10.2 ICE, Intravascular Imaging & Endomyocardial Biopsy

ICE, Intravascular Imaging & Endomyocardial Biopsy

Chapter 8 covered boxes and physics (ultrasound versus near-infrared light, whether blood must be flushed). Procedures additional diagnostic imaging asks a different question: what decision does this catheter change, and what can it break? Typical numeric cutoffs below are clinical teaching thresholds, not unpublished ARRT law.

Quick Answer: ICE in the right atrium guides transseptal puncture, ASD/PFO, LAA, TAVR, and EP. IVUS is for ambiguous left main, stent underexpansion, and MLA — a common teaching LM MLA is about 6 mm², labeled as teaching, not ARRT law. OCT is for calcium, dissection, malapposition, and thrombus. Endomyocardial biopsy samples the RV septum from IJ or femoral venous access for transplant rejection or unexplained cardiomyopathy; the feared complications are tamponade, tricuspid damage, and conduction block.

ICE: what the image is for

Intracardiac echocardiography (ICE) is an ultrasound catheter, most often advanced from a femoral vein (internal jugular is an alternative) into the right atrium. It does not require a blood-free field. It is not TEE (esophagus) and not IVUS (coronary lumen).

Transseptal puncture. This is the ICE use the exam loves. From the RA you see the fossa ovalis. As the needle and sheath tent the septum, ICE shows whether you are aiming at the fossa and not at the aortic root (too anterior) or the posterior atrial wall. After puncture, ICE confirms a catheter in the left atrium (chamber, not aorta) and watches for pericardial effusion if the needle went the wrong way. Tenting that points at the aorta is a stop, not a push.

ASD and PFO. ICE shows defect size, rims, and color-Doppler shunt. During closure it shows device disc seating on each side of the septum and residual leak. A PFO tunnel versus a true ASD changes device choice — that is physician language, but the technologist’s job is a stable ICE view of the septum, not a random RA cavity shot.

Left atrial appendage (LAA). ICE (sometimes with TEE) maps the ostium and landing zone and looks for peri-device leak after occlusion. Thrombus in the LAA is a reason not to proceed with closure that day.

TAVR. ICE can show the aortic valve, wire position in the LV, new AR / paravalvular leak, and a sudden effusion if a wire perforates. It is adjunctive; CT and aortography still own pre-implant anatomy.

Electrophysiology. ICE guides transseptal access for left-atrial ablation, shows catheter–tissue contact on the septum or pulmonary-vein antra at a teaching level, and looks for thrombus or effusion during a long left-sided case.

ICE complications are vascular (venous access), arrhythmia from catheter irritation, and rare perforation — still safer on the esophageal-injury axis than TEE, which is why labs reach for it.

IVUS: the questions angiography cannot answer

Intravascular ultrasound stays useful in a blood-filled lumen. Procedurally you care about three CI questions.

Ambiguous left main. A 50% LM on angiography is a coin toss in one view. IVUS pullback from distal LAD or LCx through the LM to the aorta measures minimum lumen area (MLA) at the tightest LM segment and shows whether plaque is ostial, shaft, or distal-bifurcation. A commonly cited teaching threshold is LM MLA about 6 mm² (some series discuss values near 5.9–6 mm²). That number is clinical teaching used in labs, not an ARRT-published cutoff and not a scored-item law. Non-LM proximal-vessel MLA teaching numbers are even less standardized on this exam — do not invent a universal 4 mm² as ARRT fact. Report the measurement; the operator applies the threshold.

Stent underexpansion. Angiography can look fine while the stent minimum area is far below the reference vessel. Underexpansion is the IVUS finding most tightly tied to later thrombosis and restenosis. The treatment is usually a larger or higher-pressure balloon, not another stent length. Malapposition (struts standing off the wall) is a different IVUS/OCT diagnosis from underexpansion (stent too small for the vessel).

MLA and plaque elsewhere. IVUS still grades lumen area, plaque burden, and calcium with acoustic shadowing when OCT flush is undesirable (low eGFR, inability to displace blood).

