JP4131735B2 - Method and apparatus for determining pressure associated with the left atrium - Google Patents

Description

  The present invention relates primarily to quantitative measurement of pressure in the body, and more particularly to obtaining a quantitative pressure value for determining mean left atrial pressure and mean left atrial transmural pressure, and other pressures associated with the left atrium. .

  There is a long-felt need for a non-invasive method that can be managed by a non-doctor to accurately determine mean left atrial pressure and transmural pressure.

  Adjacent to the left atrium in prior US Pat. Nos. 5,048,532, 5,181,517, 5,263,485, and 5,398,692 to the applicants Donald D. Hickey Thus, an apparatus and method for measuring pressure, such as the mean left atrial pressure associated with the left atrium, from the effect on an inflated balloon inserted into the esophagus is disclosed. More specifically, the above patent is incorporated herein by reference, but to determine the average left atrial pressure and / or other pressures associated therewith, the balloon is adjacent to the left atrium and the left atrial pressure Measuring the balloon pressure when the amplitude of the balloon pressure oscillation affected by the

  The object of the present invention is to obtain non-invasive quantitative pressure measurements for easily measuring human average left atrial pressure, transmural pressure and other pressures safely, accurately and reliably, and This is what can be obtained by someone who is not a doctor. As used herein and in the claims, the terms “transmural pressure” and “pulmonary vein transmural pressure” are meant to refer to the mean left atrial transmural pressure.

  In order to safely and accurately and reliably measure human average left atrial pressure and transmural pressure non-invasively and easily, according to the present invention, a balloon is inserted into the human esophagus and adjacent to the left atrium. When the heart sound intensity peaks after being positioned and inflated and the heart sound is transmitted to the balloon, the average balloon pressure is measured as described in more detail below.

  The left atrium is generally adjacent to the esophagus over a distance of about 2 cm to 5 cm. To obtain a good connection between the balloon and the left atrial pressure, position the balloon within the esophagus that extends adjacent to the left atrium so that the prevailing pressure acting on the balloon indicates the left atrial pressure Is considered important.

  In connection with pacing, an article titled “Optimal Mode of Transesophageal Atrial Pacing” by M. Nishimura et al. In American J. of Cardiology, vol. 57, 1986, p. 791-796. States that “the point showing the largest monopolar atrial electrogram was therefore considered the optimal site of pacing for both bipolar and monopolar stimulation”. This article also states that bipolar atrial electrograms should not be used to determine optimal pacing sites. “Transesophageal Atrial Pacing Threshold” by D. Benson et al., “The role of electrode spacing, pulse width and catheter insertion depth” described in American J. of Cardiology, vol. 53, 1984, p. 63-67. See also Role of Interelectrode Spacing, Pulse Width and Catheter Insertion Depth. Another related article is “Electrocardiographic Verification of Esophageal Temperature Probe Position” by G. Brengelmann et al. In J, Applied Physiology, vol. 47, 1979, p. 638-642. "Simple esophageal electrocardiography using bipolar recording leads" by S. Hammill et al. Described in Annals of Internal Medicine, vol. 95, 1981, p. 14-18. Is mentioned.

  The method proposed by Nishimura et al. May produce good results for pacing. However, in some patients, the electrogram becomes biphasic, preventing the position of the left atrium from being determined only by determining the point that exhibits the largest monopolar electrogram. The position of the maximum absolute P wave amplitude is not necessarily the position of the left atrium because of pressure coupling. In addition, the parameters for positioning for pacing are different from the parameters for coupling atrial pressure to the esophageal balloon, and the focus is on determining the location of the electrical site. Thus, a good position for pressure coupling may not be considered a good position for pacing. Thus, a more accurate and more reliable method of determining atrial position for pressure coupling would be desirable.

  Accordingly, it is an object of the present invention to provide a more accurate and more reliable approach for determining atrial position with esophageal electrodes so that pressure values associated with the left atrium can be more easily and accurately obtained. It is.

