Tissue or Mechanical Heart Valve?
Mechanical and Tissue Heart Valves
Background:
When heart valve disease progresses to the point that
treatment by medicines does not provide relief from a
patient’s symptoms, surgery to repair or replace the valves
becomes the best alternative. If the surgery is not a repair,
homograft or autograft, the choice is most likely between
carbon-based mechanical valves and biological tissue
valves.
The physician and patient will choose the type of valve,
taking into account the patients’ overall condition and
preference. Some of the patient factors considered are:
Age and life expectancy: Although age is not a rigid
indicator, the American College of Cardiology and
American Medical Association guidelines indicate that
mechanical valves are generally appropriate for a
majority of patients 65 years old and younger, or
patients already on coumadin.
Other diseases: Lung, liver and kidney disease,
diabetes, cancer and other chronic conditions can affect
life expectancy and alter the age criterion.
Heart and vascular system condition: Coronary, carotid
and peripheral artery diseases and heart rhythm
disturbances can affect valve selection.
Patient lifestyle and preference: Life situations or
intangible factors often influence valve selection.
Tissue Heart Valves:
Tissue valves are harvested from pig heart valves (porcine)
or cow heart sac (bovine). These tissues are treated and
neutralized so that the body will not reject them. Some are
mounted on a frame or stent; others are used directly
(stentless).
The lifetime of a tissue valve is typically 10 to 15 years,
often less in younger patients. Over this time the valve will
likely be degenerating to the point of requiring replacement.
Because valve replacement surgery carries a significant
risk of death, patient life expectancy is a major criterion in
considering a tissue valve.
With relatively high pressure gradients, stented tissue
valves do not perform as well as the native valve in terms of
blood flow. Tissue valves without frames (stentless)
improve blood flow, although they are more difficult to put
in place and are not usable in all cases.
The primary advantage of tissue valves is their lower
requirement for anticoagulation therapy, which reduces the
incidence of bleeding. For the majority of tissue valve
patients, taking an aspirin a day is sufficient
anticoagulation therapy. Many patients with tissue valves,
however, do not enjoy this benefit due to anticoagulation
requirements for other heart or vascular conditions.
Mechanical Heart Valves:
The most widely used mechanical valves are made from
pyrolytic carbon, which has been used for over 30 years.
Most are bileaflet designs, meaning that they employ two
carbon “leaflets” to regulate flow to a single direction.
The primary advantage of mechanical valves is that they
will last a patient’s lifetime. Mechanical valves are
preferred for patients with life expectancies beyond 10-15
years because they eliminate the mortality risk inherent in
the replacement of a worn out tissue valve. The best
mechanical valves, such as the On-X valve, have excellent
flow performance, rivaling that of the native valve even in
the small sizes.
The main drawback of mechanical valves has been their
requirement for warfarin anticoagulation therapy, with its
accompanying risk of bleeding. Bleeding events are rare but
are potentially fatal. With properly managed anticoagulation
therapy, rates are low for both bleeding and clotting.
Mechanical valves can sometimes be audible when opening
and closing. The sound level varies with the patient, but
among those noticing it, a small number of patients find the
sound disturbing, while others find it reassuring.
The Choice:
Valve selection is a balancing act between the major
positives and negatives of both valve types:
The limited durability of tissue valves (performance
degradation and the stress or mortality of reoperation).
The requirement for lifelong anticoagulation therapy of
mechanical valves.
The decision is reached differently for each patient as many
factors are considered and weighed but the goal is always
to improve quality of life while minimizing risk.
Mechanical and Tissue Heart Valves
Background:
When heart valve disease progresses to the point that
treatment by medicines does not provide relief from a
patient’s symptoms, surgery to repair or replace the valves
becomes the best alternative. If the surgery is not a repair,
homograft or autograft, the choice is most likely between
carbon-based mechanical valves and biological tissue
valves.
The physician and patient will choose the type of valve,
taking into account the patients’ overall condition and
preference. Some of the patient factors considered are:
Age and life expectancy: Although age is not a rigid
indicator, the American College of Cardiology and
American Medical Association guidelines indicate that
mechanical valves are generally appropriate for a
majority of patients 65 years old and younger, or
patients already on coumadin.
Other diseases: Lung, liver and kidney disease,
diabetes, cancer and other chronic conditions can affect
life expectancy and alter the age criterion.
Heart and vascular system condition: Coronary, carotid
and peripheral artery diseases and heart rhythm
disturbances can affect valve selection.
Patient lifestyle and preference: Life situations or
intangible factors often influence valve selection.
Tissue Heart Valves:
Tissue valves are harvested from pig heart valves (porcine)
or cow heart sac (bovine). These tissues are treated and
neutralized so that the body will not reject them. Some are
mounted on a frame or stent; others are used directly
(stentless).
The lifetime of a tissue valve is typically 10 to 15 years,
often less in younger patients. Over this time the valve will
likely be degenerating to the point of requiring replacement.
Because valve replacement surgery carries a significant
risk of death, patient life expectancy is a major criterion in
considering a tissue valve.
With relatively high pressure gradients, stented tissue
valves do not perform as well as the native valve in terms of
blood flow. Tissue valves without frames (stentless)
improve blood flow, although they are more difficult to put
in place and are not usable in all cases.
The primary advantage of tissue valves is their lower
requirement for anticoagulation therapy, which reduces the
incidence of bleeding. For the majority of tissue valve
patients, taking an aspirin a day is sufficient
anticoagulation therapy. Many patients with tissue valves,
however, do not enjoy this benefit due to anticoagulation
requirements for other heart or vascular conditions.
Mechanical Heart Valves:
The most widely used mechanical valves are made from
pyrolytic carbon, which has been used for over 30 years.
Most are bileaflet designs, meaning that they employ two
carbon “leaflets” to regulate flow to a single direction.
The primary advantage of mechanical valves is that they
will last a patient’s lifetime. Mechanical valves are
preferred for patients with life expectancies beyond 10-15
years because they eliminate the mortality risk inherent in
the replacement of a worn out tissue valve. The best
mechanical valves, such as the On-X valve, have excellent
flow performance, rivaling that of the native valve even in
the small sizes.
The main drawback of mechanical valves has been their
requirement for warfarin anticoagulation therapy, with its
accompanying risk of bleeding. Bleeding events are rare but
are potentially fatal. With properly managed anticoagulation
therapy, rates are low for both bleeding and clotting.
Mechanical valves can sometimes be audible when opening
and closing. The sound level varies with the patient, but
among those noticing it, a small number of patients find the
sound disturbing, while others find it reassuring.
The Choice:
Valve selection is a balancing act between the major
positives and negatives of both valve types:
The limited durability of tissue valves (performance
degradation and the stress or mortality of reoperation).
The requirement for lifelong anticoagulation therapy of
mechanical valves.
The decision is reached differently for each patient as many
factors are considered and weighed but the goal is always
to improve quality of life while minimizing risk.
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