Dr Louisa Malcolme-Lawes

Specialized in heart rhythm disturbances. Her NHS practice is based at Imperial College Healthcare NHS Trust and West Herts NHS Trust. She performs all types of catheter ablation and specializes in zero fluoroscopy ablation which is particularly beneficial in young patients or pregnant women wishing to avoid radiation exposure. She also performs all types of device implantation, including conduction system pacemakers and sub-cutaneous ICDs. She has special research interest in atrial fibrillation and the autonomic nervous system, and is undertaking the new technique of cardio neural ablation for vasovagal syncope at Hammersmith Hospital.

Cardiovascular • Circulatory system • Hypertension • Stress test

SYMPTOMS

Syncope

Syncope, commonly known as fainting, is a temporary loss of consciousness usually caused by a drop in blood flow to the brain. It often occurs suddenly and can be triggered by various factors, including:

Dehydration

Not having enough fluids in the body can lower blood pressure, leading to fainting.

Standing up too quickly

This can cause a sudden drop in blood pressure, known as orthostatic hypotension.

Emotional stress

Intense emotions such as fear or anxiety can trigger a fainting episode.

Heart problems:

Conditions like arrhythmias, heart valve disease, or heart failure can affect blood flow and lead to syncope.

Vasovagal response:

This is a common cause of fainting, where the body overreacts to certain triggers like the sight of blood or extreme emotional distress.

Chest pain

Chest pain can be a symptom of various conditions, some of which are serious. Common causes include:

Heart-related issues:

This includes angina (reduced blood flow to the heart), myocardial infarction (heart attack), arrhythmias leading to rapid heart rate, and pericarditis (inflammation of the outer lining of the heart).

Gastrointestinal problems

Conditions such as gastro-oesophageal reflux disease (GORD), oesophageal spasms, or peptic ulcers can cause chest pain.

Musculoskeletal issues

Pain from the muscles, bones, or joints in the chest wall, such as costochondritis (inflammation of the cartilage connecting the ribs to the breastbone), can mimic heart pain.

Lung-related conditions:

Pulmonary embolism (blood clot in the lung), pneumonia, or pleuritis (inflammation of the lining of the lungs) can cause chest pain.

Anxiety and panic attacks:

These can cause chest pain that is often sharp and accompanied by other symptoms like shortness of breath and palpitations.

If you experience chest pain, it is important to seek medical attention to determine the cause and receive appropriate treatment.

Palpitations

Palpitations are sensations where you feel your heart beating unusually fast, hard, or irregularly. They can be felt in your chest, throat, or neck and may be alarming, but they are often harmless. Common causes include stress, anxiety, caffeine, nicotine, or vigorous exercise. However, they can sometimes indicate an underlying heart condition, so it's important to discuss them with your doctor if they occur frequently or are accompanied by other symptoms like dizziness, shortness of breath, or chest pain.

Breathlessness

Breathlessness, or shortness of breath, can be caused by a variety of conditions, including:

Heart conditions:

Such as heart failure or arrhythmias, which affect the heart's ability to pump blood effectively.

Lung diseases:

Including asthma, chronic obstructive pulmonary disease (COPD), pneumonia, or pulmonary embolism.

Anaemia:

A condition where there are not enough red blood cells to carry oxygen around the body.

Obesity:

Excess weight can make breathing more difficult.

Anxiety:

Stress and anxiety can cause rapid, shallow breathing.

Infections:

Respiratory infections can lead to breathlessness.

If you experience persistent or severe breathlessness, it's important to consult a doctor to identify the underlying cause and receive appropriate treatment

Conditions

Atrial Fibrillation (AF)

Atrial fibrillation is a common heart condition where the heart beats irregularly and often rapidly. This irregular rhythm occurs because the upper chambers of the heart (the atria) beat out of sync with the lower chambers (the ventricles). This can lead to poor blood flow and various symptoms and in a small percentage of patients if left untreated can cause heart failure.