  In order to provide such an accurate and reliable approach, according to the present invention, a series of incremental electrograms are obtained when the bipolar electrode moves along the length of the esophagus. The negative portion of each P wave maximum absolute value segment is determined for at least one P wave of each of the incremental electrograms. The esophageal depth for positioning the inflated balloon is selected so that the electrogram for it corresponds to the depth of the incremental electrogram that indicates the length of the largest negative portion.

  The above and other objects, features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments when read in conjunction with the accompanying drawings. In the drawings, the same or similar parts are denoted by the same reference numerals.

  Referring to FIG. 1, a catheter device including a hollow catheter 20 generally designated 19 is illustrated, which catheter is a length of flexible tubing having a lumen or lumen 23 (see FIG. 13). 22, a balloon 24 communicating with the lumen 23 is attached to one end thereof, and the balloon is pressurized and pressure detected by the lumen. In order to obtain an electrocardiogram via the esophagus, the electrode assembly 21 is positioned directly above the balloon 24 and a pair of electrical leads 25, 29 are provided in the second catheter 27, as will be described in more detail below.

  Balloon 24 is positioned in the esophagus 26 of the human body to sense the pressure in the left atrium 28 of the heart 30. When the catheter 20 is inserted, the balloon first passes through the nostril 32, the pharynx 34, and then enters the esophagus 26. If desired, the balloon may instead be inserted through the mouth. As shown in FIG. 1, the outer wall of the left atrium 28 is adjacent to and substantially in direct contact with the outer wall of the esophagus 26, and in this connection, is inserted non-invasively into the esophagus 26 and into the esophagus 26. There is the advantage of determining the average left atrial pressure and the average left atrial transmural pressure, and the associated pressure, by the positioned balloon 24 so as to be adjacent to the left atrium along, thereby sufficiently sensing the left atrial pressure . A more detailed description of the catheter 20 is provided in the aforementioned patent, which is hereby incorporated by reference, including its inflation and its pressure measurement.

  As disclosed in the aforementioned patent, using the oscillometric principle, the esophageal balloon 24 is left when the amplitude of the balloon pressure oscillation affected by the left atrial pressure is at the peak, as discussed below. By measuring the average pressure in the esophageal balloon 24 as it is gradually inflated while adjacent to the atrium 28, the average left atrial pressure and its associated pressure are determined. According to the present invention, or using oscillometric principles, the average in the inflated balloon 24 when the intensity of the sound wave is at its peak after the sound wave is transmitted through the balloon, as will also be discussed below. By measuring the pressure, the average left atrial pressure and its associated pressure are determined.

  Although the invention is not limited by the description of this or other portions of the specification, the following will occur when the balloon 24 is pressurized. When the detection balloon 24 is gradually filled, the pressure in it increases at a slow and steady rate, which, according to the previously studied theory of oscillometric effects, is the atrial pressure and respiratory waves that generate vibrations therein. And is affected by. As the average balloon pressure approaches the average left atrial pressure, the atrial pressure oscillation component of the balloon pressure increases in intensity or amplitude until the balloon pressure resonates to the maximum, ie, reaches peak oscillation, at which time the average balloon pressure Approximates the mean left atrial pressure. Thereafter, as the average balloon pressure continues to increase, the amplitude of oscillation due to atrial pressure decreases. More specifically, balloon pressure oscillates maximally when balloon inflation raises the pressure of the tissue surrounding the left atrium to a point where the average tissue pressure is equal to the average left atrial pressure (MLAP). In this way, when the balloon is unfilled, i.e., when the average pressure on both sides of the balloon wall is equal, it works best as a pressure transmitter, and as a result, when the average balloon pressure is equal to the average left atrial pressure. It can be said that the maximum amplitude of the balloon pressure oscillation is obtained.

  2-5 show an absolute balloon pressure waveform 108 (FIG. 2), an average balloon pressure waveform 110 (FIG. 3), a differential signal 112 (FIG. 4) with additional gain from the signal processor, and a simultaneous electrocardiogram 114. FIG. 5 illustrates four electronic displays or tracings used to record and display (FIG. 5). Each vertical line 116 in FIGS. 2-5 represents the same point in time. Comparing the respective electrocardiograms 140 and 114 of FIG. 11 and FIG. 5, it is shown that the time scale of FIG. 11 expands greatly with respect to the time scale of FIGS.

