Pressure-driven intermittent pacing therapy
Cardioprotective pre-excitation pacing may be applied to stress or de-stress a particular myocardial region delivering of pacing pulses in a manner that causes a dyssynchronous contraction. Such dyssynchronous contractions are responsible for the desired cardioprotective effects of pre-excitation pacing but may also be hazardous. Described herein is a method and system that uses measures of a patient's physiological response to ventricular dyssynchrony to control the duty cycles of intermittent pre-excitation pacing.
1. A cardiac device, comprising:
pulse generators for incorporation into one or more pacing channels for delivering pacing pulses to one or more myocardial sites;
a controller programmed to operate the device in either a normal operating mode or an intermittent pacing therapy (IPT) mode;
wherein, in the IPT mode, the controller is programmed to deliver paces to the one or more myocardial sites using a pacing mode that results in some degree of ventricular dyssynchrony as compared with the normal operating mode;
a sensor for measuring blood pressure;
wherein the controller is programmed to:
establish timed duty cycles for delivering IPT;
measure a baseline value for the measured blood pressure during normal sinus rhythm when no IPT is being delivered;
switch to the IPT mode as scheduled by the timed duty cycle if the measured blood pressure is stable and within a specified range of the baseline value;
continue to monitor the measured blood pressure during delivery of IPT and, if the measured blood pressure stabilizes at an IPT-induced value lower than the baseline value, switch to the normal mode; and,
continue to monitor the measured blood pressure during the normal mode and, when the measured blood pressure returns to a value that is within a predetermined range of the baseline value, switch to IPT mode if the duty cycle has not expired.
2. The device of claim 1 wherein the controller is programmed to first determine whether a specified stability criterion for the measured blood pressure is met before terminating or initiating IPT.
3. The device of claim 1 further comprising an impedance sensor for measuring stroke volume, wherein the controller is further programmed to drive the IPT duty cycles based upon the measured stroke volume.
4. The device of claim 1 further comprising an impedance sensor for measuring stroke volume and a sensing amplifier for incorporating into a cardiac sensing channel for measuring heart rate in order to derive cardiac output, wherein the controller is further programmed to drive the IPT duty cycles based upon cardiac output.
5. The device of claim 1 wherein the controller is further programmed to switch from the IPT mode to the normal mode if the blood pressure rises to a predetermined value within a specified range of the baseline value during delivery of IPT as a result of a systemic reflex response.
6. The device of claim 3 wherein the controller is further programmed to switch from the IPT mode to the normal mode if the stroke volume rises to a predetermined value within a specified range of the baseline value during delivery of IPT as a result of a systemic reflex response.
7. The device of claim 4 wherein the controller is further programmed to switch from the IPT mode to the normal mode if the cardiac output rises to a predetermined value within a specified range of the baseline value during delivery of IPT as a result of a systemic reflex response.
8. The device of claim 1 wherein the controller is further programmed to discontinue delivery of IPT if the measured blood pressure is out of a, predetermined range considered safe during a, predetermined number of IPT duty cycles.
9. A method for operating a cardiac device, comprising:
delivering pacing pulses to one or more myocardial sites;
operating the device in either a normal operating mode or an intermittent pacing therapy (IPT) mode;
in the IPT mode, delivering paces to the one or more myocardial sites using a pacing mode that results in some degree of ventricular dyssynchrony as compared with the normal operating mode;
measuring blood pressure;
establishing timed duty cycles for delivering IPT;
measuring a baseline value for the measured blood pressure during normal sinus rhythm when no IPT is being delivered;
switching to the IPT mode as scheduled by the timed duty cycle if the measured blood pressure is stable and within a specified range of the baseline value;
continuing to monitor the measured blood pressure during delivery of IPT and, if the measured blood pressure stabilizes at an IPT-induced value lower than the baseline value, switching to the normal mode; and,
continuing to monitor the measured blood pressure during the normal mode and, when measured blood pressure returns to a value that is within a predetermined range of the baseline value, switching to IPT mode if the duty cycle has not expired.
10. The method of claim 9 further comprising first determining whether a specified stability criterion for the measured blood pressure is met before terminating or initiating IPT.
11. The method of claim 9 further comprising driving the IPT duty cycles based upon measured stroke volume.
12. The method of claim 9 further comprising driving the IPT duty cycles used upon measured cardiac output.
13. The method of claim 9 further comprising switching from the IPT mode to the normal mode if the blood pressure rises to a predetermined value within a specified range of the baseline value during delivery of IPT as a result of a systemic reflex response.
14. The method of claim 11 further comprising switching from the IPT mode to the normal mode if the stroke volume rises to a predetermined value within a specified range of the baseline value during delivery of IPT as a result of a systemic reflex response.
15. The method of claim 12 further comprising switching from the IPT mode to the normal mode if the cardiac output rises to a predetermined value within a specified range of the baseline value during delivery of IPT as a result of a systemic reflex response.
16. The method of claim 9 further comprising discontinuing delivery of IPT if the measured blood pressure is out of a predetermined range considered safe during a predetermined number of IPT duty cycles.