228th Meeting – Tuesday, October 8th  2002

'Intervention Radiology as a Substitute for Surgery'

A talk and presentation by Steven C.H. van de Ven, MSc.

Present: Leo Alting Von Geusau, Hans Bänziger, Hans Ulrich Gerber, Yves Goudineau, Reinhard Hohler, Ken Kampe, Peter Kunstadter, Sally Kunstadter, Frank Mohlmann, Oliver Puginier, Horst Schmadi, David Steane. An audience of 12.

The speaker: Steven van de Ven, a retired Dutch physicist, worked at Philips Research Laboratories from 1958 to 1966. During this period he completed studies at the Technical University of Eindhoven with a Master’s degree in physics. From 1966 to 1969 he was Group Leader for product development Imaging Systems. From 1969 until his retirement in 1991, Steven was with Philips Medical Systems where he specialised in work on Cardio-, Neuro-, General vascular diseases. After retirement at 60 he was requested by the CEO to continue for another 4 years as a consultant to set up a regional Philips Medical Systems activity in Asia. During his career he has spent 20 years involved with the development and clinical application of C/V systems in leading hospitals.

The text of the talk:

What is Intervention Radiology? - Intervention Radiology is a medical procedure performed by a trained physician who approaches a problem in the body with an instrument and repairs what is wrong without surgery. In most cases it refers to removing obstructions in arterial blood vessels (arteries) and is called ANGIOPLASTY. The wording “Radiology” refers to the fact that the procedures are done under live X-ray imaging.

Blood: Composition and Function. - Blood flows in our body through a network of vessels and provides oxygen, nourishment and hormones to all organs and tissues. Blood carries away waste materials, besides having other functions. Adults have 5-6 litres of blood, which is about 7-8% of the body weight.

In a reducing sequence of quantity, blood consists of: Plasma, Erythrocytes, Leukocytes and Thrombocytes.

Plasma consists mainly of water and salts. The salt concentration and Ph (plasma acidity) level are controlled by the kidneys. Plasma brings vitamins, nutrients, and minerals to the cells and takes waste products away. Plasma carries components which regulate the water content of tissue and blood, as well as antibodies, which help fight infectious organisms, and clotting factors, which help stop minor bleedings.

(Serum - plasma with its clotting factors removed - has an important medical use).

Erythrocytes - Red blood cells: Mainly composed of hemoglobin, a protein and iron compound. Their main function is to take up oxygen in the lungs and deliver it to all body cells.

Blood is marked of type “A”, “B”, “AB”, or “O”. This indicates the presence or absence of certain antibodies on the red blood cells. A further mark is the Rhesus factor. Rh+ is present and Rh- is not present. Blood types need to match for successful blood transfusion.

Leukocytes - White Blood Cells: They contribute a very small part to the total volume of blood, but are extremely important for our immune system. They are the core factor in fighting invading bacteria, parasites and viruses.

Thrombocytes - Platelets. The only purpose of the platelets is to start the process of blood clotting; the coagulation process that occurs when a blood vessel is damaged. They work together with the plasma based clotting factors to form a clot, which stops the bleeding.

BLOOD IS THE LIQUID OF OUR LIFE. Obstructions inside arteries limit normal blood flow to organs and tissue. The result is malfunctioning.

Obstructions are due to:

Atherosclerosis  à blood clotting à obstruction

Embolus à foreign body swims in the blood flow until it gets stuck somewhere à obstruction.

Plaque à fatty substance à obstruction

History of Angioplasty

In 1964, Dr. Charles Dotter pioneered a procedure in which he introduced a catheter into the body, usually into the femoral artery, moved it to the obstruction and tried to pass it. This was repeated, every time using a thicker catheter, until the obstruction was sufficiently removed and blood flow restored. The procedure was named to him and called “DOTTER”

Development: The Balloon Catheter. The balloon catheter has 2 concentric lumens; the inner is open ended and the outer ends in an oblong balloon. The balloon is placed in position within the obstruction and then inflated, thus compressing the obstruction against the wall of the artery and restoring blood flow.

We will discuss the function of the catheter’s inner lumen under “How it is done”.

Success rates of the procedure initiated the development of balloon catheters of different size for different applications. The procedure is known as ANGIOPLASTY or in short PTA (Percutaneous Transluminal Angioplasty)

Does it replace surgery? Is it safe?

One of the first steps – when obstructions in blood flow are suspected – is ANGIOGRAPHY.  This will show the location and severity of the obstruction. Some obstructions are best treated with vascular surgery and others with angioplasty. This decision depends on the location and the severity of the obstruction (severe atherosclerosis).

In many cases PTA can successfully restore normal blood flow and the procedure is safe.

Done under local anesthesia, administered at the location on the body where the catheter is introduced, patients are conscious and recover much, much faster than after surgery.

