Beating heart coronary artery surgery

This is a method for performing coronary surgery which eliminates the cross clamp. In the past, when the clamp was contraindicated by an "egg shell aorta" cold fibrillation and local control of the coronaries was used. Apart from these rare cases the aortic cross clamp has been mandatory for coronary artery surgery. Since the resurrection of beating heart surgery the dangers of the cross clamp have been thrown into relief. These are the result of atheromatous embolism causing infarction of brain, heart, gut, kidney and liver; they are the cause of the low but persistent mortality in all traditional series. They are more likely to occur in the older patients which are an increasing proportion of most practices today. Most beating heart surgery is now done "off pump" which also avoids the emboli generated by the arterial cannula. When the aortic side-biting clamp is eschewed as well, and all aortic manipulation is avoided, the whole range of devastating embolic complications can be banished from coronary artery surgery.

Experienced OPCAB surgeons do over 90% of cases on the beating heart without any pump assist using either left or right heart bypass in particular situations. Many, like myself, have eliminated the use of the cross clamp and are using non aortic, graft inflow methods, for the majority of cases.

There are three key technical elements required in beating heart surgery: coronary stabilisation, manoeuvres to position the heart and techniques to achieve a blood free field.

Coronary stabilisers

These come in all shapes and sizes but all greatly reduce the movement of the target coronary artery so that an accurate anastomosis can be performed. The most recognised of these is the Octopus, which uses suction to grip the epicardium. The suction aspect, in my opinion, is a gimmick; evidenced by the fact that about half the stabilisers in use, rely on pressure alone. Most stabilisers used today are disposable, a situation motivated by corporate profit. Their price is the same as the pump oxygenator, which they replace and bears no relation to actual cost. A number of completely reusable stabilisers are now available and because of their enormous cost benefit, should be more widely used. The Platypus stabiliser www.beating-heart.com , an Australian reusable device has saved that country over two million dollars in the few years since it has been available. If pump assist is necessary the cost is doubled when a disposable stabiliser is used.

Exposure techniques for beating heart surgery.

The principle of exposure is that a stable position is obtained by various methods with the stabiliser adding only a little extra help to maintain the basic exposure.
There are four exposure positions which will be discussed in detail.

Normal heart position. This is suitable for the acute marginal, right main and occasionally posterior descending. For doing the RCA on the inferior wall the stabiliser arm or a retraction suture can be used to hold back the acute margin of the heart.

Right rotation with apex in mid-line. This is the position for the LAD and most Diagonals the heart is rotated to the right with deep pericardial stay sutures or with a pack behind the LV.

Extreme right rotation with apex right of mid-line, preferably in the R chest. For exposure of high marginal arteries. The rotation is best achieved by strong traction on deep stay sutures. Entry to the chest is facilitated by a number of manoeuvres: Incision of pericardium from R diaphragmatic refection to IVC. Opening R pleural cavity. Detachment of fat and muscle from under inferior aspect of R sternum. Asymmetric sternal retractor position to elevate R sternal table. High frequency, low volume, ventilation to reduce R lung volume. Right rotation of operating table. Even after all these tricks a large heart or a small chest may prevent the apex from entering the R chest and the spreader may need to be opened widely get the heart over enough.

Apex displaced anteriorly out of chest. This allows exposure of PDA, Postero-lateral R/Cx and the low Marginal Cx. Trendelenberg table position and inferior angulation of the deep stay sutures is all that is needed to achieve this position. The two commercial suction retractors can be used to elevate the apex skyward but I have never needed the extra help and have found the "apex up" position to be very haemodynamically stable.

Techniques to achieve a bloodless field

Compression of artery. This is done with small clamps or more commonly, with snares. Snares can be sutures or Silastic tapes. There are some experimental and clinical data to suggest that external compression can cause spasm and even fixed stenoses. The presence of a plaque seems to potentiate this complication.

Many surgeons avoid a distal snare for this reason but I have had a symptomatic proximal snare related stenosis even though a "soft" tape was used.

Coronary blockers. These are effective and avoid the crushing effect of compression. They are a fiddle to insert and keep in place unless there is a tight fit which means they have to come in a variety of sizes.

Intra-coronary shunts. This is the ideal method because it not only produces a clear field but also avoids ischaemia. My anaesthetists are adamant that the patient are more stable when shunts are used, The commercial shunts have a number of shortcomings; fixed length, bulky knot, too stiff, and expensive. I use a custom made shunt of variable length and fixed diameter (A larger size is rarely required. ) It is made from the 1.2mm Silastic tube that is used for a commercial tape, with a fine silk "tag suture". Sometimes a snare needs to be added to the shunt but it does not need to completely close the artery. For details check www.beating-heart.com. The other advantage of shunts, which is not allowed to be mentioned, is the inability of the surgeon to stuff up the anastomosis by catching the back wall of the artery.

Blood clearing devices. Gas blowers and misters are very useful providing the flooding is not torrential and they are often used in conjunction with the other techniques mentioned. They are particularly useful when a septal is opposite the arteriotomy. I find a saline wash is satisfactory in most cases.

Beating heart, on pump.

By avoiding the cross clamp this method attempts to duplicate the low incidence of stroke and cognitive dysfunction reported with opcab surgery. There have been no reported series to date probably because, like me, most opcab surgeons only use the technique for highly selected and usually high risk cases. The added cost of a disposable stabiliser would certainly be a disincentive.

I have used right heart assist a few times and while it improved stability and exposure for big hearts it is not useful in the setting of acute ischaemia or when diseased vein grafts need to be transected prior to lysis of adhesions. I, therefore, use standard cardiopulmonary bypass for all the situations where off pump surgery is, in my hands, not indicated. Standard cannulation is used and the temperature kept near normal. Venting is rarely required and the aorta is not cross clamped. The shed blood is retrieved with a cell saver to avoid contaminating the pump with tissue thromboplastins and debris. All the opcab manoeuvres are employed to position and stabilise the heart together with shunting the coronary arteries. If the aorta is severely diseased and is not being used for graft inflow the arterial cannula can be placed anywhere a soft spot is found on the aorta or in a peripheral artery.

 Donald E Ross FRACS