Acute coronary syndromes

Question 1

describe the term acute coronary syndromes

Answer 1

This term covers a spectrum of acute cardiac conditions from unstable angina to varying degrees of evolving myocardial infarction (MI)

Question 2

how is unstable angina diagnosed?

Answer 2

history
ECG
troponin (no significant rise in
unstable angina)

Question 3

how is unstable angina clinically classified:

Answer 3

*Cardiac chest pain at rest
*Cardiac chest pain with crescendo pattern
*New onset angina

Question 4

how can acute myocardial infarction be diagnosed- ST elevation?

Answer 4

ST-elevation MI can usually be diagnosed on ECG at presentation

Question 5

how can acute myocardial infarction be diagnosed- non ST elevation?

Answer 5

*Non-ST-elevation MI is a retrospective diagnosis made after troponin results and sometimes other investigation results are available

Question 6

how can myocardial infarction be defined?

Answer 6

retrospectively as non-Q wave or Q-wave MI on the basis of whether new pathological Q waves develop on the ECG as a result of it

Question 7

what are ST MIs and LBBB MIs associated with?

Answer 7

with larger infarcts unless effectively treated (and therefore more likely to lead to pathological Q wave formation, heart failure or death)

Question 8

symptoms presenting for myocardial infarction

Answer 8

*Cardiac chest pain
* unremitting
*usually severe but may be mild or absent
*occurs at rest
*associated with sweating, breathlessness, nausea and/or vomiting
*one third occur in bed at night

Question 9

what does myocardial infarction usually cause?

Answer 9

-permanent heart muscle damage although this may not be detectable in small MIs
- early mortality
- late mortality

Question 10

what is a higher risk of myocardial infarction associated with?

Answer 10

higher age,
diabetes,
renal failure,
left ventricular systolic dysfunction (elevated NT- proBNP level)
and other risk factors

Question 11

which patients have the highest mortality risk?

Answer 11

Patients presenting with cardiogenic shock or requiring ventilation following out-of-hospital cardiac arrest have the highest mortality risk

Question 12

how are myocardial infarctions initially managed?

Answer 12

*Get in to hospital quickly – 999 call
*Paramedics – if ST elevation, contact primary PCI centre for transfer for emergency coronary angiography
*Take aspirin 300mg immediately
*Pain relief

Question 13

what hospital management is done for myocardial infarctions?

Answer 13

*Make diagnosis
*Oxygen therapy only if hypoxic *Pain relief – opiates/ nitrates *Aspirin +/- platelet P2Y12 inhibitor *Consider beta-blocker
*Consider other antianginal therapy
*Consider urgent coronary angiography e.g. if troponin elevated or unstable angina refractory to medical therapy

Question 14

what are the causes of ACS?

Answer 14

*Rupture of an atherosclerotic plaque and consequent arterial thrombosis is the cause in the majority of cases
*Myocardial infarction due to atherothrombosis is known as ‘type 1’ myocardial infarction
*Other causes of myocardial infarction usually fall under the umbrella of ‘type 2’ myocardial infarction

Question 15

what are the causes of type 2 MI

Answer 15

• Myocardial oxygen demand/supply mismatch caused by sepsis, acute lung pathology, thyrotoxicosis, pulmonary embolism, anaemia, haemorrhage or other causes of hypotension/hypovolaemia – underlying stable coronary artery disease may or may not be a contributing factor
• coronary vasospasm without plaque rupture
• drug abuse (amphetamines, cocaine)
• dissection of the coronary artery related to defects of the vessel connective tissue
• thoracic aortic dissection

Question 16

what is tako- tsubo cardiomyopathy?

Answer 16

Stress-induced cardiomyopathy that can masquerade as myocardial infarction.

Question 17

what causes tako- tsubo cardiomyopathy?

Answer 17

Often caused by acute stress such as extreme emotional distress in susceptible individuals

Question 18

what does tako- tsubo cardiomyopathy cause?

Answer 18

Causes transient left ventricular systolic dysfunction, typically ballooning of the left ventricular apex during systole that recovers over days or a few weeks with limited or no permanent damage

Question 19

what is troponin?

Answer 19

A protein complex consisting of troponin C, troponin I and troponin T that regulates actin:myosin contraction.

