclinical thyroid dysfunction.

METHODS

We included 303 patients treated with amiodarone between 1984 and 2007. AIT was defined as a lowered TSH level with an elevated free thyroxine (FT4) and AIH was defined as an elevated TSH level with a decreased or subnormal FT4. Subclinical AIT was defined as a lowered TSH level with a normal FT4 and subclinical AIH as an elevated TSH level with a normal FT4.

RESULTS

200 men and 103 women, aged 62 ± 12.0 years, suffering from atrial (260) or ventricular (43) arrhythmias, were evaluated. During a median follow-up of 2.8 (1.0-25) years, 44 patients developed AIT and 33 AIH. In 42 (55%) patients who developed AIT/AIH, earlier thyroid function tests showed no subclinical AIT or subclinical AIH. In 35 (45%) patients, AIT/AIH was preceded by subclinical AIT or subclinical AIH (16/44 for AIT and 19/33 for AIH).

CONCLUSIONS

In a considerable proportion of patients who developed AIT/AIH, earlier thyroid function tests showed no subclinical AIT/AIH. Less than half of the patients with a subclinical event subsequently developed overt AIT/AIH. This study provides data to reconsider the yield of regular testing of thyroid function to predict overt thyroid dysfunction in amiodarone treated patients.

Successful Pretreatment Using Plasma Exchange before Thyroidectomy in a Patient with Amiodarone-Induced Thyrotoxicosis

INTRODUCTION

Amiodarone, used for the management of tachyarrhythmias, is associated with both hypothyroidism and thyrotoxicosis. Total thyroidectomy is an effective procedure for promptly reducing circulating thyroid hormone levels. It has been proposed in patients who have severe amiodarone-induced thyrotoxicosis (AIT) or are refractory to medical therapy, or when such therapy is contraindicated. Therapeutic plasma exchange (TPE) may be considered as a pretreatment for restoring a euthyroid state preoperatively, thereby reducing a patient's symptoms and the potential perioperative risk associated with thyrotoxicosis.

CASE REPORT

We describe the case of a 62-year-old man with type 2 AIT who presented with severe unremitting thyrotoxicosis after 8 weeks of medical therapy with glucocorticosteroids, thiamazole, and potassium perchlorate. Given the severity of his presentation, a total thyroidectomy was indicated. TPE was performed preoperatively and was successful in rapidly restoring euthyroidism. This dramatically improved the patient's symptoms which had been suggestive of ischemic heart disease. Subsequently, the patient underwent total thyroidectomy under general anesthesia without any major complications.

CONCLUSION

TPE is successful in rapidly restoring a clinical and biochemical euthyroid state, and may be used to decrease the perioperative risks associated with thyroidectomy in patients with life-threatening thyrotoxicosis or in cases refractory to medical treatment.

2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis

BACKGROUND

Thyrotoxicosis has multiple etiologies, manifestations, and potential therapies. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions and patient preference. This document describes evidence-based clinical guidelines for the management of thyrotoxicosis that would be useful to generalist and subspecialty physicians and others providing care for patients with this condition.

METHODS

The American Thyroid Association (ATA) previously cosponsored guidelines for the management of thyrotoxicosis that were published in 2011. Considerable new literature has been published since then, and the ATA felt updated evidence-based guidelines were needed. The association assembled a task force of expert clinicians who authored this report. They examined relevant literature using a systematic PubMed search supplemented with additional published materials. An evidence-based medicine approach that incorporated the knowledge and experience of the panel was used to update the 2011 text and recommendations. The strength of the recommendations and the quality of evidence supporting them were rated according to the approach recommended by the Grading of Recommendations, Assessment, Development, and Evaluation Group.

RESULTS

Clinical topics addressed include the initial evaluation and management of thyrotoxicosis; management of Graves' hyperthyroidism using radioactive iodine, antithyroid drugs, or surgery; management of toxic multinodular goiter or toxic adenoma using radioactive iodine or surgery; Graves' disease in children, adolescents, or pregnant patients; subclinical hyperthyroidism; hyperthyroidism in patients with Graves' orbitopathy; and management of other miscellaneous causes of thyrotoxicosis. New paradigms since publication of the 2011 guidelines are presented for the evaluation of the etiology of thyrotoxicosis, the management of Graves' hyperthyroidism with antithyroid drugs, the management of pregnant hyperthyroid patients, and the preparation of patients for thyroid surgery. The sections on less common causes of thyrotoxicosis have been expanded.