Safety during the run: ischemia from the bulky catheter, spasm, dissection if forced, and never power-injecting an LV-gram recipe through an IVUS lumen that is not rated for it.

OCT: when you need the finer picture

Optical coherence tomography still needs a contrast or saline flush so red cells do not scatter the near-infrared light. You choose it when the clinical question is surface and strut detail, not depth to the adventitia.

• Calcium: sharply bordered, signal-poor. Arc, thickness, and length on OCT tell the operator whether balloon dilatation alone will fail and whether atherectomy or intravascular lithotripsy is the next tool. Depth numbers used in calcium-modification papers are teaching, not ARRT cutoffs.
• Dissection: an intimal flap, a cavity behind the intima, intramural hematoma — often invisible or underestimated on angiography after a balloon or a calcium crack.
• Malapposition: blood between strut and wall; OCT resolves strut-level gaps better than IVUS.
• Thrombus: irregular, protruding, high-backscatter material that angiography may call “hazy.”

OCT is a poor choice when you cannot afford the flush, when you need deep vessel remodeling (external elastic membrane), or when the vessel is too large for the light to reach the wall after a flush. That is when IVUS stays in the room.

Endomyocardial biopsy

Endomyocardial biopsy is a tissue diagnosis, not an angiogram. The usual target is the right-ventricular septum, approached from internal jugular (straight shot) or femoral venous access with a longer bioptome.

Indications. Cardiac-transplant rejection surveillance (serial biopsies) and unexplained cardiomyopathy (suspected myocarditis or infiltrative disease) are the two stems the exam uses. This is not a routine tool for every low EF.

How the pictures keep you on the septum. Under fluoroscopy, LAO helps separate septum from RV free wall; RAO shows long-axis position. Jaws open in the cavity, the bioptome is seated on septum, jaws close, then a controlled pull. Several samples from slightly different septal sites. RV free-wall bites are how you perforate.

Complications.

• Perforation → tamponade: hypotension, equalization of diastoles, effusion on ICE or echo. This is an emergency — volume, reversal of anticoagulation as directed, and drainage — not “one more sample.”
• Tricuspid damage: chordae or papillary apparatus in the bite → new or worse TR.
• Conduction block: the RV septum is near the right bundle; RBBB is common and often transient; higher-grade block is the feared version.
• Access-site bleeding, arrhythmia from mechanical irritation.

Left-ventricular biopsy exists in specialist practice; it is not the default CI teaching path, and “radial arterial LV free-wall biopsy because tamponade cannot happen on the left” is a distractor — left-sided perforation is still tamponade.

Tool / question it answers / main risk

LM MLA ~6 mm² belongs in the IVUS row as teaching, not as an ARRT-printed law.

Worked case

Planned LAA occlusion. ICE from the femoral vein sits in the RA and shows clean fossa tenting away from the aorta; transseptal puncture is completed. The same ICE view rules out LAA thrombus and later checks peri-device leak. Separately, an intermediate LM on angiography is not a biopsy indication. Pull IVUS from mid-LAD through the LM: MLA is 5.2 mm². Using the common teaching threshold near 6 mm² (again: teaching, not ARRT law), the operator treats the LM as significant and stents it. Post-stent angiography looks adequate; IVUS shows underexpansion, so a higher-pressure balloon is used. If the question had been an edge dissection versus calcium after a balloon, OCT with a flush would be the finer tool. If the next patient is a transplant recipient for routine rejection surveillance, that is RV septal biopsy from the IJ — not ICE in the coronary and not an LV free-wall bite.

Exam traps

• Putting ICE in the esophagus (TEE) or in a coronary (IVUS/OCT).
• Treating LM MLA ~6 mm² as an ARRT-published scored cutoff rather than common clinical teaching.
• Using OCT without a blood-clearing flush, or IVUS as if it needed one.
• Calling stent underexpansion the same thing as malapposition.
• Default LV free-wall biopsy, or forgetting tamponade, TR, and conduction block as biopsy complications.
• Using biopsy to “grade” an intermediate coronary stenosis.