Intracardiac blood pump

Details Intracardiac blood pump Intracardiac blood pump

1998-11-24

2001-01-23

Coggins, Wynn Wood (Department: 3763)

Surgery

Cardiac augmentation

With condition responsive means

C623S003100, C415S900000, C604S065000

Reexamination Certificate

active

06176822

ABSTRACT:

The invention relates to an intracardiac blood pump, and in particular to a blood pump that may be inserted entirely into the heart to assist the natural cardiac pump function or to replace the same by a continuous pumping operation.
A pump device for supporting the heart is described in WO94/09835 (Jarvik). This pump device comprises two independent pumps each having a pump portion and a drive portion rigidly connected therewith. The pump portion of the one pump is introduced into the left ventricle through an operation opening at the apex of the heart such that it delivers blood from the left ventricle into the aorta. The other pump portion is introduced through another operation opening into the right ventricle such that it delivers blood from the right ventricle into the pulmonary artery. The system further comprises a control and display module that is small enough to be sterilized and used in the sterile environment of the operation. It may include a microprocessor with control and monitoring algorithms for regulating the volume flow and the pressure, or to supply the volume flow and the pressure to a data base, the values thereof having been measured by sensors or having been calculated by comparing the measurements of velocity and energy consumption. These pumps, referred to as cannula pumps, may be equipped with built-in pressure sensors or volume flow measuring devices to take local measurements of these parameters in the context of patient management.
It is an object of the present invention to provide an intracardiac blood pump, the operational behavior of which can be determined with simple measuring means that require little additional space.
According to the invention, the object is solved with the features of claim
1
.
In the blood pump of the present invention, the rotational speed of the motor is controlled in dependance on the pressure prevailing at the outlet side of the pump. The pressure at the delivery side of the pump is an important parameter for the output and the operating point of the pump; it may further be used to measure the volume flow, that is the yield per unit of time. The motor may be controlled such that its rotational speed is varied as a function of the measurement result of the pressure measuring means.
In the context of the present invention, the term “intracardiac” is meant to refer to the ventricles, the vestibules and the adjacent vascular stumps.
The pressure measuring means may further be used to determine the position of the pump in the heart.
Suitably, the pressure measuring means comprises two pressure sensors, one of which measures the pressure at the delivery side of the pump, while the other measures the pressure at the inlet side of the pump, the control unit controlling the rotational speed of the motor as a function of the signals from both pressure sensors. Using the pressure sensors, the differential pressure between the intake side and the delivery side of the pump is determined. From the differential pressure of the pump and the rotational speed of the motor, the volume flow may be calculated with the use of a hydraulic characteristic pumping diagram of the pump. Thus, the volume flow delivered by the pump is obtained from a very simple measurement, with the sensors requiring very little space.
Instead of two pressure sensors, a single differential pressure sensor may be provided that measures the differential pressure between the delivery side and the intake side of the pump. Such a differential pressure sensor does not provide an absolute pressure value, but rather yields a value of the differential pressure which is the essential value for determining the volume flow. On the other hand, such a differential pressure sensor may at the same time be used for locating the pump within the heart.
The pressure measuring means need not have one or more pressure sensors. Rather, the pressure may also be determined indirectly via a current measuring means that measures the motor current and calculates the differential pressure between the delivery side and the intake side of the pump from the motor current and the rotational speed.
The present invention further relates to an intracardiac blood pump offering the possibility to monitor the positioning of the pump in the heart without requiring any x-ray control for that purpose. A blood pump of this type is defined in claim
6
. A measuring means provides an information signal corresponding to the differential pressure between the delivery side and the intake side of the pump. On a display device, either the information signal or a signal derived therefrom or information on the correct positioning of the pump in the heart are displayed. Here, use is made of the fact that a differential pressure between two different locations of the pump can occur only, if between these two locations, there is an element enclosing the pump, e.g. a cardiac valve. As long as there is no differential pressure between these two locations, the pump as a whole is in the same space. A differential pressure will appear only when a part of the pump is in another space. Due to this fact, the position of he pump may be determined by simple means.
Preferably, the pump is designed as an intravascular pump as described in WO97/37696 (published posteriorly). Such an intravascular blood pump is connected to a catheter. It is small enough to be pushed through a blood vessel to the place where it is intended to work, or it may also be operated in the blood vessel. In an intravascular blood pump of this type, the pump portion and the drive portion have substantially the same diameter of no more than about 5-7 mm, since the vessel width in peripheral regions of the body is slightly larger than 7 mm at most. The rigid length of such a pump must not be greater than about 35 mm so that the pump can manage to pass through bends of blood vessels. However, the pump may further be prolonged by means of a flexible hose that increases the effective length of the pump.
On the other hand, it is possible to surgically introduce the pump into the heart via the vessel system near the heart. In any case, the pump is small enough to fit into the heart, including the vestibules and the adjacent vascular stumps, and to be operated in the heart without parts of the pump extending from the heart. If any, the catheter connected to the pump is lead out from the heart. This catheter not only includes the lines for supplying electric energy to the pump, but also the signal lines leading from the sensors of the pump to the extracorporeal control unit.


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Article: Control of Rotary Pulsatile Cardiac Assist Pump Driven by an Electric Motor; Publication date Oct. 29, 1992.
Article: Development of a Miniature Intraventricular Axial Flow Blood Pump, Publication date Jul./Sep. 1993 issue of ASAIO Journal.

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