  By noting the peak resonant amplitude of waveform 112 (FIG. 4) and comparing it to the simultaneous average balloon pressure 110 (FIG. 3), the average left atrial pressure can be determined. In this way, according to the oscillometric principle, when the waveform 112 oscillation is at a peak, i.e. when the waveform 112 peak or maximum amplitude oscillation occurs at time 116 when the balloon pressure is equal to the average left atrial pressure. Balloon pressure approximates the average left atrial pressure. The mean left atrial pressure is thus determined from the examples of FIGS. 2-5 and is determined to be about 3 cmH 2 O, exemplified by reference numeral 128. It should be understood that the pressure 128 approximates the mean left atrial pressure. In order to obtain a more precise determination of the average left atrial pressure, the pressure 128 must be adjusted as discussed in the aforementioned patents incorporated herein by reference.

  Although not limiting the invention by the description of this or other portions of the specification, the balloons not only best transmit the pressure acting on them, but also best transmit sound when unfilled. That is, it appears that the maximum sound energy can penetrate the balloon wall when not under tension (when the pressure is balanced on both sides). In this way, the amplitude of the heart sound or any other sound transmitted through the balloon and tube is such that, if the balloon is unfilled, the average balloon pressure is equal to the average left atrial pressure (if any, the influence of the heart weight). It seems that it becomes the maximum when it is equal to. Therefore, referring to FIGS. 6 and 7, according to the present invention, the amplitude (intensity) of the heart sound or other sound wave (sound pressure level), exemplified by the reference numeral 400 transmitted by the balloon 24 and the tube 22, is the average left atrial pressure. Balloon pressure can be measured when peaked as an indication (after adjusting for the effects of heart weight, if any). In this way, a condenser-type or other suitable microphone, illustrated by reference numeral 402, is properly positioned in the appropriate housing 404 at the entrance illustrated by reference numeral 414 to the tube 22, picking up the heart sound 400, Is then filtered with a high-pass filter, illustrated at 406 in FIG. 7, to remove irrelevant frequencies, perhaps less than about 30 Hertz. Alternatively, a band filter may be used. In this manner, the microphone 402 establishes pressure transmission or flow communication between the balloon 24 and the tube 22 to receive the heart sound 400 that generally passes along the tube path without interference, and the heart sound 400 is transmitted through the wall of the balloon 24. Through to the microphone 402. Microphone 402 is, for example, an Archer electret PC (Radio Shack) sold under catalog number 270-090, a division of Tandy Corp. of Fort Worth, Texas. Archer Electret PC) Wearable condenser microphone element.

  Condenser microphone 402 conventionally comprises foil diaphragms 408, 410 spaced apart by a pair (air space 412). Diaphragm 408 extends across the opening to sound isolation housing 416 and closes it to receive sound wave 400 from tube 22 through inlet 414. The spaced diaphragms 408, 410 act as capacitors, and the vibration of diaphragm 408 relative to diaphragm 410 results in a varying capacitance. Diaphragm 410 is positioned in housing 416 so that it is separated from the sound so as not to vibrate under the influence of sound wave 400 as diaphragm 408.

  In general use of a condenser microphone, the pressure applied to a pair of diaphragms needs to be equal. Normally, pressure changes encountered, such as atmospheric pressure changes or other pressure changes, are relatively small and low, so only a very small hole need be provided in the casing 402 and diaphragm 410. Since these pressure balancing holes are therefore small enough, the intensity of the sound entering the casing is very low, thus allowing a slow pressure balance in response to a slow change in pressure, etc. without causing a significant bias effect.

