A post-mortem examination found he died "most probably due to hypovolaemic shock - an emergency condition in which severe blood and fluid loss make the heart unable to pump enough blood to the body".
Mr MacDonald was one of 14,200 international participants taking part in the medical trial by Bayer Health Care, which manufactures a blood thinning drug called rivaroxaban.
In New Zealand and Australia Johnson & Johnson Pharmaceutical Research and Development conducted the trials, which had been approved by the Health Research Council and and an accredited ethics committee.
Participants were randomly blindly assigned to take one of two blood thinning treatments, rivaroxaban or warfarin, which can both cause "major bleeding", said the finding.
Because of his irregular heart rhythm, MacDonald met the study criteria and was invited to take part. A complication of his condition was the formation of blood clots, which can be treated by using an anticoagulant - blood thinner.
As part of the trial he was given information that included the warning rivaroxaban could increase the risk of bleeding.
In case of emergency participants were given a medic alert bracelet, wallet card with study details and contact number and it was added to patients' clinical notes.
On December 9, Mr MacDonald was travelling in a cycle lane behind a car when the driver "indicated for a couple of seconds before pulling to the left", according to a witness.
Mr MacDonald swerved left but was hit by the car, sending him off his scooter.
After the crash he told a paramedic he was taking a blood thinner as part of a medical trial but did not know which one and was rushed to hospital, in a stable condition.
The doctor treating him had not heard of rivaroxaban at the time which meant he "did not know that Mr MacDonald's blood might not clot normally and that it was thinned", said the finding.
Mr MacDonald was given blood and saline over the next four hours but bled profusely and became increasingly unstable.
At 9.15pm he went into cardiac arrest and became unconscious. Staff attempted resuscitation, but he died 90 minutes later.
In spite of the plans in place to notify medical staff of Mr MacDonald's participation in the trial, hospital staff remained unaware because they did not know clinical notes had arrived in ED, the emergency number on the medic alert bracelet was unavailable and ED staff did not see the wallet card, said the finding.
"I thus find had Dr Pearson known Mr MacDonald was or might have been on rivaroxaban, there was a chance his significant coagulopathy could perhaps have been reversed to some extent, but this chance was lost because Dr Pearson did not know," said Coroner Johnson.
"I thus find that Mr MacDonald's participation in the trial and being on the rivaroxaban arm of it contributed to his death."
Following a review by Christchurch Hospital since his death details on patients enrolled in trials is placed on a patient information system for medical staff but there were ongoing issues around consistency, an investigator found
Coroner Johnson also supported a number of other recommendations made in the review including, providing advice to trial participants about the effects of rivaroxaban, a back-up local contact system, and procedures around making written notes available.
She recommended information about trials of new medicines are made immediately accessible to all emergency department staff.