Symptoms

Palpitations (feeling of a fast, fluttering, or pounding heart)

Shortness of breath

Fatigue

Dizziness or light-headedness

Chest pain

Causes

AF can be caused by various factors, including:

High blood pressure

Heart disease

Thyroid problems

Excessive alcohol consumption

Stress

Sleep apnoea

Diagnosis

AF is typically diagnosed through an electrocardiogram (ECG), which records the electrical activity of the heart. Other tests may include blood tests, echocardiogram, or a Holter monitor.

Treatment

The treatment for AF aims to control the heart rate, restore a normal rhythm, and reduce the risk of stroke. Treatment options include:

Medications

Rate control medications: These help slow down the heart rate.

Rhythm control medications: These help restore and maintain a normal heart rhythm.

Anticoagulants: These are blood thinners that reduce the risk of stroke by preventing blood clots.

Cardioversion

This is a procedure where an electric shock is delivered to the heart to restore a normal rhythm.

Catheter Ablation

This is a minimally invasive procedure where areas of the heart causing the irregular rhythm are destroyed using radiofrequency energy.

Lifestyle Changes

Reducing alcohol and caffeine intake 
Managing stress 
Maintaining a healthy weight 
Regular physical activity

Supraventricular tachycardia – SVT

Supraventricular tachycardia (SVT) is a condition where the heart suddenly starts beating much faster than normal due to abnormal electrical signals in the upper chambers of the heart (atria). This rapid heart rate can cause symptoms such as palpitations, dizziness, shortness of breath, and chest pain. SVT episodes can start and stop suddenly and may last from a few seconds to several hours. It is on the whole a benign condition but symptoms can be very debilitating. Treatment options include medications, and in some cases, procedures to correct the abnormal electrical pathways in the heart.

Ventricular tachycardia

Ventricular tachycardia (VT) is a type of abnormal heart rhythm that originates in the ventricles, the lower chambers of the heart. It is characterised by a rapid heart rate, typically over 100 beats per minute, and can be life-threatening if not treated promptly. VT can cause symptoms such as palpitations, dizziness, shortness of breath, chest pain, and in severe cases, loss of consciousness. It is often associated with underlying heart conditions such as coronary artery disease, cardiomyopathy, or previous heart attacks. Treatment options for VT may include medications, catheter ablation, or implantable cardioverter-defibrillators (ICDs) to help regulate the heart's rhythm.

Vasovagal Syncope

Vasovagal syncope, also known as a fainting spell, occurs when your body overreacts to certain triggers, such as the sight of blood or extreme emotional distress. It is caused by a sudden drop in heart rate and/ or blood pressure, leading to reduced blood flow to the brain and resulting in a brief loss of consciousness. Symptoms may include light-headedness, nausea, sweating, and blurred vision before fainting. It is generally harmless and often does not require treatment, but identifying and avoiding triggers can help prevent future episodes. Please see STOP FAINTING website for an in-depth description and management strategies of vasovagal syncope.

For more information, visit the Stop Fainting website.

Heart failure

Heart failure, also known as congestive heart failure, is a condition where the heart is unable to pump blood effectively to meet the body's needs. This can result from various underlying conditions that weaken or damage the heart, such as coronary artery disease, high blood pressure, or previous heart attacks.

Symptoms of heart failure may include:

Shortness of breath, especially during physical activity or when lying down
Fatigue and weakness
Swelling in the legs, ankles, and feet
Rapid or irregular heartbeat
Persistent cough or wheezing with white or pink blood-tinged phlegm
Increased need to urinate at night
Swelling of the abdomen (ascites)
Sudden weight gain from fluid retention
Lack of appetite and nausea
Difficulty concentrating or decreased alertness

Heart failure can be managed with lifestyle changes, medications, and in some cases, pacemaker or defibrillator implantation, or surgical procedures. It is important to follow the treatment plan prescribed by your healthcare provider to manage symptoms and improve quality of life. Regular follow-up appointments are essential to monitor the condition and adjust treatment as necessary.

