17. Role of Cardiac Computed Tomography Before Implant

Published on 26/02/2015 by admin

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Last modified 22/04/2025

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History

The patient had a medical history of hypertrophic cardiomyopathy with progression to the dilated phase of cardiomyopathy (New York Heart Association class III) and conduction abnormalities, including a prolonged QRS duration of 154 msec with right bundle branch block (RBBB) and left anterior fascicular block. Her family history was positive for hypertrophic cardiomyopathy in her father and one brother. Genetic testing revealed a mutation in the TNNI3 gene, resulting in replacement of the normal glutamic acid codon with a glutamine codon at position 124 in the troponin I gene. She had no history of hypertension, dyslipidemia, diabetes mellitus, or tobacco use. An echocardiogram demonstrated an ejection fraction of 20% to 25%. She underwent attempted cardiac resynchronization therapy defibrillator (CRT-D) implantation at a different institution, but the coronary sinus could not be cannulated. In addition, concern existed about possible coronary sinus dissection. Therefore a CRT-D device was implanted, with the left ventricular lead port capped. The patient was referred for evaluation for potential upgrade to a CRT-D via the implantation of the left ventricular lead. Cardiac computed tomography angiography (CCTA) was ordered for further evaluation of anatomic abnormalities impeding coronary venous lead placement.

Current Medications

The patient was taking carvedilol 6.25 mg in the morning and 12.5 mg at night, enalapril 7.5 mg daily, spironolactone 25 mg daily, furosemide 10 mg daily, and potassium chloride 10 mEq daily.

Physical Examination

Laboratory Data

Comments

Renal insufficiency is a factor that must be taken into account with iodinated contrast studies, such as CCTA. This is an issue for the heart failure patient population who require CRT.

Electrocardiogram

Findings

The electrogram demonstrated an atrial paced rhythm and ventricular sensed rhythm at 60 bpm. The PR interval was 198 msec; QRS duration was 156 msec, with RBBB and left anterior fascicular block; and corrected QT interval was 450 msec. Left ventricular hypertrophy was present.

Echocardiogram

A transthoracic echocardiogram showed mild left ventricular enlargement with wall thickness at the upper limits of normal and severe global hypokinesis with akinesis of the midinferior wall, inferior septum, and apex. The left ventricular ejection fraction was 22%, with a left ventricular end-diastolic dimension of 54 mm, a posterior wall thickness of 11 mm, and an interventricular septal thickness of 12 mm. Mildly decreased right ventricular systolic function was noted, as well as biatrial enlargement, with a left atrial volume index of 43 mL/m2. The aortic valve was trileaflet, without aortic regurgitation or aortic stenosis. The mitral valve morphology was normal, with no evidence of mitral stenosis or regurgitation. No evidence of pulmonary regurgitation was seen. Trace tricuspid regurgitation was present, with an estimated right ventricular systolic pressure of 28 mm Hg. The right atrial pressure was estimated to be 5 mm Hg. The inferior vena cava size and respiratory variation were normal. No evidence of pericardial effusion was observed.

Cardiovascular Computed Tomographic Angiography

Findings

Coronary Venous Findings

The coronary sinus ostium was patent, with an ostial diameter of 1.2 cm. A prominent Thebesian valve was noted covering the coronary sinus ostium (Figure 17-1). The middle cardiac vein was followed by a posterior cardiac vein branching off 1.5 cm after the coronary sinus ostium with a gentle angulation of 146 degrees and coursed posterolaterally (Figures 17-2 to 17-4). At 6 cm distal to the takeoff of the posterior vein (mid to apical ventricular level), the vein bifurcated, with one branch coursing posteriorly and the other laterally. No evidence of a branch vein in the lateral territory of the left ventricle was seen. An anterior interventricular vein was present. No evidence of coronary sinus dissection was noted.

