Introduction: The Need for Temporary Cardiac Solutions

Cardiovascular disease remains the leading cause of death globally, claiming an estimated 17.9 million lives each year. Traditional cardiac devices—stents, pacemaker leads, heart valves, and vascular grafts—are designed for permanent implantation. While life-saving, these permanent implants carry long-term risks: chronic inflammation, fibrosis, infection, device migration, and the need for revision surgeries. In pediatric patients, permanent devices become obsolete as the patient grows, necessitating multiple replacement procedures. The growing recognition of these limitations has driven a paradigm shift toward biodegradable materials that provide temporary structural or electrical support and then safely degrade in the body, eliminating the need for surgical removal and reducing long-term complications.

Biodegradable cardiac devices represent a convergence of materials science, bioengineering, and cardiovascular medicine. By engineering materials that resorb in a controlled manner, researchers aim to harness the body’s natural healing processes while minimizing foreign body response. This article explores the emerging classes of biodegradable materials—synthetic polymers, metals, and natural biopolymers—their applications in temporary cardiac devices, current clinical progress, and the challenges that remain before widespread adoption.

The Rationale for Biodegradable Cardiac Devices

Permanent cardiac implants, though effective, impose a lifelong burden. Stents remain in the artery indefinitely, posing risks of late stent thrombosis and neoatherosclerosis. Pacemaker leads introduce a foreign body that can cause venous occlusion, lead fracture, or infection—often requiring extraction procedures that carry significant morbidity. For patients needing only short-term mechanical support—such as after a myocardial infarction or during recovery from cardiac surgery—a temporary, resorbable device would be ideal.

Biodegradable materials offer several compelling advantages:

  • Elimination of secondary interventions: No need for surgical removal, reducing hospital stays, costs, and procedural risks.
  • Reduced long-term inflammation: As the material degrades, the foreign body stimulus subsides, allowing the tissue to return to a more natural state.
  • Potential for drug delivery: Biodegradable matrices can be loaded with anti-inflammatory or pro-healing agents that release as the device degrades.
  • Tissue regeneration scaffold: In cardiac tissue engineering, a biodegradable scaffold provides temporary mechanical support while encouraging cell infiltration and extracellular matrix deposition.

These benefits have spurred intense research into materials that balance mechanical performance, degradation kinetics, biocompatibility, and manufacturing scalability.

Types of Emerging Biodegradable Materials

A wide range of materials are under investigation for temporary cardiac devices. They can be broadly categorized into synthetic polymers, biodegradable metals, and natural biopolymers. Each class offers distinct advantages and trade-offs.

Synthetic Polymers

Synthetic biodegradable polymers are the most extensively studied class for temporary cardiac implants. Their key attraction is the ability to precisely tune degradation rates, mechanical properties, and drug release profiles through copolymer chemistry and molecular weight.

Polylactic acid (PLA) and polyglycolic acid (PGA) are the workhorses of the field. PLA degrades slowly (over 1–3 years) and maintains strength for months, making it suitable for stents that must support the vessel during remodeling. PGA degrades faster (weeks to months) and is often copolymerized with PLA to form PLGA (poly(lactic-co-glycolic acid)). PLGA degradation rate can be tuned by varying the lactide:glycolide ratio, offering timelines from weeks to over a year. PLGA has been used in drug-eluting bioresorbable vascular scaffolds and shows excellent biocompatibility.

Polycaprolactone (PCL) degrades very slowly (>2 years) and is often blended with faster-degrading polymers to adjust properties. For cardiac applications, PCL has been explored in long-term support devices where a gradual transition of load to the healing tissue is desired.

Among the most successful clinical products based on synthetic polymers is the Absorb BVS (bioresorbable vascular scaffold) by Abbott, made from poly(L-lactide) (PLLA). Although commercial challenges arose, the platform demonstrated the feasibility of a fully resorbable stent in the coronary arteries. Later iterations, such as the Magmaris scaffold (Biotronik), combine a magnesium backbone with a PLGA coating, leveraging both metallic and polymer properties.

Biodegradable Metals

Biodegradable metals offer superior mechanical strength compared to polymers, making them attractive for load-bearing applications such as stents, orthopaedic implants, and temporary cardiac closure devices.

Magnesium alloys have been at the forefront. Magnesium is essential for human metabolism and degrades via corrosion in the physiological environment, producing Mg²⁺ ions that are safely excreted. Early challenges of rapid degradation and hydrogen gas accumulation have been addressed by alloying with rare earth elements (e.g., WE43 alloy) and surface coatings. The Magmaris scaffold is a second-generation magnesium-based bioresorbable stent that showed promising clinical results with complete resorption within 12 months.

