Anatomical Variants and Masses

RIght atrium

• Crista terminalis - Located between the SVC and RA. Can be a useful identifier to locate sinus venosus ASD's from other secundum ASD types. (sinus venosus is cephalad of the crista terminalis whereas secundum ASD is caudad of the crista terminalis)
• Eustachian Valve - A embryological remnant used to direct oxygenated blood from the mother out of the IVC across the fossa ovalis to the LA. Normally regresses after birth. Forms a thickened ridge between the RA and IVC that can be mistaken for thrombus.
• Thebesian Valve - Forms a valve where the CS enters the RA and may serve to prevent retrograde flow into the CS during RA contraction. Can be present or absent and may have no role. Can make cannulation with retrograde cardioplegia cannula difficult. Has a characteristic "serpentine" appearance and wobbles around in the RA.
• Chiari Network - Mobile net-like series of membranes around the IVC and CS of no clinical significance. Increased risk of thrombi and atrial arrhtyhmias. Can also trap devices and lines.
• Right atrial appendage - Located in the anterior / medial portion of the RA. Becomes dilated with tricuspid stenosis or severe TR. Can be a site of arrhythmias and require ablation.
• Pectinate muscles - "teeth of a comb" appearance of the RA and sometimes LA due to muscular trabeculations which are normal variants. Genersally extend out from the RAA
• Cortriatrum Dexter - membrane crossing the entire width of the RA. Much rarer than cortriatrium sinister seen in the LA. Need to differentiate from a eustachian valve (should e obvious as the membrane is across the entire RA with cortriatriatum dexter)
• Persistent left SVC - Evidenced by a dilated CS and can be diagnosed by injecting contrast into the left upper limb and it enters the CS before the RA. Associate with ASD's. Overall incidence 0.5% but up to 10% of patients with other congenital abnormalities.
• IAS Aneurysm - Diagnostic = >15mm in width. Associated with PFO (50-89%) and cerebral emboli
• Lipomatous hypertrophy of the IAS - Benign condition with an echobright "dumbell" appearance. Essentially fatty infiltration into the IAS with sparing of the fossa ovalis. The uppermost accumulation at the top of the atrium is found in "Waterston's Groove".
• Right atrial appendage - Seen in MO-bicaval view or modified bicaval TV view. May see pectinate muscle within the RAA or extending outwards. Rarely a site for thrombus.
• Coronary sinus - normally < 1cm. If enlarged be suspicious for a persistent left SVC or aberrant pulmonary vein draining into the RA.

Left atrium

• Warfarin (Coumadin) ridge (aka ligament of Marshall) - Tissue between the LAA and the LUPV which is normal (patients get started on warfarin as it is thought to be abnormal) Can have a thin, membranous proximal section and then a more bulbous distal section.
• Cortriatriatum sinister - membrane crossing the whole LA. Caused by a failure of the PV remnants to resorb during embryogenesis. More common than cortriatriatum dexter which affects the RA. MS-type physiology is seen with restricted flow across the membrane from the dorsal (upper) to the ventral (lower) chambers. Associated with:
• Pulmonary venous inflow abnormalities
• ASD
• Persistent left SVC
• MR
• Native LA (post heart Tx)
• Left atrial appendage - site for clot, if PWD velocity >50cm/sec this is unlikely. Best imaged with 3D. May be multi-lobe.
• LAA membrane - May occlude the entrance to the LAA.

Atrial Septum

• Double membrane from fossa ovalis
• Lipomatous hypertrophy of the interatrial septum - dumbbell appearance sparing the fossa ovalis, can be quite pronounced like an alien's head!
• Tumour infiltration (Hodgkins lymphoma)
• Atrial septum aneurysm (ASA) - Seen in 1% of patients and defined as excursion of >15mm into either atrium with excessive septal movement. 50% association with PFO and associated with increased risk of stroke and paradoxical emboli.
• ASD (see congenital section)
• Primum
• Secundum
• Sinus venosus

Right ventricle

• Trabeculae = normal. Increased prominence with RVH
• Moderator band = allows for synchronous contraction of the anterior papillary muscle of the RV and appears as a prominent trabecula. Connects the septum to the anterior papillary acting as a "shortcut" for electrical conduction thereby improving contraction. A portion of the RBB.

• Crista superventricularis = separates the RV from the conus or RV outlet

Left ventricle

• Trabeculae - Can conceal a muscular VSD from the surgeon. Most common apically.
• False tendons
• Lobular / bifid papillary muscles
• Valvular strands (Lambl's excresences - <10mm)

Transverse sinus

• Can be seen at 90 degrees in the high MO view
• Right PA [1], underneath is transverse sinus [2] , underneath this is then the aorta in long axis [3]
• Generally only seen if there is a small pericardial effusion adjacent to the aorta in the MO-views.