  The pressure change in the tube 22 due to balloon inflation is on the order of 5 or 6 cmH2O (5000-6000 dynes / cm2), which is generally the pressure change encountered by the microphone (perhaps 2 dynes / in the sound of a track racing motor). These pressure changes due to balloon inflation occur very rapidly, representing a 1000 to 10,000 fold increase over cm @ 2, or less than 0.2 dynes / cm @ 2 in heart sounds. These pressure changes due to balloon inflation can break the condenser if not properly balanced at the same time. In order to achieve the desired pressure balance for the abrupt and large pressure changes encountered in tube 22, a pressure balance hole, illustrated by reference numeral 418, is probably drilled with a diameter of about 0.020 inches, eg, .0. Since a pressure balancing hole, exemplified by reference numeral 420 of a suitable size such as 0225 inches, is drilled in diaphragm 410, the pressure in air space 412 is also equalized.

  Hole 418 and hole 420 are of an appropriate size for pressure balancing, but hole 418 may be large enough that it does not sufficiently block the passage of sound wave 400 that may result in undesirable bias effects. . In order to substantially reduce the intensity of the sound wave 400 through the pressure balancing hole 418, a low pass filter comprising a length of microhole tube 421 having an inner diameter of about 0.15 inches is suitably connected to the hole 418. The The length of tube 421 required to provide adequate pressure balance to the microphone and prevent sound from passing has been empirically found to be about 6 inches. The tube 421 is preferably made of a rigid material such as polypropylene or fine glass tube that does not allow sound to pass well.

  Balloon and heart pressure waveforms generally have a frequency in the range of 3-9 Hz. In contrast, the frequency of the sound wave 400 may be in the range of 30-300 Hz. The microphone 402 is tuned by the length of the tube 421 to allow low frequency pressure changes to balance across the body of the microphone 402 while preventing or substantially delaying higher audio frequencies to balance. To do. Low frequency air pressure changes can therefore be accurately transmitted through the length of the tube 421, while the high frequency heart sound 400 is attenuated resulting in an amplitude loss and possibly one of the original amplitude. / 5. Such weakened waves passing through the diaphragm 410 do not significantly affect the microphone output. For example, 10 amplitudes acting on diaphragm 408 can result in 8 in output amplitude, which is considered appropriate to obtain the desired relative sound intensity level for a given baseline, Therefore, a smooth curve with a prominent peak can be seen.

  The microphone output can be appropriately amplified and may be used and recorded to determine transmural pressure or other pressure associated with the left atrium. However, to obtain a sound display that can be used more easily, referring to FIG. 7, the microphone output passes through the appropriate noise or sound intensity meter 422, in which the decibel equivalent value of the sound output is output. The This decibel equivalent value is then filtered by filter 406, which removes respiratory frequencies, etc. less than about 30 Hz. The filtered signal then passes through a suitable exponential amplifier 424 where it is exponentially amplified to obtain a more prominent peak. The filtered and amplified signal can then be recorded by a suitable recorder 426.

  FIG. 8 shows a tracing 428 similar to that of FIG. 2 of absolute balloon pressure from the esophageal balloon 24 as filled using a Cobe CDX III transducer. The tracings of FIGS. 8, 9, and 10 occur for the same period of time, as indicated by the time line 430. Each vertical line 432 in FIGS. 8, 9, and 10 represents the same point in time. Tracing 434 in FIG. 9 is the output from the previously described electret microphone 402 processed through a 10-40 Hz bandpass filter. Tracing 436 in FIG. 10 is a steady baseline oscillometry signal from balloon 24, which is obtained in a similar manner to signal 112 shown in FIG. FIG. 10 shows that the peak resonance amplitude of the balloon pressure signal occurs at time 432. FIG. 9 shows that the intensity (amplitude) of the sound wave 400 reaches a peak at approximately time 432. In this way, the tracing 436 can be used to verify that the mean left atrial pressure or other related pressure can be determined using the sonic tracing 434 transmitted through the balloon 24. give. In this way, tracings 434, 436 each illustrate an average left atrial pressure at point 438, assuming that there is no cardiac weight effect.

