Arrhythmias
Sick sinus syndrome SSS
Sick sinus syndrome, also called sinus node disease, is a condition where the sinus node, the small area of tissue that acts as the heart's own natural pacemaker, is not functioning properly. Sometimes the node will send an impulse as it should, and sometimes it may not fire an impulse at all, or the impulses may be out of sync. Some patients notice symptoms such as palpitations and shortness of breath, and because the node is unreliable rather than permanently stopped, those symptoms often come and go.
What sick sinus syndrome is and what happens in the heart
Every heartbeat begins with an electrical signal generated in a small structure called the sinus node, or sinoatrial node. It is often described as the heart's natural pacemaker. From there the signal spreads through specialised pathways in the heart muscle, telling the chambers to contract in a coordinated sequence and push blood around the body. When this system works normally, the heart beats in a steady and reliable rhythm.
In sick sinus syndrome, also known as sinus node disease or SND, that node is malfunctioning. Sometimes it fires as expected. At other times it may not fire an impulse at all, or the impulses it produces may arrive out of sync with the rest of the conduction system.
Because the timing of every beat depends on that first signal, an unreliable sinus node makes the whole rhythm unreliable. Sick sinus syndrome sits within the group of conduction delays that Dr Jogiya treats, alongside conditions such as bundle branch block and atrioventricular heart block.
- The sinus node fires normally at some moments and not at others
- At times no impulse is produced at all
- Impulses that are produced may be out of sync with the rest of the conduction system
The symptoms you may notice
Some patients with sick sinus syndrome experience symptoms such as palpitations and shortness of breath. Because the node fires normally at some moments and not at others, those symptoms are usually intermittent rather than constant.
Where the sinus node is not generating signals properly, the heart can beat more slowly than normal. A slow heart rhythm reduces the amount of blood reaching the brain and other organs, which is why some people feel persistent fatigue or light-headedness, become breathless, or have episodes of fainting.
Symptoms that come and go can be easy to dismiss. A common pattern is that people wait until the episodes become more frequent before seeking advice. Early assessment is always preferable, because an intermittent rhythm is far easier to identify once it has actually been recorded.
- Palpitations
- Shortness of breath
- Persistent fatigue
- Light-headedness
- Fainting episodes
How it differs from atrial fibrillation
Sick sinus syndrome is not to be confused with atrial fibrillation or other atrial conditions. Those conditions refer mostly to an overactive or irregular atrial impulse, where the upper chambers of the heart fire chaotic or excessively rapid signals. Sick sinus syndrome refers mostly to a sinus node that is not functioning.
The distinction matters because it points treatment in a different direction. An overactive atrium is usually managed by controlling, slowing or resetting the rhythm. A sinus node that fails to fire needs support to keep the rate up instead, which is why the two conditions are treated so differently even though both can cause palpitations and breathlessness.
The link with tachy-brady syndrome
Many people with sinus node disease also experience tachy-brady syndrome. This is a phenomenon where the heart rate increases (tachycardia) and decreases (bradycardia) spontaneously, without any external influence. Normally the heart responds to its surroundings, so the rate rises during exercise and falls during sleep. In tachy-brady syndrome those swings happen on their own.
It is normally diagnosed as a period of bradycardia, meaning a low heart rate, with alternating spontaneous paroxysmal supraventricular beats. It occurs mostly alongside atrial fibrillation, and results from abnormal automated impulses being conducted through the atrial tissue. At least 50% of patients with sick sinus syndrome develop the alternating slow and fast rhythm known as tachy-brady syndrome.
Treatment for tachy-brady syndrome relates to whichever is the more serious problem. A lower heart rate will require a pacemaker to increase and regulate the impulses being delivered to the atria. Fast heart rates can be treated with medication, and sometimes a specialised pacemaker or an internal defibrillator may be implanted to regulate the heart rhythm and control fast rates.
How sick sinus syndrome is diagnosed
The diagnosis of heart rhythm issues is usually made with an ECG, or with a Holter monitor, which is a prolonged ECG recording, to get an understanding of the heart rhythm. Because sick sinus syndrome is intermittent by nature, a single tracing taken in clinic can look entirely normal, so Dr Jogiya will usually arrange a longer recording that captures a full day or more of activity and sleep.
Longer monitoring, event recorders and wearable technology are increasingly helping to pick up intermittent rhythm problems earlier. Capturing the heart rhythm during an actual episode is often what provides the answer.
An echocardiogram may also be used to assess the structure and function of the heart. Once treatment has started, regular ECGs will be conducted to ensure that treatment is successful and effective.
- An ECG to record the electrical activity of the heart
- A Holter or ECG monitor worn for 24 hours or longer to capture an intermittent rhythm
- An echocardiogram to assess the structure and function of the heart
How sick sinus syndrome is treated
The common treatment for sick sinus syndrome is a single chamber, or atrial, pacemaker. It regulates the impulses being sent from the atria to the ventricles and promotes regular cardiac function. Sometimes a dual chamber pacemaker is implanted instead, to further regulate and manage the heart rhythm in both the atria and the ventricles.