PROCEDURES

Cardioversion

Cardioversion is a medical procedure used to restore a normal heart rhythm in people with certain types of abnormal heartbeats (arrhythmias). It is often performed when the heart is beating too fast or irregularly, such as in atrial fibrillation or atrial flutter.

THERE ARE TWO MAIN TYPES OF CARDIOVERSION:

Electrical Cardioversion

This involves delivering a controlled electric shock to the heart through paddles or patches placed on the chest. The shock momentarily stops the heart's electrical activity, allowing it to restart in a normal rhythm. This procedure is usually done under sedation to ensure comfort.

Pharmacological Cardioversion

This involves using medications to restore the heart's normal rhythm. These medications can be administered orally or intravenously.

Cardioversion is generally a safe procedure, but like any medical intervention, it carries some risks, including the potential for blood clots, stroke, or other complications. Your doctor will discuss these risks with you and take steps to minimise them, such as prescribing blood thinners if necessary.  

The decision to undergo cardioversion will depend on your specific condition, symptoms, and overall health. Your cardiologist will provide detailed information and guidance tailored to your situation.

Atrial fibrillation ablation

Atrial fibrillation (AF) ablation is a medical procedure used to treat irregular heartbeats, specifically atrial fibrillation. The procedure involves using catheters inserted through the blood vessels to reach the heart. Once in place, the catheter delivers energy (such as radiofrequency or cryotherapy) to the areas of the heart causing the irregular rhythm. This energy creates small scars in the heart tissue, which help to block the abnormal electrical signals and restore a normal heart rhythm. The procedure is typically performed under sedation or general anaesthesia and may require a short hospital stay.

While AF ablation is generally safe, there are potential risks and complications associated with the procedure. These occur in around 2-3% of cases and may include:

- Bleeding or infection at the catheter insertion site.
- Damage to blood vessels as the catheters are threaded through them.
- Heart perforation or damage to the heart tissue.
- Blood clots, which can lead to stroke or other complications.
- Pulmonary vein stenosis, a narrowing of the veins that carry blood from the lungs to the heart.
- Oesophageal injury, which is rare but can occur due to the proximity of the oesophagus to the heart.
- Phrenic nerve injury, which can affect breathing.
- Arrhythmias, or new irregular heartbeats, which may require additional treatment.

Electrophysiology Studies and ablation of SVT

Electrophysiology (EP) studies are specialised tests used to assess the electrical activity and pathways of the heart. These studies help diagnose abnormal heart rhythms (arrhythmias) and determine the best treatment options. In some cases, an ablation procedure may be performed during the EP study to treat the arrhythmia.

Procedure:

1. Preparation:

You will be asked to fast for several hours before the procedure.
You may need to stop certain medications as advised by your doctor.
An intravenous (IV) line will be placed in your arm to administer medications and fluids.

2. During the Procedure:

The procedure is usually performed in a specialised lab called an electrophysiology lab.
You will be given a sedative to help you relax, but you will remain awake.
Small electrodes will be placed on your chest to monitor your heart's activity.
A local anaesthetic will be applied to numb the area where the catheters will be inserted, usually in the groin.
Thin, flexible tubes called catheters will be inserted through a vein and guided to your heart.
The catheters will record the electrical signals in your heart and stimulate your heart to reproduce the abnormal rhythm.

3. Ablation (if needed):

If an abnormal rhythm is identified, the doctor may perform an ablation.
Ablation involves delivering energy (such as radiofrequency or cryotherapy) through the catheter to create small scars in the heart tissue, which disrupt the abnormal electrical pathways.
The goal is to prevent the abnormal rhythm from occurring.

After the Procedure:

You will be monitored in a recovery area for a few hours.
You may need to lie flat for a period to prevent bleeding from the catheter insertion site.
Most patients can go home the same day, but some may need to stay overnight for observation.

