Rio Bravo qWeek

Episode 211: Understanding HFpEF.  Hyo Mun and Jordan Redden (medical students) explain the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and how it differentiates from HFrEF. Dr. Arreaza asks insightful questions and summarizes some key elements of HFpEF.  Written by Hyo Mun, MS4, American University of the Caribbean; and Jordan Redden, MS4, Ross University School of Medicine. Comments and edits by Hector Arreaza, MD. You are listening to Rio Bravo qWeek Podcast, your weekly dose of knowledge brought to you by the Rio Bravo Family Medicine Residency Program from Bakersfield, California, a UCLA-affiliated program sponsored by Clinica Sierra Vista, Let Us Be Your Healthcare Home. This podcast was created for educational purposes only. Visit your primary care provider for additional medical advice. What is EF? Just imagine, the heart is a pump, blood gets into the heart through the veins, the ventricles fill up and then squeeze the blood out. So, the percent of blood that is pumped out is the EF. Let’s start at the beginning.  What is HFpEF? Mike: HFpEF stands for heart failure with preserved ejection fraction. Basically, these patients squeeze normally—their ejection fraction is 50% or higher—but here's the thing: the heart can't relax and fill the way it should. The muscle gets stiff, almost like a thick leather boot that just won't stretch. And because the ventricle can't fill properly, pressure starts backing up into the lungs and the rest of the body. That's when patients start experiencing shortness of breath, leg swelling, fatigue—all those classic symptoms. Dr. Arreaza: And this is where people get fooled by the ejection fraction. Mike: Exactly. The ejectionfraction tells you total left ventricular emptying, not just forward flow. Jordan: The classic example is severe mitral regurgitation. You can eject 60% of your blood volume and still be in cardiogenic shock because most of that blood is leaking backward into the left atrium instead of going into the aorta. So, you get pulmonary edema, hypotension, fatigue, all with a “normal” EF. Which is honestly terrifying if you’re over-relying on echo reports without thinking clinically. Dr. Arreaza: And in HFpEF, functional mitral regurgitation often shows up later in the disease. It’s not usually the primary cause; it’s more of a marker of advanced disease. Moderate to severe MR in HFpEF independently predicts worse outcomes, including a higher risk of mortality or heart failure hospitalization. So, let’s contrast this with HFrEF. How are these two different? Mike: HFrEF—heart failure with reduced ejection fraction—is a pumping problem. The heart muscle is weak and can't contracteffectively. Ejection fraction drops below 40%, and this is your classic systolic dysfunction. Jordan: HFpEF, on the other hand, is diastolic dysfunction. The heart muscle is thick, fibrotic, and noncompliant. It squeezes fine, but it just doesn’t relax, even though the EF looks reassuring on paper. Mike: I like to explain it this way: HFrEF is a weak heart that can't squeeze. HFpEF is a stiff heart that can't relax. Totally different problems. Dr. Arreaza: And then there’s the gray zone: heart failure with mildly reduced EF, or HFmrEF. That’s an EF between 41 and 49% with evidence of elevated filling pressures. It really shares the features of both worlds. So, what actually causes HFpEF versus HFrEF? Jordan: HFpEF is basically what happens when all the problems of modern living catch up with you. You've got chronic hypertension, obesity, diabetes, metabolic syndrome, aging, systemic inflammation—all of these things slowly remodel the heart over years. The muscle gets thick and stiff, and eventually the ventricle just loses its ability to relax. So, HFpEF is really a disease of metabolic dysfunction and chronic stress in the heart.  Mike: HFrEF is more about direct injury. Think about myocardial infarctions, ischemic cardiomyopathy, viral myocarditis, alcohol toxicity, chemotherapy like doxorubicin, genetic cardiomyopathies, or chronic uncontrolled tachycardia. These insults actually damage or kill heart muscle cells, leading to a dilated, weak ventricle that can’t pump effectively. Dr. Arreaza: So the short version: HFpEF is caused by chronic metabolic and hypertensive stress, while HFrEF is caused mainly by myocardial damage. A question we get a lot: does HFpEF eventually turn into HFrEF? What do you guys think? Mike: In most cases, no. HFpEF patients usually stay HFpEF throughout their disease course. They don’t just “burn out” and turn into HFrEF. Jordan: They’re generally separate disease entities with different pathophysiology. A patient with HFpEF can develop HFrEF if they have a big myocardial infarction or ongoing ischemia that damages the muscle, but that’s not the natural progression. Mike: Interestingly though, the opposite can happen. Some HFrEF patients actually improve their