Fatigue: When It's Your Heart, and What to Do Next
Fatigue is one of the most common complaints in primary care, and it's also one of the most frustrating. Patients describe it in dozens of ways. They feel tired all the time. They have no energy by mid-afternoon. They can't make it through a workout they used to coast through. They wake up unrefreshed. They feel like they're moving through water. The list of possible causes is enormous, ranging from the trivial to the life-threatening, and figuring out which bucket a particular patient falls into is one of the harder problems in medicine.
I'm Dr. Damian Rasch, a cardiologist in Encinitas. Patients come to me when their primary doctor has worried about a cardiac contribution to their fatigue, or when they've noticed that the fatigue is happening alongside heart-related symptoms like shortness of breath, leg swelling, or palpitations. This article walks through how I think about fatigue when the heart is on the differential, what the cardiac causes look like, what the major non-cardiac mimickers are, what the workup involves, and when the symptom warrants a real workup versus reassurance.
When Fatigue Is Cardiac
Cardiac fatigue has a recognizable shape, and recognizing the pattern is the first step. The classic features are exertional fatigue (the patient gets unusually tired with exertion that previously didn't bother them), accompanying shortness of breath, and a recent decline in functional capacity that's faster than expected for age.
The mechanism in most cardiac fatigue is reduced cardiac output, either at rest or with exertion. The heart can't deliver enough blood to working muscles, the muscles can't extract enough oxygen, and the patient feels exhausted with effort that should be easy. In some cases the fatigue at rest reflects ongoing neurohormonal activation, with elevated catecholamines and inflammatory cytokines that contribute to the malaise patients describe.
A few features should raise concern that fatigue is cardiac. Fatigue with exertional dyspnea (climbing one flight of stairs leaves you winded). Fatigue with orthopnea (you're sleeping on more pillows than you used to). Fatigue with leg swelling, especially if bilateral and pitting. Fatigue with palpitations or known atrial fibrillation. Fatigue with chest discomfort during exertion. Fatigue in a patient with a history of heart attack, valvular disease, or known cardiomyopathy. Fatigue with a sudden decline rather than a slow gradual one.
When the fatigue stands alone, with no other heart-related symptoms, the cardiac causes are usually further down the differential. When the fatigue is accompanied by even one of the symptoms above, the heart moves up the list quickly.
The Cardiac Conditions That Cause Fatigue
A handful of cardiac conditions account for most of the cardiac fatigue I see in clinic.
Heart failure, both HFrEF and HFpEF, is the leading cardiac cause of fatigue. The mechanism in HFrEF is reduced forward output that limits oxygen delivery to muscles. In HFpEF, the elevated filling pressures and inability to augment cardiac output with exercise produce the same symptom. Patients with heart failure also have neurohormonal activation, anemia, deconditioning, and often sleep-disordered breathing, all of which contribute to fatigue. Treatment of the underlying heart failure (the four-pillar regimen for HFrEF, SGLT2 inhibitor and aggressive comorbidity management for HFpEF) usually improves fatigue substantially within weeks to months.
Atrial fibrillation is one of the more common causes of new fatigue in older patients. The loss of atrial kick, combined with an irregular and often rapid ventricular response, drops cardiac output by 20 to 30 percent in many patients, especially those with stiff ventricles who depend on atrial contraction for filling. Some patients have AFib for years without realizing it because the irregularity is mild and the rate isn't dramatically elevated. New unexplained fatigue in a patient over 65 should always prompt a careful pulse check and an EKG. Rate control or rhythm control (with antiarrhythmics or catheter ablation) often resolves the fatigue.
Bradyarrhythmias, including sinus node dysfunction and high-grade AV block, can cause fatigue when the resting and exertional heart rate fail to keep up with metabolic demand. Patients describe exercise intolerance, dizziness, and sometimes presyncope. The diagnosis is made by EKG, ambulatory rhythm monitoring (Holter, event monitor, patch monitor like Zio, or implantable loop recorder for elusive cases), and sometimes an electrophysiology study. Treatment is pacemaker placement when sinus node dysfunction or AV block is symptomatic.
Severe aortic stenosis, severe mitral regurgitation, and other significant valvular lesions can present primarily with fatigue, especially in older patients who attribute the decline to aging. Aortic stenosis classically presents with the triad of angina, syncope, and heart failure (which manifests as exertional dyspnea and fatigue), but the symptoms often appear gradually over months. Severe MR can be silent for years and then present with reduced exercise capacity. Auscultation, echocardiography, and clinical context guide the workup.
Coronary ischemia, including stable angina and acute coronary syndromes, can present with fatigue rather than chest pain, especially in women, diabetics, and older patients. The clue is usually exertional fatigue that resolves with rest, with the same pattern of provocation each time. A stress test, coronary CT angiogram, or invasive angiography is the appropriate workup.