Modern X-ray equipment, used during Angioplasty, is designed for this procedure and the received X-ray dose is well below permitted limits.

Important: If the patient is a diabetic and takes insulin, or if other medicine is taken, or the patient is allergic to X-ray dye, the doctor will take special precautions during the procedure.

Where in the human body? The aorta is the main and biggest artery. It departs from the heart, makes an arch and runs down the body. From the aorta depart many arteries, going to the neck and head, the arms, organs - including the liver, kidneys, intestine, and sex organs and the legs.

Most obstructions occur in arteries feeding the kidneys, intestine, liver, heart and the legs.

Fewer occur in neck arteries and arteries feeding the arms.

Coronary arteries, which feed the heart, are discussed under Special Procedures.

Arteries inside the skull and feeding the brain are not suitable for angioplasty. Obstructions there may cause STROKE and are treated with other procedures. We will discuss some cerebrovascular diseases under “Special procedures”.

In general angioplasty is a safe and successful procedure to restore normal blood flow. It can be applied anywhere in the body as long as the obstructed artery is accessible with a catheter and has sufficient lumen.

How is it done? The patient is taken to the X-ray Dept. to a room equipped for angiographic examinations. Laid down (face upwards), usually the right groin area is prepared for catheter insertion, where first a local anesthetic is injected. A short tube (introducer sheath) is inserted into the femoral artery. A guiding catheter is then inserted through the sheath and moved into or close to the obstructed artery. Then a guide wire is inserted, the end of which is positioned past the obstruction. Next the balloon catheter, with its open ended lumen, is moved over the guide wire and the balloon placed in position within the obstructed area.

The balloon is inflated (several times if necessary), which splits and reshapes the obstruction and stretches the artery wall. X-ray contrast (dye) is then injected into the obstruction area and a few X-ray exposures are made to confirm blood flow is restored. The catheters are then removed. When the sheath is finally removed (sometimes it is left in place for an hour or so), a nurse will compress the location of catheter insertion for 20 min., after which a compression dressing is applied. The patient returns to the ward and can usually go home the next day.

It will be clear that the doctor needs to see where he is going with the catheters. This is done under live X-ray imaging (fluoroscopy). Many imaging techniques, including computer assisted image processing, have been developed to support angioplasty procedures. This, together with increased medical skills and experience, has resulted in very high procedure safety, shorter procedure times (average 1-2 hrs) and the treatment of increasingly more complicated cases.

Does the patient feel pain? – NO. Injection of dye (X-ray contrast, which contains iodine) may produce a brief sensation of warmth, which is harmless.

What causes obstructions in arteries? - Diet, life style, heavy smoking (lung inhalation), family history, and age. However, even though most patients are over 55 it does not mean that one cannot get the illness at younger age.

Special Procedures

Angioplasty of the coronary arteries. (PTCA - Percutaneous Transluminal Coronary Angioplasty)

The heart, about the size of our fist, is made of muscular tissue and is the blood pump of our body. It has its own blood supply via the RIGHT and the LEFT coronary arteries, which depart immediately above the AORTIC VALVE.

The pumping activity is regulated by electric pulses which activate the muscle cells, resulting in a heart compression, called “systole” (pushing out the blood) and a relaxation, called “diastole” (filling with blood). The heart muscle needs plenty of blood for its hard work and the coronary arteries split soon after their departure into many branches to provide blood to every part of the heart. Obstructions in these branches cause decay of muscle tissue, resulting in an INFARCTION if not treated in time.

In 1977, Dr. Andreas Gruentzig was the first cardiologist who used a balloon catheter to restore blood flow in a coronary artery. Until then it was the exclusive work of the heart surgeon (coronary bypass or graft surgery). Very soon many top cardiologists joined Gruentzig’s research work. Purpose designed balloon catheters, increased medical skills and experience, and ongoing research to further perfect imaging techniques made PTCA a successful and safe procedure, certainly when typical symptoms of coronary obstructions are early detected.

Although really complicated cases can today be treated with PTCA, it does not completely replace coronary surgery. The choice, whether to go for PTCA or for surgery, is carefully made based upon the patient’s condition and the results from several tests, including a heart catheterization (angiogram of the heart and coronary arteries). PTCA is, for patient safety reasons, only done in hospitals where heart surgery is on stand by. Done in a dedicated heart catheterization room, the procedure is much similar to the before described angioplasty, as well is the patient’s recovery time.

Laser Angioplasty.  Laser (Light Amplification by Stimulated Emission of Radiation) is the acronym used for the coherent light which originates from a single source and carries energy in the form of photons (energy packages). Laser light was discovered during the late fifties and soon became a very important technology with industrial as well as medical applications.

