Pulmonary Emboli: Arteriography, Thrombectomy, and Thrombolysis

Ugur Bozlar

Ulku C. Turba

Krishna Kandarpa

Klaus D. Hagspiel

Pulmonary Arteriography

Advances in less invasive radiographic modalities, such as computed tomography pulmonary angiography (CTPA), alone or in combination with strategies that include clinical risk scores, venous ultrasound, and measuring serum D-dimer levels, have significantly diminished the diagnostic role of catheter-directed arteriography in pulmonary embolism (PE). Nevertheless, arteriography remains useful for adjudication (relative to other modalities) of suspected PE, vascular anatomic diagnosis, and treatment (1).

Indications

Diagnosis of Pulmonary Embolism

1. To reconcile a discrepancy between the clinical index of suspicion for a pulmonary embolism (PE) and the results of a CTPA or assessment of its probability on radionuclide ventilation-perfusion ([V with dot above]/[Q with dot above]) scan

2. Prior to inferior vena cava (IVC) filter placement, especially if extremity deep vein thrombosis (DVT) or renal vein thrombosis could not be documented as a source for emboli (1)

Treatment of Pulmonary Embolism

1. Anticipated interventional management (thrombolysis and/or inferior vena cava filter [IVCF] placement)

2. Knowledge or suspicion of massive PE, as a cause for hemodynamic compromise in a patient who may benefit from emergency percutaneous or surgical thromboembolectomy. Echocardiography and intravenous (IV) digital subtraction angiography (DSA) may have a diagnostic role in this setting.

3. Evaluation of chronic thromboembolic disease in the central pulmonary arteries causing pulmonary hypertension in patients who are potential candidates for thromboembolectomy (2)

4. Measurement of right ventricular end-diastolic pressure to assess and minimize risk of bleeding when anticoagulation therapy is contemplated

5. Nondiagnostic or negative CTPA despite very high clinical suspicion of PE, particularly when treatment without definite evidence carries a high risk (i.e., when unequivocal establishment or exclusion of the diagnosis of PE is required)

Diagnosis of Cardiopulmonary Anatomy

1. Evaluation and transcatheter treatment of congenital abnormalities

2. Evaluation and treatment of arteriovenous malformations/fistulas (acquired and congenital), and hemoptysis with negative bronchial arteriogram

Relative Contraindications

Cardiac evaluation may be needed in certain cases.

1. Coexistent severe pulmonary hypertension (see item 3 under “Procedure”). Noninvasive assessment of pulmonary pressure by echocardiography or crosssectional imaging methods may be helpful.

2. Left bundle-branch block on electrocardiogram (ECG). Place a transvenous pacing catheter to break complete heart block in the event that catheterinduced right bundle branch block (RBBB) occurs.

3. Ventricular irritability. Perform a pulmonary arteriogram only if the risk of anticoagulant or thrombolytic therapy is high because objective evidence of PE is mandatory prior to therapy.

4. Other concomitant life-threatening illness (e.g., congestive heart failure) should be evaluated and treated appropriately before the patient is subjected to pulmonary arteriography.

5. Severe prior documented contrast reaction

Preprocedure Preparation

1. Perform standard preprocedure preparation for angiography (see Chapter 1). Determine if there is an indication for filter placement, if the study is positive.

2. Check cardiopulmonary status (history, physical exam, diagnostic tests, etc.). Although individual clinical and laboratory parameters may be nonspecific, a combination of significant manifestations suggestive of PE is valuable in selecting patients for further diagnostic studies (3).

3. Review: Chest x-ray, ECG (rule out acute myocardial infarction, assess arrhythmias, and evaluate right ventricular strain [P-pulmonale, right-axis deviation, RBBB, or S1Q3T3]), [V with dot above]/[Q with dot above] scan, CTPA, venous studies, right-sided hemodynamics (if available from previously placed Swan-Ganz catheter); pulmonary capillary wedge pressure is useful in ruling out left-sided heart failure. Right ventricular end-diastolic pressure (RVEDP) and pulmonary artery (PA) pressure can determine the degree of pulmonary hypertension and serve to guide a tailored pulmonary angiogram.

4. Check serum electrolytes, blood urea nitrogen (BUN)/creatinine (Cr), coagulation parameters (partial thromboplastin time [PTT] <1.5 times control; prothrombin time [PT] <15 seconds), and platelets (>75,000 per µL).

5. Treat arrhythmias with prophylactic lidocaine 50 to 100 mg IV; obtain cardiology consult, if needed.

6. Study must be done with continuous cardiac monitoring in all patients. Prepare to place and activate transvenous pacer if the patient has a left bundle-branch block.

Procedure

1. Venous access: generally into the femoral veins (preferably right) if there is no evidence of iliofemoral thrombosis. Up to 14% of patients undergoing pulmonary angiography can have thrombus in the IVC (1). If in doubt, perform limited ultrasound of the femoral veins prior to puncture and perform venography of pelvis and/or IVC.

