Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-03-30
2004-07-20
Bockelman, Mark (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C600S509000
Reexamination Certificate
active
06766189
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a method and apparatus for administering stimulation therapy for heart disease and, more particularly, to a method and apparatus for predicting acute response to cardiac resynchronization therapy.
BACKGROUND
The heart is a muscular organ comprising multiple chambers that operate in concert to circulate blood throughout the body's circulatory system. As shown in
FIG. 1
, the heart
100
includes a right-side portion or pump
102
and a left-side portion or pump
104
. The right-side portion
102
includes a right atrium
106
and a right ventricle
108
. Similarly, the left-side portion
104
includes a left atrium
110
and a left ventricle
112
. Oxygen-depleted blood returning to the heart
100
from the body collects in the right atrium
106
. When the right atrium
106
fills, the oxygen-depleted blood passes into the right ventricle
108
where it can be pumped to the lungs (not shown) via the pulmonary arteries
117
. Within the lungs, waste products (e.g., carbon dioxide) are removed from the blood and expelled from the body and oxygen is transferred to the blood. Oxygen-rich blood returning to the heart
100
from the lungs via the pulmonary veins (not shown) collects in the left atrium
110
. The circuit between the right-side portion
102
, the lungs, and the left atrium
110
is generally referred to as the pulmonary circulation. When the left atrium
110
fills, the oxygen-rich blood passes into the left ventricle
112
where it can be pumped throughout the entire body. In so doing, the heart
100
is able to supply oxygen to the body and facilitate the removal of waste products from the body.
To circulate blood throughout the body's circulatory system as described above, a beating heart performs a cardiac cycle that includes a systolic phase and a diastolic phase. During the systolic phase (e.g., systole), the ventricular muscle cells of the right and left ventricles
108
,
112
contract to pump blood through the pulmonary circulation and throughout the body, respectively. Conversely, during the diastolic phase (e.g., diastole), the ventricular muscle cells of the right and left ventricles
108
,
112
relax, during which the right and left atriums
106
,
110
contract to force blood into the right and left ventricles
108
,
112
, respectively. Typically, the cardiac cycle occurs at a frequency between 60 and 100 cycles per minute and can vary depending on physical exertion and/or emotional stimuli, such as, pain or anger.
The contractions of the muscular walls of each chamber of the heart
100
are controlled by a complex conduction system that propagates electrical signals to the heart muscle tissue to effectuate the atrial and ventricular contractions necessary to circulate the blood. As shown in
FIG. 2
, the complex conduction system includes an atrial node
120
(e.g., the sinoatrial node) and a ventricular node
122
(e.g., the atrioventricular node). The sinoatrial node
120
initiates an electrical impulse that spreads through the muscle tissues of the right and left atriums
106
,
110
and the atrioventricular node
122
. As a result, the right and left atriums
106
,
110
contract to pump blood into the right and left ventricles
108
,
112
as discussed above. At the atrioventricular node
122
, the electrical signal is momentarily delayed before propagating through the right and left ventricles
108
,
112
. Within the right and left ventricles
108
,
112
, the conduction system includes right and left bundles branches
126
,
128
that extend from the atrioventricular node
122
via the Bundle of His
124
. The electrical impulse spreads through the muscle tissues of the right and left ventricles
108
,
112
via the right and left bundle branches
126
,
128
, respectively. As a result, the right and left ventricles
108
,
112
contract to pump blood throughout the body as discussed above.
Normally, the muscular walls of each chamber of the heart
100
contract synchronously in a precise sequence to efficiently circulate the blood as described above. In particular, both the right and left atriums
106
,
110
contract (e.g., atrial contractions) and relax synchronously. Shortly after the atrial contractions, both the right and left ventricles
108
,
112
contract (e.g., ventricular contractions) and relax synchronously. Several disorders or arrhythmias of the heart can prevent the heart from operating normally, such as, blockage of the conduction system, heart disease (e.g., coronary artery disease), abnormal heart valve function, or heart failure.
Blockage in the conduction system can cause a slight or severe delay in the electrical impulses propagating through the atrioventricular node
122
, causing inadequate ventricular relations and filling. In situations where the blockage in the ventricles (e.g., the right and left bundle branches
126
,
128
), the right and/or left ventricles
108
,
112
can only be excited through slow muscle tissue conduction. As a result, the muscular walls of the affected ventricle (
108
and/or
112
) do not contract synchronously (e.g., asynchronous contraction), thereby, reducing the overall effectiveness of the heart
100
to pump oxygen-rich blood throughout the body. For example, asynchronous contraction of the left ventricular muscles can degrade the global contractility (e.g., the pumping power) of the left ventricle
112
which can be measured by the peak ventricular pressure change during systole (denoted as “LV+dp/dt”). A decrease in LV+dp/dt corresponds to a worsened pumping efficiency.
Similarly, heart valve disorders (e.g., valve regurgitation or valve stenosis) can interfere with the heart's
100
ability to pump blood, thereby, reducing stroke volume (i.e., aortic pulse pressure) and/or cardiac output.
Various medical procedures have been developed to address these and other heart disorders. In particular, cardiac resynchronization therapy (“CRT”) can be used to improve the conduction pattern and sequence of the heart. CRT involves the use of an artificial electrical stimulator that is surgically implanted within the patient's body. Leads from the stimulator can be affixed at a desired location within the heart to effectuate synchronous atrial and/or ventricular contractions. Typically, the location of the leads (e.g., stimulation site) is selected based upon the severity and/or location of the blockage. Electrical stimulation signals can be delivered to resynchronize the heart, thereby, improving cardiac performance.
Despite these advantages, several shortcomings exist that limit the usefulness of CRT. For example, results from many clinical studies have shown that hemodynamic response to CRT typically varies from patient to patient, ranging from very positive (e.g., improvement) to substantially negative (e.g., deterioration). Additionally, hemodynamic response can also vary based upon the stimulation site used to apply CRT. Thus, in order to predict acute hemodynamic benefit from CRT, the patient typically must be screened prior to receiving the therapy and the actual stimulation site used to apply CRT should be validated for each patient. Existing methods that predict acute hemodynamic response to CRT are, therefore, patient specific. Furthermore, while some existing techniques and/or procedures can predict whether a specific patient will derive an acute hemodynamic benefit from CRT, they are unable to determine or validate that a specific stimulation site will produce a positive hemodynamic response from CRT.
Improvements in methods used to predict acute responses to CRT are, therefore, sought.
SUMMARY
In general terms, the present disclosure relates to a method and apparatus for administering stimulation therapy for heart disease. More particularly, the present disclosure relates to a method and apparatus for predicting acute response to cardiac resynchronization therapy. In one aspect of the disclosure, the method for predicting acute responses to cardiac resynchronization therapy can comprise meas
Auricchio Angelo
Ding Jiang
Spinelli Julio
Yu Yinghong
Bockelman Mark
Cardiac Pacemakers Inc.
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