A pacemaker is a small device, usually about the size of a matchbox, implanted beneath the skin of the chest. It has a pulse generator, which holds the battery and the electronic circuitry, and one or more thin wires called leads that connect the device to the heart. It monitors the heart's own rhythm continuously and remains inactive while the heart beats normally, delivering a gentle electrical impulse only when the rate slows below a safe level. Many newer devices also raise the rate to match physical activity, so climbing stairs or walking up a hill feels more comfortable.
Implanting a pacemaker is a routine procedure and is usually carried out under local anaesthetic with light sedation. A small incision is made beneath the collarbone, the leads are guided through a vein into the heart using X-ray imaging for precision, and the device is then programmed to suit the individual's rhythm. Most patients return home within a day.
Modern pacemakers are highly reliable and designed to last many years before the battery needs replacing, and many can be monitored remotely, which avoids frequent hospital visits. Every patient's situation is different, so decisions about the device and its settings are always personalised. Many patients who struggled with dizziness or fatigue notice a significant improvement once their heart rhythm is stabilised.
When to seek help
Any persistent dizziness or unexplained fainting should be assessed by a medical professional. Closer attention is paid when symptoms happen during physical activity, when fainting occurs without any warning, or when light-headedness comes alongside palpitations, chest discomfort or breathlessness. Fainting that happens during exercise is always taken seriously and should be investigated promptly.
Call 999 if you have chest pain that is severe or does not settle, if someone collapses and does not come round, or if someone becomes unresponsive or stops breathing. Those situations need emergency assessment rather than a routine appointment.
For symptoms that are troubling but not an emergency, an appointment with Dr Jogiya allows the rhythm to be recorded properly and the cause investigated. Where an unreliable sinus node is confirmed, the treatment pathway is well established, and patients are usually able to return to their normal activities once the initial healing period has passed.
Where the figures on this page come from
Every figure above is quoted from one of these. This page is general information, not individual medical advice.
More in arrhythmias
Related conditions he treats.
- Atrial fibrillationAtrial fibrillation, commonly known as AF, is a condition where the atria, or upper chambers of the heart, fire chaotic electrical impulses. This leads the muscle to quiver, or fibrillate, instead of beat, so the heartbeat becomes irregular and is often faster than normal. It is one of the most common heart rhythm issues and around 1.7 million people in the UK have been diagnosed with it.
- Atrial flutterAtrial flutter is a heart rhythm problem that affects the upper chambers of the heart, known as the atria. Instead of beating at a normal pace, the atria beat rapidly, but in a regular and organised pattern rather than a chaotic one. Because the chambers do not have enough time to fill properly, blood is not pumped efficiently from the top chambers to the bottom chambers, which is what leads to shortness of breath.
- Atrial tachycardiaAtrial tachycardia is a fast heart rhythm that starts in the atria, the two upper chambers of the heart. An electrical signal emerges from another section of the atria and causes a rapid repeating beat, which means the atria beat very fast. It is one form of supraventricular tachycardia, or SVT, and short bouts of it can be common.
- Bundle branch blockBundle branch block describes a block in the part of the heart's conduction system known as the bundle branches. These branches carry the electrical impulse from the AV node down to each ventricle, and when one of them is blocked the signal reaches one side of the heart before the other, so the two ventricles no longer contract in step. It is a pattern picked up on an ECG, and mostly it is something monitored rather than actively treated.
- First degree heart blockFirst degree heart block is common, and it can affect anyone at any age. It describes a delay in the electrical signal as it travels from the upper chambers of the heart to the lower chambers, rather than a true blockage. Every signal still gets through, which is why many people notice nothing at all and why the condition is usually diagnosed when testing is being done for something else.
- Second degree heart blockSecond degree heart block is a fault in the heart's electrical wiring, not a blockage in an artery. Some of the electrical signals travelling from the upper chambers of the heart fail to reach the lower chambers, so a heartbeat is occasionally missed. There are two types, known as Mobitz I and Mobitz II, and they are treated very differently.
- Supraventricular tachycardiaSupraventricular tachycardia, usually shortened to SVT, is a fast heart rhythm that starts above the ventricles, in the upper part of the heart. Symptoms vary widely from one person to another, so some people are very aware of an episode while others barely notice one. Short bouts of SVT can be common, and can usually be treated very easily.
- Tachy brady syndromeTachy brady syndrome is a heart rhythm problem in which the heart rate increases and then decreases spontaneously, without any external influence. Instead of settling at a pace that matches what you are doing, the heart swings between periods of a slow rate and sudden bursts of a fast one. It is closely linked to sinus node disease, and it occurs mostly alongside atrial fibrillation.