  Referring to FIG. 13, from any point indicated by reference numeral 502 after passing the nose or mouth without inaccuracies, for example, when the catheter is pushed into the esophagus, it is triggered by bending of the electrode wire. To obtain a measurement of the distance or esophageal depth indicated by reference numeral 500 toward the esophageal position indicated by reference numeral 504 corresponding to the left atrium 28, the electrode assembly 21 and the electrical leads 25, 29 are silastic. Or it is suitably enclosed in the tube 27 comprised from another synthetic resin material. Tube 27 is suitably attached to balloon catheter tube 20 to move together. However, if desired, the esophageal depth 500 may be determined by using an electrode catheter that is separate from the balloon catheter 20, after which the electrode catheter 27 is withdrawn and the balloon catheter has been previously determined. 500 is inserted.

  In accordance with the present invention, the esophageal electrode assembly 21 is selected as a bipolar to make an accurate and reliable determination of the esophageal depth 500 to facilitate positioning of the balloon 24, and thus the esophageal electrode assembly 21 is spaced apart. Two electrodes 506, 508, which provide signals along leads 25, 29, respectively. The trajectory of the composite electrogram signal is the point indicated by reference numeral 510, which is considered to be at the midpoint between the electrodes 506, 508 when the electrodes 506, 508 are equal in size. When the sizes of the electrodes are not equal, the trajectory is determined using principles known to those skilled in the art to which the present invention belongs. This trajectory 510 is at a distance indicated by reference numeral 512, perhaps about 2 inches above the balloon 24. Thus, once the esophageal depth 500 for the left atrium 28 is determined, the balloon 24 is still below this depth and only has to be raised to this depth 500.

  Since the electrogram indicated by reference numeral 140 is probably obtained in increments of each centimeter when the catheter 27 is pulled up to the esophagus, the esophageal depth 500 may desirably be measured to the nearest centimeter position. And the distance of each electrogram is indicated at 514. However, if desired, the electrogram may be recorded by the distance to the center of the first electrode 506, to which a distance equal to 1/2 of the distance between the centers of the electrodes is added.

  The signal from the bipolar electrode 21 is directed to a preamplifier, indicated by reference numeral 516, which combines the signals from the individual electrodes 506, 508 to eliminate baseline wander usually associated with esophageal electrograms and reduce low It is provided to remove frequency breathing and other artifacts and to strengthen the P wave while reducing the QRS wave. A suitable preamplifier is the Arzco preamplifier sold by Arzco Medical Electronics, Inc. of Chicago, Ill., Which is employed in the present invention. (Arzco Tapsul) may be used with pill bipolar electrodes. Preamplifier 516 connects the combined signal from electrode 21 to standard electrocardiograph 518, which outputs an esophageal electrogram 140, which includes a left leg rim lead 520 and a right leg rim lead, respectively. Line 522 may be connected.

  The preamplifier 516 also connects a right hand rim lead 524 and the signal on this lead 524 is relayed to the electrocardiograph 518 to provide a conventional rim lead II electrogram. This electrogram appears to have the advantage of establishing a P wave in the esophageal electrogram 140. Additional electrograms may be provided as is known to those skilled in the art to which the present invention belongs.

  In FIG. 11, a P wave is shown at 530, which represents the atrial depolarization and is therefore associated with the atrial position on the stationary baseline 532. Usually, the portion of the electrogram wave below the baseline 532 is negative and the portion above the baseline 532 is positive. By examining the P-wave 530, the segment 534 having the greatest absolute deflection or amplitude can be located. The segment 534 includes a positive portion 536 above the base line 532 and a negative portion 538 below the base line 532. Note that the negative portion 538 precedes the positive portion 536 in the P-wave 530. However, in the P wave 540 of FIG. 12, the positive portion 542 of the maximum amplitude segment 544 preceded the negative portion 546.

  Based on a comparison of the X-ray indicating the position of the left atrium and the human esophageal electrogram, according to the present invention, the known left atrial position indicated by the X-ray and the length of the negative portion where the electrogram is maximum. It can be seen that there is a good correlation with the left atrial position determined by selecting the depth of the esophagus corresponding to the electrode depth of the incremental electrode. The negative part mentioned above is the negative part of each P-wave segment having the maximum absolute value.

