The Effects of Cardiac Pacing on Central Hemodynamics in Experimental Propoxyphene-Induced Cardiac Failure

Coronary sinus pacing was evaluated in 10 pigs during propoxyphene-induced cardiac failure. From baseline, propoxyphene chloride 15 mg . min-1 was infused until circulatory shock developed. Cardiac pacing was evaluated at different dose levels expressed as % of the shock dose of propoxyphene: at intoxication levels below 50% of the shock dose, cardiac pacing improved cardiac performance. At dose levels above 50% of the shock dose cardiac performance deteriorated further during pacing. The results are consistent with a severe negative inotropic effect of propoxyphene in overdose.     

非心脏手术前安装心脏临时起搏器指征的探讨

目的探讨非心脏手术前安装心脏临时起搏器的指征。方法对102例合并缓慢性心律失常的外科患者术前植入临时起搏器,根据术中和术后心电图监测记录,将患者分为起搏组和备用起搏组,对比分析2组的临床特点。结果围手术期37例出现起搏心律(起搏组),65例为自主心律(备用起搏组)。与备用起搏组比较,起搏组患者年龄偏大[(61±17)岁vs(52±14)岁,t=2.885,P=0.005],具有器质性心脏病[心肌梗死:54%(20/37)vs14%(9/65),χ2=18.733,P=0.000;心肌病:8%(3/37)vs0%(0/65),P=0.045]和晕厥病史的患者[11%(4/37)vs0%(0/65),P=0.030]相对较多,24小时动态心电图(Holter)[97%(36/37)vs48%(31/65),χ2=25.741,P=0.000]和超声心动图(UCG)[97%(36/37)vs45%(29/65),χ2=26.076,P=0.000]检查结果异常的比例较高,差异具有显著性。结论手术前植入临时起搏器需全面评价患者的临床情况,Holter发现缓慢性心律失常,同时UCG显示心肌病变的高龄患者,特别是合并晕厥...     

The Status of Pacemaker Implantations in Japan

Abstract: It has been over 40 years since the initial clinical application of a cardiac pacemaker. Currently, approximately 300 per million patients in the United States and Europe are kept alive owing to the benefit of implantable pacemakers. Recently, the Japanese Cardiac Pacing Society and the Japanese Society of Artificial Organs performed pacemaker registry studies for 1989 and 1990. In this paper, results of this survey are described. Currently, implantable cardiac pacemakers are utilized only on the level of 120 per million patients in Japan. Surprisingly, all implantations were performed using foreign manufactured pacemakers. Despite the high level of electronic technologies available in Japan, no Japanese-made implantable cardiac pacemakers are utilized in Japan. One could speculate that a major reason for the low level of clinical application of cardiac pacemakers is that these devices are quite expensive because of the import duties imposed on them. It is necessary and strongly recommended that implantable cardiac pacemakers be manufactured in Japan in order for them to be utilized as fully as they are in the United States and Europe.     

Glued Carbon Fiber Electrodes for Diaphragm Pacing

Carbon fibers with fibrin glue were used as electrodes for diaphragm pacing. The electrodes were applied to three mongrel dogs and the effectiveness was tested. The carbon leads were glued to phrenic nerves by means of the fibrinogen and thrombin bilaterally. The tidal volumes and threshold current level for stimulation were measured at various time up to 9 weeks after implantation. Effective contraction of diaphragm were observed for 9 weeks. By using this electrode, the exfoliation of the nerve is not necessary, the nerve can be maintained in an intact state, and the risk of the implanting operation can be minimized.     

Permanent Cardiac Pacing after Cardiac Operations

Abstract: From January 1980 through December 1990, implantation of a permanent pacemaker was performed in 34 patients following open heart surgery. The patients were divided into two groups according to the clinical indications for implantation of permanent pacemakers. Group I (9 patients) had surgical atrioventricular block, and Group 2 (25 patients) had sick sinus syndrome. Tricuspid valve surgery was involved in 67% of Group 1 and 64% of Group 2. Adams-Stokes syncopal attack was the prime indication for permanent pacing in 100% of Group 1 and in 72% of Group 2. There were 2 operative deaths in Group 1, and no deaths in Group 2 (22% in Group 1 vs. 0% in Group 2, p < 0.005). Causes of the deaths were not related to the pacemaker implantation but to congestive heart failure following surgery. Among 32 survivors, there were 2 late deaths in Group 1, and 4 deaths in Group 2 (25% in Group 1 vs. 16% in Group 2, p < 0.05). The overall actuarial survival rate at 10 years was 82.1 ± 2.8%. However, the actuarial survival rate of patients in Group 1 is 70.2 ± 4.1%, which is statistically less than 85.4 ± 2.2% in Group 2 (p < 0.01). As judged by these results, patients in Group I should be followed on a regular out-patient basis even if they are asymptomatic and there is no evidence of pacemaker failure.     

