Introduction

When we talk about heart problems linked to diabetes (high blood sugar), it is not just about artery blockages and heart attacks. Elevated blood sugar levels can affect the heart's normal, steady rhythm, causing atrial fibrillation, a condition linked to damage in the heart's upper chambers, known as the atria.

According to the World Health Organisation, high blood sugar contributed to about 11% of cardiovascular mortality worldwide in 2021.¹

We will examine how spiking blood sugar levels can alter the heart's structure and scramble the signals that normally keep the heart's rhythm steady, and why this is a growing concern. We will also explore the connection between diabetes and persistent atrial fibrillation, a common and sustained type of irregular heart rhythm affecting the upper chambers of your heart, and how excess blood sugar remodels the heart tissue in ways that promote this condition.

What is atrial fibrillation?

Atrial fibrillation (AF) is a type of heart disease that occurs when the normal rhythm in the upper chambers of the heart, or the atria, becomes irregular, causing the heart to beat too rapidly. This in turn impedes blood flow out of the atria, where they pool and can form dangerous clots. When a blood clot forms, it can get dislodged from the heart and reach the brain, causing a stroke.²

Atrial fibrillation is associated with a four- to five-fold increase in the risk of developing stroke.³ The presence of diabetes can further enhance the established risk. More specifically, type 2 diabetes, a variant affecting the older age groups, is associated with a 70% relative increase in the risk of stroke for patients with AF.⁴

A person with AF may sometimes not show any symptoms, and their condition can be detected only through a physical exam. Others may have one or more symptoms such as general tiredness, chest pain, shortness of breath, rapid and irregular heartbeat, severe sweating, and dizziness.²

There are different patterns of atrial fibrillation, which include:²

• Paroxysmal: When episodes stop within 2-7 days
• Persistent: Episodes last longer than 7 days
• Long-standing persistent: Atrial fibrillation has been present for more than a year, either due to the failure of cardioversion, a therapy meant to reset the heart rhythm, or because medicines were not initiated
• Permanent AF: It is the type where the rhythm is unresponsive and hence no treatment is attempted
• Non-valvular AF: Irregular heart rhythm not caused by severe valve issues such as rheumatic valve disease or having an artificial (prosthetic) heart valve

How diabetes increases the risk of persistent AF

Diabetes has been identified as a major risk factor for serious heart-related problems.⁴ This chronic health condition, which occurs when your blood sugar levels are elevated, is present in one out of nine adults globally, and the figures are predicted to increase by 46% by 2050.⁵

In the diabetic population, inflammatory markers such as C-reactive protein, TNF-α (tumour necrosis factor-alpha), and interleukin-6 are significantly elevated, and these contribute to the enlargement of the left atrium and increased occurrence of AF.⁴ Hence, they develop persistent or permanent AF more often than those without diabetes.⁶

How high blood sugar remodels the atria

Several mechanisms explain how high blood sugar levels contribute to changes in the heart muscle:

Structural changes

High blood glucose can trigger inflammation and lead to buildup of certain undesirable compounds such as advanced glycation end products (AGE), reactive oxygen species (ROS), and growth factors (TGF-β) that decrease the elasticity of the heart muscles by causing atrial fibrosis. This causes the atria to become stiffer, and consequently limits their ability to store blood. Secondly, the atria can become enlarged, which is a significant factor in the development of AF.^3,4

Electrical changes

People with impaired glucose regulation may present with altered ion channels and junctions in the heart, which are key to the smooth transmission of electrical signals across the heart tissue. This abnormal signal conduction can lead to arrhythmias (irregular heartbeat).⁷

Autonomic remodelling

A stable heart rhythm requires a balance of the sympathetic and parasympathetic nerves that control the heart. This balance can be disrupted in diabetes, resulting in remodelling of the atria and development of AF.^4,7

The vicious cycle

While poor sugar control tends to cause atrial damage, the inverse relationship has also been postulated. Once AF sets in, it can form clots and impair blood flow through smaller blood vessels supplying body organs. Over time, this impairs the functioning of organs like the pancreas, which is responsible for glucose regulation in the body, and increases the risk of diabetes. So diabetes and atrial fibrillation are speculated to have a bidirectional relationship.⁸

