A pacemaker (PM) is an electronic device that generates electrical pulses to stimulate the heart muscle so that it contracts. The device is used to treat patients with an excessively slow heartbeat (bradycardia).

Strictly speaking, the heart’s natural pacemakers are the sinus node and, to some extent, the atrioventricular node.

What is a pacemaker and how does it work?

The pacemaker is fitted with 1 or 2 electrodes connected to the atrium and/or the ventricle. These wires constantly monitor the heart’s electrical activity and send data to the computer in the generator. If the heartbeat is irregular or too slow, the pacemaker sends electrical pulses to the heart, causing it to contract. The pacemaker ensures that the heart beats regularly and supplies enough oxygen to the body.

What types of pacemakers are there?

Pacemakers can be divided into single-chamber and dual-chamber systems, depending on the number of electrodes they contain. The terms refer to the pacemaker’s ability to stimulate either one or two heart chambers.

When is a pacemaker used?

The heart requires an electrical pulse to contract or, in other words, to create a heartbeat. Sometimes the heart’s natural conduction system is impaired which means that the heart is no longer strong enough. It either beats too slowly or with too many pauses. Symptoms include fatigue and reduced performance, shortness of breath, dizziness, fainting and unconsciousness. A pacemaker restores a regular heartbeat to the heart.

Common reasons for fitting a pacemaker

• Slow pulse (bradycardia): Bradycardia arrhythmia is a condition where the heart beats too slowly. The brain is no longer supplied with enough oxygen, leading to dizziness, a feeling of weakness and fainting.
• An insufficient rise in the pulse during increased activity (chronotropic incompetence): The pulse displays no abnormalities while resting. However, with increased activity, it fails to quicken in line with demand, limiting performance.
• Heart failure: Sometimes, medication is not enough to treat heart failure (cardiac insufficiency) effectively. A pacemaker can stabilise heart function.
• Bradycardiac atrial fibrillation (bradycardia arrhythmia): Activity in the atrium is impaired so that only a few pulses from the atrium are conducted to the ventricles. The pacemaker regulates activity.
• Carotid sinus syndrome: Part of the carotid artery responds over-sensitively to pressure in the neck or turning of the head, causing a dramatic fall in the heart rate. The pacemaker activates the heart chambers.

How is a pacemaker implanted?

Inserting a pacemaker is considered a routine procedure. Open-heart surgery is not required. The procedure is normally carried out under local anaesthetic. The surgeon makes a small incision (approx. 5cm in length) in the skin just below the collarbone. One or two electrodes are pushed through a vein all the way to the heart. The surgeon connects these electrodes to the pacemaker and programs the device to match the patient’s individual needs. Most patients are discharged from hospital within 24 hours of surgery.

What should people with pacemakers bear in mind in daily life?

Patients with pacemakers can lead normal lives with hardly any restrictions. In fact, an accurately set pacemaker increases quality of life. Patients can pursue many leisure activities without encountering any problems. Even so, it is important to consider several points.

• Sports: As soon as the electrodes are properly embedded, you can continue your sports activities as before. The only exception is diving at depths over 10 metres. This is not allowed as it creates too much pressure. Martial arts and extended arm movements should likewise be avoided.
• Magnetic resonance imaging (MRI): Strong magnetic fields can impair the function of the pacemaker or even damage it. These days, MRI -compatible pacemakers are usually implanted. MRI scans should only be performed where the pacemaker is MRI-compatible. If the pacemaker is not MRI-compatible, a CT scan can be carried out instead.
• Metal detectors: Special metal detectors are used to trace weapons and explosives. Under certain circumstances, they can impair the function of your pacemaker. For this reason, you should show your Pacemaker ID Card when going through airport security. You will then be checked manually and will not be directed through the security gates.
• Mobile phones: The newer pacemakers are hardly affected by mobile phones. Even so, for safety reasons, you should not carry your mobile phone close to your body. You should make all telephone calls holding the phone to the ear farthest away from your pacemaker.
• Some electrical appliances: You should keep the following devices roughly at a half or whole arm’s length: appliances with electrical motors, two-way radios, combustion engines with spark plugs, electrical garden appliances, electric blankets and electrical heating pads, remote controls. You do not have to worry about appliances such as televisions and video recorders, computers, fax machines, washing machines, dishwashers and electric hobs etc.

