22 February 2019

During many types of heart surgery, blood which would normally pass through a patient’s heart is diverted outside of their body through a heart-lung bypass machine. 

The machine does the work that those organs would normally do: oxygenating blood and keeping it flowing around the body. 

This technique, known as cardiopulmonary bypass (CPB), allows the patient’s heart to be stopped and their lungs to be deflated, making it easier for surgeons to operate. 

However, there are a number of possible post-surgical complications to this method, including heart attack, stroke, major bleeding and kidney injury.

The new CoMICS (Conventional versus Minimally Invasive extra-corporeal circulation in patients undergoing Cardiac Surgery) Trial is a prospective randomised trial comparing the standard cardiopulmonary bypass technique to minimally invasive cardiopulmonary bypass, otherwise known as mini-bypass. 

Mini-bypass uses a miniaturised version of the conventional heart-lung machine, which has been manufactured to try and reduce the risk of complications. 

“Mini-bypass is a technique that we have been using at Royal Papworth Hospital for the past five years,” said Mr Narain Moorjani, Clinical Lead for Cardiac Surgery at Royal Papworth Hospital and Principal Investigator for the CoMICS Trial. 

“It differs from conventional cardiopulmonary bypass by reducing the dilution of circulating blood and has been shown to be associated with less of a need for transfusion of blood and blood products.

“In addition, it reduces the contact of circulating blood with air, thereby attenuating the inflammatory response of the body to the heart-lung bypass machine. This can potentially reduce associated impairment of a patient’s heart, kidney and lung function and ultimately shorten their hospital stay.”

Perfusion Manager Simon Colah and Senior Perfusionist Eve McPhilimey, who are responsible for operating the heart-lung machine during surgery, are working with Mr Moorjani on the trial along with Clinical Research Nurse Sarah Dennis, who plays a key role in recruiting patients. 

The study will be the largest ever trial assessing the potential benefits of mini-bypass, with over 30 centres from 11 different countries around the world contributing.

It will also look at the amount of blood products transfused in both groups and the overall resources used to treat patients during their time in hospital.

“We are honoured to be asked to be involved in this international study,” said Mr Moorjani. “We have recently recruited our first patient and are looking forward to recruiting more over the next few weeks and months.”