Other Cardiovascular Findings

The coronary artery system was right dominant, with normal location of the coronary artery origins. Evidence of calcified and noncalcified plaques was present, without evidence of severe coronary artery stenosis (Figure 17-5). The left ventricle was moderately dilated, with thinning and aneurysmal dilation of the apex. A thin layer of mural thrombus was seen in the region of the apical aneurysm (Figure 17-6). The left atrium was severely enlarged. The right ventricle demonstrated normal morphology. The right atrium was normal in size. A dual-chamber implantable cardiac defibrillator (ICD) was present with leads in the right atrial appendage and right ventricular apex. The aorta and pulmonary arteries appeared unremarkable.
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FIGURE 17-1 A two-dimensional oblique cardiac computed tomography angiography image demonstrates a prominent Thebesian valve (white arrows) covering the coronary sinus ostium.

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FIGURE 17-2 A three-dimensional cardiac computed tomography angiography reconstruction shows the coronary venous system. A posterior cardiac vein was present branching off 1.5 cm after the coronary sinus ostium coursing posterolaterally. At 6 cm distal to the takeoff of the posterior vein, the vein bifurcated, with one branch coursing posteriorly while the other branch coursed laterally. There was no evidence of a branch vein in the lateral territory of the left ventricle. The vein targeted for implant is shown (white arrow). CS, Coronary sinus; GCV, great cardiac vein; LA, left atrium.

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FIGURE 17-3 A three-dimensional cardiac computed tomography angiography reconstruction demonstrates localization of the myocardial segments associated with the posterior vein. The arrows demonstrate the myocardial location of the bifurcation of the vein at the mid to apical ventricular level.

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FIGURE 17-4 A two-dimensional oblique cardiac computed tomography angiography image shows the gentle angulation of 146 degrees of the posterior vein off of the coronary sinus. CS, Coronary sinus; Post vein, posterior vein.

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FIGURE 17-5 A two-dimensional oblique cardiac computed tomography angiography image showing the left coronary artery circulation without significant coronary artery disease. Cx, Circumflex coronary artery; LAD, left anterior descending coronary artery; LM, left main coronary artery; Ramus, ramus intermedius coronary artery.

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FIGURE 17-6 A two-dimensional chamber cardiac computed tomography angiography image demonstrates the left ventricle to be moderately dilated with thinning and aneurysmal dilatation of the apex. A thin layer of mural thrombus was seen in the region of the apical aneurysm (white arrows). The left atrium was severely enlarged.

Focused Clinical Questions and Discussion Points

Question

What are the potential anatomic limitations and challenges to left ventricular lead placement?

Discussion

Impediments to coronary venous lead placement are multiple and include (1) coronary venous valves or valve remnants, such as the Thebesian valve covering the coronary sinus ostium or Vieussen’s valve at the ostium of the great cardiac vein; (2) an unroofed coronary sinus; (3) coronary venous diverticulum, aneurysm, stenosis, or occlusion; (4) coronary sinus atresia; (5) absent or underdeveloped coronary veins in the target area for left ventricular lead placement; (6) procedural complications, such as coronary sinus dissection; (7) thoracic venous anomalies, such as a persistent left-sided superior vena cava draining into a dilated coronary sinus with or without a right-sided superior vena cava; (8) close proximity of the phrenic nerve to a coronary venous branch target site causing diaphragmatic pacing; and (9) presence of significant myocardial scar at the target coronary venous branch site.

Question

What information important to CRT can be gleaned from a CCTA relevant to CRT lead placement?

Discussion

CCTA can provide anatomic characterization for CRT implant, including right atrial size, coronary sinus ostial characteristics, presence and location of coronary sinus branch veins, angulation of the branch vein off of the the coronary sinus or great cardiac vein, course of the target vein, and assessment for anomalies that may limit lead placement (see previous question).1–7

Question

What are the current guidelines for coronary venous CT imaging?

