Introduction
Angiographic procedures were first performed only months after Roentgen’s discovery of X-rays. Haschek and Lindenthal injected mercury salts into an amputated hand and created one of the first recorded images of the arterial system ( Fig. 43.1 ). This showed the enormous potential of radiographic visualization of the arterial system. In 1924, Brooks reported concentrated sodium iodide arterial injection as a means of demonstrating lower extremity vessels ( Fig. 43.2 ). Over the next 50 years, multiple contrast agents were used. Iodinated compounds initially used to treat infection were soon found to be X-ray contrast agents.
Conventional angiography plays a vital role in the diagnosis and management of peripheral vascular disease. Recently, advanced, non-invasive techniques, such as computed tomography angiography (CTA), magnetic resonance angiography (MRA), and vascular ultrasound have made a significant impact on the diagnosis of vascular disease. These modalities are safe and effective in characterizing vascular disease and providing critical preprocedure planning. Despite the increased use of noninvasive measures, conventional angiography remains the gold standard. Endovascular therapy is considered less invasive compared with traditional open surgery. It translates to lower cost, decreased recovery time, and fewer postprocedural complications. Although catheter angiography is considered an extremely safe procedure, it is not without risk, with complications seen in 3%–5% of cases. Using noninvasive modalities prior to angiography, procedure times and complication rates can be reduced. We will review some of the complications encountered during and following conventional angiography.
Selection of Access Site and Approach
Transfemoral (TF) arterial access is widely accepted as the standard approach for angiography. It is generally well tolerated; however, alternative approaches have recently been explored, including transbrachial (TB) and transradial (TR). Preprocedure planning with CTA or MRA have simplified angiography procedures. Through creating “road maps,” physicians are able to prepare appropriate access for the safest procedure to complete an intervention. TR access is found to be associated with lower complication rates compared with the TF approach. However, technical success for TR is slightly lower and requires increased familiarization for improved physician’s technical success. Additionally, vessel size must also be considered when planning an endovascular intervention.
Access Complications
The most frequently encountered angiography complication is related to vascular access, with an incidence reported from 0.1% to 23%. Postvascular access groin hematomas are the most common of these complications, with an incidence ranging from 5% to 23%. Groin hematomas are generally benign and self-limiting. Rarely, hematomas can become large and life-threatening, only discovered after the patient has had profound blood loss and resultant hypotension. Retroperitoneal hematomas are described in 0.1%–0.7% of the cases and are seen when femoral artery access is superior to the inguinal ligament ( Fig. 43.3 ).
More recently, access complication rates have been reduced when utilizing real-time ultrasound ( Fig. 43.4 ). The femoral artery access with ultrasound trial (FAUST) confirmed real-time ultrasound guidance statistically reduces the number of access attempts, time to access, and vascular complications. These complications are categorized as minor or major depending on the requirement of blood transfusion.
Additional access-related complications include pseudoaneurysm, vascular dissection, and arteriovenous fistula. A pseudoaneurysm is a defect in the inner two layers of the blood vessel (tunica intima and media). The incidence of pseudoaneurysms are described in 0.8%– 2.2% postinterventional procedures. The likelihood increases when the superficial femoral artery or profunda femoris is accessed ( Fig. 43.5 ). Small pseudoaneurysms can be monitored and often resolve spontaneously, but in other cases they may require treatment with ultrasound compression, thrombin injection, or surgery.
An arteriorovenous fistula (AVF) is an abnormal communication between an artery and a vein, which occurs in approximately 1% of cases. AVFs occur when the access needle crosses the wall of both the femoral artery and vein ( Fig. 43.6 ). Research suggests that at least one-third of AVFs resolve spontaneously. As such, follow-up imaging is initially suggested to avoid unnecessary interventions.
Vascular dissection is uncommon. If it is to occur, it is more frequently seen with diseased and tortuous vessels or traumatic sheath insertion. The dissection can occur both at the access site and further upstream ( Fig. 43.7 ).
In the majority of cases, a retrograde dissection is not clinically significant. If there is a symptomatic dissection, a pressure gradient should be measured across the dissection. Most pressure gradients should be treated with inflating an angioplasty balloon across the dissection and remeasuring the pressure gradient. If the dissection is not in the vicinity of a joint or osseous structure, a bare-metal stent can be placed to tamponade the false lumen. Knowing the vascular anatomy of the groin with a general awareness of the potential complications will help decrease the risk of vascular access related complications.
