Surgery to correct pulmonic stenosis using an open pulmonary arteriotomy approach requires inflow venous occlusion. The thorax is entered through the left 4th intercostal space. The caudal vena cava and cranial vena cava are encircled with umbilical tape tourniquet snares. Then the pericardium is opened and a partially occluding clamp is applied to the main pulmonary artery before incising it.

ps6-n	ps6a-n Approximate location of the incision in dogs wth pulmonic stenosis that are undergoing surgical correction.
ps6b-n Caudal vena cava, highlighted in yellow.	ps6c-n Cranial vena cava, highlighted in yellow
ps6d-n Main pulmonary artery, highlighted in blue.

Once the tourniquets are in place around the venae cavae, stay sutures are placed in the pulmonary artery followed by a partially occluding, double-angled vascular clamp (Satinsky-like). The clamp isolates a segment of the pulmonary artery through which an incision can be made prior to stopping circulation. Restraining sutures control the cut edges of the incision over the clamp.

ps7-n	ps7a-n The arteriotomy incision over the clamped portion of the pulmonary artery, highlighted in blue.
ps7b-n Stay sutures, placed into the edges of the arteriotomy, highlighted in red.

The next step in the open pulmonary arteriotomy approach is inflow venous occlusion. The preplaced tourniquets on the venae cavae are tightened and clamped and the elapsed time is recorded. After 3 heartbeats the clamp is opened and blood is aspirated from the pulmonary artery. The obstruction is identified and relieved. This approach allows direct visualization of the valve and provides 2 1/2 minutes to correct the obstruction before the clamp is reapplied and the tourniquets released. 2 1/2 minutes is usually sufficient to relieve a valvular stenosis. If more time is required, the opening procedure can be repeated after 5 minutes of adequate circulation.

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ps8a-n Inflow occlusion of the cranial and caudal vena cavae, highlighted in purple. Umbilical tape is used as a tourniquet, passing through a semi-rigid tourniquet tube and clamped distant from the veins.

The surgery is begun with the anesthetized dog in right lateral recumbency. The incision is made in the 4th intercostal space from the caudal angle of the scapula to the costochondral junction. Bleeders are isolated, clamped, and ligated. The thoracotomy follows normal procedure.

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The ribs are spread with a rib retractor, being careful to avoid damaging the lung.

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The caudal vena cava is isolated by blunt dissection through the mediastinal pleura just caudal to the pericardium. A curved ligature carrier is passed under the vena cava and used to withdraw umbilical tape around the vessel. The plastic tube shown is placed over the umbilical tape to be used as a tourniquet to occlude the vena cava and prevent venous return when the pulmonary artery is opened.

To expose the heart the lungs are retracted caudally and held in place with a moist gauze sponge. Post-stenotic dilation of the main pulmonary artery is visible through the pericardium.

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ps12a-n Post-stenotic dilation of the pulmonary artery, highlighted in purple.

The cranial vena cava is dissected by making an incision in the mediastinal pleura just cranial to the pericardium. The phrenic nerve is encircled with umbilical tape and retracted to prevent trauma. When the cranial vena cava is exposed it is encircled with umbilical tape and a tourniquet tube placed in the same manner as that on the caudal vena cava.

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ps13b-n The phrenic nerve, highlighted in yellow, is retracted with umbilical tape.

An incision is made in the pericardium over the lateral aspect of the main pulmonary artery. Note the post-stenotic dilation of the main pulmonary artery. A small stay suture is placed in the lower lateral aspect of the main pulmonary artery. This suture will subsequently be used to close the pulmonary artery. Another stay suture is placed in the upper lateral aspect of the main pulmonary artery.

ps14-n	ps14a-n Pulmonary artery, highlighted in purple, is accessed through a pericardiotomy.
ps14b-n Proximal end of the main pulmonary artery, highlighted with a yellow cross.	ps14c-n Distal end of the main pulmonary artery, highlighted with a yellow cross.