Pulmonary hypertension, whether primary or secondary to left heart disease, lung disease, or chronic thromboembolism, presents with progressive exertional dyspnea and fatigue. The right ventricle struggles to pump against elevated pulmonary pressures, and exercise capacity drops. The workup includes echo with attention to RV function and TR jet velocity, and often right heart catheterization for confirmation.
Cardiac amyloidosis is increasingly recognized as a cause of HFpEF in older patients with unexplained fatigue, especially men over 65 with bilateral carpal tunnel syndrome and increased LV wall thickness on echo. The diagnosis can be made non-invasively in many cases with technetium pyrophosphate scintigraphy. Treatment with tafamidis or other transthyretin stabilizers improves outcomes when caught early.
Postural orthostatic tachycardia syndrome (POTS) deserves a mention because it's increasingly common, especially after viral illness including COVID, and is often missed for years. Patients describe fatigue, brain fog, exercise intolerance, lightheadedness on standing, palpitations, and sometimes nausea. The diagnosis is a sustained heart rate increase of at least 30 beats per minute (or above 120) within 10 minutes of standing, without significant blood pressure drop. Treatment includes high salt and fluid intake, compression garments, recumbent exercise progression, and selected medications (low-dose beta-blockers, ivabradine, fludrocortisone, midodrine).
The Non-Cardiac Causes Worth Considering
Most fatigue is not cardiac, and the differential is enormous. A few categories account for the majority of cases.
Anemia is one of the most common reversible causes of fatigue. Iron deficiency, B12 deficiency, folate deficiency, anemia of chronic disease, and hemolysis all cause reduced oxygen-carrying capacity and exertional fatigue. A simple CBC with iron studies, B12, and folate is the first-line workup, and treatment of the underlying cause usually resolves the symptom.
Hypothyroidism classically causes fatigue, weight gain, cold intolerance, dry skin, hair loss, constipation, and cognitive slowing. A TSH level is the screening test. Replacement with levothyroxine usually resolves the fatigue within weeks to months.
Diabetes, especially when poorly controlled, causes fatigue through hyperglycemia, polyuria with dehydration, and the systemic effects of metabolic derangement. An A1C and a fasting glucose are the screening tests. Treatment of the underlying diabetes usually improves the fatigue.
Sleep disorders, especially obstructive sleep apnea, are some of the most underrecognized causes of fatigue. Patients often have no idea they're stopping breathing at night. Bed partners report snoring, gasping, restless sleep. Daytime symptoms include unrefreshing sleep, morning headaches, difficulty concentrating, and increased motor vehicle accident risk. A sleep study is the diagnostic test, and CPAP usually transforms how patients feel within weeks.
Depression presents with fatigue more often than people realize. The fatigue of depression is typically accompanied by anhedonia, depressed mood, sleep disturbance (often early morning awakening), appetite changes, difficulty concentrating, and a sense of hopelessness. Screening tools like the PHQ-9 are useful, and treatment with therapy, medications, or both is often effective.
Chronic kidney disease causes fatigue through anemia (decreased erythropoietin), uremic toxin accumulation, electrolyte abnormalities, and bone-mineral disturbances. A basic metabolic panel and a urinalysis screen for it.
Liver disease can cause fatigue through bilirubin accumulation, ammonia elevation, and the systemic effects of hepatic dysfunction. Liver function tests, INR, and albumin screen for it.
Adrenal insufficiency is uncommon but easily missed. The classic presentation is fatigue, weight loss, hyperpigmentation, hypotension, and electrolyte abnormalities (low sodium, high potassium). A morning cortisol level and an ACTH stimulation test are the diagnostic tests.
Medication side effects account for a meaningful share of new fatigue. Beta-blockers, opioids, antihistamines, anticholinergics, benzodiazepines, gabapentin, pregabalin, statins (occasionally), and many others can contribute. A careful medication review, especially around the time the fatigue started, often identifies the culprit.
Long COVID and post-viral fatigue syndromes are now well-recognized causes of persistent fatigue after viral illness. The mechanism is incompletely understood but likely involves persistent immune activation, autonomic dysfunction, microvascular changes, and metabolic disturbances. Treatment is largely supportive and includes structured rehabilitation, treatment of identified co-conditions (POTS, sleep apnea, depression, anemia), and patience.
Cancer presents with fatigue more often than not, sometimes before any other symptom is apparent. Unexplained fatigue accompanied by weight loss, night sweats, lymphadenopathy, or new pain warrants careful evaluation including age-appropriate cancer screening.
Deconditioning is the single most common cause of new exercise intolerance and fatigue in patients who haven't exercised in months or years. The cure is gradual progressive activity, ideally with cardiac and pulmonary screening to rule out coexisting disease before starting an exercise program.
