Claims
- 1. A method of automatically controlling the speed of an axial flow ventricular assist device, in accordance with a patient's time-varying physiological requirements, comprising the steps of:
- a) sensing the opening and closing of the aortic and mitral valves of the patient's heart; and
- b) maintaining said speed at a level where the aortic valve remains closed on most cycles of the patient's heartbeat to avoid ventricular collapse, and the mitral valve opens and closes on every cycle.
- 2. The method of claim 1, in which said sensing step includes:
- i) measuring the pulsatility of the motor current of said device; and
- ii) determining the speed at which said pulsatility decreases to a predetermined reference value.
- 3. The method of claim 1, in which said sensing step includes:
- i) continually determining the average peak-to-peak value of the motor current of said device over a period of several cycles;
- ii) incrementally increasing motor speed if said average peak-to-peak value is above a predetermined reference value; and
- iii) incrementally decreasing motor speed if said average peak-to-peak value is below said predetermined reference value.
- 4. The method of claim 1, in which said sensing step is performed acoustically by detecting heart sounds.
RELATED CASES
This case is a continuation-in-part of application Serial No. 08/740,749 filed Nov. 1, 1996, now U.S. Pat. No. 5,888,242.
US Referenced Citations (8)
Number |
Name |
Date |
Kind |
3985123 |
Herzlinger et al. |
Oct 1976 |
|
4809681 |
Kantrowitz et al. |
Mar 1989 |
|
5693091 |
Larson, Jr. et al. |
Dec 1997 |
|
5697884 |
Francischelli et al. |
Dec 1997 |
|
5722930 |
Larson, Jr. et al. |
Mar 1998 |
|
5807234 |
Bui et al. |
Sep 1998 |
|
5833619 |
Freed et al. |
Nov 1998 |
|
5888242 |
Antaki et al. |
Mar 1999 |
|
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
740749 |
Nov 1996 |
|