  When using an implantable bipolar pacing electrode assembly in a Medtronic coronary sinus pacemaker having two electrodes with a distance between the centers of the electrodes of 3.3 cm, the electrode catheter is pulled up into the esophagus, Esophageal bipolar electrograms were taken in 1 cm increments. It should be understood that the distance between the electrodes may be different for different bipolar electrode assemblies.

  With each increment, an electrogram baseline 532 (from which positive and negative deflections are generated) is established so that accurate measurements can be obtained. Each P-wave segment selected with maximum absolute (total) deflection (including positive and negative parts) is recognized. The length of the negative portion or component of this P-wave segment is then measured. Preferably, a number such as 2 or 3 is given as such a negative portion length measurement and averaged to provide an electrogram measurement of each increment. For purposes of defining the claims, such an average of the negative portion measurements of the increment electrogram shall be deemed equivalent to the negative portion length determined for that increment electrogram. It is. After the measurement is obtained at each increment of distance, the depth of the electrode having the largest negative portion or component is selected. This depth is relative to the center of the upper electrode. Thus, an amount equal to 1/2 of the distance between the centers of the electrodes, or 3.3 / 2, or 1.65 cm, is added to the electrode depth, of the selected electrode depth relative to the center of the bipolar electrode. Provides a distance, which is considered the distance to the left atrium. This distance was then compared to the distance to the left atrium determined by X-ray for a particular person.

  The table below is the data results for 8 humans and shows the distance from the nose to the left atrium determined using the method of the present invention. The human was in the supine position and lateral X-rays were used.

  In numbers 5 and 6, there were two depths with the greatest negative portion length. As indicated, the depth in such a case is an intermediate point between the two depths.

  The method of the present invention determines the position of the left atrium within 1 cm in all the above cases, which is considered appropriate for balloon placement. Using the longest P-wave segment length to correlate only with the results of the seven cases above to determine the left atrial length is unlikely to be reliable in the method of the present invention. showed that.

  In addition to providing the esophageal electrogram 140, the output signal from the electrocardiograph 518 may be input to a suitable computer, denoted by reference numeral 141, which will be apparent to those skilled in the art to which the present invention pertains. Manipulating data entered according to the principles described herein in accordance with known principles and outputting processed esophageal depth 500, whereby electrocardiogram 140 is manually read and analyzed It is programmed to eliminate errors that may occur.

  A more clinically useful physiological value, i.e. transmural pressure determination, can be obtained without moving the balloon from its initial position near the left atrium. This value is particularly important because it can affect the degree to which fluid leaves the pulmonary capillaries and enters the lung tissue, causing pulmonary edema or “wet lungs”. In this way, this allows the physician to more accurately determine when the patient will become pulmonary edema from heart failure or volume overload, and it will allow assessment of the effects of positive and respiratory pressure by the aerated patient. It becomes possible. Clinicians are not accustomed to using this pressure because it has not been readily available.

  Transmural pressure is equal to left atrial pressure minus thoracic abdominal pressure, which is the peak balloon vibration measurement pressure-[pressure due to heart weight + thoracic abdominal pressure / thoracic abdominal pressure]-thoracic abdominal pressure equal. Thus, the transmural pressure is equal to the peak balloon vibration pressure-(pressure due to heart weight + intrathoracic pressure). As discussed above, the pressure at the slope change point 200 is equal to the pressure due to the heart weight plus the intrathoracic pressure. Thus, the transmural pressure is equal to the peak balloon oscillating pressure 128 minus the pressure at the slope change point 200, and both of these values come from the same balloon position, ie, the position adjacent to the left atrium. In addition, since it is not necessary to move the balloon away from the heart to measure esophageal pressure as an approximation of thoracic abdominal pressure, this is a concern regarding the effectiveness of esophageal pressure as a measure of thoracic abdominal pressure and thoracic abdominal pressure. Concerns about the optimal location within the esophagus to measure and concerns about any other factor in or around the esophagus that would distort the intrathoracic pressure determination.

  Although the invention has been described in detail above, it should be understood that the invention can be embodied in other ways without departing from the principles thereof. Such other embodiments are meant to fall within the scope of the invention as defined in the appended claims.