ejection fraction with good medical therapy—that's called HF with improved EF—and it's a great sign that treatment is working. Dr. Arreaza: Another question. How do HFpEF and HFrEF compare to restrictive cardiomyopathy and constrictive pericarditis? Jordan: Clinically, they can all look very similar: dyspnea, edema, fatigue, but the underlying mechanisms are completely different. Mike: In HFpEF, the myocardium itself is stiff from hypertrophy and fibrosis. The problem is intrinsic to the heart muscle, and EF stays preserved. Echoshows diastolic dysfunction with elevated filling pressures. Jordan: In HFrEF, the myocardium is weak. The ventricle is often dilated and contracts poorly, with a reduced EF. Mike: Restrictive cardiomyopathy is different. Here, the myocardium gets infiltrated by abnormal stuff—amyloid, iron, sarcoid—and that makes it extremely stiff. It can look like HFpEF on the surface, but it's usually more severe. On Echo You'll see biatrial enlargement, small ventricles, and preserved EF. And importantly, it's a pathologic diagnosis, so you need advanced imaging or biopsy to confirm it. Jordan:  Constrictive pericarditis is another mimic, but here the myocardium is usually normal. The problem is that the pericardium is thickened, calcified, and rigid. This will physically prevent the heart from being filled. Imaging shows pericardial thickening, septal bounce, and respiratory variation in flow, and cath shows equalization of diastolic pressures, which is the hallmark of constrictive pericarditis. Dr. Arreaza: So the takeaway is: HFpEF is a clinical syndrome driven by common metabolic and hypertensive causes, while restrictive and constrictive diseases are specific pathologic entities. If “HFpEF” is unusually severe or not responding to treatment, you need to think beyond HFpEF. Which type of heart failure is more common right now? Mike: Good question, the answer is: HFpEF. It now accounts for up to 60% of all heart failure cases, and it’s still rising. Dr. Arreaza: Why is that? Jordan: Because people are living longer, gaining weight, and developing more metabolic syndrome. HFpEF thrives in older, or people with obesity, hypertension, or diabetes: basically, the modern American population. At the same time, better treatment of acute MIs means fewer people are developing HFrEF from massive heart attacks. Mike: HFpEF is the heart failure epidemic of the 21st century. It’s honestly the cardiology equivalent of type 2 diabetes. Dr. Arreaza: Let’s talk aboutCOVID-19. (2025 and still talking about it) Does it actually increase heart failure risk? Mike: Yes, absolutely. COVID increases both acute and long-term heart failure risk. Jordan: During acute infection, COVID can cause myocarditis, trigger massive inflammation, and precipitate acute decompensated heart failure, especially in patients with pre-existing disease. It also causes microthrombi, which can injure the myocardium. Mike: And after infection, even mild cases are linked to a significantly higher risk of developing new heart failure within the following year. Both HFpEF and HFrEF rates go up. Dr. Arreaza: I remember seeing this in 2021, we had a patient with acute COVID and HFrEF, her EF was about 10%, I lost contact with the patient and at the end I don’t know what happened to her. What’s the pathophysiology of COVID and heart failure? Mike: COVID causes direct viral injury through ACE2 receptors, triggers massive inflammation that damages the endothelium and heart muscle, leads to microvascular clotting and fibrosis—all mechanisms that promote HFpEF. Jordan: Add autonomic dysfunction, persistent low-grade inflammation, and worsening metabolic syndrome, and you’ve got a perfect storm for heart failure. Dr. Arreaza: Bottom line: COVID is a cardiovascular disease as much as a respiratory one. If someone had COVID and now has unexplained dyspnea or fatigue, think about heart failure. Get an echo, get a BNP, start treatment. Last big question: why did we have so many therapies for HFrEF but essentially none for HFpEF for years? Mike: HFrEF is mechanistically straightforward. You've got a weak heart with excessive neurohormonal activation going on — so you block RAAS, block the sympathetic system, drop the afterload. The drugs make sense. Jordan: HFpEF is messy. It’s not one disease. It’s stiffness, fibrosis, inflammation, microvascular dysfunction, metabolic disease, atrial fibrillation, all overlapping. One drug can’t fix all of that. Mike: And some drugs that worked beautifully in HFrEF actually made HFpEF worse. Take Beta blockers, for example.  They slow heart rate, which is a problem because HFpEF patients rely on heart rate to maintain their cardiac output. Jordan: The breakthrough came with SGLT-2 inhibitors: diabetes drugs that unexpectedly addressed multiple HFpEF mechanisms at once: volume, metabolism, inflammation, and myocardial energetics. Dr. Arreaza: The miracle drug