2. Catheters

a. Femoral access: Placement of a venous sheath is recommended but not necessary. Preshaped catheters (e.g., Grollman) or pigtail catheters maneuvered with a tip-deflecting wire may be used. Higher profile catheters are used for cut-film angiography. New lower profile catheters may be used, along with DSA, as long as contrast can be safely injected at the required flow rates.

b. Jugular or brachial access: Preshaped low-profile catheters are available that enter the PA without a need for tip-deflecting wire.

c. A Swan-Ganz catheter, for pressure measurements and possible subselective balloon occlusion injections, is suitable for introduction through all access sites. This catheter also may be exchanged over a wire for another diagnostic catheter, if necessary. This should be done expeditiously to avoid inducing arrhythmias when the endocardium is exposed to the bare guidewire.

3. Measure right heart pressures. About 30% of patients undergoing pulmonary angiography can have pulmonary hypertension (3). RVEDP must be 20 mm Hg or less (and PA systolic pressure ≤70 mm Hg); if these pressures are greater, the mortality associated with pulmonary angiography is increased (approximately 2% to 3%) (1). In such a case, use subselective injection (with balloon occlusion technique, if necessary) and nonionic contrast media. These safety measures are even more important if cardiac output is determined to be below normal (1).

4. Arteriographic technique

a. Contrast agents: Nonionic low osmolality contrast agents are preferred and considered mandatory for patients with elevated right-sided pressures. Lowcost alternative agents are acceptable when right-sided pressures are normal.

b. Injection rates

(1) Selective arteriography: right or left PA, 30 to 50 mL at 15 to 25 mL per second

(2) Subselective arteriography: Use the CTPA or [V with dot above]/[Q with dot above] scan as guide, especially for patients with pulmonary hypertension (RVEDP ≥20 mm Hg). Adjust the rate and volume according to the size of the region to be studied (5 to 15 mL per second for 2 seconds; with balloon occlusion, no more than 5 to 7 mL total volume followed by rapid deflation of the balloon) (1).

(3) Main PA injection: 70 mL at 35 mL per second, for the anatomic evaluation of central pulmonary arteries with congenital anomalies

(4) Injection rates may be modified with DSA imaging and/or dilution of contrast agents.

c. Imaging: Use CTPA or [V with dot above]/[Q with dot above] scan as a road map; the demonstration of a single clot is usually all that is necessary to make a therapeutic decision.

(1) Always obtain images with maximal inspiration.

(2) Begin with ipsilateral anterior and posterior oblique (45- to 60-degree) views of the side most suspected on prior studies. Additional anteroposterior (AP) views may be needed on occasion.

(3) Superselective magnified peripheral views may be needed, especially if prior studies suggest small peripheral emboli, which can be missed when injections are made centrally (4,5). Of the 76% of Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) I patients
who had only a single clot on the angiogram, 25% of these clots were located peripherally (1). Moreover, very high false-positive rate (75%) for subsegmental embolus detection with CTPA in PIOPED II patients emphasizes the role of superselective magnified peripheral views if a definitive result is required (6).

(4) If a balloon catheter is used for subselective injection, make sure that it is never totally occlusive during the injections and is rapidly deflated after the injection.

(5) In the event of suspected procedure-related cardiac trauma, stop the procedure immediately. Evaluate the patient for cardiac tamponade (pressures, ECG, emergency echocardiogram on the table). Proceed only after the suspicion has been ruled out.

(6) If a patient with PE on arteriography has a contraindication to anticoagulant or thrombolytic therapy, percutaneous placement of an IVC filter should be considered before the catheter is removed.

Postprocedure Management

1. Standard postangiographic management

2. Cardiac trauma: Discontinue anticoagulants; admit to cardiac intensive care unit.

3. Arrhythmias: For frequent premature ventricular contractions (PVCs): bolus lidocaine 50 mg IV via catheter into right atrium (RA) (total up to 100 mg).

Results

Sensitivity

If done promptly and carefully, the sensitivity of pulmonary arteriography is extremely high. A negative angiogram of high quality essentially rules out a clinically significant PE (1). The false-negative rate of angiography (determined by follow-up surveillance) was 0.6% in the PIOPED I study (1).

Results of PIOPED II study showed a need for additional testing when multidetector computed tomographic angiography (CTA)-computed tomographic venography (CTV) results were negative in the setting of high clinical index of suspicion, given the 18% false-negative rate of CTPA-CTV in such cases (up to 40% false negatives for CTPA only). However, the additional testing is not necessarily limited to pulmonary DSA but could include lower extremity venous ultrasound and [V with dot above]/[Q with dot above] scanning (6). A normal lower extremity imaging study (either by CTV or ultrasound) is needed before anticoagulation is withheld in patients with suspected PE, but normal pulmonary CTA.

Specificity

Using the rigid criteria of unequivocal intraluminal filling defect or abrupt arterial cutoff, the specificity of pulmonary arteriography is almost 100% (1).

Image Interpretation

1. A pulmonary angiogram performed 24 hours after the acute episode may be falsely normal because fragmentation and partial lysis can occur within this period.

2. The only definitive angiographic sign of PE is unequivocal evidence of an intraluminal filling defect or abrupt arterial cutoff, or both.

3. Careful interpretation of pulmonary angiograms in the setting of chronic pulmonary thromboembolic disease

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