Tuesday, October 23, 2012

Heart Attack

Heart Attack

What is a heart attack?
How common is a heart attack?
What are the symptoms of a heart attack?
What should be done if a heart attack is suspected?
What happens when a heart attack patient arrives in the ER?
How does "clot buster" treatment compare with angioplasty?
Why is primary angioplasty and stent not used in every case?
What happens after the patient is admitted to the hospital?
What happens after the first day?
What are the complications of a heart attack?
What medications will be prescribed after discharge?
What is a heart attack?  The heart is a muscular organ that pumps blood to the body at an average of 72 times per minute. The coronary arteries are responsible for supplying oxygen and nutrients to the heart muscle. A temporary decrease in blood supply can cause the muscle to "starve" for oxygen and result in chest discomfort or angina. A prolonged total loss of supply can cause irreversible damage of the heart muscle and produces a heart attack. To understand this, let us imagine that the heart is represented by a garden kept lush and green by water sprinkler system. The lawn is divided into three areas, each receiving water from a separate pipe or coronary artery, as shown on the left (below):

   Now imagine that one of these pipes is partially blocked by debris and rust. During a hot summer season, the rusty pipe is unable to keep up with the water needs of the garden. The area supplied by the partially blocked pipe begins to dry and turns brown, but is still alive, as shown on the right (above).. If the garden had symptoms, it would feel pain as it starves for water and nutrients.
   If water flow is now restored or increased, the garden once again turns green and the pain goes away. This is equivalent to angina. The big difference being that angina usually lasts only a few minutes, while the garden's "symptoms" occurs over a matter of weeks or months.
   Now let us imagine that the pipe becomes abruptly and totally blocked (above). Water supply to a section of the garden is completely and permanently interrupted. The grass turns brown and then dies. Once this happens, subsequent restoration of water supply will never return that section of the lawn to its original live, lush and green status. The plant life in one section of the garden has suffered the equivalent of a heart attack and turned into "scar tissue."

   The human heart, like the garden example, can experience prolonged "starvation" or angina before the affected muscle dies and turns into scar tissue. Scar tissue looses a muscle's power to pump. Thus, that portion of the pump becomes stiff, moves sluggishly and decreases the ability of the left ventricle (major pumping chamber of the heart) to efficiently pump blood to the body. The symptoms of chest pain preceding a heart attack can last from several minutes to a few hours.
    The pictures below demonstrate the different phases of atherosclerosis or blockage within a coronary artery. You may click on the left and middle button to stop and then play the slide show. The slides will "loop" continually. You may click on the "Rewind" button to restart the slide show from the beginning.
     The majority of heart attacks occur when a blockage plaque "ruptures" or develops a crack on the inner aspect of the blood vessel. Clot develops at this site and then grows to completely block the channel of the artery. This cuts off blood supply to the heart muscle supplied by that artery and results in a heart attack.
How common is a heart attack?: According to the AHA (American Heart Association; based on statistics from 1996) 1.1 million new and recurrent heart attacks occur per year in the United States. There are about 800,000 new heart attack survivors per year, according to the National Center for Health Statistics (NCHS). Following are additional important statistics provided by the AHA and NCHS:
  • There are 12 million victims of angina, heart attack and other forms of coronary artery disease (CAD) living in the USA.
  • 5.8 million are male and 6.1 million are female.
  • Approximately 225,000 people die, including 125,000 who die suddenly or before they reach a hospital. Most of these deaths are due to lethal irregular heart beats.
  • Heart Disease is the number one cause of death in the USA. This is followed by cancer, stroke, lung disease and accidents.
from 1986 to 1996 the death rate from CAD declined approximately 25%
What are the symptoms of a heart attack? A heart attack may be the first symptom of coronary artery disease in many patients. In others, it may be preceded by days, weeks, months or even years of angina.

