Basic Cardiac Investigations

Question 1

What are the absolute contraindications to Treadmill testing

Answer 1

Acute Severe Cardiopulmonary disease

• HF
• PE
• IHD
• Arrhythmia
• Myocarditis/pericarditis

Acute aortic dissection

Question 2

What are the standard criteria for an abnormal ST-segment response during Treadmill testing

Answer 2

Horizontal or down-sloping ST depression of 1mm at the ST-60 or ST-80 point ( 60 or 80 mm distal to the J point) occurring during exercise or during the early recovery period.

Question 3

Describe risk stratification accomplished by Treadmill testing

Answer 3

High risk

One or more of at low level exercise (METs< 4, HR < 100, < 70% max HR):

• STD > 0.1 mV
• Persistent ischaemic response > 3 mins after exertion
• ≥ 5 abnormal leads
• STE > 0.1 mV
• Typical angina
• CPX induced decrease BP by 10 mmHg

Intermediate risk (METs 4 -6, HR 100 - 130, 70 - 85% max HR)

• STD > 0.1mV
• Persistent ischaemic response 1 - 3 mins
• 3-4 abnormal leads

Low risk (METs > 7, HR > 130, > 85% max HR)

• STD > 0.1mV
• Persistent ischaemic response 1 - 3 mins
• 1 - 2 abnormal leads

Question 4

What is the sensitivity and specificity of Treadmill testing for detecting CAD

Answer 4

Specificity - 77%

Sensitivity - 68%

50 % of patients with single vessel disease and adequate levels of exercise will have a normal stress ECG

Question 5

What is the alternative in patient’s unable to undergo Treadmill testing?

Answer 5

Dobutamine Stress Echocardiography (DSE)

Question 6

What is the sensitivity and specificity of DSE

Answer 6

Sensitivity - 72% of patients with CAD will be correctly identified

Specificity - 88% of patients without CAD will be correctly excluded

Question 7

What are the disadvantages of DSE

Answer 7

Expensive
Operator dependent
Less reproducible

Question 8

How is cardiopulmonary testing (CPX) different to treadmill testing

Answer 8

Treadmill test - risk stratifies a patient with regard to IHD

Cardiopulmonary testing (CPX) - evaluates both cardiac and pulmonary responses to exercise induced stress.

Question 9

What is the use of CPX

Answer 9

CPX testing provides an accurate, reproducible and objective measure of functional capacity.

How a patient performs during a CPX test has been shown to be a powerful predictor of outcome after major surgery.

Question 10

What are the overall physiological responses to exercise

Answer 10

1. Increase Ve
2. Increase Q
3. Increase OER
4. Decrease SVR

Question 11

Technique of Cardiopulmonary Exercise Test

Answer 11

12 lead ECG
Mouth piece
Bicycle ergometer/treadmill 10 minutes

Question 12

Define the anaerobic threshold

Answer 12

The anaerobic threshold (AT) is defined as the highest VO2 attained without a sustained increase in blood lactate concentration. VCO2 and minute ventilation increase rapidly relative to VO2 beyond this threshold.

As lactate accumulates, VCO2 increase rapidly relative to VO2 beyond this point

VO2 is plotted on the X axis and VCO2 is plotted on the Y axis. The point at which the VCO2 begins to increase more rapidly than VO2 is taken as the anaerobic threshold.

Question 13

What is a ‘low anaerobic threshold’ and what are the implications of this

Answer 13

< 11 ml O2/kg/min is low AT

Powerful discriminator of mortality for elderly patients undergoing major abdominal surgery identifying patients who may benefit from preoperative optimisation and postoperative monitoring in intensive care.

Question 14

What is the negative predictive value for a DSE

Answer 14

93 - 100% negative predictive value

Question 15

How many stages does the Bruce protocol consist of and how long is each stage

Answer 15

7 stages
3 minutes each

Each stage increases speed by 1.2 kmph and gradient by 2%