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Biomedical subjects

M V Kamath

Publications and source records attributed to M V Kamath.

52 records · Page 3Linked to original sources
PubMed1988

Spectral analysis of heart rate variability following human heart transplantation: evidence for functional reinnervation.

To determine the status of innervation in long-term human donor allografts, the power spectrum of heart rate variability was analysed in 9 post-transplant patients and 7 healthy control subjects. The mean post-transplant follow-up was 17.8 months (range: 2-37 months). Continuous ECG signals were recorded throughout a 15-min rest period. An R-R interval tachogram was generated and an autoregressive model using linear predictive coding, was applied to the heart rate variability data. In 8 transplant patients the frequency oscillations were irregular, broad based and widely dispersed from 0 to 1 Hz. The patterns resembled white noise and were consistent with dissociation of the donor allograft from the recipient's central nervous system. In contrast, one patient displayed a heart rate variability spectrum indistinguishable from that of control subjects. This pattern contained two distinct spectral bands; one corresponding to the patient's respiratory rate at 0.2 Hz and a low frequency Mayer wave at 0.1 Hz. Atropine abolished the respiratory (vagal) peak. Except for this patient's post-transplant time (33 months compared to the group mean of 17.6 months), there were no clinical characteristics which distinguished this patient from the others. While the mean heart rate for the remaining 8 allografts was significantly higher than controls (95.3 vs 64.5 bt/min; P less than 0.001) the standard deviation of heart rate variability for the 8 patients was significantly narrower than controls (0.7 vs 4.86; P less than 0.01). The variance of heart rate for the patient with the normal power spectrum was fourfold greater than the mean SD of the other transplant patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Repair of aneurysms of the thoracic aorta: 12-year experience in a high-risk population.

We present our 12-year experience with surgical treatment of aneurysms of the thoracic aorta in a high-risk patient population. Of 52 patients with aneurysms, 36 patients, aged 19 to 80 years, had operation. In 24 of the 36, there were three or more associated major disease processes, such as chronic bronchitis, hypertensive cardiovascular disease, aortic valve disease, cerebrovascular disease, abdominal aortic aneurysm, and coronary artery disease. Eight patients with acute type A (ascending aorta) and seven with acute type B (descending aorta) aneurysms had emergency repair, with survival in four and seven, respectively. All patients with chronic type A or B aneurysms had elective repair, and all patients with acute or chronic type A aneurysms had surgical treatment. Four patients with acute type A and two with acute type B aneurysms had elective operation, with survival in three and one, respectively. Nine patients with chronic type A and six with chronic type B aneurysms had elective operation, and all survived. Twelve patients with chronic type B aneurysms did not have operation, and all were alive at early follow-up. Mortality for patients having acute type A aneurysms requiring emergency operation was greater than that after elective repair of acute or chronic type A aneurysms. Short-term survival for chronic type B aneurysms was similar whether the patient was treated medically or surgically.

Aorta, Thoracic↗
PubMed1988

Combined paraesophageal and sliding hiatal hernia.

We have reported a case of a large paraesophageal herniation with a small sliding component. Abnormal positioning of the esophagogastric junction or the necessity for mobilizing it during repair requires the addition of an antireflux procedure to the standard reduction and repair. Elective repair of a paraesophageal herniation, even in the absence of limiting symptoms, is warranted, since complications of nonsurgical treatment may be sudden and severe.

Esophagogastric Junction↗
PubMed1988

Radiological changes in rheumatoid arthritis: measurement of area of juxta-articular bone as outcome event in clinical therapeutic trials of antirheumatic drugs.

A high degree of intra - and inter - rater reproducibility was obtained in measurement of a standardized area of the head of the first right metacarpal using a precision digitizer. This instrument had an accuracy for every point digitized of 0.127 mm. Intra-rater difference between readings at approximately a month's interval showed no significant differences. The method is reasonably simple to perform and is applicable to small joints such as the proximal interphalangeal joints. The method may prove useful in following progression of joint damage in rheumatoid arthritis.

Anti-Inflammatory Agents↗
PubMed1988

Power spectrum of heart rate variability: a non-invasive test of integrated neurocardiac function.

Under steady state conditions, frequency specific oscillations in the heart rate record reflect beat-to-beat autonomic control of sinus node activity. Using an autoregressive model, samples (2.5 min) of continuous ECG records were analyzed in 36 healthy young adults during supine rest (45 min), orthostatic stress and controlled respiration. In the supine state, constancy of heart rate was achieved (mean HR 62.8 bt/min +/- 4.88 SD). However, the 0.1 Hz peak spectral power varied considerably: average coefficient of variation was 34% compared to only 8% for heart rate. When breathing rates were synchronized to a metronome there was a small insignificant decrease in the peak power at 0.1 Hz compared to spontaneous respiration. Standing produced a significant increase in the peak power at 0.1 Hz especially during synchronized breathing. There was a maximum increase in the low frequency (0.1 Hz) peak power of 40 (bt/min)2. Hz-1 at a controlled breathing frequency of 0.25 Hz in the standing compared to supine position. The data show that reproducibility of the power spectrum heart rate variability is best achieved at controlled but physiologic respiratory rates and, preferably, in the upright position.