FIG. 5 is a left partial cross-sectional view of the human body taken along the central longitudinal section showing an esophageal catheter device including a balloon for determining pressure associated with the left atrium and an esophageal electrode assembly used in the present invention. When the balloon of FIG. 1 is adjacent to the left atrium, in a pressure trace of the unfiltered signal of the balloon pressure including vibrations due to breathing and heartbeat when the balloon is gradually pressurized in accordance with an embodiment of the present invention. is there. Figure 3 is a pressure trace of the average balloon pressure for the pressure trace of Figure 2; FIG. 4 is a pressure trace of an amplified cardiac signal obtained from the balloon pressure trace of FIG. 2 and on a steady baseline covering the same time period as FIGS. 5 is a graph of an electrocardiogram taken simultaneously with the pressure traces of FIGS. FIG. 2 is a schematic view of an apparatus including the balloon catheter of FIG. 1 according to another embodiment of the present invention. FIG. 7 is a block diagram of an electronic element for processing a signal provided by the apparatus of FIG. 3 is a pressure trace similar to that of FIG. 8 is a trace of the amplified sound output from the apparatus of FIGS. 6 and 7 covering the same period of time as FIG. FIG. 5 is a pressure trace similar to FIG. 4 where the signal is obtained from the balloon pressure trace of FIG. 8 and covers the same period of time as FIGS. FIG. 4 is an exemplary diagram of an electrogram P-wave. FIG. 4 is an exemplary diagram of an electrogram P-wave. FIG. 2 is a detailed partial view of the apparatus of FIG.

Explanation of symbols

19 Catheter device 20 Catheter 21 Electrode assembly 22 Flexible tube 23 Lumen 24 Balloon 25 Lead wire 26 Esophagus 27 Second catheter 28 Left atrium 29 Lead wire

Claims (10)

An apparatus for measuring an average pressure from a pressure source in the body, the balloon being positionable at a position in the body adjacent to the pressure source, means for inflating the balloon, and via the balloon and microphones for generating the received output sound waves transmitted Te, after waves transmitted through the balloon, to measure the pressure of the balloon when the intensity of the sound wave reaches a peak And a device comprising: The microphone is disposed in pressure communication with the balloon, and the microphone includes means for maintaining a balance of balloon pressure changes while preventing the sound intensity from becoming significantly balanced. The apparatus of claim 1. A pair of diaphragms in which the microphone acts as a capacitor; housing means for blocking one sound of the diaphragm; low-pass filter means provided in the housing means for maintaining balance of balloon pressure change; And a means for equalizing pressure on both sides of the diaphragm. The low-pass filter means includes a tube of a certain length that is connected to the housing and communicates between the inside and the outside of the housing, and the tube prevents the sound wave intensity from maintaining a remarkable equilibrium state. However, the apparatus of claim 3 selected to have a constant length and caliber to balance the balloon pressure change. The apparatus of claim 4, wherein the tube is constructed from a rigid material to prevent sound from penetrating through the wall of the tube. The means for measuring the balloon pressure comprises means for measuring an average balloon pressure when the intensity of the sound wave reaches a peak after a sound wave is transmitted through the balloon. The device described. The balloon may be inserted into the esophagus to position the balloon adjacent to the left atrium, and the measuring means may have a peak intensity of the heart sound after the heart sound is transmitted through the balloon. The apparatus of claim 1 comprising means for measuring balloon pressure when reached. The apparatus of claim 7, wherein the inflated diameter of the balloon is between about 0.8 and 1.5 cm. A balloon insertable into the esophagus to be positioned adjacent to the left atrium, means for inflating the balloon, and measuring the balloon pressure when the intensity of the heart sound transmitted through the balloon reaches a peak Means for
Means for adjusting the measured balloon pressure to compensate for the effects of heart weight. 8. The means for measuring the balloon pressure comprises means for measuring an average balloon pressure when the intensity of the sound wave reaches a peak after a sound wave is transmitted through the balloon. The measuring device described.

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