Abstract
Thyroid storm is a life-threatening condition which, in rare cases, may lead to cardiogenic shock and dysrhythmias. Mechanical circulatory support with an Impella device or extracorporeal membrane oxygenation may be used as a bridge to recovery in these cases. This case involves a patient with thyrotoxicosis and reduced ejection fraction and hemodynamic instability requiring Impella device placement. After treatment with methimazole, Lugol’s iodine, and hydrocortisone, he was weaned off mechanical circulatory support and made a full recovery. Mechanical circulatory support devices can be a useful bridging tool in reversible causes of cardiogenic shock, such as thyroid storm.
Keywords: Cardiogenic shock, cardiomyopathy, Impella, thyrotoxicosis
Thyrotoxicosis is a serious condition that can lead to high-output heart failure and possible cardiogenic shock.1 It usually presents with extreme symptoms of hyperthyroidism, including tachycardia, fever, hypotension, agitation, nausea, vomiting, and/or diarrhea. Thyroid function tests will show high free T4 and T3, with low thyroid-stimulating hormone. Treatment for thyroid storm includes beta-blockers, iodine solution, thionamides, and glucocorticoids.2 Complications of heart failure can potentially require temporary mechanical circulatory support (MCS) with an Impella device or extracorporeal membrane oxygenation (ECMO).1 In patients with hemodynamic instability, beta-blockers are avoided to prevent worsening of high-output cardiac failure. MCS can be a useful bridging tool during the treatment of reversible causes of cardiogenic shock, such as thyroid storm.
CASE PRESENTATION
A 55-year-old man with known hyperthyroidism, depression, and asthma presented to the emergency department with shortness of breath and weakness. He had been noncompliant with his methimazole due to lack of insurance and failure to follow-up. Initially he was afebrile, with a heart rate of 140 beats/min and blood pressure of 141/115 mm Hg. Laboratory results were significant for a brain natriuretic peptide of 1164 pg/mL (reference <100 pg/mL); troponin, 0.04 ng/mL (0.00–0.09 ng/mL); free T3, 6.4 nmol/L (1.6–3.9 nmol/L); and free thyroxine, 1.65 ng/dL (0.76–1.46 ng/dL). Electrocardiogram showed atrial flutter with 2:1 conduction. Imaging showed small bilateral pleural effusions but no evidence of pulmonary embolism. The patient received 60 mg of methimazole, three doses of 5 mg intravenous metoprolol, and 50 mg of oral metoprolol. He developed acutely worsening hypoxic respiratory failure requiring 15 L of oxygen by nonrebreather.
Upon admission to the medical intensive care unit for thyroid storm, the patient was started on methimazole, propranolol, Lugol’s iodine, and hydrocortisone and immediately went into pulseless electrical activity arrest. He had a total of three separate episodes of pulseless electrical activity arrest, for which there was immediate resuscitation for all events and return of spontaneous circulation. A bedside transthoracic echocardiogram showed a severely reduced ejection fraction of <10%. The ECMO team was consulted, but he was not deemed to be a candidate due to a Survival After Veno-Arterial ECMO score of −14, which put him at an 18% in-hospital survival rate. There were also limited resources in the hospital at that time due to an active surge of COVID-19 patients.
Due to ongoing hemodynamic instability and further discussion with the cardiac team, the patient ultimately underwent successful implantation of Impella CP (Abiomed; Danvers, MA) in an attempt to provide support during treatment of his thyroid storm. The right heart catheterization demonstrated elevated right- and left-sided heart pressures, and his atrial flutter was treated with cardioversion with successful conversion back to sinus rhythm. Within 6 hours of Impella placement, his hemodynamics improved (Table 1). While on the Impella device, his blood pressure and heart rate normalized and he was weaned off pressor support. By the third day, he was maintaining a cardiac index of approximately 3.0 with adequate mean arterial pressures, and the decision was made to extract the Impella device. The patient continued to recuperate without any further pulseless electrical activity as the thyroid storm resolved and he made a full recovery. When reassessed in 4 weeks, his ejection fraction had improved to 57%.
Table 1.
Hemodynamics at Impella implantation and 6 hours later
| Hemodynamics | At implantation | 6 hours later |
|---|---|---|
| Central venous pressure (mm Hg) | 12 | 4 |
| Pulmonary artery pressure (mm Hg) | 55/32 | 42/33 |
| Pulmonary artery pressure mean (mm Hg) | 40 | 30 |
| Cardiac output (L/min) | 3.2 | 6.1 |
| Cardiac index (L/min/m2) | 1.6 | 3.1 |
| Systemic vascular resistance (dyne*sec–5) | 1774 | 944 |
| Systemic vascular resistance index (dyne*sec–5/m2) | 3548 | 1857 |
DISCUSSION
Thyroid hormones have many effects on the cardiovascular system, and during thyrotoxicosis, these effects may be profound, with an increased heart rate and contractility.3 With prolonged hyperthyroidism, high-output heart failure may develop due to impaired left ventricular contractility and elevated left ventricular end diastolic pressure due to sustained tachycardia.4 About 6% of thyrotoxicosis patients may develop heart failure.5
Standard therapy for thyroid storm includes the use of beta-blockers to control increased adrenergic tone, thionamides to reduce thyroid hormone synthesis, iodine to reduce the release of thyroid hormone, and glucocorticoids to block peripheral conversion of T4 to T3.6 However, beta-blockers must be used with caution in patients with acute heart failure.
In rare cases, thyrotoxicosis-induced cardiomyopathy may require additional therapy such as MCS for successful recovery. MCS devices like the Impella CP can provide hemodynamic stability and protect the myocardium by increasing coronary flow and reducing end-diastolic pressure.7 One retrospective study showed that biventricular Impella devices can improve cardiac output and patient outcomes in various cases of cardiogenic shock.8 As evidenced by a single case report, patients who are not started on MCS in thyrotoxicosis-induced cardiogenic shock can have a high mortality rate.9 Further studies are needed to understand the true mortality rate of patients who do not have MCS in cardiogenic shock due to thyrotoxicosis.
Early detection and effective treatment of cardiogenic shock in patients with thyroid storm is essential for a favorable recovery and decreased mortality. Our case illustrates successful bridging support with Impella for the treatment of thyrotoxicosis-induced cardiomyopathy.
Disclosure statement/Funding
The authors report no funding or conflicts of interest. The patient gave consent for the case to be published.
References
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