An implantable cardioverter/defibrillator (ICD) is a miniaturised automatic electrical device that is surgically implanted in patients with a high risk of life-threatening cardiac arrhythmia.

The ICD electrodes are located in the heart chamber and have direct contact with the heart muscle. For patients suffering from ventricular fibrillation, the device automatically triggers an electrical pulse which normalises the activity of the heart muscle and its life-preserving pumping function. The device is fitted in the same way as a pacemaker.

Implanting a defibrillator/cardioverter

The defibrillator, which measures approx. 6cm x 6cm x 1.5cm and weighs around 80g – 120g, is fitted by a heart surgeon or cardiologist. The procedure is carried out under general anaesthetic. The device is usually inserted in the fatty tissue beneath the skin above the left pectoral muscle in the chest (“defibrillator pocket”). In rare cases, the defibrillator is implanted in the abdomen or under the muscle. Using the same incision, the defibrillator’s electrodes – two or three depending on the patient’s condition – are pushed through a vein into the right heart chamber.

If the patient not only suffers from high-risk cardiac arrhythmia but also has an impairment of the heart’s pace-making centres or conduction system, the defibrillator can also function as a “normal” pacemaker.

While the patient is still under general anaesthetic, the device is tested for the first time to check its location and function. A further test is carried out a week later before the patient is discharged. The patient is briefly anaesthetised and the surgeon artificially triggers ventricular fibrillation which is then halted by the device. Before being discharged, patients are given a “Defibrillator ID Card”, which they should always carry with them.

After being discharged, subsequent tests should be carried out every three months to check the status of the device and the programming. If, in the meantime, the patient has experienced cardiac arrhythmia, the relevant data can be retrieved from the defibrillator’s memory. It is also possible to check the device for the delivery of therapy – allowing any necessary changes to be made at this time.

Living with a defibrillator/cardioverter

In daily life, the same restrictions apply as for a pacemaker. However, patients are not allowed to drive for the first six months.

The battery will last for around five years depending on how often the defibrillator is triggered. After that the battery will have to be changed. This involves removing the device from the pocket and connecting a new casing.

Atrial fibrillation is a cardiac arrhythmia, which can be episodic or continuous. The condition causes the heart and the pumping action to fall out of step.

One way of restoring the heart to its normal rhythm (sinus rhythm) is to perform an atrial ablation in a cardiac catheterisation procedure. Generally, this form of treatment is only used when alternative methods of control, such as medication or electrical pulses, have proven unsuccessful.

What is catheter ablation?

A special catheter is used to perform an electro-physiology (EP) study to trace the places inside the heart that are causing cardiac arrhythmia. A variety of different ablation methods are available. For example, an electrode, measuring no more than a few millimetres, is located in the catheter and is heated using radiofrequency current. The areas of heart tissue touched by the electrode are ablated or destroyed point by point. The succession of many ablation points creates linear lesions which limits the spread of the electrical pulses. Another possible method involves the use of balloon catheters which ablate the tissue using extreme cold (cryoablation) with similar levels of success. Other possibilities include balloon catheters that use radiofrequency current or lasers, as well as helical ablation catheters. The objective of all these treatments is to prevent atrial fibrillation, without the need for medication.

ExtraCorporeal Membrane Oxygenation (ECMO) is a life-support machine used to treat patients with impaired heart and lung function for a certain period of time (generally 1-3 weeks).

Who receives ECMO treatment?

As a rule, ECMO is given to patients with profound heart and lung failure (cardio-pulmonary failure) who cannot be treated effectively with medication and conventional ventilation.

