13: Pulmonary HT & Thromboembolic Dz

Vascular pressure within the lungs and why

Low pressure system; we want lots of easy blood flow through the lungs

T/F: the lungs hold a large blood volume

True

Structural characteristic of alveoli that allow for gas exchange

Very thin walls

Definition of pulmonary hypertension

Systolic pressure >25 mmHg

How much of the vascular bed needs to be lost for pulmonary HT to develop

65%

Three general causes of pulmonary HT

• Increased pulmonary blood flow

• Increased pulmonary vascular resistance

• Pulmonary venous congestion

Causes of increased pulmonary blood flow

PDA, V/ASD

Causes of increased pulmonary vascular resistance

Chronic lung disease and chronic hypoxia

Causes of pulmonary venous congestion

Classic MMVD, other chronic L sided heart disease

Primary pathophysiology of pulmonary HT

Thicker, inflamed walls

Demographic that is highly likely to have pulmonary HT from chronic hypoxia

Brachycephalics

T/F: PHT is rare in cats

Maybe, but could be that we are just overlooking it

History associated with PHT

• Coughing (common!)

• Syncope/collapse

• Dyspnea

• Exercise intolerance

DDx for “seizures” alleged by owner

Syncope and collapse

Things to evaluate to differentiate seizure and syncope

• What was happening before

• How did they look waking up

• Limb movement

• Foaming/chattering

CS associated with PHT

Nonspecific

• Tachypnea and dyspnea

• Weakness

• R CHF

• ± Tachycardia, cyanosis, crackles, murmur

T/F: true, primary PHT will present with a murmur

Not usually

Radiographic findings consistent with acute PHT

Normal rads :)

Radiographic findings consistent with chronic PHT

• Dilated MPA

• Dilated cr/cd lobar arteries

• R sided enlargement

Where is the MPA on a VD radiograph

1-2 o’clock

Indirect measurement of pulmonary pressure that we can do via echo

Measure the velocity of blood across the pulmonic valve or tricuspid valve

If there are clots in the lungs, what WILL happen

Fluid build up

Best test we can do to evaluate clotting activity

Thromboelastography

Why is thromboelastography (and other viscoelastic testing) so great

It measures all aspects of the clotting cascade: platelets, clotting factors, fibrinolysis, etc.

Meds to consider if a patient is hypercoagulable

Antiplatelet and anticoagulant drugs

THE treatment for PHT

O₂

How quickly do PHT patients respond to O₂

Fast, may look much better after 30-60 minutes

Go-to meds for managing PHT

Sildenafil ± pimobendan

When might we use diuretics for PHT

If there is severe cavitary fluid accumulation

When might we really not want to give diuretics for PHT

If there is R CHF

Why do we like IVF for PHT

Helps the R heart overcome the pressure in the lungs and move blood into the LV

When can you wean a PHT patient off of O₂

When they are breathing normally at room air

T/F: PHT is an acute disease

F, it is chronic and progressive

Chronic management for PHT

• Manage L sided heart disease

• Sildenafil ± pimobendan

• ± Antiplatelet drugs

• Avoid physical stress

At-home monitoring for PHT

• RR/RE

• Log syncopal episodes

• HW prevention

• BP

Elements of virchow’s triad

• Endothelial injury

• Hypercoagulability

• Turbulent blood flow

Thrombus v embolus

Thrombus is an initial clot in the heart or an artery, an embolus is a piece of the clot that breaks off and lodges somewhere else

The most common cause of clots in cats

Heart disease

The most common cause of clots in dogs

Lots of things

Types of shock caused by thromboembolic disease

Obstructive ± cardiogenic shock

How do clots cause damage

Mechanical obstruction of an artery → tissue ischemia

Clots are the number one complication of which immune mediated disease

IMHA

5 P’s of feline aortic thromboembolism (FATE)

• Pain

• Paralysis

• Pulselessness

• Poikilothermy

• Pallor

The best way to diagnose thromboembolic disease

CT angiogram

More accessible ways to diagnose thromboembolic disease

• Paired glucose and lactate

• Ultrasound

• Viscoelastic testing

Treatment for thromboembolic disease

• Pain meds

• Clopidogrel

• Anticoagulant drugs

• Nursing care

T/F: surgery can increase survival rates for thromboembolic disease

Nope

Common complication of trying to treat thromboembolic disease

Reperfusion injury

Reperfusion injury

Sudden uptick in toxins and K⁺ from damaged/dead cells

Clinical manifestations of reperfusion injury

• Hyperkalemia → bradycardia

• Severe metabolic acidosis

• AKI

• Death