单电极VDD心脏起搏治疗肥厚性梗阻型心肌病(附1例报告)

目的：用ＶＤＤ心脏起搏治疗１ 例肥厚性梗阻型心肌病（ＨＯＣＭ）,并观察其临床及血流动力学效果。　方法：常规方法植入ＶＤＤ型心脏起搏系统,设置房室起搏间期１２０ ｍ ｓ,心房感知０．１５ ｍ Ｖ,起搏前后进行左室流出道压力阶差等血液动力学对比观察。　结果：术后房室同步起搏率为１００％ ,左室流出道压力阶差从６．８ ｋＰａ（５１．４ｍ ｍ Ｈｇ）降至２．８１３ ｋＰａ（２１．１ ｍ ｍ Ｈｇ）,二尖瓣前移现象消失,临床症状明显改善,随访期间未再出现晕厥。　结论：ＶＤＤ起搏植入简便、房室同步功能稳定,对ＨＯＣＭ 患者不失为一种新的有效的治疗方法。     

VDD起搏器治疗肥厚性梗阻型心肌病临床初探

目的：探讨ＶＤＤ起搏器治疗肥厚性梗阻型心肌病的临床疗效及其血液动力学变化。方法：对６例肥厚梗阻型心肌病患者植入ＶＤＤ起搏器,并进行随访观察,观测其左室流出道压差及血流速度的变化情况。结果：随访期间所有患者的临床症状均有明显缓解。与术前相比,术后随访各期的左室流出道压差及血流速度均有显著降低（Ｐ＜０．００１,Ｐ＜０．０１）。结论：ＶＤＤ起搏器治疗肥厚性梗阻型心肌病临床效果显著,可明显改善血液动力学状况,是一种较理想的治疗方法。     

VDD起搏治疗幼儿完全性房室阻滞(附一例报告)

一例３．５岁的女性幼儿因室间隔缺损修补术致迟发性完全性房室阻滞（ＣＡＶＢ）而安置ＶＤＤ起搏器。经锁骨下静脉途径埋置单根心房感知、心室触发起搏电极，使之于右房内塑形并贴靠房壁；起搏器埋于同侧皮下胸大肌筋膜上囊袋内。术中测得起搏阈值０．１Ｖ、脉宽０．４ｍｓ、电极阻抗５２０Ω、Ａ波振幅１．５ｍＶ、Ｖ波振幅１０．６ｍＶ，Ａ波感知设定０．２５ｍＶ。术后房室同步起搏率１００％，临床症状改善。表明ＶＤＤ起搏器不仅埋置简便，而且具有房室同步、频率应答等生理性起搏特点，是治疗幼儿ＣＡＶＢ的理想起搏方式。     

Can Chest Roentgenogram Predict the Posture Dependent Changes of Atrial Sensing Performance in Patients with a VDD Pacemaker?

The VDD pacemaker is useful for sequential pacing with a single lead but carries a risk of sensing failure. This study was designed to evaluate the relationship between the relative position of atrial lead and atrial sensitivity in different postures in patients with VDD pacemakers. Atrial sensitivity determination and chest roentgenography was performed in the supine and standing position 3 months after implantation in 25 patients with VDD pacemakers. Measurements of cardiac longitudinal length (from the top of the aortic arch to the diaphragm) and distances from the floating electrode to the upper margin of the seventh thoracic vertebra (D-T7), to the top of the aortic arch (D-knob), to the lateral wall of right atrium (D-wall), and the D-knob/cardiac longitudinal length (D-Ratio) were performed. Atrial signal amplitude decreased with the standing compared to the supine position in eight patients (group I) and increased or did not change in the other 17 patients (group II). In group I, the change of the D-ratio was greater (0.073 vs 0.035, P < 0.01), and the change of the cardiac longitudinal length with standing position was greater (18.4 +/- 7.3 vs 12.1 +/- 8.8 mm, P < 0.05) than in group II. The change of atrial sensitivity was related to the change of the atrial electrode position with different postures. Decreased atrial-sensed amplitude was observed in patients who had a greater change in the cardiac longitudinal length while standing. Thus, a decrease in atrial sensitivity with standing may be predicted by the positional changes of the cardiac silhouette on roentgenography before the procedure.     

Atrial signal amplitude measurements in VDD systems according to body position

Single lead VDD pacing is an established therapy in patients with AV block. Body position may influence the amplitude of the atrial signal recorded through the floating atrial electrode. This study analyzed the degree of posture related variation in the signal amplitude of floating atrial electrodes in 63 patients (mean age 72 +/- 21 years) implanted with a VDD system. The average atrial amplitude in the supine position was 1.59 +/- 1.15 mV and decreased significantly in the sitting position (1.37 +/- 1.08, P < 0.014), right decubitus (1.33 +/- 0.83, P < 0.007), and the abdominal position (1.24 +/- 0.86, P < 0.001). The left side decubitus showed a nonsignificant increase in atrial amplitude (1.66 +/- 1.02, P < 0.64). Body position significantly affects P wave amplitude and may be the cause of intermittent atrial undersensing. P wave amplitude measurement in different body postures should be performed in cases where suspected atrial undersensing occurs.     

VDD pacing from the middle cardiac vein via a persistent left superior vena cava

We report a combination of unusual features demonstrating a permanent pacemaker implantation of a single-pass VDD lead by way of an anomalous persistent left superior vena cava in the middle cardiac vein. The ventricular stimulation resembled a right bundle branch block QRS morphology and was successfully synchronized by spontaneous atrial activity. This case illustrates an alternative approach of effective VDD pacing and sensing in patients with such a venous anomaly when other standard implantation sites fail.     

