Acute Coronary Syndrome

Abstract

According to data published from the National Health and Nutrition Examination Survey (NHANES), it is estimated that 16.5 million Americans over the age of 20 have been diagnosed with Coronary Heart Disease. This was based on data collected between 2011 and 2014.  (Benjamin, Blaha, & Chiuve, 2017) Acute Coronary Syndrome (ACS) affects more than 900,000 a year in the United States. Of those 900,000 people who suffer an incident of acute coronary syndrome, close to 400,000 of those people die each year. Many of the people who are affected by ACS have coronary disease and may not even know it, this is much more common in men than in women. A heart attack occurs about every 40 seconds in the United States, according to the American Heart Association.

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Over the last 20 years the incidence pf ACS has decreased due to earlier treatment and prevention techniques with medical management of risk factors, people eating healthier and exercising more. Many physicians are treating their patients at high risk with a low dose aspirin and statins as preventative treatment. A clinical study has been performed on over 1600 patients which concluded that the preventative use of both aspirin and statin significantly reduces the risk of a ACS event taking place and if one does take place the outcome will be a milder event. (Weidmann, et al., 2018)

Acute Coronary Syndrome

Acute coronary syndrome (ACS) describes any condition relating to the heart where there is a lack of blood flow or a blockage of blood to the heart muscles. Some conditions that are included under this umbrella are a myocardial infarction (MI), otherwise known as a heart attack and unstable angina. ACS is an acute condition caused by a partial or full blockage in the coronary system of the heart. The longer you wait to treat one of these episodes, the more potential heart muscle that dies due to lack of blood flow from a full blockage. Even though ACS is considered an acute disease, it is a chronic problem, because it will never go away, there will not always be symptoms, but the underlying cause is still there. ACS is not an infectious disease, but it does tend to run in families and certain ethnicities have a higher risk of being diagnosed with ACS than others.

A MI is broken down into two major types, a ST elevation MI (STEMI) or a Non-ST elevation MI (NSTEMI). The MI is distinguished by whether or not the patient has a ST segment elevation on their ECG. A person who has had a STEMI has a complete blockage of one of the arteries in their heart and can be very serious, especially in younger patients, where there is not a collateral network of vessels. A NSTEMI is caused by a partial blockage of the heart, which of course is less severe than a STEMI, but if left alone and untreated can turn into a full blockage causing a STEMI.

Aside from having an ECG at the hospital patients experiencing symptoms of ACS will have blood drawn to assess their cardiac enzymes. Your cardiac enzymes could still be in the normal range even if you are having a heart attack. Hospitals usually do a series of cardiac enzymes, as they rise with time. There are several different cardiac enzymes that could be measured, and they include creatine kinase (CK), creatine kinase-muscle/brain (CK-MB), Troponin I and Troponin T. Depending on where you go for treatment, depends on which blood test they offer. They all have slightly different levels of sensitivity and all of have the potential to show a false positive reading because these enzymes are always in your body but increase during a cardiac issue. The cardiac enzymes and the ECG along with clinical symptoms should be considered when determining if this an episode of ACS.

Blockages to the heart are present in many people without them even knowing that they have a blockage. These are all partial blockages caused by plaque in the coronary arteries. Sometimes patients will feel pain in their chest, that lasts for a few minutes or longer. That may be your heart telling you that you have plaque in your coronary vasculature system and should be seen by a cardiologist. If the pain goes away after a few minutes many people just ignore this warning sign.

Figure 1

Summary of decreasing MI mortality risk and interventions through time

Signs and Symptoms

It is difficult for the lay person to differentiate between unstable angina and a heart attack. The primary signs and symptoms of a heart attack are chest pain or pressure (described by many as squeezing or an elephant sitting on their chest), which may or may not radiate to the neck, jaw and the left arm, nausea, palpitations, difficulty breathing, vomiting and breaking out in a cold sweat. Many people who have a history of indigestion, experience similar symptoms as a result of the indigestion and may overlook a heart attack. Heart attacks do not necessarily cause a cardiac arrest, although they can cause a cardiac arrest. In general, cardiac arrest is caused by an electrical rhythm problem in the heart called an arrhythmia.

Women and diabetics present slightly differently than males. Women and diabetics generally present with pain in the lower chest or upper abdomen, which radiates to the back, and is also associated with nausea, dizziness and lightheadedness along with shortness of breath.