CONCLUSIONS

One hundred twenty-four evidence-based recommendations were developed to aid in the care of patients with thyrotoxicosis and to share what the task force believes is current, rational, and optimal medical practice.

Quantitative assessment of thyroid-to-background ratio improves the interobserver reliability of technetium-99m sestamibi thyroid scintigraphy for investigation of amiodarone-induced thyrotoxicosis

BACKGROUND

Amiodarone-induced thyrotoxicosis (AIT) is caused by excessive hormone synthesis and release (AIT I), a destructive thyroiditis (AIT II), or a combination of both (AIT Ind). Although no gold-standard diagnostic test is available, technetium-99m sestamibi thyroid scintigraphy (99mTc-STS) has been previously reported to be an accurate tool for differentiating subtypes with important therapeutic implications. However, the information to guide reporting of 99mTc-STS is qualitative and highly subjective. This study aims to compare the interobserver reliability of 99mTc-STS before and after the use of quantitative thyroid-to-background ratios (TBRs) displayed on a time-activity curve for differentiation of AIT subtypes.

METHODS

A retrospective audit of Nuclear Medicine Departments at Royal Melbourne Hospital (Parkville, Victoria, Australia) and Cabrini Hospital (Malvern, Victoria, Australia) identified 15 consecutive 99mTc-STS studies performed for AIT. Four nuclear medicine physicians reported the studies according to previously established criteria (series 1). Quantitative TBR and estimated 'normal' range TBR were subsequently provided before the studies were reordered and reported again (series 2). Interobserver reliability was calculated using Fleiss' κ statistic for each assessment.

RESULTS

The overall percentage of agreement (PoA) and κ statistics for use of conventional 99mTc-STS for diagnosis of AIT improved from 47 to 80% and from 0.30 to 0.67 following the use of quantitative TBR displayed on a time-activity curve with reference to a normal population. Interobserver reliability improved substantially under all diagnostic comparisons, particularly for differentiation of either AIT I (PoA 80% to 94%, κ: 0.48 to 0.84) or AIT Ind (PoA 47% to 82%, κ: -0.05 to 0.51) from other types of AIT.

CONCLUSION

Use of quantitative TBR improves the interobserver reliability of reporting 99mTc-STS for investigation of different types of AIT. There is 'almost perfect' agreement upon differentiation of AIT I from AIT II and AIT Ind, with important implications for rationalizing the use of corticosteroid therapy. Prospective identification of AIT Ind is improved from 'poor' to a 'moderate' level of agreement to facilitate rational use of combination therapy at diagnosis.

Amiodarone-induced thyrotoxic thyroiditis: a diagnostic and therapeutic challenge

Amiodarone is an iodine-based, potent antiarrhythmic drug bearing a structural resemblance to thyroxine (T4). It is known to produce thyroid abnormalities ranging from abnormal thyroid function testing to overt hypothyroidism or hyperthyroidism. These adverse effects may occur in patients with or without preexisting thyroid disease. Amiodarone-induced thyrotoxicosis (AIT) is a clinically recognized condition commonly due to iodine-induced excessive synthesis of thyroid, also known as type 1 AIT. In rare instances, AIT is caused by amiodarone-induced inflammation of thyroid tissue, resulting in release of preformed thyroid hormones and a hyperthyroid state, known as type 2 AIT. Distinguishing between the two states is important, as both conditions have different treatment implications; however, a mixed presentation is not uncommon, posing diagnostic and treatment challenges. We describe a case of a patient with amiodarone-induced type 2 hyperthyroidism and review the current literature on the best practices for diagnostic and treatment approaches.

Effects of amiodarone, thyroid hormones and CYP2C9 and VKORC1 polymorphisms on warfarin metabolism: a review of the literature

OBJECTIVE

To review the literature regarding the interaction among amiodarone therapy, thyroid hormone levels, and warfarin metabolism.

METHODS

A 73-year-old male with type 2 after describing an unusual case of amiodarone-induced thyrotoxicosis (AIT) who experienced a severe rise in international normalized ratio (INR) values after initiating warfarin therapy due to an unusual combination of excessive thyroid hormones, amiodarone therapy, and a genetic abnormality affecting warfarin metabolism.

