Patients are often referred for cardiac review with symptoms which could represent rhythm abnormalities, and the mainstay of cardiac electrophysiology is diagnosis of these issues using non-invasive methods. Many patients will undergo ECG assessment; some will require Ambulatory heart rate monitoring or exercise tolerance testing. In some circumstances, tilt table testing can be used in an attempt to provoke symptoms and diagnose issues.
Drug provocation testing is used in rare cases where there is a strong suspicion of arrhythmic disease (particularly in genetic conditions) but where baseline testing has proved normal.
These tests are mostly performed on an outpatient basis and represent the majority of the workload of diagnostic electrophysiology. In general, these assessments can initially be arranged by general paediatric cardiologists, but in cases where the results are abnormal or equivocal it is important to arrange for expert electrophysiology review. In cases where the non-invasive testing demonstrates abnormalities of cardiac conduction, many can be treated medically without the need for invasive therapy. In cases where medical therapy is not effective or not appropriate, the electrophysiologist may plan further strategies for treatment.
Inherited Cardiac Conditions
There are some rare cardiac conditions with a genetic basis that cause issues with heart rhythms, the most well-known examples of these being Long QT syndrome and Brugada syndrome. Other structural cardiac abnormalities such as Hypertrophic Cardiomyopathy can also cause heart rhythm issues and therefore are often reviewed by electrophysiologists.
Frequently, arrhythmia experts are asked to screen family members when a patient is identified as suffering from one of these genetic conditions (or when a family member has died suddenly but with no identifiable cause). This screening often involves a combination of non-invasive testing and drug provocation challenges and can also involve formal genetic testing if abnormal genes have previously been identified within the family.
Often, even if initial testing proves normal the patients are followed up as some conditions do not demonstrate abnormalities until patients are more mature. This requires close working with adult electrophysiology, as many patients will need to be transitioned to adult services for further follow-up.
Most regions support joint working where cardiologists and geneticists work side-by-side in combined clinics to provide the expertise to manage these patients in a streamlined manner.
In most paediatric cases, invasive EP studies are performed under general anaesthesia, although in some older children and adolescents it is possible to use a combination of local anaesthetic and sedation.
Sheaths are inserted to the central veins (similarly to cardiac catheterisation) and electrical wires are passed through the veins into the chambers of the heart. Electrical stimulation is then performed, and an electrical map of the heart is created to allow for potential short-circuits or other conduction abnormalities to be identified. If abnormalities are identified, the use of either radio-frequency ablation or cryo-ablation can allow disruption of the abnormal conduction tissue. In the majority of cases with purely electrical abnormalities, this leads to a normalising of cardiac conduction and a cure of the condition.
In patients who have undergone previous cardiac surgery, where the anatomy is abnormal or where post-operative scarring exists within the heart, treatment of early or late post-operative arrhythmias can promote better cardiac function and reduce long term morbidity, hospitalisation and can even prolong life.
These invasive cases utilise a combination of X-ray angiography and 3 dimensional computerised mapping systems, with many centres also using ultrasound to guide access to central veins or trans-septal left atrial access if required.
Some congenital heart centres will provide invasive EP services to the regional Adult Congenital Heart disease service, often in combination with the local adult electrophysiology teams. Again, a close multidisciplinary working method is required.
Arrhythmia Device Implantation
In cases where non-invasive testing have demonstrated heart rates that are too slow or too fast, causing patient symptoms, or in some post-operative situations where there is evidence of heart block, an implantable arrhythmia device may be indicated.
These devices are implanted by electrophysiologists, and include both pacemakers and cardioverter defibrillators. There are also devices which can be implanted to record rather than treat heart rhythm issues where the diagnosis is not possible to make from non-invasive recordings. These implantable loop recorders are useful in cases where longer term monitoring is required, or when episodes which could represent cardiac rhythm dysfunction occur too infrequently to assess with standard monitoring systems.
In the majority of cases, these cardiac devices are implanted under general anaesthesia, and require knowledge of pre and post-operative congenital cardiac anatomy to ensure the accurate and appropriate positioning of leads within the heart. Devices are then programmed with specific treatment parameters for the patientís individual condition, in collaboration with highly specialised cardiac physiologists.
Once patients have undergone implantation of devices, there is a need for specialised follow-up to ensure that the electrical aspects of their treatment remain appropriate for their specific condition. Often patients will require medical therapy as an adjunct to their device (particularly in patients where defibrillators are implanted).
The device battery levels and lead integrity also need to be monitored to diagnose issues and plan replacement devices if the need arises.
These patients are seen in specialised clinics and the electrophysiologists are involved in ensuring the safe ongoing care of patients, often in tandem with a team of cardiac physiologists who have expertise in device therapy.
All centres with Congenital Electrophysiology services submit procedural data to national databases for device therapy and electrophysiology cases. In a similar way to other catheter data, this is freely available for review, and the submitted data is audited yearly to ensure accuracy through a series of individual unit visits performed by the national audit team. Visit NICOR website
Paediatric Cardiology trainees in the UK undertake a 2 stage period of training commencing at ST4 level, to which there is competitive national recruitment. Following appointment to the post, trainees spend 3 years (ST4-6) training in general paediatric cardiology, within which there is a defined programme of exposure to non-invasive and invasive electrophysiology. Those trainees who demonstrate an interest and aptitude for Electrophysiology then progress into Higher Specialist Training (ST7-8) and spend 2 years focusing on this aspect of cardiology (whilst maintaining their general paediatric cardiac expertise through inpatient and outpatient work).
All centres which perform Congenital Cardiac Surgery will have at least one defined specialist Consultant Electrophysiologist, who will oversee the training. Within this 2 year period, trainees are required to spend a period of at least 6 months seconded to an Adult Electrophysiology unit, as it is recognised that most Congenital centres will provide low volumes of cases for device implantation in particular and the higher volume of adult cases allows the opportunity for a greater degree of experience to be gained in a shorter time frame.
Many trainees will opt to spend a period of training in an international centre, which may occur either during or following the formal period of defined UK training. Many trainees will go on to seek further experience following the award of their CCT in Paediatric Cardiology prior to taking up a substantive consultants post.
Following appointment, there is an on-going requirement for training and continuing education throughout a consultantís career, and an informal national network of electrophysiologists exists to provide review of difficult cases and to support national working.
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[Content provided by Dr Dominic Hares, Consultant Paediatric Cardiologist, Leeds General Infirmary - last updated 16 May 2017]