What Can Be Done for Scar Tissue on the Heart?

Cardiac scar tissue cannot be reversed with any treatment available today, but a growing range of therapies can limit its damage, improve the heart’s pumping ability, and in some experimental settings, begin to replace scar with functional tissue. The scar that forms after a heart attack or chronic heart disease disrupts the electrical signals that keep the heart beating in rhythm and weakens the muscle wall, often leading to heart failure or dangerous arrhythmias. Current options span medications that slow further scarring, surgical procedures that reshape or remove damaged tissue, devices that take pressure off the heart, and supervised exercise programs that curb harmful remodeling. Beyond those established approaches, laboratory research into cell reprogramming, engineered immune cells, injectable biomaterials, and gene therapy is pushing toward treatments that could one day dissolve or replace scar tissue altogether.

Why the Heart Scars in the First Place

When heart muscle cells die, whether from a blocked artery during a heart attack or from years of high blood pressure, the body patches the gap with collagen-rich scar tissue. This scar is stiff and cannot contract the way living muscle does, so every patch of it reduces the heart’s pumping power. Scar tissue also conducts electrical signals poorly. In healthy heart muscle, electrical impulses travel quickly and evenly so the chambers contract in sync. Scar tissue raises the electrical resistance of the damaged zone, slowing and scattering those impulses and setting the stage for irregular heart rhythms.¹ The mismatch between scarred and healthy tissue creates uneven contraction that, over time, stretches the heart out of shape and pushes it toward heart failure.²

The pattern of scarring depends on what caused the damage. A heart attack typically leaves a dense, well-defined patch of scar where blood flow was cut off. Chronic conditions like long-standing high blood pressure or certain cardiomyopathies produce a more diffuse web of fibrosis threaded between living muscle fibers.³ That distinction matters for treatment: a localized scar can sometimes be surgically removed or targeted with a catheter, while diffuse fibrosis calls for medications or systemic therapies that address the whole heart.

Finding and Measuring Scar Tissue

Before deciding what to do about cardiac scar tissue, doctors need to know how much there is and where it sits. The most widely used tool is a specialized MRI technique called late gadolinium enhancement, or LGE. A contrast agent containing gadolinium is injected into the bloodstream and lingers in scarred areas, lighting them up on the scan. LGE has become the standard for mapping scar after a heart attack and for gauging the extent of fibrosis in various cardiomyopathies.⁴ The amount of scar visible on LGE helps predict how well the heart will function going forward and whether the patient is at risk for life-threatening arrhythmias. Several methods exist for quantifying scar extent on these images, ranging from manual outlining to automated signal-intensity thresholds.⁵

A limitation of LGE is that it shows established scar but says little about fibrosis that is still actively forming. A newer imaging approach uses PET scans with radiotracers that bind to fibroblast activation protein, a marker on the surface of the cells actively laying down new collagen. These FAPI-PET scans can detect fibrosis at an earlier, potentially more treatable stage.⁶ In a study of 50 patients with non-ischemic cardiomyopathy, roughly two-thirds showed positive FAPI uptake on PET, and the signal correlated with worse pumping function and higher levels of a heart-failure blood marker called NT-proBNP.⁷ If this technology matures, it could help doctors intervene while fibrosis is still in progress rather than after scar has fully hardened.

Blood tests for fibrosis are also under investigation. Several circulating biomarkers have been proposed to reflect how much fibrous tissue is accumulating in the heart, but a review in the Journal of the American College of Cardiology found that most of them lack solid proof that they actually track what is happening in the heart muscle itself, as opposed to fibrosis elsewhere in the body.⁸ For now, imaging remains far more reliable than a blood draw for assessing cardiac scar.

Medications That Slow Further Scarring

No pill can dissolve scar tissue that has already formed. What medications can do is slow the biological processes that keep adding new collagen, buying the heart time and preserving whatever healthy muscle remains. The cornerstone drugs for this are the ones already prescribed broadly in heart failure: ACE inhibitors, angiotensin receptor blockers (ARBs), and mineralocorticoid receptor antagonists like spironolactone and eplerenone. These medications target the renin-angiotensin-aldosterone system, a hormonal cascade that, when overactive, drives fibroblasts to produce excess collagen.³ Blocking that cascade doesn’t erase existing scar, but it can meaningfully reduce the rate at which new fibrosis develops.

A newer class of drugs, the SGLT2 inhibitors originally developed for type 2 diabetes, has shown antifibrotic effects in animal models. In rats that had suffered a heart attack, the SGLT2 inhibitor dapagliflozin reduced fibrosis by dampening harmful reactive oxygen species and limiting the infiltration of cells involved in scar formation.⁹ SGLT2 inhibitors are already approved for heart failure regardless of diabetes status, and while their clinical benefits in people are well documented, the specific contribution of their antifibrotic action versus their other effects on the heart is still being worked out.

