E-Science Station

The number of coronary angiograms is increasing year by year. Every year active interventional cardiologists in reference centers review more than a hundred angiograms made in other clinics.
We reviewed the angiogram of the 65 years old male patient. We have found a strange picture. On the series of angiograms of chronical total occlusion (CTO) of the right coronary artery (RCA), we have found several puddle-like reservoirs of contrast at terminal segments of atrial branches of RCA. The diameter of reservoirs was about 0,2 - 0,3 mm (fig. 1) and the surface area on the pictures was 4-12mm. The first series of angiograms did not show this phenomenon. These contrast "puddles" appeared after the second contrast injection. The puddles had clear geographic contours and were moving with heart structures. The contours have not been washed out. Their shape stayed constant for 10 and more cardiac cycles.
We assumed that this lacunar contrast puddle-like depo was the result of hydrodynamic trauma. In theory, the mechanism of damage looks like during the catheterization CTO all volume of the contrast has been delivered on the short stump. The stump diameter was 3.5 mm and the length was 3 cm. The amount of injected contrast  was as usual for a non-occluded artery and reached 5-10 ml. The possibility that the catheter is wedged in the atrial branch of right coronary artery ostium cannot be excluded. The direct super-selective contrast injection can presumably lead to volume overload and rupture of terminal segments of the artery, where elastic resistance of the vessel wall is minimal and adjacent tissues because of the thin myocardium layer does not protect.
The aim of this study was to develop the porcine model of direct super-selective contrast injection and check the possibility of terminal segments atrial RCA branches rupture due to volume overload.   

We used the porcine heart. It was less than 2 hours after animal death. Coronary arteries of this heart were catheterized with standard cannulas used in cardiac surgeries for antegrade selective cardioplegia with inflation balloon diameter 4 mm (CalMed Labs, polyvinylchloride and silicone). We filled the artery with excessive contrast volume using angiography syringe 10.0ml. The contrast was Omnipak 350 mg/ml. The injection was under fluoroscopy and cine 30 frames per second. Overload of main vessels did not result in similar puddles (fig 2) possible because of the intramural passing of the vessels deep in the ventricle muscles. It was impossible to get the tight filling of the atrial branches of RCA at this level of catheterization with cannulas. It was because of the ostium placement. They were proximal or at the level of cannula's sealing balloon. We separated and dissected the proximal RCA to achieve super-selective cannulation of the atrial branches (fig 3). Ostiums of the atrial branches were ad-oculus cannulated with venous catheters Vasofix18G B-Braun without using a needle. Then contrast overload was performed once again and we have achieved puddle-like intramural extravasation in terminal segments of atrial branches (fig 4). We did not see any extravasation and seen ruptures on the surface of the heart. These puddle-like extravasations were found in the subendocardial layer.

The results show that direct super-selective contrast injection can lead atrial RCA branches in terminal segments rupture due to pressure and volume overload (fig 4). Also, there is ahigh possibility of the traumatic cause of these puddle-like contrast spots in the case with the patient with chronically occluded RCA. The anatomical determinant for this rupture is the absence of hard muscle layer around the vessel. This layer should prevent this rupture as it could be in intramural terminal branches in the ventricle.
Coronary angiography is a routine procedure now. But the technique of angiography is different site by site. Colleagues sometimes are not aware of how deep and how co-axial is the catheter. The intensity, volume, and speed of injection cannot be made equally without special injection devices. Also, the lengths of cine are different indifferent clinics. Sometimes all phases of contrast passage are not registered. One of the mistakes is not changing the volume or speed of injection. The performing doctor should be aware of the basic anatomic and pathophysiologic peculiarities of the patient to make angiography safe and informative.

The model shows the dangers of underestimation technical aspects of angiography. First, get the optimal placement of a catheter tip. The position is important to get the tight filling of the artery and to prevent artery damage. Second, avoid excessive intensive injection of contrast. The contrast injection should be as delicate as necessary to get a good picture. Third, our research found that these puddle-like contrast lakes on angiogram are the result of the hydrodynamic trauma. The clinical consequences of this damage possible can be the fibrosis or arrhythmogenic nodes, but due to limited cases, it is a hard subject of future research.