Technology is a great equalizer.Never in my dreams, I would have thought as I drive through the dense Nilgiris forest , a satellite located 36000 Km up in the sky would guide me through every turn and bend most accurately.
The curvy roads are coded with live traffic flow in Red ,orange & green . That’s “Google map” for you. (By the way, proud to note Google runs with an Indian CEO who hails from my city Chennai !)
Now , coming to academics , . .Some one thought, if the traffic in the entire globe can be monitored with few clicks, How about adding live traffic data to the otherwise dumb anatomical coronary angiogram images we get in a non Invasive CT scan ? We can even color code the different segments of coronary artery based on the velocity profile and pressure drop. That is CT- FFR . Now technology is available to get online live FFR as well. (Siemens )
Live coronary traffic blood flow
Heart flow the newest technology in coronary Imaging and non invasive Quantitative assessment is possible .It provides direct information about how to navigate the coronaries and intervene only the reddish areas leaving the greens untouched.
Principle
Its called computational fluid dynamics .A super computer calculates live FFR for the entire segment by measuring the drop in CT density data in Hounsfield units and translates into pressure equivalents and hence non invasive FFR.This modality has been approved by FDA.The heart -flow and Siemens has come out with onsite CT FFR.
Reality check :Have we conquered the coronary physiology ?
Trying to understand coronary flow with a engineering mind-set is Insulting the complexities of biology. Be reminded , Invasive FFR is assumed as a gold standard, Inspite of the fact that , its blessed with flaws in concept , techniques ,(Hyperemia vs no hyperimia) and lesional variation . Now ,what is the big deal , a non invasive CT -FFR is compared Impure gold standard and claiming a breakthrough ?
Of course,logic would suggest,if both FFRs are flawed why not use a less invasive one that is CT -FFR. It can atleast save time, cost, and potential procedure related issues.May be ideal in ACS situations were catheter FFR can destabilise the patient.Further, it can provide continuous live information in a hybrid lab , hence post procedure FFR is readily assessed . (Converting Red coronary into Green ones would become cardiologists new moto!)
Final message
The point of contention for the modern day cardiologist is ,they have realized (Not all ofcourse !) in a harsh way that , they must use a physiological confirmation of a lesion severity before indulging on fixing it with a metal. Whether CT-FFR will increase the number of angioplasties or reduce will remain a mystery . Whatever it does , it should do it for appropriate reasons . We know any technology has a shelf life and If MRI can provide the MRI-FFR (Journal of Cardiovascular Magnetic Resonance January 2014, 16:O55) , CT will be pushed back for obvious reasons (Prohibitive radiation hazard)
Reference
Dr.S.Venkatesan MD 
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