Surgical and Catheter-Based Procedures

When scar tissue causes a bulge in the heart wall known as an aneurysm, surgery can physically remove the damaged area and reshape the ventricle. One approach involves tailored excision of the scar followed by a linear closure to restore the chamber’s normal geometry. A review of over 100 patients who underwent this type of repair showed acceptable survival rates over more than a decade of follow-up.¹⁰ Another technique, called the Dor procedure, uses a patch to exclude the aneurysm from the chamber. In one case involving a rapidly growing post-infarction aneurysm, surgical ventricular restoration with the Dor technique brought the patient’s ejection fraction from dangerously low levels back up to about 47% at six months, with sustained reverse remodeling confirmed on follow-up MRI.¹¹ These operations are major surgery, but for selected patients with large, well-defined scars that are actively harming heart function, they can be transformative.

Scar tissue is also the primary target in catheter ablation for ventricular tachycardia, a dangerous fast heart rhythm that commonly arises from scarred areas of the heart after a heart attack. The border zone between living muscle and scar is where errant electrical circuits tend to form. In a study mapping the origins of these arrhythmias, about two-thirds of the abnormal circuits were successfully ablated at sites in that border zone, with additional circuits found within the scar itself or on the heart’s outer surface.¹² Ablation doesn’t remove scar, but it destroys the small pockets of tissue within or around the scar that are generating the arrhythmia, reducing the risk of sudden cardiac death.

Mechanical Devices and Ventricular Unloading

Left ventricular assist devices (LVADs) are mechanical pumps implanted to help a failing heart move blood. Their primary job is keeping the patient alive, often as a bridge to transplant, but they also produce an interesting secondary effect: by taking workload off the weakened ventricle, they allow some degree of structural recovery. LVAD support has been linked to partial restoration of ventricular geometry, calcium handling, and metabolic function in the heart muscle.¹³

The relationship between LVADs and fibrosis is more complicated than a simple “helps or hurts” story. One small study found dramatic results: all ten patients had significant reductions in heart tissue collagen content after LVAD placement, with scar area dropping from roughly a third of the tissue to about 4%.¹⁴ However, another investigation found that LVAD unloading actually increased both interstitial and total collagen content, even while it improved blood vessel density in the tissue.¹⁵ The discrepancy probably reflects differences in how long the devices were in place, the underlying cause of heart failure, and how collagen was measured. The takeaway is that mechanical unloading can trigger reverse remodeling, but it doesn’t reliably dissolve scar tissue in every patient.

Exercise and Cardiac Rehabilitation

Structured exercise after a heart attack may be the most accessible intervention for limiting scar-related damage. It won’t shrink an existing scar, but animal studies consistently show that aerobic exercise training after a heart attack reduces harmful remodeling of the ventricle. In rat models of chronic heart failure following infarction, eight weeks of aerobic exercise improved cardiac function, reduced collagen buildup, and decreased the amount of fluid backing up into the lungs.¹⁶ In mice, exercise started before and resumed early after a heart attack reduced both overall collagen content and thinning of the infarcted wall, partly by tamping down inflammation in the damaged area.¹⁷

Translating animal exercise studies to human clinical practice requires caution, since people obviously can’t be randomly assigned to “no exercise” controls the way mice can. Still, cardiac rehabilitation programs that include supervised aerobic training are a standard recommendation after heart attacks and heart failure diagnosis. The evidence strongly supports that these programs improve exercise capacity, quality of life, and cardiovascular outcomes. The mechanism likely involves reduced inflammation, improved blood flow, and a slowing of the fibrotic processes that progressively reshape the heart after injury.

Reprogramming Scar Cells Into Heart Muscle

Perhaps the most ambitious strategy for dealing with cardiac scar is to convert the very cells that make up the scar, fibroblasts, into functioning heart muscle cells. Researchers have identified a cocktail of transcription factors (proteins that control which genes a cell turns on) that can push fibroblasts to take on the identity of beating cardiomyocytes. These reprogrammed cells are called induced cardiac myocytes, or iCMs.¹⁸ The appeal is obvious: the heart already contains a large pool of fibroblasts sitting in the scar, and if even a fraction of them could be reprogrammed in place, the scar would shrink while new contractile tissue appeared.

Additional transcription factors beyond the original three-gene cocktail have been found to boost the efficiency of this conversion in mouse cells.¹⁹ The challenge is that the process remains inefficient, meaning only a small percentage of fibroblasts actually become functional heart cells, and the reprogrammed cells don’t always mature enough to beat in sync with the surrounding heart. This work is still firmly in the laboratory, but it represents a fundamentally different approach: rather than managing scar, it aims to erase it from the inside.

Exosomes and Stem Cell Byproducts

Early attempts at cardiac stem cell therapy focused on injecting living cells into the damaged heart, but results in human trials were mixed. A shift has occurred toward using not the cells themselves but the tiny vesicles they secrete, called exosomes. These nanoscale packages carry proteins, RNA, and signaling molecules that can nudge the heart’s own cells toward repair. Mesenchymal stem cell-derived exosomes can modulate blood vessel growth, reduce inflammation, and limit cell death in injured cardiac tissue.²⁰

An intriguing recent development is the idea of delivering these exosomes through inhalation rather than injection. In a mouse model of heart attack, inhaled stem cell exosomes improved heart pumping function, reduced fibrotic tissue, and promoted the proliferation of heart muscle cells.²¹ An inhaled therapy would be far less invasive than surgery or even catheter delivery, but this work is in its early stages and the leap from mice to humans remains large.

