Detection of aortic porcine valve dysfunction by maximum entropy spectral analysis

A high-resolution method of spectral analysis, of the class generally called "maximum entropy method," was used in a study of aortic porcine valve closing sounds in 37 patients (ages 19 to 76). Spectra from 27 normal xenografts, implanted from 2 weeks to 61 months previously, were characterized by a dominant frequency peak, F1, at 89 +/- 15 Hz (mean +/- SD), with a lower amplitude peak, F2, at 154 +/- 25 Hz. Eight of nine patients with aortic porcine valve dysfunction were proved surgically to have leaflet degeneration or infection and had either F1 (139 +/- 54 Hz) and/or F2 (195 +/- 74 Hz) significantly higher than normal (p less than .001). In two patients with paravalvar leak but no leaflet abnormality, F1 and F2 were in the normal range. Estimation of F1 and F2 was highly reproducible and was unaffected by duration of implant up to 5 years. Spectral analysis of aortic porcine valve closing sounds by the maximum entropy method may be useful for detection of intrinsic xenograft dysfunction.     

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A sample of 30 subjects, 15 with and 15 without subjective temporomandibular joint (TMJ) complaints (noises, sounds), underwent a clinical examination, a sonography and an axiography, to detect TMJ clicking. The clinical examination found 22 noisy joints in a total of 60 TMJs considered. Axiography found 19 noisy joints and sonography 32. While 90% of the examined joints showed agreement between axiography and clinical examination (with a little higher sensitivity demonstrated by clinical examination with respect to axiography), 20% of the joints were positive for clicking in sonography only. Sonography showed a high sensitivity in detection of joint noises which suggests its utility as a screening test for early detection of craniomandibular disorders.     

The contribution of peridurography to the anatomy of the lumbosacral spinal canal

Phonocardiography and echocardiography were used to examine 20 patients with a normally functioning Beall disc mitral valve prosthesis. Phonocardiographic intervals were: Q-S1 interval 67 +/- 3 msec; A2-OC interval 118 +/- 8 msec. Maximal variation of the Q-S1 interval within one examination was 21 +/- 2 msec, for A2-OC interval it was 31 +/- 5 msec. Echocardiographic disc velocities were: opening velocity 296 +/- 30 mm/sec, closing velocity 414 +/- 44 mm/sec. Maximal variation of the opening velocity was 126 +/- 25 msec; maximal variation of the closing velocity was 334 +/- 57 msec. Abnormal poppet function was suspected in one patient with unusual prolongation and variability of A2-OC interval.     

Systemic hypertension as a risk factor for complications with an aortic mechanical valve

We sought to determine the effect of preoperative systemic hypertension on prosthesis related complications or postoperative aortic dissection after valve replacement in patients with aortic regurgitation. The patients were divided into two groups according to the presence or absence of systemic hypertension: Group I, with hypertension (n = 35), and Group II, without hypertension (n = 37). The survival rate and event free rate were examined for 72 patients who were alive 30 days after valve replacement with a St. Jude Medical valve for aortic regurgitation. The cumulative 10 year survival rate of Group I (65% +/- 12%) was lower than that of Group II (79% +/- 15%). The 10 year event free rate of all prosthesis related complications was 62% +/- 13% in Group I, and 96% +/- 3% in Group II (p < 0.05). The 10 year event free rate for ascending aortic dissection was 73% +/- 12% in Group I and 100% in Group II (p < 0.05). The linearized event rate of all prosthesis related complication was 3.8% per patient-year in Group I and 0.5% per patient-year in Group II. In conclusion, systemic hypertension was a risk factor for prosthesis related complications and for complicated aortic lesions after aortic valve replacement. Careful postoperative management for hypertension is necessary in patients with systemic hypertension after aortic valve replacement. Tissue valves may be recommended in patients with aortic valve disease and severe hypertension.     

The hypomobile temporomandibular joint

The hypomobile (restricted) temporomandibular joint (TMJ) is usually caused by a restricted joint capsule or by an anteriorly displaced disk. Here, painful unilateral hypomobility (19 mm jaw opening), with normal disk position, caused by voluntary immobilization after a dental procedure, was the presenting symptom. Management included inflammation control, TMJ manipulation (mobilization), and lateral pterygoid muscle relaxation. Inflammation and pain were alleviated by nonsteroidal anti-inflammatory drugs (NSAIDs) and local TMJ ice massage. TMJ mobilization was performed at every visit, to tear joint capsule adhesions and to realign collagen fibers. Exercise consisted mainly of resistive opening (the patient resists an upward force applied to the chin), with the jaw maintained at full opening. This produced lateral pterygoid muscle relaxation at full length, aiding in the restoration of a pain-free 44 mm opening.     

