Angioplasty

Shawn N. Sarin, Eberhard Zeitler *, Reinhard Loose, Prasanna Vasudevan and Anthony C. Venbrux

Percutaneous transluminal angioplasty (PTA) is based on the diagnostic percutaneous catheter techniques introduced by Sven Seldinger in 1953. PTA was first introduced by Charles Dotter and Melvin Judkins in Portland, Oregon, in 1964 as a method to treat arteriosclerotic occlusion in arteries.

The year 1974 marked the beginning of a new era of PTA, with introduction of the double-lumen balloon catheter by Andreas Gruentzig. Remarkable technical and clinical results were achieved. Because of the smaller outer diameter of the balloon catheter in the deflated state, local complications at the puncture site could be reduced, and the dilation force on stenotic lesions in the vessel could be adapted to the diameter of each artery by using different balloon diameters. Balloons were inflated to maximal force with solutions of contrast material. Such inflation enabled the operator to achieve excellent control during fluoroscopy.

Since its introduction, PTA (with and without stenting) has become standard practice in all arteries of the extremities, as well as in other areas of the body, including the coronary 1,2 and carotid³ circulations. The increasing success of angioplasty of the coronary arteries led to general clinical acceptance of angioplasty as an alternative to open surgery. Subsequent technical developments and the introduction of additional antiplatelet aggregation drugs helped improve clinical results.

Stenting

Intravascular stents are mechanical devices used to solve problems arising during or after recanalization and balloon angioplasty. Stents are inserted for the management of intimal dissection or elastic recoil and have been found to improve long-term patency.

Stents can also be used as a primary technique for vascular recanalization. They are used in highly stenotic arteries, followed by PTA to optimize vessel diameter and the inner surface of the arteriosclerotic artery and to reduce intimal hyperplasia.

There are basically two types of stent configurations: balloon-expandable (BX) and self-expandable (SX) stents. They are constructed of different materials and have different designs (Table 25-1). To reduce the problem of in-stent restenosis, drug-eluting stents and bioabsorbable stents are now being evaluated in clinical trials. At present, PTA without stents is less costly than PTA with stents, so stent use requires specific clinical indications derived from results of randomized trials. Use of drug-eluting stents is safe for acute complications, but for elective applications, results from randomized prospective trials are necessary.

Clinical Relevance

Global Prevalence of Peripheral Occlusive Vascular Disease

The incidence of peripheral occlusive vascular disease (POVD) varies between 2.7% and 4.0%, without regard to differences in age and sex. Between the ages of 70 and 79 years, the prevalence of POVD is 9.8% in men and 7.7% in women. Coronary artery disease (CAD) is 2.5 times more frequent in patients with POVD than in individuals with healthy peripheral arteries. In contrast, POVD develops 2.3 times more often in patients with CAD than in persons without coronary symptoms; a strong correlation exists between CAD and POVD.4,5

The prognosis for POVD if untreated is poor, with about 25% of patients dying within 5 years and 17% requiring leg amputation. Follow-up studies of patients with intermittent claudication (Rutherford classification 2 and 3) show that 50% die within 10 years, 20% do not change, and 20% experience symptom deterioration. Clinically, only 10% improve spontaneously.⁶

In such circumstances, any treatment modality that helps improve the overall clinical situation and prognosis is important. Thus, the basis of therapy is modification of risk factors, including control of hypertension, diabetes mellitus, smoking, hyperlipidemia, and infection. The last 30 years’ experience in angioplasty of the extremities has shown that in addition to conservative management (e.g., exercise, different types of open vascular surgery), image-guided endovascular treatment plays an important role.

Most patients with claudication, pain at rest, and gangrene with Trans-Atlantic Inter-Society Consensus (TASC) type A or B arterial occlusion can be successfully treated with either balloon angioplasty or stent-assisted angioplasty (stenting). The results of endovascular techniques vary depending on the clinical stage (Rutherford grading), extent of arterial occlusion (length and diameter; TASC classification), and experience of the interventionalist.

Results can be optimized with the combination of open surgery and endovascular treatment. The original TASC classification gives recommendations for the management of POVD secondary to atherosclerosis affecting the lower limbs and seeks to aid physicians in selecting a suitable treatment. TASC II (2007),⁷ more recently released, reflects the evolution of the preferred options for treating femoropopliteal lesions.

Angioplasty is generally the preferred minimally invasive technique. In most cases, it requires shorter hospitalization time, no general anesthesia, and less intensive postprocedural monitoring. In 20% of patients, mainly with TASC A and B lesions, angioplasty can be performed on an outpatient basis.

