Surgical Approach and Heart Preparation
The surgery is performed under endotracheal anesthesia. Left anterolateral or lateral thoracotomy through the fourth intercostal space is most commonly used.
After opening the chest, the surgeon must expose the heart. This is done via pericardiotomy: the pericardium is incised strictly posterior to the phrenic nerve (n. phrenicus). The incision extends from the initial segment of the pulmonary trunk down to the apex of the left ventricle.
The next critical step is preparation of the left atrial appendage, through which access to the valve will be established:
- A Satinsky clamp is applied to the base of the appendage.
- Just above the clamp, the wall is plicated with a purse-string suture.
- The ends of the suture are passed through a Rumel tourniquet for secure fixation.
- The apex of the appendage is carefully amputated with scissors.
- Four stay sutures are placed on the edges of the resulting incision to control the lumen.
- The cavity is irrigated with normal saline solution containing heparin to prevent thrombosis.
Digital method (main stage)
Closed digital commissurotomy is the classical variant of the procedure. The surgeon inserts the index finger of the right hand directly into the left atrial cavity through the prepared appendage. Simultaneously, the assistant removes the Satinsky clamp.
Inside the atrium, the surgeon digitally palpates and assesses the degree of mitral stenosis. Then, blunt dissection of the fused anterior and posterior commissures is performed using the finger.
Once the orifice is successfully dilated, the finger is withdrawn. The assistant instantly tightens the purse-string suture using the tourniquet and ties it at the base of the appendage. Excess appendage tissue is resected, and the stump is additionally reinforced with interrupted sutures.
Instrumental commissurotomy
In situations where the density of adhesions prevents digital separation of the commissures, the instrumental technique is used.
Preparation for instrument insertion: The finger is withdrawn from the atrium, and a Satinsky clamp is reapplied to the base of the appendage. The heart is slightly luxated into the wound by placing a gauze sponge under the apex. A deep U-stitch (mattress suture) is placed in the avascular area of the left ventricle. The ventricular wall is punctured with a scalpel directly between the stitches of this suture. The surgeon temporarily covers the resulting wound with a finger to prevent bleeding.
Dilation procedure:
- The clamp is removed from the appendage, and the right index finger is re-introduced into the left atrium to serve as the surgeon's "eyes".
- A specialized instrument—the Dubost dilator (or B.V. Petrovsky dilator)—is introduced through the puncture in the left ventricle.
- Under strict control of the finger inside the atrium, the blades of the dilator are opened, mechanically tearing the commissures.
- After reaching the desired diameter, the dilator is removed, and the U-stitch on the ventricular wall is securely tied.
Open commissurotomy and alternative approaches
In addition to the classical left-sided approach, a right-sided lateral approach exists. In this approach, the interatrial septum is dissected between the caval entry zones, the left atrium is opened, and a finger or dilator is introduced through it.
Open mitral commissurotomy is a more extensive procedure used under strict indications:
- Complication of stenosis by left atrial thrombosis.
- Pronounced valve calcification.
- Restenosis following a previous closed operation.
Features of the open method: Access is achieved via right lateral thoracotomy (4th intercostal space) or median sternotomy. The main difference is the mandatory use of cardiopulmonary bypass (CPB). The left atrium is widely opened, allowing visual control of the procedure. First, all detected thrombotic masses are removed. Then, the valve leaflets are separated and the fused commissures are incised with a scalpel down to the fibrous ring.
Briefly: answers to topical questions
In which specific anatomical zone of the left ventricle is the U-stitch placed for dilator insertion?
The U-stitch for dilator insertion is placed in the avascular zone of the left ventricle. This step is performed during instrumental commissurotomy if digital commissural separation fails. Before placing the suture, the heart apex is luxated into the wound with a gauze sponge. The left ventricular wall is punctured with a scalpel between the stitches, and the Dubost dilator is introduced through the wound. Upon completing the manipulations, the instrument is removed, and the U-stitch is securely tied.
Which layers of the chest wall are successively incised during left-sided thoracotomy through the fourth intercostal space?
The source provides the layered structure of the chest wall from superficial to deep:
- skin;
- subcutaneous adipose tissue;
- superficial fascia;
- deep fascia of the chest;
- pectoralis major muscle;
- clavipectoral fascia;
- pectoralis minor muscle;
- intercostal muscles and ribs;
- endothoracic fascia;
- parietal pleura.
What structures form the root of the left lung, near which the left phrenic nerve runs?
The source does not specify the relationship between the left phrenic nerve and the root of the left lung. Composition of the left lung root: pulmonary artery, main bronchus, superior and inferior pulmonary veins, lymphatic vessels, and nerves. From top to bottom: pulmonary artery, main bronchus, pulmonary veins.
What branches are given off by the left coronary artery, injury to which must be avoided during left ventricular manipulations?
The left coronary artery divides into two key branches:
- the anterior interventricular branch, which runs down to the apex of the heart;
- the circumflex branch, which directs toward the lateral and posterior walls of the heart.
How does the right-sided lateral approach to the mitral valve differ from the left-sided approach?
The right-sided and left-sided approaches to the mitral valve differ in the site of entry into the left atrium.
| Characteristic | Left-sided approach | Right-sided lateral approach |
|---|---|---|
| Site of entry | Through the left atrial appendage | Through the interatrial septum |
| Technical features | A purse-string suture is applied to the base of the auricle, the apex is cut off, and a finger is inserted into the left atrial cavity | The interatrial septum is dissected between the entry points of the venae cavae, and the left atrium is opened |
It is easy to remember the types of commissurotomy by the acronym DIO: Digital (first we try with a finger), Instrumental (if that failed — a dilator is inserted through the ventricle), Open (for thrombosis and recurrences, with cardiopulmonary bypass).
Class and exam questions
Where is the pericardium incised during the left-sided approach?
The pericardium is incised posterior to the phrenic nerve, from the initial part of the pulmonary trunk to the apex of the left ventricle.
Through which structure is the finger inserted during the closed technique?
The index finger is inserted through the previously prepared left auricle (onto which a purse-string suture and tourniquet have been applied).
What is the purpose of the U-shaped suture on the left ventricle?
It is placed in the avascular zone in order to safely insert the Dubost dilator through a puncture, and after its removal, to quickly and hermetically close the wound.
When is open mitral commissurotomy indicated?
It is indicated for stenoses complicated by thrombosis or calcinosis, as well as for recurrences of stenosis after a previously performed closed procedure.
What else to study on this topic
- Technique of applying purse-string and U-shaped sutures to the heart
- Design and operating principle of the Dubost dilator and Petrovsky dilator
- Topographic anatomy of the phrenic nerve and pericardium
- Operating principle of the cardiopulmonary bypass machine (CPB)
- Topography of the interatrial septum and the orifices of the venae cavae
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