The heart

Interventional procedures

 

Percutaneous transluminal coronary angioplasty (PTCA)

Stenosis and occlusion of the coronary arteries results in reduced pressure peripheral to the lesion, and reduced myocardial blood flow with poor oxygenation of the jeopardized region of the myocardium. As a consequence of this, angina pectoris develops. Treatment may be either surgical, by aortocoronary bypass, usually autologous veins from the ascending aorta to the affected coronary artery peripheral to the stenosis or occlusion, or by dilatation of the arterial stenosis or occlusion.
During the last 10-15 years, modem interventional radiology has developed alternatives to surgical treatment. Transluminal angioplasty of the coronary arteries was first carried out by Andreas Gruntzig in 1977. The method consists of introducing a narrow catheter, on which a balloon is mounted, into the area in the coronary artery where there is stenosis (or occlusion). The catheter is then placed in the centre of the narrow area, and the balloon inflated to a diameter corresponding to the original diameter of the artery. The atheromatous (or calcified) masses forming the stenosis are thus pressed flat, and the artery regains a larger diameter, resulting in a return to normal of the peripheral circulation (Fig. 30 a-c). The first years after it was introduced the method was used only in patients with simple, short stenosis, centrally placed in the coronary arteries. Now, since the development of modem balloon catheters, a considerably larger number of patients can be treated, even when the lesions are in several coronary arteries, and are relatively peripheral. Re-stenosis

a	Figure 30. a) Selective arteriography left coronary artery. Subtotal stenosis (arrow) of the artery supplying the anterior wall of the heart (LAD). b) Balloon catheter inserted into the left coronary artery to dilate the subtotal stenosis. Outline of balloon marked by arrows. c) Angiography to check result of dilatation - the calibre of the artery has returned to normal.
b
c

occurs in about 30 to 50% of the cases, but if this occurs, repeat dilatation of the same vessel can be carried out. Acute complications of the procedure, such as occlusion and development of infarcts, may take place. Sudden death has also occurred, but is today rare.

In the USA as well as in Europe, it is now as common to employ coronary angioplasty as it is to perform an aortocoronary bypass.

Fibrinolysis

Acute infarction may be caused by thrombi in the coronary arteries. When acute occlusion caused by thrombi occurs, treatment with fibrinolytic agents to dissolve the thrombus, thus re-establishing circulation in the coronary artery, may be indicated. Both systemic and local intra-arterial treatment have been used. Systemically, heparin and large doses of streptokinase and tissue plasminogen activator (TP A) have been given intravenously to induce lysis of the thrombus. Local intra-arterial use of streptokinase (or urokinase) is a possible treatment, especially when the condition has lasted for less than four hours. Local intra-arterial infusion with fibrinolytic agents often lasts for several hours. Angiography is carried out during this period to follow the effect on the thrombus and possible retraction or dissolution of the thrombus. As complications such as bleeding are not unusual with this type of treatment, these patients must be carefully monitored.

Valvuloplasty

It has now become possible to dilate stenotic cardiac valves using large diameter balloon catheters. This was performed initially in pediatric cardioradiology, where much experience has been accumulated with dilatation of pulmonary stenosis. For mitral valvuloplasty, the balloon catheter is introduced percutaneously via the femoral vein up to the right atrium. With the aid of a long, curved needle, the atrial septum is punctured and the balloon catheter is passed into the left atrium, and advanced caudally towards the left ventricle, so that the balloon is positioned in the mitral orifice. When the balloon is inflated, any adhesions between the cusps will be broken, and the excursion of the leaflets improved. This is a safe type of treatment with a relatively low incidence of complications.

An attempt has also been made to use a method employing a similar balloon catheter in aortic stenosis. The catheter is introduced retrogradely from the femoral artery to the aortic orifice, which is dilated. Aortic valve dilatation is now almost abandoned because of a very high recurrence rate.

Pericardial drainage

When large amounts of fluid collect in the pericardium, especially when the amount of fluid is so great that there is danger of cardiac tamponade, drainage is indicated. It is easiest to carry out pericardial drainage under the guidance of ultrasound, employing a puncture below the ensiform process. It is usually preferable to puncture the fluid-filled pericardial space in the area near the right atrium. In experienced hands, this is a safe method of treatment without appreciable complications. As the fluid usually sinks down so that the belt of fluid is widest posteriorly, it is best to use a relatively long catheter, which can be positioned with the tip at the back of the pericardial space. When the fluid is hemorrhagic, and large in volume, there may be doubt whether one of the chambers or

Figure 31. After drainage of pericardial exudate under the guidance of ultrasound. Some air has entered the pericardial space, which is seen as a double outline on the left side (black arrows).

appendages of the heart has been punctured instead of the pericardial space. In these cases, the hemoglobin content of the fluid will, however, rapidly differentiate between pericardial fluid and venous blood. If the myocardium should be punctured accidentally, so that the tip of the catheter enters the right atrium, complications such as bleeding into the pericardial space usually do not occur because the pressure in the right atrium is low. In some cases, where pericardial fluid is formed rapidly, permanent drainage may be indicated and the catheter can be left in the pericardial space. However, it is usually preferable to remove the catheter once drainage is completed (Fig. 31).

 

Arnulf Skjennald and Charles B. Higgins