Cardiac implants are devices placed inside the body to keep the heart beating steadily or to keep a blood vessel open. The main ones are the pacemaker, the implantable defibrillator, the stent and the artificial heart valve. Cardiac means to do with the heart.
A pacemaker is a battery-powered device about the size of a large coin, placed under the skin below the collarbone. One to three thin wires, called leads, run from it through a vein into the heart. The pacemaker senses every heartbeat through the leads. If the heart beats slower than a minimum rate set by the doctor, the pacemaker sends a tiny electrical pulse that makes the heart beat. An implantable cardioverter-defibrillator (ICD) does the same. It can also give a shock to stop a dangerous fast rhythm. The external version of that shock is explained on the defibrillator page.
A stent is a tiny tube of metal mesh. A cardiologist pushes it into a narrowed artery of the heart on a thin tube, then expands it with a small balloon, so that it holds the artery open. Most stents used today are drug-eluting stents. They slowly release a medicine that stops the artery from narrowing again. In India, the government caps the price of coronary stents.
The decisions inside a pacemaker are made by firmware, the program stored in the device. Take, for example, a retired school headmaster in Thrissur whose pacemaker is set to a minimum of 60 beats a minute. One night, his own heart rate drops to 38. The pacemaker paces his heart at 60 and stores a record of the episode. A small box beside his bed, or an app on his phone, reads the record over a short-range radio link. It sends the record to the clinic's website. The next morning, the cardiologist's team sees an alert and calls him in to check the settings. Sending a device's readings to the doctor from home is a form of remote patient monitoring.
In the clinic, the doctor changes the settings with a programmer: a computer with a wand that is held over the chest. The same link can install new firmware, for example to fix a security weakness. A pacemaker's battery lasts several years. When it runs low, the whole device is replaced in a short operation.
A pacemaker is in class D, the highest risk class, under India's Medical Devices Rules. So each change to its software must be tested and approved before it reaches patients, as software as a medical device explains. The report from each device check also goes into the patient's hospital EHR.