Introduction

Thyroid storm is a rare condition but can be life-threatening. It happens when the thyroid hormone is released excessively in large quantities from the thyroid gland, causing crises characterised by hyperthyroidism symptoms, including fever, irregular heartbeats, increased blood pressure, vomiting, diarrhoea and nervousness. This condition may also cause malfunctions in several organs of the body, like liver failure, heart failure, and central nervous system disturbances.¹ 

One of the harmful effects of the excess release of these thyroid hormones is that it significantly impacts the heart, which then causes complications like arrhythmias, heart failure, and hypertension.

How does thyroid storm change the body?

The thyroid storm plays a major role in several factors that change the body from its normal state of health, and this contributes to the impact it makes on the heart. These include:

Increase in thyroid hormone

Thyroid storm is a complication of an increased level of thyroid hormones, and this links to more free thyroid hormones, which are the T3 and T4 hormones that work in the body and are free from binding to proteins. This rise in these hormones can come from many reasons, like stress that cuts down thyroid hormone binding proteins or boosts the side conversion of T4 to T3.²

Increase in sympathetic tone

This state means that the part of the nervous system that "feels" for us is working extensively. This part also prepares one for the fight-or-flight response, making the body react more to thyroid hormones. This causes the activation of more beta-adrenergic receptors, and as a result, the heart releases more catecholamines like adrenaline.³

High sensitivity to thyroid hormones

The body tissues become more aware of and reactive to thyroid hormones. Consequently, the overactive metabolism and heart issues worsens.²

Cardiovascular effects and complications

Increased heart work and heart rates

Thyroid hormones boost the count of beta-adrenergic binding sites in the heart muscle. This results in more reactions to nerve signals. Hence, the heart beats faster and works more vigorously, which may cause fast heart rhythms and fluttering or irregular heartbeats.^4,5 In a severe thyroid crisis, heart rates can jump above 130 beats per minute, putting extra strain on the heart.⁶

Arrhythmias 

The highly overactive state that comes with thyroid storm can lead to heart rhythm issues in both the upper and lower parts of the heart. Atrial fibrillation, which is often seen, can lead to the heart stopping if it is not properly taken care of or immediate attention is not given to it right away.^4,7 The possibility of atrial fibrillation rises up sharply with a high level of thyroid hormone, even when it is a mild case of overactive thyroid.⁷ The increased responsiveness to thyroid hormones and stronger nerve action causes the heart rate to elevate. This can cause atrial fibrillation and other heart rhythm problems, greatly increasing the risk of the heart stopping in people experiencing thyroid storms.²

Heart failure

When the heart works too hard and too fast, it can lead to a type of heart failure called high-output heart failure. This type has a high preload and increased left ventricular work.⁷ Over time, this issue can lead to heart failure due to excessive pressure on the heart.⁵ Research shows that about 6% of people with thyrotoxicosis face heart failure, but this issue can be resolved with the right care. The high effort from the heart because of too much output can lead to high-output heart failure. If not quickly taken care of, this might turn into congestive heart failure.⁸

Hypertension 

Thyroid hormones boost the renin-angiotensin-aldosterone system, causing a higher force of blood against vessel walls, resulting in high blood pressure. On the other hand, the blood pressure when the heart is at rest could drop because of a weaker force of blood against the vessel walls, making the difference in beats more noticeable.^4,5 At the start, a thyroid crisis is usually observed with high blood pressure, also known as hypertension, due to a stronger push against vessel walls and the impact of thyroid hormones on the renin-angiotensin-aldosterone system. However, as the situation worsens, low blood pressure might be evident as the heart and blood vessels fail.¹

Heart remodelling and atherosclerosis

Persistent high levels of thyroid hormones can cause the heart to change, leading to thick walls and stiff areas, which might raise the chance of heart problems.