Adult↗
PubMed1987

Heart rate variability power spectrogram as a potential noninvasive signature of cardiac regulatory system response, mechanisms, and disorders.

This paper attempts to provide evidence that the heart rate variability power spectrum (HRVPS) reflects the presence of neural control of cardiac regulation. A normal individual is seen to have a characteristic HRVPS (comprising a 0.1-Hz peak and a respiratory peak at 0.25-0.34 Hz), which is altered in a predictable manner in response to orthostatic stress and exercise, while in two patients with autonomic neuropathy, the HRVPS failed to demonstrate such a characteristic alteration in response to orthostatic stress. Postinfarct HRVPS signatures were studied in two patients with anterior and inferior infarcts so as to lend insight using non-invasive means into both the healing process and the dominant deliterious sympathetic or protective vagal tone due to the infarct. When subjects with transplanted hearts were studied, their HRVPS did not exhibit the characteristic pattern of a normal individual; rather, the HRVPS energy was spread over a wider and higher frequency range. However, one of the transplanted patients surprisingly but consistently revealed the characteristic HRVPS; the post-transplant time at the time of the study was 33 months and the patient had the typically high resting heart rate of a transplant recipient but a wide standard deviation like that of a normal individual. This could be the first noninvasively demonstrated evidence in humans of reinnervation of a transplanted heart. Thus, the HRVPS constitutes a simple non-invasive method to assess cardiac neuroregulatory response and disorders and it is proposed that it be referred to as the heart rate variability cardiogram (HRVC).

Adult↗
PubMed1987

Power spectral analysis of normal and pathological brainstem auditory evoked potentials.

The brainstem auditory evoked potential (BAEP) recording has become a powerful investigational tool in neurological diagnosis. The BAEPs of patients have different latencies and morphologies when compared to those of normals. In this paper the power spectra (PS) of BAEPs of 21 normals, 17 patients with multiple sclerosis (MS) and 12 patients with head injury (HI) computed by Blackman-Tukey (BT) and Maximum Entropy (ME) methods are examined for their frequency composition. Three major peaks appear at approximately 170 Hz, 520 Hz and 950 Hz in PS of normal BAEPs. The average power contained in the frequency bands spread around these frequency bands for BAEPs of patients differed significantly (P less than 0.05) from those of normal BAEPs. The peaks observed in ME spectra were found to match those computed using BT method. The model order for representing both normal and patient BAEPs is greater than 40 and data compression afforded by modelling the BAEPs is of the order of 5:1.

Adolescent↗
PubMed1987

Esophageal mucocele: a complication of blind loop esophagus.

Mucocele of the bypassed esophagus is an unusual complication of esophageal replacement and has been described only in isolated references. This report is based on our experience with 6 patients in whom a mucocele developed following esophageal replacement. Esophageal replacement was performed on 37 patients over a 10-year period at the Medical College of Georgia Hospital. A symptomatic mucocele requiring excision developed in 3 patients with achalasia, 1 with congenital tracheoesophageal fistula, 1 with esophageal atresia, and 1 with inflammatory stricture. Conduits used included stomach (4), reversed gastric tube (1), and colon (1). Our experience indicates that conversion of a closed-loop esophagus into a symptomatic mucocele is more likely in the presence of functioning, chronically irritated mucosa. The clinical features were referable to the mucocele itself or respiratory embarrassment therefrom. Thoracic roentgenograms and computed tomographic scans were diagnostic in verifying the presence of the esophageal mucocele. All five mucoceles arose from squamous epithelium. One of 3 patients with achalasia in whom a mucocele developed following esophageal replacement had premalignant changes in the mucosa. Based on this experience, our treatment of choice is early, complete excision of the mucocele.

Esophageal Diseases↗
PubMed1987

Disc immobilization of Björk-Shiley and Medtronic Hall valves during and immediately after valve replacement.

During the last fourteen years, 377 unileaflet tilting-disc prosthetic valves (Björk-Shiley and Medtronic Hall) have been used for single or multiple valve replacements with and without concomitant coronary artery by-pass grafting. In the past five years, five instances of disc immobilization (three in the mitral and two in the aortic position) occurred either at the time of weaning from cardiopulmonary bypass or immediately thereafter. When the implanted site of the prosthetic valve was the mitral position, reexploration in 2 patients revealed chordal remnants in the subannular area stuck between the disc occluder and the valve ring, thereby immobilizing the disc. In the third instance, the free movement of the disc was impeded by the left ventricular myocardium. In the aortic position, an unraveled suture impacted between the disc occluder and the valve ring immobilized the disc in 1 patient. In the other patient, the cause of the malfunction could not be determined at the time of reexploration. The 1 death among these 5 patients was directly related to the malfunction of the prosthesis. The mechanism, recognition, treatment, and prevention of this catastrophic malfunction of tilting-disc valves are discussed.

Adult↗
PubMed1985

The effects of local cooling on canine spinal cord blood flow.

The internal spinal cord blood flow was measured in dogs at the site of local cooling using hydrogen polarography. Blood flow decreased to 50% of the normothermic values during cooling of the cord to a central temperature of 16 degrees Celsius. Upon cessation of cooling internal blood flow rapidly returned to normal values. Implications of this finding for the treatment of spinal cord injury are discussed.

Animals↗