VVI与AAI起搏对病态窦房结综合征合并阵发性房性快速心律失常的影响

目的比较ＶＶＩ与ＡＡＩ起搏对病态窦房结综合征（病窦综合征）合并阵发性房性快速心律失常的远期影响。方法分别对４１和３８例病窦综合征合并阵发性房性心律失常的患者行ＶＶＩ和ＡＡＩ起搏,术后进行了临床、心电图、２４小时动态心电图的定期随访,随访时间分别为３９±２．６和２４±１．８个月。结果ＶＶＩ组２１例（５１．２％）发展成持续性心房颤动,２０例阵发性房性心律失常发作次数及持续时间较术前显著增加（Ｐ＜０．０５）,６例（１４．１％）出现血栓栓塞,无１例死亡,无电极移位等并发症。ＡＡＩ组,所有患者生活质量明显改善,１９例（５０％）阵发性心房颤动、心房扑动发作的频度及持续时间较术前显著减少（Ｐ＜０．０５）,无１例发展为持续性心房颤动、血栓栓塞和死亡,１例（３％）出现电极移位,１例（３％）出现一度房室阻滞。结论ＡＡＩ起搏是一种安全、可靠的起搏方式,对病窦综合征合并的阵发性房性心律失常有明显的抑制作用,显著优于ＶＶＩ。     

Clinical efficacy of permanent cardiac pacing in patients with bradysystolic forms of disturbances of cardiac rhythm and conduction

From 1996 to 2002 primary implantations of pacing systems because of bradysystolic disturbances of cardiac rhythm and conduction had been carried out in 311 patients. Indications were disturbances of atrioventricular conduction in 168 and sick sinus syndrome in 143 patients. According to type of permanent pacing patients were divided into 3 groups: with single-chamber ventricular on demand pacing (VVI, n=215), with single-chamber atrial pacing (AAI, n=39), and with dual-chamber pacing (DDD, n=57). As characteristics illustrating long term clinical results of permanent pacing we used development of the pacemaker syndrome; development of permanent atrial fibrillation; risk of thromboembolic complications and strokes; progression of heart failure; total, cardiovascular mortality and their structure; 7 year survival.     

Ventrikuläre Stimulationsvermeidung bei Patienten mit Sinusknotenerkrankung oder intermittierendem AV-Block

In patients with frequent right ventricular stimulation, worsening of heart failure and atrial fibrillation may occur. Avoidance of unnecessary right ventricular pacing is a major requirement for pacemaker selection and programming in patients with sinus node disease or intermittent AV block. In dual chamber pacemakers this goal can be achieved by programming a long AV delay or an AV delay hysteresis. Algorithms that allow AAI pacing in a dual chamber pacing mode and change to DDD mode in case of high degree AV block are a new attempt to avoid unnecessary right ventricular pacing. The article describes various strategies to avoid unnecessary ventricular pacing and discusses their advantages and disadvantages.     

Our experience using continuous atrial stimulation in sick sinus syndrome

Temporary atrial pacing (AAI) was applied in 31 patients with sick sinus syndrome (S.S.S.), including 20 with tachycardia-bradycardia syndrome (t.b.s.). In all patients before pacemaker implantation atrioventricular conduction was estimated using rapid left atrial, transoseophegeal stimulation assuming Wenckebach's point over 120 imp./min to be a physiological one. In all cases, but one ventricular electrodes were implanted and connected with multiprogrammable pacemakers (MP). Follow-up time ranged from 3 to 38 months (mean 18,4). Electrode dislodgment was not observed. In 9 persons sensing disorders were observed but thanks to programming the pacemaker sensitivity they could be resolved almost in all of them. Second degree Mobitz type I a-v block occurred in 3 patients during a long-term follow-up. In one of them changing the pacing mode to VVI was necessary. In persons with tachycardia-bradycardia syndrome cardiac pacing together with pharmacologic therapy allowed to almost eliminate tachycardia attacks. Authors positively estimated AAI pacing mode.     

Schrittmachertherapie bei Patienten mit Vorhofflimmern

Pacemaker therapy in patients with atrial fibrillation means the best current pacemaker therapy for patients with bradycardias with the aim to avoid the onset of atrial fibrillation and to establish DDD pacing despite of a history of atrial tachyarrhythmias. The newer application of pacing is the suppression of atrial arrhythmias in patients with medical refractory atrial tachyarrhythmias. Patients with slow ventricular rates and permanent atrial fibrillation should receive a VVI-pacemaker, if the bradycardias causes syncope, dizziness or a decrease of their exercise tolerance. In case of chronotropic incompetence the pacemaker should provide rate responsive pacing. Patients with sick sinus syndrome should receive an atrial (AAI) or dual-chamber (DDD) pacemaker, because patients with these in contrast to VVI-pacemakers develop less often atrial fibrillation and subsequent complications such as atrial thromboembolism. A dual-chamber or VDD-pacemaker—the latter connected to a VDD-single-lead—is indicated in patients with advanced AV-block. Atrial fibrillation occurs in 3 to 6% of the patients with no history of arrythmia and is, if pacemakers have no automatic mode switch, an often reason to program the devices to the VVI-pacing mode. Nowadays, most DDD(R)-pacemakers provide an automatic mode switch: During an atrial tachycardia the pacemaker switches to a VVI/VVIR mode and restores the initial DDD(R)-pacing mode with termination of the arrhythmia. In respect to the newer applications, one approach to prevent atrial tachyarrhythmias is permanent atrial pacing. As lower pacing rates of 80 to 90 ppm are usually needed and many patients hardly tolerate these pacing rates, new algorithms are under clinical investigation. Another approach is the simultaneous depolarization of the right and left atrium. Biatrial pacing is performed with one lead in the high right atrium and another lead in the coronary sinus. Another solution is bifocal atrial pacing with leads placed in the high right atrium and in the coronary sinus ostium. One effect of the new pacing techniques is to shorten interatrial conduction times. Therefore, biatrial pacing has become a therapy to prevent atrial arrhythmias deriving from delayed interatrial conduction times. As atrial reentry circuits seem to be important in atrial fibrillation, multisite atrial pacing is also performed in patients with medical refractory paroxysmal atrial fibrillation. Preliminary results suggest a more effective prevention of atrial fibrillation; nevertheless, these techniques should be still restricted to patients enrolled in clinical studies.     

