Dr. Shapiro has widespread clinical and research interests in interventional cardiology, and has undertaken a very large number of cardiac procedures in each of these clinical areas whilst at Royal Papworth Hospital in Cambridge.
Before a procedure, a patient is fully informed about their particular procedure in detail by the hospital staff, so that they fully understand what will take place during the procedure itself. A consent form is then signed, which gives the hospital permission to perform the necessary tests and acknowledges that the patient fully understands the risks involved (see below)
The patient is then asked to wear a hospital gown and paper underwear and the nurses then shave a small amount of hair from the groin area so it does not interfere with the equipment. Often the patient will be able to walk to the theatre. These procedures are usually in a modified operating theatre, called a cardiac catheterisation laboratory (common name: Cath Lab). This is a sterile area where the patient lays on an operating table and is draped in sterile green or blue paper sheets, the staff are also clothed in sterile gowns. Interestingly caps and masks are not always worn.
The difference from a normal operating theatre is the presence of a large X-ray machine. This is a very high resolution machine, allowing real time video images of the passage of devices into the circulation and the heart and the taking of detailed images. The images are usually made with an injection down the catheter (a long plastic tube) in order to see the outline of the blood vessels and other heart structures, a contrast medium or dye is used making it easy to see on Xray. The medium or dye occasionally may induce the sensation of a warm flush in the patient or on very rare occasions a slight chest pain. In the past, the dye often made the patient rather sick, and allergic reactions were common, but the newer modern products, of a much higher value and quality are much less troublesome. It is important to note that the dose of radiation is relatively small and poses very little risk to both patient and theatre staff.
Procedures are normally carried out via the femoral vessels (the arteries and veins located in the crease at the top of the leg in the groin area) or the radial artery (located at the wrist). These vessels are entered via a needle puncture after the placement of copious amounts of local anaesthetic. This is usually almost completely painless. The passage of catheters (long specially designed plastic tubes) takes place through the blood vessels themselves. Fortunately, us human beings have no pain sensation inside blood vessels – so other than a curious sensation of pressure, normally nothing is felt.
Many patients feel anxious before and during these procedures, which is not surprising but many are relieved by the absence of pain and reassurance from experienced staff. We give some patients a gentle sedative to calm their fears.
The passage of the catheters, which are specially shaped for this particular purpose , is viewed on the Xray screens and are directed to wherever required both by rotation and forward and backward motions. The movements of the catheters on the Xray screens as well as the images taken can be seen by the patients (although some people prefer not to look!). Many comment how extraordinarily strange it is to see things moving inside you without any sensation of it happening. The tubes placed in the arteries have valves attached to prevent bleeding.
figure coronary angiogram, normal right coronary artery, note the catheter in the artery and the smooth appearance of the vessel.
At the end of the procedures, the tubes need to be removed. As they are placed in blood vessels, there is a risk of bleeding. To prevent this, simple pressure with the fingers may be sufficient – plus there are a number of gadgets to help the process. There are also some clever devices which introduce a plug (of collagen) or a stitch into the artery to seal the hole. Most patients need a few hours of bed rest. For simple or painless procedures such as a coronary angiography, PCI and defect closure, many patients go home on the same day. Although the area in the groin may be a little sore for a few days there should be no other significant pain or discomfort.
For procedures such as a hole in the heart (PFO and ASD) closure (see below for description) an extra form of imaging is used, namely echocardiography. This is done in one of two ways. The first option when using a general anaesthetic involves the use of a TOE probe. This is like an endoscope and is placed in the oesophagus (gullet) , which fortunately lies just behind the heart and produces excellent images particularly of the back portion where the holes in the heart are found. This probe is passed under a general anaesthetic which is used for ASD closure. An alternative ultrasound probe is available which is much smaller and is passed through the veins to the heart (known as intra-cardiac echo or ICE). This can readily be performed under local anaesthetic and is painless.
This is an echo picture taken in the Cath Lab showing a coloured jet passing across a small hole in the heart from the left atrium above to the right atrium below.