Contrast-Related Complications
Iodinated contrast agents are a fundamental component for conventional angiography. These agents are widely used in medical imaging because of their ability to opacify vascular structures. By manipulating various X-ray beam properties, a specific energy can be isolated that highlights the contrast material, optimizing vascular opacity. Reactions to contrast can range from minor allergic and physiologic reactions to life-threatening ones.
Iodinated contrast agents are subdivided into categories: osmolality (high, low, iso) and tonicity (ionic or nonionic). The most common combination is nonionic low osmolality with lower associated risk. In this group, reaction rates range from less than 1% for minor reactions to less than 0.1% for severe ones. Risk factors include prior contrast reactions, severe allergies, asthma, cardiac or renal disease, and increasing age. It is of note that shellfish allergy is no longer considered a risk factor for contrast reactions.
Acute contrast reactions are categorized into physiologic and allergic types. Physiologic reactions are thought to be related to a disruption in homeostasis. In increasing severity, physiologic reactions include flushing, warmth, nausea, vomiting, hypertension, chest pain, and seizures. Allergic reactions, on the other hand, are immunologic responses to intravenous contrast, most often type I hypersensitivity reactions. Allergic reactions, include rash, edema, nasal congestion, generalized erythema, hoarseness, throat pain, severe edema, laryngeal spasm, hypotension, and hypoxia. Contrast reactions usually occur within 1 hour, the majority within the first 5 minutes. It is critical to distinguish physiologic from allergic type reactions because treatments differ depending on etiology. Allergic reactions require premedication, but physiologic reactions do not.
Management of acute contrast reactions varies depending on severity. The first step in managing acute reactions is to assess and to categorize the reaction as mild, moderate, or severe. Clinical evaluation should include overall patient appearance, ability to speak, respiratory status (i.e., use of accessory muscles), skin, and vital signs. Mild reactions usually require no intervention beyond observation, although occasional antihistamines can be administered. This can be seen in cases such as mild urticaria. Moderate and severe reactions require more aggressive treatment. Bronchospasm is treated with β-agonists as the first line along with oxygen. More severe reactions require intravenous epinephrine. Laryngeal edema is often life-threatening and is treated with intravenous epinephrine. Differentiating a vasovagal response to anaphylaxis is critical. A vasovagal reaction is treated with patient positioning and intravenous fluids. Moderate and severe reactions are treated with intravenous atropine. However, anaphylaxis is treated with intravenous epinephrine. The American College of Radiology manual on contrast reactions is an excellent resource and should be required reading for physicians working with contrast agents.
Contrast induced nephropathy (CIN) is a controversial topic and the role intravascular contrast plays in its occurrence is questionable. The definition of CIN varies, but according to the acute kidney injury network, CIN is an absolute or percentage increase in serum creatinine levels compared with baseline (0.3 mg/dL or 50% above baseline) or urine output less than 0.5 mL/kg for at least 6 hours within 48 hours of contrast administration. For the general population with normal renal function, CIN approaches an incidence close to 0%. However, in patients with pre-existing chronic kidney disease, diabetes mellitus, or even increased age, the incidence of CIN increases to 20%–40%. It is important to identify these risks factors prior to giving intravascular contrast. CIN prevention starts with identifying the at-risk patients. If CIN occurs, laboratory values start increasing 1–3 days postinjection, peaking 3–5 days, normalizing in 7–14 days. CIN is thought to be self-limiting, and the mainstay of treatment/prevention is intravenous hydration. Research has been carried out to determine safe alternatives to iodinated contrast, particularly for at-risk patients. Gadolinium-based contrast agents were found to be well tolerated in patients with renal insufficiency (doses less than 0.3–0.4 mmol/kg) as well as associated with a decreased incidence of CIN. Given the risk of nephrogenic systemic fibrosis, the use of gadolinium for angiography has mostly disappeared. Furthermore, while carbon dioxide may not be considered the optimal imaging agent, it can also act as an alternative for patients with CIN or allergy, given its rapid clearance through the pulmonary system ( Fig. 43.8 ).
