Developing mechanical hearts, also known as artificial hearts, is indeed a complex and challenging task. While significant progress has been made in the field of cardiac devices, there are several reasons why long-term success has been difficult to achieve:

1. **Biocompatibility:** Mechanical hearts need to be made from materials that are compatible with the human body to minimize the risk of immune response or blood clotting. Finding suitable materials that can withstand the stresses of pumping blood continuously and interact with the body without causing adverse reactions is a significant challenge.

2. **Power source:** Mechanical hearts require a reliable and compact power source to function. Currently, most mechanical hearts are powered by external systems through cables that pass through the skin. These systems have limitations in terms of mobility, infection risk, and inconvenience for the patient.

3. **Wear and tear:** The continuous pumping action of a mechanical heart creates significant wear and tear on the device over time. Friction, stress, and mechanical failure can occur, leading to device malfunction or failure.

4. **Blood compatibility:** Mechanical hearts need to handle blood flow without damaging blood cells or causing excessive turbulence. Designing the pump mechanisms to mimic the natural flow and prevent complications such as hemolysis (rupturing of red blood cells) is a significant challenge.

5. **Size and fit:** Mechanical hearts need to be appropriately sized and fitted within the patient's chest cavity. Achieving a suitable size and fit while considering the anatomical variations among individuals is a complex engineering and surgical challenge.

Regarding the lifespan of current mechanical hearts, the couple of months you mentioned may not reflect the typical duration. In recent years, advancements have been made in mechanical heart technology, and some devices have achieved survival rates beyond two years. However, long-term durability remains a challenge, with the goal of achieving mechanical hearts that can function for 10+ years.

Researchers and engineers are actively working on addressing these challenges. Ongoing advancements in materials science, miniaturization of components, improved power sources, and better understanding of the biomechanics of the heart are paving the way for more durable and effective mechanical hearts. While there is no definitive timeline, it is indeed possible that future developments will lead to mechanical hearts that can function for extended periods of time, significantly improving the quality of life and survival rates for patients with heart failure.
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