Determinants of reoperation after 960 valve replacements with Carpentier-Edwards prostheses

During the period of 1977 to 1990, 960 Carpentier-Edwards standard prostheses (Baxter Healthcare Corp., Santa Ana, Calif.) were placed in 875 operations. Freedom from reoperation at 10 years was 57% +/- 4%, 76% +/- 3%, and 95% +/- 5% for mitral, aortic, and tricuspid valve replacement, respectively. Age was the only independent determinant of reoperation for both aortic and mitral valves. Likelihood of reoperation decreased with age, with freedom from reoperation after 10 years in patients aged less than 60 years versus 60 or more years being 65% +/- 5% versus 90% +/- 4% after aortic valve replacement and 48% +/- 5% versus 75% +/- 6% after mitral valve replacement. For mitral valve replacement, larger valve size made reoperation more likely, with freedom from reoperation at 10 years being 71% +/- 6% for sizes median less than 31 mm and 57% +/- 5% for sizes 31 mm or larger. For aortic valve replacement, prior median sternotomy reduced freedom from reoperation at 10 years from 80% +/- 3% to 25% +/- 5%. The low prevalence of reoperation affirms the suitability of the Carpentier-Edwards prosthesis for selected elderly patients and for tricuspid valve replacement. Because of their influence on the probability of reoperation, valve size and prior cardiac procedures also merit consideration in the choice of valvular prosthesis.     

Repair of ruptured sinus of valsalva aneurysm: determinants of long-term survival

BACKGROUND: Ruptured sinus of Valsalva aneurysm is a rare cardiac anomaly and long-term survival after surgical treatment is not well established. This study was designed to investigate the determinants of long-term survival after repair of ruptured sinus of Valsalva aneurysm. METHODS: From April 1978 to April 1996, 53 patients underwent operation for ruptured sinus of Valsalva aneurysm. The incidence among our cardiac surgical population was 0.56%. Long-term survival was investigated in 46 patients (13 to 65 years) who survived the operation, with 96.2% follow-up completeness (mean+/-standard deviation, 6.5+/-4.9 years; maximum, 17.2 years), by univariate and multivariate analyses. RESULTS: There was no early operative death and no recurrence after the initial repair. Actuarial survival was 83.8%+/-8.4% at 15 years. Reoperation, aneurysm draining into the left ventricle, aortic prosthetic dehiscence, bacterial endocarditis, and aortic cross-clamp time (<70 minutes) were significant factors in long-term survival (p < 0.05). Multivariate analysis revealed that only aortic prosthesis dehiscence was the significant factor influencing late survival (p = 0.0001). CONCLUSIONS: Surgical treatment for ruptured sinus of Valsalva aneurysm is safe and has satisfactory results. Aortic prosthesis dehiscence is the independent determinant for long-term survival. Other factors including bacterial endocarditis, concomitant ventricular septal defect repair, and aortic valve replacement did not independently influence long-term survival.     

A study of the influence of arrangement of upper posterior artificial teeth on pronunciation: Japanese sounds articulated on the posterior palate

To clarify the standard of bucco-lingual tooth arrangement in complete denture construction, the influence of the bucco-lingual position of upper posterior artificial teeth on pronunciation was investigated. Wearing 7 kinds of experimental artificial teeth with the upper posterior ones arranged in 7 different positions, patients pronounced 5 test sounds: "ka", "ki", "kw", "ke" and "ko". Resultant sounds were evaluated in terms of how the bucco-lingual position of posterior artificial teeth influenced pronunciation as determined with by aural pronunciation judgment test and frequency analysis using a 1/3 octave-band real-time analyzer. Pronunciation disorders caused by the arrangement of the upper posterior artificial teeth in complete dentures occur when the lingual surfaces of the upper molars is located more than 1/4 inward of the distance between the right and left denture border from the buccal denture border or less than 1/10 of that distance outward from the buccal denture border. Results of the aural pronunciation judgment test indicated that the influence of the arrangement of the upper posterior artificial teeth on pronunciation depends on the vowel following the consonant of the sound. When the vowel following the consonant is a back vowel, as in "ka", "kw" and "ko" the sound was barely influenced, but when the vowel is a front vowel. as in "ke" and "ki", the sound was markedly influenced. We established the frequency spectrum of the consonant of the normally pronounced 5 test sounds as the standard frequency spectral range and compared distorted and misheard sounds with it.(ABSTRACT TRUNCATED AT 250 WORDS)     