Question 20

what are Cardiac-specific isoforms of troponin T and troponin I?

Answer 20

are highly sensitive markers for cardiac muscle injury

Question 21

what is the Role of soluble platelet agonists in thrombus formation at site of vascular damage?

Answer 21

promote healing
prevent bleeding to death
platelets adhere and secrete agonists to activate other platelets and attract them such as ADP ( ADP is the target of the anti platelet plug)
forma plug in the breech- good when needed but bad when responding to atherosclerotic rupture

Question 22

fibronyltic system

Answer 22

e
n plasminogen
d I
o I
t I fibrin
h——->tPA—— I I
e Plasmin——–> I
l I
I Fibrin
u degradation products
m

Question 23

when is P2Y 12 Inhibitors used?

Answer 23

sed in combination with aspirin in
management of ACS = ‘dual antiplatelet therapy’

Question 24

what are the three oral drugs available of P2Y 12 inhibtors?

Answer 24

*Three oral drugs are available: clopidogrel, prasugrel and ticagrelor

PRASUGREL IS MOST EFFICIENT

Question 25

describe the effect of Clopidogrel and prasugrel

Answer 25

are thienopyridines that have an irreversible effect on platelets

Question 26

describe the effect of ticagrelor

Answer 26

Ticagrelor binds reversibly to P2Y12 receptors so has a more rapid offset of effect than thienopyridines

Question 27

what are the adverse effects common to all of P2Y12 inhibitors ?

Answer 27

• Bleeding e.g. epistaxis, GI bleeds, haematuria * Rash
• GI disturbance

Question 28

diosyncratic adverse effects of ticagrelor:

Answer 28

• Dyspnoea: usually mild and well-tolerated, but occasionally not tolerated and requires switching to prasugrel or clopidogrel
• Ventricular pauses: usually sinoatrial pauses, may resolve with continued treatment

Question 29

what are GPIIb/IIIa antagonists used with

Answer 29

*Used in combination with aspirin and oral P2Y12 inhibitors in management of patients undergoing PCI for ACS

Question 30

what increased risk do GPIIb/IIIa antagonists have?

Answer 30

*Increase risk of major bleeding

Question 31

what do anticoagulants target

Answer 31

Target formation and/or activity of thrombin

Question 32

what do anticoagulants inhibit?

Answer 32

• Inhibit both fibrin formation and platelet activation

Question 33

doses of anticoagulants varying on procedure

Answer 33

Fondaparinux (a pentasaccharide) used in NSTE ACS prior to coronary angiography = safer than heparins as low level of anticoagulation used
* Full-dose anticoagulation used during PCI: options are heparins (usually unfractionated heparin; some centres use enoxaparin, a low-molecular-weight heparin) or the direct thrombin inhibitor bivalirudin (expensive, little used now)
* High dose heparin used during cardiopulmonary bypass for CABG surgery

Question 34

what is given for initial pain relief in ACS?

Answer 34

morphine + metoclopramide, nitrates

Answer 35

• Initial pain relief if necessary – morphine + metoclopramide, nitrates
• Aspirin and P2Y12 inhibitor combination (assuming no contraindications
  and confirmed diagnosis)
• Anticoagulant: fondaparinux or heparin
• Consider intravenous glycoprotein IIb/IIIa antagonists for STEMI patient undergoing primary PCI
• Anti-anginal therapy – beta blocker, nitrates, calcium antagonist
• Secondary prevention – statins, ACEI, beta blocker, other antihypertensive
  therapy
• Heart failure patients – diuretic, ACEI, beta blocker, aldosterone antagonist (spironolactone, epleronone)
• Fibrinolytic therapy may be used for acute STEMI if primary PCI not available

Question 36

when is coronary angiography usually performed?

Answer 36

for patients with troponin elevation or unstable angina refractory to medical therapy

Question 37

what is the most frequent revascularisation procedure?

Answer 37

PCI

Question 38

Why may some patients have no obstructive coronary artery disease?

Answer 38

• Actual diagnosis not ACS
• Plaque rupture without significant stenosis and resolution of
  obstructive thrombus by the time of angiography
• Stress-induced (Tako-Tsubo) cardiomyopathy without obstructive coronary artery disease