Neuroangiography in Hemorrhagic and Ischemic Stroke
Pearls
Neuroangiography remains the gold standard for the evaluation of cerebrovascular diseases, and it is the foundation for neurointervention and neuroendovascular surgery.
The mastery of the techniques necessary for safe and effective neuroangiography is essential for anyone who is venturing into the area of neurointervention and neuroendovascular surgery.
Before starting the procedure, it is important to have a plan based on the disease being evaluated (which vessels to inject, which anatomic segment to image, need for three-dimensional imaging, etc.).
As with any other procedure, it is important to be familiar with the devices and other equipment.
Although very uncommon, severe complications may occur; it is important to be prepared to recognize and deal with them.
Neuroangiography is the dynamic study of the cerebral and spinal vasculature performed by means of an endovascular arterial catheter that is used to inject radiopaque contrast media. Imaging is then performed during the injection of contrast, and a series of arterial, capillary/parenchymal, and venous phase frames are acquired using the digital subtraction technique. Usually, repeat injections in multiple planes are necessary for an adequate cerebral study. More recently, three-dimensional (3D) rotational angiography has become an important tool in the angiographic evaluation of vascular lesions, particularly intracranial aneurysms, and may reduce the need for additional angulated series.
Despite the constant advances in and improvement of less invasive techniques such as magnetic resonance angiography (MRA) and computed tomography angiography (CTA), cerebral catheter angiography (CA) remains the gold standard for the evaluation of cerebrovascular diseases. Moreover, CA is the foundation for neurointervention, enabling the creation of a functional angiographic map that facilitates intelligent planning of targeted neuroendovascular surgical procedures. The mastery of the techniques necessary for safe and effective neuroangiography is essential for anyone who is venturing into the area of neurointervention and neuroendovascular surgery.
♦ Historical Facts
Wilhelm Conrad Roentgen produced and detected electro-magnetic radiation (x-ray) in November 1895.1
An angiographic study of an amputated arm was performed in Vienna using a mixture of quicklime, petroleum, and mercuric sulfide in 1896.2
Antonio Egas Moniz, a Portuguese neurologist who attended the Treaty of Versailles following World War I, and who received the Nobel Prize for developing frontal leucotomy as a treatment for psychiatric diseases, performed the first cerebral angiograms in cadavers. In 1927, he performed the first cerebral angiogram in a living human, assisted by his colleagues Almeida Lima and Almeida Dias; the patients had diagnoses of paralysis of the insane, parkinsonism, and brain tumors. Interestingly, the first patient with a successful series of angiographic images suffered thromboembolic complications and died soon after the procedure. In Moniz’s series, strontium bromide and then sodium iodide were used as contrast media.2 – 4
In 1931, Thorotrast, a colloidal solution of thorium, was used for cerebral angiography. Due to high rates of carcinogenesis, the use of this agent was discontinued in the early 1950s. Additional follow-up studies also showed a significantly increased incidence of malignancies (hepatobiliary, leukemia, and others) in patients who had received this agent.2 , 4
Cerebral angiography gained popularity and was established as an important tool for evaluation of intracranial diseases in the late 1950s; at that time it was performed by direct puncture of the cervical arteries.5
In the late 1960s cerebral angiography through femoral access was introduced.6
Until the 1970s, cerebral angiography was performed for evaluation of all kinds of intracranial processes; the development of computed tomography (CT) in 1973 resulted in a shift toward cerebral angiography being reserved predominantly for evaluation of neurovascular diseases.4
In the 1980s digital subtraction angiography (DSA) replaced film-screen techniques, and became the angiographic technique of choice, providing good resolution and image contrast with much more efficient workflow.
More recent technologies, including 3D rotational angiography and flat-panel detectors capable of acquiring data that can be reconstructed into computed tomography (CT)-like images, are rapidly becoming an essential component for diagnostic or therapeutic procedures in neurointerventional departments around the world.
♦ Performing a Neuroangiography
A physician who performs cervicocerebral or spinal angiography must have received adequate training based on published accepted standards, and must demonstrate high success and low complication rates.7 , 8 The procedure can be effective and safely performed using several different techniques depending on physician preference. It is important to mention that there is no “right” way to perform the procedure; however, safety thresholds need to be respected. Patient selection and preparation, meticulous technique executing the procedure, and postprocedural care are key steps to avoid complications.