Risks and Benefits:

Benefits:

Accurate diagnosis of arrhythmias.
Potential to cure certain types of arrhythmias with ablation.
Improved quality of life and reduced symptoms.

Risks:

Bleeding or infection at the catheter insertion site.
Damage to blood vessels or heart tissue.
Rarely, more serious complications such as stroke or heart attack.

Follow-Up:

You will have follow-up appointments to monitor your heart's rhythm and ensure the success of the procedure.
Your doctor will provide specific instructions on activity restrictions and medication adjustments.

Conclusion:

EP studies and ablation are valuable tools in diagnosing and treating arrhythmias. Discuss any concerns or questions with your doctor to ensure you are well-informed and comfortable with the procedure.

Flutter ablation

Flutter ablation is a medical procedure used to treat atrial flutter, a type of abnormal heart rhythm. During the procedure, a catheter is inserted through a vein in the groin and guided to the heart. Once in place, the catheter delivers radiofrequency energy to the area of the heart causing the abnormal rhythm. This energy creates a small scar, which blocks the abnormal electrical signals and restores a normal heart rhythm. The procedure is typically performed under local anaesthesia and sedation, and patients can usually go home the same day.

Ventricular tachycardia ablation

A ventricular tachycardia (VT) ablation is a medical procedure used to treat abnormal heart rhythms originating from the ventricles, the lower chambers of the heart. During the procedure, a catheter is inserted through a blood vessel and guided to the heart. Once in place, the catheter delivers energy to the areas of the heart muscle causing the abnormal rhythm, creating small scars that block the abnormal electrical signals. This helps restore a normal heart rhythm and can significantly reduce or eliminate episodes of VT. The procedure is typically performed under sedation or general anaesthesia, and patients may need to stay in the hospital for a short period for monitoring and recovery.

Pacemaker implantation

A pacemaker implantation is a procedure where a small electronic device called a pacemaker is placed under the skin of the chest to help manage irregular heartbeats. The pacemaker sends electrical impulses to the heart to ensure it beats at a regular rate and rhythm. This device is particularly useful for individuals with conditions such as bradycardia (slow heart rate) or heart block (a delay in the heart's electrical signals).

The procedure typically involves the following steps:

01. Preparation:
The patient is given a local anaesthetic to numb the area where the pacemaker will be implanted. Sedation may also be provided to help the patient relax.

02. Insertion:
A small incision is made near the collarbone. The pacemaker leads (wires) are then guided through a vein into the heart. These leads are connected to the pacemaker device, which is placed under the skin.

03. Testing:
The pacemaker is tested to ensure it is working correctly and effectively regulating the heart's rhythm.

04. Closure:
The incision is closed with stitches, and a dressing is applied.

After the procedure, the patient will be monitored to ensure the pacemaker is functioning properly. Instructions will be provided on how to care for the incision site and any activity restrictions to follow during the recovery period. Regular follow-up appointments will be necessary to check the pacemaker and make any necessary adjustments.

Transvenous Implantable Defibrillator (ICD)

Transvenous ICD (Implantable Cardioverter Defibrillator) implantation is a procedure used to treat patients at risk of sudden cardiac arrest due to life-threatening arrhythmias. The device is implanted under the skin, typically below the collarbone, and connected to the heart via leads that are threaded through the veins.

The procedure involves the following steps:

01. Preparation:
The patient is given local anaesthesia and sedation to ensure comfort during the procedure.

02. Insertion of Leads:
Leads are inserted through a vein, usually the subclavian vein, and guided to the heart using fluoroscopy (a type of X-ray).

03. Positioning of Leads:
The leads are positioned in the right ventricle and sometimes the right atrium. Their placement is confirmed through imaging and electrical testing.

04. Connection to ICD:
The leads are connected to the ICD device, which is then placed in a pocket created under the skin.

