Coronary Artery By-Pass Graft (CABG) or 'cabbage'

The heart requires a blood supply of its own to supply the heart tissues with oxygen and nutrients. This is provided through the coronary arteries. When an artery become constricted or blocked the section of the heart it serves is starved of oxygen. This causes chest pain (angina) or in severe cases a heart attack or myocardial infarction (MI). To correct this the blood supply must be restored. This can be done in several ways. Drugs can be used to dilate (open) the arteries allowing the blood to flow. Another option is to do an Percutaneous Coronary Intervention (PCI) or Angioplasty. In this procedure a catheter is passed into the artery and is fed up into the affected coronary artery. A ball

oon on the tip of the catheter is inflated widening the artery. A stent (a wire mesh tube) is sometimes placed (permanently) in the coronary artery. This holds open the artery and prevents the artery closing again. In more severe cases a Coronary Artery By-Pass Graft (CABG) or 'cabbage' is required.

CABG is an open heart procedure. The aim of bypass surgery is to circumvent (bypass) the affected area by routing blood from the aorta to an area of the artery below the blockage, where the heart is starved of blood. There may be one or more blockages requiring several grafts.

In order to bypass the blockage a length of blood vessel must be taken from the patient. . The most common areas to take a vessel from within the chest area - the internal mammary artery (or internal thoracic artery), leg (saphenous vein) or arm (radial artery). Internal mammary artery has proven very durable (Paris Heart Centre >95% of CABG procedure utilises the internal mammary artery)

Conventional CABG

The heart is reached by opening the centre of the chest - called a median sternotomy. The breastbone is then exposed. The breastbone is then split down the middle (along the axis indicated on the diagram) and a special clamp reveals the heart underneath. A heart lung machine is usually connected which takes over from the heart in pumping blood around the body (ON PUMP). The heart is stopped using several drugs called cardioplegia. The surgeon is now free to start the bypass procedure.

The open heart CABG (ONPUMP) procedure has the advantage of maximising the field of view and access for the surgeon. Use of the cardio pulmonary bypass machine means the surgeon can work on a heart that is still and free of blood. The surgeon will also be able to apply mulitple grafts as required. For the patient as this is quite an invasive procedure.

After the grafts have been applied the chest is closed, the sternum is wired back together and the wound stitched. A long scar will remain along the length of the breastbone..

CABG (OPCAB - Off Pump Coronary Artery Bypass)

MIDCAB Minimally Invasive Direct Coronary Artery Bypass

This procedure is done when the exact position of the affected coronary artery is known and only a single graft is required. The diagram left shows the position of the incision. No bypass machine is used. Intsruments are placed to immobilise the heart allowing the surgeon to operate. The bypass procedure is the same as the normal CABG. However, it is a more challenging procedure as the heart is still beating and there is blood present in the operating field (the heart is still pumping blood). The length of the incision means there is less room for the surgeon to work. However, the need for a large incision and splitting the chest is removed, therefore fewer complications arise and the patient will have a faster recovery time and have a shorter stay in hospital.

The coronary arteries

An impression of how a graft is attached. One end of a harvested blood vessel is joined to the aorta and the other end is attached to the affected coronary artery below the blockage.

Here the surgeon uses a keyhole technique to harvest a blood vessel (saphenous vein) from the leg (in the background a surgeon is working on the patients chest) Alternatively an incision will be made along the length of the leg to expose a suitable blood vessel for harvesting. This does however create a long scar.

The heart lung machine. The surgeon inserts a cannula (a small flexible tube inserted into a body cavity for draining off fluid or introducing medication) into the aorta and the right atrium. The blood is taken from the right atrium into the machine where it is oxygenated, warmed, filtered then returned to the body via the aorta. The Heart Bypass Machine

The bypass machine

• Allows full access to heart - visually & surgically.
  
• Bloodless operating field
  
• Easier to work on still heart.
  
• Multiple grafts are possible + valves.
  

• Allows full access to heart - visually & surgically.
  
• Avoids complications from using bypass such as organ damage
  
• Quicker recovery, therefore shorter stay
  
• Available to patients who wouldn't tolerate procedure using bypass machine.
  

• Less invasive - scar is smaller, breastbone left intact.
  
• Avoids complications from using bypass such as organ damage.
  
• Quicker recovery, therefore shorter stay
  
  

• Risks using bypass machine.
  
• Large incision/broken breastbone/leg incision.
  
• Large scar

• Beating heart surgery - more challenging.
  