Pacemaker dependent patients with device infection—a modified approach

A modified surgical concept for temporary cardiac pacing in pacemaker dependent patients requiring total removal of infected devices is presented. Proximal to the infected pocket a permanent bipolar pacing lead is placed transcutaneously into the ipsilateral subclavian or jugular vein. The lead is placed in the right ventricle and fixed into the skin using the suture sleeve. Pacing is established by connecting an external pacing generator. Subsequently the infected device can be removed completely. After wound dressing the externalized lead is connected to a permanent VVI-pacemaker allowing for prolonged temporary pacing.     

Characteristics of Chronically Paced Cardiac Functions in the Congenital Complete Atrioventricular Block

Characteristics of morphology, cardiac function, and cardiac reserve at late state were evaluated at rest, by changing the pacing rates, and after exercise in patients with ventricular pacemakers for isolated congenital complete atrioventricular block. Heart size was reduced statistically after pacemaker implantation, and concentric myocardial hypertrophy was observed. Cardiac pump functions at rest seemed fairly well compensated by increased ejection fraction, but the cardiac index was still lower than that of the normal heart. Responses of cardiac function towards the changing rates were considered satisfactory, and those variables had statistic correlations with the pacing rates. After exercise, significant increase of cardiac pump function and also statistic acceleration of myocardial function were observed. This fact proved that cardiac reserve was good, although the increased cardiac output after exercise was still insufficient without an increase in heart rate. More physiological pacing modes would be required as currently recommended.     

Long-term Effects of Gastric Pacing to Reduce Feed Intake in Swine

Background: The purpose of this study was to show the effect of chronic antral gastric electrical stimulation on the feeding behaviour of swine. Methods: Three groups of swine were investigated; first group control-group, second group - 8 months of electrical antral stimulation (10 Volts; 450 micros; Hertz 100; Mode: Cycling; on time 3.25 s; off time 5.15 s), the third group - 3 months of stimulation with modification of the following parameters - amplitude 8 Volts, hertz 5. All animals were nourished with commercial balanced dry feed ad libitum. Results: Group one demonstrated continued increased weight gain. After 90 days of stimulation, group two noted a net decrease of feed intake from 12% to 16%, followed by a net cyclical weight loss 30 days later (2 weeks of weight gain followed by 1 week of weight loss). The percentage difference between group one and two in increasing weight was-12 to 29% respectively. The feed output of the stimulated group (group two) was 12.8 less compared with control. The net weight loss was of 19 to 29.6 kg compared with control. Finally, group three was used to test a lower stimulation rate, resulting in a shorter rest during feeding and a 7% increase in consumption compared with control. Conclusions: Long-term antral gastric pacing influences the alimentary behaviour of swine. We attempt to extrapolate this influence in humans for possible attendant applications in patients with consumption dysfunction (e.g. bulimia and/or anorexia).     

Single Lead Atrial Synchronous Ventricular Pacing in Japanese Patients with Complete Atrioventricular Block

Abstract: The purpose of this study was to review our experience with atrial synchronous ventricular pacing devices (THERA VDD pacing systems, Medtronic, Inc., U.S.A.) using single atrioventricular leads in Japanese patients with complete atrioventricular block and normal sinus function. Twenty patients with a mean age of 55 ± 13 years underwent implantation of VDD pacemakers. At implantation the amplitude of atrial signals in the supine position during normal breathing, which was measured directly using an external pacing system analyzer, ranged from 1.8 to 5.8 mV with a mean amplitude of 3.4 ± 1.4 mV. Atrial amplitudes did not change during deep breathing (3.3 ± 1.1 mV) or in the semi-Fowler position (3.4 ± 1.6 mV). Atrial oversensing or undersensing was not observed in any of the patients. During a follow-up period, the percentage of atrial synchronization was >95% in 19 patients, and none of the patients had pacemaker related tachycardia or pacemaker related complications. These results were promising enough to warrant the extension of the clinical use of the VDD pacemaker.     