Heart children, whose cardiac output is still weak after an operation, are sometimes placed on ECMO for several days (vein to artery). This gives their heart extra time to recover. It also gives the specialists more time to plan their next steps.

ECMO can also replace just the lung function (oxygen enrichment and CO2 removal) in patients presenting with lung problems (e.g. pneumonia or serious infections) but whose heart function is only slightly impaired. In this instance, a veno-venous (vein to vein) cannulisation is the preferred option. The lungs are “immobilised” and the ventilation gives them time to recover without sustaining any further damage, until they can function properly again.

How does ECMO work?

A cannula is placed in a large vein, channelling blood from the body into a pump and oxygenator where it is enriched with oxygen and returned to the body through a second cannula. The second cannula is located either in a major vein (vein to vein) or in a major artery (vein to artery).

There are two access routes for cannulisation: either “peripherally” via the carotid arteries or “centrally” after opening the ribcage (this option is generally only used on patients who have undergone heart surgery).

Children receiving ECMO treatment are looked after in a single room in our intensive care unit (ICU). They are given medication to make them sleep and to relieve any pain. Older children can be in a waking state but need to keep still to ensure that the cannulas do not move.

An artificial heart is a system that usually supports the function of just one of the two heart chambers, although in extreme cases, it can also support both.

In the case of a weak heart muscle (myocardial insufficiency), it serves as an additional pump to support the seriously diseased heart and to maintain circulation.

When is an artificial heart used?

For patients with myocardial insufficiency that is so advanced that medication is no longer effective, a heart transplant becomes the method of choice. Several tests and examinations must be carried out before the patient can be added to the transplant waiting list. Patients usually have to wait a long time for a transplant. Often, their heart function continues to deteriorate during this period and there is a risk that they will die before a suitable organ becomes available.

In such instances, it may become necessary to bridge the time gap to transplantation. An “artificial heart” is one way of doing this.

How does an artificial heart work?

The blood is channelled over the apex of the heart muscle through an elastic plastic tube into the pumping chamber of the support system. This pumping chamber is inserted between the muscles in the abdominal wall beneath the diaphragm. The flow and return of blood to and from the pumping chamber is monitored electronically.

A control cable is connected to a central control unit and runs through the fatty tissue beneath the skin. The blood is pumped into the aorta through a second plastic tube. The heart and pump work in parallel and independently of one another.

Given that the heart only has to pump a small amount of blood into the body, it is put under less strain. At the same time, the remaining organs benefit from improved blood flow provided by the additional pump.

From a surgical point of view, the technical aspects of a heart transplant are not particularly challenging – even where a heart has already undergone surgery in the past. The diseased heart is separated from the major blood vessels and the healthy donated heart is reconnected to the corresponding blood vessels. It is the pre-operative assessment and post-operative care that are crucial.

The post-operative care following a heart transplant is of critical importance. It encompasses not only medication but also psychological support which starts while the patient is still on the transplant waiting list.

Pre-operative assessments

Before a decision is made to opt for a heart transplant, extensive tests and examinations are required. Usually, a clinic that has been treating a heart patient will contact a specialist heart centre and the patient is invited for an introductory meeting.

The first main objective is to determine the extent of heart failure, to establish the patient’s attitude to having a transplant and to identify any other conditions that may rule out a heart transplant. In most cases, one meeting is not enough. In fact, the patient will either spend several days on a ward or will have to make repeated visits as an outpatient. This is a good opportunity for the patient to get to know the clinic and the staff.

Registering for a heart transplant

Once a decision has been made to perform a heart transplant, the patient is added to the Eurotransplant registry in Leyden and is placed on the waiting list.

Waiting for a heart transplant

Waiting times can vary from several weeks to many months so it is important to be able to bridge this time gap. As the heart failure advances, the patient will probably be admitted to the local hospital more frequently. Close cooperation between the transplant centre and the local hospital is of huge importance. In many cases, it will be necessary to admit the patient to the transplant centre, and to check whether additional support is needed to bridge the time gap.

