The Heart Partners perform the full range of cardiac pacing and electrophysiology (EP) procedures. These include pacemaker insertion, ICD insertion, lead revision and generator changes. Furthermore, ablation procedures for palpitations (SVT) and atrial fibrillation are also performed. Most procedures are carried out as day-case procedures, or with a single overnight stay, at The Wellington Hospital in St John's Wood. The Heart Partners also offer detailed non-invasive assessment for coronary artery and heart valve disease with using cardiac CT, MRI and Echocardiography scans. In the event that coronary intervention is required (e.g. a stent or angioplasty), or cardiac surgery is needed, then our close contacts with excellent specialists in these fields ensure a seamless continuation of care. We are also able to recommend and refer to the most appropriate operator for your condition directly.
CARDIAC ELECTROPHYSIOLOGY STUDY
A cardiac electrophysiological study is a procedure which involves looking at the conduction system and abnormal rhythms of the heart. It is virtually always performed from the veins in the groin (the femoral veins) and between 2 and 5 small tubes or sheaths are placed within the veins, most commonly using both sides and through these sheaths small catheter electrodes are placed within the heart which allow us to measure the electrical signals from the heart and also to stimulate the heart. This allows us to measure conduction through the heart and we can also deliberately initiate abnormal rhythms, find extra pathways and so on. Most frequently this test is performed to look at tachycardias (fast heart beats), but occasionally is used to look at a slow heart beat. When investigating fast heart beats it is usually combined with a catheter ablation procedure (see below). The diagnostic part of the test is usually fairly rapid and is extremely safe but there is no procedure which is risk free.
Atrial fibrillation (AF) ablations tend to be much more complex than the other types of ablation and the risks are certainly increased over other forms of ablations but are sometimes extremely valuable procedures. Unlike other ablations, where a small pathway or tract of tissue is destroyed, AF can initiate from many different parts of the heart, especially from the “cuff” of atrial tissue surrounding the four pulmonary veins as they enter the back of the left atrium bring oxygenated blood from the lungs to the heart. Other foci include elsewhere in the left and also right atria and in the lower part of the superior vena cava (the large vein returning de-oxygenated blood to the heart from the upper body). Typically two large circles of radiofrequency ablation are made, each one isolating a pair of the pulmonary veins. These are made up of many individual spot ablations which link to form the exclusion zone. Because of the complex substrate and the need for large ablations, recurrence has been fairly common. If 30 lesions are made around a pair of veins, it only needs one of these to only temporarily damage the heart tissue and not permanently destroy it for recurrence to occur. However, the latest advances, such as 3D mapping, contact force sensing (when the catheter is able to "feel" whether it is sufficiently touching the heart wall to create an adiquate lesion), and improvements in the sheaths used to guide the catheters has improved the success rates.
A recent development has been the advent of balloon cryoblation. Here, a special cryo-balloon used to isolate each vein by freezing the tissue, rather than burning it. This is a much faster procedure than AF ablation by radiofrequency, and cases can usually be completed within an hour. Whatsmore, even if AF does come back, a second procedure is usually much simpler than when the first procedure was performed with RF ablation. This is because the "recurrence spots" only exist in one or two points, which can be precisely targeted, and time can be spent targeting other driving areas of abnormal tissue.
Nevertheless. succesful AF ablation is time consuming and requires the operator to perform many cases per week to be an expert. With the latest technology, we expect that 80% of patients will have their symptoms completely controlled following a single ablation for paroxysmal AF. Five year recurrences in patients stable and off drugs at one year is approximately 28%. Serious, permanant complications leaving are thankfully very rare. Howver, some complications including bleeding around the heart requiring drainage, temporary damage to one or more of the nerves which are important in breathing or nasty bleeding at the top of the leg, can occur in around 1 in 50 patients.
IMPLANTABLE CARDIOVERTER DEFIBRILLATOR (ICD)
An implantable defibrillator looks like a big pacemaker. They all incorporate pacemakers but the important feature of a defibrillator is that they are able to monitor and treat fast rhythms of the ventricle of the heart known as ventricular tachycardia and ventricular fibrillation which may be lethal. If a patient has a critical event the device will try to pace the heart very fast to overdrive the fast heart beat and if that fails a large shock is delivered (in some cases the shock is delivered as the first therapy depending on the clinical situation) and the patient’s heart is restored. These devices are larger, more complex and more expensive than pacemakers and typically last 5-8 years. They are only used in patients who have shown that they have either had or are at risk of having major cardiac rhythm disturbances. Most people with ICDs use Carelink.