   Classic or commonest signals of a heart attack consists of pressure- like, squeezing, or tightness feeling in the center of the chest that may radiate or move to the left shoulder and arm. In some, it may move to both shoulders and arms, the jaw, or between the shoulder blades in the back. If this is merely an angina warning, the symptom may go away in a few minutes and then return.
   Once a coronary artery is totally blocked, a heart attack takes place and the chest discomfort becomes more intense and persistent. The chest discomfort or pain may be accompanied by shortness of breath, unexplained anxiety (a sense of impending doom), weakness, marked fatigue, cold sweats, paleness and a feeling of skipped heart beats. It must be recognized that only one or some of these symptoms may accompany the chest discomfort of heart attack. Also, the symptoms may not be typical in some cases and shortness of breath, cold sweats or marked and sudden fatigue may be the only symptom. 
How should be done if a heart attack is suspected? When a heart attack occurs, it is extremely important to recognize symptoms and respond rapidly. Nearly 50% of patients suffering from a heart attack wait two or more hours before seeking medical help. This delay reduces the amount of heart muscle that can be salvaged with treatment, raises the amount of disability and increases the risk of sudden death.
   A person experiencing symptoms of a heart attack should be rushed to the nearest emergency room that offers round-the-clock cardiac care. Each person needs to recognize that their symptoms of heart pain may be different from the classical pattern described here and else where. If chest discomfort occurs during exertion, the activity should be stopped and the person be advised to lie down.
   If nitroglycerin tablets have been previously prescribed, a single tablet should be placed under the tongue and allowed to dissolve. if pain continues, take a second and third nitroglycerine tablet at five minute intervals. If pain is not completely relieved, 911 should be called. If time allows, notify the patient's physician so that he or she can make appropriate preparations for the patient's arrival in the emergency room.
What happens when a heart attack patient arrives in the ER? As noted earlier, a heart attack results when a coronary artery is abruptly and totally blocked. In the majority of cases, this occurs as a result of a blood clot. The goals of treatment are to quickly confirm the diagnosis, relieve the symptoms and open up the closed artery (with a "clot buster" medication or by means of angioplasty with or without stents).
Panoramic View of the Cardiac Section of an Emergency Room:

     Move your move cursor within the picture to pan left and right or pause the rotation. You may also do so by placing the mouse cursor within the image and moving it left and right or up and down. Each open door reveals a typical room with ready availability of emergency devices and medications.
   The initial evaluation of a patient with a suspected heart attack is usually accomplished within 10 - 20 minutes of arrival to the Emergency room.
Initial evaluation and treatment usually consists of:
  • History of illness is obtained by interviewing the patient and family. This helps the physician determine the likelihood and duration of the heart attack.
  • Physical Examination is performed, including recordings of the pulse rate, blood pressure, respiration rate and temperature.
  • EKG or electrocardiogram is a useful test in indicating the presence of a heart attack.
  • An intravenous line is placed.
  • Oxygen is started.
  • A nitroglycerin (NTG) tablet is placed under the tongue if the blood pressure is not too low. and the patient is continuing to have chest pain. Intravenous NTG may also be used in these cases.
  • Pain medication is delivered, usually via an i.v. line.
  • Aspirin is given by mouth.
  • Blood is drawn and sent "stat" to the laboratory. This helps confirm the early indication of a heart attack.
  • The safety and feasibility of using an intravenous "clot buster" medicine versus taking the patient to the cardiac
catheterization laboratory (if promptly available) is quickly assessed. If not contraindicated one or the other form of treatment is used in the majority of patients.
  • A portable chest x-ray is commonly obtained, particularly if the patient is having shortness of breath. In some cases, an echocardiogram may be obtained in the emergency room to asses the size of a heart attack.
     All the above measures may not be performed or needed in every case, and is individualized on the basis of the patient's symptoms and urgency of the situation.