Discussion

Based on the American College of Cardiology Foundation, Society of Cardiovascular Computed Tomography, American College of Radiology, American Heart Association, American Society of Echocardiology, American Society of Nuclear Cardiology, North American Society of Cardiovascular Imaging, Society for Cardiovascular Angiography and Interventions, and Society for Cardiovascular Magnetic Resonance 2010 Appropriate Use Criteria for Cardiac Computed Tomography, noninvasive coronary vein mapping before placement of a biventricular system was deemed appropriate with a score of 8/9.8 Preliminary data suggest that review of CT coronary venous angiography findings before CRT can facilitate placement of CRT devices.5

Question

What are the special considerations for coronary venous CT angiography in patients undergoing evaluation for CRT?

Discussion

Because patients undergoing evaluation for CRT have significant ventricular dysfunction, special considerations and potential limitations apply to coronary venous imaging. Patients must be able to lie in the supine position and follow breathing instructions for an appropriately timed breath-hold during imaging. Heart rate control can be challenging because some patients cannot be acutely beta-blocked to a heart rate of 60 bpm for imaging. Atrial or ventricular ectopy and arrhythmias such as atrial fibrillation can decrease study quality. Issues can relate to the volume load of contrast agent and iodinated contrast-induced nephrotoxicity.
The optimal timing of image acquisition in relation to administration of the contrast bolus may be delayed in patients with significant ventricular dysfunction as a result of prolonged circulation time of contrast to target structures. In addition, visualization of the coronary venous system requires a delay in triggering of image acquisition because contrast must course through coronary arteries to the myocardium and back through the coronary venous system. Coronary venous imaging can be achieved by performing a test bolus at the region of interest to assess timing before the study injection, with triggering based on a surrogate region of interest such as the descending aorta at the lowest slice of the study, adding several seconds to the timing based on a standard coronary artery study or using the timing of a standard coronary artery study with the trigger set at a higher Hounsfield unit threshold.

Question

What is the relevance of the Thebesian valve to cardiovascular procedures?

Discussion

The Thebesian valve is a remnant structure of the embryonic right valve, which commonly exists as a minimal remnant but can occur as fenestrated partial valve remnant, or fully formed valve. Thebesian valves can make coronary sinus cannulation more challenging for procedures such as coronary sinus catheter placement for electrophysiology studies, retrograde cardioplegia for cardiothoracic surgical procedures and CRT procedures. CCTA can allow visualization of prominent Thebesian valves, which may impede placement of left ventricular leads.9

Final Diagnosis

CCTA demonstrated a prominent Thebesian valve covering the coronary sinus ostium as the impediment to placement of the left ventricular lead via the coronary venous system.

Plan of Action

Some Thebesian valves are challenging to cross with standard approaches and require other methods, including (1) use of alternative guide wires and sheaths from a standard subclavian or cephalic approach; (2) a double cannulation technique in which the valve is opened using a catheter from a different approach via a femoral vein, subsequently allowing the guide wire, sheath, and left ventricular lead to be placed from a subclavian or cephalic approach;10 or (3) rarely an epicardial approach to left ventricular lead placement, which can be achieved through a minimally invasive surgical approach. In this case, the CCTA can help identify the target site in relation to the three-dimensional thoracic anatomy and skeletal structures for decisions as to the optimal incision site (Figure 17-7).
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FIGURE 17-7 A three-dimensional cardiac computed tomography angiography reconstruction demonstrates the relationship of the left ventricle to the skeletal structures. These views could potentially be useful to planning an epicardial approach to left ventricular lead placement.