Plan
Patient History and Review of Previous Studies
As in any other interventional procedure, the patient’s clinical history is extremely important. The rationale and the risks and benefits of performing the procedure need to be determined individually. It is important to ask if the patient’s clinical issue could be just as well assessed using a less invasive imaging modality such as magnetic resonance imaging (MRI), CT, MRA, or CTA. All prior procedures and imaging studies relevant to the case at hand need to be reviewed prior to the procedure during the decision-making process.
Allergies, Medical Problems, and Medications
Other important questions need to be addressed: Does the patient have an allergy to any medication or contrast agent that will be used during the procedure? Has the patient been exposed to iodine in the past (CT with IV contrast or intravenous urogram)? Does the patient need to be premedicated before the procedure? In our institution we use premedication when a prior reaction to iodine is reported, and if there is a history of a severe reaction, the procedure is performed with anesthesia standby, monitored anesthesia care (MAC), or, in the worst-case scenario, under general anesthesia (GA). Our premedication protocol includes 50 mg of prednisone administered 13 hours, 7 hours, and 1 hour before the procedure, and 50 mg of diphenhydramine given 1 hour before the procedure.
Coexistent medical problems such as high blood pressure, diabetes, decreased renal function or renal failure, and diseases that result in a prothrombotic state and require anticoagulation can also potentially increase the risks of the procedure and need to be factored in to the plan prior to the procedure. Certain medications that require special attention include heparin, warfarin, and metformin; any decision made to discontinue these medications before the procedure need to be discussed with the referring physician. In patients on heparin therapy, it is our practice to hold the heparin 2 hours before the puncture and restart it immediately after the procedure if a closure device is successfully deployed, or to restart it after 2 to 4 hours if manual compression of the puncture site is performed. Warfarin is usually stopped 5 days prior to the procedure and the international normalized ratio (INR) is rechecked the day before the procedure. It can then be restarted the same day after the procedure. It is important to discuss with the referring physician the need for heparin bridging therapy during the period when the INR is subtherapeutic, depending on the primary reason for anticoagulation. Metformin, an oral antihyperglycemic medication that is excreted predominantly by the kidneys, increases the risk of lactic acidosis, a rare but serious complication, when associated with contrast administration. It is recommended to hold the Metformin until 48 hours after contrast administration and restart it after making sure that renal function is normal.9
Another category of patients that requires special attention are those with decreased renal function. Because there is an increased chance of worsening renal function due to contrast-induced nephrotoxicity, pretreatment of this patient population is recommended. It is our routine to give two 1200-mg doses of N-acetylcysteine 12 hours prior to contrast exposure and two doses after the procedure. On the day of the procedure we hydrate these patients with an intravenous solution of sodium bicarbonate (150 mEq/L in 1000 mL of D5W), 3 mL/kg for the first hour before contrast administration and 1 mL/kg/h for 6 hours after the procedure. The use of low- or iso-osmolar contrast media is also important.10
Neurologic Examination
A baseline neurologic examination prior to the procedure is extremely important. Knowing the patient’s neurologic status also makes the clinical diagnosis of neurologic complications during the procedure fairly straightforward.
Laboratory Workup
The preprocedural laboratorial workup should include, at least, complete blood count, chemistry panel, and coagulation panel. Women should also have a pregnancy test done prior to the procedure to avoid radiation to the fetus, if possible. The most important questions to ask in regard to laboratory workup are the following: Is the patient severely anemic? Is the platelet count acceptable for the procedure? Is there an infection? What is the renal function? Are the prothrombin time (PT), INR, and partial thromboplastin time (PTT) acceptable for the procedure?
