What I should know about Acute Coronary Syndrome?

Posted on February 1, 2016

What is Acute Coronary Syndrome (ACS)

ACS is the medical abbreviation for Acute Coronary Syndrome, which includes a spectrum of conditions leading right up to full blown heart attack. The term ACS implies that the condition is unstable, evolving and unpredictable. As such, it is treated as a medical emergency. ACS includes Unstable angina, small Heart attack or a full blown Heart attack. A small Heart Attack occurs when only part of the heart muscle dies from lack of oxygen because the artery may only be 95-99% blocked. A full blown Heart Attack occurs when the full thickness of the same muscle dies when the same artery now becomes completely occluded.

The problem we face is in the early recognition of symptoms of ACS. If patients do not recognise early warning signs, they do not present themselves for treatment. The main problem is that there may be no warning signs at all in some patients when ACS first develops. That is why Heart Attack is aptly named the Silent Killer. Woman as a group need special mention. This is because similar symptoms in woman tend to be ignored or interpreted as non-specific pain. Worse still, it may be masked by depression in some of them. In my practice, patients still commonly have the mistaken impression that Heart Attacks occur only in old men.

Angina-the symptom preceding ACS

Chest tightness, chest pain at rest may be a harbinger of what is to come. This is known as Angina. A typical description is a sensation of stone pressing on the chest or a gripping sensation around the throat. More often than not, this may be accompanied by clammy sweating, difficulty breathing and fast pumping of the heart. This pain may radiate to the jaw, left arm, shoulder or back. There may also be unexplained feelings of anxiety and fatigue. Nitroglycerin is a medication often prescribed for the relief of chest pain. It relaxes spasm of the heart arteries. If such symptoms are temporary and relieved by nitroglycerin placed under the tongue, then it is considered Stable Angina and there is no need for hospital consult.

ACS-Unstable Angina, Heart Attack

I often tell patients that Nitroglycerin can be repeated once every five to ten minutes until chest pain resolves. If however, chest tightness or pain lasts more than half an hour, the Angina may be Unstable or may even be a full blown Heart Attack. In this case, patients must proceed to the nearest A&E without delay.

Being unstable, any component of ACS is potentially fatal. A common misconception is that Unstable Angina is a safer condition than a small Heart Attack, which in turn is safer to have compared to a big Heart Attack. This is a myth that must be dispelled. The whole spectrum is dangerous, because as I mentioned in the first paragraph, the condtion is evolving and unpredictable without treatment.

In Singapore, the SCDF ambulances have been equipped with monitors that can diagnose full blown Heart Attacks en route to the nearest hospital. Thus, interventional cardiologists (ie cardiologists who perform balloon and stenting) and their team can stand by to institute immediate treatment. The main aim is to open up artery blockages within 90 minutes of arrival to the hospital.

If it is not a full blown Heart Attack, the diagnosis will only become clear after a few hours of observation. That is why, the protocol in the A&E is to give Aspirin, the clot buster, and then perform repeated ECGs and blood tests. If ACS is excluded, patients can be discharged home, with a followup appointment at the cardiologist’s clinic. If ACS is diagnosed, they can then be admitted for treatment.

What causes ACS

The heart pumps an average of 80 beats per minute, requiring a steady supply of oxygen to function. There are three coronary arteries (heart artery) that supply oxygen to various parts of the heart muscle. Just like water pipes, they get clogged with plaque as a person ages. ACS is caused by blood clots forming over plaques within a coronary artery, interfering with the oxygen supply.

Plaque consists of a layer of fatty material that becomes fibrotic and calcified with time. It is covered by a fibrous cap. When plaque covers more than 75% of the lumen of the artery, oxygen supply to the heart muscle is impeded and the patient can experience Angina.

However, even before this occurs, minor plaques, ie, plaques covering less than 50% of the arterial lumen can also cause fatal problems. The fibrous cap can rupture and, like in a volcanic eruption, blood clots rapidly form over this and results in partial/complete occlusion of the artery resulting in a Heart Attack. If the blockage is anything less than 100%, some blood can still trickle through, this results in a minor Heart Attack. A major Heart Attacks occurs when the artery is 100% blocked.

Anyone with plaques are at risk of plaque rupture and hence Heart Attacks. The treatment is early use of clot busters like aspirin, Plavix and Heparin. Definitive treatment includes emergency angiogram, angioplasty and stenting.

Key Words

ACS(Acute coronary Syndrome): Sudden coronary occlusions that lead to dying of heart muscles
Coronary: Artery supplying heart muscles
Angina: Chest pain emanating from the heart
Plaque: Layer of fat, fibrous material and calcium in the wall of the coronary
Ruptured Plaque: Unstable plaque with blood clots
Interventional cardiologists: Subspecialty of cardiologists who perform angioplasty and stenting

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Lim Ing Haan Cardiology Clinic
3 Mount Elizabeth #04-02
Singapore 228510

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