05. Testing:
The ICD is tested to ensure it can detect and treat arrhythmias effectively.

06. Closure:

The incision is closed with sutures, and a dressing is applied.

Post-procedure, the patient is monitored for any complications and given instructions on how to care for the incision site and manage the device. Regular follow-up appointments are necessary to check the device's function and battery life.

Sub-Cutaneous Defibrillator (S-ICD)

A fully subcutaneous implantable cardioverter-defibrillator (S-ICD) is a device designed to monitor and regulate heart rhythms, particularly in patients at risk of sudden cardiac arrest. Unlike traditional ICDs, the S-ICD is implanted entirely under the skin, without the need for leads to be placed inside the heart or blood vessels.

The procedure involves the following steps:

01. Preparation:
The patient is given local anaesthesia and sedation to ensure comfort during the procedure.

02. Incision and Pocket Creation:
A small incision is made on the left side of the chest, just below the armpit. A pocket is then created under the skin to house the S-ICD device.

03. Lead Placement:

A single lead is tunnelled under the skin from the incision site to the sternum (breastbone). This lead is positioned to detect the heart's electrical activity and deliver shocks if necessary.

04. Device Connection:

The lead is connected to the S-ICD device, which is then placed into the pocket created earlier.

05. Testing and Closure:

The system is tested to ensure it functions correctly. Once confirmed, the incision is closed with sutures, and a dressing is applied.

The S-ICD continuously monitors the heart's rhythm and can deliver a shock to restore normal rhythm if a life-threatening arrhythmia is detected. This device is particularly beneficial for patients who require defibrillation but do not need pacing therapy.

Cardioneural Ablation

Cardioneural ablation is a medical procedure aimed at treating certain types of heart rhythm disorders, particularly those that are influenced by the autonomic nervous system. This procedure involves the targeted destruction of specific nerve pathways that contribute to abnormal heart rhythms. By ablating these nerves, the procedure can help to stabilise the heart's electrical activity and reduce the occurrence of arrhythmias. It is typically considered when other treatments, such as medications or lifestyle changes, have not been effective. The procedure is performed by a cardiologist and may involve the use of catheters and advanced imaging techniques to precisely target the problematic nerve areas.

"Many thanks for the excellent care you and your team gave me during the AT ablation procedure at Hammersmith Hospital last friday. You have a calm and reassuring demeanour, and an impressive collective competence. For that many thanks.”

-Mr RM April 2025

Dr Louisa Malcolme-Lawes see private patients at Hammersmith Hospital and One Welbeck.

Research & Publications

As an Honorary Clinical Lecturer at Imperial College Dr Malcolme-Lawes continues to be closely involved in ongoing research studies and is Principle Investigator at West Herts NHS Trust for the Protect HF study which is a national study of conduction system pacing being run by Imperial College. She also participates in research activities within Imperial College including student vivas and teaching programs, regularly teaching on the BCS Mayo Clinic Cardiology Board Review Course.

Catheter Ablation for Vasovagal Syncope: The Therapeutic Potential of Gateway Plexi.

Machine learning-derived cycle length variability metrics predict spontaneously terminating ventricular tachycardia in implantable cardioverter defibrillator recipients.

Ectopy-triggering ganglionated plexuses ablation to prevent atrial fibrillation: GANGLIA-AF study.

Long-term outcomes of ganglionated plexus ablation as sole therapy for paroxysmal atrial fibrillation.

Artificial intelligence-enabled electrocardiogram to distinguish atrioventricular re-entrant tachycardia from atrioventricular nodal re-entrant tachycardia.

Postinfarct ventricular tachycardia substrate: Characterization and ablation of conduction channels using ripple mapping.

Characterization of conduction system activation in the postinfarct ventricle using ripple mapping.

Feasibility of mapping and ablating ectopy-triggering ganglionated plexus reproducibly in persistent atrial fibrillation.

Targeting the ectopy-triggering ganglionated plexuses without pulmonary vein isolation prevents atrial fibrillation.