May 28 – 30, 2015, Montréal, Québec

Cardiac Devices and Peri-Operative Cardiac Surgery Appearances

Dr. Bruce PreciousDalhousie UniversityFriday, May 29, 2015

Disclosure Statement: No Conflict of Interest

May 28 – 30, 2015, Montréal, Québec

I do not have an affiliation, financial or otherwise, with a pharmaceutical company, medical device or communications organization.

I have no conflicts of interest to disclose ( i.e. no industry funding received or other commercial relationships).

I have no financial relationship or advisory role with pharmaceutical or device-making companies, or CME provider.

I will not discuss or describe in my presentation at the meeting the investigational or unlabeled ("off-label") use of a medical device, product, or pharmaceutical that is classified by Health Canada as investigational for the intended use.

Objectives

• At the end of this session, participants will be able to:

• Recognize cardiac devices on imaging and assess for their related complications.

• Identify cardiac surgery preoperative planning concerns and postoperative complications on imaging.

• Manage the technological aspects of imaging cardiac devices and peri-operative issues in cardiac surgery patients.

Cardiac Devices

Pacemakers and ICDs

• Permanent pacemakers: pulse generator (battery pack and control unit) and lead wires with electrodes

• Single-lead (RV apex)• Dual-lead (RAA and RV apex) • Biventricular (RAA, RV apex and LV pacing electrode through coronary sinus

and into a left ventricular cardiac vein)

• Automatic implantable cardioverter-defibrillator (AICD) can be combined with the pacemaker

• Single high-voltage shock coil within the right ventricle• Additional coil in the SVC or brachiocephalic vein• Coils can be positioned either within a single wire or in two separate wires

Normal lead placement

• Right atrial lead:• In right atrial

appendage• First course inferiorly

into the right atrium, then curve upward and anteriorly

Normal lead placement

• Right ventricular lead:• At apex of the right

ventricle• On frontal view: tip to

the left of the spine• On the lateral view:

tip pointing anteriorly and either superiorly or inferiorly

• Can be placed in other locations (e.g. RVOT)

Normal lead placement

• Left ventricular lead:• Through the coronary

sinus into a left ventricular cardiac vein

• On frontal view: courses inferiorly and laterally

• On lateral view courses posteriorly

Variant: lead in RVOT (intended location)

Variant: RV ICD lead via left SVC

Pacemakers and ICDs – Acute Complications• Pneumothorax• Vascular injury• Myocardial perforation• Improper seating of a terminal connector pin within the connector

block (causes failure of lead to capture the cardiac rhythm)

Post pacemaker insertion hydropneumothorax

RV lead perforation

SVC perforation during pacemaker implantation: contrast from fluoroscopy seen in right pleural space on non-contrast post procedural CT

Reference: Aguilera A, et al. Radiography of Cardiac Conduction Devices: A Comprehensive Review. RadioGraphics 2011; 31:1669–1682.

Improper seating of the terminal connector pin within the connector block

Proper seating of the terminal connector pin within the connector block

Pacemakers and ICDs – Chronic Complications• Chronic complications related to CCD leads include:

• Lead fracture• Damage to the lead insulation• Lead displacement

• Myocardial perforation • Lead fractures are most common:

• At the venous access site (result of compression of the lead between the clavicle and the first rib)

• Near the tip of the lead or near the pulse generator

• Manipulation of the pulse generator by the patient causing it to rotate within its pocket can cause lead dislodgement (“twiddler syndrome”)

Damage to lead insulation at the venous access site (result of compression of the lead between the clavicle and the first rib)

Lead migration: pulse generator rotated and LV lead now in RA

Lead migration and perforation: RV lead extends beyond margin of RV apex

Perforation of implantable leads

• Can be acute or have a delayed presentation (defined as more than 1 month after implantation)

• Usual workup of suspected lead perforation: • device interrogation, • CXR• Echo• Fluoroscopy

• CT can be helpful when echocardiographic findings are equivocal• Precise location of the lead tip can be difficult to determine due to streak artifact• Findings of near perforation (lead tip close to the epicardium) are not an

indication alone for lead removal

CT technique for evaluation of perforation of implantable leads

• ECG gating (can be prospective or retrospective – 70% of R-R)• Can be done without beta blockade• Thin slices (at least 2mm but 0.6 mm better) with MPR• Can be done without contrast• Dual energy and IR to reduce streak artifact

Intraaortic Counterpulsation Balloon Pump (IABP)

• IABP is a supportive mechanical device used in the setting of cardiogenic shock to increase coronary artery perfusion

• Made up of:• catheter• inflatable balloon (approximately 25 cm long)• cylindrical radiopaque marker at the tip

• The radiopaque tip marker should be in the descending thoracic aorta 2 cm distal to the origin of the left subclavian artery (just distal to the aortic arch).