When to Seek Care
Most fatigue is not an emergency. A few situations warrant prompt evaluation rather than waiting for a routine appointment.
Call 911 or go to the emergency department if fatigue is accompanied by chest pain at rest, by sudden severe shortness of breath, by syncope, by new severe palpitations, or by sudden severe weakness on one side of the body or facial droop or speech difficulty (worry about stroke).
Contact your doctor the same day or within a few days for fatigue with new exertional dyspnea, for fatigue with new leg swelling, for fatigue with new palpitations, for fatigue with significant unintentional weight loss (especially over five percent of body weight), for fatigue with night sweats or fevers, or for fatigue that's progressing rapidly over weeks rather than months.
Schedule a primary care visit within a few weeks for chronic fatigue without alarm features, for fatigue you suspect is medication-related, for fatigue in the setting of known sleep problems, for fatigue you think is related to mood or stress, or for fatigue that's been gradually worsening for months. The clinic visit is the right setting when there are no acute features and the question is about getting a workup started.
The Workup
In clinic, the workup for new fatigue is broad because the differential is broad, and the goal of the first visit is usually to screen for the most common reversible causes and to identify any features that should narrow the workup.
The history covers when the fatigue started, what makes it better or worse, what associated symptoms are present (shortness of breath, weight changes, sleep quality, mood, appetite, bowel changes, urinary changes, fever, night sweats), what the patient's medication list looks like, and what the medical history is relevant (heart disease, lung disease, kidney disease, liver disease, thyroid disease, diabetes, depression, prior cancer).
The exam includes vital signs (orthostatic vital signs if POTS or autonomic dysfunction is on the differential), a careful cardiovascular exam, a careful pulmonary exam, an abdominal exam, a thyroid exam, a lymph node survey, and a careful neurologic exam.
Standard labs include a CBC for anemia and white count, a basic metabolic panel for kidney function and electrolytes, liver function tests, a TSH, a fasting glucose or A1C, iron studies if anemia is identified, B12 and folate if anemia or neurologic symptoms are present, vitamin D, and a BNP or NT-proBNP if cardiac fatigue is on the differential.
An EKG is appropriate when cardiac fatigue is on the differential, looking for atrial fibrillation, prior MI, conduction abnormalities, and signs of left ventricular hypertrophy. An echocardiogram is the next step when cardiac fatigue is suspected, especially in the presence of a heart murmur, abnormal EKG, exertional dyspnea, leg swelling, or known heart disease.
Additional testing depends on the clinical picture. Ambulatory rhythm monitoring (Holter, patch monitor, event monitor, or implantable loop recorder) is appropriate for suspected paroxysmal atrial fibrillation or bradyarrhythmias. A stress test or coronary CT angiogram is appropriate for suspected ischemia. A sleep study is appropriate for suspected sleep apnea. Pulmonary function tests are appropriate for suspected COPD or asthma. Cardiopulmonary exercise testing can quantify exercise capacity and help separate cardiac from pulmonary from deconditioning causes.
For patients in whom the standard workup is unrevealing and fatigue persists, additional testing for less common causes (cardiac amyloidosis, autonomic dysfunction, mitochondrial disorders, hidden malignancy, autoimmune disease) is appropriate.
Common Patient Questions
I'm 58 and I'm tired all the time. Could it be my heart?
It could be, but it's more often something else. The first sweep should include a CBC for anemia, a TSH for thyroid disease, a basic metabolic panel, an A1C, and a careful sleep history. If those are unrevealing and you have any heart-related symptoms (exertional dyspnea, orthopnea, leg swelling, palpitations, chest pain), add a BNP, an EKG, and an echo. Most patients with fatigue and no other symptoms turn out to have a non-cardiac cause, but the screening cardiac workup is straightforward and reassuring when negative.
My energy crashes by 2 PM every day. Is that cardiac?
A pattern of post-prandial energy crash is more often related to blood sugar, sleep quality, or circadian rhythm than to the heart. Get a fasting glucose and an A1C, evaluate sleep quality (consider a sleep study if there's snoring, witnessed apneas, or unrefreshing sleep), and look at caffeine and meal timing. If the crash is accompanied by exertional symptoms or other heart-related complaints, add a cardiac workup.
I had COVID two years ago and I'm still exhausted. What can I do?
Long COVID fatigue is real and well-documented, and the workup is worth doing because there are often treatable contributors. Get the standard fatigue panel (CBC, TSH, BMP, LFTs, A1C, B12, vitamin D, ferritin), screen for sleep apnea, check orthostatic vital signs to look for POTS, get a baseline EKG and echo if there are any cardiac symptoms, and consider pulmonary function tests if there's exertional dyspnea. Cardiac MRI is sometimes useful to look for myocarditis or microvascular dysfunction. Treatment is usually multimodal, including structured rehabilitation, treatment of any identified comorbidities, and patience. Many patients improve gradually over months to years.