While on the waiting list, it is essential that the patient can be reached at all times.

Performing a heart transplant

The actual transplant itself is the shortest part of the treatment plan. When the transplant centre receives an organ, the patient is called and asked to come to the centre immediately. This can cause the patient to feel anxious:

"Oh my goodness, it’s finally happening!"

Not only the patient but also members of the family may suddenly feel stressed and anxious:

"What’s the quickest and safest way to get to the transplant centre?"

The best way is by ambulance. The drivers are used to this kind of situation and, because they are not directly involved, they tend to be a lot calmer. If they are stuck in traffic or if there are other road-related problems, they can reduce the time to hospital by switching on their blue lights. When you get to the centre, you will be issued with a transportation certificate for your health insurance. On arrival at the clinic, the first half-hour tends to be very busy. While the necessary paperwork is being completed as efficiently as possible, the preparations for theatre get under way. Usually, the patient already knows the nursing staff and clinicians from the pre-op assessments.

It is essential that the patient arrives at the centre without delay and that this preparatory phase is completed.

This is usually followed by a period of inactivity as the patient and family members wait for the next phase to begin. This may take several hours and largely depends upon the organisation of organ removal.

The patient is taken into theatre where all the necessary monitoring steps are put in place. Depending on the time plan, and after consulting with the organ removal team, the patient is then put under general anaesthetic.

The organ removal team may abort the transplant at any time as they may find that, contrary to expectations, the donor heart is not suitable after all. This can happen even after the patient has been anaesthetised.

If everything goes to plan, the transplant is carried out. There is nothing more for the family members or patient to do. The operating time varies and will depend on how well the donor heart has coped in the time from removal and transplantation to the restoration of blood flow (reperfusion).

Post-operative stay in hospital

After surgery, the patient is taken to the intensive care unit (ICU). The next phase is all about controlling the circulation, transplant rejection and infections. During this phase, continuous monitoring is essential.

The patient’s circulation system is supported with medication.

Follow-up checks

Heart muscle biopsies are performed on a regular basis to monitor transplant rejection. In the first few weeks after surgery, a biopsy is carried out every week. Depending on the patient’s progress, the intervals between biopsies become longer in the months that follow.

A cardiac catheterisation procedure is carried out once a year to identify any signs of chronic transplant rejection. The patient’s immune and infection status is monitored on a regular basis.

Even if the patient feels well, these measures continue over the years. Occasionally, the test results require immediate attention and hospitalisation, even though the patient has no complaints and the treatment may not at first seem necessary.

In the years following a transplant, the patient will be required to return to the centre for these tests roughly four times per year. If the patient experiences any complaints, they should, of course, go to the centre without delay.

Life after a heart transplant

The aim of a heart transplant is for patients to return to their social surroundings so that they can participate fully in society. After such a long illness, this will not happen overnight, but over a period of many months.

One of the first positive experiences will probably be climbing the stairs without having to stop for breath. Holidays to far-flung destinations are also possible although the country’s hygiene standards and medical care should always be considered before booking.

The regular testing described above means that patients will always remain in contact with their transplant centre.

The heart is composed of two atriums and two ventricles. The valves between the atriums and the ventricles (atrioventricular valves) as well as between the ventricles and the arteries (aortic and pulmonary valves) determine the direction of blood flow.

For the heart to function normally, it is essential that these valves are working properly. Cardiac valve defects can either be congenital or acquired. An acquired cardiac valve defect can be triggered, for example, by rheumatic fever, a bacterial infection or following a heart attack.

We distinguish between a

narrowing of the valve (stenosis) – the blood accumulates in front of the valve

and a

valve that does not close properly (insufficiency) – the blood flows back again after the valve has closed (regurgitation).

