A GP quizzes an expert to take a medical issue beyond the textbook
GP Dr John Couch interviews
Dr David Fluck
thinking in intervention cardiology
Practical points · Catheterisation can give detailed anatomy · Emergency angioplasty certain to be used more in UK · More and more patients fitted with implantable defibrillators · Use of drug-eluting stents in angioplasty is major step forward
· Catheterisation can give detailed anatomy
· Emergency angioplasty certain to be used more in UK
· More and more patients fitted with implantable defibrillators
· Use of drug-eluting stents in angioplasty is major step forward
What cardiac catheterisation can tell us
can tell us
What are the current indications for adult cardiac catheterisation?
The commonest indication for adult cardiac catheterisation is the investigation of ischaemic heart disease, to establish whether coronary artery disease exists.
If disease does exist, cardiac catheterisation will establish the severity and prognosis of the condition and whether revascularisation or additional medical therapy is appropriate.
The other indication is the investigation of valvular heart disease, but this has become less common as non-invasive testing continues to develop. Echocardiography, for instance, gives us very clear information in terms of the severity of and mechanism for valvular dysfunction. On the other hand, we still need catheterisation to clarify the coronary artery anatomy in patients for whom we are proposing valve surgery.
Generally the risks of catheterisation are very low. Risks include local complications related to the access site such as haematoma and infection. About one in 1,000 patients experience a major adverse cardiac event (MACE) such as death or stroke.
What information can cardiac catheterisation provide?
Catheterisation generally provides detailed anatomy of the coronary circulation and will show the presence, severity and site of coronary narrowings. It can also give us an idea of left ventricular (LV) performance. On this basis we can then assess both the prognosis of the patient and whether revascularisation is required.
To assess LV function a catheter is passed across the aortic valve into the
LV cavity. X-ray contrast medium is injected which we can then monitor.
Indications for angioplasty
How would you define the difference between intervention cardiology and cardiac surgery?
Angioplasty versus coronary artery bypass graft treatment of ischaemic heart disease provides a good example of the difference between intervention cardiology and cardiac surgery. Both are therapeutic procedures aimed at improving blood supply to the heart. But cardiac surgery is a major operation that often involves a thoracotomy with substantial time in hospital and convalescence. Angioplasty is a much less invasive procedure with often only a day in hospital and a very quick recovery time.
What factors decide whether to attempt coronary angioplasty and when would a stent also be used?
There are two reasons for considering surgical or percutaneous revascularisation: to reduce symptoms from ischaemic heart disease and/or to improve prognosis. Patients must fall into at least one of these categories.
Coronary anatomy often dictates which method is more appropriate, with surgery a better option for more diffuse and widespread disease. Sometimes both procedures are just as applicable and other factors such as co-morbid conditions and patient preference must be considered.
There is about a 10 per cent risk of early restenosis with angioplasty using bare metal stents whereas with bypass surgery, after the initial risks of the operation, it is unlikely
you would have any problems before
about 10 years.
We now deploy a stent during angioplasty in 90-95 per cent of cases. Stents offer
benefits over angioplasty alone in terms of fewer short-term complications and a reduced risk of restenosis.
When is an emergency angioplasty indicated?
There are two indications for emergency angioplasty. The first is in patients presenting with acute coronary syndrome (unstable angina) who have not settled with medical therapy and are at high risk of having an MI with more myocardial damage.
The other indication is acute MI. There is much evidence to suggest an angioplasty is actually more beneficial to a patient presenting with an MI than simple thrombolytic treatment. Mortality can be halved to around 3.5 per cent.
Emergency angioplasty is routinely used in countries like the US, France and Germany. It is currently used to a lesser extent in the UK partly due to lack of infrastructure but will almost certainly be used more in the future.
What is the rationale for antiplatelet treatment
Antiplatelet therapy is very important after angioplasty with or without a stent. This is because angioplasty causes plaque rupture which activates platelets.
Evidence has shown that using aspirin together with another antiplatelet agent clopidogrel reduces the risk of acute thrombosis. The duration of clopidogrel treatment is hotly debated but we currently recommend four to six weeks following a routine stent, about six months with the newer drug-eluting stents and about 12 months in patients following acute coronary syndrome.