Type of Contrast to Be Used
Most contrast agents used for cerebral angiography are nonionic. Examples of nonionic low-osmolarity agents include iopamidol (Isovue; Bracco Diagnostics, Princeton, NJ), iohexol (Omnipaque; GE Healthcare, Princeton, NJ), ioversol (Optiray; Mallinckrodt, Hazelwood, MO), and iopromide (Ultravist; Bayer Vital, Leverkusen, Germany). The iodine content of the contrast media is included in the label for nonionic agents (e.g., Isovue-370 has 370 mgI/mL of solution; Omnipaque-300 has 300 mgI/mL of solution). For most nonionic agents, the osmolality depends on the concentration. Recently, a new nonionic contrast agent has been introduced; iodixanol (Visipaque; GE Healthcare, Princeton, NJ). A nonionic dimeric contrast agent that is iso-osmolar to blood, Visipaque 320, has 320 mgI/mL of solution with an osmolality of 290 mOsm/kg H2O.11 At our institution we reserve the use of iso-osmolar contrast agents for patients with decreased renal function or difficult spinal angiograms where increased volume of contrast might be necessary.
Sedation Assessment
Sedation assessment is another important issue. Does the patient have breathing problems? Are there airway/facial abnormalities? Does the patient have sleep apnea? Is there a history of airway problems or difficult intubation? Is the patient’s mental status depressed? Does the patient respond appropriately and follow commands? What is the American Society of Anesthesiologists (ASA) status? The vast majority of cases can be performed under moderate sedation (conscious sedation) as long as the patient responds purposefully to verbal commands or light tactile stimulation. In these cases spontaneous ventilation is adequate and no intervention is required to maintain a patent airway or cardiovascular function.12 Usually adequate moderate sedation can be achieved with the careful use of a sedative agent (commonly a benzodiazepine) associated with an analgesic drug (opioids). During the moderate sedation period the patient’s vital signs and responsiveness should be carefully monitored by an independent observer, to guard against respiratory depression. If oversedation occurs, the benzodiazepine should be reversed using flumazenil; for opioid reversal, naloxone is the agent of choice.13 , 14 Patients who are combative, who are not following commands, or who have delicate cardiovascular or respiratory stability may need anesthesia support (MAC or GA). In those cases an anesthesia consult is appropriate.
Arterial Access
Gaining access through a successful arterial puncture is the first step in cerebral angiography. Several different sites and arteries have been used for this particular purpose.2 , 4 , 6 , 15 – 18
The femoral artery puncture became the standard for access in the early 1970s. It was introduced in the late 1960s when most of the procedures were performed by direct puncture of the carotid or vertebral arteries.6 The common femoral artery should be punctured below the inguinal ligament. A high puncture can result in difficulty obtaining hemostasis at the end of the procedure and increases the risk of retroperitoneal hematoma. The femoral head can be used as a landmark for puncture. The skin incision should be performed over the inferior third of the femoral head after application of local anesthesia ( Fig. 11.1 ). This usually corresponds to 2 to 3 cm below the inguinal ligament. The puncture needle is then advanced in a 45-degree cephalad angle until the artery is punctured. Note that because the needle is angled superiorly, the artery will be punctured approximately 1 to 2 cm above the skin incision ( Fig. 11.2 ).
A variety of puncture techniques can be used, including single wall, double wall, and micropuncture depending on the physician’s preference. At our institution we routinely perform the arterial puncture using a micropuncture kit ( Fig. 11.3 ). In this technique a 21-gauge needle is used to puncture the artery. An 0.018-inch micro-guidewire is passed into the arterial lumen to the level of the common iliac artery or proximal abdominal aorta. The needle is then removed and the wire is kept in the vessel lumen. A 4- or 5-French (F) in troducer is then advanced over the wire. Subsequently, the inner part of the introducer and the micro-guidewire are re moved together and a 0.035-inch J-wire or Bentson wire is advanced into the abdominal aorta and the outer piece of the introducer is removed. After that, a 4F or 5F arterial sheath is inserted in the common femoral artery over the wire. Finally, the wire and the sheath’s inner portion are removed, leaving the outer canula in place. Axillary, brachial, and radial artery puncture follow the same principles.