Zinc-based alloys have emerged as a more recent alternative. Zinc degrades slower than magnesium, matching the healing timeline of arteries more closely (12–24 months), and its corrosion products are generally biocompatible. Research has focused on Zn-Mg and Zn-Cu alloys to improve mechanical strength and ductility. Preclinical studies in porcine models show favorable healing and minimal inflammation.

Iron-based alloys have also been explored for their high mechanical strength, but their extremely slow degradation rate (years) and potential for chronic inflammation have limited clinical translation. Newer iron-manganese alloys and composite approaches aim to accelerate degradation while maintaining biocompatibility.

Natural Biopolymers

Natural biopolymers such as silk fibroin, derived from silkworms, offer excellent biocompatibility, tunable degradation (via processing), and mechanical properties suitable for cardiac tissue engineering. Silk fibroin has been used to fabricate microporous scaffolds for myocardial patches, showing good cell attachment and neovascularization. Its degradation byproducts are amino acids that are metabolized harmlessly.

Collagen and gelatin are other natural polymers widely used in hydrogel-based cardiac patches. Their main limitation is poor mechanical strength, often requiring crosslinking or combination with synthetic polymers. Chitosan, derived from chitin, is being investigated for its antibacterial properties and ability to deliver growth factors for cardiac repair.

Applications in Temporary Cardiac Devices

Biodegradable materials are being applied across a spectrum of cardiac devices, each with unique material requirements.

Bioresorbable Stents for Coronary Artery Disease

Bioresorbable stents (BRS) are the flagship application. Unlike permanent metal stents that remain in the artery forever, BRS provide temporary scaffolding to prevent early recoil and then degrade, allowing the vessel to regain natural vasomotion and reducing the risk of late adverse events. First-generation BRS using PLLA (Absorb) suffered from higher rates of device-related thrombosis due to thicker struts and incomplete endothelialization. Second-generation BRS use thinner struts, improved polymers, or magnesium alloys (Magmaris), resulting in better outcomes. Ongoing clinical trials are evaluating next-generation fully polymeric stents with faster resorption and better deliverability.

Recent meta-analyses indicate that with improved patient selection and deployment techniques, BRS can achieve comparable safety to drug-eluting stents while offering the benefit of a foreign-body-free vessel after resorption.

Temporary Pacemaker Leads and Electrodes

Traditional permanent pacemaker leads are associated with long-term complications such as lead fracture, infection, and venous obstruction. For patients needing only short-term pacing—for example, after heart surgery or as a bridge to recovery—biodegradable leads could eliminate the need for extraction. Researchers have developed silk fibroin-based leads with electrodes that dissolve after weeks, as well as Zn-Mn alloy wires that conduct electricity and degrade safely. A landmark 2021 study demonstrated a fully bioresorbable pacemaker device that wirelessly powers itself, degrades completely, and avoids the need for a second surgery. This opens the door to temporary cardiac electrotherapy for infections, post-surgical recovery, or pediatric applications where the device would be outgrown.

Cardiac Patches and Scaffolds for Tissue Engineering

For patients with damaged myocardium (e.g., after a heart attack), biodegradable scaffolds provide temporary mechanical support and a substrate for cell delivery or host cell infiltration. Silk fibroin and collagen-GAG scaffolds have been tested in preclinical models, showing improved ventricular function and reduced scar formation. Some patches incorporate microgrooved surfaces to direct cell alignment and electrical conductivity. The ideal scaffold degrades at a rate that matches the formation of new functional tissue—typically several months. Recent work on composite PLGA-silk scaffolds demonstrates enhanced mechanical properties and controlled degradation for cardiac applications.

Key Properties and Degradation Mechanisms

The success of a biodegradable cardiac device hinges on a delicate balance of properties. Degradation must be predictable and controllable: too fast, and the device fails prematurely; too slow, and it behaves like a permanent implant, defeating the purpose. For polymers, degradation proceeds via hydrolysis (and sometimes enzymatic cleavage), breaking long chains into oligomers and monomers that are metabolized or excreted. For metals, corrosion occurs through electrochemical reactions, producing metal ions that are transported and cleared by the body.

Mechanical integrity must be maintained during the required support period. For a coronary stent, this is typically 3–6 months, during which the vessel remodels. The material must also maintain sufficient radial strength to prevent recoil without being too bulky. Surface modifications—such as drug-eluting coatings, passivation layers, or microtexturing—can modulate degradation, improve biocompatibility, or deliver therapeutic agents.

Biocompatibility is paramount. Degradation products must not provoke excessive inflammation, cytotoxicity, or thrombosis. For magnesium alloys, local alkalinity and hydrogen gas release need to be managed. For synthetic polymers, lactic acid (from PLA) can lower local pH, potentially causing inflammation if concentration is high. Copolymer ratios, scaffold architecture, and perfusion are used to mitigate these effects.