Changes in the use of pacemakers
Which arrhythmias can be treated by use of a pacemaker and how would you decide when
one is indicated?
The vast majority of pacemakers are implanted for symptomatic bradycardia caused, for instance, by sinus node disease, second-degree atrio-ventricular block or complete heart block.
Other conditions such as vasovagal syncope may occasionally benefit from pacing.
Fewer pacemakers are now fitted for tachyarrhythmias for which radiofrequency ablation is more commonly used.
There are patients with sinus node disease who have paroxysms of atrial fibrillation and periods of sinus arrest for whom pacing is very successful.
Modern pacemakers are very sophisticated and able to adapt to changes in patients' arrhythmias.
Which other conditions can be treated by pacing?
Implantable defibrillators can be used in patients who have either survived a cardiac arrest or are at high risk of developing one. Evidence shows the use of an implantable defibrillator gives a better result than the use of antiarrhythmic drugs alone. Numbers of patients with implantable defibrillators in the UK are small but growing.
Patients with refractory heart failure can have dysynchrony of left ventricular contraction and a biventricular pacemaker can resynchronise the left ventricle and improve performance. These pacemakers have been shown to be of great benefit to patients, improving symptoms and reducing hospitalisation by up to 80 per cent and mortality by around 20 per cent
significant improvements for this very high risk group of patients.
Do all patients with a pacemaker require anticoagulation or an antiplatelet agent?
No, it is not the existence of the pacemaker itself that means such agents are needed but the underlying cardiac status such as atrial fibrillation, impaired left ventricular function or ischaemic heart disease.
What is the cost of an average pacemaker?
Costs are extremely variable across the country. Conventional pacing costs £1,500-£3,000, biventricular pacing £3,500-£8,000 and implantable defibrillators £16,000-£25,000.
Although implantable defibrillators seem expensive, economics make them an effective treatment as the cardiac event rate is so high in this group of patients.
Batteries tend to last seven to 10 years depending on levels of use.
The future in intervention cardiology
What is the role of electrophysiological studies?
Cardiac electrophysiology is predominantly used to evaluate the mechanisms of cardiac arrhythmias and identify the strategies to
treat them. Treatment can be conservative, medical, radiofrequency ablation and, in a few cases, pacing.
What are the indications for radiofrequency
ablation, and how is it performed?
Radiofrequency ablation of an accessory pathway or ectopic focus may be used for more problematical and symptomatic arrhythmias. The classic condition for radiofrequency ablation is in a patient who is troubled with paroxysms of a narrow complex re-entry tachycardia, such as that seen in patients with Wolff-Parkinson.
Access is usually gained via the femoral vein and occasionally via the femoral artery. Electrode catheters are directed into the
heart under X-ray guidance. The electrode catheter is then used to map the conducting system of the heart, looking for accessory pathways or ectopic foci which, once found, can be destroyed with localised electrical energy via the catheter. The procedure does take longer than an ordinary cardiac catheterisation typically one hour to 90 minutes.
The risks of radiofrequency ablation are low. However, in high-risk situations when the accessory pathway is close to the atrioventricular node, there is a less than 1 per cent risk of inducing complete heart block, which would require pacing.
What treatments are on the horizon?
The next major step forward will be the widespread use of drug-eluting stents in angioplasty. These are stents coated with chemicals that reduce the restenosis rate,
the major Achille's heel of angioplasty. It is likely they will be recommended in the next NICE guidelines.
In electrophysiology, major advances are occurring in the treatment of atrial fibrillation, particularly in its early stages.
We are likely to see many more atrial fibrillation patients treated by radiofrequency ablation in the future.
John Couch is a GP in Ashford, Middlesex David Fluck is a consultant cardiologist at St George's Hospital, London, and Ashford and St Peter's Trust, Chertsey, Surrey
David Fluck is a consultant cardiologist at
St George's Hospital, London, and Ashford
and St Peter's Trust, Chertsey, Surrey