Sensing Through the Esophagus for Temporary Atrial Synchronous Ventricular VDD Pacing

The purpose of this study was to evaluate the effectiveness and safety of temporary VDD pacing using an esophageal electrode for sensing of the atrial electrogram. We studied 15 patients, 8 men and 7 women, aged 77 ± 2 years (mean ± SE, range 61–90), with severe atriovenfricular (AV) conduction disturbances. A 24-hour beat-to-beat ECG analysis was used to evaluate the effectiveness of the pacing system and special tests were performed to test the stability of pacing and sensing. The system performed satisfactorily in 12 of the 15 patients. The 24-hour Holter ECG monitoring revealed the following percentages of beats: 96.32 ± 0.5 VDD, 2.92 ± 0.6 VVI, and 0.14 ± 0.05 paced beats resulting from pseudosensing. All the latter were single, with no bigeminy or salvos. The results of the stability tests were as follows: the percentage of VDD beats was significantly lower than the 24-hour mean when the patient lay on his right side (92.8 ± 0.5, P < 0.001), during the swallowing of liquids (91.26 ± 0.4, P < 0.001) and soft foods (84.2 ± 1.4, P < 0.001), and during coughing (94.2 ± 0.6, P < 0.001). The percentage of VVI type beats increased in these four cases (6.7 ± 0,5, 7.2 ± 0.3, 13.2 ± 1.2 and 4.8 ± 0.4, respectively, P < 0.001 in each case). The percentage of ectopic beats due to pseudosensing did not change significantly during any of the tests. These results indicate that the method described is a safe and effective technique for temporary VDD pacing.     

Comparative Functional Effects of Chronic Ventricular Demand and Atrial Synchronous Ventricular Inhibited Pacing

We compared the effects of chronic ventricular inhibited (VVI) and atrial synchronous ventricular inhibited (VDD) pacing on functional capacity in 8 patients with complete atrioventricular heart block. Permanent VDD (Medtronic #2409, ASVIP) pacemakers were implanted in four men and four women (age range 27-76 years, mean 58.9 +/- 18.4 years), and randomly assigned to a three-month period of VDD or VVI pacing in this single blinded, crossover study. Functional capacity was assessed by questionnaire, graded treadmill exercise testing and radionuclide angiocardiography prior to pacemaker implant and following each pacing period. Following 3 months of pacing in each of VVI and VDD pacing modes, maximum heart rate (83.4 +/- 14 vs 134.9 +/- 16.4 beats/min, p less than 0.001) and double product (147.5 +/- 58.3 vs 218.9 +/- 52.7, p less than .001) were greater with VDD pacing. Although exercise duration on treadmill exercise testing (5.3 +/- 2.9 vs 6.9 +/- 3.1 minutes, p less than 0.1) was greater in the VDD mode, the difference was not significant. Similarly, there was no significant difference in functional capacity as measured by questionnaire scores (50.1 +/- 8.4 vs 46.9 +/- 8.9, p less than 0.1) or in left ventricular ejection fraction for the two pacing modes (.54 vs .55, p less than .5). Only one patient reported a subjective improvement with physiologic (VDD) pacing, whereas the remaining patients stated no preference. We conclude that VDD pacing offers improved maximal cardiac work during exercise compared to VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical Evaluation of a New Single Pass Lead VDD Pacing System

Twenty-five patients with second- to third-degree AV block and normal sinus function (16 males, mean age 60 ± 18; range 15–78 years) underwent implantation of WD pacemakers (THERA VDD, Medtronic, Inc.) with a single pass (SP) lead. Results: During implantation the mean amplitude of the atrial (A) signal was 3.9 ±1.4 mV (range 2.0–7.8 mV). Stable, acceptable A-signals during implantation were usually observed in the mid- or lower part of the right atrium. The lead tip electrical parameters were not compro mised in any patient in order to obtain an acceptable A-signal. To verify VDD device function, patients underwent pacing system analysis on the second day and again 1, 3, and 6 months after implantation. Acute and chronic electrical measurements in the ventricle were similar to those with regular steroid leads. During follow-up tests, stable atrial sensing (A ≥ 0.7mV) was found in all but one patient (in whom A was 0.25–0.5 mV and an intermittent loss of atriai sensing occurred). There was no difference between serial measurements of A-signal amplitudes on the second day or 1, 3, and 6 months after implantation: 1.9 ± 1.3 mV, 1.5 ± 0.6 mV, 1.3 ± 0.8 mV, and 1.5 ± 1.1 mV, respectively. The mean implantation time was 54.0 ± 17 minutes and the mean fluoroscopy time was 3.2 ±1.3 minutes. Conclusions: SP lead VDD pacing is reliable and easy to manage with dependable atriai sensing and ventricular pacing. The significant reduction in atriai postimplantation amplitude is related to the different techniques used for measuring acute and chronic atriai signals.     

VDD Pacing with a Previously Implanted Single Lead System

Three patients who had undergone implantation of a rate modulated, afrial sensitive RS4 pacemaker, with a single orthogonal lead underwent replacement of a depleted unit with a DDD pulse generator, reusing the original lead with an adapter that allowed conversion of the bipolar atrial electrode into unipolar configuration. The mean atrial electrogram amplitude was 1,8 mV and no significant atrial sensing defects were found during Holler monitoring. As the RS4 pulse generator is no longer available, continued VDD pacing is possible by replacing it with a DDD pulse generator using the previously implanted single lead system.