Intravascular Ultrasound: Indications, Procedure, and Complications

Introduction:

Intravascular ultrasound (IVUS) is a diagnostic procedure used to visualize the interior of the blood vessels. Intravascular ultrasound is a combination of echocardiography and cardiac catheterization procedure. This procedure uses sound waves to visualize and detect the function of the coronary arteries. It is also called coronary intravascular ultrasound, endovascular ultrasound, or intravascular echocardiography. IVUS is an effective adjunctive tool for cardiac catheterization in detecting the morphology of the plaque and guiding the percutaneous coronary interventions.

How Does the Intravascular Ultrasound Work?

Intravascular ultrasound is a diagnostic tool that captures images of the blood vessels inside the body using sound waves. During the ultrasound, a handheld probe called the transducer produces high-frequency sound waves which bounce off the blood vessels and are received by the transducer. The transducer processes the reflected waves, which are then converted by the computer into images of the blood vessels.

What Are the Indications of Intravascular Ultrasound?

The indications of intravascular ultrasound are:

• Aortic Aneurysm - Balloon-like enlargement of the aorta.

• Blood Clots - Clumps of blood.

• Carotid Artery Disease - Narrowing or blockage of the carotid artery by plaque deposition.

• Coronary Artery Disease - Blockage or narrowing of the coronary artery.

• Deep Vein Thrombosis - Formation of blood clots in the deep veins.

• Peripheral Artery Disease - Blockage of the blood vessels supplying lower extremities.

• Pulmonary Artery Stenosis - Narrowing of the blood vessel connecting the right ventricle of the heart to the lungs.

How Is the Intravenous Ultrasound Performed?

During an intravenous ultrasound procedure, patients may be asked to lie flat on the procedure table. Then the nurse connects an intravenous (IV) line into the vein of the patient's arm or hand to deliver the sedatives. Intravenous ultrasound requires moderate sedation. Before the procedure, the health provider sterilizes the area where the tube will be inserted. Local anesthesia will be given to numb the procedure site.

Then the doctor will make a small incision at the procedure site and inserts the catheter (flexible tube) into the groin artery or vein. The catheter used in the intravascular ultrasound is a thin tube with an ultrasonic transducer connected to an end. The other end of the tube is connected to the computer. The size of the catheter varies depending on the size of the blood vessel to be imagined. Under ultrasound guidance, the catheter is threaded into the target site through the blood vessels. Once the catheter reaches the procedure site, the transducer in the catheter produces sound waves to provide images of the blood vessels. The final images are displayed on the computer screen at 30 frames per second. When the images of the blood vessels are taken, the doctor will remove the tube and apply pressure or use a closure device to seal the hole in the artery or vein. Finally, the small incision on the skin will be covered with a dressing.

What Are the Post-procedure Instructions for an Intravascular Ultrasound?

Post-procedure instructions include:

• Patients are advised to lie flat for about six hours after the intravascular ultrasound procedure.

• Sometimes patients may be hospitalized after the procedure overnight for observation.

• Patients are instructed to bring someone else to avoid driving home alone after the procedure.

• Avoid aggressive exercises or heavy weight lifting.

What Are the Different Types of Equipment Required in Intravascular Ultrasound?

Intravascular ultrasound uses a catheter with a piezoelectric transducer at one end and a guide wire. The guide wire is usually 0.36 millimeters in diameter and is used to guide the placement of the catheter into the target site. The IVUS transducer is usually operating at a frequency of about 10 to 20 megahertz. The IVUS catheters are available in two different types, a fixed array of mini transducers or a single rotating transducer.

What Are the Advantages of Intravascular Ultrasound?

The advantages of intravascular ultrasound are:

• Easy to use.

• Does not require radiation and contrast materials.

• Higher accuracy rate.

• Quick patient recovery.

What Are the Complications Associated With Intravascular Ultrasound?

The following are the complications associated with intravascular ultrasound:

• Arrhythmia (irregular heartbeat).

• Infection at the site of injection.

• Severe bleeding.

• Allergic reactions to medications.

• Difficulty in breathing.

• Heart attack.

• Stroke (a life-threatening condition in which blood vessels supplying the brain are blocked).

• Damage to the heart valve.

• Kidney failure.

• Vasospasm (narrowing of the blood vessels resulting in reduced blood flow).

• Thrombosis (formation of clots inside the blood vessels).

• Perforation.

What Are the Guidelines for the Use of Intravascular Ultrasound?

1. American College of Cardiology (ACC) Guidelines-

Class II A:

• IVUS can effectively assess left main coronary artery disease, which is indeterminant in angiography (level of evidence- B).

• IVUS and coronary angiography are performed four to six weeks and one year after the cardiac transplantation surgery (level of evidence- B).

• IVUS can determine the mechanism of stent restenosis (level of evidence- C).

Class ll B:

• IVUS can reasonably be used to assess non-left main coronary artery with intermediate coronary stenosis (50 to 70 percent of the diameter stenosis) (level of evidence- B).

• IVUS might be considered for guiding coronary stent implantation, particularly in the left main coronary artery stenting (LMCA) (level of evidence- B).

• IVUS can determine the mechanism of stent thrombosis (level of evidence- C).

Class lll:

• IVUS is not recommended for routine lesion assessment if revascularization with CABG or PCI is not contemplated (level of evidence- C).

2. European Society of Cardiology (ESC) Guidelines-

• According to the guidelines of ESC in 2018, IVUS can be used to detect the severity of the disease and plan the treatment of the unprotected left main coronary lesions (class ll a). ESC also recommends IVUS to detect restenosis and also in patient selection for stent implantation.

What Are the Limitations of Intravascular Ultrasound?

The limitations of intravascular ultrasound are:

• Sepsis or bacteremia.

• Bleeding disorder.

• Coronary artery spasm.

• Unstable blood flow.

• Fully blocked artery.

• Patients who are not eligible for coronary artery bypass grafting surgery.

• Patients who are not eligible for percutaneous transluminal coronary interventional procedures.

Conclusion:

The intravascular ultrasound (IVUS) procedure requires intracoronary nitroglycerin and systemic anticoagulant before the insertion of a catheter to prevent the risk of thrombus and vasospasm. The doctor should be very careful while visualizing highly tortuous blood vessels to avoid severe complications. If the procedure involves sedation, patients should not eat or drink anything for four to six hours before the procedure. IVUS can effectively visualize the plaques within the vessel wall (hidden) that cannot be seen on angiography.