Immediate care should be sought if you experience symptoms of ACS. The first step is to call 911. You do not want to take the chance and drive to the hospital. Once you arrive at the hospital and describe your symptoms to the emergency room, you shod receive an immediate ECG and a blood test to check your cardiac enzymes to see if they are elevated. Once these tests are performed, they will determine if you are having a definite ACS episode, possible ACS episode or have stable angina or a non-cardiac related chest pain. Anyone who has a possible or definite ACS episode will receive aspirin immediately and many will also receive nitroglycerin. Nitroglycerin will lower your blood pressure while dilating your blood vessels in your heart, so more blood can flow through the vessels lower the amount of damage which can be caused by a lack of blood flow.

Figure 1

Incidence of MI by age, sex and race (ARIC Surveillance: 2005-2013)

ARIC indicates Atherosclerosis Risk in Communities (Benjamin, Blaha, & Chiuve, 2017)

Table 2

Annual number of adults being diagnosed with a heart attack by age and sex per 1000 (ARIC Surveillance: 2005-2013 and CHS)

Cardiovascular Health Study (CHS) Source: National Heart Lung and Blood Institute. (Benjamin, Blaha, & Chiuve, 2017)

Risk Factors for ACS

There are many risk factors for ACS which include familial history (including ethnicity), hypertension, hypercholesterolemia, hyperlipidemia, diabetes, smoking, obesity, unhealthy diet (including a lot of fried foods), sedentary lifestyle and an age greater than 45 in males and 55 in females. People who are always under a lot of stress is also more at risk of having a heart attack. Your physician may recommend that you lower your stress in order to avoid having an additional heart attack or your initial heart attack. Certain races are more susceptible to having a ACS and they are African Americans, Native Americans, Native Hawaiians, Mexican Americans as well as Asian Americans. Females who had experienced preeclampsia or diabetes during pregnancy are also at a higher of developing ACS. It is very important to try to limit these risk factors, at least the ones that you can. The more risk factors that are present, increases your chances of developing ACS.

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In an article by Hodzic, he describes that the incidence of ACS can be affected by seasonal changes and the month of highest incidence is December and it affects more males than females. This paper shows that there is a correlation between the cold weather and potential changes in blood pressure and eating b=-habits during the winter months. (Hodzic, Perla, Iglica, & Vucljak, 2018)

Treatment

Historically, going back to 1940, the initial treatment for ACS was morphine and oxygen therapy. That therapy model was then added to by adding in the addition of aspirin and heparin in the 1960’s. In the 1970’s there was another increase to the therapy and that was to add nitrates, beta blockers and thrombolytics. In the 1980’s there was the beginning of Percutaneous transluminal coronary angioplasty (PTCA) and then eventually Percutaneous Coronary Intervention (PCI) treatment in the late 1980’s. This treatment has remained the standard of care along with the medications listed above and the addition of statins in the 2000’s. (Kline, Conti, & Winchester, 2015)

Currently, the initial treatment for ACS is medication and life-style changes. There are several different types of medications which may be prescribed for the treatment of ACS including anticoagulants, antiplatelets, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, beta blockers, calcium channel blockers, diuretics, anti-hypercholesterolemia medications and vasodilators. If those do not work, or if the symptoms do not become relieved, the next treatment is a diagnostic angiogram. An angiogram (catheterization) is an imaging test that uses x-rays to view your body’s blood vessels. Physicians often use this test to look for narrowed, blocked, enlarged, or malformed arteries or veins in many parts of your body, including your heart. The angiogram pictures allow your physician to see if there are any sections of your arteries that are narrowed as a result of plaque formation, and if so, determine the size of that blockage.

Depending on the size of the blockage in the heart, the physician may want to place a small stent in the narrowed arteries. The physician will use a small stent, tightly attached to a special angioplasty balloon, and guide it to the site of the blockage. The angioplasty balloon is inflated to stretch open the stent and blockage, increasing the size of the vessel back to its original size. The balloon is removed, and the stent remains permanently in place to hold the artery open. The implantation of the stent takes about 10-20 minutes.

Following the implantation procedure patients will be given aspirin and medication called a platelet inhibitor or anti-platelet to decrease the chance of formation of a blood clot. Patients will remain on aspirin indefinitely and the other anti- platelet (to help make your platelets slippery) medicine will be taken for at least 6 months.

Coronary artery stenting has evolved substantially since the first use of stents as an adjunct to balloon angioplasty in the early 1990s. The first stents implanted were called bare metal stents. It was noticed that these patients having similar pains after the implantation of their stents and when the physician preformed another angiogram, the patients had experienced a blockage in their previously implanted stent (restenosis). The performance of coronary stents has improved considerably, with stenting now the primary mode of revascularization in PCI.