It is our practice to always use arterial sheaths. It has been demonstrated in a randomized controlled trial that they de crease the incidence of intraprocedural bleeding at the femoral puncture site and increase the ease of catheter manipula tion without increasing the number of groin complications.19
Cerebral angiography using the radial or ulnar artery ap proach has been shown to be feasible and safe, with limited complications.15 – 17 , 20 In these cases the patient is examined using the modified Allen test to ensure adequate collateral circulation from the ulnar artery.16 , 17 , 20 The artery is then punctured using the micropuncture technique described above. Due to the small size of these vessels, some authors recommend infusion of a mixture of medications including heparin, verapamil, lidocaine, and nitroglycerin through the introducer sheath for vasospasm prevention or treatment.16 , 20 The main advantages of these approaches over the conventional transfemoral approach are easier hemostasis and greater comfort for the patient (the patient is not required to lie flat for several hours after the procedure).16 , 17 , 21
When extreme tortuosity of the aortic arch and proximal supraaortic trunks makes selective catheterization impossible via the transfemoral approach or through one of the upper extremities approaches, the cervical arteries can be punctured directly. In a recent series of patients who underwent endovascular treatment of intracranial diseases, direct puncture of the cervical arteries, predominantly the common carotid artery followed by the vertebral artery, was felt to be effective and relatively safe.18
Catheters
Many different catheter shapes have been used successfully in performing selective catheterization of the cervical arteries. In more than 90% of cases, all cervical vessels can be successfully selected using all-purpose catheters such as the angled taper, vertebral, Berenstein, Davis, and Headhunter types. If the aortic arch is elongated and very tortuous, or in cases of bovine arch, catheters such as the Simmons-II, Vitek, and HN-4 might be necessary to perform selective catheterization of the supraaortic arteries.
For spinal angiography, useful catheters include the Cobra-2, HS-1, Simmons-I, and Headhunter (useful for upper thoracic segmental arteries).
Continuous Flush Versus Double Flush
Here is another choice that is dependent on the operator’s experience and preference. Both techniques are effective and safe if used carefully. Using a continuous flush system, a solution of heparinized saline (3000 to 5000 U/L) is infused in a drip fashion under pressure through the catheter. This al lows for the catheter lumen to be filled by clean heparinized saline at all times, preventing blood stagnation and clot from forming within the catheter. At our institution, continuous flush is almost always used. Figure 11.4 shows our setup when a mechanical injector is connected and when hand in jections are used.
Double flushing the catheter is also very safe and effective as long as a meticulous technique is used. This technique consists of the aspiration of the catheter with one syringe to clear all bubbles and possible clots from the catheter lumen. This syringe is then disconnected and another syringe with clean heparinized saline is subsequently connected to the catheter. A small aspiration with subsequent flush of the catheter with heparinized saline is then performed. This maneuver should be repeated every time a wire is used and every time a new vessel is selected, or every 2 minutes, to prevent clots from forming in the catheter lumen.
Selecting Cervicocranial Vessels
After selecting the catheter of choice, the cervicocranial vessels are selected using standard over-the-wire technique. In this technique, a hydrophilic wire is advanced carefully under fluoroscopic guidance to select the target vessel. Subsequently, the wire is pinned and the catheter is advanced over the wire into the target vessel. Depending on vessel tortuosity, the presence of atherosclerotic disease, or operator preference, techniques such as roadmap or fluoro-fade guidance can be of significant help during this task ( Fig. 11.5 ).
Another technique frequently used is the puff-and-push technique. Using this technique the operator connects a syringe of contrast directly to the catheter or flush system. The operator then repeatedly puffs small amounts of contrast and pushes the catheter into the target vessel without a guidewire in place. In this technique it is very important that the sequence of tasks is respected. Puffing first displaces the tip of the catheter away from the vessel wall, allowing the catheter to be pushed safely into the target vessel. This technique should be used in young patients with fairly straight anatomy and no significant atherosclerotic disease. In older patients with tortuous vessels and significant atherosclerotic disease, the over-the-wire technique is safer and should always be used.
Catheter-Induced Vasospasm
It is important that when advancing the wire or catheter that the vessel anatomy and its curves be respected to avoid complications such as dissection or severe vasospasm ( Fig. 11.6 ). Catheter-induced spasm is usually a self-limited condition and requires no treatment in most cases ( Fig. 11.7 ). If severe catheter-induced vasospasm is noted, slow infusion of 1 to 5 mg of verapamil or 100 to 200 μg of nitroglycerin can be used to treat it.22
For spinal angiography the selective catheterization of the thoracic and lumbar segmental arteries are performed using anatomic landmarks with sequential catheterization of the levels above or below on each side.
