ANGIOGRAPHIC PROCEDURE

By

Dr/ Dina Metwaly

Digital Subtraction Angiography

DSA: The acquisition of digital fluoroscopic images combined with injection of contrast material and real-time subtraction of pre- and post contrast images to perform angiography.

The image is taken from the image intensification system rather than the film system and allows for instant video replay of a continuously subtracted image (real time).

DSA was extremely helpful when used in conjunction with regular arteriography, as a screening tool, and to improve the quality of manually subtracted films.

It allows for the use of lower doses of contrast and smaller catheters.

Its resolution is not as fine as film, but for most screening purposes it is adequate.

Its other main advantage is that because it subtracts electronically, it is more accurate than manual techniques. The storage of images allows for post-processing manipulation to compensate for movement or poor exposure techniques.

Its most frequent use is in the study of:

1. Carotid stenosis (as a screening tool)

2. As a guide during interventional procedures

3. As a follow-up study after angioplasty or vascular surgery

4. As an adjunct to arteriography, enabling the use of less contrast and smaller catheters (3 French)

DSA Equipment

Digital subtraction angiography requires more complex equipment than digital radiography.

1. Generator and tube: The same nature of the angiographic tube and generator, without further modifications.

2. Image intensifier: The digital image is taken from the television image produced during fluoroscopy. There must also be a high contrast ratio so that small variations in beam attenuation can be registered and used in the subtraction process.

3. TV camera: A camera focuses on the image intensification image and scans it electronically. The amount and quality of light reaching the TV camera are carefully controlled by a light diaphragm.

4. Image storage and processor: This is the section of the computer that takes the acquired images, manipulates the subtraction, and then recreates an analog video image for visualization on a screen.

5. Image digitizer: This turns the analog TV image into a digital image consisting of pixels, the number of which depends on the lines per inch of the TV image. The usual pixel numbers in an image are 512 x 512 or 1024 x 1024 (high resolution)

6. Postprocessing image manipulation: This is performed using the computer and images stored within it and is performed after completion of an examination to create the best image possible.

7. Multiformat camera: A hard copy of the resultant analog image can be produced using this image processor.

Before the Procedure1. After patient is properly identified, the procedure must be

explained before consent can be signed.

2. Before the procedure, the patient is admitted to the hospital for careful observation. This may be as an inpatient or as a day patient, depending on the severity of the patient's condition and the procedure to be done.

3. Vital signs and peripheral pulses should be taken to serve as a baseline for post-angiographic care.

4. Blood tests must be done including BUN, creatnine, PTT, INR, insulin/sugar levels

5. Anticoagulant therapy should be assessed and careful note made of prothrombin time to ensure that it is within normal limits. Administration of these drugs should be withheld for 4 hours before the procedure and resumed after 24 hours postprocedure.

6. Patient should fast for 4 to 8 hours before the procedure. Fluid intake is recommended for patients with renal disease.

Patient Preparation

After patient is put on table, the area being puncture must be free from hair

The technologist working with the cardiologist must be scrubbed in following basic sterile surgical technique

The patient is then draped from neck down with sterile drapes All equipment (radiation shields, image intensifier, equipment used

to manipulate machine) must be prepped with sterile covers

Sterile equipment needed

Procedure tray should include:

1. sterile gowns and gloves for scrub tech and doctor

2. sterile towels and drapes for procedure,equipment covers

3. Gauze, scalpel, needles, scissors, hemostats

4. syringes for heparin/saline flush, lidocaine, and blood draw

5. labels with marking pen for any item filled with a solution

6. basin for heparin/saline mixture, basin for waste fluids, small cup for lidocaine, skin prep solution ,high power manifold-connection tubing

Catheters, wires and sheaths

Medications Used

Once the consent form has been signed any premedication prescribed can be administered. The usual medications include:

1. Valium (diazepam)-muscle relaxant and sedative

2. Atropine-to inhibit a vasovagal reaction

3. Two 500mL bags of saline infused with 2,000 units (2cc) heparin each for flushing all tubing, catheters, sheaths

4. Lidocaine (local anesthesia) for tissue numbing

5. Visipaque contrast unless otherwise specified

When doctor and tech are scrubbed and all equipment and supplies are ready, the procedure may begin

Start Procedure

Arterial Puncture

Access is easiest from right side of patient . Puncture is generally done via the femoral artery Alternative sites include the radial and brachial arteries

of the arm

After puncture of femoral, radial or brachial artery (primarily on right side of patient), a catheter is advanced into the aorta and then the coronary arteries

Catheter introduction

Steps to Insert Catheter

1. After numbing the groin area, the femoral artery is palpated and a needle is inserted in that direction

2. When blood comes out of needle, the artery has been accessed

3. A small, flexible guidewire is then inserted into the lumen of the needle

4. The needle can then be removed but the wire must maintain position

5. After removing the needle, a flexible plastic tube can be placed over the wire and introduced into the artery. This is called a one-way sheath (allows insertion of catheters and wires without blood escaping)

6. The catheter is then inserted over the guidewire but through the sheet and advanced into placement via the inferior vena cava to the aorta

Catheter Placement

Movement of catheter is monitored under fluoroscopy (x-ray movies) with the cardiologist manipulating its movements

The fluoroscopic machine is manipulated by a qualified, scrubbed in, radiologic technologist

When catheter is in place, wire can be removed and contrast administered

Fluoroscopic Views

Catheter in place to view left coronary arteries

Catheter in place to view right coronary arteries

Fluoroscopic Views

Pigtail catheter in left ventricle to measure ventricular pressure

Aortagram used to assess ascending and descending aorta

Fluoroscopic Views

Right coronaary arteries shown with contrast

Left coronary arteries shown with contrast

Complications

Complications in Angiographic Procedures are due to: Contrast Media Intra-arterial complications are rarer than with an IV injection of

contrast. Some specific reactions can occur. Hotness and pain at injection site are reduced by the low-osmolarity

contrast agents. A chemotoxic affect can occur. Sodium or meglumine salts can

affect the ECG. Sodium can produce neurotoxic effects. Acute renal failure is extremely rare but can occur if there has been

significant dehydration, the recent administration of nephrotoxic drugs, and high doses of contrast medium.

Due to procedure

1. Hematoma, Hemorrhage & Arterial thrombus, due to trauma to the artery wall; this can happen for several reasons:

Large catheters , Frequent catheter changes Prolonged time in the arteries, Rough handling and maneuvering

of the catheters Rough-surfaced catheters, specifically polyurethane Treatment: Heparinization of the saline, heparin-bonded catheters,

and guidewires and repeated wiping of these during use, by gauze soaked in heparinized saline

2. Infection at puncture site caused by nonsterile technique

3. Other rare complications can include: Arteriovenous fistula formation Embolus production, atherosclerotic or air Artery dissection Catheter knotting and impaction Guidewire breakage

Finished Procedure

The procedure is complete when the cardiologist has seen all the views and anatomy desired and all pressures recorded

The catheter can be removed and manual pressure must be applied to entry site for 15 minutes

Post Procedure Instructions

1. The patient must lie flat and supine for a minimum of two hours to ensure the artery does not reopen

2. Vital signs taken, including peripheral pulses

3. After two hours, the patient can be released to person driving the patient home

4. Dressing must remain dry, no lifting over five pounds for three days

5. Bed rest for 4 to 12 hours depending on the procedure

6. No shower for 24 hours, No bathing or swimming for one to two weeks

7. If severe pain, swelling or discoloration of limb occurs, doctor must be notified immediately

8. Hydration encouraged

9. Resumption of any drug therapy when assessed to be safe