RESULTS

Genetic analysis revealed that the patient was CYP2C9*2 wild-type, CYP2C9*3/*3 homozygous mutant, and VKORC1*3/*3 homozygous mutant. A review of the literature revealed that both mutations can independently affect warfarin metabolism. In addition, amiodarone therapy and the presence of thyrotoxicosis per se can affect warfarin metabolism and reduce the dose needed to maintain INR in the therapeutic range. The association of the 2 genetic polymorphisms in a patient with AIT is extremely rare and strongly impairs warfarin metabolism, exposing the patient to a high risk of overtreatment.

CONCLUSIONS

In patients with AIT, warfarin therapy should be gradually introduced, starting with a very low dose, because of the significant risk of warfarin overtreatment. Whether the genetic analysis of CYP2C9 and VKORC1 polymorphisms should be routinely performed in AIT patients remains conjectural.

Consequences of excess iodine

Iodine is a micronutrient that is essential for the production of thyroid hormones. The primary source of iodine is the diet via consumption of foods that have been fortified with iodine, including salt, dairy products and bread, or that are naturally abundant in the micronutrient, such as seafood. Recommended daily iodine intake is 150 µg in adults who are not pregnant or lactating. Ingestion of iodine or exposure above this threshold is generally well-tolerated. However, in certain susceptible individuals, including those with pre-existing thyroid disease, the elderly, fetuses and neonates, or patients with other risk factors, the risk of developing iodine-induced thyroid dysfunction might be increased. Hypothyroidism or hyperthyroidism as a result of supraphysiologic iodine exposure might be either subclinical or overt, and the source of the excess iodine might not be readily apparent.

[Total thyroidectomy in patients with amiodarone-induced hyperthyroidism: when does the risk of conservative treatment exceed the risk of surgery?]

Amiodarone plays a pivotal role in the treatment of ventricular and supraventricular arrhythmias. However, amiodarone-induced hyperthyroidism (AIH) is one of the most feared complications, which necessitates interdisciplinary treatment and careful balancing of the risks of conservative treatment against those of total thyroidectomy. In this article we discuss the pharmacological aspects of amiodarone and its diverse effects on the thyroid. Furthermore, we present diagnostic and therapeutic strategies and report our positive experiences with total thyroidectomy in patients with AIH. Particularly in patients for whom continuation of amiodarone treatment is compulsory, a well-timed total thyroidectomy is a reliable therapeutic option, with minimal complication rates and immediate amelioration of symptoms.

An audit of amiodarone-induced thyrotoxicosis--do anti-thyroid drugs alone provide adequate treatment?

INTRODUCTION

Amiodarone is a widely used anti-arrhythmic drug. A common long-term complication is amiodarone-induced thyrotoxicosis (AIT). We examined retrospectively the efficacy of anti-thyroid drugs with or without prednisolone and the role of surgical thyroidectomy in the treatment of AIT in a single centre, in an iodine-replete region of Australia.

METHODS

A retrospective audit of patients with AIT was performed between 2002-2012 at this centre. Twenty-seven patients, mean age 60.9 ± 2.3 years were identified. Medical therapy (anti-thyroid drugs, prednisolone) was commenced according to the treating endocrinologist. The main outcomes were time to euthyroidism and number proceeding to thyroidectomy.

RESULTS

Of 11 patients commenced on anti-thyroid drugs alone, seven (64%) required the addition of prednisolone. Baseline free T4 was significantly higher in those ultimately treated with prednisolone (58.4 ± 6.3pmol/L) versus those not (31.7 ± 3.4pmol/L, P<0.05). Although similar results were seen with free T3, the difference was not significant (P=0.06). In patients with baseline free T4 <30pmol/L, 75% (3/4) achieved euthyroidism without prednisolone. Neither the use of prednisolone nor continuation of amiodarone significantly influenced time to euthyroidism. Eleven patients (41%) proceeded to surgical thyroidectomy, which was undertaken by an experienced surgical team without significant complications and no mortality.

CONCLUSION

Patients with AIT generally required glucocorticoids. Mild disease (free T4 <30pmol/L) may be successfully treated with anti-thyroid drugs alone. Surgical thyroidectomy is a safe and effective treatment for those refractive to medical therapy.

Managing thyroid dysfunction in selected special situations

Managing thyroid dysfunction is simple at first glance, the idea is to bring hormone levels in the euthyroid range, treat with antithyroid drugs, radio-iodine or surgery if toxic and replace with thyroxine or T3 if hypothyroid. Complexities arise when there are coexisting conditions that affect the thyroid or are affected by thyroid dysfunction and this review will deal with the special situations that need care when correcting thyroid hormone levels.