Arterial disease includes those conditions that can obstruct blood flow (embolism and thrombosis), compromise the arterial wall integrity risking rupture (aneurysms), or result in abnormal flow of arterial blood, e.g., arteriovenous fistulas. There are many ways in which to pursue the cause(s) of arterial disease upon which to base a rational therapeutic plan:
- CT, MRI, and other imaging technologies
- Arteriography to delineate a “road map” of the arterial tree and where it may be compromised within
Duplex ultrasound is the combination of two different ultrasound modes–the B (brightness) mode to construct a picture of the arterial structure and identify obstructions and thrombosis/emboli and Doppler to study movement, i.e., blood flow. Other non-invasive tests, such as segmental blood pressures to assess the arterial circulation can be useful, but aside from the simple blood pressure measurements, ultrasound remains the easiest, least expensive, and most readily available way to begin the process of diagnosing arterial disease. Even the minimally invasive CT and MRI imaging involve contrast which means each is not totally benign. For these reasons, duplex ultrasound is typically used for the initial investigation into those suspected of having arterial disease or for those at increased risk for it.
- Claudication (symptoms of pain in limbs with exertion)
- Signs of tissue ischemia, such as discoloration, ulceration, or skin integrity
Those at Risk:
- Dyslipidemia (high cholesterol/triglycerides)
- Previous trauma
- Conditions in which emboli are possible, such as atrial fibrillation
Arteriography (Arterial Angiography)
Once a diagnosis is proposed–or strongly suspected–catheter-based arteriography is the definitive vascular imaging modality to confirm it, often used to advantage if there is to be simultaneous intervention, such as removal of emboli. It can also serve to identify collateral circulation. Since contrast is used, whether the study be X-ray, fluoroscopic, CT, or MRI angiography, it is considered invasive, with complications possible, such as arteritis, sepsis, anaphylaxis, and nephropathy.
Arterial angiography can identify compromised blood supply to different organs and tissues distal to the point of blockage:
- Traumatic interruption
- Mesenteric ischemia
- Atherosclerosis of large (femoral, iliac) and smaller (carotid, coronary) vessels that can explain conditions from claudication to Raynaud’s phenomena
- Dissection of aortic aneurysm that blocks an area of arterial branching, compromising tissue distal to it
- Cardiac vegetation lesions that can separate as emboli
Diagnosis with Arterial Angiography
The following angiography techniques are used for diagnosing arterial disease:
- Ultrasound not true angiography is used to screen high-risk patients and to begin the investigation into possible arterial disease. Once arterial disease is suspected, more invasive methods (angiography) are indicated.
- MRI angiography with contrast (MRA): This uses the polarity of atoms in tissue to render an image. It has the highest accuracy in diagnosing arterial disease. Because of the contrast used, it has the highest likelihood of complications, but not the most severe. Its chamber is constricted and the machinery loud, so severe claustrophobia can make it unfeasible without sedation.
- CT angiography is a computed series of thin X-ray slices that are reconstructed into a continuous image. It is a good choice for those for whom contrast is contraindicated (allergies, kidney disease), but it is considered less accurate because of the absence of–or its reduced doses of–contrast for image enhancement. It is used for assessment of abdominal aortic aneurysms.
- Conventional (X-ray and fluoroscopic) angiography. Although it does not have the highest frequency of complications, it has the most severe complications and considerations, such as loss of control of arterial puncture, higher ionizing radiation, potential for nephrotoxicity and permanent kidney damage, and anaphylactic reaction to the contrast agent.
Arterial Angiography for Specific Arterial Conditions
- Abdominal aortic aneurysm: CT is the most useful.
- Thoracic aortic aneurysm: usually diagnosed incidentally by X-rays. Ultrasound, MRI, and CT imaging ordered for other reasons may discover a previously unknown thoracic aortic aneurysm. Once discovered, CT or MR angiography are the best ways to further analyze the pathology and follow its progress.
- Peripheral aneurysm: abdominal and pelvic CT angiography is used for symptomatic patients. MRA is useful as well, but not typically used due to expense and issues with metal implants.
- Aortic dissection: CT angiography is the most common method of imaging aortic dissection.
- Atherosclerosis: atherosclerotic plaques that can compromise blood flow or pose a risk for emboli are initially studied using ultrasound and then further investigated using CT angiography.
- Blunt aortic injury: CT angiography is the most common method of imaging traumatic aortic injury, usually because of its ready availability to most ER facilities where trauma patients first land.
- Carotid artery stenosis: cerebral angiography, using reduced contrast doses and small catheters, is used. It can allow visualization of the entire carotid arterial system for atherosclerosis, plaques, and collateral circulation which can affect management. Alternately, duplex ultrasound can be used, but its accuracy depends on the skills of the ultrasonographer.
Management of Arterial Angiography
Once arterial disease is diagnosed, its management depends on what type of pathology is involved and whether the condition is stable vs. warranting urgent treatment.
- CT angiography: Is used to follow aortic aneurysms and once a crucial threshold is breached (usually > 5.5 cm diameter or an acceleration of expansion) the risk of imminent rupture outweighs any risks to surgical intervention or grafting insertions via arteriography, and such intervention is planned and carried out.
- Atherosclerosis: Is treated by minimizing the aggravating factors: weight management, antihypertensive medications, statin drugs for cholesterol/triglyceride elevations, smoking cessation, and supervised physical exercise.
- Ischemia: In distal organs due to emboli are invasively addressed radiographically using arteriography. An invasive interventional radiologist or vascular interventionist can thread a catheter to the involved area under fluoroscopic guidance to destroy or remove the blockage, reestablishing blood flow to the organ in danger of ischemia.
- Treatment of arterial thrombus formation: is via anticoagulation therapy for several months accompanied by imaging the area(s) for resolution or extension.
- Congenital arteriovenous fistulas: Which allow high-pressure arterial flow to enter the low-pressure venous flow, is corrected surgically to prevent the complications of varicosities, nerve compression, and deep vein thrombosis associated with this abnormality. Dialysis patients, for whom an AV fistula is created for therapeutic reasons, must be assessed for the same complications a spontaneous or congenital AV fistula can produce.
- Carotid endarterectomy or stenting: Is used to treat carotid stenosis once criteria are reached (per cent of blockage or appearance of symptoms such as TIAs or strokes). Arteriography plays an important part in determining the treatment threshold.
Prevention of Conditions That Are Diagnosed with Arterial Angiography
Prevention of conditions that are diagnosed and followed via arterial angiography is centered on conventional preventive medicine:
- Diabetics: Can prevent hyperglycemia-related arterial complications by strict glycemic control and maintaining a constant glycated hemoglobin A1c of <7.0%.
- Atherosclerosis: Requires preventive measures to avoid progression or its complications, including plaque formation, carotid stenosis, coronary artery disease, TIAs, and stroke. Prevention is centered on weight control via nutritional consultation, lipid management with statins, treatment of hypertension with antihypertensives and dietary changes, reducing the severity of any metabolic syndrome with lifestyle alterations and possibly metformin, and exercise.
- Aneurysms: Cannot be prevented, but arterial angiography can prevent progression or rupture via serial measurements of the diameter of the aorta or other arteries with similar arterial wall weakness. This includes the prevention of further dissection that can become life-threatening.
- The altered hemodynamics of arteriovenous fistulas: Can be corrected surgically to prevent venous complications from continuity with the high-pressure flow of arteries.
- Ischemia and necrosis distal to blockage of arterial blood flow: Is prevented by resolution of such blockages (thrombi), either mechanically (interventional arteriography), dissolution with intra-arterial agents, or recanalization with stents.