Research reveals more blocked heart pipes and harder artery walls in people with abnormally high levels of thyroid hormone than in those with normal levels.⁹

Diagnosis and evaluation

To find out if a person has a thyroid storm with heart issues, doctors usually do a full check-up and use scores, since there are no clear lab tests for this issue. They look closely for strong signs of high thyroid activity and linked heart problems.^8,10,11

Signs and symptoms

• Fast beats (over 140 per minute), shaky heartbeats, heart working irregularly, and high blood pressure
• Body signs: High temperature, upset, mixed-up thoughts, feeling sick, loose bowels.
• Delirium, agitation and seizures 
• Vomiting and diarrhoea

Scoring systems 

• Burch-Wartofsky point scale: This scale gives numbers for signs like fever, brain and stomach issues, fast heartbeat, full heart, odd beats, and what caused it all. A high score of over 45 suggests thyroid storm
• Japanese thyroid association criteria: This criteria mixes signs you can see with blood test results that show a high level of thyroid hormone
• Akamizu criteria: This criteria watches for signs like fever, fast heartbeat, full heart, and abnormal liver tests, as well as thyroid hormone levels

Laboratory tests

• Thyroid hormone levels: High free T4 (FT4) and free T3 (FT3) levels, with low or no TSH
• Heart signs: High troponin level, which may indicate heart stress or lack of blood flow
• Electrolytes and kidney function: Checking if electrolytes are balanced and within their normal range. Additionally, this method is required to check how well the kidneys work

Imagining and monitoring 

• Electrocardiogram (ECG): To check for odd heartbeats like atrial fibrillation
• Chest X-ray: To look for heart failure indications
• Regular monitoring: To monitor key health signs, like heart rate, blood pressure, and how much air is in the blood

Diagnostic strategies 

• Medical check: Mainly done by looking at signs and past cases of high thyroid levels
• Use of rating tools: To grade how severe the symptoms are and ensure accurate diagnosis
• Laboratory tests: To confirm that thyroid levels are indeed high and check heart health

Management Strategies

Blocking thyroid hormone production 

• Antithyroid medications: Propylthiouracil (PTU) or methimazole help suppress the production of thyroid hormone. PTU is preferred for more severe cases, as it can also block the conversion of T4 into T3¹²
• Iodine therapy: Iodine may be given after thyroid drugs to stop the excretion of thyroid hormone. It must be given at least one hour after thionamides to ensure effectiveness¹³

Managing heart complications

Managing arrhythmias 

• Beta blockers: Drugs like Propranolol or Esmolol help slow the heart rate and lower the effects of heart's stress hormone, such as adrenaline. They are key in reducing fast heart rates and high blood pressure⁸
• Antiarrhythmics: Drugs such as alcium channel blockers or Adenosine are options when beta blockers can't be used or are unable to work for heart rate issues such as atrial fibrillation

Managing heart failure 

• Diuretic: elps to eliminate extra fluid and ease swelling signs
• Vasodilators: They might help reduce heart strain and improve heart activity, but be careful as they may cause low blood pressure
• Close monitoring: Always observing heart activity is a must to ensure timely treatment and prevent further heart issues

Managing hypertension

• Antihypertensive: The type of drug to treat high blood pressure should fit the needs of the affected person, taking into account factors like other health issues and the limit of the drug
• Monitoring and adjustments: When the levels of thyroid hormone get back to normal, the plan for the administration of blood pressure drug might need to be modified to prevent abnormally low blood pressure⁴

Additional supportive care

• Hydrocortisone: Given to help with adrenal problems and prevent the conversion of T4 into T3
• Fluid and electrolytes management: IV fluids and salt fixes are key to stopping dehydration and electrolyte imbalance
• Addressing root causes: Finding and resolving the possible main issues, such as infections, is key to stopping thyrotoxicosis¹³

New therapies

• Plasmapheresis: Done in extreme cases to eliminate the thyroid hormones from the blood
• Bile acid binders: These can help to lower thyroid hormone levels by disrupting the gut-liver cycle¹³

Summary

A thyroid storm is a health crisis that requires quick attention. The heart issues experienced by those who have thyroid storms can be detrimental and may lead to death. It is important to notice and treat a thyroid storm when it is still in the early stage to avoid the adverse effects that may come with it over time. To manage it, you must monitor your heartbeat and blood pressure, as well as address heart issues and bring back thyroid levels to normal with the appropriate treatment.

In summary, a thyroid storm is a great risk to heart health, as it can cause uneven heartbeats, heart failure, and high blood pressure due to the high level of thyroid hormone. Getting assistance from an expert doctor is important to reduce these risks and improve heart health.