• Large incision/broken breastbone/leg incision.
  
• Large scar

• Beating heart surgery - more challenging.
  
• Restricted view and surgical mobility.
  
• Fewer grafts are possible

Premedication : the administration of drugs prior to the anaesthetic such as ACE inhibitors, Aspirin & Clopidogrel, Beta-blockers,Diuretics and other cardiac medication and oxygen.

The theatre day starts at 8.30am. The anaesthetist gathers together all the required drugs. The patient is checked in and moved to the anaesthetic room and set up for monitoring. The patient is then connected to various catheters and drips required for administering medicines and monitoring of heart output. An epidural (anaesthetic injected into epidural space of the spinal cord) is given. The patient is put to sleep and monitored by the anaesthetist who is aiming to stablise the patient and achieve an acceptable heart rate. The patient is then intubated - a tube is fed down the throat of the patient to keep the airway open.

Other equipment required for the procedure is readied such as: TOE - Transesophageal Echocardiography machine - allows the heart to be monitored by providing moving images of the heart via an endoscopy echo probe which is inserted down the gullet (the oesophagus).Other devices include a bair hugger - device to warm the patient, diathermy pad, warming mattress fluid warmer and blood brain barrier.... an so on.

In theatre : The patients legs and chest are swabbed with antiseptic solution e.g. Betadine - this gives the skin its yellow appearence. Drapes are placed over the patient leaving only the chest area/leg exposed. The patient is placed on a ventilator and continuously monitored using the following parameters : ECG, blood pressure, blood gases, temperature and coagulation.

The procedure begins with an incision to the chest. The surgeon then has to cut downwards through a layer of fat (1-2cm thick) and then through the muscle to the sternal bone. The strenum or breastbone is split down the middle. An electric saw is used for this (figure 1).

A retractor (figure 2) is inserted to keep the incision and ribs open allowing the surgeon to work. The pericardium is opened exposing the heart.

Next the heart has to be prepared for connection to the bypass machine. Before this can be done a dose of heparin is delivered to stop the blood clotting whilst in the bypass machine.

A cannula is inserted into the atrium (figure 5) and a second cannula is inserted into the aorta (figure 4).

Tubes are then inserted into the heart which are used to deliver the cardioplegia drugs which are used to temporarily stop the heart.

All the lines are then connected up and the bypass is ready. The surgeon will instruct perfusionist to enable bypass. The patient is carefully monitored at this point whilst anaethesia and equipment is checked and the ventilator is turned off

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Heart-Lung Bypass Machine

When the surgery team is happy that the patient's circulation is being supported by the bypass machine, it is time to stop the heart. This is initiated by the surgeon "cross clamping" the aorta which separates the heart from the circulation. The cardioplegia solution is delivered into the coronary arteries and veins via catheters as shown in picture - figure 6. The infusion of carioplegia stops the heart.

The surgeon can now start the coronary bypass procedure by first finding the affected coronary arteries. Once located the coronary artery is opened below the blockage. One end of a harvested blood vessel is stitched onto the opened coronary artery. This is repeated for any other affected arteries. The loose ends of the harvested blood vessels are then joined to the aorta.

The bypasses are now finished. It is now time to restart the heart. First, since the arteries have been opened it is crucial to remove any air inside the heart. The "cross clamp" is taken off restoring the circulation. The heart should start to beat without any intervention. However if there are any problems at this point such as arrhythmia then a temporary pacemaker may be fitted or an electric shock may be applied using a defibrillator.

Once the heart is started and is stable the patient needs to be removed from the bypass machine. This is done by turning off the bypass machine incrementally, allowing the heart and lungs to take over the circulation and breathing whilst still being supported by the machine. Temperatues, blood gases, ventilation, anaesthesia and heart function are very closely monitored.

All being well the venous cannula and aortic cannula are ready to come out. A dose of Protomine is given - this counteracts the effects of the heparin drug given earlier before the bypass machine was used. The cannulae are taken out. The blood is monitored for correct clotting function and fluid balances are checked.

The surgeon is now ready to close the chest. Chest drains are inserted and the sternum is closed using steel wire. The tissue layers are stitched together and the skin is closed using stitches or staples.

Post Operation Day 0

The patient is ready to transfer to the cardiac surgery unit for post operative care. Here the patient is continuously monitored for problems with blood pressure, ventilation, post operative bleeding, cardiac output and arrythmias.

