Cerebral revascularization

During the last 10 years, there has been a revival of interest in cerebral revascularization procedures. Not only have significant progressions in surgical techniques been published, the use of more advanced diagnostic methods has led to a widening of the indications for cerebral bypass surgery. The purpose of this review is to outline the current techniques for extracranial-to-intracranial (EC/IC) and intracranial-to-intracranial (IC/IC) bypass surgery, as well as to identify the current indications for revascularization procedures based on the available literature. The excimer laser-assisted non-occlusive anastomosis (ELANA) technique is described in more detail because we think that this technique almost completely eliminates the risk of cerebral ischemia due to the temporary vessel occlusion which is currently used in conventional anastomosis techniques.

Nonocclusive excimer laser-assisted end-to-side anastomosis

BACKGROUND

High-flow extraintracranial bypass operation on the brain is a risky procedure because of the temporary occlusion of the intracranial portion of the internal carotid artery. We therefore developed a nonocclusive anastomosis technique in the experimental animal laboratory in 100 chronic and acute experiments in rabbits.

METHODS

In 40 patients we interposed a venous transplant between the external carotid artery or one of its branches and the intracranial portion of the internal carotid artery. During the construction of the distal anastomosis the recipient artery was not occluded. The donor vessel was stitched to the exterior of the recipient vessel and an Excimer laser catheter (Medolas GmbH, Amberg, Germany) was introduced by way of an artificial side branch. The tip of the laser catheter created a hole in the wall of the recipient artery just inside the anastomosis. The cut-out full-thickness portion of recipient vessel wall remained attached to the tip of the laser catheter by way of high vacuum suction and was removed together with the laser catheter. The artificial side branch was occluded with a hemostatic clip. No interruption of blood flow in the recipient artery was induced during the making of the anastomosis.

RESULTS

The procedure was well tolerated by the patients and a high patency rate was observed.

CONCLUSIONS

The nonocclusive Excimer laser-assisted anastomosis technique is safe and yields a high long-term patency rate in neurosurgical patients. It cannot be excluded that there are indications for this method in coronary bypass surgery.

Hemodynamic changes during displacement of the beating heart by the Utrecht Octopus method

BACKGROUND

Coronary bypass grafting of posterior circumflex branches requires full displacement of the heart (apex pointing ventrally), which, in the beating heart, results in an arterial pressure drop. We analyzed its origin.

METHODS

To facilitate displacement, the Utrecht "Octopus" method was applied in 8 anesthetized beta-blocked pigs and the beating heart was fully retracted.

RESULTS

Displacement decreased stroke volume from 75 +/- 17 mL (mean +/- standard deviation) to 43 +/- 13 mL (p < 0.001), a 44% +/- 3% decrease that resulted in a decrease in cardiac output by 32% +/- 5% (mean +/- standard error of the mean; p < 0.001), a decrease in mean arterial pressure by 26% +/- 5% (p < 0.01), and an increase in heart rate by 26% +/- 6% (p < 0.01). Right ventricular end-diastolic pressure increased from 5 +/- 1 to 8 +/- 1 mm Hg (p < 0.01). Twenty degrees head-down tilt normalized cardiac output and mean arterial pressure. Right ventricular end-diastolic pressure increased to 10 +/- 2 mm Hg (p < 0.001) and left ventricular end-diastolic pressure to 11 +/- 3 mm Hg (p < 0.01).

CONCLUSIONS

Displacement of the beating heart in the pig induced a 44% drop in stroke volume, which is attributed to biventricular interference with pump function. The Trendelenburg maneuver reestablished the control circulatory status at the expense of augmented right and left ventricular preloads and an increased heart rate.

Experimental off-pump grafting of a circumflex branch via sternotomy using a suction device

BACKGROUND

We have shown previously in the pig that coronary artery bypass grafting on the beating heart may be facilitated by local cardiac wall immobilization by a suction device ("Octopus") applied to the anterolateral side of the heart. The purpose of this study was to investigate the feasibility of the method on the posterolateral side.