Laser angioplasty uses a unit where the laser beam is produced. To this unit a laser catheter is connected which is advanced through the blood vessels to the blocked artery. The laser catheter emits at its tip, pulsating beams of light (energy) that vaporize the plaque and thereby improve the blood flow. Laser angioplasty can be a procedure on its own, but it is mostly used in combination with balloon angioplasty. In those cases, the laser procedure will be followed by balloon angioplasty.

Rotablator: Coronary atherectomy. A later development (early nineties) to restore blood flow in blocked arteries makes use of the Rotablator catheter. Located at the end of this slender catheter is a small burr coated with diamond crystals. The catheter is inserted into the artery and advanced to the blocked area. Then the burr is rotated at up to 200,000 RPM. As the diamond crystals cut into the blockage, the catheter is further advanced until it has “drilled” itself completely through the obstruction. The removed plaque particles are so small that they cannot cause another obstruction. They are removed with the blood stream, filtered out by the kidneys and disposed with urine.

Whether balloon angioplasty, laser, rotablator or a combination of techniques is used to restore blood flow depends upon two main factors:

Where is the blockage?

How severe is it? - A nearly or total blockage is unsuitable for balloon angioplasty only.

Stenting - A stent is a small tube made of surgical steel wire mesh. It is used to keep an artery open after angioplasty, when the doctor fears a re-closure (restenosis) may occur. The stent is placed over the balloon of an angioplasty catheter and put to its smallest diameter. The catheter is then introduced with the stent into the area of the previous blockage. The balloon is then inflated, which expands the stent and locks it in place against the artery wall. After the balloon is deflated, the balloon catheter is removed and the stent remains in place.

Video of PTAC procedure.

Cerebrovascular Diseases

Our brain controls many of the body’s functions. When brain cells are deprived of proper blood flow (oxygen and nutrients) for more than a few minutes, they starve to death. This causes immediate disability of the function which is controlled by the affected brain tissue. (E.g.- paralysis, speech, sight, etc.)

We will discuss the most commonly occurring cerebrovascular diseases, Stroke and AVMs.

Stroke is a common name for ISCHEMIC STROKE, TRANSIENT ISCHEMIC ATTACK (TIA) and HEMORRHAGIC  STROKE

ISCHEMIC STROKE (the most common form of stroke). The cause is usually atherosclerosis in one of the carotid arteries in the neck. These arteries carry blood from the heart to the brain. When plaque forms at the location of the sclerosis, it reduces blood flow, causing blood turbulence. This is a process that easily results in the forming of a blood clot (thrombus), which may then swim further in the blood stream until it gets stuck somewhere in the brain, cuts off blood supply and a stroke is the result. Not only a thrombus but also an embolus can cause the same effect. An embolus often develops in one of the heart chambers due to a calcified valve. When the clot (embolus) gets loose and is taken with the blood stream to the brain, it will also cause stroke.

TRANSIENT ISCHEMIC ATTACK  (TIA). The cause is usually the same as described above for Ischemic stroke, but the obstruction of blood supply in the brain is not as severe. A patient suffering a TIA has stroke-like symptoms but they may slowly disappear after an hour to a day. Sometimes a TIA precedes a stroke attack.

HEMORRHAGIC STROKE is caused either by the rupture of a weakened blood vessel in the brain, or by an aneurysm, or by an AVM (see next paragraph). If the cause is a rupture, blood will freely bleed into the surrounding brain tissue. This bleeding can compress other blood vessels in the affected area and thereby deprive brain tissue of proper blood supply. An aneurysm is a ballooning part of a blood vessel, due to weakening of the vessel wall. Consequently that part is prone to rupture with a bleeding as a result. Hemorrhagic strokes are likely to affect a larger area of the brain than Ischemic strokes. Their symptoms are often more severe and more sudden as well as is their fatal risk of death.

ARTERIO-VENOUS MALFORMATION (AVM)

An AVM is an abnormal cluster of vessels, which short circuit between arterial and venous blood flow. Brain cells, like all body cells, are nourished via capillaries; the tiny vessels at the end of arteries. The return of used blood back to the heart also starts here, where capillaries form into veins. An AVM bypasses the capillaries. Its cluster of abnormal vessels can put strain on surrounding tissue. Bleeding of an AVM-vessel can occur with the result as discussed above.

Cause of AVMs - Although there is no clear proof, doctors suggest that most AVMs develop during the pre-natal period. As the symptoms are usually minor during childhood and early adulthood, they are often not detected early. There is no indication which shows relation to family history. Patients with an AVM often suffer from persistent headaches.

Note on Brain Tumors

A tumor is an abnormal mass of excessive multiplying tissue cells. They can be benign or malignant, but all have in common, that they put strain on surrounding brain tissue and its supplying blood vessels. Therefore their symptoms are comparable with those of erebrovascular diseases.