Equipment

Today a wide range of equipment for diagnostic and interventional procedures is commercially available. For optimal function, a dedicated interventional room has to be large and versatile enough to allow different types of sophisticated interventional procedures to be performed. Additional modalities that should be available to the interventionalist include electrocardiography, Doppler ultrasound, or other studies that do not require moving the patient to different examination rooms.

The suite should be equipped much like an operating room: equipment for monitoring, life support, and resuscitation of critically ill patients. Illumination should be bright and shadowless, and operation of room lights should be controllable with an on/off foot switch.

Commonly used diagnostic and interventional materials such as catheters, guidewires, stents, drugs, and contrast material should be stored in the interventional suite for quick access. In situations involving critically ill patients, immediate access to the staff of the intensive care unit, critical care unit, and anesthesia department should be available through a paging system.

Most diagnostic and interventional angiography systems are designed as a “C-arm” or a “U-arm” so the equipment can be moved around the patient easily to acquire multidirectional imaging projections during dynamic fluoroscopic imaging without subtraction or during digital subtraction angiography. If possible, the systems should be designed with the x-ray tube under the table to reduce occupational exposure. If horizontal or oblique projections are necessary, the physician should always stand at the detector side of the patient and not at the tube side. Additional and mandatory options for reduction of patient and occupational exposure include last image hold, a second monitor for reference images, pulsed fluoroscopy, and virtual collimation without radiation.⁸

In 2002, the first dynamic flat-panel detectors were introduced, replacing the image intensifier. These detectors are now available with dimensions up to 40 × 40 cm. When compared with image intensifier systems, they provide higher spatial resolution (up to 3.25 line pairs per millimeter), homogeneous signal intensity over the entire image, no geometric distortion, and a better signal-to-noise ratio with a smaller dose of radiation.⁹ In 2004 the first flat-panel detector computed tomography (CT) systems were introduced for clinical use. With a single rotation for unsubtracted images or two rotations (forward/backward) for subtracted images, up to 2000 thin CT slices can be reconstructed. The time needed for a 240-degree rotation ranges from 5 to 20 seconds, and the dose to the patient does not exceed that of a conventional multislice CT.¹⁰

Technique

Anatomy and Approach

Descriptions of normal arterial anatomy of the abdominal aorta, pelvic arteries, and upper and lower extremities are derived from several standard texts and included elsewhere in this book. Knowledge of vascular variations and sites for percutaneous introduction of catheters into the arterial system is important for performing interventional techniques.11,12

The common femoral artery, which is the continuation of the external iliac artery distal to the inguinal ligament, and the superficial femoral artery (SFA) are most often the sites of percutaneous puncture for access to the arterial system. In specific clinical circumstances and with availability of smaller-diameter catheters, the brachial artery can also be punctured retrograde for catheterization of the aorta and aortic side branches, as well as the lower extremity arteries.

The SFA is a unique vessel in its anatomy, function, and interventional requirements. It is not comparable to any other arterial vascular bed. The SFA is a long vessel with high resistance to flow in varied hemodynamic conditions. In the past, the unique characteristics of the SFA have resulted in suboptimal outcomes for specific endovascular procedures. Although some endovascular techniques used in the SFA have been studied in prospective randomized trials, the results have been disappointing. Five-year long-term patency rates ranging between 50% and 60% have been reported. This is lower than rates reported in other arterial vascular beds.¹³

The interventional procedure starts with local anesthesia and percutaneous puncture of the artery in a retrograde or antegrade direction. For most diagnostic procedures, including cardiac and cerebrovascular angiography, retrograde puncture of the femoral artery below the inguinal ligament is most desirable. The Seldinger technique is used. To reduce local groin complications, use of a catheter introducer sheath is important. Such sheaths are of value in several specific clinical situations, such as introduction of closed-tip catheters; delivery of interventional devices such as balloon catheters, stents, atherectomy devices, intravascular duplex ultrasound catheters, intravascular radiation devices; and for removal of clots, embolic material, or intravascular foreign bodies.

Angioplasty of the iliac arteries, renal arteries, aortic branches, and the aorta itself most often requires the retrograde puncture technique followed by introduction of sheaths of different sizes.

Angioplasty of lower extremity arteries, especially the SFA, can be performed after antegrade puncture of the CFA or retrograde puncture from the contralateral CFA and manipulation of the catheter at the aortic bifurcation (the so-called up-and-over approach). This technique requires special catheters with preshaped tips and a stabilizing guidewire. This combination is generally more rigid to facilitate downstream manipulation of angioplasty catheters, stents, balloons, and other endovascular devices.

