The primary causes of secondary pulmonary hypertension are existing medical conditions—most commonly left-sided heart disease or chronic lung issues—that force high pressure to build up in the arteries of your lungs. Unlike "primary" hypertension which starts in the lungs themselves, this secondary type is a reaction to something else going wrong in your body, such as a weak heart pump, blocked airways, or even sleep disorders.
Let me take a moment to be real with you. I’ve spent years in cardiology clinics, and the story I hear most often usually starts the same way. A patient—let’s call her Maria—comes in looking exhausted. She tells me, "Doctor, I used to walk up the stairs to my apartment with groceries in both hands. Now, I have to stop twice just to catch my breath." Maria was scared because she thought her lungs were failing. But after we ran some tests, we found out her lungs were actually victims of a different crime: a stiff heart valve.
It’s a scary moment when you realize your body isn't keeping up with you. That feeling of "air hunger" is terrifying. But here is the good news: in my experience, understanding the "why" is the first step to fixing the "how." Secondary pulmonary hypertension isn't a mystery disease that comes out of nowhere. It is almost always a signal, a red flag waving to tell us that another organ needs help. Whether you are in New York, London, or Tokyo, the biology is the same. When we treat the root cause—that underlying heart or lung issue—we often see the pressure go down and the breathing get easier.
I wrote this guide to help you make sense of the medical jargon. We are going to skip the complex textbook definitions and talk about what is actually happening inside your chest, plain and simple. We will look at the twelve most common culprits, how they disrupt your circulation, and most importantly, what you can do about it starting today.
What You Will Learn
- 1. The "Backup" from Left-Sided Heart Disease
- 2. COPD and Emphysema: The Airway Blockers
- 3. Sleep Apnea’s Silent Nighttime Damage
- 4. Pulmonary Fibrosis and Lung Scarring
- 5. Blood Clots (Chronic Thromboembolic PH)
- 6. Mitral Valve Issues: The Leaky Faucet
- 7. Congenital Heart Defects You Were Born With
- 8. The Impact of Living at High Altitudes
- 9. Autoimmune Diseases (Lupus and Scleroderma)
- 10. Liver Disease (Portopulmonary Hypertension)
- 11. HIV and Chronic Infection Links
- 12. Certain Medications and Toxin Triggers
1. The "Backup" from Left-Sided Heart Disease
By far, the most common reason I see patients develop high pressure in their lungs is due to issues on the left side of the heart. Think of your heart and lungs as a closed plumbing loop. The right side of the heart pumps blood into the lungs to get oxygen. The lungs then send that fresh blood to the left side of the heart, which pumps it out to the rest of the body. It’s a beautiful, continuous cycle when it works.
However, if the left side of your heart is weak (systolic failure) or too stiff (diastolic failure), it can’t pump the blood out fast enough. Imagine a sink drain that is clogged. The water doesn't go down; it backs up into the sink. In your body, the "sink" is the left heart, and the "backup" goes straight into the blood vessels of your lungs. This fluid congestion raises the pressure significantly. Over time, the arteries in the lungs get thicker and harder to try to handle this extra pressure, which only makes the problem worse.
In my experience, many people don't realize they have left heart failure until the lung pressure alerts us. It’s a chain reaction. The lungs are screaming because the heart isn't clearing the traffic. Treating the heart failure usually relieves the lung pressure.
2. COPD and Emphysema: The Airway Blockers
Chronic Obstructive Pulmonary Disease (COPD) and emphysema are major players here. These conditions damage the air sacs (alveoli) and the airways in your lungs. When you have COPD, it’s hard to get air out of your lungs, and your oxygen levels tend to drop. This is where the body’s survival instincts actually backfire on us.
When parts of your lungs don’t get enough oxygen, the blood vessels in those specific areas tighten up. This is a reflex called "hypoxic vasoconstriction." The body tries to divert blood away from the damaged areas to the healthy areas. It’s a smart move in the short term. But in COPD, large parts of the lungs lack oxygen all the time. This means blood vessels all over the lungs tighten up simultaneously.
Imagine trying to push water through a garden hose, and then someone squeezes the hose tightly. The pressure behind the squeeze shoots up. That is exactly what happens in the pulmonary arteries. The heart has to work double-time to push blood through these squeezed, narrow vessels. Over years of smoking or exposure to bad air, this constant squeezing leads to secondary pulmonary hypertension.
3. Sleep Apnea’s Silent Nighttime Damage
This one surprises a lot of my patients. You might think, "I just snore a little, how does that hurt my heart?" Obstructive Sleep Apnea (OSA) is a condition where your throat muscles relax too much during sleep, blocking your airway. You might stop breathing for seconds or even a minute, dozens of times an hour. Every time you stop breathing, the oxygen level in your blood plummets.
Remember that reflex I mentioned earlier? When oxygen drops, lung vessels tighten. If you have severe untreated sleep apnea, your lung vessels are squeezing tight all night long, every single night. This creates a rollercoaster of high pressure in the pulmonary arteries. Over time, these vessels stay stiff and narrow even when you are awake.