Loading of a unilateral temporomandibular joint prosthesis: a three-dimensional mathematical study

The load on the prosthetic side and the influence of the design on the remaining natural contralateral TMJ must be known before a unilateral temporomandibular joint (TMJ) prosthesis can be developed. The aim of the present study was to determine the maximum loading of the TMJ prosthetic side and the natural contralateral TMJ and to investigate the influence of the location of the center of rotation of the prosthesis on the maximum loading. For this purpose, a mathematical model of the mandible with a unilateral TMJ prosthesis with a fixed center of rotation (CR) was developed. The location of the CR of the TMJ prosthesis was varied from the middle of the natural mandibular condyle to 15 mm inferior to this location. Although the maximum joint reaction forces changed as a result of a unilateral TMJ prosthesis, the trend of the loading curves was similar to that of an intact mandible. A unilateral TMJ prosthesis resulted in a 50% higher loading of the prosthetic side, while the load on the natural contralateral TMJ remained within normal limits. The maximum load on the prosthetic side occurred during molar bites and could reach 100 N in the cranial direction, 30 N in the ventral direction, and 25 N in the medio-lateral direction. The location of the CR did not have a significant influence on the loading of the TMJ prosthesis and the natural contralateral TMJ.     

Anti-inflammatory drugs and endothelial cell adhesion molecule expression in murine vascular beds

STATEMENT OF PROBLEM: There are discrepancies among researchers concerning the reliability and use of temporomandibular joint sounds. PURPOSE: This study examined the reliability of mandibular movements and sounds and determined the correlation between movements and sounds. MATERIAL AND METHODS: The mandibular movements of 35 subjects diagnosed with temporomandibular disorders were recorded with 2 CCD cameras, and sounds were recorded bilaterally with Panasonic electret condenser microphones in the ear canal. Subjects performed 3 movements, each repeated 5 times. RESULTS: Reliability of maximum movements across the 5 trials was good to excellent, with Intraclass Correlation Coefficients (ICC) between 0.76 and 0.91 for all movements except protrusion. Temporomandibular sound event counts were reliable for most movements, including vertical opening, protrusion, and right and left laterotrusion (ICCs between 0.41 and 0.81). Most subjects produced sound events either in 100% or in none of the trials. Reliability for sound events was better during protrusion (ICCs between 0.56 and 0.81) than vertical opening (ICCs 0.41 to 0.64). Subjects with sound events during vertical opening (followed by closing) were significantly more likely to have sound events during protrusion (followed immediately by vertical opening and closing) (P <.01). CONCLUSION: Temporomandibular sound events are generally reliable and warrant study regarding their use in classifying and diagnosing patients with temporomandibular disorders. Condylar translation, which occurs during both vertical opening and protrusion, appears to have a strong influence on the production of temporomandibular sound events.     

Symptoms of the stomatognathic system in temporomandibular and cervical spine disorders

This study was performed to assess the prevalence of signs and symptoms of temporomandibular disorders (TMD) in patients with cervical spine disorders (CSD) and to compare patients with CSD and subgroups of patients with TMD with regard to the results of orthopaedic tests of the stomatognathic system. A group of 103 consecutive patients with signs and symptoms of CSD and a group of 111 consecutive patients with TMD were examined. All subgroups of TMD patients showed a significantly smaller range of motion than the CSD patients. Patients with TMD had limited mouth opening (< 40 mm) on active and passive mouth opening more often than CSD patients. TMD patients with myogenous problems reported oral habits more often than CSD patients, although no objective differences between CSD and TMD patients were found. Subgroups of TMD patients reported joint sounds, and pain on palpation and joint play tests of the temporomandibular joint (TMJ) more frequently than CSD patients. Joint sounds on active movements, pain on palpation of the TMJ, and pain on joint play tests correctly classified 82% of the patients with TMD and 72% of the patients with CSD. In spite of the biomechanical and anatomical relationship between the neck and the stomatognathic system, the results of the study show that CSD patients have signs and symptoms of TMD comparable with those of the adult Dutch population. It was concluded that the function of the masticatory system should be evaluated in patients with neck complaints in order to rule out a possible involvement of the masticatory system.     