• A long tubular radiolucent structure in the aorta can be seen on CXR if the balloon is inflated (during diastole) when the image is acquired

Intraaortic Counterpulsation Balloon Pump (IABP)

• Complications:• Overadvancement:

• Occlusion of the left common carotid, vertebral or subclavian arteries.• Underadvancement:

• occlusion renal or mesenteric arteries• renders device less effective

• Aortic dissection• loss of definition of the descending thoracic aorta• lateral positioning of the catheter along the aorta

• Ballon rupture and air embolus (extremely rare)

IABP normal tip position IABP inflatedReference: Myrna C et al. Chest Radiography in the ICU: Part 2, Evaluation of Cardiovascular Lines and Other Devices. AJR 2012; 198:572–581.

CT of Left Ventricular Assist Devices

• CT provides noninvasive, high-resolution imaging of LVADs to identify normal and pathologic appearances

• Circulation:• Blood enters from the LV apex into the inflow

cannula• Transverses the pump• Exits through the outflow cannula to the aorta.

• Pump position:• Intra-abdominally• Preperitoneal pocket in the left upper quadrant

CT of Left Ventricular Assist Devices

• Indicators that LVAD is functioning normally to unload the LV:• Neutral septum position• Reduction in mitral regurgitation• Closed aortic valve during systole

• Normally positioned inflow cannula is directed into the LV without abutting any wall

CT of Left Ventricular Assist Devices – Acute Complications• Pericardial hematoma/tamponade

• high-attenuation fluid surrounding the heart• signs of tamponade include

• dilatation of the IVC• flattening of the heart border• compression of the RVOT, RA and coronary sinus

• Cannula obstruction/malposition can result from• kinked inflow or outflow cannula• LV hypertrophy• small or collapsed LVOT• deviated septum secondary to RV failure

CT of Left Ventricular Assist Devices – Chronic Complications• Thrombosis

• thrombus is seen as low-attenuation material within the LV• often adherent to the inflow cannula

• Aortic stenosis• Aortic fusion or stenosis from the continuous closure can result in stasis and

abnormal flow

• Aortic insufficiency• From increased transaortic valvular gradient and constant back-pressure• Can decrease effective forward outflow from the device

• Infection • Seen as gas or fluid collections around the driveline or the pump itself

CT technique for Imaging LVADs

• Retrospectively ECG-gated• morphologic and dynamic information of the aortic and mitral valves

throughout the cardiac cycle

• Contrast enhanced or noncontrast if just for positioning• Thin slices for MPR

Peri-Operative Cardiac Surgery Appearances

CT for Pre-operative CVS Planning

Re-operative cardiothoracic surgery:

• Relationship of cardiovascular structures to sternum

• Relationship of coronary bypass grafts to sternum

• Atherosclerotic calcification of the ascending aorta

• Anatomy of subclavian & axillary arteries and aortic arch

Relationship of cardiovascular structures to sternum

• Relationship of the following normal structures to the sternum:• Brachiocephalic vessels• Aorta• RV• Pericardium

• Assess for abnormalities in proximity to the sternum:• Chamber enlargement• Aneurysm• Pectus excavatum deformity• Adhesions from prior surgery/radiation

• Safe distance from the sternal midline: 10 mm (measured in relation to the closest sternal wire)

Relationship of coronary bypass grafts to sternum

• LIMA:• Often routed through a left pericardial slit (to prevent sternal adhesion)• May be medially displaced by adhesions

• RIMA:• Usually do cross the midline posterior to the sternum

• SVG:• Usually at a safe distance from the sternum• Can be displaced closer to the sternum by

• RV enlargement• Aortic aneurysm• Mediastinal adhesions

• High risk of injury: crossing the midline within 10 mm of the sternum

LIMA graft

Atherosclerotic calcification of ascending aorta

• Direct cannulation of the ascending aorta for cardiopulmonary bypass is contraindicated in the setting of extensive atherosclerotic calcification of the ascending aorta or “porcelain aorta” (risk of CVA)

Anatomy of subclavian & axillary arteries and aortic arch

• Axillary or subclavian arteries can be used as alternative sites for cannulation if the aorta is too heavily calcified

• Assess anatomy of these vessels• Variations (“bovine variant”, right arch, aberrant right SCA)• Atherosclerosis• Stenosis

CT technique for Pre-operative CVS Planning• Typically prospective ECG triggering• Reduced tube voltage (100 kV) and IR techniques to lower radiation

dose. • Non-contrast study can be performed

Imaging Post-Cardiac Surgery - Normal• Postoperative changes can persist for up to 2 weeks following surgery.