METHODS

In a consecutive series of 8 pigs, after median sternotomy, the posterior wall was taken hold of by the Octopus and subsequently brought up anteriorly and immobilized while hemodynamics were monitored. A posterolateral branch of the circumflex artery was grafted with the left internal mammary artery. After the coronary artery was ligated proximally, the heart was repositioned. At 6 weeks, bypass graft angiography and functional testing (postocclusion hyperemia testing) were performed. After sacrifice, histologic examination of the anastomosis was performed.

RESULTS

Dislocation of the heart to expose the distal anastomosis site caused a minor drop in mean arterial blood pressure from 71 +/- 14 (baseline) to 63 +/- 6 mm Hg (dislocated) (not significant) and recovery to 70 +/- 12 mm Hg, 15 minutes after repositioning. Cardiac output decreased from 4.0 +/- 1.0 to 3.2 +/- 0.7 L/min (p = 0.02) and recovered to 4.3 +/- 0.3 L/min. No inotropic drugs were necessary. Anastomosing required 21.5 +/- 6.5 minutes. Baseline graft flow was 8 +/- 3 mL/min and increased threefold to 24 +/- 10 mL/min (p < 0.05) at postocclusive hyperemia testing. At sacrifice after 6 weeks (n = 8), graft flow increased fourfold from 5 +/- 2 to 20 +/- 8 mL/min (p = 0.002) (n = 7). At histologic examination all eight anastomoses were patent without stenosis or mural thrombus.

CONCLUSIONS

Off-pump coronary artery bypass grafting of the posterolateral circumflex branches using the Octopus method on the beating pig heart is feasible, with full patency maintained for at least 6 weeks.

Facilitated exposure of the internal mammary artery in minimally invasive direct-vision CABG

A method is described to facilitate harvesting of the mammary artery in minimally invasive direct-vision coronary artery bypass grafting using a 10-cm anterior thoracotomy. Hoisting of the anterior thoracic wall with a modified retractor allows good exposure. Harvesting the mammary artery without the use of endoscopic tools was successful in all 10 cases.

Coronary artery bypass grafting without cardiopulmonary bypass and without interruption of native coronary flow using a novel anastomosis site restraining device ("Octopus")

OBJECTIVE

This study assessed the feasibility of coronary artery bypass grafting on the beating heart without interruption of native coronary blood flow using a novel anastomosis site restraining device.

BACKGROUND

Recently, an end-to-side bypass technique was described that does not require interruption of flow in the recipient artery.

METHODS

By means of a suction device ("Octopus"), in 31 pigs the epicardium was grasped and immobilized through an arm contraption fixed to the operating table. In the first 15 consecutive pigs (study I), the two-dimensional motion of an epicardial beacon was monitored. In 16 subsequent pigs (study II), an internal mammary artery was grafted under the microscope in two steps to a proximal coronary artery segment, without cardiopulmonary bypass. First, the internal mammary artery was sutured end-to-side to the outside of the coronary artery. Secondly, an orifice was punched in the partitioning coronary wall by an excimer laser catheter introduced through a temporary side-branch of the internal mammary artery.

RESULTS

Study II: During 43 suction periods in four anastomosis areas, immobilization was achieved for 15 to 169 min (>30 h in total) in 13 open- and 9 closed-chest procedures without hemodynamic deterioration. The area circumscribed by the edges of the beacon trajectory (area in which the anastomosis is to be tracked) was reduced from 73.0 +/- 43.0 mm(2) (mean +/- SD) to 1.3 +/- 0.5 mm(2) (p<0.001) in the open-chest and to 0.2 +/- 0.2 mm(2) in the closed-chest procedure. At 6 weeks, no myocardial or coronary suction lesions were found. Study II: Nonocclusive anastomosis surgery required 25 +/- 3 min. No leakage, serious arrhythmias, graft closure or hemodynamic deterioration occurred during the procedure or for 2 h after ligating the coronary artery proximally. At 6 weeks, all seven grafts were patent.

CONCLUSIONS

Coronary bypass on the beating heart without interruption of coronary flow is feasible. In both open- and in closed-chest procedures, the "Octopus" reduced anastomosis site motion to about 1 X 1 mm without adverse consequences.