Thrombus and Embolic Events

What is the difference between a thrombus and an embolus

thrombus is a blood clot attached to a vessel wall

embolus is a free floating clot

Conditions which increase likelihood of thrombus?

1. there is stasis (low-flow of blood)

2. there is a substrate

3. there is hypercoagubility of blood (more likely to clot)

What is the triad for causes of vascular thrombosis called ? What are the categories?

Virchow’s triad:

1. Stasis

2. Vessel wall damage

3. Hypercoagulation

Echo sign of stasis of blood

Spontaneous echo contrast

What does Spontaenous echo contrast mean in terms of risk?

• increased likelihood of thrombus formation

What causes spontaneous echo contrast? What can exacerbate it

usually happens in AF, abnormal pump function of LA causes slower moving blood

exacerbated in AF with MS

List all the substrates for a thrombus?

• RWMAs

• Akinetic apex: apical thrombi

• Aneurysmal LV region

• Akinetic LV region

• LAA: MS, MR, AF?

• RA: L to R shunting?

• Intracardiac devices: valve replacements, pacing leads (RA and RV), intravascular catheter, LV assist device, ASD occluder device (Amplatzer)

What increases chances of LA thrombus?

• AF (loss of normal atrial contraction)

• MS:

What in the LA / LAA can be mistaken for a thrombus?

pectinate muscles

In a patient with AF, MS and an echogenic mass in the LA, what is the likelihood this is a thrombus?

high

What can cause right heart thrombus?

• conditions + pacing / defibrillator leads/ intravacular catheter

• thromboembolism in peripheral veins (i.e DVT) in transit to pulmonary system

Are right heart thrombi usually formed in the right heart?

can be but this is rare

more often formed in the peripheral veins and travel back to right heart

What typically causes LV thrombus

1. Akinetic walls

2. Aneurysmal walls

3. Valve replacement

Name the different types of thrombus?

• mural

• laminated

How does thrombus usually attach to myocardium?

• broad base attachment rather than via a stalk (perdunculated)

Medicines to prevent thrombus?

anticoagulants

• Apixiban, rivaroxiban, dabigatran, edoxaban

• Warfarin

• Occasionally aspirin which is a blood thinner but not 1st line anticoagulant

Medicines to break down an existing thrombus?

thrombolytic drugs that induce fibrinolysis

What are the risks associated with a thrombus?

• thrombus can dislodge/ detach from wall and become embolus

• Embolic event

• pulmonary embolism

• brain aneurysm: Stroke

Terrible image quality but what can be seen in the PA bifucraction?

Saddle shaped embolus

Likely an acute pulmonary embolism

After seeing this, what other echo features to check for?

• RV free wall: look for McConnell’s sign (akinesis with apical sparing) and 60/60 sign: PAT <60 ms and RVSP <60 mmHg

What is the echogenicity of thrombus like?

different to myocardium/ darker but change based on age. Older can look brighter due to calcification.

Thrombus vs a tumour: how can we tell the difference?

• echogenicity: tumour should have similar echogenicity to myocardium/ liver (speckled parenchyma appearance)

• attachment: perdunculated or broad base?

• ask yourself: are there the conditions for a thrombus ? Stasis/ substrate/ hypercoagubility

What is the best ultrasound imaging technique for LA or LAA thrombus?

• TOE due to reduced distance from the LAA (higher temporal resolution, and spatial res (sharpness) because higher frequencies can be used because penetration is less)

What is the best ultrasound imaging technique for LV thrombus?

• TTE because this is closer to LV than TOE would be (particularly the apex which is a major site of thrombi)