• Pre- and retro-sternal soft tissue inflammatory stranding/edema• Fluid/blood• Locules of air

• Sternal defect:• Gap of up to 4 mm• Step deformity• Impaction• Overlap of the fragments

• 50% show complete sternal union at 6 months and should be complete by 1 year

Imaging Post-Cardiac Surgery Complications - Mediastinal hematoma• Redo sternotomy for mediastinal hematoma is less than 4%• CT shows: high density fluid in the retrosternal space• Seen normally in the immediate peri-operative period but should not

increase in size or and attenuation

Imaging Post-Cardiac Surgery Complications -Pericardial effusions• Common but rarely associated with haemodynamic change• Usually taken back to OR if present within the first 2 h after surgery• Most diagnosed within 5 days postop (peak in 10 days) and should

resolve in 1 month• Echocardiography can miss posterior effusions and is operator-

dependent

Imaging Post-Cardiac Surgery Complications - Mediastinitis• Incidence less than 5% but approximately 1/3 mortality.• Clinical signs can be subtle• CXR findings are non-specific:

• mediastinal widening• Pneumomediastinum• accompanying sternal dehiscence (midternal stripe 3mm or below first sternal wire)• “wandering wire sign” (change in alignment of sternotomy wires from expanding fluid and abscess – can

lead to wire fracture)

• CT shows:• Loss of mediastinal fat planes• Diffuse soft-tissue infiltration• +/- gas • +/- focal fluid collections

• Assess depth and extent of infection for surgical debridement planning

Reference: Bhatnagar G et al., The role of multidetector computed tomography coronary angiography in imaging complications post-cardiac surgery. Clinical Radiology 2013; 68: e254-e265.

Mediastinitis

Imaging Post-Cardiac Surgery Complications -Constrictive pericarditis• Chronic inflammatory changes can result in constrictive pericarditis.• Complex diagnosis but CT can be helpful in showing associated

features:• Pericardial thickening ( normal 2 mm; > 4mm abnormal)• Pericardial calcification• bi-atrial/SVC/IVC enlargement• Compressed “cone shaped” ventricles

Imaging Post-Cardiac Surgery Complications - Sternum• Spectrum of sternal complications:

• Sternal dehiscence (acute; clinically identifiable)• Non-union• Osteomyelitis

• Cross sectional imaging not generally necessary unless the question is of infection

• mediastinitis• sternal osteomyelitis

• Imaging findings of non-union:• Displaced sternal wires• Non-union of the sternal incision edges• Increasing sternal gap

Imaging Post-Cardiac Surgery Complications – Prosthetic Valve Endocarditis (PVE)• Like echo, CT can show:

• Vegetations • irregular masses creating filling defect in contrast pool adherent to valve/endocardium

• Abscess• irregular, heterogeneous “mass-like” paravalvular/peri-annular attenuation

• Pseudoaneurysm • contrast medium-filled focus communicating with chambers or root

• Fistula • contrast filled continuation between left and right chambers

• Valvular dehiscence• retrospective study: rocking motion of prosthetic valve with excursion of 15 degrees

• CT can also show: • Extra-cardiac disease (e.g. septic emboli in the lungs)• Coronary artery disease

Objectives

• At the end of this session, participants will be able to:

• Recognize cardiac devices on imaging and assess for their related complications.

• Identify cardiac surgery preoperative planning concerns and postoperative complications on imaging.

• Manage the technological aspects of imaging cardiac devices and peri-operative issues in cardiac surgery patients.

Thank-youQuestions?

Useful References

1. Mak G and Truong Q. Cardiac CT: Imaging of and Through Cardiac Devices. Curr Cardiovasc Imaging Rep 2012; 5:328–336.

2. Myrna C et al. Chest Radiography in the ICU: Part 2, Evaluation of Cardiovascular Lines and Other Devices. AJR 2012; 198:572–581.

3. Aguilera A, et al. Radiography of Cardiac Conduction Devices: A Comprehensive Review. RadioGraphics 2011; 31:1669–1682.

4. Rajiah P andSchoenhagen P. The role of computed tomography in pre-procedural planning of cardiovascular surgery and intervention. Insights Imaging. 2013; 4:671–689.

5. Bhatnagar G et al., The role of multidetector computed tomography coronary angiography in imaging complications post-cardiac surgery. Clinical Radiology 2013; 68: e254-e265.

6. Christensen J et al. Imaging of Complications of Thoracic and Cardiovascular Surgery. Radiol Clin N Am. 2014; 52: 929–959.