PTCA has been widely used to treat subjects with symptomatic coronary artery disease (CAD). The major limitations of PTCA (abrupt closure, PTCA-induced intimal dissection and restenosis) have been addressed through the development of coronary stents. Steady improvements in stent design and adjunctive medical therapies over the preceding two decades have resulted in marked improvement in the safety and efficacy of PCIs. Estimates for in-hospital adverse events (death, myocardial infarction and stent thrombosis) are less than 1% in a recent U.S. multi-center registry.

Conventional PCI usually includes pre-dilatation of the target lesion prior to stent placement. This convention is dictated, in part, by the characteristics of first generation stents, which were higher profile, stiff devices that could not reliably be delivered to lesions. Additionally, these stents were hand-crimped onto balloon catheters, resulting in tenuous securement of the stents to their delivery systems. These features made pre-dilatation of the target lesion virtually mandatory to allow for stent delivery. Current generation stents and stent delivery systems increasingly allow for stent placement without pre-dilatation, a strategy known as ‘direct stenting’.

Direct stenting is currently employed in approximately 30-40% of PCI procedures and has been compared to conventional stenting (using pre-dilatation) in numerous observational and randomized studies using bare metal stents. Significant reductions in procedure time, radiation exposure, contrast administration and cost have been realized with the implementation of direct stenting compared to pre-dilation.

While PCI with stenting for CAD is associated with high rates of clinical success and low procedural morbidity, the risks of radiation exposure, contrast use and access site bleeding, as well as overall procedure costs in general, are not negligible. Clinical risks are incrementally higher in subjects with advanced age, multi-vessel disease requiring staged procedures, chronic kidney disease and peripheral arterial disease, making minimization of these risks of paramount importance.

Fixed-wire balloon catheters were introduced in the early days of PCI to provide lower profile options in the event of abrupt vessel closure and treatment of more complex lesions. As stents evolved throughout the 1990s, conventional PTCA balloons became mostly relegated to pre-and post-dilate lesions, which drove the market toward the use of guide wire-based devices. The need to re-cross lesions for further treatment (i.e. for post-dilatation or secondary stenting) additionally limited use of the fixed-wire platform.

Reports of wire fractures and difficulties with balloon deflation further dampened enthusiasm for these early fixed-wire systems. These early limitations of fixed-wire technology, along with the development of lower profile guide wire-based systems, resulted in the abandonment of the fixed-wire balloon catheter. However, in an era where more challenging lesions are being treated and even greater value is being placed on the clinical and procedural benefits associated with direct stenting.

A large body of published data now exists to demonstrate the superiority of drug-eluting stents, and particularly sirolimus and zotarolimus-eluting stents, over bare metal stents. (Garg, MB, ChB & Serruys, MD, PhD, 2010) However, in spite of the clinical efficacy of drug-eluting stents, there are ongoing concerns regarding the long-term biocompatibility of durable polymers, including polymers used on currently commercialized drug-eluting stents. It is believed that these polymers may, in the long term, incite inflammation, which could lead to late ‘catch-up’ (restenosis) or late stent thrombosis. Due to the concern with durable polymers, there is renewed interest in developing drug-eluting stents with bioresorbable, non-inflammatory coatings.

If the patient has very extensive disease, a coronary artery bypass grafting (CABG) needs to be performed. If your blockage is extensive and not amenable to PCI, then a CABG procedure would be performed. This can be done for all of the major vessels in the heart. If it is a very small vessel many times, the cardiologist will not treat it. To perform this procedure, the cardiologist removes a vein or an artery from another part of your vasculature system that is healthy and replaces the blocked section of the coronary vessel with this healthy vessel. It is sewn together to provide good blow flow to other areas of the heart in order to get good blood flow throughout the heart.

Discussion

Insurance companies offering screenings for cardiovascular disease is one way that the public health system can help with disease prevention. Teaching all people, especially those at higher risk lifestyle changes will help considerably lower risk factors for those who have the highest risk factors. Many people do not realize that their other medical problems contribute to their risk factor for ACS.