Multichannel (Ineraid) cochlear implant update

From April 1984 to May 1991, 49 profoundly deaf patients received implantation of the Ineraid multichannel cochlear implant at the University of Utah. The auditory results of 48 patients indicated improvement in mean pure-tone performance to 500 Hz (32.9 +/- 10.1 dB), 1000 Hz (27.1 +/- 10.0 dB), and 2000 Hz (30.1 +/- 9.8 dB). This group of patients had mean performances of 61.2% on auditory-only environmental sounds (Minimum Auditory Capabilities [MAC] battery), 48.8% on auditory-only CID sentences, and 95.5% on auditory-plus-visual CID sentences. The percutaneous pedestal has been well-tolerated. Changes in the surgical skin incisions have been made. A home use speech therapy program has been developed on VHS tapes.     

Central NO is involved in the antinociceptive action of intracisternal antidepressants in freely moving rats

The present study was performed to examine the central effects of antidepressants on nociceptive jaw opening reflex after intracisternal injection. we also investigated the mechanisms of central antinociceptive action of intracisternal antidepressants. We recorded the jaw opening reflex in freely moving rats and chose to administer antidepressants intracisternally in order to eliminate the effects of anesthetic agents on the pain assessment and evaluate the importance of the spinal site of action of antidepressants. After intracisternal injection of 15 microg imipramine, digastric electromyogram (dEMG) was decreased to 76+/-6% of the control. Intracisternal administration of 30 microg desipramine, nortriptyline or imipramine suppressed dEMG remarkably to 48+/-2, 27+/-8, or 25+/-5% of the control, respectively. The suppression of dEMG was maintained for 50 min. L-NG-Nitroarginine methyl ester (NAME) blocked the suppression of dEMG from 32+/-2 to 81+/-5% of the control. These results indicate that antidepressants produce antinociception through central mechanisms in the orofacial area. The central NO pathway seems to be involved in the antinociception of intracisternal antidepressants at supraspinal sites.     

Factors responsible for computed electrogastrographic parameters in humans

OBJECTIVES: Clinical knowledge about myoelectrical frequency is well known, but the factors responsible for recorded myoelectrical amplitude remain less clear. METHODS: We assembled an electrogastrographic system that could automatically compute the dominant myoelectrical frequency and power and power ratio. We enrolled 50 healthy volunteers (25 men and 25 women) to study their myoelectrical characteristics. Three surface electrodes were placed in the fundic, stomach body, and antral positions for two 30-min recordings in the fasting and postprandial states. RESULTS: The three different electrodes recorded similar dominant frequencies of about 3 cpm before and after a meal. The fasting dominant powers from these electrodes were 52.9 +/- 14.7, 44.6 +/- 11.5, and 50.1 +/- 15.1 dB, respectively (p < 0.01), whereas the postprandial dominant powers were 61.6 +/- 28.8, 54.3 +/- 26.6, and 61.9 +/- 27.8 dB, respectively (p < 0.01). Meal ingestion did increase the power (p < 0.05). Women had a lower dominant power than men (p < 0.001). Moreover, the dominant powers of each electrode were significantly correlated with body mass index (r = 0.3-0.36, p < 0.05) regardless of meal ingestion. The postprandial power ratio was not influenced by electrode position, gender, or body mass index. CONCLUSIONS: Myoelectrical dominant frequencies and power ratios are similar throughout the whole stomach area, whereas a lower power area exists on the stomach body. Gender-related variation in dominant power seems to be an effect of body size. The power ratio is the only reliable parameter for expressing myoelectrical amplitude.     

A novel sodium channel mutation causing a hyperkalemic paralytic and paramyotonic syndrome with variable clinical expressivity

BACKGROUND: The CarboMedics valve is a relatively new, low-profile, bileaflet, mechanical prosthesis. The results of a prospective follow-up study after valve replacement with this prosthesis in a university hospital are presented. METHODS: We implanted 640 CarboMedics prostheses in 583 patients in the aortic (n = 359), mitral (n = 167), or aortic and mitral positions (double valve replacement; n = 57). Patient ages ranged from 11 to 81 years (mean age, 58 +/- 12.3 years). RESULTS: Overall hospital mortality was 9.0%; however, when high-risk urgent cases were removed from the calculation, the operative mortality fell to 4.5%. Follow-up was 98% complete, comprising 2,027 patient-years for a mean follow-up of 44 months (range, 6 to 72 months). Actuarial freedom from complications (linearized rates in parentheses) was as follows: late mortality, 85% +/- 2.0% (2.3%/patient-year); thromboembolism, 92% +/- 1.1% (1.6%/patient-year); anticoagulation-related hemorrhage, 87% +/- 1.2% (2.8%/patient-year); prosthetic valve endocarditis, 98% +/- 0.5% (0.1%/patient-year); and overall valve-related morbidity and mortality, 76% +/- 2.1% (4.3%/ patient-year). CONCLUSIONS: The CarboMedics valve shows a low rate of valve-related complications comparable with other new mechanical heart valve prostheses.     