Bipolar Leads for Use With Permanently Implantable Cardiac Pacing Systems: A Review of Limitations of Traditional and Coaxial Configurations and the Development and Testing of New Conductor,Insulation, and Electrode Designs

The unacceptable rate of mechanical failures, threshold problems, and recalls experienced with many coaxial bipolar cardiac pacing lead designs are reviewed in detail. To address these problems, redundant insulation coradial atrial and ventricular tined leads (AL and VL, respectively) with iridium oxide electrodes were developed and subjected to extensive accelerated testing. There were no mechanical failures. The new lead body design proved to be much more durable than widely used trifilar MP35N configurations. The data reviewed and early and current test results are strongly supportive of tightly coupled insulation being a major factor in improving lead durability as long as the insulating material is not stressed. In addition to improving flex life, insulation adherence to the conductor may reduce the potential for ionic degradation. Pacing and sensing thresholds in animal studies of the new leads were within the reported range for leads with steroid eluting electrodes. A multicenter Canadian clinical trial was initiated with the first implant in early January 1994. By November 1995, 110 VL and 82 AL had been placed in 124 patients and followed for a mean of 11 ± 6 months; maximum 21, total 1355. There were 60 males and 64 females with a mean age of 64 ± 16 years, range 15-88. Primary indications for pacing were AV block in 61 patients, sick sinus syndrome in 53, vasovagal syncope in 4, and congestive heart failure in 7. Many patients had associated or primary tachyarrhythmias, including 111 with supraventricular and 12 with ventricular. Forty-two percent of patients (52/124) had prior cardiac procedures, including 18 open heart surgeries and 20 AV nodal ablations. At implant, 8 lead characteristics were rated good or excellent in 90% (746/829) of evaluations. X-ray visibility was of concern in 10% of patients (12/124). Three perioperative complications occurred, including displacement of one AL (1.2%) and one VL (0.9%). There were no subsequent mechanical (connector, conductor, or insulation) or functional (exit block, micro or macro displacement, or over- or undersensing) problems. Implant pacing thresholds (PT) at 0.45 ms were AL, 0.6 ± 0.2 (74) and VL 0.4 ± 0.2 V; impedance (Z) at 3.5 V output AL 373 ± 77 (82) and VL 497 ± 117 Ω. Sensing thresholds (ST) were AL 3.1 ± 1.6 (74) and VL 10.3 ± 4.9 mV. Ventricular lead data were obtained for all patients (N = 110). Atrial lead data are incomplete, because some patients were in atrial fibrillation during implantation. After 12 months, AL PT at 1.5 V output was 0.18 ± 0.10 ms (21) and at 2.5 V was 0.10 ± 0.05 (22). Associated AL ST was 3.3 t 0.9 mV (21) and AL Z 500 ± 65 Ω (25). After 18 months VL PT at 1.5 V was 0.15 ± 0.10 ms (9) and at 2.5 V output was 0.09 ± 0.04 ms (9). Associated VL ST was >7.5 ± 2.4 mV (9) and VL Z 497 ± 105 R (9). Follow-up time discrepancy is due to the VL being available 6 months earlier than the AL. There were no 30-day deaths and only one late death at 10 months in a patient with chronic atrial fibrillation. Death was unrelated to pacer or lead function. At 1 year, 68% AL (15/22) and 62% VL (24/39) captured at 0.5 V and ≤1 ms pulse width output. Innovative adherent insulation coradial bipolar lead conductors of the design studied combined with coated iridium oxide electrodes provide for a negligible incidence of mechanical or functional failure with clinical follow-up now approaching 3 years. Excellent acute and chronic sensing and pacing thresholds have been documented. Late thresholds have continued to improve gradually. Long-term clinical pacing at ≤1.5 V output with a large safety margin is feasible in essentially all patients. This coradial design produces very flexible <5 French bipolar redundantly insulated lead bodies allowing both AL and VL to simultaneously pass through a single 10 French introducer sheath. The coradial design reduces potential insulation, subclavian crush, and implant and late threshold problems versus coaxial approaches. Because the leads are so slender with reduced metallic content, some method of increasing radiopacity would help when using older fluoroscopes that are standard in many Canadian centers.     

