What Is Junctional Escape Rhythm

Overview

A junctional escape rhythm refers to an abnormal rhythm of your heartbeat caused by an issue with the electrical conduction system within the heart.¹ Under normal conditions, our heartbeat is controlled and initiated by a bundle of cells located towards the top of our heart. This bundle of cells is known as the sinoatrial node (SA node). In healthy individuals, the SA node is constantly generating what is known as an action potential.² The term action potential refers to the change in voltage across a cell when specific ions (such as sodium and potassium) move across their membrane.³ This action potential then travels along the electrical conduction system of the heart as an electrical signal before reaching what is known as the atrioventricular node (AV node). This is located between the two bottom chambers of the heart (the ventricles) and is responsible for slowing conduction of this signal so that the ventricles have sufficient time to fill with blood. Following this, the electrical signal will then travel to the ends of the ventricles before causing them to contract and squeeze the blood out. 

This established process in healthy individuals is what gives rise to a regular, resting heart rate of 60–100 beats per minute (BPM). The ability of the SA node to spontaneously generate its own action potentials is what gives it its name as our ‘natural pacemaker’.² When the SA node is damaged or working incorrectly, command over the electrical conduction system is often given to either the AV node or the conduction tissue that runs between the two ventricles (the Bundle of His).¹ Such a process is called a ‘junctional escape rhythm.’ As we have discussed, the AV node is mainly responsible for slowing the conduction of this electrical signal. As such, if the generation of the electrical signal is caused solely by the AV node, patients can often expect to experience a resting heart rate between 40–60 BPM. 

Causes of junctional escape rhythm

When the activity of the SA node is blocked, or when its rate of generation is slower than that of the AV Node or Bundle of His, patients can expect to develop a junctional escape rhythm.¹ There are numerous conditions associated with the development of a junctional escape rhythm¹ and these include: 

• Chest trauma
• Sick sinus syndrome
• Collagen vascular disease
• Myocarditis 
• Neuromuscular disorder
• X-linked muscular dystrophy
• Carotid sinus hypersensitivity 
• Hypothyroidism 
• Sleep apnoea 
• Hypoxia 
• Intracranial hypertension
• High Levels of Potassium in the Blood (Hyperkalaemia) 
• Anorexia nervosa 
• Amyloidosis 
• Pericarditis 
• Lyme disease
• Rheumatic fever 
• Ischaemic heart disease
• Acute myocardial infarction
• Acute and chronic coronary artery disease
• Inherited channelopathy  

There are also a number of medications which are known to predispose patients to developing a junctional escape rhythm¹ and these include: 

• Clonidine  
• Adenosine 
• Cimetidine 
• Antiarrhythmics class I to IV 
• Lithium 
• Amitriptyline 
• Beta-blockers 
• Calcium-channel blockers
• Digoxin 
• Ivabradine 
• Opioids 
• Cannabinoids 

There are also some therapies and interventions which can lead to the development of a junctional escape rhythm¹, including: 

• Radiotherapy 
• Repair of congenital heart disease

Signs and symptoms of junctional escape rhythm

As mentioned previously, those with a junctional escape rhythm will often experience a heart rate between 40–60 BPM. However, the type of junctional escape rhythm can be classified further depending on the heart rate exhibited by affected patients.¹ These classifications are as follows: 

• Junctional Bradycardia: a heart rate below 40 BPM
• Junctional Escape Rhythm: a heart rate between 40 and 60 BPM
• Accelerated Junctional Rhythm: a heart rate between 60 and 100 BPM
• Junctional Tachycardia: a heart rate of over 100 BPM

Other than an altered heart rate, some patients may experience no symptoms at all. It is also important to note that the symptoms of a junctional escape rhythm most typically depend on the underlying cause of the syndrome.¹ For example, in those patients with rheumatic fever, patients will most typically present with a fever, pains in their joints, a rash, and a heart murmur due to the damage caused by the disease.¹ A junctional escape rhythm will then often be an incidental finding when investigated by your healthcare professional. However, there some symptoms which may be experienced by those with a junctional escape rhythm¹ and these include: 

• Dizziness or dizzy spells 
• Fatigue 
• Syncope (fainting) 
• Palpitations 
• An alternating heart rate, i.e., the heart rate will swing from very low to very high sporadically. 