Enhancement of opsin activity by all-trans-retinal

This study examines the hemodynamic performance of small size St. Jude BioImplant aortic prostheses using dobutamine echocardiography. Eleven patients (3 women, mean age 75 years) who had undergone aortic valve replacement with a size 21-mm St. Jude BioImplant aortic prostheses at 10.8 +/- 5.1 months (SD) previously were studied. Dobutamine infusion was started at a rate of 5 microg/kg/min and increased to 10 microg/kg/min, and subsequently to 20 microg/kg/min at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, mean gradient, and the performance index across each prosthesis were calculated and cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract. Stress dobutamine increased heart rate and cardiac output by 51% and 56%, respectively (both p <0.0001), and the mean transvalvular gradient increased from 30.1 +/- 7.5 mm Hg at rest to 49.3 +/- 11.5 mm Hg at maximum stress (p <0.0005). The performance index increased progressively from 0.29 +/- 0.05 at rest to 0.40 +/- 0.10 at maximum stress (p <0.0005). Regression modeling analyses demonstrated that the maximum stress gradient was independent of all variables except the resting gradient (p = 0.03). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. Thus, these data demonstrate that the size 21-mm St. Jude BioImplant prosthesis exhibits suboptimal hemodynamic performance with transvalvular gradients consistent with mild to moderate aortic stenosis, both at rest and under stress conditions.     

Effect of prosthesis type and size on the hemodynamic response of mitral valve prostheses to exertion

BACKGROUND: Doppler echocardiography is current tool for hemodynamic evaluation of mitral prosthetic heart valves. It's accepted that the area and the gradients by Doppler echocardiography are not influenced at rest by valvular type and valvular size. We evaluated the influence of valvular type, mechanical-biological, and size on exercise hemodynamic of normally-functioning mitral prosthesis. Thirty-seven patients with mitral prosthesis, mean age 56 +/- 10 years, underwent exercise Doppler echocardiography. Peak and mean prosthetic gradient were obtained at rest, during and at maximal exercise with a nonimaging transducer. Mechanical prosthesis were 23 and biological valves 14. Valvular size was less than 26 mm in 7 patients and more than 28 mm in 20 patients. Exercise increased the heart rate from 80 +/- 14 to 143 +/- 22 (p < 0.001), peak gradient from 11.4 +/- 4 to 26.1 +/- 7 mm Hg (p < 0.001) and mean gradient from 4.8 +/- 1 to 13.7 +/- 5 mm Hg (p < 0.001). We found similar peak (11.4 +/- 3 & 11.3 +/- 4) and mean gradient (3.4 +/- 1 & 2.9 +/- 0.7) at rest between mechanical and biological valves; at maximum exercise, peak (26 +/- 7 & 26 +/- 6) and mean gradient (13.9 +/- 6 & 13.2 +/- 4) were also similar. Prosthesis with > 28-mm-size compared with prosthesis < 26-mm-size showed minor peak gradient at second step (21.3 +/- 4 & 26.4 +/- 6, p < 0.05) and at peak exercise (25.4 +/- 7 & 29.8 +/- 8, ns). Hemodynamics on exercise using Doppler echocardiography was not influenced by valvular type (mechanical-biological) in normal mitral prosthesis. However, mitral prosthesis of small size showed worse on hemodynamics exercise than bigger ones.     

The effect of food consistency upon jaw movement in the macaque: a cineradiographic study