儿童心瓣膜病的外科治疗

目的 报告儿童心瓣膜手术的经验。方法 ８７儿童心瓣膜病变患者,男５８例,女２９例,年龄４～１４岁,平均年龄１０．２岁。其中二尖瓣置换术３６例,主动脉置换术１３例,二尖瓣和主动脉瓣双瓣膜置换术６例,主动脉瓣成形术１３例,二尖瓣成形术１９例,所用心瓣膜均为机械瓣。同期处理三尖瓣关闭不全４１全,室间隔缺损２３例,房间隔缺损９例,佛氏窦瘤破裂８例,动脉导管未闭３例。结果 术后早期并发症包括：低心排血量综合     

Cardiac myxomas: 24 years of experience in 49 patients

Objectives: In this single-center study we reviewed our experience with a significant number of cardiac myxoma cases occurring over the past two decades. Patients and methods: Cardiac myxomas represented 86% of all surgically treated cardiac tumors at our center. Specifically, there were 49 consecutive patients, each with at least one myxoma. A detailed clinical, immunological, and echocardiographic long-term examination of 37 patients revealed one recurrent myxoma. Results: Most myxomas originated from the left atrium (87.7%), but also much less frequently from the mitral valve (6.1%), from the right atrium (4.1%), and from the left and right atria (2.0%). The myxomas produced a prolapse into the left ventricle in 40.8% of the patients, mitral stenosis in 10.2%, and threatened left ventricular outflow tract obstruction in 2.0%. Multiple myxomas were found in 20.4% of the patients. Cardiac signs appeared in 93.9% of the patients. Preoperative embolic events had occurred in 26.5%. Immunologic alterations were present in 87.5%. For resection, a bilateral atriotomy was used. An additional aortotomy was needed to expose one mitral valve myxoma. Postoperatively, 81.1% of the patients remained without cardiac symptoms. The early mortality rate was 2.0% and the late mortality rate was 6.1%. Long-term prognosis was excellent with an actuarial survival rate of 0.74. Specific immunologic alterations were found in 71.4% of the patients. The actuarial freedom from reoperation of the myxoma was 0.96. The rate of reoperations was low with 2.0% after 24 years. Conclusions: Myxomas were usually detected and operated on in symptomatic patients. A high index of suspicion seems important for early diagnosis. Immunologic findings may play an additional role in confirming the diagnosis and the recurrence of a myxoma. Immediate surgical treatment was indicated because of the high risk of embolization or of sudden cardiac death. Also, a familial genesis must be excluded in myxoma patients.     

Cardiac Pacing Following Surgery for Acquired Heart Disease

Abstract Background: This study is comprised of 3493 consecutive patients who underwent open heart surgery at our institution. Data on all patients were collected prospectively. Methods: In 45 patients (Group P) (1.3%), a permanent pacemaker (PP) was inserted postoperatively. For the purpose of the study, these patients were compared to 3448 patients (Group NP) who did not require insertion of a PP after surgery. Mean follow-up was 33 months (range 1.5 to 66). Results: We found Group P patients were older (64.8 ± 11.0 vs 61.0 ± 11.0 years, p < 0.05), had a higher proportion of elderly (> 70 years) (36% vs 19%, p = 0.01), and of female patients (48.8% vs 22.7%, p < 0.001) compared to Group NP. Group P also had a higher incidence of preoperative rhythm abnormalities (26.6% vs 5.7%, p < 0.0001), redo surgery (13.3% vs 4.6%, p = 0.02), aortic valve surgery (48.8% vs 10.8%, p < 0.001), and tricuspid valve surgery (repair 3, replacement 1) (8.8% vs 0.5%, p < 0.001), in addition to a higher proportion of patients in whom cold (vs warm) blood cardioplegia was used (68.8% vs 52.3%, p = 0.03). Indication for postoperative PP was sick sinus syndrome (SSS) in nine patients; atrial fibrillation in eight patients; atrioventricular block (AVB) in 27 patients; and combined AVB/SSS in 1 patient. There were no operative deaths in Group P. Necessity for PP after heart surgery had a significant impact on resource utilization resulting in prolonged ventilation (3.1 ± 7.5 vs 1.4 ± 3.3 days, p < 0.01), intensive care unit (5.1 ± 10.2 vs 2.5 ± 4.0 days, p < 0.01), and postoperative hospital stay (18.0 ± 13.4 vs 8.1 ± 9.4 days, p < 0.01). Conclusions: By multivariate logistic regression (odds ratio and p value in parentheses), aortic valve surgery (8.23, p = 0.001), the absence of preoperative sinus rhythm (5.60, p = 0.001), postoperative myocardial infarction (3.46, p = 0.024), and female gender (2.52, p = 0.003), were found to be independent predictors for PP requirement post surgery.     