In a clinical study performed in Canada, it was noticed that the outcomes varied by where the providence the episode of ACS took place, as not all provinces were following the same treatment and follow-up regimen, including the use of dual antiplatelet therapy (DAPT) following the implantation of a coronary stent. (Fitchett, MD, et al., 2011)

A clinical study (EPISTENT) was performed in the US to compare the outcomes of 2399 patients who received a stent and was treated with a placebo medication, patients who received a stent and was treated with abciximab and patients who were treated with just a balloon angioplasty and abciximab. All of the patients in the study were followed for 6 months clinically and a sub study group of 899 patients were scheduled to have a diagnostic angioplasty at 6 months. At the 6-month timepoint patients were evaluated for MI and death. Of the patients who received the stent and the placebo medication, 11.4% had an additional MI or death within the first 6 months after the index procedure. Of the patients who received the balloon angioplasty and the abciximab medication, 7.8% had an additional MI or death within the first 6 months after the index procedure. Of the patients who received the stent and the abciximab medication, 5.6% had an additional MI or death within the first 6 months after the index procedure. The results of the sub-study also showed that the abciximab medication helped to reduce the incidence of restenosis of the stented lesion. (Lincoff, MD, et al., 1999)

The National Heart, Lung, and Blood Institute Dynamic Registry encompassed the treatment and outcomes of over 4600 patients who were treated with a PCI and compared the results by age group of the patient when they had their procedure. The patients were put in 1 of 3 age groups < 65, 65-79 and >79. The study showed that the incidence of ACS is higher in males than in females, until you reach the age group of > 85. It also showed that the outcomes of patients were good in all age groups, but patients in the > 85 age group tended to have more complications. This is also true in the general population, because they have more co-morbidities in that age group. The results of this registry show that stenting is safe in all age groups of people. (Cohen, MD, et al., 2003)

In a similar study performed in NY, from the NY Angioplasty Registry, patients were assessed in 3 age groups <60, 60-80 and >80. During 2000 to 2001, there were over 71,000 PCI’s performed in NY and register in this registry. The baseline demographics showed similar results as the above registry with the incidence of male to female ratio increasing as the age group increased. It also showed a 53% rate of smokers in the <60 age group compared to a smoking rate of 6% in the > 80 age group which is significant. This study also showed the coronary stenting by PCI is safe for patients in their 80’s, with very low mortality rates. (Feldman, MD, et al., 2006)

Conclusion

In order to obtain and maintain good outcomes, it is very important that people who are at risk for ACS be treated according to a standard of care, beginning with medical management of symptoms, reduction of those risk factors that can be mitigated (smoking cessation, weight loss, control of diabetic blood sugar, etc.) and either a PCI or CABG procedure, as necessary with a follow-up of cardiac rehabilitation. (Fitchett, MD, et al., 2011) As part of the cardiac rehabilitation program, there is a nutritionist who works with the patients to ensure that they are trying to help themselves by following a healthy diet.

References

  • Benjamin, E., Blaha, M., & Chiuve, S. (2017, March 7). Heart Disease and Stroke Statistics: 2017 Update. Circulation, pp. e146-e603.
  • Cohen, MD, H. A., Williams, MD, D. O., Holmes, MD, D. R., Selzer, PhD, F., Kip, PhD, K. E., Johnston, PhD, J. M., . . . Detre, MD, DrPH, K. M. (2003, September). Impact of age on procedural and 1-year outcome in percutaneous transluminal coronary angioplasty: a report from the NHLBI dynamic registry. American Heart Journal, pp. 513-519.
  • Feldman, MD, D. N., Gade, MD, C. L., Slotwiner, MD, A. J., Parikh, MD, M., Bergman, MD, G., Wong, MD, S., & Minutello, MD, R. M. (2006, November 15). Comparison of Outcomes of Percutaneous Coronary Interventions in Patients of Three Age Groups (<60, 60 to 80, and >80 Years) (from the New York State Angioplasty Registry). The American Journal of Cardiology, pp. 1334-1339.
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  • Hodzic, E., Perla, S., Iglica, A., & Vucljak, M. (2018, March 30). Seasonal Incidence of Acute Coronsry Syndrome and Its Features. Mater Sociomed, pp. 10-14.
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  • Lincoff, MD, A., Califf, MD, R. M., Moliterno, MD, D. J., Ellis, MD, S. G., Ducas, MD, J., Kramer, MD, J. H., . . . Topol, MD, E. J. (1999, July 29). Complementary Clinical Benefits of Coronary Artery Stenting and Blockadeof Platelet Glycoprotein IIb/IIIa Receptors. New England Journal of Medicine, pp. 319-327.
  • Weidmann, L., Obeid, S., Mach, F., Shahin, M., Yousif, N., Denegri, A., . . . Luscher, T. F. (2018). Pre-existing treatment with aspirin or statins influences clinical presentation, infarct size and inflammation in patients with de novo acute coronary syndromes. International Journal of Cardiology, p. https://doi.org/10.1016/j.ijcard.2018.10.050.

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