Heart Attack – Diagnosis, Symptoms, and Treatment

What is a Heart Attack?

A heart attack is a medical condition characterized by the blockage of an artery supplying the heart – this results in cardiac injury and death of heart muscle tissue (myocardial infarction).  This condition is a medical emergency and represents the most common cause of death in the United States.  It can lead to sudden death, life-threatening abnormal heart rhythms (arrhythmias), and heart failure.

What Causes a Heart Attack?

A heart attack is caused by a sudden blockage of blood flow through an artery supplying the heart.  The arteries providing blood supply to the heart are called coronary arteries.  People with risk factors can develop the buildup of fatty plaques in the walls of the artery. These risk factors typically include:

• Smoking history
• Family history of heart disease or stroke
• High blood pressure
• Elevated cholesterol
• Advanced age
• Diabetes mellitus

Fatty plaques (atheromas) begin forming arteries starting as early as age 20.  Over time, patients with risk factors get progressive plaque formation with resultant narrowing of the arteries. This results in reduced blood flow to organs such as the heart – especially during physical activity and exercise.

If a plaque in the coronary artery ruptures, this can lead to a blood clot formation that blocks the heart muscle’s blood supply.  If the heart muscle is injured, it may not be able to pump as effectively, which leads to heart failure.  Plaque rupture in a major artery supplying the heart – such as the left anterior descending artery (LAD) – can result in sudden death, heart failure, cardiac shock, or life-threatening arrhythmia.

How Common is a Heart Attack?

Approximately 15.5 million Americans ≥20 years of age have coronary artery disease.  A heart attack is the number one cause of death in the United States in men and women of every major ethnic group – it is responsible for more than 600,000 deaths per year.  About 785,000 Americans experience their first heart attack every year.  A heart attack is particularly prevalent in the elderly population.

Signs and Symptoms

The most common symptoms of a heart attack include:

• Chest pain – often radiating to the left arm, neck, or jaw
• Chest pressure – the feeling of an elephant sitting on the chest
• Difficulty breathing
• Nausea & vomiting
• Profuse sweating
• Dizziness

Chest pain is often characterized as a pressure sensation that radiates to the left arm, neck, or jaw.  Symptoms may occur at rest.  They may also occur with exertion – but do not generally resolve after taking 3 doses of nitroglycerine.  This is the key distinction between a heart attack and stable angina – the latter is chest pain that occurs with exertion but improves with rest or nitroglycerine.  An additional feature is that the pain progressively gets worse – a term referred to as crescendo angina.

Your doctor will often evaluate for specific findings on your physical examination, such as:

• Abnormal vital signs – low blood pressure, irregular heart or respiratory rate
• Alertness & mental status
• Heart rhythm abnormalities (arrhythmias)
• Heart murmurs – may suggest heart failure or heart valve dysfunction
• Signs of heart failure - fluids in the lungs & leg swelling

Diagnosis

A heart attack is diagnosed based on symptoms and physical examination and confirmed with EKG and cardiac enzymes.  EKG is a study that evaluates the electrical activity of your heart.  Cardiac enzymes are molecules released by the heart muscle tissue – they are typically elevated in a heart attack setting.

Minor heart attacks are called non-ST elevation myocardial infarctions – these are still considered severe heart attacks – but they have a better prognosis as the entire heart wall muscle is not damaged.  Major heart attacks are called ST-elevation myocardial infarctions – these heart attacks are characterized by complete infarction of the heart wall muscle, which often has a poor prognosis.

Sometimes the diagnosis of minor heart attack is not clear – in these cases, your cardiologist may obtain a stress test to categorize your risk for heart attack.  During a stress test, you may be required to walk or run on a treadmill while your vital signs and EKG are being recorded.  Suppose you have chest pain, abnormal EKG findings, or cannot achieve a specific heart rate and blood pressure. In that case, the cardiologist will usually perform an ultrasound of your heart (echocardiogram) to assess your cardiac structure and function.

The evaluation of heart attack usually also requires the following blood tests: CMP (comprehensive metabolic panel), CBC (complete blood cell count), thyroid function (TSH, T4), and coagulation studies (PT/INR, PTT).  They will also check your cholesterol levels and screen for diabetes.

Heart Attack Treatment and Medication

Major heart attacks (ST-elevation myocardial infarctions) often result in heart failure, cardiac shock, life-threatening arrhythmias, and sudden death.  These types of heart attacks require immediate percutaneous coronary intervention (PCI).  PCI is performed in a cardiac laboratory.  During the procedure, an interventional cardiologist inserts a catheter into an artery in the groin or wrist.  They then advance the catheter to the arteries in your heart.

Once inside the coronary arteries, they can inject dye to visualize any obstruction or blockage in the arteries.  If they see a blockage, they can use a balloon to open up the blockage.  Sometimes they also deploy a stent made of either bare metal or drug-eluting material.  Some patients with severe disease involving three or more coronary arteries require a coronary artery bypass graft (CABG) – heart bypass surgery.

Your cardiologist may also administer one of the following antiplatelet agents during the procedure:

• Aspirin
• Plavix (clopidogrel)
• Effient (prasugrel)
• Eptifibatide (integrilin)

Suppose you are at a hospital that does not provide PCI. In that case, your emergency physician may administer a medication called tissue plasminogen activator (t-PA) – this rapidly acts to open-up any blood clots in the heart’s arteries.

Patients with minor heart attacks also typically undergo percutaneous coronary intervention, but it is not as urgent in most cases than major (ST-elevation) heart attacks.  Minor heart attacks are usually initially treated with blood thinners such as intravenous heparin or Lovenox (enoxaparin).  Patients also typically receive intravenous nitroglycerine to reduce blood pressure and promote blood flow to the coronary arteries.

These medications may also be prescribed to reduce cardiovascular risk factors such as high blood pressure and diabetes:

• Cholesterol-lowering therapy
  • Lipitor (atorvastatin)
  • Lescol (fluvastatin)
  • Mevacor (lovastatin)
  • Pravachol (pravastatin)
  • Crestor (rosuvastatin)
  • Zocor (simvastatin)

• Antihypertensive agents
  • Beta-blockers - Toprol (metoprolol), Coreg (carvedilol)
  • Angiotensin-converting enzyme (ACE) inhibitors - Zestril (lisinopril)
  • Angiotensin receptor blockers (ARBs) - Diovan (valsartan)

If you have diabetes, they may also recommend drugs such as Glucophage (metformin), Glucotrol (glipizide), Januvia (sitagliptin), or even insulin.

References:

1. Levine GN, Bates ER, Blankenship JC. 2015 ACC/AHA/SCAI Focused Update on Primary Percutaneous Coronary Intervention for Patients With ST-Elevation Myocardial Infarction: An Update of the 2011 ACCF/AHA/SCAI Guideline for Percutaneous Coronary Intervention and the 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. J Am Coll Cardiol. 2016 Mar 15;67(10):1235-50. - https://www.ncbi.nlm.nih.gov/pubmed/26489034
2. Bainey KR, Mehta SR, Lai T. Complete vs culprit-only revascularization for patients with multivessel disease undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: a systematic review and meta-analysis. Am Heart J. 2014 Jan;167(1):1-14.e2. - https://www.ncbi.nlm.nih.gov/pubmed/24332136
3. Braunwald E, Morrow DA. Unstable angina: is it time for a requiem? Circulation. 2013 Jun 18;127(24):2452-7. - https://www.ahajournals.org/doi/full/10.1161/CIRCULATIONAHA.113.001258