Variation in the form of masticatory cycles in individuals is often assumed to be limited. The contrary hypothesis, that jaw cycles vary widely but systematically with food consistency, was tested in macaques fed similarsized pieces of monkey chow, apple, and banana. With the animals under general anesthesia, radiopaque markers were inserted into the jaw, tongue, and hyoid. Oral movements were recorded by cineradiography at 100 frames/sec in lateral projection synchronously with frontal view cinephotography (50 frames/sec). The films were examined for the events that subdivide each jaw movement cycle into its constituent phases (fast closing, slow closing, intercuspal, slow or early opening, final opening). The frame numbers at which these events occurred were used to define phase durations. The numbers of cycles preceding a swallow increased with the hardness of the ingested food item. Regardless of the test food, every feeding sequence (initial ingestion to final clearance of mouth) contained multiple swallows, each of which defined the end of a sub-sequences when the animals were feeding on chow, the sub-sequences were initially long (20 cycles or more), but when they were feeding on banana, the sub-sequences were short (10 cycles or fewer). Although the form of individual cycles (defined by phase durations) was often unrelated to that of neighboring cycles, the general cycle characteristics in a sub-sequence typified a particular food. Chow feeding cycles were characterized by slow-closing (SC) phases of long duration with slow-opening (SO) phases of short duration; the characteristics of banana feeding cycles were the reverse. SC duration correlated directly and SO duration correlated inversely with food hardness (p < 0.001). The evidence supports the view that the centrally generated pattern of movement is highly dependent upon intra-oral sensory feedback.     

Mitral valve replacement with the St. Jude Medical prosthesis: a 15-year follow-up

BACKGROUND: A retrospective study was conducted to analyze the results of St. Jude Medical mitral valve replacement. METHODS: From January 1979 to December 1989, 870 patients (54% women, 46% men; mean age, 55.8 +/- 6.2 years) underwent mitral valve replacement with the St. Jude Medical prosthesis. Of these operations 616 were isolated mitral valve replacements and 254 were double valve replacements. Coronary artery bypass grafting was performed concomitantly in 55 patients (6.3%). RESULTS: Overall, early mortality was 5.05%, with 4.2% for the isolated mitral valve procedure and 7.08% for the double valve replacement. Follow-up at 15 years was complete in 859 patients (98.74%). Mean follow-up time was 93.5 months, for a total of 6,436 years. Actuarial survival at 15 years was 59.5% +/- 5%, 60.5% +/- 6%, and 56.9% +/- 9%, for the entire group, the isolated mitral valve and double valve procedures, respectively. Multivariate analysis identified age, sex, hospital stay, and preoperative mitral regurgitation as independent prognosis factors for overall mortality. Of 606 patients alive at the latest follow-up, the New York Heart Association class improved significantly (from 67% class III/IV before the operation to 88% class I/II after the operation). All patients received warfarin to maintain an international normalized ratio between 3.5 and 4. The linearized rates (% per patient-year) of thrombosis, thromboembolism, and major hemorrhage were, respectively, 0.21, 0.75, and 0.94 for the entire group; 0.18, 0.67, and 0.88 for the isolated mitral valve operation; and 0.15, 0.92, and 1.08 for the double valve replacement. For the entire group the freedom from thrombosis and thromboembolism at 15 years was 98.1% +/- 1% and 88% +/- 4%, respectively. No case of structural dysfunction occurred. The freedom from paravalvular leak and endocarditis at 15 years was 95.3% +/- 2% and 97.3% +/- 2.4%, respectively. The probability of remaining free from reoperation at 15 years was therefore 95.6% +/- 2.5%. CONCLUSIONS: These results confirm that the St. Jude Medical valve is a reliable prosthesis with very low thrombosis and thromboembolism rates, allowing the use of a low dose of anticoagulation with an international normalized ratio of about 3.     

The effect of halothane on the amplitude and frequency characteristics of heart sounds in children

Although continuous auscultation has been used during surgery as a monitor of cardiac function for many years, the effect of anesthetics on heart sounds has never been quantified. We determined the root mean squared amplitude and frequency characteristics (peak frequency, spectral edge, and power ratios) of the first (S1) and second (S2) heart sounds in 19 healthy children during induction of anesthesia with halothane. In all patients, halothane decreased the amplitude of S1 (R2 = 0.87 +/- 0.12) and S2 (R2 = 0.66 +/- 0.33) and the high-frequency components (>80 Hz) of these sounds. These changes were clearly audible and preceded decreases in heart rate and blood pressure. The spectral edge decreased for S1 in 18 patients (R2 = 0.73 +/- 0.24) and for S2 in 13 patients (R2 = 0.58 +/- 0.25). Peak frequency did not change. The rapidity with which myocardial depression and its associated changes in heart sound characteristics occurred confirms that continuous auscultation of heart sounds is a useful clinical tool for hemodynamic monitoring of anesthetized infants and children. Implications: Heart sound characteristics can be used to monitor cardiac function during halothane anesthesia in children. The changes occur rapidly and precede noticeable changes in heart rate and blood pressure.