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Pacemaker implant surgery
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Some hearts beat regularly while some don’t. The normal, healthy heart has its own pacemaker called the sinus node that regulates the rate at which the heart beats. It produces impulses that travel through electrical pathways in the heart and cause the heart muscle to contract and pump blood as it’s needed by the body. Sometimes, this natural mechanism becomes diseased so that impulses are irregular – too slow, too weak – or its impulses may be blocked by other disorders. Bradycardia is the name for a group of diseases in which the heart beats too slowly to support the circulatory needs of the body.
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| Dr Ketan Mehta |
If this happens, the person may feel dizzy, weak, or just very tired. An artificial pacemaker may then be used to restore a consistent flow of proper electrical impulses, thus improving blood circulation and restoring a general feeling of well being to the patient. When people refer to a pacemaker, they are actually discussing a pacing system, which includes the pacemaker and leads. A pacemaker is a small device that is implanted under the skin, typically just below the collarbone. The device delivers therapies to treat irregular, interrupted, or slow heartbeats. Leads are thin, soft, insulated wires about the size of a spaghetti noodle. The leads carry the electrical impulse from the pacemaker to the heart and relay information about the heart’s natural activity back to your pacemaker. It is prescribed for people whose hearts are beating too slowly or irregularly. A pacemaker may also be used to treat fainting spells (syncope), congestive heart failure, and hypertrophic cardiomyopathy.
So, how does a pacemaker work?
A pacemaker is designed to mimic the heart’s natural pacemaker, the sinus node. The pacemaker has two main purposes – pacing and sensing.
- Pacing: A pacemaker will send an electrical impulse to the heart through a pacing lead when the heart’s own rhythm is too slow or interrupted. This electrical impulse starts a heartbeat.
- Sensing: A pacemaker will also “sense” (monitor) the heart’s natural electrical activity. When the pacemaker senses a natural heartbeat, it will not deliver a pacing pulse.
General steps for implanting a pacemaker include:
- A small incision, approximately two to four inches long, will be made in the upper chest area, just below the collarbone
- One or two leads will be guided through a vein into the heart, and the leads will be connected to the pacemaker
- Pacemaker settings will be programmed, and the device will be tested to ensure that it is working properly to meet the patient’s medical needs
- The pacemaker will be inserted beneath the skin, and the incision in the chest will be closed.
Living with a heart device
Living with a heart device usually requires some adjustments, such as restricting your arm movements for the first few weeks and visiting your doctor for regular check-ups. But, pacemakers help millions of people live more full and active lives.
A patient’s medical condition determines the type of pacemaker one may receive. Pacing therapy is diverse because the underlying heart conduction disorders that result in rhythm disturbances are different. If your medical condition or pacing requirements change, your doctor may prescribe adjustments in certain functions of your pacemaker.
Pacemakers have improved in size, better life and functionality since the early days. This, in turn, has led to better patient outcomes, lesser side effects and hospitalisations and improved longevity including quality of life. The technology has also helped in lowering cost of managing the disease.
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Interesting facts
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MRI compatible pacemaker – the ‘smart’ choice
For millions of patients with cardiac devices, MRI scans are unsafe and contraindicated. While a traditional pacemaker helps to treat a form of cardiac arrhythmias known as bradycardia (slow heart beats) and normalise the heart rhythm, it may pose challenges for cardiac patients with other health complications who need to be exposed to an MRI scan. These include high-risk elderly patients, with diseases of the brain, spinal cord, or joints.
Furthermore, it may also include individuals over the age of 65 who are twice as likely to undergo a scan for the liver, gall bladder, pancreas and kidney. This turned out to be true in the case of a 76-year old woman from Mumbai. She had been suffering from diabetes from the past 20 years, hypertension for 15 years and Ischemic Heart Disease (IHD) for 12 years. She was implanted with a dual chamber pacemaker due to complete heart block (CHB). A dual-chamber pacemaker typically use two pacing leads, one placed in the right atrium and the second placed in the right ventricle; the electrical pulses delivered to the heart are timed so that the atria and ventricles are beating “in sync” with each other, however such a pacemaker is not MRI compatible.
Over two years back, she went through a contrast CT scan of the abdomen which was performed for suspected acute pancreatitis. However she got an anaphylactic reaction which is very dangerous for the patient. She has been getting repeated episodes of transient giddiness and ataxia requiring frequent hospitalisation since the last six months on which she was advised to go for MRI or CT scan by the neurologist. Unfortunately, she could not be subjected to a CT scan due to allergic reaction and could neither go for MRI due to non-MRI compatible pacemaker. Due to these complications the patient was unable to go for the right investigation tests, and hence she has been treated symptomatically. If this patient were with an MRI compatible pacemaker the right diagnosis could have been made and subsequently her trauma and suffering could have been reduced to a great extent.
Currently, most pacemakers are not considered safe in an MRI environment because the MRI could change the settings, temporarily affect the normal operation of, or potentially damage the pacemaker. As an MRI machine uses a strong magnetic field, it exposes the patient to the risk due to heating up at tip of the metal wires of these pacemakers that is in contact with the heart and thus damaging cardiac tissues resulting in loss of stimulation of the heart to beat. Also the strong magnetic field could reset the device or affect its pacing function giving rise to abnormal heart beats.
Research has shown that even if the device is turned off or set at a constant rhythm during the scan there are slight changes in electrical parameters required for stimulating the heart to beat after the MRI scan compared to pre-scan. This also raises several concerns for the practitioners who are carrying out the scan. The magnetic field will not only reset the pacemaker but may permanently damage it. Switching off the device is not possible in many patients as it could prove fatal even if it is for a few minutes.
Medical and surgical specialists rely on MRI for diagnosis. In fact, MRI is the gold standard diagnostic tool for soft tissue imaging for neurologists, oncologists, and orthopaedic surgeons. MRI is extremely necessary for diagnosis of internal soft tissue injury and diseases. This stresses on the need for pacemakers suitable for allowing MRI scan. Generally, bradycardia (slow heart beats) can be diagnosed with symptoms like dizziness, fatigue, fainting and other non-invasive tests. The only reliable treatment is pacemaker implantation.
Medtronic has a pacemaker system which is FDA approved for use in the MRI environment. This pacemaker system has a unique design, developed so that under specific conditions, patients may safely undergo MRI scans. With regular pacemakers, patients would be barred from undergoing any MRI scanning as exposure to magnetic radiation could lead to several complications. But MRI conditional pacemaker has no such adverse effects and has truly emerged as a technological boon for patients who suffer from bradycardia (slow heart beats) who may require an MRI scan in future. However, patients implanted with an MRI conditional pacemaker should consult their cardiologist before undergoing the scan.
Conclusion
MRI compatible pacemakers have maintained a positive track record and gained acceptance from cardiologists both in the national and international heart centres. It is important that we are aware of these technological advancements and utilise them to counter unforeseen health issues if it ever strikes someone around us.
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