Priority 21 from the Heart Surgery PSP

UNCERTAINTY: Do outcomes of heart surgery and follow-up time vary by postcode/location and how to reduce the variation? (JLA PSP Priority 21)
Overall ranking 21
JLA question ID 0088/21
Explanatory note Despite our search could not identify relevant sources, the effect of location on outcome in cardiac surgery is a rarely explored concept that could however change current practice, as highlighted in recent publications.
~ Are postcodes indicative of outcomes in cardiac surgery? Why does the follow-up periods vary so much, district to district? Is there any way to narrow the variation in outcomes across cardiac units? 
Evidence

No reference 

Health Research Classification System category Cardiovascular
Extra information provided by this PSP
Original uncertainty examples Are postcodes indicative of outcomes in cardiac surgical procedures? Why does the follow-up periods vary so much, district to district? ~ Is there any way to narrow the variation in outcomes across units? 
Submitted by 1 x patient, 2 x healthcare professional, 1 others 
PSP information
PSP unique ID 0088
PSP name Heart Surgery
Total number of uncertainties identified by this PSP. 45  (To see a full list of all uncertainties identified, please see the detailed spreadsheet held on the JLA website)
Date of priority setting workshop 11 July 2019