Contrast Injection Rates (Mechanical Power Injection Versus Hand Injection)
The suggested rates and volumes of contrast for mechanical power injections are as follows:
Aortic arch: 20 to 30 mL/s for 25 to 40 mL of contrast
Common carotid artery: 7 to 10 mL/s for 10 to 14 mL of contrast
Internal carotid artery: 4 to 6 mL/s for 6 to 10 mL of contrast
External carotid artery: 1 to 3 mL/s for 4 to 6 mL of contrast
Vertebral artery: 3 to 6 mL/s for 6 to 8 mL of contrast
Subclavian artery with pressure cuff inflated on the ipsilateral proximal upper extremity: 7 to 9 mL/s for 15 to 20 mL of contrast
Segmental arteries (intercostal or lumbar): 1 to 2 mL/s for 4 to 6 mL of contrast
A randomized study demonstrated no statistically significant difference between these methods when evaluated for image quality and contralateral vessel reflux. The radiation exposure to the operator’s hand and body, however, was reduced by up to 70% by using a mechanical injector during selective digital subtraction cerebral angiography. There was also a tendency of increased safety favoring mechanical injection, as all complications in the study were related to hand injection.23 Figure 11.4 shows our setup when a mechanical injector is connected and when hand injections are used.
No matter which technique is used, the operator needs to be attentive when setting up the mechanical power injector or when hooking up the contrast syringe for hand injection, so that no air is introduced into the system and subsequently injected into the patient’s intracranial circulation. Air embolism is known to cause neurologic deficits in humans.24 Interestingly, in a study where transcranial Doppler ultrasonography was used to monitor the presence of air emboli in the middle cerebral arteries of seven patients undergoing cerebral angiography, air embolism was noted in all cases, but none of the patients developed a focal neurologic deficit, suggesting that, in most cases, small degrees of air embolism do not result in focal neurologic deficit.25
Standard Imaging and Projections
Every cervicocerebral angiogram should start with a posteroanterior (PA) and lateral view of the anterior circulation ( Fig. 11.8 ) and a Towne and lateral view of the posterior circulation ( Fig. 11.9 ). At our institution we also perform a set of bilateral obliques for each internal carotid or vertebral artery injected. Depending on the pathology being evaluated, special techniques such as 3D rotational angiography for aneurysms or increased frame rate (6 frames/second) for documenting arteriovenous malformations and fistulas may be helpful.
Manual Pressure
Manual compression at the site of arterial puncture is a feasible, very safe, and effective method to achieve hemostasis for most patients undergoing a diagnostic neuroangiogram where a 4F or 5F sheath is used. The major disadvantages of this method are patient discomfort during the compression period and the necessity of bedrest with the patient lying flat for 2 to 6 hours afterward.26 – 28 Patients on oral antiplatelet agents such as aspirin and clopidogrel may require slightly prolonged compression times. Anticoagulation (heparin) should be stopped 2 hours before the procedure and restarted 2 to 4 hours after hemostasis is achieved with manual compression.
Manual compression should be performed with three fingers immediately above the skin incision. This technique ensures that the compression is being made exactly at the arterial puncture site (usually 2 cm above the skin incision). The amount of pressure held should be enough to avoid subcutaneous collections or external oozing, but the femoral pulse should always be felt. Extreme compression can result in vessel occlusion. Manual compression is usually held for 10 to 20 minutes depending on the case. After this period the physician should inspect the groin, making sure that no hematoma has formed or is actively forming, even in the absence of external oozing. The lower extremity pulses are again reevaluated to ensure adequate lower extremity blood supply. The patient is then kept in an observation unit with orders for bedrest with the patient lying flat for 4 hours. After the initial 4 hours the patient can sit, and after another 2 hours the patient is allowed to ambulate. The punctured groin and lower extremity pulses, along with the patient’s vital signs, are monitored every 15 minutes during the first hour, every 30 minutes during the next 2 hours, and every hour for the last 3 hours.
Related posts:
Positron Emission Tomography in Ischemic and Hemorrhagic Stroke
Computed Tomography in Hemorrhagic and Ischemic Stroke
Ultrasound Assessment in Ischemic and Hemorrhagic Stroke
Promising Developments in Stroke Imaging
Magnetic Resonance Imaging in Hemorrhagic and Ischemic Stroke
Fibrinolysis for Cerebral Ischemia
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