Stress testing patients on oral dipyridamole

Dr Parthi ArumugamConsultant Nuclear PhysicianNuclear Medicine CentreManchester Royal Infirmary

Parthi Arumugam

Case history

71 year old male Typical angina Peripheral vascular disease Risk factors for CAD

Hypertension Diabetic Current Smoker Raised BMI

Parthi Arumugam

What is the next line of investigation ?

Exercise testing Myocardial perfusion imaging Dobutamine stress echo CT Coronary angiogram Invasive Coronary angiogram

Parthi Arumugam

Based on NICE guidelines on chest pain of recent onset 1, this patient has a high pre test likelihood of CAD so invasive coronary angiogram should be considered.

The patient decided to have a functional test, so based on local availability, MPS was ordered. CTCA is also a suitable alternative.

So all responses are potentially correct.

1.NICE clinical guidelines 95 http://www.nice.org.uk/nicemedia/live/12947/47938/47938.pdf

Parthi Arumugam

He was booked for an Adenosine Rubidium PET perfusion study.

He turned up for his appointment having forgotten to stop oral Dipyridamole.

Parthi Arumugam

What is the most appropriate stress modality?

Exercise High dose Adenosine Dobutamine Dipyridamole Cancel the test and rebook

Parthi Arumugam

Either exercise or Dobutamine stressing could be employed but there are practical issues when used in conjunction with Rubidium imaging.

Cancelling the test is an option but would inconvenience the patient.

IV Dipyridamole was used.

Parthi Arumugam

IV Dipyridamole is a safe and efficacious in patients who are on oral dipyridamole2.

The protocol was completed without any significant side effects or ischaemic symptoms.

2 ASNC guidelines http://www.asnc.org/imageuploads/ImagingGuidelinesStressProtocols021109.pdf

Parthi Arumugam

Stress

Rest

Stress

Stress

Stress

Rest

Rest

Rest

Parthi Arumugam

Scans shows extensive inducible ischaemia in the inferior, inferolateral and inferoseptal myocardium (involving 8/20 segments).

Parthi Arumugam

Absolute Blood Flow Measurement

Parthi Arumugam

Flow measurement showed global ischaemia with significantly reduced flow reserve in the RCA and LCx (normal flow reserve should be more than 2.0),with probable steal phenomena – resting flow more than stress.

Note there is reduced flow in the LAD territory where relative perfusion was ‘normal’.

Parthi Arumugam

Coronary Angiogram

Coronary angiogram showed occluded RCA, tightly stenosed LCx and moderate LAD disease, which correlates with the flow reserve measurement.

Patient has been referred for CABG.

Parthi Arumugam

Teaching points

IV Dipyridamole can be used in patients on oral dipyridamole.

Relative perfusion assessment can underestimate extent of ischaemia in patients with multivessel disease.