CAR T Cells Targeting Fibrosis

One of the most surprising recent entries in cardiac scar research borrows from cancer immunotherapy. CAR T-cell therapy, famous for its success against certain blood cancers, engineers a patient’s immune cells to recognize and attack a specific target. In the cardiac version, the target is fibroblast activation protein (FAP), the same marker used in the FAPI-PET imaging scans discussed earlier. The idea is to send T cells into the heart that selectively destroy the activated fibroblasts responsible for producing scar tissue.

In a mouse model of hypertensive heart injury, CAR T cells directed against FAP significantly reduced cardiac fibrosis and partially restored both diastolic and systolic heart function.²² A concern with traditional CAR T therapy is that the engineered cells persist in the body, potentially causing off-target damage. To address that, researchers developed a method for generating CAR T cells directly inside the body using lipid nanoparticles carrying modified mRNA. These in-vivo-produced CAR T cells were transient, lasting only as long as the mRNA signal persisted, and still reduced fibrosis and restored cardiac function in mice with heart failure.²³ The transient approach is particularly appealing because you wouldn’t want immune cells permanently attacking fibroblasts throughout the body, since fibroblasts serve important roles in wound healing everywhere.

Conventional therapies have largely failed to halt or reverse established cardiac fibrosis, which is precisely why the early CAR T results have generated such excitement.²⁴ Human trials are being planned, though significant hurdles remain around safety, dosing, and ensuring the treatment targets heart fibroblasts specifically rather than fibroblasts in other organs.

Injectable Biomaterials and Conductive Scaffolds

Another strategy sidesteps the biology-first approach entirely and focuses on the physical problem: scar tissue is stiff, thin, and electrically insulating. Injectable hydrogels can be delivered directly into a scarred area to mechanically bulk up the weakened wall. Even acellular hydrogels, ones that carry no drugs or cells, have been shown to thicken the heart wall after injection, reducing the abnormal stresses that cause the ventricle to stretch out of shape.²⁵

More advanced versions of these hydrogels are being designed to restore electrical conduction across the scar as well. One recent formulation combines collagen, hyaluronic acid, bacterial cellulose, and gold nanoparticles to create an injectable, self-healing, conductive scaffold. In laboratory tests, human stem cells grown on this material generated measurable electrical beats, suggesting the hydrogel could act as a bridge for electrical signals across an otherwise insulating scar.²⁶ A separate study demonstrated that implanting a conductive biopolymer patch onto scarred heart tissue could correct conduction blockages and resynchronize contraction in animal models.¹ These biomaterials-based approaches could eventually complement or replace electronic pacemakers for certain types of conduction problems caused by scarring.

Gene Therapy and the Translation Gap

Gene therapy offers yet another angle: delivering genetic instructions directly into heart cells to promote repair, grow new blood vessels, or protect surviving muscle from further damage. Approaches tested in animals include inserting genes that trigger blood vessel growth in the scar zone, genes that reduce cell death during injury, and reprogramming factors that push fibroblasts toward a cardiac muscle identity. Preclinical results have been promising across several of these strategies.²⁷

The honest picture, though, is that translating these results from animals to humans has been inconsistent. The reasons are instructive: getting a high enough concentration of the gene product to the right spot in a full-sized human heart is harder than in a mouse heart; the delivery vehicles (viruses or nanoparticles) don’t always reach the target efficiently; and the molecular pathways driving fibrosis in people are not identical to those in rodent models.²⁷ Gene therapy for cardiac scar is real science with real potential, but it remains years away from routine clinical use.

Why Some Animals Can Do What Humans Cannot

If all of this sounds like scientists are working hard to recreate something that should be natural, that’s because some animals already do it effortlessly. Zebrafish can regenerate large portions of their heart after injury, replacing damaged tissue with new muscle rather than scar. This makes zebrafish a valuable model for understanding which genetic and cellular switches need to be flipped to enable heart regeneration.²⁸ Newborn mice also show a brief window of regenerative capacity that is lost within the first week of life. The human heart has a vanishingly small rate of cardiomyocyte turnover in adulthood, far too slow to replace a scar. Much of the regenerative medicine research described above is, at its core, an attempt to reactivate pathways that evolution switched off in adult mammals.

Studying these regenerative species has already informed several therapeutic strategies. The transcription factor cocktails used for direct reprogramming, the growth factors deployed in gene therapy, and even the signaling molecules packaged in exosomes all draw on knowledge gained from animals that naturally rebuild their hearts. The gap between a zebrafish and a human patient is enormous, but each new discovery in regenerative biology narrows it slightly, offering a roadmap for therapies that could eventually do more than manage scar tissue and instead replace it.