Complications

Studies suggest that those with diabetes experienced a higher burden of AF symptoms, along with heart failure and disease progression. Their overall health status is reportedly worse, and they have a significantly higher risk of mortality and hospitalisation, further escalating healthcare expenses.⁶

Patterns

Individuals showing wide blood sugar variations have a higher risk of developing AF than those with long-term increased blood sugar levels. This is because glucose fluctuations potentially release excess free radicals that harm your heart cells. This means an effective management strategy should aim to prevent glucose variations and not just reduce the blood sugar levels.⁴

What can help

The management of individuals suffering from both diabetes and atrial fibrillation demands a multifaceted and personalised approach. This may include strategies to control blood sugar levels using antidiabetic medications. Other therapeutic recommendations often include blood thinners that decrease the clotting tendencies in persons with AF to prevent the risk of stroke.

Early rhythmic management is essential in reducing the burden of AF consequences. Rhythm control can be achieved with antiarrhythmic medications as well as modern approaches like catheter ablation, a procedure where a catheter is used to destroy small areas of heart tissue that generate abnormal electrical signals.

Incorporating lifestyle changes such as regular exercise, weight control, dietary modification, smoking cessation, alcohol reduction, stress management, and sleep hygiene is beneficial for both glucose control and reducing AF symptom burden.

Certain medications like GLP-1 receptor agonists, sodium-glucose cotransporter-2 (SGLT2) inhibitors, metformin, thiazolidinediones, and dipeptidyl peptidase-4 (DPP-4) inhibitors have demonstrated protective effects on the heart. However, the prescription of these medicines must be tailored to the individual's needs and medical profile due to possible side effects of these medications.

Ultimately, the comprehensive care of such individuals demands a collaborative effort between healthcare providers to improve their quality of life and mitigate adverse outcomes.⁹

When to see your doctor

Managing both diabetes and atrial fibrillation means staying alert to changes in your body. Contact your healthcare team promptly if you notice any of the following:

• New or worsening heart symptoms: Heart palpitations (a racing, pounding, or fluttering feeling) that are stronger, last longer, or feel different than usual
• Increased shortness of breath, dizziness, or unusual fatigue with everyday activities
• Chest discomfort, pressure, or pain
• Problems managing your blood sugar: Low blood sugar (hypoglycaemia) that is more frequent, severe, or harder to treat
• Persistent high blood sugar along with symptoms like extreme thirst, frequent urination, or nausea
• Possible medication side effects: Unusual bleeding or bruising (a concern if you are on a blood thinner)
• Persistent nausea, dizziness, or skin rashes
• Before any medical or dental procedure, including minor surgeries, so your doctors can manage your blood thinners and blood sugar
• Before starting a new intense exercise programme or making a major change to your diet
• Any significant, unexplained change in your weight

FAQs

How can I prevent atrial fibrillation if I am living with diabetes?

Ensure that your blood sugar, blood pressure, and weight are under control. Regular exercise, limited alcohol intake, and proper sleep also help keep your heart's rhythm stable. Managing stress and taking your prescribed medications further reduce the chances of AF developing.³

Are there medications that both control diabetes and protect the heart?

Certain medications like SGLT2 inhibitors, GLP-1 receptor agonists, and metformin have cardioprotective effects and may reduce the risk of AF.

What is persistent atrial fibrillation?

Persistent atrial fibrillation occurs when the abnormal heart rhythm you experience lasts for more than a week and doesn't stop on its own. It requires medical treatment to reset the heart rhythm.

Summary

Diabetes significantly influences the heart's structure and rhythm system, increasing the risk of atrial fibrillation. The combination is associated with a reduced quality of life and translates into a higher likelihood of developing heart-related complications, incurring greater healthcare costs. Such complexities emphasise the need for personalised risk assessment, proactive interventions, and holistic management strategies to address the growing concern.

Once AF sets in, it can worsen blood flow, which in turn worsens glycaemic control. Poor sugar control then feeds back into more atrial damage, creating a self-reinforcing loop.

The therapeutic landscape encompasses a range of options, from prescribing medications to rhythm control and lifestyle modifications. Individualised treatment plans that consider each patient's unique characteristics and preferences are crucial to achieving optimal outcomes. Early intervention and collaborative care are essential for improving outcomes and preventing complications.