Device and method for effecting ventricular cardiac pacing by inserting electrodes which are supported by a carrier into the stomach of a patient via the patient's esophagus, and pressing the electrodes against the wall of the stomach by the action of a carrier displacing member.

BACKGROUND OF THE INVENTION 
The present invention relates to non-invasive cardiac pacing, and is 
particularly directed to a method and device for transmitting electrical 
stimulation pulses to a heart ventricle, and monitoring cardiac function, 
by insertion of electrodes via the patient's esophagus, thereby avoiding 
the need for any surgical intervention. 
It is already known in the art that atrial cardiac pacing can be performed 
by a procedure known as transesophageal pacing, in which one or more 
electrodes are introduced into a patient's esophagus to bring the 
electrodes to a point in the esophagus which is directly adjacent to the 
left atrium of the heart. A device of this type is disclosed in U.S. Pat. 
No. 4,706,688. 
When electrodes are brought to such a position and are pressed against the 
wall of the esophagus, cardiac stimulation pulses can be applied to the 
heart atrium. When a condition requiring atrial pacing is encountered, 
this technique can prove advantageous since it allows pacing to be 
initiated rather quickly without requiring surgical intervention and the 
trauma associated therewith. 
However, while there are certain situations in which ventricular pacing is 
indicated, there are no existing devices or procedures which allow 
ventricular pacing to be achieved safely in a manner similar to the 
transesophageal pacing technique described above. 
BRIEF SUMMARY OF THE INVENTION 
It is a primary object of the present invention to make possible 
ventricular pacing by means of a device which can be inserted through a 
patient's esophagus in order to bring an electrode or electrodes into 
position to effect ventricular pacing. 
Another object of the invention is to provide a device for this purpose 
which is constructed to be safely and comfortably introduced into the 
patient's esophagus via a naris. 
A further object of the invention is to enable effective ventricular pacing 
to be achieved by the application of low current pulses. 
The invention is based in part on the realization that electrodes can be 
suitably mounted to enable them to first safely pass through the esophagus 
into the stomach and to then be pressed against the stomach wall at a 
location proximate to the patient's ventricle. 
Thus, the above and other objects are achieved, according to the present 
invention, by a device for effecting ventricular cardiac pacing, 
comprising: cardiac pacing electrodes; a carrier supporting the electrodes 
in a manner to permit the electrodes to be inserted into the stomach of a 
patient via the patient's esophagus; and carrier displacing means 
supporting the electrodes and operable for pressing the electrodes against 
the wall of the stomach at a location adjacent a heart ventricle. 
Objects according to the invention are further achieved by a method for 
effecting ventricular cardiac pacing comprising: inserting electrodes into 
a patient's stomach via the patient's esophagus; pressing the electrodes 
against a portion of the wall of the stomach which is adjacent a heart 
ventricle; and delivering electrical impulses to the electrodes for 
transfer to the heart ventricle as pacing pulses.

DETAILED DESCRIPTION OF THE INVENTION 
The device shown in FIG. 1 is composed basically of a tube, or catheter, 2 
having a flexibility sufficient to enable it to be advanced through a 
patient's naris (not shown) and then through the patient's esophagus 12 so 
as to bring the leading, or distal, end of tube 2 into the patient's 
stomach 14. Balloon 6 is mounted on the distal end portion of tube 2. 
Balloon 6 may be inflated via an airway 8 that extends to the proximal end 
of tube 2, which would be located outside of the patient's body. The 
proximal end of airway 8 may be provided with an inflation bulb or other 
inflation device of the type commonly employed in medical equipment. In 
FIG. 1, balloon 6 is shown in its fully inflated state. 
Tube 2 is provided, on its outer surface, with several annular electrodes 
16, each connected to one respective conductor 20 that passes though tube 
2 and extends to the proximal end of tube 2. The number, form and spacing 
of electrodes 16 will be selected on the basis of principles already known 
in the art. 
The patient's heart 24 is normally located relative to esophagus 2 and 
stomach 14 in substantially the manner shown in FIG. 1, with its left 
ventricle in close proximity to, or in contact with, the wall of stomach 
14, its right ventricle in proximity to the wall of stomach 14 and its 
left atrium close proximity to, or in contact with, esophagus 12. 
According to the invention, two or more electrodes 16 are pressed, as a 
result of inflation of balloon 6, against the inner surface of the portion 
of the wall of stomach 14 which is in proximity to, or in contact with, at 
least the left ventricle of heart 24, and possibly also against the inner 
surface of the portion of the wall of stomach 14 which is in proximity 
with the right ventricle of heart 24. Balloon 6 may be given a compliance 
and may be dimensioned so that balloon 6 will, upon being inflated, act to 
slightly distend the associated the portion of the wall of stomach 14 to 
an extend sufficient to place that stomach wall portion in contact with 
the outer surfaces of one or both ventricle chambers. Then, electrical 
impulses conducted to electrodes 16 via conductors 20 will be conducted to 
heart 24 through the stomach wall to act as ventricular pacing pulses. 
Due to the fact that balloon 6 can press electrodes 16 firmly against the 
stomach wall, and can press the stomach wall against at least one 
ventricle, electrodes 16 can be given small dimensions and low level 
pacing currents can be used. 
