EP 140: Pulmonary Hypertension 101

Pulmonary hypertension is a type of high blood pressure that affects the arteries in the lungs and the right side of the heart resulting in increased pulmonary vascular resistance and pulmonary arterial pressures [1].

Diagnosis

Pulmonary arterial hypertension is diagnosed with a right heart catheterization or Swan–Ganz catheter showing pulmonary arterial mean pressure greater than 25 mm Hg and not by echocardiogram.

Normal pulmonary artery pressure is 15-25/8-15
A normal mean pulmonary artery pressure: 10-20
Normal pulmonary artery wedge pressure: 6-12
A normal CVP: 2-6
Normal CO: 4-8
A normal SVR: 700-1500

Causes

The typical heart has two upper chambers (atria) and two lower chambers (ventricles). Each time blood passes through the heart, the lower right chamber (right ventricle). It then pumps blood to the lungs through a large blood vessel (pulmonary artery).

In the lungs, the blood releases carbon dioxide and picks up oxygen. The blood flows through vessels in the lungs (pulmonary arteries, capillaries, and veins). It then goes to the left side of the heart.

Changes in the cells that line the pulmonary arteries affect the wall of the arteries. They become stiff, swollen, and thick. These changes may slow down or block blood flow. It blocks the flow of blood through the lungs, causing pulmonary hypertension.

The right ventricle spends little time in isovolumic contraction or relaxation. As a result, is able to generate cardiac output with only a fifth of the energy demanded by the left ventricle (LV).

Left-sided heart failure can cause pulmonary hypertension.
Pulmonary hypertension can cause right-sided heart failure.

Groups of Pulmonary Hypertension

This condition is divided into 5 groups by the World Health Organization

WHO group	Etiology of pulmonary hypertension	Mean pulmonary arterial wedge pressure	Example causes
1	Pulmonary arterial hypertension	Normal	Idiopathic, hereditary, drug or toxin-induced, shunts related to congenital heart disease, connective tissue disease, portal hypertension, chronic hemolytic anemia, Collagen Vascular Diseases
2	Pulmonary hypertension secondary to left heart disease	Increased	Valvular heart disease, systolic dysfunction, diastolic dysfunction, pericardial disease, congenital/acquired left heart inflow/outflow tract obstruction, congenital cardiomyopathies
3	Pulmonary hypertension secondary to lung disease	Normal	Chronic obstructive pulmonary disease, severe asthma, interstitial lung disease, sleep apnea, long term exposure to high altitude, congenital lung abnormalities
4	Chronic thromboembolic pulmonary hypertension (CTEPH)	Normal	Chronic pulmonary embolism
5	Pulmonary hypertension with unclear and/or multifactorial mechanisms	Normal or increased	Systemic diseases, sarcoidosis, vasculitis, hematological malignancies, chronic renal failure, metabolic disorders, lung tumors

Group 1: Pulmonary arterial hypertension (PAH)

Causes include:

Unknown cause (idiopathic pulmonary arterial hypertension)
Changes in a gene passed down through families (heritable pulmonary arterial hypertension)
Use of some prescription diet drugs or illegal drugs, such as meth
Heart problems present at birth (congenital heart disease)
Other conditions such as HIV infection, chronic liver disease (cirrhosis)
Collagen Vascular Diseases – Diseases such as R.A & Lupus. Inflammation is probably an important contributor to the development of pulmonary hypertension. Clustering of macrophages and T‐lymphocytes around vascular lesions has been reported in PPH and associated with this condition and has been linked to vascular remodeling [1].

Potential causes of PAH based on pathophysiology: Endothelial dysfunction, impaired vascular dilatation, alterations in the expression of NO, ET1 and serotonin, increased expression of inflammatory cytokines and chemokines, loss of endothelial caveolin-1, and disordered proteolysis of extracellular matrix contribute to the pathogenesis of PAH.

Definition of Proteolysis – The breakdown of proteins or peptides into amino acids by the action of enzymes.

Group 2: Pulmonary hypertension caused by left-sided heart disease

Causes include:

Left-sided heart valve diseases such as a mitral valve or aortic valve disease
Failure of the lower left heart chamber (left ventricle)
- In response to a massive increase in left-sided filling pressures, more specifically left atrial pressure

Group 3: Caused by lung disease

Causes include:

Chronic obstructive pulmonary disease (COPD)
Scarring of the tissue between the lung’s air sacs (pulmonary fibrosis)
Obstructive sleep apnea
Long-term exposure to high altitudes in people who may be at higher risk of pulmonary hypertension

Sleep apnea causes PAH due to left heart dysfunction with either preserved or diminished ejection fraction. The combination of hypoxic pulmonary vasoconstriction and pulmonary venous hypertension with abnormal production of mediators will result in vascular cell proliferation and aberrant vascular remodeling leading to pulmonary hypertension.

Pulmonary vascular remodeling in COPD is the main cause of the increase in pulmonary artery pressure and is thought to result from the combined effects of hypoxia, inflammation, and loss of capillaries in severe emphysema.

