Unstable Angina/NSTEMI

Introduction

Acute coronary syndrome (ACS) is a term used to describe a range of conditions resulting from sudden reduction in coronary blood flow. The presence or absence of ST-segment elevation on presenting ECG indicates ST-elevation MI, or non-ST – elevation acute coronary syndrome (NSTE-ACS).

NSTE-ACS is further sub-divided into NSTEMI (non ST-elevation myocardial infarction) or Unstable Angina, depending on elevation of troponin.

  • NSTEMI: ECG does not show persistent ST elevation, but may show ischaemic changes such as ST depression or T-wave inversion. The ECG may also be normal. Serum troponins are elevated.

  • Unstable angina (UA): Is present in patients with ischaemic symptoms suggestive of an ACS and a normal troponin, with or without ECG changes indicative of ischaemia (ST-segment depression or new T-wave inversion). It is largely a clinical diagnosis

Since an elevation in troponin may not be detectable for up to 4-8 hours after symptoms onset, UA and NSTEMI are frequently indistinguishable at initial evaluation. The importance of serial troponins cannot be over emphasised.

Risk Factors

 

Modifiable Risk Factors

  • Elevated cholesterol levels

  • Smoking

  • Hypertension

  • Diabetes mellitus

  • Obesity

  • Physical inactivity

  • Cocaine use

Non Modifiable Risk Factors

  • Atherosclerosis – History of angina, myocardial infarction, stroke, transient ischaemic attack, peripheral vascular disease.

  • Age > 65yrs

  • Male sex

  • Family history - MI in 1st- degree relative <55 years

  • Chronic kidney disease

 

Clinical Features

 

Symptoms

Pain

  • Chest pain that may radiated into the shoulder, arm, jaw, neck, or back.

  • Discomfort that feels like tightness, squeezing, crushing, burning, choking, or aching.

  • Pain that may have previously occurred only on exertion that now occurs at rest or minimal exertion and does not easily go away with nitrates = Unstable angina

  • Pain brought on by less activity, more severe, more prolonged or increased frequency than previously = Sometimes referred to as “crescendo” angina implying infarction is imminent.

Associations

  • Shortness of breath, sweating, nausea, pre-syncope, palpitations, belching, indigestion, fatigue

Signs

Most patients with non-ST elevation ACS will have a nil acute on physical exam

Assess for signs of modifiable risk factors. e.g. hypertension, hypercholesterolaemia

Signs of heart failure

  • Hypoxia, increased WOB, tachypnoea, 3rd or 4th heart sound, gallop rhythm, basal creps, elevated JVP

 

Differential Diagnosis

 

Cardiac

  • STEMI

  • Angina pectoris

  • Pericarditis

  • Myocarditis

 
 

Gastrointestinal

  • GORD

  • Gastritis

  • PUD

  • Oesophageal spasm

  • Cholecystitis/Biliary Colic

Vascular

  • Aortic dissection

 
 
 

Musculoskeletal

  • Costochondritis

  • Precordial catch syndrome

  • Trauma

Respiratory

  • Pneumothorax

  • Pulmonary embolism

  • Pneumonia

 

Neuropathic

  • Herpetic Neuralgia

  • Cervical Neuropathy

 

Clinical Investigations

 
Ischaemic+ECG.jpg

Bedside

ECG

  • 12 lead ECG and interpretation within 10 mins of arrival to ED to out rule STEMI which is a time critical, life threatening diagnosis.

  • dynamic ST-segment deviation (>0.5mm), or new T wave inversion (>2mm)

  • ECG may be normal or show minor changes in up to 50% cases.

VBG

  • acid-base status. ? high BM in poorly controlled DM

 
bloods%2B%252B%2Bpod.jpg

Laboratory

Serial Troponins

  • Used to distinguish NSTEMI (high troponin) from unstable angina (normal troponin).

  • Levels usually begin to rise around 2 -3 hours after onset of myocardial ischaemia.

    • Therefore serial troponins over at least 6 hours is necessary to out rule NSTEMI

  • Levels peak at approx 18 hours post pain and remain elevated for 14 days

FBC

  • Hb measurements may help to evaluate a secondary cause of NSTEMI (i.e., acute blood loss, anaemia)

  • ? thrombocytopenia to estimate risk of bleeding.

U&E

  • ? underlying CKD. Baseline renal function prior to commencing meds

K/Mg/Ca

  • Electrolyte derangements may predispose to cardiac arrhythmias.

1.8cm pneumothorax.png

Radiology

CXR

  • Assess for other diagnoses.

  • Assess for signs of heart failure

Echo

  • ? regional wall motion abnormality

  • Evidence of underlying heart disease e.g. LVF, LVH

Management and Disposition

 

Initial Resuscitation

  • ABC as clinically indicated

  • O2 to keep sats > 92%

 

Specific Treatment

  • In ED give a loading dose of dual anti-platelet therapy (Aspirin plus P2Y12 Inhibitor)

    • Aspirin 300 mg PO

    • Ticagrelor 180 mg PO

  • Consider Beta Blocker if BP and heart rate allow to decrease myocardial work load

Symptomatic Treatment

  • Analgesia PRN in the form of IV Opioid +/- sublingual nitrate

  • Anti-emetic PRN

 

Disposition

  • NSTEMI and Unstable angina patients need to be reviewed by and admitted under the cardiology service for in patient angiography

    • CCU bed with continuous cardiac monitoring

 

References

1.  B Wilkinson I, Raine T, Wiles K, Goodhart A, Hall C, O’Neill H. (2017) Oxford Handbook of Clinical Medicine. Oxford, UK: Oxford University Press.

2. Faselis C, Lieber J, Noto F. (2017) Step 2 CK Lecture Notes 2017: Internal Medicine. New York, US: Kaplan Medical.

3. https://bestpractice.bmj.com/topics/en-gb/151

This blog was written by Dr Maria Garcia and was last updated in Nov 2020

 Before you go have another look at the clinical case and see have any of your answers to the questions changed?