Tube 2 of a device according to the present invention could be constructed 
on the basis of principles well known in the art and can be constituted by 
any tubular body having the requisite flexibility. This tube could be 
constituted, for example, by a device known as a tapscope, examples of 
which are marketed by the Arzco Corporation. Tube 2 could also be 
identical to a known tube used for transesophageal pacing, as disclosed in 
the above-cited U.S. Pat. No. 4,706,688. Tube 2 may also be a flexible 
catheter made of electrically insulating material. 
Balloon 6 can be secured to a distal end portion of tube 2 in any suitable 
manner already known in the art for securing balloons to catheters and 
other medical devices. When balloon 6 is not inflated, it will not offer 
any impediment to insertion of the device through a naris and then through 
the esophagus. In addition, When balloon 6 is not inflated, tube 2 will 
assume its normal generally straight configuration, thus allowing it to 
pass easily and safely through the esophagus, while having sufficient 
flexibility to follow curves or bends in the esophagus. When tube 2 has 
been inserted to a final position, where a portion of its distal end 
projects by an appropriate amount into stomach 24, balloon 6 can be 
inflated, using an inflation fluid such as air or water introduced via 
airway 8, to deflect the distal end portion of tube 6 into the 
configuration shown in FIG. 1, so that at least two electrodes 16 press 
against the inner wall of stomach 14. 
Then, a pulling force may be applied to the distal end of tube 2 to help 
press the electrodes against the stomach wall. Prior to insertion of tube 
2, the patient's nasal passages will be locally anesthetized. Experience 
with other medical procedures involving nasal insertion of a tube have 
shown that the requisite pulling force will not cause unacceptable patient 
discomfort. Thereafter, pacing pulse may be applied between a selected 
pair of electrodes, or heart activity may be monitored by connecting one 
or more electrode pairs, via associated conductors 20, to monitoring 
equipment located outside of the patient's body. 
Balloon 6 may be made of any suitable, resiliently stretchable material of 
the type normally employed in medical devices, one suitable material being 
rubber latex. Balloon 6 can have homogeneous physical characteristics, 
including a homogeneous compliance, or balloon 6 can be made so as to have 
two subportions with respectively different compliances, compliance 
representing the ease with which a material can be stretched, and high 
compliance signifying greater ease of stretchability than does low 
compliance. This can be achieved by manufacturing the two subportions to 
have respectively different thicknesses or by fabricating the balloon in a 
manner such that the two subportions have respectively different 
compositions. In either event, balloon 6 can have a one-piece 
construction. 
The change in characteristics between subportions can take place at an 
appropriate transition region whose location is represented generally by 
the line 6a in FIG. 1. In this case, the subportion to the right of line 
6a would have a higher compliance than the subportion to the left thereof 
so that the subportion carrying tube 2 expands preferentially to press 
electrodes 16 against the inner surface of the wall of stomach 14. 
The electrodes on tube 2 may be constructed and mounted in the same manner 
as the electrodes disclosed in the above-cited U.S. Pat. No. 4,706,688. 
Tube 2 can have a relatively small diameter, for example as small as 7 
French, and can have a flexibility which enables it to be safely 
introduced to the patient's esophagus via a naris. This mode of 
introduction has been found to be less uncomfortable for the patient than 
oral introduction. 
In further accordance with the invention, electrodes 16 can, as shown in 
FIG. 1, be supplemented by identical electrodes 26 disposed along a length 
of tube 2 at a location to act on an atrial region of heart 24, in the 
manner disclosed in U.S. Pat. No. 4,706,688, cited above. Each electrode 
26 is also connected to a respective conductor 20 so that pacing pulses 
may be generated between an adjacent pair of electrodes or heart signals 
can be supplied to external monitoring equipment. Also as disclosed in 
U.S. Pat. No. 4,706,688, tube 2 carries a cuff, or balloon, 28 which is 
inflatable to press one or more pairs of electrodes 26 against esophagus 
12 at a location adjacent an atrial portion of heart 24. 
Electrodes 26 and cuff 28 have the same structure as disclosed in U.S. Pat. 
No. 4,706,688, as do all components, such as an airway member 30 for 
inflating cuff 28 and conductors 20 connected to electrodes 26. For this 
reason, the entirety of U.S. Pat. No. 4,706,688 is incorporated herein by 
reference. 
Ventricular and/or atrial pacing pulses can be generated by applying 
electrical voltage pulses between an adjacent pair of electrodes 16 or 26, 
this representing bipolar pacing, or between any one of electrodes 16, 26 
and an extended electrode secured to the patient's chest, this 
representing ambipolar pacing. Correspondingly, cardiac activity can be 
monitored by sensing electrical pulses created between an adjacent pair of 
electrodes or between any one electrode 16, 26 and the external electrode. 
A plurality of spaced electrodes 16 are provided to allow for individual 
variations in the precise position of heart 24 in the body. If the exact 
location of each electrode is not known, the same stimulating pulses can 
be applied to adjacent electrode pairs in the case of bipolar pacing, or 
adjacent electrodes in the case of ambipolar pacing. 
