Fatigue: When It's Your Heart

"I'm just so tired" is one of the hardest symptoms to evaluate in cardiology. It's vague, it's common, and it has a long list of possible causes that aren't cardiac at all. But fatigue is also a real and underrecognized symptom of heart problems, especially in women, in older patients, and in anyone with reduced heart function. The trick is figuring out when fatigue points toward the heart and when it points elsewhere.

I'm Dr. Damian Rasch, a cardiologist in Encinitas. This article walks through how I sort out cardiac fatigue from the dozen other possible explanations.

What Cardiac Fatigue Looks Like

Cardiac fatigue is usually exertional. The patient describes feeling worn out after activities they used to handle easily, like walking the dog, getting up a single flight of stairs, or doing the laundry. The fatigue is often associated with mild shortness of breath that the patient may not even recognize as breathlessness, calling it "feeling weak" instead. The pattern progresses over weeks to months.

Other clues that point cardiac:

- Associated leg swelling or weight gain

- Difficulty lying flat at night, or waking with shortness of breath

- A prior history of heart attack, valve disease, or cardiomyopathy

- A new diagnosis of atrial fibrillation

- Palpitations or a sense that the heart is racing or skipping

- Lightheadedness with exertion

If your fatigue is purely after a poor night of sleep, related to a stressful period at work, or following a viral illness, the cardiac probability is much lower. If it's been creeping up steadily over weeks despite rest, that's the pattern that warrants evaluation.

The Cardiac Causes

Heart failure

When the heart can't generate enough output to meet the body's demand, the symptoms are some combination of fatigue, dyspnea, and fluid retention. Both reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF) cause fatigue. The NYHA class captures it: Class I has no limitation, Class II has slight limitation with ordinary activity, Class III has marked limitation with less than ordinary activity, Class IV has symptoms at rest.

If you have known heart failure and your fatigue is worsening, the question is usually whether you've decompensated (need diuretic adjustment), whether your medication regimen needs optimization, or whether something new has developed (atrial fibrillation, anemia, new ischemia).

Valvular heart disease

Severe aortic stenosis classically presents with the triad of angina, syncope, and dyspnea, but fatigue is often the earliest symptom. Patients describe a slow, insidious decline in stamina over months. Severe AS is a class I indication for valve replacement (TAVR or surgical) once symptoms appear.

Severe mitral regurgitation causes exertional fatigue and dyspnea. Severe primary MR with symptoms or LV dysfunction warrants intervention (MitraClip or surgical repair).

Severe tricuspid regurgitation causes fatigue, leg edema, and abdominal bloating from right-sided congestion.

Bradyarrhythmias

Sinus node dysfunction (chronotropic incompetence) means the heart can't speed up appropriately with exertion. Patients feel exercise intolerant and exhausted. Diagnosis often requires a stress test or ambulatory monitor.

AV block at any degree can cause fatigue. High-degree block warrants pacemaker evaluation.

Tachyarrhythmias

Atrial fibrillation with rapid ventricular response causes exertional fatigue and dyspnea. Even AFib with controlled rate can cause fatigue from loss of atrial contribution to filling. New-onset AFib is a common explanation for new fatigue in older patients.

Persistent SVT or atrial tachycardia can cause tachycardia-mediated cardiomyopathy, presenting as fatigue and dyspnea after weeks to months of an unrecognized rhythm.

Cardiac Medications That Cause Fatigue

A particular irony in cardiology is that many of the medications we use to treat heart problems can themselves cause fatigue, especially when first started or after a dose increase.

Beta-blockers (metoprolol, carvedilol, bisoprolol) commonly cause fatigue and exercise intolerance, especially in the first few weeks. The benefit on survival in HFrEF and post-MI is large enough that we typically push through. Switching from one beta-blocker to another sometimes helps, and dose reduction can be a reasonable compromise. Fatigue from beta-blockers usually improves over weeks.

ACE inhibitors and ARBs can cause fatigue from low blood pressure, especially in the first weeks. Adjusting the timing or dose usually resolves it.