Diagnosis & Treatment of Cerebrovascular Diseases - Patients with symptoms of suspected stroke as well as AVM undergo several diagnostic imaging techniques, which include:

Computed Tomography (CT or CAT scanning) - Using X-rays, the machine produces sliced images of the subject under investigation, which show its internal structure. Images can provide information as to whether the patient suffers an Ischemic or a Hemorrhagic stroke, or AVM.

Magnetic Resonance Imaging (MRI) - Makes use of a very strong magnetic field and radio- frequency pulses. The technique exploits the magnetic properties of atomic nuclei. Its added value to CT lies in its sensitivity to reveal subtle chemical changes in diseased tissue.

MRI produces CT-like sliced images, which (depending on the field strength of the magnet) provide high resolution information. Unlike X-ray based imaging techniques, MRI is not harmful to living cells.

X-ray Angiography - Blood and blood vessels are invisible on X-rays. To visualize them, dye (a liquid contrast material containing iodine) is injected through a catheter into the bloodstream, while exposures are made. The images provide detailed information about the source, severity and location of an obstruction, aneurysm or AVM.

Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) - Both techniques involve injection of an isotope (a radioactive substance) into the bloodstream. The isotope emits radiation, while traveling through the area of interest, which is collected by a radiation detector. The produced images show information about brain tissue that has been injured or affected by a stroke or a bleeding.

Treatment & Recovery

The cerebrovascular diseases discussed above are life threatening and more often than not cause sudden death. Survival and successful treatment are highly dependent on the earliest possible detection of their symptoms and immediate medical treatment. Treatment depends on a precise diagnosis and information about what exactly is happening. When stroke is caused by a thrombus or embolus, treatment will focus on removing the obstruction by a local injection of a drug that breaks up the clot and restores blood flow. To be effective, it needs to be done within a few hours after the first symptoms of stroke are detected.

NOTE   

As one gets older the risk of atherosclerosis increases and with it the risk of a thrombus forming. Overweight, high blood cholesterol, high blood pressure and family history are some of the factors which increase the risk.

Statistics show that about 80% of recorded strokes are Ischemic Strokes, caused by a thrombus or embolus.

As said before, a thrombus usually originates from a sclerotic area in one of the carotid arteries, while an embolus is often caused by a calcified heart valve. By listening with a stethoscope to the heart sounds, a cardiologist can detect valve abnormalities. Blood flow and obstructions in the carotid arteries can easily be shown with ultrasound imaging, which is painless and non-invasive.

Both checks are not expensive and may be suggested on annual basis for those who consider themselves candidates.

Treatment of Hemorrhagic Stroke, caused by bleeding, aneurysm or AVM, is more complicated and often involves surgical clipping of the aneurysm, removal of the AVM as well as intervention (embolization of feeding vessels) techniques and even combinations of intervention and surgery. Which technique is chosen depends on location and accessibility without damaging intact brain tissue.

Appendix

Heart disease is a very much feared illness. Many people fall victim to it and too often it causes sudden death, which in many cases could be avoided if we had better knowledge about its symptoms. Besides congenital heart defects (born with the defect), which are usually detected early due to good medical services for newborns, we talk about acquired heart disease.

The most common and dangerous form of acquired heart disease is ANGINA or fully Angina Pectoris, which is a symptom for ischemia = insufficient blood supply.

Stable Angina  Stable Angina causes chest pain when the heart muscle does not receive enough blood (oxygen) for the work it needs to do. During physical exercise, but also during strong emotions, or being exposed to big differences in temperature, the heart rate increases (the heart works harder) and consequently needs more food (blood, oxygen). If the supply is not sufficient, due to obstructions in coronary arteries, it causes chest pain. When the patient returns to rest and the heart rate lowers, the chest pain reduces and usually disappears. This is a typical symptom for angina pectoris and is called “STABLE ANGINA”

It will now be clear that Stable Angina is predictable. The patient should see a cardiologist as soon as possible, but stable angina is not immediately life threatening.

Unstable Angina Absence of sufficient blood supply is also the reason for chest pain, but it occurs at any time, often during the night when one is at rest. Unstable angina is therefore unexpected, unpredictable and much more dangerous. It is usually caused by severe obstruction of blood flow in a major part of the coronary arteries. The chest pain is more severe and more prolonged and requires EMERGENCY MEDICAL TREATMENT.

In the worst case unstable angina can lead to an acute infarction (decay of heart muscle tissue), followed by abnormal electrical pulses à ventricular tachycardia (fibrillation of the ventricles) à cardiac arrest and very soon sudden death.

Apart from the discussed cases, angina can also be caused by defects of the heart valves. Chest pain is a typical symptom of angina, however not every chest pain indicates angina. It is most important to consult a cardiologist as soon as possible if a patient feels the described discomfort. Knowing is better than guessing!

Following a clinical question and answer session, the meeting adjourned to the Alliance Cafeteria where members of the audience engaged Steven in more informal discussion over drinks and snacks.