Sam Lee offers an informative guide to pioneering advancements in heart treatments.
What is Heart Failure?
Heart failure occurs when the volume of blood pumped out by the heart is insufficient to meet the body’s requirements. Currently, heart failure affects 920,000 people in the UK, with 200,000 new diagnoses being made each year. Unfortunately, half of those diagnosed will die within five years.
The left side of the heart pumps blood from the lungs to the rest of the body, therefore leftsided heart failure (which is more common than right-sided) creates a backlog of blood into the lungs. This increases the pressure within the blood vessels and results in fluid leaking out into the lungs pulmonary oedema.
This reduces the efficiency by which oxygen enters the blood from the lungs, leading to shortness of breath, fatigue, and difficulty breathing at night while lying down.
What is the Current Treatment for Heart Failure?
Treatment involves using medication to offload the fluid (diuretics), decrease blood pressure (ACE inhibitors), and reduce heart rate (beta blockers). However, sufferers will eventually deteriorate, necessitating more radical treatment in the form of heart transplants or artificial devices. Over 50 years on from the first heart transplant in 1967, roughly 4,000 such procedures are carried out annually worldwide.
With an average waiting time of three years for a heart transplant in the UK, human donors are unable to fully meet the transplant demand from heart failure patients, let alone other cardiac conditions. Additionally, transplants are fraught with complications and by 30 years postoperation, only 16% of patients are still alive, with the average survival time being 11 years. Clearly, alternatives are required.
A New Paradigm?
There are two main types of artificial devices: ventricular assist devices (VADs) and total artificial hearts. VADs take over the function of the failing heart chambers and have traditionally been used as a “bridge to transplant” keeping the patient alive until a donor heart is found. Recently, UK guidelines have changed to support VADs as a “destination therapy” permanent alternatives to transplants. Total artificial hearts were first trialled as a “bridge” in 1969, then as a “destination” in 1982, with the patient living for 112 days posttransplant, albeit with a poor quality of life. Usage of total artificial hearts has increased since their inception, and in 2013, the number of artificial device implants overtook the number of heart transplants carried out in North America.
Despite advances made in transplants and medical devices, the mortality rate remains high. Recent efforts surrounding transplants have focused on: reducing the risk of rejection by modifying the patient’s immune system; increasing the number of eligible donors; and improving access to donor hearts. However, with new heart failure diagnoses outstripping the transplant provision, there is a limit to the contribution that transplants can make to the treatment of heart failure.
VADs are not without significant drawbacks. Devices can weigh up to 500 grams and require an external battery pack or air compressor to operate, the weight (~1kg) and limited battery life (~12 hours) of which are both areas for future optimisation.
VADs and artificial hearts also risk triggering the formation of blood clots, which can travel to the brain and cause strokes. Usually, patients take long term medication to reduce clot formation.
However, recent trials have been carried out to line the surfaces of such devices with biological tissue in order to reduce the risk of clotting and the need to take long term medication.
But, as mortality reduces, several ethical questions are raised. With VAD implantation costing the NHS £91,000 per device, will such devices become the domain of the wealthy in societies without access to universal healthcare? Indeed, who has the right to switch off such devices if further treatment is deemed to be futile?
As the treatment of heart failure changes, the public’s perception of death and dying must also change. While science can solve the practical, it is now up to society to address the ethical for science is not absolute, it can only go so far.
From SATNAV Issue 23, pages 20-21.