CARDIAC RESYNCHONISATION THERAPY
CRT devices can be either pacemakers or most commonly defibrillators. A conventional pacemaker will pace the right atrium and right ventricle. These devices will pace the right atrium but will also pace both the left and the right ventricle. They do this using a third wire which is placed into a vein inside the heart called the coronary sinus which leads through to the musculature of the left ventricle. This leads to a more synchronised heart beat being produced than a conventional pacemaker but they are more complex devices.
They are typically used in patients who are suffering from heart failure with an ECG abnormality known as left bundle branch block and many patients such as this can be helped by biventricular pacing as part of cardiac resynchronisation therapy even if they don’t otherwise need a pacemaker. In addition, certain patients who are pacing the right ventricle most of the time, will do better with having a CRT device implanted to help preserve their muscle.
CARDIAC CATHETERISATION AND CORONARY ANGIOGRAPHY
In order to visualise the heart arteries and to make definitive diagnosis of coronary disease, and also in many cases with valve disease, an invasive test is needed. Under local anaesthetic, and usually intravenous sedation, a small tube (sheath) is placed in the artery or vein either at the top of the leg or in the wrist. Through these sheaths, catheters are passed to the heart chambers and to allow access to the coronary arteries. Pressures can be measured and iodine-containing x-ray dye injected into the chambers and arteries alloweing excellent visualisation of the vessels.
CATHETER ABLATION FOR SVT
A catheter ablation is a procedure in which small amounts of cardiac tissue are deliberately destroyed in order to terminate and prevent cardiac arrhythmias. Ablation is usually performed either with radiofrequency, which is a hot energy, a bit like diathermy, or cryo therapy which is a cold energy source. Radiofrequency is the most traditional form of energy that is used but cryo energy is sometimes used in atrial fibrillation ablation and I use it extensively in patients who have AV nodal re-entrant tachycardias (a form of SVT) because its effect is a little more gradual and if there is any risk of damaging normal conduction pathways, which can be very close to the abnormal, cryo energy allows you to stop ablating before any permanent damage has been done which can sometimes be difficult with radiofrequency. Rhythms that can be successfully ablated include atrial tachycardias, atrial flutter and atrial fibrillation, AV nodal re-entrant tachycardias, the Wolff Parkinson White syndrome and its variants and ventricular tachycardias. Procedural success rates for these procedures are very high and recurrence rates low.
REVEAL DEVICE INSERTION
These are small devices that are implanted through a tiny incision on the left side of the lower chest. It is a small operation taking about ten minutes. These devices will last 2-3 years and will monitor, on a loop, the heart rhythm throughout this time. If the device senses an abnormal slow or fast heart beat it will store it automatically but the patient also has a radiofrequency activator which can be used if they feel that they are suffering from their symptoms which can include collapse. The device will store quite a long ECG before over-writing it and so if the patient does collapse and wakes up a few minutes later there is still time to store that rhythm on the device. The devices are now minute, and are “injected” under the skin at the from of the chest near the breastbone. The readings from these devices can be interrogated by us using a radiofrequency programmer onto which the ECGs can be downloaded but more usually with a trans-telephonic system commonly known as CareLink.
A pacemaker is a small device that is implanted usually under local anaesthetic and placed underneath the skin or the muscle just below the clavicle (collarbone), most frequently on the left. This device is usually implanted to control a slow heart beat. The slow heart beat can originate from either the atrium or the ventricle or both and depending on the patient’s status either a single chamber device is used (typically in patients with atrial fibrillation with a slow ventricular rate) or a dual chamber device which is the most common sort used. There is also a CRT device – see below. The pacemaker will sense the heart’s intrinsic rhythm and if it is too slow in either chamber will produce a tiny electrical stimulus which isn’t detectable by the patient which will stimulate the heart allowing a normal heart beat to occur. They are battery driven and typically last 7-8 years. They are not generally used to control fast heart beats although sometimes by suppressing slow heart beats rebound tachycardias or fast heart beats can sometimes be prevented and in addition there are patients with slow heart beats and fast heart beats in whom a drug to help control rhythm disturbances would slow the heart too much and a pacemaker is needed to allow the drugs to be used.
Follow up of the devices is usually performed every six months or thereabouts by coming to see a specialist such as myself or by going to a physiologist (technician) run clinic. More frequently follow up is now done using a trans-telephonic remote follow up system such as Carelink and in our practice we will usually follow people up every two months by Carelink and see them every year in the consulting rooms. If problems occur downloads can be made at other times and when the batteries are getting near to the end of their life monthly follow up is usually used. One of the important features of modern pacemakers is their ability to store large amounts of data on the ECG and so if a patient has a clinical event such as a funny turn or collapse or a feeling of palpitations this will be recorded on the device and can be carefully examined afterwards which is extremely useful.