10.4 Cardiac Risk Stratification

Question 1

History

You are asked to see a 65-year-old patient with a known history of
hypertension, ischaemic heart disease, and congestive cardiac failure who had been booked for urgent below knee amputation due to acute ischaemia and gangrenous limb.

He is on ramipril, aspirin, and warfarin.

ECG shows irregular ventricular response around 125–140/min.

What are the issues presented to you?

Answer 1

• Elderly patient with significant comorbidities
• Emergency surgery
• Need for assessment of cardiac condition
• Rate control of atrial fibrillation
• INR optimised if abnormal
• High chance of sepsis, which needs to be treated

Question 2

Why would you need to assess
the cardiac status?

Answer 2

The purpose of preoperative cardiac risk assessment is to

1 * Identify patients at increased risk of an adverse
perioperative cardiac event.

2* Assess the medical status of these patients
and the cardiac risks posed
by the planned noncardiac surgery.

3. • Recommend appropriate strategies to
     reduce the risk of cardiac problems
     over the entire perioperative period and
     to improve long-term cardiac outcomes.

Question 3

How would you assess this patient’s cardiac status?

Answer 3

1. History and physical examination
2. Evaluation of functional status
3. Cardiac risk stratification using clinical predictors

Question 4

History and physical examination

Answer 4

to help to identify markers of cardiac risk
and assess the patient’s cardiac status.

High-risk cardiac conditions include recent MI,
decompensated heart failure,
unstable angina, symptomatic arrhythmias,
and symptomatic valvular heart disease.

Patients with severe aortic stenosis,
elevated jugular venous pressure,
pulmonary oedema, and/or third heart sound
on examination are at high surgical risk.

Question 5

Evaluation of functional status

Answer 5

The metabolic equivalent of a task (MET)

is a physiological concept expressing
the energy cost of a physical activity.

• 1 MET: Eat, dress, use the toilet, and walk indoors around the house
• 4 METs: Climb a flight of stairs (usually 18–21 steps) or run short distances
• > 10 METs: Participate in strenuous sports such as swimming and skiing.

on assessment, patients with < 4 METs are
considered to have poor functional capacity
and are at relatively high risk of a perioperative event,

while patients with > 10 METs have excellent functional capacity
and are at very low risk of perioperative events,
even if they have known CAD.

Patients with a functional capacity of 4–10 METs
are considered to have fair functional capacity and are
generally considered at low risk of developing perioperative events.

Question 6

Cardiac risk stratification using clinical predictors

Answer 6

Assessment of clinical predictors of increased perioperative risk for
MI, heart failure, and cardiac death

high risk:
Recent MI or severe angina
Decompensated heart failure
Severe valvular heart disease
Significant arrhythmias

Intermediate risk:
History of ischaemic heart disease
Compensated heart failure
Diabetes mellitus
Renal insufficiency (preop creatinine > 177 mmol/L)
Cerebrovascular disease

Question 7

investigations

Answer 7

1.ECG
* Preoperative resting 12-lead ECG can show
arrhythmias, ventricular hypertrophy, and ischaemic changes.

2. Echo
   * Preoperative noninvasive evaluation of ventricular and valvular function
   with echocardiography.
3. Stress testing:
   Exercise ECG and stress imaging
   (Dobutamine stress echo
   and dipyridamole thallium scan)
   provides an estimate of functional capacity,
   detects myocardial ischaemia,
   and assesses haemodynamic
   performance during stress.
4. Coronary angiography:
   Indicated in patients with evidence of high cardiac risk;
   identifies specific blood vessels with perfusion problems.
5. Brain natriuretic peptide (BNP):
   BNP appears to independently predict
   major adverse cardiac events in the first 30 days
   after vascular surgery and can significantly improve
   the predictive performance of the revised cardiac risk index.
6. Assessment of both cardiac and respiratory elements
   of exercise is done
   with cardiopulmonary exercise testing (CPEX).

Question 8

Discuss the cardiac risk scoring
systems in anaesthesia.

Answer 8

1. • New York Heart Association (NYHA) functional classification of heart
     disease
2. Goldman cardiac risk index

3.* Lee’s revised cardiac risk index: Six independent variables and each
assigned one point.

Question 9

• New York Heart Association (NYHA) functional classification of heart
  disease

Answer 9

I: No symptoms and no limitation of ordinary physical activity

II: Mild symptoms and slight limitation during ordinary activity

III: Symptoms and limitation in less than ordinary activity

IV: Symptoms even at rest

Question 10

Goldman cardiac risk index elements

Answer 10

nine multifactorial index of cardiac risk in the noncardiac surgery setting

Risk factors Points

1. Elevated JVP 11
2. Third heart sound 11
3. Myocardial Infarction in past 6 months 10
4. ECG: premature arterial contractions or any rhythm other than sinus 7
5. ECG: > 5 ventricular ectopics 7
6. Age > 70 5
7. Emergency procedure 4
8. Intra-thoracic, intra-abdominal or aortic surgery 3
9. Poor general health status 3

Question 11

Goldman - what does the score mean

Answer 11

The incidence of complications related to the score achieved is shown in the
table below.

Class Score Incidence of severe cardiovascular complications

I 0–5 1%

II 6–12 7%

III 13–25 14%

IV > 26 78%

Question 12

• Lee’s revised cardiac risk index:

Answer 12

Six independent variables and each assigned one point.

° High-risk surgical procedure

° History of ischaemic heart disease

° History of congestive heart failure

° History of cerebrovascular disease

° Preoperative treatment with insulin

° Preop serum creatinine > 2 mg/dL (177 mmol/L)

Question 13

Lees RCRI - What does the score mean

Answer 13

Class Points Risk

I 0 0.4%

II 1 0.9%

III 2 6.6%

IV > 3 11%

Question 14

How will you anaesthetise this
patient?

Answer 14

• Thorough preoperative assessment and preoptimisation as much as
  possible.
• Choice of anaesthetic:
  Regional techniques are not advisable due to coagulopathy and sepsis.

General anaesthesia with titrated doses of anaesthetics to avoid hypotension.

• Invasive monitoring, optimal analgesia, and treatment of arrhythmias are
  important.
• Assess the chances for postoperative complications, and admission to a
  high-dependency or intensive care unit would be ideal.

Question 15

What are the analgesic options?

Answer 15

• Simple analgesics like paracetamol followed by opioid analgesics.
• Anti-inflammatory drugs are relatively contraindicated due to sepsis,
  severe heart disease, and probable acute kidney injury.
• Nerve blocks can be given if coagulation is controlled. Femoral and sciatic
  nerve block gives pain relief for 12 to 24 hours.
• Local anaesthetic infiltration by surgeons especially to the cut ends of
  nerves reduces incidence of phantom limb pain.
• Catheter infiltration of local anaesthetic through a pump is another option.