Diuretics (furosemide, torsemide, bumetanide) cause fatigue when they over-deplete or cause electrolyte abnormalities, especially low potassium or low magnesium.

Mineralocorticoid receptor antagonists (spironolactone, eplerenone) can cause fatigue, especially with high potassium or kidney dysfunction.

Sacubitril/valsartan (Entresto) can cause low blood pressure-related fatigue, especially at initiation.

Amiodarone can cause fatigue through hypothyroidism, which it induces in 10 to 20 percent of long-term users.

If you started a new cardiac medication and the fatigue began within days to weeks, the medication is probably contributing. Don't stop it without talking to your prescriber. Adjustments are usually possible.

Non-Cardiac Causes That Mimic Cardiac Fatigue

Anemia reduces oxygen delivery and is a leading cause of new fatigue. Iron deficiency anemia is common in heart failure (about half of HFrEF patients), and treating it with intravenous iron improves quality of life and exercise tolerance. A simple CBC and iron studies catch this.

Hypothyroidism causes fatigue, weight gain, cold intolerance, dry skin, and constipation. A TSH should be checked at the first visit for new fatigue.

Sleep apnea causes daytime fatigue, morning headaches, and poor concentration. It's also a major cause of resistant hypertension, atrial fibrillation, and worsening heart failure. Estimated prevalence in HF patients is 50 to 70 percent. A sleep study is warranted with snoring, witnessed apneas, daytime sleepiness, or refractory cardiac symptoms.

Depression causes fatigue, loss of interest, sleep disturbance, and reduced motivation. It's common in patients with cardiac disease and often underdiagnosed. Screening with a PHQ-9 takes two minutes and is worth doing.

Deconditioning from a sedentary period (after surgery, after illness, after a long winter) causes real fatigue and exercise intolerance. The fix is gentle progressive activity.

Long COVID can cause persistent fatigue for months after acute infection, often with associated POTS, exercise intolerance, and brain fog.

Vitamin D deficiency, low B12, electrolyte abnormalities, and chronic kidney disease all contribute to fatigue.

The Workup

A reasonable initial workup for new persistent fatigue includes:

History and exam with attention to cardiac risk factors, current medications, sleep history, mood symptoms, and energy patterns through the day.

Labs: CBC with iron panel, TSH, BMP (kidney function, electrolytes), liver function, BNP if heart failure suspected, vitamin D, B12.

EKG: rules out arrhythmia, heart block, prior MI patterns.

Echocardiogram if cardiac suspected based on exam, history, or BNP.

Stress test if exertional symptoms warrant evaluation for ischemia or chronotropic incompetence.

Sleep study if OSA suspected.

In most patients, this workup quickly identifies the cause. The hardest cases are those where everything looks normal. Those often turn out to be deconditioning, depression, or undiagnosed sleep apnea.

Common Patient Questions

I started metoprolol two weeks ago and I'm exhausted. Is this just from the medication?

Probably yes, partially. Beta-blocker fatigue is common in the first 2 to 6 weeks and often improves. Don't stop the medication without talking to your doctor. If the fatigue is severe and persistent, options include reducing the dose, switching beta-blocker (carvedilol versus metoprolol versus bisoprolol have different profiles), or considering an alternative agent if you're on it for blood pressure rather than heart failure.

My EF is 30 percent and I'm constantly tired. Why?

Reduced cardiac output is itself fatiguing. The four pillars of HF therapy (beta-blocker, ACE/ARB/sacubitril-valsartan, MRA, SGLT2 inhibitor) all improve symptoms over time. Iron deficiency, sleep apnea, atrial fibrillation, and depression should all be screened for. Cardiac rehabilitation is genuinely helpful and is covered by Medicare for HFrEF.

My TSH and CBC are normal. Could it still be cardiac?

Yes. Normal labs don't rule out cardiac fatigue. An EKG and echo are the next stops if there are any cardiac risk factors or exertional features.