In some cases, one or several cardiac valves may display both anomalies at the same time.

If the valve is significantly impaired, the heart function will be limited, causing the patient to experience shortness of breath during exertion. Depending on the severity of the defect, the patient may display other symptoms as well, e.g. swollen legs, an irregular heart rhythm (allodromy) or a racing heartbeat (tachycardia).

In cases of suspected valve impairment, an echocardiography is carried out which can often result in a reliable diagnosis. Generally, cardiac catheterisation is performed as well.

The two most commonly affected cardiac valves are the aortic valve (between the left ventricle and the aorta) and the mitral valve (between the left atrium and the left ventricle).

The mitral valve can usually be surgically reconstructed with the body’s own valve tissue. However, the success of this procedure on the aortic valve is usually short-lived. As a result, it is almost always necessary to replace the valve with a cardiac valve prosthesis.

The paediatric surgeon will correct the heart valve defect where necessary.

The procedure is carried out under general anaesthetic and with the help of a heart-lung machine. In the operating theatre, the patient is placed on their back (supine) and covered with surgical drapes under sterile conditions.

The ribcage is then opened, the heart-lung machine is connected and the heart is stopped (arrested).

The cardiac valve is examined closely to establish whether it can be repaired or whether the defect is so far advanced that a prosthetic valve is needed.

Artificial and biological valves

There are two main types of prosthetic heart valves: artificial heart valves und bioprosthetic heart valves.
The surgeon and patient discuss which of the two options is most suitable. The choice is largely dependent on the patient’s age, any other conditions the patient may have and the type of heart valve defect in question.

Patients with an artificial prosthesis will have to take blood-thinning medication for the rest of their lives. The advantage of an artificial heart valve is that it lasts for a long time.

Patients fitted with a bioprosthetic heart valve do not have to take blood-thinning medication in the long term. This valve type may degrade after 10-15 years, possibly requiring further valve replacement surgery.

This is where the aortic valve is replaced on a beating heart.
Cardiac catheterisation is used to implant an artificial heart valve (heart valve stent) in the dysfunctional aortic valve. In the past, an aortic valve replacement would always involve open-heart surgery and a heart-lung machine. The new method has been used successfully on hundreds of patients at the university cardiac centre.

During this procedure, the aortic valve can be accessed in two ways:
Either through the femoral artery (transfemoral access) or through the apex of the heart by making an incision between the fourth and fifth ribs (trans-apical access). Both methods involve pushing a catheter through to the aortic valve.

The dysfunctional heart valve is stretched open with a small balloon at the tip of the catheter (balloon dilation) and a vascular prosthesis with a heart valve (heart valve stent) is carefully positioned with the help of echo- and angiographic monitoring. Finally, the prosthesis is stretched open, replacing the old valve. The procedure is carried out under surgical conditions at a certified cardiac catheterisation lab.

This procedure provides new opportunities for patients unable to have surgery either due to their advanced age or because they have other serious conditions.

A bypass operation involves diverting the flow of blood around obstructed blood vessels. Bypasses are laid mostly to the heart but also to other blood vessels when the dysfunctional vessels are too diseased to secure the blood supply.

This procedure is used to treat coronary heart disease (CHD).

When is a bypass operation carried out?

A bypass operation may become necessary for a variety of reasons. It is often required on the heart when

• cardiac catheterisation to widen or re-open a coronary artery has proven unsuccessful
• one or two coronary arteries are affected and the left coronary artery (LCA) is either constricted at its base or is completely closed (occlusion) – otherwise known as left main coronary artery stenosis.
• all three main branches of the coronary arteries are affected at the same time ("three-vessel disease")
• there is repeated narrowing along extended sections of the arteries and the patient is diabetic
• several coronary arteries are affected, and the reduced supply of oxygen and nutrients is restricting the pumping action of the left ventricle
• when the left anterior descending artery between both heart chambers (RIVA, originates from the left coronary artery) is extremely narrow at its origin