Increased Thiopental Sensitivity in Cardiac Patients

The average dose of thiopental necessary for induction was 3.4 mg/kg body weight in seven patients on long-term therapy with digoxin and a diuretic and 4.7 mg/kg body weight in seven matched control patients (P less than 0.05). The initial volumes of distribution (V1) did not differ significantly. The amounts of thiopental redistributed (removed from V1) during the induction were calculated as V1 X k12 X ct and V1 X k13 X ct, where k12 and k13 are the rate constants describing the drug transfer from V1 to V2 and V3 and ct the computer-calculated average thiopental concentration in V1 during the initial 40 s of the induction period. There was no evidence of a lower amount being removed during the induction in the cardiac patients. The intravascular drug concentration at the time of sleep was expressed as the average of the arterial and the venous sleep concentrations. In the cardiac patients the average of that value was 20.1 micrograms/ml and in the control patients 30.2 micrograms/ml (P less than 0.05). It is concluded that the lower dose requirement in the cardiac patients was caused at least in part by a higher cerebral sensitivity to the drug.     

62例小儿心脏瓣膜置换术

目的总结１９７５～１９９７年间６２例１４岁以下儿童人工心脏瓣膜置换术的经验,探讨儿童瓣膜置换的手术适应证、瓣膜选择和术后抗凝等问题。方法全组低温体外循环下行心脏瓣膜置换术,１７例使用生物瓣,４５例使用机械瓣。结果住院死亡１２例,晚期死亡１３例,术后失访４例,长期存活３３例;随访时间２～２５７个月,其中心功能Ⅰ级２８例,Ⅱ级５例,无１例因生长发育出现人工瓣膜相对狭窄。结论儿童人工心脏瓣膜置换术的死亡率高,宜慎重掌握适应证;儿童心脏瓣膜置换宜选择机械瓣     

Effect of Intestinal Pacing on Small Bowel Transit and Nutrient Absorption in Healthy Volunteers

Background  Intestinal pacing (IP) has been previously shown to delay gastric emptying and reduce food intake in animals. The aims of this study were to investigate the effect and mechanism of IP on nutrient absorption in healthy volunteers. Methods  Twelve healthy volunteers (six men, six women) were involved in a two-session (one session without IP and one with IP) study. At the beginning of each session, a nasal-duodenal feeding tube, with two ring electrodes (used for IP) on the tip of the tube, was incubated into the duodenum under endoscopy. After a complete recovery from the incubation, the duodenum was infused via the feeding tube with 150 ml 30% intralipid + 25 g D-xylose within 30 min, and the stool was collected for 24 h for the analysis of fecal lipid during which a controlled meal was taken. Then 100 ml 1mCi⁹⁹Tc-labeled non-absorbable solution was infused within 3 min. The subject was asked to lie under a γ camera for at least 1 h for the measurement of small bowel transit. The movement of isotopes was monitored by γ camera at an interval of 10 s. The first appearance of isotopes in the cecum was considered as small intestinal transit time. The order of the two sessions was randomized and 1 week apart. In the IP session, intestinal pacing was performed via the pair of the ring electrodes for 2 h initiated at the beginning of infusion with a pacing frequency of 13 pulses/min, pulse width of 300 ms and amplitude of 5 mA. Results  (1) IP significantly reduced lipid and D-xylose absorption. The fecal lipid was 6.6 ± 4.6 g without IP and almost doubled with IP (11.1 ± 6.5 g, P = 0.047). Similarly, the D-xylose in urine was 3.46 ± 2.22 g with IP, which was significantly lower than that without IP (6.63 ± 5.06 g, p = 0.049). (2) IP accelerated intestinal transit. The transit time was 39 ± 17 min in the control session and reduced to 28 ± 10 min in the IP session (p < 0.03). (3) Diarrhea was reported in one subject without IP but in six subjects with IP (p < 0.05). Conclusions  The increased fecal lipid and induction of diarrhea with intestinal pacing suggest that intestinal pacing is capable of inducing malabsorption. This effect maybe contributed to the acceleration of intestinal transit.