Oblique sinus

• Cannot be seen with TEE unless filled with fluid (common site for accumulation after cardiac surgery)
• Space located between the pulmonary veins and the LA
• May be seen in the near-field around the LA and the oesophagus

Intra-cardiac Masses

Thrombi

• Generally grey in appearance with highly variable appearances otherwise
• LV thrombi tend to be seen in the apex (easily missed in MO5C view as apex lies in the far field, use MO2C instead)
• Associated with RWMA and SEC
• Broad-based thrombi with attachment to the myocardium = "mural thrombus"

• LA thrombus = generally located in the LAA
• Associated with SEC, slow flow and dilated LA (typical of MS)

• RA = tend to be seen in the RAA and associated with elevated RAP.
• May also be evident as a "thrombus in transit" from elsewhere

Vegetations

• Abnormal growths containing platelets, fibrin and infected material. Overall sensitivity for TTE is 50-70% therefore TOE recommended if high clinical suspicion (85% sensitivity)
• Most likely found on valves but also foregin material (wires), septal defects or alongside other congenital abnormalities.
• MV and AV more frequently affected than the TV. (IVDU increases risk of right sided endocarditis)
• 2D underestimates size (3D can give a more accurate assessment)
• Risk of embolisation increases with size (>1.6cm in one study showed higher risk of embolisation)
• On prosthetic valves, dehiscence of the sewing ring = paravalvular regurgitation (may develop a rocking motion to the valve)
• Associated with valvular incompetence (regurgitation), perforations, abscesses and fistuale
• Differentials = fibroelastoma, degenerative changes, valve strands, thrombi, old burnt-out vegetations. Thrombi are the most similar in terms of echogenicity.
• Abscesses = More likely on prosthetic valves. Be suspicious if non-resolving clinical picture or an invasive microorganism is causative e.g. S.Aureus. Heart block can be a feature is abscess invades into the IVS.

Primary - Benign Tumours (75%)

Myxoma (50% of benign tumours)

• Affects ages 30-60yrs with females > males
• Very unlikely to be found on a valve
• 75-90% in the LA, 5-20% in the RA
• Most likely seen in the LA, LAA or warfarin ridge. Can prolapse through the MV causing MS-type symptoms
• Myxoma most commonly found on the LA side of the fossa ovalis (Insert into the IAS)
• Often attached to the fossa ovalis (Can be missed on CT/MRI)
• Appearance = "Grape cluster" with associated fronds. Generally attached via a stalk. Normally smooth walled and polypoid in structure.
• High thromboembolic potential (and should therefore be excised)
• Rarely multiple or located in the ventricles.

Fibroelastoma

Second-most common cardiac tumour (after myxoma)

• Histologically benign but can cause embolic stroke
• Occur on valves, normally on the downstream side. Don't normally cause valvular incompetence
• Mimic the appearances of vegetations and Lambl's excresences
• AV & MV > TV & PV
• 99% are <20mm with most <10mm
• Often attached via a mobile stalk

Lipomas / fibrolipomas

• Can be found anywhere in the heart but usually superficial in the pericardium
• Benign adipocyte tumours
• Rhabdomyomas = most common tumour-type in children

Primary Malignant Tumours (25%)

Sarcoma

• 95% of the malignant cardiac tumours
• Angiosarcoma = most common (40%) , poor prognosis (3 months-1 year) Generally seen in the RA
• Rhabdomyosarcoma = Less common. Seen in the ventricular walls and encountered in paediatric population, often with a poor prognosis.

May present as an incidental finding, embolic stroke, arrhythmia, SOB, chest pain or pericardial effusion.

Management

• Resection but recurrence is very common. Complete resection doubles life expectancy
• Radiotherapy (palliative)

Secondary Tumours

Metastases

• The most commonly encountered tumour in the heart. Pericardium is more likely to be affected than the myocardium or heart itself.
• CA most likely to be secondary to melanoma (50% of patients with mets) or lung cancer.
• Renal cell carcinoma = most likely to metastasise to the vena cavae
• Breast, ovarian, lymphoma, leukaemia and oesophageal CA can all also metastasise.

Aortic Valve

Lambl's excresences = filamentous attachments to the AV cusps. (Normal variant)

Fibroelastomas

• Bulbous benign growths which are associated with thromboembolic events (see below)
• Mimic vegetations but more pedunculated
• Seen on valvular structures (but DON"T tend to cause insufficiency)
• Seen on the DOWNSTREAM (high pressure) side of the valve (vegetations tend to be on the opposite low pressure side)
• Most likely at AV and MV but have been found on PV and TV
• Tend to be small
• Often have a mobile stalk