    The video shown above was taken, during cardiac cath in a patient with angina. It shows a 70% blockage in the proximal or beginning portion of the right coronary artery (RCA) as shown by the arrow. The patient desired medical treatment and did well for a year.. You can also switch between the gray scale and a colorized version by clicking on the button.
    A year later, the same patient was admitted through the emergency room with a heart attack, Unfortunately, the patient continued to smoke and neglected his diet and exercise for several months. He was taken from the emergency room to the cardiac catheterization laboratory where the x-ray films showed total blockage of the right coronary artery. Click on the green arrow button to see how the blockage was treated in the laboratory. 
How does "clot buster" treatment compare with emergency angioplasty and coronary stenting? This is an excellent question for which there is no easy answer. Let us first look at intravenous thrombolytic (clot buster) treatment which became one of the more important advances in the treatment of heart attacks since its introduction. It offers the following advantages (Reference: ACC/AHA Guidelines for Patients with Acute Myocardial Infarction: Executive Summary, Circulation, Nov 1, 1996):
  • In comparison with standard medical treatment, thrombolytic therapy reduces the 35-day mortality (death rate) by 21%
This corresponds to an overall reduction of 21 deaths per 1000 patients treated in this manner.
  •  Time is of essence with the use of thrombolytic treatment. Higher benefits are achieved when it is given within 6 hours of the onset of heart attack symptoms. Best results are observed within two to three hours but continues to be beneficial even if started within 12 hours.
  • 35 per 1000 lives are saved when it is used within the first hour of symptoms. This drops to 16 lives saved per thousand if treatment is delayed for 7 to 12 hours.
  • Thrombolytic therapy benefits the patient regardless of age, sex or presence of risk factors for coronary artery disease.
  • Disadvantages include a small risk of a stroke (2%) with a little over half of them (1.1%) being due to bleeding. To place this in the proper perspective, the risk of a stroke due to thrombolytic treatment is far outweighed by the number of lives that are saved
   Next, let us examine the advantages of angioplasty performed as a primary procedure in the treatment of a heart attack. According to the recommendations of the American College of Cardiology and the American Heart Association Guidelines (above), primary angioplasty may be performed as an alert native to thrombolytic therapy in the following circumstances:
  • It can be accomplished in a timely manner by skilled and experienced staff.
  • There is prompt access to coronary bypass graft surgery.
   Advantages of Primary Angioplasty:
  • About half the patients treated with thrombolytic therapy continue to have a significant blockage (since the treatment breaks up blood clots but does nothing for the underlying blockage) and reduced blood flow in the affected artery. In comparison, blood flow is brisk and a mild or no blockage is left behind in over 90% of cases treated with primary angioplasty with or without stenting.
  • The mortality or death rate with primary angioplasty is 60% lower (Reference: JAMA 278:2093, 1997) than that achieved with thrombolytic therapy (4.4% compared to 6.5%).
  • The risk of stroke is reduced by more than 50%, compared to thrombolytic therapy.
  • The probability of having an open artery at 6 months with thrombolytic therapy alone is 59%. The odds improve to 87-91% at 3-6 months with primary angioplasty (References: NEJM: 328, 1993 and Circulation 90:156, 1994).
  • In studies where patients were randomized to thrombolytic therapy versus primary angioplasty, those treated with thrombolytic therapy required subsequent PTCA or bypass surgery in 30% of cases. In contrast, only 5% of patients treated with primary angioplasty required a subsequent procedure or surgery during the 3-6 month follow-up (Reference: Circulation 10[Suppl A] 12A, 1998).
  • With Primary Stenting in heart attacks, the success rate of the procedure is increased to >95% with less than 1% (0.8%) mortality (death rate) within the hospitalization period (Reference: Cathet Cardiovasc Diag 44, 118, 1998).
  • The restenosis rate (chance of blockage returning at same site) is around 25% at 7 months in cases of primary stenting for heart attacks (Reference: J Am Coll Cardiol 31, 23, 1998).
If Primary Angioplasty and Stenting is so good why is it not used in every patient with a heart attack? Excellent question! Since only 18% of hospitals are equipped to perform emergency angioplasty and stenting in patients with heart attacks, this form of treatment is not available in the remaining 82% of hospitals that admit patient's with chest pain. Remember that time is of essence in getting rid of obstructing blood clots and salvaging heart muscle. In most cases, the patient is far better off in receiving a "clot buster" medication in the emergency room if access to a hospital with a cardiac cath lab is not readily available.

   The x-ray video on the left shows a normal left ventricle as it fills and empties. The study was obtained during cardiac catheterization. Note how the top (anterior wall) and bottom (inferior wall) move towards each other as the heart pumps blood to the body.
    The video on the right shows the same left ventricle after a heart attack involving total blockage of the right coronary artery (RCA). Compared to the video above, please note that the inferior (bottom) wall, which is supplied by the RCA, is now barely moving.
What happens after the patient is admitted to the hospital with a heart attack? As noted earlier, most patients who are admitted to an ER (emergency room) in the US are considered for treatment with a "clot buster" medication or emergency angioplasty (with or without a stent). The exact form of treatment has to be individualized on the basis of each case, location of the ER and the duration of time in getting the patient to a cardiac catheterization laboratory. In some cases, because of a patients age and coexisting disease (terminal cancer, etc.), the family and patient may decide to use neither approach.
The first 24 hours in the hospital are usually spent in a coronary care unit (CCU) where the patient's heart rhythm is continuously monitored and the diagnosis of a heart attack is confirmed by a series of EKGs and blood tests. Most deaths from heart attacks occur during the first 24 hours and close observation is usually best provided in a CCU. Here, the patient receives appropriate medications by mouth and through an intravenous line.

