Monday, June 21, 2010

Sudden Cardiac Death

Chest pain, the occurrence of which sends terrifying images to mind, of someone clutching his chest before finally falling to the ground in a heap… Yes, chest pain may indeed be the first sign of something gone awry, a condition called angina, in which the arteries which carry blood and oxygen to the heart are narrowed, the heart muscle is deprived of oxygen, lactic acid accumulates and stimulates pain nerves in the heart. While at rest, the blood supply may be adequate; however, whenever the heart pumps faster or harder, such as during exercise, after a meal, emotional stress (anger, excitement) or sexual activity, the increased need for oxygen is unmet by the already narrowed arteries, and therefore chest pain results. As the heart returns to its resting state, the oxygen demand is reduced and supply is again adequate, resulting in relief of chest pain. Hence angina is a reversible state, in which the pain is relieved when the activity or situation which produced it, is removed.

A heart attack, or myocardial infarction is what happens when the blood supply to the heart is cut off, usually by a blood clot within the artery. No oxygen reaches the heart muscle and the muscle cells die. If blood flow is restored quickly, permanent damage to the heart muscle can be avoided. Otherwise, the muscle cells die and are replaced by scar tissue over time. Indeed, the most common symptom of a heart attack is chest pain, lasting usually for more than 20 minutes. Common descriptions of the pain are "crushing”, "burning", "pressing" or  "heavy feeling". It is uncommon for the pain to be "poking", "pricking", "fleeting” or "ants biting”. Along with the pain, other symptoms may be cold sweat, breathlessness, giddiness, fainting, nausea and vomiting. Although the most common location of the pain is central or slightly to the left, uncommon locations may be in the upper abdomen, inner part of the left arm, left shoulder, neck or jaw. In myocardial infarction, the pain persists long after the initial activity or stimulus, which triggered the attack has ceased.

While pain is the most prominent symptom of myocardial infarction, a minority may present with no pain at all. Instead, other symptoms like breathlessness, fainting, palpitations or indigestion may be the only indication. Very rarely, the first, and only symptom may be collapse and sudden death. The unusual, or atypical symptoms, of myocardial infarction, are more often seen in women below the age of 65 years.

Usual investigations for chest pain include an electrocardiogram (ECG), echocardiogram (echo), cardiac enzymes (a blood test), chest X ray, exercise treadmill test, exercise perfusion scan (MIBI scan), exercise echo, CT scan and coronary angiography. Elderly or infirm patients who are unable to exercise may be tested using pharmacological methods (injection of drugs). An assessment of risk factors is mandatory. This includes enquiry into family history, smoking habits and checking the blood pressure, blood cholesterol, glucose, homocysteine, C reactive protein and other tests as indicated.

Once a diagnosis of myocardial infarction is made, it is a medical emergency, which must be treated as soon as possible to minimize the amount of heart muscle damage (hence, the adage, "time is muscle”). This includes the use of clot busting medication (thrombolytic drugs), emergency catheter procedures to open the blocked artery (angioplasty or stenting) or emergency heart bypass surgery.

With stable angina, there is time to do the various investigations and try medical therapy and assess the need for widening the narrowed arteries by angioplasty or heart bypass surgery.

Not all chest pain equates to heart attack or angina. Non-cardiac causes (i.e. not due to the heart) include musculoskeletal chest pain (due to muscle and ribcage), lung inflammation (pleurisy or pneumonia), pneumothorax (air leak in the lung), pulmonary embolism (blood clot in the lung), breast disorders (cancer, fibrocystic disease), aortic dissection (a split in the wall of the aorta) and shingles (herpes zoster infection) affecting the nerves supplying part of the chest wall. Lastly, psychological factors such as anxiety and panic disorders may play a role. Careful history, physical examination and appropriate investigations will help to delineate the actual cause by a process of elimination.

Article courtesy of
Dr Ruth Kam
Consultant Cardiologist

No comments: