Post-implant Period Research Articles

Effect of post-implant edema on prostate brachytherapy treatment margins

To determine if postimplant prostate brachytherapy treatment margins calculated on Day 0 differ substantially from those calculated on Day 30. Thirty patients with 1997 American Joint Commission on Cancer clinical stage T1-T2 prostatic carcinoma underwent prostate brachytherapy with I-125 prescribed to 144 Gy. Treatment planning methods included using loose seeds in a modified peripheral loading pattern and treatment margins (TMs) of 5-8 mm. Postimplant plain radiographs, computed tomography scans, and magnetic resonance scans were obtained 1-4 hours after implantation (Day 0). A second set of imaging studies was obtained at 30 days after implantation (Day 30) and similarly analyzed. Treatment margins were measured as the radial distance in millimeters from the prostate edge to the 100% isodose line. The TMs were measured and tabulated at 90 degrees intervals around the prostate periphery at 0.6-cm intervals. Each direction was averaged to obtain the mean anterior, posterior, left, and right margins. The mean overall TM increased from 2.6 mm (+/-2.3) on Day 0 to 3.5 mm (+/-2.4) on Day 30. The mean anterior margin increased from 1.2 mm on Day 0 to 1.8 mm on Day 30. The posterior margin increased from 1.2 mm on Day 0 to 2.8 mm on Day 30. The lateral treatment margins increased most over time, with mean right treatment margin increasing from 3.9 mm on Day 0 to 4.7 mm on Day 30. Treatment margins appear to be durable in the postimplant period, with a clinically insignificant increase from Day 0 to Day 30.

A new equine pericardial stentless valve

Objective Small aortic valve replacement remains a challenging hemodynamic problem. A new bioprosthesis (3F Therapeutics, Lake Forest, Calif) was designed to further improve the hemodynamic performance currently achieved with stentless bioprostheses. This valve consists of a tubular structure assembled from 3 equal sections of equine pericardial material, with virtually no foreign material except for a thin polyester ring. Its hemodynamic performance was compared with that of a commercially available stentless prosthesis in a bovine model. Patients and methods Twelve calves (55 ± 2.8 kg) received a 19-mm 3F valve (3F group, n = 6) or a 19-mm stentless control valve (control group, n = 6). The animals were fully equipped for hemodynamic monitoring and transvalvular gradient measurements. After implantation, dopamine was infused in increasing doses, and the hemodynamic values were recorded at each step of 100-μg/min increase. Linear regression analysis was applied for group comparison of each variable. Results The mean transvalvular gradient at 4.5 L/min was 3.48 ± 0.14 mm Hg (95% confidence interval) in the 3F group and 5.72 ± 0.28 mm Hg in the control group ( P < .0001) and at 6.5 L/min, 7.4 ± 1.55 mm Hg, and 11.13 ± 0.18 mm Hg, respectively ( P < .0001). The effective orifice area at 4.5 L/min was 2.4 ± 0.03 cm 2 in the 3F group and 1.86 ± 0.02 cm 2 in the control group ( P < .0001) and at 6.5 L/min, 2.41 ± 0.04 cm 2, and 1.96 ± 0.02 cm 2, respectively ( P < .0001). Conclusions This new bioprosthesis without a stent and without a supporting wall that has its commissures fixed directly to the aorta outperforms in vivo standard stentless prostheses in the immediate postimplant period.

Perioperative considerations in the patient with a left ventricular assist device.

Perioperative considerations in the patient with a left ventricular assist device.

The effect of androgen deprivation on the early changes in prostate volume following transperineal ultrasound guided interstitial therapy for localized carcinoma of the prostate

Purpose: To determine the change in volume of the prostate as a result of neoadjuvant androgen deprivation prior to prostate implant and in the early postimplant period following transperineal ultrasound guided palladium-103 brachytherapy for early-stage prostate cancer. Methods and Materials: Sixty-nine men received 3 to 6 months of androgen deprivation therapy followed by treatment planning ultrasound followed 4 to 8 weeks later by palladium-103 implant of the prostate. All patients had clinical and radiographic stage T1c–T2b adenocarcinoma of the prostate. A second ultrasound study was carried out 11 to 13 days following the implant to determine the change in volume of the prostate as a result of the implant. The prehormonal and preimplant volumes were compared to the postimplant volume to determine the effect of hormones and brachytherapy on prostate volume. Results: The median decrease in prostate volume as a result of androgen deprivation was 33% among the 54 patients with prostate volume determinations prior to hormonal therapy. The reduction in volume was greatest in the quartile of men with the largest initial gland volume (59%) and least in the quartile of men with smallest glands (10%). The median reduction in prostate volume between the treatment planning ultrasound and the follow-up study after implant was 3%, but 23 (33%) patients had an increase in prostate volume, including 16 (23%) who had an increase in volume >20%; 11 of these patients (16%) had an increase in volume >30%. The time course of development and resolution of this edema is not known. The severity of the edema was not related to initial or preimplant prostate volume or duration of hormonal therapy. Conclusions: Prostate edema may significantly affect the dose delivered to the prostate following transperineal ultrasound guided brachytherapy. The effect on the actual delivered dose will be greater when shorter lived isotopes are used. It remains to be observed whether this edema will affect outcome.

A 4-year investigation into phonetic inventory development in young cochlear implant users.

Phonetic inventories of 9 children with profoundly impaired hearing who used the 22-electrode cochlear implant (Cochlear Limited) were monitored before implantation and during the first 4 years of implant use. All children were 5 years old or younger at the time of implant. Spontaneous speech samples were collected at regular intervals for each child and analyzed to investigate phone acquisition over the post-implant period. Acquisition was measured using two different criteria. The "targetless" criterion required the child to produce a phonetically recognizable sound spontaneously, and the "target" criterion required the child to produce the phone correctly at least 50% of the time in meaningful words. At 4 years post-implant, 40 out of 44 phones (91 %) had reached the targetless criterion, and 29 phones (66%) had reached the target criterion for 5 or more of the children. Over the time of the study 100% of monophthongs, 63% of diphthongs, and 54% of consonants reached the target criterion. The average time taken for a phone to progress from the targetless to target criterion was 15 months. Overall, the data suggest trends in the order of phone acquisition similar to those of normally hearing children, although the process of acquisition occurred at a slower rate.

Circadian variations in minute ventilation can be reproduced by a pacemaker sensor.

Special software allowing the memorization of 24-hour minute ventilation can be loaded into the memory of the Chorus RM, a DDDR pacemaker driven by minute ventilation. This feature was tested in the postimplant period in 13 patients. Measurements of minute ventilation, respiratory rate, and respiratory amplitude were analyzed according to prospectively defined diurnal and nocturnal time periods. Minute ventilation decreased by 39% (P < 0.001) from the diurnal to the nocturnal phase, while respiratory rate and amplitude decreased by 18% and 28%, respectively (P < 0.001 each). Thus, minute ventilation allowed discrimination between sleep and waking hours. This information could be utilized to modulate the backup rate of the pacemaker.

Stability of the input-output properties of chronically implanted multiple contact nerve cuff stimulating electrodes.

The objective of this investigation was to measure the input-output (I-O) properties of chronically implanted nerve cuff electrodes. Silicone rubber spiral nerve cuff electrodes, containing 12 individual platinum electrode contacts, were implanted on the sciatic nerve of seven adult cats for 28-34 weeks. Measurements of the torque generated at the ankle joint by electrical stimulation of the sciatic nerve were made every 1-2 weeks for the first 6 weeks post-implant and every 3-5 weeks between 6 weeks and 32 weeks post-implant. In three implants the percutaneous lead cable was irreparably damaged by the animal within 4 weeks after implant and further testing was not possible. One additional lead cable was irreparably damaged by the animal at 17 weeks post-implant. The three remaining implants functioned for 28, 31, and 32 weeks. Input-output curves of ankle joint torque as a function of stimulus current amplitude were repeatable within an experimental session, but there were changes in I-O curves between sessions. The degree of variability in I-O properties differed between implants and between different contacts within the same implant. After 8 weeks, the session to session changes in the stimulus amplitude required to generate 50% of the maximum torque (I50) were smaller (15+/-19%, mean +/- s.d.) than the changes in I50 measured between 1 week and 8 weeks post-implant (34+/-42%). Furthermore, the I-O properties were more stable across changes in limb position in the late post-implant period than in acutely implanted cuff electrodes. These results suggest that tissue encapsulation acted to stabilize chronically implanted cuff electrodes. Electrode movement relative to the nerve, de- and regeneration of nerve fibers, and the inability to precisely reproduce limb position in the measurement apparatus all may have contributed to the variability in I-O properties.

Effects of melatonin in the mediobasal hypothalamus on the secretion of gonadotrophins in sheep: role of dopaminergic pathways.

Previous studies have shown that treatment with micro-implants of melatonin in the mediobasal hypothalamus (MBH) of sexually inactive Soay rams exposed to long days induces an increase in the secretion of FSH and reactivation of the testicular axis, as normally occurs in response to short days. The current study was conducted to investigate the possible involvement of hypothalamic dopaminergic (DA) systems in this melatonin-induced effect. At 10 weeks under long days, sexually inactive Soay rams were treated in the MBH with micro-implants containing bromocriptine (DA agonist) or sulpiride (DA antagonist), given alone or in combination with melatonin, to establish whether the DA drugs would mimic or negate the effects of melatonin. All micro-implants were inserted bilaterally and left in place for 14 weeks; the study lasted a total of 28 weeks (14 weeks implant period and 14 weeks post-implant period) while the animals remained under long days. The ability of the micro-implants to release bromocriptine and sulpiride for 14 weeks was confirmed by incubating implants in vitro and testing for the presence of the compounds in the incubate using a pituitary cell bioassay. Profiles of FSH, determined in blood samples collected three times weekly, were significantly different among treatments (time x treatment interaction, P < 0.001, ANOVA). Melatonin in the MBH induced a marked increase in the concentrations of FSH during the implant period, and a decrease during the post-implant period (P < 0.001). Bromocriptine given alone in the MBH induced a decrease in the concentrations of FSH which became statistically different from the control during the post-implant period (P < 0.05). Treatment with sulpiride alone also resulted in a suppressive effect during the post-implant period (P < 0.01). When given in combination with melatonin, bromocriptine or sulpiride significantly reduced the melatonin-induced increase in the concentrations of FSH observed during the implant period (P < 0.001). The results support the view that DA pathways in the MBH play an important role in the inhibitory regulation of gonadotrophin secretion in the ram. The inhibitory effect of bromocriptine is likely to result from the direct activation of the hypothalamic DA receptors linked to GnRH neurones regulating the secretion of FSH. The apparent paradoxical inhibitory effect of sulpiride is thought to be due to enhanced gonadal steroid negative feedback resulting from blockade of the inhibitory DA pathways, as evidenced by significantly increased secretion of testosterone (P < 0.05) in the animals receiving sulpiride in combination with melatonin.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of bovine follicular fluid and luteinizing-hormone-releasing hormone antagonist on the dominant follicle maintained by a norgestomet ear implant in heifers

The effects of BFF and LHRHa on the dominant follicle, maintained by 9-d synthetic progestin (norgestomet) ear implants inserted at proestrus, were studied in cattle. From day 4 of implant insertion, heifers (n = 18) were injected twice daily with saline (control, n = 6) or charcoal-extracted bovine follicular fluid, 10 mL i.v. for 4 d (BFF, n = 6) or LHRHa, 0.8 mg i.v. for 3 d (LHRHa, n = 6). Follicular changes were monitored daily by ultrasonography. Plasma estradiol-17β, serum LH and FSH were measured by radioimmunoassays. The dominant follicle was maintained during the treatment period, and it ovulated after implant removal in control heifers. In BFF group, the dominant follicle either ovulated after implant removal (two of six heifers) or gradually regressed until day 10 in the post-implant period (other four of six heifers). In the LHRHa group, the dominant follicle regressed during or after the implant period in 5 of 6 heifers. The dominant follicle ovulated in 1 of 6 heifers. Growth rate of the dominant follicle, until it reached its maximum diameter, was lower in BFF group than the control group (0.4 ± 0.1 vs 0.7 ± 0.1 mm d−1; P &lt; 0.01). Both BFF and LHRHa groups showed high regression rates in those follicles that did regress (2.2 ± 0.1 (n = 4) and 1.9 ± 0.8 mm d−1 (n = 5) respectively; P &lt; 0.01), compared with no regression in the control group. The BFF injections failed to suppress serum FSH levels consistently in all the heifers treated. LHRHa-treated heifers showed a significant decline (P &lt; 0.01) in the mean serum LH concentration. In conclusion, deprivation of LH causes atresia of the dominant follicle. Key words: Follicular fluid, LHRH antagonist, follicular dynamics, gonadotropins, estradiol-17β, ultrasound, regression

Does melatonin act on dopaminergic pathways in the mediobasal hypothalamus to mediate effects of photoperiod on prolactin secretion in the ram?

Previous studies have shown that the chronic administration of melatonin in the mediobasal hypothalamus (MBH) using micro-implants in Soay rams housed under long days causes a sustained decrease in the secretion of prolactin as occurs in response to short days. The purpose of this study was to investigate whether hypothalamic dopaminergic (DA) systems acting through D2 receptors may be involved in this melatonin-induced effect. Groups of Soay rams living under long days were treated in the MBH with micro-implants containing bromocriptine (BROM, DA D2 receptor agonist), or sulpiride (SULP, DA D2 receptor antagonist), given alone or in combination with melatonin (MEL), to establish whether the DA drugs would mimic or negate the effects of melatonin. A control group (C) received empty micro-implants or no treatment. The micro-implants were bilateral and were left in place for 14 weeks; the trial continued for a total of 28 weeks (14-week implant period and 14-week post-implant period) while the animals remained under long days. The ability of the micro-implants to release BROM and SULP for 14 weeks was confirmed by incubating implants in vitro and testing for the presence of the compounds using a pituitary cell bioassay. MEL in the MBH induced a marked decrease in the blood plasma concentrations of prolactin during the implant period and an increase during the postimplant period (MEL vs. C, p < 0.001). BROM given alone induced a sustained decrease in the plasma concentrations of prolactin (less marked than MEL), while SULP caused an increase (BROM and SULP vs. C, p < 0.001); the effects were restricted to the implant period. BROM given in combination with MEL produced the same effect as MEL alone during both the implant and postimplant periods, while SULP given with MEL produced the same effect as MEL during the implant period, but impaired the increase in plasma concentrations of prolactin during the postimplant period (MEL + SULP vs. MEL, p < 0.001). There were changes in growth and moulting of the pelage correlated with the marked changes in the secretion of prolactin induced by MEL, but not related to the lesser effects of BROM and SULP. In conclusion, the long-term effects of the D2 agonist and antagonist are consistent with the inhibitory role of hypothalamic DA pathways in the homeostatic regulation of prolactin secretion. The inhibitory effect of the D2 agonist did not mimic that of MEL in the MBH, thus it is unlikely that the short day MEL signal operates primarily through a hypothalamic DA system to inhibit the secretion of prolactin. However, since the administration of the D2 antagonist in the MBH did influence the response to MEL, it is probable that DA pathways are involved in relaying the effects of MEL on the long-term cycle in the secretion of prolactin in the ram.

Aerodynamic assessment of the speech of adults undergoing multichannel cochlear implantation.

This investigation was designed to evaluate the aerodynamic characteristics of the speech of adult multichannel cochlear implant (Nucleus, 21-channel) recipients. Five adults with an acquired profound sensorineural hearing loss were tested before implantation, immediately following implantation, and 3, 6, 9, and 12 months after implantation. A commercially available computerized pressure-flow instrumentation system was employed to assess the respiratory, laryngeal, velopharyngeal, and oral articulatory subsystems of speech of the implantees. The results of the investigation indicated 1) a slight increase in airflow rate values for sustained vowel /a/phonation after implantation, 2) a slight increase in duration of sustained vowel phonation from the preimplant period to the last postimplant period, 3) an increase in laryngeal airway resistance after implantation that resulted from a larger increase in estimated transglottal pressure than in transglottal airflow, 4) maintenance of normal velopharyngeal closure in oral-nasal contrastive contexts, and 5) slight increases in oral orifice area for fricative syllable utterances following implantation. Individual strategies for coordinated control of the speech mechanism appear to be potent variables to consider when assessing speech production.

Optimal management of a ventricular assist system. Contribution of flow visualization studies.

The Novacor (Baxter Novacor, Oakland, CA) Left Ventricular Assist System (LVAS) incorporates a versatile microprocessor based controller that permits a variety of operating modes. These include internally triggered automatic synchronous counterpulsation, electrocardiogram triggered synchronous operation, and full to empty or fixed rate asynchronous operation. The aim of this pilot study was to determine the extent to which washing of the blood contacting surfaces of the pump may be optimized by suitable choice of operating mode. Visualization of flow fields adjacent to surfaces in confined areas requires small, neutrally buoyant tracer particles for feature extraction. A novel technique using fluorescent tracer particles (100 microns), an argon laser, and a low pass optical filter has been developed for this purpose. Particle motion was tracked from video images and calculations were made of velocity. Flow visualization was performed under conditions that simulated clinically observed hemodynamic conditions, typical of the immediate post-implant period. At a given LVAS output, fluid speed in the vicinity of the inflow valve tended to increase at higher LVAS beat rates (and consequently lower LVAS stroke volumes). This and future work may well be useful in selecting the optimum modes of LVAS operation as a function of the hemodynamic status of the patient.