Panoramic View of a Coronary Care Unit (CCU) Room:
You may move your mouse within the picture to pan left and right or pause the rotation. 

What are the possible complications of a heart attack and how are they managed? As noted earlier, the first 24 hours of a heart attack are the most critical. With the use of modern day interventions, the death rate from a heart attack has been brought down to around 5% in patients who are hospitalized with a heart attack. depending upon the location of the heart attack and the delay in seeking medical attention, the following complications may be seen:
  • Very slow heart beat or heart block (where electrical impulses from the upper chambers of the heart does not make it down to the lower ones). This is usually treated by using a temporary pacemaker.
  • Ventricular arrhythmias originating from the lower chambers of the heart. This usually responds to medications but may require an electrical shock to regulate. In some patients with serious and persistent irregular heart beats, an AICD (a specialized device that detects and corrects serious irregular heart beats and looks like a large pacemaker) may be needed to reduce the risk of sudden death).
  • Heart failure, where the pumping capability of the heart is significantly reduced by a large heart attack. This is more likely to occur in patients who have had one or more prior attacks. Heart failure (also known as congestive heart failure or CHF) is treated with oxygen and diuretics (a medication that increases the flow of urine and helps the patient get rid of excess fluids). Medications are also used to help reduce the workload of the heart and improve the strength of muscle contraction.
Shock may occur when a very large amount of heart muscle is damaged by a heart attack. It is a more severe form of heart failure. Depending upon the situation, this may be treated with intravenous medicines, insertion of an intra-aortic balloon pump It consists of a special balloon catheter that is inserted via the groin artery. The inflation and deflation of the balloon pump is timed by the patient's heart beat and helps support the circulation and gives the patient's heart to recover. The treatment of cardiogenic or heart shock may require that the pressure within the heart be monitored with the use of a special (Swan-Ganz) catheter. This is usually inserted through a little needle hole in the groin, or under the collar bone.
    A Swan-Ganz catheter and temporary pacemakers may be inserted in a special procedure room that is equipped with x-ray equipment and is shown below. A Swan-Ganz catheter can also be inserted in the CCU room without the use of x-ray.

Recurrent closure of a coronary artery after it has been opened up with "clot buster" medication or emergency angioplasty. Such patients are usually taken to a cardiac cath lab on an emergency basis and the artery reopened. In some cases, emergency coronary bypass surgery may be needed. The video above shows a surgeon suturing a bypass graft to a coronary artery.

   Other complications can include pericarditis (inflammation of the lining of the heart, heart rupture and a tear within the lower partition of the heart or of the muscle attached to a valve. The latter two complications usually require heart surgery for correction. 
What happens in the hospital after the first 24 hours of a heart attack? Depending upon how well the patient is doing, transfer to a "telemetry" floor is usually arranged on the second day. Unstable patients may remain in the CCU for one or more additional days.
If the patient is recovering nicely, he or she is ambulated in the hallway and may be seen by the cardiac rehabilitation team. The patient and spouse or family are provided with information that helps them understand what happened during the heart attack and what preventive measures are needed to avoid a second one. Instructions about dietary restrictions and an exercise regimen are also given. Depending upon the severity of the heart attack and promptness with which treatment was received, many patients are discharged in 2 to 4 days. Smokers are encouraged to quit tobacco use and supportive measures are recommended.
What medications are prescribed after a heart attack? Many of the patient's home medicines (for example those used to treat high blood pressure, diabetes, etc) are continued. Traditionally, the majority of patients also receive daily aspirin and nitroglycerine for "PRN" or as needed use. If there are no contraindications, most patients are also discharged on a "beta-blocker" medicine. This helps reduce the risk of a second heart attack and sudden death. However, a beta-blocker may not be used in patients with very slow heart beat, asthma and heart failure. Instead, patients with heart failure or reduced heart function may be sent home on a medicine known as an "ACE inhibitor" that helps reduce the workload of the heart. Patients with a high cholesterol level may be sent home on a medication to help control this problem.
Upon discharge, the patient will be given a follow-up appointment with the physician.

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