Type 2 Diabetes: Preventing Complications
Understanding Heart Attack
By Arthur E. Fass, MD
The last decades have ushered in a new era in the treatment of heart attacks. Gone are the days of passive convalescence. No longer are doctors relegated to the role of concerned observers, powerless to alter the natural course of the illness. Today, heart attack victims are given a range of the most modern and aggressive treatments available in cardiology. Heart attack patients arriving in the hospital now have a greater than 90% chance of surviving the event. Most will go on to lead fully productive and active lives.
What causes a heart attack?
The crucial breakthrough in improving treatment was a superior understanding of the cause of heart attacks. Utilizing anatomic and angiographic studies, it is now known that heart attacks are usually caused by blood clots that block the flow of blood in a coronary artery. The clotting occurs when an underlying atherosclerotic plaque tears or erodes, exposing cholesterol and other clot-promoting substances to the bloodstream.
We do not know what specifically causes a coronary plaque to rupture and trigger a heart attack. Many plaques remain stable for years and never lead to a major clinical event. A great deal of research effort is now directed at attempting to identify vulnerable plaque and preventing it from causing trouble.
The role of risk factors
While a specific inciting cause in plaque rupture is often unknown, there is general agreement that certain risk factors predispose to coronary events. These include hypertension, cholesterol abnormalities, cigarette smoking, diabetes, obesity, and sedentary lifestyle. High levels of mental stress or anger may play a contributory role.
Rarely do risk factors occur in isolation. They are interrelated and tend to bunch together. For example, a sedentary life style is often associated with obesity and diabetes. One aspect common to all risk factors may be the inflammatory response. Inflammation is a complicated series of biochemical reactions mounted by the body in response to a variety of insults such as injury and infection. In a sense, the known coronary risk factors represent forms of physical or biochemical injury to blood vessels resulting in an inflammatory response. Inflammation, in turn, renders atherosclerotic plaques more vulnerable to rupture. It follows that by avoiding or minimizing these risk factors, one will lower the risk of heart attacks. It is tempting to think that by improving the biologic conditions in the coronary circulation that coronary plaques can be stabilized and not cause clinical problems.
An ounce of prevention
There is now overwhelming evidence that control of blood pressure, smoking cessation, and aggressive lowering of lipids will have major preventive benefits. Perhaps the most compelling evidence has accumulated in the area of lipid lowering. Treatment with statins has dramatically changed the cardiology landscape. These agents dramatically lower LDL (bad) cholesterol. They also have a variety of other beneficial actions including an anti-inflammatory effect.
Preventive measures, especially risk factor modification, have had a significant impact on the rate of heart attacks. Coronary mortality has declined about 20% during the past two decades. Contributing to this decline is a greater awareness of healthy diet and lifestyles.
When a heart attack strikes
It is the patient’s job to seek medical attention as soon as possible after symptoms occur. Classic symptoms of discomfort, pressure, or heaviness over the upper chest may be absent. Instead, shortness of breath, sweating, weakness or lightheadedness may be the only signs.
On presentation to a medical facility, symptoms are reviewed, vital signs are taken, and a focused examination is performed. An intravenous line is inserted, blood tests are drawn, and oxygen is administered. An electrocardiogram (EKG) is quickly obtained. The next phase of treatment depends on the EKG findings. If the typical EKG changes
of an acute myocardial infarction (heart attack) are present, the medical team will swing into action.
Opening the artery
The overriding aim is to restore blood flow in the blocked artery as soon as possible. This will limit damage to the heart muscle and avoid complications. Other treatments are designed to decrease the workload of the heart to minimize its oxygen demand. After protecting the heart with a beta-blocker (to lower pulse and blood pressure), a concerted effort is focused on dealing with the offending clot.
All available weapons are brought into the therapeutic arena. Aspirin will be given wiithout delay. This old remedy has potent inhibitory effects on platelet clumping. Even by itself, aspirin can decrease heart attack mortality by 20%. Another platelet inhibitor,
clopidogrel (Plavix) is also routinely administered.
The assault on the clotting mechanism will be expanded with heparin or one of its low-molecular weight derivatives. These agents interfere with the synthesis of fibrin, the reinforcing protein in clot formation. With a simultaneous attack on platelet aggregation, and clotting proteins, coronary blood flow will sometimes be restored. Often, however, additional measures will be necessary. It is at this point that subsequent treatment will be determined by the available facilities.
Clot-busters in the community
Heart attack patients in community hospitals without angioplasty laboratories who have not responded to the above treatments, will now receive intravenous therapy with powerful clot-busters known as thrombolytic agents. Numerous studies have documented the effectiveness of these agents in opening arteries clogged with a blood clot. The majority of patients will obtain prompt restoration of coronary blood flow with alleviation of symptoms and reversal of EKG changes.
Thrombolytic agents, originally introduced in the mid-1980’s dramatically improved the prognosis of heart attack victims. Mortality was reduced by about 40%. For the first time, doctors had the ability to actively alter the course of the disease. Several drawbacks, however, became evident with the thrombolytic approach. Some patients did not achieve clot resolution. Also, a small percentage of patients experience significant bleeding. The most serious is cerebral hemorrhage, a complication occurring in fewer than 1% of patients. Other patients are not candidates for this treatment because of bleeding problems, recent surgery, or history of stroke.
Mechanical options with angioplasty and stents
With the development of coronary angioplasty and stenting, another approach to treating heart attack victims emerged. Instead of thrombolytic therapy, the patient is taken directly to a catheterization laboratory to undergo coronary angiography. The blocked artery is then opened with a balloon angioplasty, usually followed by stenting (implantation of a metal scaffold to maintain artery patency). When performed promptly (i.e. within 90 minutes of arrival at the hospital) this technique has a certain advantage over thrombolysis.
There is a greater likelihood of opening the blocked artery and a slightly lower mortality rate. In addition, the entire coronary anatomy can be evaluated. There is a lower risk of significant bleeding and virtually no risk of intracranial hemorrhage. Because of these advantages, immediate coronary angioplasty has become the preferred treatment of heart attacks in hospitals having facilities to perform the procedure.
Should all patients presenting to a community hospital be transferred to another hospital for urgent angioplasty? The answer depends on the time required to transfer to the catheterization facility. If the transfer cannot be accomplished within 90 minutes, thrombolytic therapy should be given at the community hospital to restore coronary flow as quickly as possible. In practice it is usually not possible to transfer a patient to a receiving catheterization lab in the prescribed period of time.
Cardiologist’s comment:
Great strides have been made since the introduction of thrombolysis and primary coronary angioplasty. The strengths and limitations of each of these modalities are becoming better defined. Thrombolysis offers an immediate treatment that can be delivered at any hospital or even in the field by emergency medical personnel. It provides an opportunity for the most rapid relief of coronary obstruction and is non-invasive.
Primary angioplasty can open virtually all acutely blocked coronary arteries, but usually with a longer delay to treatment. As with any invasive procedure, complications can occur at arterial puncture sites. The angiographic dye can have a toxic effect on the kidneys, and considerable radiation exposure is required for the procedure. In addition, coronary stents require careful long-term management. Anti-platelet treatment with aspirin and Plavix must be continued for many months, and possibly indefinitely, to prevent sudden thrombosis (clotting) of the stent.
Research continues on the use of combined therapy — thrombolysis for immediate clot dissolving followed by angioplasty for more definitive treatment. Our improved understanding of coronary disease has opened exciting new opportunities in prevention and treatment. Hopefully, options will continue to expand as research is translated into
further clinical progress.
This article first appeared in the November/December 2006 issue of Heart & Health Reports. For a subscription, call 1-877-HEART-12.