Thus, a device as disclosed herein can be selectively used to effect 
ventricular and/or atrial pacing and/or monitoring. 
According to a further feature of the present invention, the novel device 
disclosed above can be utilized in a system for performing 
electrophysiological testing, possibly on an outpatient basis. Such a 
system is employed, for example, to custom test a pacemaker which is to be 
implanted in a patient and to pretest the heart prior to pacemaker 
implantation. Heretofore, this has been done by surgically implanting 
between five and seven electrodes at different points in the heart 
chambers, applying pacing pulses having different characteristics, and 
monitoring the heart response with electrocardiographic (EKG) device. Such 
a procedure is known as preprogramming. 
Both the application of atrial and ventricular pacing pulses and monitoring 
of cardiac response can be performed in a system using a pacing device 
according to the invention, introduced into the patient's esophagus and 
stomach. Thus, one phase of surgical intervention can be eliminated. 
One embodiment of an electrophysiological pacing and monitoring system 
according to the invention is shown in FIG. 2. This system includes the 
device of FIG. 1, represented in FIG. 2 only by electrodes 16 and 26, a 
pulse generator and receiver 40, a control panel 50 and a monitor 60. 
Pulse generator and receiver 40 is connected to supply pacing pulses to a 
selected pair of electrodes 16 and a selected pair of electrodes 26 and to 
receive electrical signals arising in the heart and applied to the 
selected electrodes 16 and/or 26. The timing, frequency, pulse duration 
and magnitude of the electrical pulses delivered to electrodes 16 will 
also be determined on the basis of principles, and particularly biopolar 
pacing principles, already well-known in the ventricular pacing art. 
Control panel 50, which may be a keyboard, is connected to pulse generator 
and receiver 40 for inputting commands to control the timing, amplitude 
and duration of pacing pulses. 
Monitor 60 is connected to pulse generator and receiver 40 to display 
parameters of pacing pulses being outputted and associated heart 
responses. Monitor 60 may be a CRT, LED, LCD, plotter, printer, etc., and 
may display any desired combination of signal waveforms and alphanumeric 
data representations. 
Components 40, 50 and 60 may be constituted by known electrophysiological 
testing systems. With regard to pulse generator and receiver 40, systems 
for generating heart pacing pulses and for processing signals resulting 
from cardiac activities are already well known in the art and the assembly 
and operation of such systems for purposes contemplated by the present 
invention are well within the capability of those skilled in the relevant 
art or arts. 
As an example of operations that can be performed with apparatus according 
to the invention, atrial pacing pulses can be applied to electrodes 26 at 
a preset rate for a selected time period. These pacing pulses are then 
halted and the sinus node recovery time is measured. This measured time 
provides an indication of the function of the sinus node. 
According to another example, atrial pacing pulses can be applied to 
electrode 26, and the AV delay, which is an indication of the time 
required to conduct an atrial impulse to the ventricle, is measured. 
Atrial pacing can be used to overdrive and correct arrhythmias. The 
contribution of actual pacing to heart function can be assessed in 
comparison to the contribution of ventricular pacing alone. 
According to another possibility, ventricular pacing pluses are applied to 
electrodes 16 and the VA time, or the time required to conduct such pulses 
from the ventricle to the atrium, is measured. In addition, extra impulses 
can be used to reduce and correct, and to test the effects of medication 
on, arrhythmias. 
Such pacing pulses can also be employed to detect or correct arrhythmias. 
If arrhythmias are detected, these can either be converted by electrical 
shock, or paced out by increasing the rate of ventricular or atrial pacing 
pulses. 
In addition, the system according to the present invention can be utilized 
to perform other functions that are now performed by implanted pacemakers, 
including monitoring of drug therapy and monitoring of implanted pacemaker 
performance. Thus, with the device shown in FIG. 1 introduced into the 
patient's esophagus and stomach, pacing pulses having different patterns, 
including pulse rates, amplitudes, durations, etc., can be delivered to 
electrodes 16 and 26, respectively, accompanied by echocardiographic 
monitoring. This procedure will allow the physician to determine the 
optimum settings for a pacemaker, which can then be permanently implanted 
according to conventional techniques, and will facilitate preplanning of 
the type of pacemaker to be employed. 
A system of the type shown in FIG. 2 can thus be employed for testing 
atrial pacing, ventricular pacing, or atrial-ventricular pacing. It can be 
used to measure time intervals between a pacing pulse and a particular 
heart response, such as the AV delay or the VA delay. It can be employed 
to produce external stimuli which cause arrhythmias or to determine the 
efficacy of any drug treatment being performed on the patient. In 
addition, a system according to the invention can be employed to determine 
the programming parameters for a pacemaker prior to implantation. 
Because of the manner in which a device according to the invention is 
introduced into a patient, all of the procedures described herein can be 
performed on an outpatient basis. 
While particular embodiments of the present invention have been shown and 
described, it will be obvious to those skilled in the art that changes and 
modifications may be made without departing from this invention in its 
broader aspects and, therefore, the aim in the appended claims is to cover 
all such changes and modifications as fall within the true spirit and 
scope of this invention.