By placing slight tension on the stay sutures, the wall of the pulmonary artery is stabilized and a partially occluding vascular clamp is applied to the artery.

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An incision is made in the pulmonary artery above the clamp with a sharp scalpel and extended with blunt-tipped scissors in both directions as far as the stay sutures.

A restraining stitch is placed in the lateral aspect of the cut edge of the pulmonary artery. This is sutured over the edge of the clamp to the side of the artery and is used to stabilize the edge of the incision. This process is repeated on the other side of the incision.

When preparations are complete, the tourniquets are applied to the venae cavae. After the heart is allowed a few beats to reduce intracardiac blood volume, the vascular clamp is opened and remaining blood in the pulmonary artery is removed by suction. The heart is essentially empty but continues to beat during the period of inflow occlusion.

In normal dogs there are three thin semilunar cusps making up the pulmonic valve. You can see the valve opening and closing as this post mortem specimen is squeezed.

In this case, as shown in this post mortem specimen, the valve was bicuspid and thickened, with a fish-mouth appearance, instead of having three thin cusps. The stenosis was reduced by incising the commissures to increase the diameter of the orifice, but the valve was left bicuspid. Jet lesions (J) in the pulmonary artery are caused by the high velocity poststenotic turbulence in pulmonic stenosis.

ps20-n	ps20a-n View through the pulmonary artery at a domed pulmonary valve (commissural fusion), highlighted in yellow. Jet lesions (J) can be seen in the wall of the opened pulmonary artery.
ps20b-n Illustration of how the valve was opened (yellow lines) to form a bicuspid valve with a larger orifice.

To close the pulmonary artery, it is allowed to refill with blood to exclude air and then the partially occluding clamp is reapplied with gentle traction on the stay sutures.

After 2 1/2 minutes of circulatory arrest the arteriotomy is reclamped and the tourniquets on the vena cava are loosened, allowing venous return.  The heart is allowed to stabilize and resume normal pressure. If more time is needed to repair the valve, allow 5 minutes of adequate circulation, then re-establish inflow occlusion and open the clamp for an additional 2 1/2 minutes each time. When everything is stable the tourniquets are completely loosened and closure of the arteriotomy is begun.

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The pulmonary artery is closed by a continuous suture pattern starting from the ventral stay suture at 1 to 1.5 mm intervals and is tied independently of the second line. The second line of sutures begins at the dorsal stay suture and goes at 1 to 1.5 mm intervals back to the beginning of the suture line. After suturing, the vascular clamp is removed to check hemostasis. Some leakage through the needle holes may occur but it will stop in 2 - 3 minutes with applied finger pressure. The tourniquets are completely removed when hemostasis is confirmed.

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ps23a-n Suture line, highlighted in yellow, showing the arteriotomy incision after closure.

The pericardium is closed with interrupted sutures at 1 cm intervals so it is not watertight. This prevents the accumuation of blood inside the pericardium.

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ps24a-n Closure of the pericardium, highlighted in yellow.

The lungs are repositioned and inflated to eliminate areas of atelectasis.

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In large dogs it is useful to use a rib approximator to hold the ribs together as the tension sutures are tied. Prior to this a chest tube is inserted into the pleural cavity through a small incision in the 6th intercostal space. Multiple holes are put in the end of the tube to prevent blockage. An untied mattress suture is placed around the tube to close the incision when the tube is removed.

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The incision is closed in normal fashion. Once an airtight seal has been established a large syringe is used to aspirate air from the chest tubes. The tubes are aspirated every 15 minutes until less than 1cc of air or fluid per 10 lbs of body weight per hour is obtained; at this point the tubes are removed and the incisions closed with the mattress sutures already in place.

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Post operative care includes a 5 day course of antibiotics and exercise restriction. The dog should take walks only for 1 month. If congestive heart failure was present prior to surgery then medical therapy is continued until the post operative examination at 2 months.

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