I had COVID six months ago and I'm still exhausted. Is my heart involved?

Possibly. Long COVID can include cardiac involvement (mild myocarditis, microvascular dysfunction, POTS). A focused cardiac evaluation including echo, sometimes cardiac MRI, and orthostatic vitals is reasonable. Many patients improve with patience, gradual reconditioning, salt and fluid for orthostatic intolerance, and addressing sleep.

My doctor offered iron infusions for my heart failure. Is that worthwhile?

For HFrEF patients with iron deficiency (ferritin under 100, or ferritin 100 to 300 with transferrin saturation under 20 percent), IV iron has been shown in multiple trials (CONFIRM-HF, AFFIRM-AHF, IRONMAN) to improve quality of life and exercise capacity. It's a reasonable intervention.

Is exercise safe if I'm so fatigued?

For patients with stable cardiac disease, supervised cardiac rehabilitation or a graded home exercise program is one of the most effective fatigue treatments. The early sessions feel hard. Within 6 to 8 weeks most patients feel better than they have in months. Cardiac rehabilitation is covered by Medicare and most insurers for qualifying conditions.

My energy is fine in the morning but I crash by mid-afternoon. Could that be cardiac?

Cardiac fatigue is often more constant or progressive through the day with exertion. Mid-afternoon crashes more often relate to sleep quality, blood sugar swings (especially in pre-diabetes), or postprandial dips. Sleep apnea is worth screening for if you snore.

A Final Note From Me

Fatigue is the symptom patients most often dismiss. They tell themselves it's normal aging, or stress, or that they should be tougher. Some of those explanations are right. Many are not. If your fatigue is new, progressing, or interfering with how you want to live, it's worth a real workup. Most causes are treatable. The few that turn out to be cardiac are much easier to treat in the early stages.

If you have any cardiac history, take new fatigue seriously. If you don't, take it seriously anyway, but the workup may pivot to non-cardiac causes quickly.

References

1. Heidenreich, Paul A., Biykem Bozkurt, David Aguilar, et al. "2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure." Circulation 145, no. 18 (2022): e895-e1032.

2. Ko, Dennis T., Patricia R. Hebert, Christopher S. Coffey, et al. "Beta-Blocker Therapy and Symptoms of Depression, Fatigue, and Sexual Dysfunction." JAMA 288, no. 3 (2002): 351-357.

3. Anker, Stefan D., Javed Butler, Gerasimos Filippatos, et al. "Effect of Ferric Carboxymaltose on Hospitalisations and Mortality in Iron-Deficient Heart Failure Patients (AFFIRM-AHF)." Lancet 396, no. 10266 (2020): 1895-1904.

4. Kalra, Paul R., John G. F. Cleland, Mark C. Petrie, et al. "Intravenous Ferric Derisomaltose in Patients With Heart Failure and Iron Deficiency in the UK (IRONMAN)." Lancet 400, no. 10369 (2022): 2199-2209.

5. Cowie, Martin R., Holger Woehrle, Karl Wegscheider, et al. "Adaptive Servo-Ventilation for Central Sleep Apnea in Systolic Heart Failure (SERVE-HF)." New England Journal of Medicine 373, no. 12 (2015): 1095-1105.

6. Rutledge, Thomas, Veronica A. Reis, Sarah E. Linke, Barry H. Greenberg, and Paul J. Mills. "Depression in Heart Failure: A Meta-Analytic Review of Prevalence, Intervention Effects, and Associations With Clinical Outcomes." Journal of the American College of Cardiology 48, no. 8 (2006): 1527-1537.

7. Long, Lindsey, Rod S. Taylor, Karen Rees, et al. "Exercise-Based Cardiac Rehabilitation for Adults With Heart Failure." Cochrane Database of Systematic Reviews 1, no. 1 (2019): CD003331.

8. Otto, Catherine M., Rick A. Nishimura, Robert O. Bonow, et al. "2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease." Journal of the American College of Cardiology 77, no. 4 (2021): e25-e197.

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.