Management and treatment of junctional escape rhythm

Management of a junctional escape rhythm is often directed by the underlying cause of the syndrome. In those patients that are healthy, without symptoms and without significant impairment, treatment is often not indicated. Such cases are often seen in the younger populations, whereby frequent exercise and fitness can often lead to a normal and expected lowered heart rate.¹ 

In the case of junctional escape rhythm caused by digoxin toxicity, 

patients are often treated with atropine. 

In Children with persistent and symptomatic junctional escape rhythm, percutaneous radiofrequency ablation is often indicated. This is a process whereby surgeons will use heat to generate small scars within the heart muscle to prevent the conduction of abnormal electrical signals.⁴ 

If the junctional escape rhythm is caused by sick sinus syndrome, a permanent pacemaker is often the solution. This device will then assume the role of the dysfunctional ‘natural pacemaker.’ 

Diagnosis

Before conducting any tests to diagnose a junctional escape rhythm, your healthcare provider will first ask you a series of questions relating to the symptoms you have been experiencing. This process is what is known as obtaining a ‘medical history.’ Details of your symptoms, medications and previous medical history will help your healthcare professional to narrow down the list of possibilities. Following this, your healthcare professional may then conduct a physical examination whereby they assess the heart and vessels around it. If suspicion is raised, your healthcare provider will then order the following tests¹ to confirm their diagnosis:

• ECG: Assessment of your ECG will allow your healthcare professional to identify a junctional escape rhythm. Your healthcare professional will be looking for the absence or irregularity of what is known as a P-wave.⁵ As all four chambers will be contracting at approximately the same time, absence of a P wave is often indicative of a junctional escape rhythm. 
• Blood tests 

Echocardiography: The use of an echocardiogram will allow your healthcare provider to detect any structural abnormalities within the heart that may be causing the junctional escape rhythm. 

FAQs

How can I prevent junctional escape rhythm? 

There are numerous causes which can lead to the development of a junctional escape rhythm. If you develop a junctional escape rhythm attributable to a drug you are taking, your healthcare provider will often take immediate action to change this. The avoidance of recreational drugs such as opioids and cannabinoids can also reduce your chance of developing a junctional escape rhythm. 

How common is junctional escape rhythm?

As junctional escape rhythm is a common occurrence amongst those with Sick Sinus Syndrome (SSS), its incidence is thought to be synonymous with the occurrence of SSS. Using this measure, we can see that 1 in every 600 cardiac patients in the USA has SSS,¹ and it is therefore likely to be a similar number for junctional escape rhythm. 

What can I expect if I have a junctional escape rhythm?

As we have discussed, it is common for most patients not to notice any symptoms. This is especially true in those that are young. Importantly, the prognosis for junctional escape rhythm is very good, with most symptoms abating after treatment. 

When should I see a doctor? 

If you notice any of the symptoms we have discussed, or are feeling particularly unwell with episodes of fainting or dizziness, then you should contact your doctor immediately. Should you require a pacemaker, your doctor will organise frequent check-ups to ensure the pacemaker is working adequately and that there are no associated complications from its insertion. 

Summary

A junctional escape rhythm is a condition caused by an abnormality within your heart’s electrical conduction system. Caused by a number of medical conditions, medications and interventions, dysfunction of the SA node can often lead to the AV node assuming control of your heart’s electrical conduction. This results in patients experiencing a lower than normal heart rate. It is important to note that the symptoms of a junctional escape rhythm are often masked by the underlying cause and thus its presence may be found incidentally upon investigation. Where there is no clear cause, some patients report experiencing symptoms relating to dizzy spells, fatigue and fainting. Treatment of a junctional escape rhythm is also dependent on its cause, with doctors often withdrawing causative medications or resorting to surgical interventions in the cases of sustained symptomatic presentation. Diagnosis typically consists of a medical history, physical examination and a number of tests including an ECG.