The safety and efficacy of chronic ventricular pacing at 1.6 volts using a steroid eluting lead.

Steroid eluting leads may allow for lower chronic pacing thresholds and therefore lower pacing outputs. Twenty-two patients (15 presenting with syncope) were implanted with VVI or VVIR pacemakers and transvenous steroid eluting leads and followed for a mean of 20.6 months while being paced at 1.6 V and 0.6 msec. Mean acute voltage pacing thresholds were 0.40 V at 0.5 msec and chronic pulse width thresholds were 0.21 msec at 0.8 V. Pacemaker function was documented with one to three 24-hour Holter monitors, attached during the 2-6 week postimplant period, bimonthly transtelephonic monitoring, and monthly pacemaker clinic visits. No patient developed recurrent symptoms and consistent capture was verified in all patients on every 24-hour Holter recording and transtelephonic monitor. Chronic ventricular pacing at an output of 1.6 V at 0.6 msec is safe and effective when using a steroid eluting lead and potentially has implications for pacemaker longevity.

Differential effects of DOCA on renal and gastrointestinal handling of sodium and potassium in pigs.

Young, male pigs eating standard pig chow, ad libitum, received approximately 170 mEq Na and 290 mEq K per day. Electrolyte intake, urinary and fecal electrolyte output, and plasma electrolyte levels were determined daily in 12 deoxycorticosterone acetate (DOCA)-treated pigs and in 6 control pigs. Daily Na and K balances (dietary intake - urinary + fecal output) were calculated. DOCA caused a reduction in urinary Na output from 1.53 mEq/kg/day to 0.57 mEq/kg/day during the first 48 hr following implantation. Escape from the renal sodium retaining effect of DOCA was complete within 3 days, with urinary Na output returning to pre-DOCA levels. Fecal Na output decreased from 0.65 mEq/kg/day during the preimplant period to 0.13 mEq/kg/day during the postimplant period. No escape from GI Na retention occurred by Day 15. Plasma Na rose to significantly higher levels by Day 15. Sodium balance was significantly elevated in DOCA-treated pigs for that first 48 hr postimplant. Urinary K output decreased from 3.50 mEq/kg/day to 1.74 mEq/kg/day during the first 2 days, but returned toward preimplant levels by Day 4. Fecal K output was increased for the first week, and thereafter returned to preimplant levels. Plasma K fell from 3.9 to 2.9 mEq/liter by Day 15. Potassium balance fell slightly in both experimental and control animals. No significant differences in potassium balance were present between the two groups. The control pigs showed no significant changes in plasma electrolyte concentration or in electrolyte balance. It is concluded that DOCA has differential effects on renal and gastrointestinal handling of electrolytes and that DOCA may induce an intracellular shift of potassium in pigs.

Output programmability and reduction of secondary intervention after pacemaker implantation

Six hundred one new or initial pacemaker implants between Jan. 1, 1972, and Dec. 31, 1979, consisted of 289 output-programmable pulse generators and 312 fixed-output generators. Standard leads were used in all instances. Of the 289 output-programmable pulse generators, 4.5% (13) required revision for failure to capture the heart in the postimplant period; of the 312 fixed-output units. 9.6% (30) required revision (p = 0.015). In 41 patients the early threshold was above standard output (5 V. 10 mamp, 0.5 msec), and in six of them approximately 6 months were required to return to stable threshold levels below standard output. In the remainder, threshold rose above standard output and was managed by increased output of the output-programmable pulse generators, either briefly or permanently. We conclude that output programmability allows reduction in secondary intervention after implantation and that threshold evolution may occupy a period as long as 6 months.

Disulfiram implantation critically evaluated.

A previous paper (Malcolm and Madden, 1973) has described the use of disulfiram implantation as a method of treatment for some alcoholics. The results obtained were satisfactory, measured in terms of duration of abstinence and social improvements made in the post-implant period. However, it was suggested that the success of the implant might be due to psychological rather than pharmacological factors. In an effort to clarify the nature of any deterrent effect of the implant, further clinical and biochemical evidence has been collected.