When LV fails the lung gets congested and flooded with blood . Similarly when coronary sinus , the major draining outlet of coronary circulation resists the incoming blood flow . . . myocardium will get congested !
This is the concept of retrograde perfusion in treating refractory CAD with angina . It is a double-edged concept. If the coronary sinus pressure is excessive it may interrupt even the normal flow .It should be optimal so that it prolongs coronary micro-circulation time without compromising ante-grade flow. .
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We know cardiac failure patients rarely complain of angina .
Why ? . . The myocardial congestion due to coronary sinus pressure is the most likely explanation.This goes well with the back flow concept in treating refractory angina.
While surgeons tried to link artery to vein , Interventional cardiologists were smart enough to occlude the coronary sinus partially , that will result in stasis of blood in coronary micro-circulation and hence facilitates oxygen extraction .
God is a master craftsman. Do not think there is only one access to coronary micro circulation.Apart form LCA and RCA there is a vast network of coronary veins traversing the delicate surfaces and grooves of the heart .
Remember ,they also reach the same micro vascular bed but in a different direction !
If we can exploit them for myocardial arterial perfusion we have a real breakthrough in our hands. . After all , why should we take a vein from a far way from legs (saphenous veins ) for by-pass surgery when venous channels are simply there beside every branch of a coronary artery !
Let us be quixotic , we shall attempt to congest the myocardium with blood for refractory angina by whatever means ! Mean while let us also remember what happened to TMR (Trans myocardial laser revascularisation ) the biggest technology failure in cardiology in recent times !