I often tell patients that sleep is supposed to be the time your heart rests. With sleep apnea, your heart is running a marathon while you sleep. The strain on the right side of the heart (which pumps to the lungs) can be immense. The scary part is that you are asleep, so you don't feel the struggle, but you wake up tired, with a headache, and with rising lung pressure.
4. Pulmonary Fibrosis and Lung Scarring
Pulmonary fibrosis is a condition where the tissue deep in your lungs becomes thick, stiff, and scarred. As the lung tissue scars, it gets harder to breathe because the lungs can't expand like a soft balloon anymore—they become more like a stiff leather bag. But the damage isn't just to the air sacs; it affects the blood vessels, too.
The tiny capillaries (the smallest blood vessels) run right through this lung tissue. When the tissue scars, it physically crushes and destroys these tiny vessels. It’s a simple matter of capacity. If you destroy 50% of the roads in a city, the remaining roads will have terrible traffic jams. In the lungs, as capillaries are destroyed by scar tissue, the blood has fewer paths to take.
This forces the same amount of blood to squeeze through fewer vessels, which naturally drives the pressure up. Additionally, the low oxygen levels caused by the scarring trigger that same "tightening" reflex we talked about with COPD. It is a double whammy: fewer vessels available, and the ones that are left are squeezed tight.
5. Blood Clots (Chronic Thromboembolic PH)
This cause has a long name—Chronic Thromboembolic Pulmonary Hypertension (CTEPH)—but the concept is straightforward. It starts with a pulmonary embolism, which is a blood clot that travels to the lungs, usually from the legs (DVT). Most of the time, the body dissolves these clots with blood thinners, and things go back to normal.
However, in a small number of unlucky people, the body fails to dissolve the clot completely. Instead, the clot hardens and turns into scar tissue inside the lung arteries. It becomes like cement, permanently blocking the flow of blood. If enough of these old, scarred clots build up over time, they block off significant portions of the lung’s plumbing.
The right side of the heart has to push incredibly hard to get blood past these blockages. I want to highlight this one because it is unique: it is one of the few types of pulmonary hypertension that can sometimes be cured with surgery. A specialized operation can actually scrape these old clots out of the arteries, instantly lowering the pressure. It’s risky, but the results can be miraculous.
6. Mitral Valve Issues: The Leaky Faucet
The mitral valve acts as the gateway between the upper and lower chambers on the left side of your heart. It controls the flow of blood that has just returned from the lungs. If this valve is "stenotic" (too tight) or acts like a "leaky faucet" (regurgitation), it causes major pressure problems upstream in the lungs.
In mitral stenosis, the door is too narrow. The blood struggles to get through, so it piles up behind the door—right back into the lungs. In mitral regurgitation, the door doesn't close properly. When the heart pumps, blood shoots backward through the valve, again, flooding the lungs. Both scenarios result in increased volume and pressure in the pulmonary veins.
In my experience, patients often tolerate this for years because the heart tries to compensate. But eventually, the pressure becomes too much. The pulmonary arteries react by thickening, leading to secondary hypertension. Fixing the valve—either through repair or replacement—is usually the only way to relieve the pressure on the lungs. It’s plumbing 101: fix the broken valve to stop the backup.
7. Congenital Heart Defects You Were Born With
Congenital heart defects aren't just for kids; many adults live with them without knowing until symptoms appear later in life. A common example is a "hole in the heart," such as an Atrial Septal Defect (ASD) or Ventricular Septal Defect (VSD). These are holes in the wall separating the right and left sides of the heart.
Normally, the left side has higher pressure. If there is a hole, blood flows from the high-pressure left side to the low-pressure right side. This extra blood gets pumped into the lungs. Imagine the lungs are used to receiving 5 liters of blood a minute, and suddenly they are receiving 10 liters because of this leak. The pulmonary arteries aren't built for that volume.
Over years, this high flow damages the lining of the lung arteries. They become stiff and thick to handle the stress. Eventually, the pressure in the lungs can get so high that it reverses the flow through the hole (Eisenmenger syndrome), which is a very serious condition. I’ve seen patients in their 40s discover a hole they’ve had since birth because they finally got checked for breathlessness.
8. The Impact of Living at High Altitudes
This is a fascinating cause that relates to geography. If you live high in the mountains—like in the Andes, the Himalayas, or high parts of Colorado—the air is thinner. There is less oxygen available in every breath you take. As we discussed earlier, the lungs have a reflex where they constrict (tighten) blood vessels when oxygen is low.
For most people visiting high altitudes, this is temporary. But if you live there permanently, your lung vessels are in a state of chronic constriction. Your body also produces more red blood cells to try to grab more oxygen, which makes your blood thicker and more like sludge. The combination of tight vessels and thick blood makes the heart work much harder to pump through the lungs.
I have treated patients who moved from sea level to the mountains and developed symptoms within a year. It’s not that their lungs are "diseased" in the traditional sense; they just aren't genetically adapted to that environment. Sometimes, the only "cure" for this specific type of secondary pulmonary hypertension is actually moving back down to sea level, where oxygen is plentiful.