Technical Aspects

Angioplasty for treating arterial stenosis or obstruction may be divided into steps:

1. Pretreatment angiography with localization of the arterial obstruction

2. Crossing the lesion with a guidewire or catheter with a flexible tip

3. Advancement of the treating catheter or instrument over the guidewire and confirming patency of runoff arteries

4. Exchange of the diagnostic catheter for the balloon catheter or stent

5. Dilation of the stenosis with the angioplasty balloon, followed by deflation

6. Completion angiography followed by treatment of runoff vessels with different balloon catheters or stents

7. Exchange of catheter materials and occlusion of the arterial puncture site by manual compression or a closure device

8. Placement of a compression bandage above the puncture site, followed by patient monitoring for a minimum of 2 hours

9. Depending on the patient’s clinical situation and condition and the outcome of the angioplasty procedure, monitoring the patient for several more hours

10. After discharge, if there is no contraindication, patients may be treated for 2 more days with medications such as anticoagulant or antiplatelet drugs. Modification of risk factors is also important.

In summary, the pathomorphologic mechanism of angioplasty can be described as a “controlled traumatic injury” that leads to dilation, with a free arterial lumen. This effect can be verified by histologic and angiographic examination and is summarized in Table 25-2.

Angioplasty for Occlusion of the Iliac Artery

Angioplasty with balloon catheters as originally described by Gruentzig is successful in treating single stenoses of the common and external iliac arteries (Figs. 25-1 to 25-3) via a retrograde transfemoral approach. To treat stenoses in the groin region, the CFA of the contralateral side is punctured, and treatment is accomplished as described earlier (i.e., “up and over” the iliac bifurcation).

FIGURE 25-1 Single stenosis in right common iliac artery (TASC type A) before **(A)** and after **(B)** balloon angioplasty.

In patients with stenosis of the infrarenal aorta or occlusion of the iliac arteries on both sides (see Fig. 25-2), bilateral retrograde femoral artery puncture is required. To dilate stenoses close to the aortic bifurcation or in the aorta itself, simultaneous dilation with two balloons (i.e., the kissing balloon technique) or a balloon with a large diameter is necessary. Dilation with three balloons has been reported in the literature (i.e., balloon catheters inserted from the groin puncture sites and one from the brachial artery directed downstream [i.e., caudally]).

In some situations, atherosclerotic changes are so severe that balloon dilation results in rupture of the inner layers, followed by dissection, incomplete dilation, and reduced blood flow. This can be visualized immediately with a completion angiogram. In addition to angiography, this problem can be further evaluated with duplex or intravascular ultrasound guidance. At the time of angioplasty, intraarterial blood pressure readings confirm the presence of a significant gradient (i.e., suboptimal angioplasty). In this circumstance, an optimal outcome can be achieved by stenting the lesion, which results in a patent lumen and good blood flow.

After angioplasty or stenting, a completion angiogram of the treated lesion and runoff vessel is necessary. Ankle and arm pressures should be obtained to calculate the ankle-brachial index (ABI) using a Doppler technique.

Indications for the different types of treatment of POVD in the aortoiliac segment are summarized in the TASC 2007 ⁷ document, which states that treatment of type C lesions can be endovascular or surgical. If endovascular techniques and conventional surgery have comparable short- and long-term results, the technique associated with the least morbidity and mortality is preferred.

Regarding type D lesions, treatment is generally surgical, although endovascular repair may be considered in special clinical and local situations.

Angioplasty of the Superficial Femoral and Popliteal and Tibioperoneal Arteries

In most patients, angioplasty of the superficial femoral, popliteal, and tibioperoneal arteries generally starts with an antegrade puncture in the groin under local anesthesia. A sheath is placed, and a guidewire with a soft, flexible tip for crossing the stenosis is advanced. A more rigid guidewire may be used if necessary to recanalize a total occlusion. The combined diagnostic and therapeutic procedure is monitored with image guidance. In most patients, this is accomplished fluoroscopically, but occasionally ultrasound and magnetic resonance imaging (MRI) may be used. In some patients with complete vascular occlusion, laser technology or a rotating device (Rotablator [Boston Scientific, Natick, Mass.]) can be used.

In patients with claudication, more often single (Figs. 25-4 and 25-5) or multiple stenoses can be crossed safely with the guidewire and catheter. In some patients, the diagnostic catheter is exchanged for the balloon catheter. In others, after carefully advancing the guidewire, the balloon catheter can be introduced directly over the guidewire in situ.