Percutaneous Transluminal Coronary Angioplasty (PTCA)
Commonly known as “balloon” angioplasty, PTCA is a procedure undertaken to reshape coronary arteries which have been severely blocked by atherosclerotic plaque so as to restore blood supply to heart muscle. A catheter with a deflated balloon at its tip is first inserted into an artery in the patient’s leg, and then gradually manoeuvred to the blocked or narrowed section of the affected coronary artery. After the balloon has been positioned to lie across the most severe area of narrowing, it is inflated and deflated several times. In the process, the pressure exerted by the balloon as it expands squeezes the cholesterol deposits against the wall of the coronary artery. This widens the opening of the affected artery, thus improving blood supply to the heart. After the procedure is completed, the balloon is deflated and the catheter removed. The patient is then closely monitored through X-rays of his reshaped coronary arteries to see if there is an improvement in blood flow. In general, the risk of major complications arising from angioplasty is low, with the procedure having a high success rate of approximately 90%. The extent to which a blocked coronary artery is widened by angioplasty may, however, vary significantly from individual to individual.
A patient who has undergone PTCA / “balloon” angioplasty may find his affected coronary artery becoming constricted again after a lapse of time. In this scenario, a stent in the form of a metallic coil or mesh may be inserted at that part of the artery which was previously widened by angioplasty so as to act as a “scaffolding” which keeps the vessel open. As with angioplasty, stent implantation has a relatively high success rate of close to 90%. Patients who have undergone this procedure may, however, subsequently have to take extensive blood thinners to prevent blood from clotting within their coronary arteries.
Coronary Artery Bypass Grafting (CABG)
A patient with angina may not be a suitable candidate for either angioplasty or stent implantation if he has atherosclerosis at several sites in his coronary arteries. In this case, CABG may be recommended.
This procedure involves creating a new route for blood to flow around the blocked part of each affected coronary artery. This is typically done by taking healthy blood vessels from other parts of the body (for instance, the saphenous veins in the leg or the internal mammary arteries inside the chest) and using them as grafts to bypass the obstructed portions of the coronary arteries. The blood vessels chosen as grafts are usually extra vessels which will not be missed when their blood flow is diverted. One end of the graft is attached to the aorta, and the other end to that part of the affected coronary artery which lies downstream of the blockage. In this way, oxygenated blood is able to flow through the coronary artery via an alternative route. If more than one blockage is present in the patient’s coronary arteries, more than one graft will be needed.
Following CABG, moderate recovery usually occurs by the end of the first month, with full recovery being attained within six months. If the operation is successful, the patient can expect a dramatic improvement in his cardiac condition.
Implantation of Electrical Devices
Two types of external electrical devices which are sometimes used in invasive cardiac therapy are pacemakers and defibrillators.
A pacemaker is an electrical device consisting of a lead in the form of a plastic tube, coupled with a metal core and a tip. It is typically used to regulate the heartbeat in patients with severe arrhythmia. The lead is inserted into the patient’s heart through a vein and then attached to a box with electrical circuits that constantly monitor his heartbeat. With each heartbeat, this electrical device waits for the next beat. If none occurs within a set period of the previous heartbeat, it emits a tiny electrical pulse which travels through the metal core of the lead to the tip, stimulating the heart and causing it to beat. A pacemaker can be either programmed externally to cause the patient’s heart to beat at a specific rate, or fitted with built-in sensors to regulate his heart rate according to his physiological needs. A pacemaker may also be fitted with either a single lead so as to stimulate the ventricles alone, or two leads so as to stimulate both the atria and the ventricles.
A defibrillator is a device used to pass high voltage currents through a critical mass of heart muscle so as to restore electrical conduction and coordinated contractions of the heart. Although defibrillators are usually used as external devices, they may sometimes be implanted within the patient’s body.