Intervention

An upgrade procedure was performed with addition of a left ventricular lead through the coronary venous system to the CRT-D device. The device pocket was exposed through an incision at the site of the generator incision, and the generator was disconnected. Left subclavian venous access was obtained. A multipurpose curved catheter was advanced under fluoroscopic guidance over a Wholey wire (Coviden, Mansfield, Mass.) into the mid–right atrium, rotated septally, and advanced across the tricuspid annulus into the right ventricle. The catheter and wire were slowly pulled back with counterclockwise torque into the right atrium, rotating the catheter posteriorly. Once in the right atrium, the Wholey wire was advanced to gain access to the coronary sinus through the Thebesian valve. Because of the difficulty in advancing the multipurpose sheath into the coronary sinus, a flexible Terumo catheter (Terumo Medical, Somerset, N.J.) was advanced over the Wholey wire into the main coronary sinus body. Then the multipurpose sheath was advanced over the transit catheter and the Wholey wire into the main coronary sinus and great cardiac vein. A contrast injection was performed that identified the posterolateral branch vein. The Wholey wire and transit catheter were removed. The sheath was flushed, and the coronary venous lead was advanced over a PT2 wire (Boston Scientific, Natick, Mass.) and positioned in the posterolateral branch vein (Figure 17-8). Excellent sensing and capture thresholds were confirmed. Diaphragmatic stimulation was absent during a test pulse at 10 V and 2 ms.
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FIGURE 17-8 Fluoroscopy images show the multipurpose catheter that has been advanced beyond the Thebesian valve into the main body of the great cardiac vein, with subsequent deployment of the left ventricular endovascular lead.

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FIGURE 17-9 A chest radiograph demonstrates the final left ventricular lead position (white arrows).

Outcome

The patient had successful deployment of a coronary venous lead with a normally functioning CRT-D device (Figure 17-9).

Selected References

1. Auricchio A., Sorgente A., Soubelet E. et al. Accuracy and usefulness of fusion imaging between three-dimensional coronary sinus and coronary veins computed tomographic images with projection images obtained using fluoroscopy. Europace. 2009;11:1483–1490.

2. Cao M., Chang P., Garon B. et al. Cardiac resynchronization therapy: double cannulation approach to coronary venous lead placement via a prominent Thebesian valve. pacing and clinical electrophysiology. Pacing Clin Electrophysiol. 2012  in press.

3. Girsky M.J., Shinbane J.S., Ahmadi N. et al. Prospective randomized trial of venous cardiac computed tomographic angiography for facilitation of cardiac resynchronization therapy. Pacing Clin Electrophysiol. 2010;33:1182–1187.

4. Jongbloed M.R., Lamb H.J., Bax J.J. et al. Noninvasive visualization of the cardiac venous system using multislice computed tomography. J Am Coll Cardiol. 2005;45:749–753.

5. Mao S., Shinbane J.S., Girsky M.J. et al. Coronary venous imaging with electron beam computed tomographic angiography: three-dimensional mapping and relationship with coronary arteries. Am Heart J. 2005;150:315–322.

6. Mark D.B., Berman D.S., Budoff M.J. et al. ACCF/ACR/AHA/NASCI/SAIP/SCAI/SCCT 2010 expert consensus document on coronary computed tomographic angiography: a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents. Circulation. 2010;121:2509–2543.

7. Mlynarski R., Mlynarska A., Sosnowski M. Anatomical variants of coronary venous system on cardiac computed tomography. Circulation. 2011;75:613–618.

8. Shinbane J.S., Girsky M.J., Mao S. et al. Thebesian valve imaging with electron beam CT angiography: implications for resynchronization therapy. Pacing Clin Electrophysiol. 2004;27:1331–1332.

9. Taylor A.J., Cerqueira M., Hodgson J.M. et al. ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 appropriate use criteria for cardiac computed tomography: a report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. Circulation. 2010;122:e525–e555.

10. Van de Veire N.R., Marsan N.A., Schuijf J.D. et al. Noninvasive imaging of cardiac venous anatomy with 64-slice multi-slice computed tomography and noninvasive assessment of left ventricular dyssynchrony by 3-dimensional tissue synchronization imaging in patients with heart failure scheduled for cardiac resynchronization therapy. Am J Cardiol. 2008;101:1023–1029.

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