9. Autoimmune Diseases (Lupus and Scleroderma)
Autoimmune diseases are confusing because the body essentially attacks itself. Conditions like Scleroderma (Systemic Sclerosis), Lupus, and Rheumatoid Arthritis can cause significant inflammation in the blood vessels of the lungs. Scleroderma is particularly aggressive in this regard.
In these conditions, the immune system mistakenly targets the lining of the pulmonary arteries. This causes inflammation and an overgrowth of cells that clog the vessel from the inside. It’s like rust building up inside a pipe—the opening gets smaller and smaller. This increases resistance, causing the blood pressure in the lungs to soar.
What makes this tricky is that it can happen even if the patient's lung tissue looks fine on an X-ray. It is a vascular (blood vessel) problem, not necessarily an airway problem. In my practice, I screen my Scleroderma patients for pulmonary hypertension every single year, regardless of how they feel. We have to catch this one early because it moves fast.
10. Liver Disease (Portopulmonary Hypertension)
The connection between the liver and the lungs is one that even some doctors overlook. This condition is called Portopulmonary Hypertension. It occurs in people with serious liver disease or portal hypertension (high pressure in the liver's blood vessels). It’s a complex biochemical process.
When the liver is damaged, it fails to filter certain toxins and substances from the blood. These substances bypass the liver and travel straight to the heart and lungs. Some of these unfiltered chemicals can cause the blood vessels in the lungs to spasm and thicken. It effectively transfers the high pressure from the liver system into the lung system.
This is a critical diagnosis because it affects liver transplant eligibility. If a patient needs a new liver but has severe pulmonary hypertension, the surgery is too dangerous. We often have to treat the lung pressure with aggressive medication first to get it low enough so the patient can safely undergo a liver transplant. It’s a delicate balancing act.
11. HIV and Chronic Infection Links
It has been established for years that the Human Immunodeficiency Virus (HIV) can trigger pulmonary hypertension. While modern antiretroviral therapies have made HIV a manageable chronic condition, the risk for lung pressure issues remains higher than in the general population. We don't fully understand the exact mechanism, but we believe the virus itself, or the chronic inflammation it causes, stimulates the growth of smooth muscle cells in the lung arteries.
This extra muscle makes the artery walls thick and stiff. The good news is that this complication is relatively rare compared to other HIV complications, but it is serious. Because HIV patients are living much longer, healthier lives now, we are seeing this more often simply because there is more time for it to develop.
Other chronic infections, like Schistosomiasis (a parasitic worm infection common in parts of Asia, Africa, and South America), are actually a leading cause of pulmonary hypertension globally. The parasite eggs get lodged in the lung vessels, causing inflammation and blockage. While rare in the US or Europe, it is a massive global health issue.
12. Certain Medications and Toxin Triggers
Finally, we have to look at what we put into our bodies. Historically, certain diet drugs (like "Fen-Phen" in the 90s) caused an epidemic of pulmonary hypertension. While those specific drugs are off the market, other substances can still act as triggers. Methamphetamines and cocaine are major offenders in the modern world.
These stimulants cause severe clamping (constriction) of blood vessels. Chronic use essentially burns out the blood vessels in the lungs. I have seen young patients, in their 20s and 30s, with the hearts of 80-year-olds because of methamphetamine use. The damage causes the vessels to remodel and stay narrow permanently.
Additionally, certain chemotherapy drugs used for cancer (like Dasatinib) have been linked to developing high lung pressure. It’s always a risk-benefit analysis. If you are taking strong medications, it’s important to monitor for breathlessness so doctors can switch your prescription if the lungs start reacting negatively.
Trusted Resources for Further Learning
I believe in empowering my patients with the best information. Here are two resources I trust implicitly for accurate, easy-to-understand data:
- Best Article: Mayo Clinic: Pulmonary Hypertension Guide – This is the gold standard for patient information. It breaks down the types and treatments clearly.
- Best Video: Khan Academy: Pulmonary Hypertension Explained – This video uses simple drawings to explain exactly how the pressure builds up. It’s fantastic for visual learners.
Conclusion & Next Steps
We have covered a lot of ground today. From the mechanics of a failing left heart to the silent damage of sleep apnea and blood clots, secondary pulmonary hypertension is a condition with many faces. But if you take one thing away from this article, let it be this: breathlessness is not normal, and it is not just "getting old."
If you find yourself gasping for air after simple tasks, or if you feel a tightness in your chest that wasn't there last year, please do not ignore it. The causes we discussed—heart failure, COPD, clots, sleep apnea—are all treatable. The earlier we catch the secondary cause, the better chance we have of reversing the pressure in your lungs and getting you back to your life.
I hope this guide helped demystify the frightening terms you might have heard in the doctor's office. Knowledge is your best prescription. Now, I’d love to hear from you. Have you or a loved one struggled with getting a diagnosis for breathing issues? Did treating the underlying cause help? Drop a comment below and share your story—it might just help someone else who is feeling alone in this journey.
Hi, I’m Dr. Alex. I’m a cardiology specialist who believes medicine shouldn't be a secret language. I’ve spent the last 15 years helping folks from all over the world understand their hearts better. When I’m not in the clinic or writing these guides, you’ll usually find me hiking (slowly!) or trying to brew the perfect cup of coffee.