Clinical Trials and Regulatory Approvals

The path from bench to bedside for biodegradable cardiac devices has been gradual but accelerating. The first CE-marked bioresorbable stent was the Absorb BVS (Abbott), approved in Europe in 2011. While initially successful, longer-term registry data showed higher rates of scaffold thrombosis compared to drug-eluting metal stents, leading to Abbott's decision to discontinue sales in 2017. However, this paved the way for improved designs.

The Magmaris magnesium-based stent (Biotronik) received CE mark in 2016 for the treatment of coronary de novo lesions. Clinical studies, such as the BIOSOLVE-II and -IV, demonstrated excellent safety and efficacy outcomes with very low rates of cardiac death and scaffold thrombosis at 3-year follow-up. Magmaris represents a hybrid approach: a magnesium backbone with a PLGA coating that elutes sirolimus. The device resorbs completely in about 12 months, restoring vessel patency and flexibility.

For temporary pacemakers, clinical translations are earlier stage. The fully resorbable pacemaker reported in Nature in 2021 has not yet entered human trials but represents a proof-of-concept that has attracted significant attention. Other preclinical devices have been tested in small and large animal models with promising results for leadless, biodegradable pacing systems.

Regulatory bodies such as the FDA and EMA have issued guidance documents for bioresorbable medical devices, emphasizing the need for long-term follow-up to confirm degradation and late safety. The European Society of Cardiology has also provided position papers on the use of BRS.

Current Challenges and Ongoing Research

Despite progress, several hurdles remain before biodegradable cardiac devices become routine clinical tools.

Controlled and Predictable Degradation

Individual patient variability—in pH, enzyme activity, blood flow, and tissue composition—can lead to inconsistent degradation. Researchers are developing smart coatings that respond to local stimuli (e.g., pH or temperature) to modulate degradation. Another approach is to design composite materials with multiple degradation phases, providing a predictable loss of mechanical strength.

Mechanical Performance

Biodegradable polymers generally have lower strength than permanent metals like cobalt-chromium. This forces thicker struts in stents, which increases thrombogenicity risk. New high-strength polymers and oriented crystallization methods are being explored to achieve thinner struts without sacrificing radial strength. For magnesium alloys, improving fatigue resistance and ductility remains a priority.

Immune and Inflammatory Response

Even biocompatible materials can elicit foreign body reactions during degradation. Macrophage-mediated inflammation may hinder tissue healing. Researchers are incorporating immunomodulatory drugs—such as everolimus, sirolimus, or rapamycin—into the device coatings to dampen inflammation without compromising degradation. Clinical studies on drug-eluting BRS indicate that such coatings are effective in reducing restenosis and inflammation.

Manufacturing Scalability and Cost

Producing biodegradable devices with consistent quality and at large scale is challenging. Polymers are sensitive to processing conditions (temperature, shear), and metal alloys require precise casting and extrusion. Additive manufacturing (3D printing) offers the potential for patient-specific implants with controlled porosity and degradation profiles, but regulatory approval and cost remain barriers. Advancements in 3D-printed bioresorbable scaffolds are being reported, but clinical adoption is still nascent.

Future Directions

The next decade will likely see biodegradable cardiac devices become more sophisticated. Key emerging trends include:

  • Smart responsive materials: Hydrogels or polymers that change properties in response to mechanical stress, pH, or enzymatic activity, enabling adaptive support.
  • Therapeutic integration: Devices acting as both a scaffold and a drug delivery depot, releasing anti-proliferative, anti-inflammatory, or pro-angiogenic agents at controlled rates.
  • Multifunctional composites: Combining a metallic core for strength with a polymer shell for drug elution and tailored degradation.
  • Patient-specific customization: Using imaging and computational modeling to design devices with degradation profiles matching an individual's healing timeline.
  • Wireless and battery-free functionality: For temporary electronic devices like pacemakers, integrating bioresorbable batteries and wireless power transfer will be a major leap forward.

Collaborations between materials scientists, cardiologists, and regulatory agencies will be essential to accelerate translation. As manufacturing techniques improve and long-term clinical data accumulate, biodegradable cardiac devices could become the standard of care for many indications, reducing the burden of permanent implants and improving patient quality of life.

Conclusion

Emerging biodegradable materials—synthetic polymers like PLGA, biodegradable metals like magnesium and zinc alloys, and natural biopolymers like silk fibroin—are reshaping the landscape of temporary cardiac devices. From bioresorbable stents that restore vasomotion to dissolvable pacemaker leads that eliminate extraction procedures, these materials promise to reduce long-term complications and align with the body's natural healing. While challenges in degradation control, mechanical strength, and manufacturing persist, ongoing research and clinical progress are steadily overcoming them. The future of cardiac care is moving toward temporary, biocompatible, and smart devices that heal with the patient and then disappear—leaving only healthy tissue behind.