Diagnosing cardiovascular disease is becoming more sophisticated. Diagnosis begins with a medical examination and patient history. This procedure may be supplemented with a variety of tests that may confirm or refute the physician's suspensions of the presence of cardiovascular disease. Exercise stress tests using a motor driven treadmill with the patient hooked to an ECG have gained popularity in the last 10 years or so. It is a noninvasive test using surface electrodes on the chest that are sensitive to the electrical actions of the heart. Mechanical anomalies of the heart produce abnormal electrical impulses that are displayed on the ECG strip. These are read and interpreted by the doctors.
The treadmill "road tests" the heart as it works progressively harder to meet the increasing oxygen requirement as the exercise protocol becomes more physically demanding. This test is more accurate for men than women. The gender difference in response to the treadmill test is not fully understood, but it is believed that women's breasts and extra fat tissue interfere with the reception of electrical impulses by the chest electrodes.
In some cases a thallium treadmill test is required because it is more sensitive; however, it is also much more expensive. This involves the injection of radioactive thallium during the final minute of the tread mill test. Thallium is accepted, or taken up, by normal heart muscle but not by is chemic heart muscle. The absorption or nonabsorption of thallium can be seen on a television monitor. The thallium stress test increases diagnoses susceptibility to cardiovascular disease to approximately 90%.
Echocardiography is a safe, noninvasive technique that uses sound waves to determine the size of the heart, the thickness of the walls, and the function of its valves. Cardiac catheterization is an invasive technique in which a slender tube is threaded from a blood vessel in an arm or leg into the coronary arteries. A liquid contrast dye that can be seen on x-ray film is injected into the coronary arteries. X-ray films are taken through the procedure to locate where and how severely the coronary arteries are narrowed.
A variety of drugs have been developed that lower blood pressure and cholesterol, minimize the likelihood of blood clotting, and dissolve clots during a heart attack. Even aspirin sees to playa significant role in preventing a second heart attack or an initial heart attack. The more aspirin is studied, the better it appears to be.
Surgical techniques have also affected the treatment of cardiovascular disease. Coronary artery by pass surgery is designed to shunt blood around an area of blockage by removing a leg vein and sewing one end of a leg vein into the aorta and the other end into a coronary artery below the blockage, thereby restoring blood flow to the heart muscle.
The internal mammary arteries are also used for bypass grafts. In fact, many permissions consider these to be the ideal grafts. There are two internal mammary arms, but the one in the left side of the chest is preferred because it is closer to the coronary arteries. Many surgeons would rather not use both arteries in the same patient because the flow of blood to the chest impairs healing of the surgical wound. Also, fashioning bypass grafts out of these arteries is time consuming precision surgery, and there are only two of them and they do not reach all parts of the heart. The advantage is that 95% of them remain open 10 years after surgery.
Balloon angioplasty uses a catheter with a shaped shaped balloon at the tip. The catheter is positioned at the narrow point in the artery, and the balloon is inflated, which cracks and compresses the plaque, stretches the artery wall, and widens the blood vessel to allow greater blood flow. Laser angioplasty uses heat to burn away plaque if the catheter can be maneuvered into the correct position. This technology appears to be useful for patients with certain types of atherosclerotic narrowings or blockages. Coronary artherectomy, one of the newest techniques, uses a specially tipped catheter fitted with a high speed rotary cutting blade to shave off plaque.
Catheterization techniques are also used to implant a coronary stent in a diseased artery. The stent is a flexible, metallic tube that functions like a scaffold to support the walls of diseased arteries, thus maintaining an open passage for blood flow. Stents are positioned in such arteries by a catheter with a deflated balloon inside the stent. When correctly positioned, the balloon is inflated, causing the stent to expand. This action stretches the artery. Then the balloon is withdrawn, leaving the expanded stent behind to keep the blood vessel open.
This technique shows much promise, but there is a major limitation associated with the procedure: it increases the risk of blood clots forming at the site of the stent. To counteract this, patients are given blood thinning medications for 2 to 3 months following their implantation, and then they are maintained on aspirin thereafter.
Artificial valves have been developed to replace defective heart valves, and these work quite well. On the other hand, artificial (mechanical) hearts have not performed to expectation because modern technology has not produced a surface smooth enough to simulate the natural interior of the human heart. Blood clotting continues to occur at the valves in these devices. However, mechanical assist devices have been successfully used to aid a failing heart while the patient awaits a heart for transplantation.
Heart transplants have prolonged many lives. The outlook for patients has improved considering due to the development and use of cyclosporine, an antirejection drug. The 5 year survival rate is up to 72%.
Candidates for transplants are those whose hearts are irreversibly damaged with disease that does not respond to conventional treatment. Without a new heart, these people will die. In 1968, 23 heart transplants were performed, in 1993, 2298 were performed. The major problems associated with heart transplantation involve too few donors, procurement of a compatible donor heart, and the constant battle against organ rejection by the recipient.