Methods and systems for lowering blood pressure through reduction of ventricle filling
Systems and methods for reducing ventricle filling volume are disclosed. In some embodiments, a stimulation circuit may be used to stimulate a patient's heart to reduce ventricle filling volume or even blood pressure. When the heart is stimulated at a consistent rate to reduce blood pressure, the cardiovascular system may over time adapt to the stimulation and revert back to the higher blood pressure. In some embodiments, the stimulation pattern may be configured to be inconsistent such that the adaptation response of the heart is reduced or even prevented. In some embodiments, a stimulation circuit may be used to stimulate a patient's heart to cause at least a portion of an atrial contraction to occur while the atrioventricular valve is closed. Such an atrial contraction may deposit less blood into the corresponding ventricle than when the atrioventricular valve is opened throughout an atrial contraction.
1. A method, carried out with an implanted heart muscle stimulator associated with a heart of a patient, for treating a blood pressure disorder in the patient, the patient having a pretreatment blood pressure, the method comprising:
determining a future anticipated contraction of an atrium of the heart;
delivering, to a ventricle of the heart associated with the atrium, one or more stimulation pulses a pacing time interval before the future anticipated contraction of the atrium, such that the ventricle begins contracting before the future anticipated contraction of the atrium begins; and
reducing blood pressure of the patient to below the pretreatment blood pressure by at least one of reduced ventricular filling or increased atrial stretch.
2. The method of claim 1 , further comprising delivering to the atrium one or more stimulation pulses after the pacing time interval to cause the future anticipated contraction of the atrium.
3. The method of claim 2 , further comprising sensing atrial excitation to confirm that the one or more stimulation pulses delivered to the atrium are delivered before a natural excitation of the atrium takes place.
4. The method of claim 1 , further comprising allowing the future anticipated contraction of the atrium to occur naturally without stimulation.
5. The method of claim 1 , further comprising:
sensing a natural activity rate of the atrium; and
setting the pacing time interval preceding the future anticipated contraction of the atrium based on the sensed natural activity rate.
6. The method of claim 1 , further comprising:
sensing atrial excitation to determine onset of atrial excitation;
determining a sensing delay interval as a duration from the onset of atrial excitation to when the atrial excitation is sensed; and
determining, based on the sensing delay interval, the pacing time interval preceding the future anticipated contraction of the atrium.
7. The method of claim 6 , wherein estimating the sensing delay interval comprises modifying the sensing delay interval until a resulting effect on blood pressure is equal to an effect obtained by pacing both the atrium and the ventricle with a desired atrioventricular delay.
8. The method of claim 1 , further comprising determining the pacing time interval by accounting for a relation between mechanical contraction and electrical excitation of the ventricle.
9. The method of claim 1 , wherein the pacing time interval is between about 0 ms and about 50 ms.
10. The method of claim 1 , wherein the atrium contracts at least partially against a closed atrioventricular valve between the atrium and the ventricle.
11. The method of claim 10 , further comprising reducing atrial kick by closure of the closed atrioventricular valve, thereby causing the reduced ventricular filling.
12. The method of claim 1 , wherein 100% of the future anticipated contraction of the atrium occurs during ventricular systole of the ventricle.
13. The method of claim 1 , further comprising setting the pacing time interval between about 0 ms and about 50 ms when an intrinsic atrial excitation rate of the atrium is lower than an intrinsic ventricular excitation rate of the ventricle.
14. The method of claim 1 , further comprising:
sensing at least one cardiac activity parameter comprising at least one of blood pressure, blood flow, atrioventricular valve status, or wall motion of the heart or a part thereof; and
adjusting the pacing time interval based on the sensed at least one cardiac activity parameter.
15. A method for reducing blood pressure of a patient, the method comprising:
delivering stimulation pulses to an atrium and a ventricle of a heart of the patient at a first delivery rate expected to be higher than a natural heart rate of the heart;
sensing whether a natural excitation occurs between delivery of the stimulation pulses;
when the natural excitation occurs, inhibiting delivery of next stimulation pulses to the atrium and the ventricle;
when an amount of sensed natural excitations exceeds a predetermined higher threshold over a given time frame, identifying the natural heart rate as higher than the first delivery rate, and increasing the first delivery rate to a second delivery rate that is higher than the natural heart rate; and
when an amount of sensed natural excitations is lower than a predetermined lower threshold over a given time frame, decreasing the first delivery rate to a third delivery rate to avoid over-excitation of the heart.
16. The method of claim 15 , further comprising sensing the natural heart rate.
17. The method of claim 16 , wherein the first delivery rate is higher than the sensed natural heart rate of the heart, and
wherein delivering the stimulation pulses to the atrium and the ventricle comprises stimulating the ventricle at a time between about 50 ms before and about 70 ms after stimulation of the atrium.
18. The method of claim 15 , wherein delivering the stimulation pulses causes ventricular excitation before a stimulation pulse is delivered to the atrium, and
wherein the stimulation pulse delivered to the atrium is delivered at a time that is earlier than a next anticipated natural onset of atrial excitation.
19. The method of claim 15 , further comprising reducing blood pressure of the patient to below a pretreatment blood pressure by at least one of reduced ventricular filling or increased atrial stretch.
20. A system for treating a blood pressure disorder in a patient, the patient having a pretreatment blood pressure, the system comprising:
a stimulation circuit configured to deliver a stimulation pulse to at least one cardiac chamber of a heart of the patient; and
at least one controller configured to execute delivery to a ventricle of the heart one or more stimulation pulses a pacing time interval before a future anticipated contraction of an atrium associated with the ventricle,
such that the ventricle begins contracting before the future anticipated contraction of the atrium begins,
thereby reducing blood pressure of the patient to below the pretreatment blood pressure by at least one of reduced ventricular filling or increased atrial stretch.
21. The system of claim 20 , wherein the at least one controller is further configured to deliver to the atrium one or more stimulation pulses after the pacing time interval to cause the future anticipated contraction of the atrium.
22. The system of claim 20 , further comprising:
a first sensor that senses an excitation rate of at least one of the atrium or the ventricle; and
a second sensor that senses a parameter relating to cardiac activity,
wherein the least one controller adjusts the pacing time interval based on the sensed parameter.
23. The system of claim 22 , wherein the parameter comprises at least one of blood pressure, blood flow, atrioventricular valve status, or wall motion of the heart or a part thereof.
24. The system of claim 22 , wherein the second sensor comprises at least one of a pressure sensor, an impedance sensor, an ultrasound sensor, an audio sensor, or a blood flow sensor.