CSU actions for receiving patient :

• Monitoring equipment available for collection
  
• Bed area checked
  
• Equipment documentation completed
  
• Ventilator set up, alarms set and circuit labelled,
  
• Bair Hugger is available.
  
• Emergency equipment checked and working

When patient arrives

• Patient handover received from theatre staff – check identity band is insitu
  
• Thoracic suction applied to chest drains
  
• Warm patient on arrival from theatre if temperature is <35oc with Bair Hugger
• Ensure anaesthetic staff have completed management form including prescribing post operative drugs and fluid
• CSU Fluid output chart started with readings taken at 15 minute intervals

The patients relatives will be contacted at this point to let them know that the patient is back in intensive care.

Monitoring :

• Obtain initial blood gases, Full Blood Count and clotting.
• Ensure drug/fluid infusions are given according to prescription, labelled correctly and are infusing at correct rate
  
• Commence epidural monitoring if patient has a thoracic epidural - every hour.
• Central lines are secure- Central Line, Arterial Line,· Swan Ganz Catheter, Peripheral Cannula’s
  
• Wound Condition condition is checked.
• If all observations are acceptable a full clinical assessment is done about 1-2 hrs post-op. This is repeated twice over the next 24hrs. The assessment assesses airway,breathing, blood gases, fluids ,drugs,circulation, bleeding, sedation, pain levels, patient awareness, patient pychological state, wound condition and oral hygiene. An assessment is also made of the manual handling of the patient.

Patients usually stay here for 24hrs. If patient is fit enough he or she is transferred to the cardiac surgery high dependency unit.

CSHDU Post op Day 1/2

On the first day after procedure the patient is transferred to the Cardiac Surgery High Dependency Unit. Activity during the stay on CSHDU:

• Continuous monitoring of ECG
• Check pacing and if not required remove box
• Wean patient off drugs according to condition of the patient.
• Remove catheters and lines.
• Perform 12 lead ECG.
• Remove chest drains.
• Chest X ray performed
• Assessment of blood gases
• Physiotherapist visits patient who assesses the chest - whether it is expanding correctly, enourages deep breathing, enourages coughing and excercising of the upper limbs.
• Pain relief is checked and a review done by the Acute Pain Team.
• Patient is offered breakfast and drink
• Patient may be mobilsed from bed to a chair according to condition of patient.
• Medical review am and pm
• Review wounds and dressings

When the patient is well enough they are discharged from CSHDU and transferred to Ward 3

General Cardiothoracic Ward -Day 2-5 : Ward 3

The aim here is to prepare the patient for discharge. Planning for the patient's discharge has already started. By encouraging physical activity the patient can become independent, better preparing themselves for life out of the hospital. Physiotherapy sessions will be held with the patient. The patients mobility is assessed through several excercises - e.g. walking the length of the ward, moving around the room, upper limb exercises and stair climbing.

• Discharge planning continues - cardiac liaison team will have a discussion with the patient. If required convalenscence care will be organised. Transport will be arranged and the District Nursing team will be informed. The District Nursing team will visit the patient at home and manage the patient's wounds.
  
• Standard observations
  
• Adjustment of drug chart
  
• Removal of temporary pacing wires, if fitted.
  
• Increased patient independence
  
• Planned discharge Day 5
• Medical review - ready for discharge ?

Discharge

A plan is produced through discussion with the patient and the cardiac liaison team. The cardiac liaison team will provide the patient with information containing the following:

• Discharge information
  
• Cholesterol information
  
• Medication information
  
• Warfarin information if required
  
• Dental Letter /Information Given (if appropriate)
  
• Cholesterol result
  
• Appointment made for anticoagulant clinic if required.

If the patient is well enough, observations are acceptable and all the administration is completed, the patient will be allowed home (or discharged back to a district general hospital)

After Discharge

Patient's are usually contacted by liaison nurse at approximately 7 days from discharge. The team  then decide if they need any further calls and that decision is made on an individual basis. There is a telephone helpline available 7 days a week provided by the liaison team.

At about 6 weeks after discharge the patient will have a followup appointment in the outpatients department at MRI - the patient can expect to have a wound check, sternum check, blood pressure/pulse check, a medication review, a mobility review, pain review, breathing check and an echocardiogram (though this depends on the individual consultant). At about this time most patients have returned to their normal levels of activity - but without chest pain. Sometimes there is still some wound discomfort easily controlled with paracetamol. After the clinic visit patients may drive again. Also secondary prevention issues - insuring no return of cardiac symptoms, will be discussed. All being well the patient is usually discharged from our care back to his/her GP.