I'm on a beta-blocker and I'm tired all the time. Is that the medication?
Possibly. Beta-blockers can cause fatigue, especially at higher doses or in patients sensitive to the effect on heart rate and exercise capacity. The strategies are: try a more cardio-selective beta-blocker (metoprolol, bisoprolol, nebivolol) if you're on a non-selective one (propranolol, carvedilol); reduce the dose if clinically appropriate; switch to a different class entirely if the indication is hypertension; or accept the trade-off if the indication is something where beta-blockade is essential (post-MI, heart failure with reduced EF, certain arrhythmias). Talk to your prescriber before changing anything. The benefits of beta-blockers in many cardiac conditions are substantial and shouldn't be given up lightly.
My doctor said my BNP is normal but I'm still exhausted. Can it still be my heart?
A normal BNP makes heart failure as the cause of fatigue much less likely, but doesn't completely rule out cardiac fatigue. Other cardiac causes (ischemia, arrhythmia, valvular disease, pericardial disease, autonomic dysfunction) can produce fatigue without elevating BNP. If clinical suspicion is still high, an echo and ambulatory rhythm monitoring add useful information. If those are also normal, the workup pivots to the non-cardiac differential.
My fatigue is worse when I stand up. Could that be POTS?
It might be. POTS is increasingly common, especially after viral illness including COVID, and is often missed for years. The diagnosis requires a sustained heart rate increase of at least 30 beats per minute (or above 120) within 10 minutes of standing, without significant blood pressure drop, accompanied by orthostatic symptoms. The workup includes orthostatic vital signs in clinic (with measurements at one and three and ten minutes), an EKG, often an echo, and sometimes tilt-table testing. Treatment is structured: high salt and fluid intake, compression garments, recumbent exercise progression, and selected medications. Many patients improve substantially with consistent treatment.
I sleep eight hours but I'm still tired. What does that mean?
Quality matters more than quantity. The most common cause of sleeping eight hours and still feeling tired is unrecognized obstructive sleep apnea, which fragments sleep without the patient being aware. A sleep study is appropriate, especially if you snore, if a bed partner has noticed you stop breathing, or if you wake up with morning headaches. Other causes include depression, hypothyroidism, anemia, sleep disorders (restless legs syndrome, periodic limb movements), and circadian rhythm problems. Consider a sleep study and a basic fatigue workup.
I'm a 70-year-old man with new fatigue and I have to pee at night. Could those be related?
They could be. Nocturia in older patients can come from BPH, but it can also come from heart failure (the body mobilizes fluid overnight when supine and the kidneys make extra urine), poorly controlled diabetes, sleep apnea, and various medications. New fatigue in a 70-year-old man with nocturia warrants a heart failure workup with a BNP and an echo, a urology evaluation for BPH, an A1C for diabetes, and consideration of a sleep study. The combination of fatigue, nocturia, and exertional dyspnea would be classic for heart failure.
A Final Note From Me
Fatigue is one of the symptoms patients most often dismiss as "just life" or "just getting older." Some of that is appropriate. The fifty-year-old who is also raising kids, working full-time, and not sleeping enough doesn't usually have a hidden disease causing the fatigue. They have a hidden lifestyle. But fatigue that is new, progressive, accompanied by other symptoms, or out of proportion to the situation deserves evaluation. Most of the causes are treatable.
From a cardiac standpoint, the symptoms that should prompt evaluation alongside fatigue are exertional dyspnea, orthopnea, leg swelling, weight gain, palpitations, and chest discomfort. A patient with fatigue and any of those symptoms warrants at minimum a BNP, an EKG, and an echo. The workup is inexpensive, fast, and reliably distinguishes cardiac from non-cardiac causes in most cases.
If your fatigue has been chronic and stable for years, a routine workup with your primary care doctor is the right starting point. If it's new and progressing, especially with cardiac symptoms, get evaluated sooner. The treatable cardiac causes (heart failure, atrial fibrillation, valvular disease, ischemia, bradyarrhythmias) all respond well when caught early, and modern treatment changes both how patients feel and how long they live.
References
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10. Ewald, B., Ewald, D., Thakkinstian, A., and Attia, J. "Meta-analysis of B-Type Natriuretic Peptide and N-Terminal Pro B-type Natriuretic Peptide in the Diagnosis of Clinical Heart Failure and Population Screening for Left Ventricular Systolic Dysfunction." Internal Medicine Journal 38, no. 2 (2008): 101-113.
Published on damianrasch.com. The above information was composed by Dr. Damian Rasch, drawing on individual insight and bolstered by digital research and writing assistance. The information is for educational purposes only and does not constitute medical advice.