Group 4: Caused by chronic blood clots

Causes include:

Chronic blood clots in the lungs (pulmonary emboli)
Other clotting disorders

Group 5: Pulmonary hypertension triggered by other health conditions

Causes include:

Blood disorders, including polycythemia vera and essential thrombocythemia
Inflammatory disorders such as sarcoidosis and vasculitis
Metabolic disorders, including glycogen storage disease
Kidney disease
Tumors pressing against pulmonary arteries

Signs:

Heart sounds: Loud P2 (Closing of the Pulmonic value, Murmur of tricuspid regurgitation
The liver will be pulsatile
EKG – Right Ventricular Deviation (RVH)
- Lead 2 peaked P-wave
- V1 – Large V wave and maybe an RBBB
Echo – This device would measure the change of pressure “Velocity” Measuring the absolute pressure of the Right atrium and the right ventricle. Would also measure the Size of the Right Atrium and Ventricle.

Complications

Potential complications of pulmonary hypertension include:

Right-sided heart enlargement and heart failure (cor pulmonale). In cor pulmonale, the heart’s right ventricle becomes enlarged and has to pump harder than usual to move blood through narrowed or blocked pulmonary arteries.
- As a result, the heart walls thicken and the right ventricle expands to increase the amount of blood it can hold. But these changes create more strain on the heart, and eventually, the right ventricle fails.
Blood clots. Having this kind of hypertension increases the risk of blood clots in the small arteries in the lungs.
Arrhythmia can cause irregular heartbeats (arrhythmias), which can lead to a pounding heartbeat (palpitations), dizziness, or fainting. Certain arrhythmias can be life-threatening.
Bleeding in the lungs can lead to life-threatening bleeding of the lungs and coughing up blood (hemoptysis).

Pathophysiology of PAH and RVF

In order to reduce wall tension caused by the increased afterload of PHTN, hypertrophy of the right ventricle occurs. As a result, coronary flow no longer occurs in diastole despite the increased demand of the hypertrophied right ventricle.
The right ventricle spends more time in isovolumic contraction and relaxation to overcome increased pulmonary pressures, reducing right heart output and greater energy demand.
RV hypertrophy also interferes with the normal motion of the tricuspid valve and increases pulmonary pressures resulting in tricuspid regurgitation. The growth of the right ventricle also impedes the function of the LV as the interventricular septum bulges into the LV.
These changes in the right ventricle all reduce cardiac output, decrease coronary flow to the RV, and causes ischemic damage. Finally, this hypertrophy of the right ventricle, accompanied by ischemic damage, eventually leads to ventricular dilatation and total right heart failure.

Fun Fact:

Patients with PHTN are at risk for developing sepsis. Patients with low cardiac output may poorly perfuse the bowel, leading to a leaky endothelial barrier that allows bacteria and their toxins to invade, which can result in sepsis.

The effects of sepsis on patients with PHTN can be devastating. Sepsis-induced drops in systemic vascular resistance (SVR) can severely compromise patients with reduced cardiac output from PHTN.

Sepsis has been shown to cause pulmonary vasoconstriction and dysfunction and produce cytokines that reduce right heart contractility.

Clinically, sepsis was found to be a leading cause of patient mortality in the ICU for patients with PHTN exacerbations [2].

Interventions

Pulmonary vasodilators are used to reduce RV afterload by reducing pulmonary arterial pressures. Vasodilators are effective at reducing RV afterloads, such as IV Prostanoids, Inhaled Nitric oxide cause improvements in cardiac output and oxygenation.
- Outpatient we can use Sildenafil to cause an increase in nitric oxide that will vasodilate.

Inotropes, such as Dobutamine and Milrinone are used to maintain cardiac output in the presence of cardiogenic shock from right heart failure due to this hypertension.
Pressure support medications, such as norepinephrine and vasopressin, should be used to maintain systemic blood pressure as well as right coronary artery perfusion of the right ventricle.
We also can Diuresis these patients to reduce the pressure of fluid overload on a failing right ventricle.
Intubation of patients with PHTN and RVF should be avoided as sedatives can depress cardiac function and lower SVR, and increased transpulmonary pressures can further lower CO.
For patients with end-stage PAH and RVF refractory to optimized medical treatment, lung transplantation with bridging via extracorporeal life support should be considered.
Anticoagulation was found beneficial in groups 1 and 4 based on autopsies that there are a lot of blood clots.
For stage 4 PAH, like we saw during COVID, we refer to a drug called Epoprostenol. Stimulates the Prostacyclin receptor (agonists) and causes Vasodilation.

TIMESTAMPS:

0:00 Cup of Nurses Intro
0:54 Sponsor Ads
1:32 Cup of Nurses Introduction
3:23 Pulmonary Hypertension
6:16 Pulmonary Arterial Hypertension Diagnosis
10:25 Groups of pulmonary hypertension
10:38 Pulmonary arterial hypertension Causes
11:58 Pulmonary hypertension secondary to left heart disease
12:36 Pulmonary hypertension secondary to lung disease
16:20 Pulmonary hypertension caused by chronic blood clots
19:18 Pulmonary hypertension triggered by other health conditions
19:54 Signs of Pulmonary Hypertension
22:44 Complications of Pulmonary Hypertension
25:38 Fun Facts