Angiography and Interventions

Workup of a Patient for Pulmonary Angiography

Clinical history, laboratory values, and medications should be reviewed. A clinical history of left bundle branch block places the patient at risk of a complete heart block while catheterizing the pulmonary arteries. Temporary cardiac pacing prior to the procedure may be considered in elective cases to mitigate this risk. Moderate pulmonary hypertension is a relative contraindication for pulmonary angiography. Iodinated contrast materials are known to cause pulmonary vasoconstriction and pulmonary edema, leading to increased right heart strain. The use of low-osmolar contrast material and limiting the injection volume can mitigate this risk. Similar to any other vascular procedure involving the use of contrast material, renal function tests, coagulation parameters, and platelet counts should be checked.

Performing Pulmonary Arteriography

The procedure can be safely performed under local anesthesia. Moderate sedation is often administered to reduce anxiety. Patients who cannot lay flat or hold their breath for 10 seconds or have a poor airway are best intubated for pulmonary angiography. If a left bundle branch is known, a temporary pacer is placed. Jugular or femoral vein access is established after administering local anesthesia. The choice of venous access is dependent on the operator's preference and length of the catheter or devices anticipated for the procedure. Shorter catheters and devices will require a jugular access. Most of the catheters used for pulmonary angiography are between 6 and 8 Fr. Standard pulmonary flush catheters (Grollman, Van Aman, Berman) have a 90-degree curve to facilitate maneuverability through the right heart. A pigtail catheter and a tip-deflecting guidewire can also be used to catheterize the pulmonary artery.

Pulmonary arterial pressures are measured with the catheter positioned in the right or left main pulmonary artery. A nonselective pulmonary trunk arteriography is rarely performed. Selective arteriography with the catheter tip in the right and left pulmonary arteries in the frontal and lateral projections is typically performed. The contrast material is injected at a rate of 15 to 20 mL/s, for a total volume of 30 to 40 mL ( Figs. 10.1 and 10.2 ). The images are acquired at a rate of six frames/s using digital subtraction angiography during a single breath-hold.

Complications of Pulmonary Arteriography

Minor complications, including access site complications, transient arrhythmias, and allergy to contrast materials occur in 5% of patients. Major complications include contrast-induced nephropathy, which occurs in 1%, and fatalities, which occur in 0.5%. With the advent of flexible catheters and nonionic contrast materials, the complication rates are even lower.

Pulmonary Arteriovenous Malformations

PAVMs are rare vascular anomalies of the lungs, in which abnormal dilated vessels provide a direct high-flow, low-resistance, right-to-left shunt between the pulmonary artery and vein. PAVMs are usually part of hereditary hemorrhagic telangiectasia (HHT), although sporadic cases occur in 30% of patients. Conversely, one-third of patients with HHT harbor a PAVM. Uncommon causes of PAVMs include trauma, malignancy, and hepatopulmonary syndrome. Patients may be asymptomatic, especially with a small PAVM, but larger lesions may present with hypoxia or heart failure from a right-to-left shunt. Other presentations are usually secondary to systemic emboli; these include transient ischemic attacks (37%), stroke (18%), brain abscess (9%), and seizures (8%). Rupture leading to pulmonary hemorrhage or hemothorax is a rare but well-known and dreaded complication. Diagnosis is usually with CT pulmonary angiography and bubble echocardiography. Endovascular occlusion of the feeding artery with fibered coils or vascular plugs is the mainstay of treatment.

Performing Embolization

Based on the location of the PAVM on CT pulmonary angiography, selective pulmonary angiography of the lung is performed. The feeding pulmonary arteries are identified ( Figs. 10.3 and 10.4 ). At our institution, the 7.0/5.0-Fr Lumax guiding catheter (Cook Medical, Bloomington, IN) is used to cannulate the feeding artery. Microcatheters are used if a more selective catheter position is desired. The feeding artery is occluded with fibered coils or vascular plugs ( Fig. 10.5 ). Coils or vascular plugs are selected based on the size of the feeding artery, with the coil usually oversized by 2 mm or 20% and vascular plugs by 30% to 50%. Embolization of the aneurysmal segment is not indicated. In the presence of a high-flow PAVM, a technique known as the anchor technique is used to prevent paradoxic embolization of the coil. In this technique, the initial segment of a long coil is first deployed in a proximal branch vessel (to anchor it to the branch) and the rest of the coil is then prolapsed into the feeding artery supplying the PAVM. The embolization procedure is much simpler with the use of detachable vascular plugs, especially in PAVMs with large but short feeding arteries.

Pulmonary Embolism

Systemic anticoagulation is the mainstay of therapy for acute PE. Systemic thrombolysis for massive and submassive PE has been well established. Intravenous infusion of tissue plasminogen activator (tPA) along with systemic anticoagulation decreases the risk of death (41% risk reduction compared to anticoagulation alone) and recurrence. However, systemic thrombolysis is contraindicated in the presence of a recent stroke or intracranial injury, intracranial malignancy, bleeding from any source in the body, and recent surgery. Intracranial bleeding is the most devastating complication of systemic thrombolysis, occurring with a frequency of 2% to 5%. Major bleeding complications, including retroperitoneal and gastrointestinal bleeding, occur in 9%. Catheter-directed thrombolysis (CDT) has been gaining acceptance in the treatment protocol for massive and submassive PEs by limiting the systemic side effects of thrombolysis.