Vorhofflimmern: Stimulation und Schrittmachertherapie

Pacing therapy is well established in all cases of symptomatic bradyarrhythmic atrial fibrillation. In paroxysmal or persistent atrial fibrillation, the implanted dual chamber pacemaker device should incorporate an automatic mode switching algorithm. Mode switch in case of atrial fibrillation detection avoids pacemaker mediated rapid ventricular pacing during an atrial tachyarrhythmia and allows to perform dual chamber pacing during phases of sinus rhythm which is the preferable mode due to improved hemodynamics, rate adaptation, lower progress in atrial fibrillation burden and a lower rate of thromboembolic events as compared to ventricular pacing. PERSPECTIVE: The possibility to prevent from atrial fibrillation recurrencies by pacing is currently under investigation. Various methodological approaches, for example multisite or alternate single site pacing, preventive pacing algorithms or hybrid- and even triple-therapy concepts are used for that purpose. Due to the theoretical point of view, that all these pacing interventions may reduce atrial fibrillation but also have the potential to act in a proarrhythmic manner, the data from adequately designed trials is of major importance: Septal pacing and preventive pacing algorithms seem to have a beneficial effect in a limited number of so far available studies. CONCLUSION: In clinical practice, preventive pacing and/or placement of the atrial lead in a septal position should therefore be available in those patients with a conventional pacing indication in addition to symptomatic recurrent atrial fibrillation. Preventive pacing is so far with a significant and not-predictable amount of non-responders no "early" stage of therapy in patients with recurrent symptomatic atrial fibrillation and no additional conventional pacing indication.     

Realisierbarkeit und Sicherheit einer alleinigen AAI(R)-Schrittmacherbehandlung beim isolierten symptomatischen Sinusknotensyndrom

Recent investigations prove that AAI(R) pacing is the "ideal" stimulation mode in isolated sick sinus syndrome. Nevertheless, in Germany this bradycardia is treated by AAI(R) pacemakers in less than 4% of cases compared to 25% in other countries. In our institution treatment of patients with isolated sick sinus syndrome is uniform and corresponds to the actual guidelines since the early 1990s; therefore the aim of our study was to analyze feasibility and safety of AAI(R) pacing in a retrospective study.Between 1998 and 2000, 52 of 165 patients (31.5%) with isolated sick sinus syndrome were treated by an AAI(R) pacemaker. The median follow-up duration was 51.5 months (minimal: 36 months). 6 patients died, in all cases unrelated to the stimulation mode. Three patients required reoperations, however, in only one case due to second degree AV block with the need for upgrading to DDD stimulation. Thus, the yearly incidence of this specific complication in the AAI(R) cohort is 0.64%.In conclusion, permanent atrial stimulation in isolated sick sinus syndrome is feasible in a quarter of all cases. It is safe if performed corresponding to actual guidelines. Additionally, single lead AAI(R) pacing is a cost-effective therapy and the only stimulation mode which, today, reliably prevents unnecessary right ventricular stimulation. If, on the other hand, algorithms providing automatic mode switching from AAI to DDD and vice versa are implemented reliably into all dual chamber pacemakers, single chamber atrial pacing will no longer be a subject for discussion.     

病窦综合征患者AAI和VVI起搏的远期随访分析

分析并比较病窦综合征 (SSS)患者AAI和VVI起搏的远期效果。对 1 4 0例AAI起搏、4 3例VVI起搏的SSS患者进行定期随访并行临床、心电图和Holter检查。结果 :随访 5 2± 4 .3(6～ 1 4 4 )个月 ,AAI组发生间歇性文氏型房室阻滞 (AVB) 1例。VVI起搏组阵发性房性心律失常、持续性心房颤动、脑栓塞、心源性死亡的发生率明显较AAI组高(分别为 39.5 3%vs 5 .71 %、1 8.6 0 %vs 1 .4 3%、9.3%vs 0 .71 %、1 1 .6 3%vs 0 .71 % ,P均 <0 .0 1 )。快速房性心律失常的发生率VVI组明显增加 (39.5 3%vs 1 8.6 0 % ,P <0 .0 1 ) ,AAI组明显减少 (5 .71 %vs 1 8.5 7% ,P <0 .0 1 )。无 1例近期和远期电极脱位。结论 :AAI起搏时远期AVB和电极脱位发生率很低 ,并且快速性房性心律失常、脑栓塞、心源性死亡事件的发生率低于VVI起搏     

Atrial adaptive rate pacing in sick sinus syndrome: effects on exercise capacity and arrhythmias.

OBJECTIVE--To test the hypotheses that adaptive rate atrial (AAIR) pacing: significantly increases maximal exercise capacity, and results in significant suppression of supraventricular and ventricular arrhythmia compared with fixed rate atrial (AAI) pacing. DESIGN--Prospective, randomised, single blind, crossover study with maximal treadmill exercise testing and 24 hour ambulatory electrocardiographic monitoring in AAIR and AAI modes. SETTING--Regional pacing centre. PATIENTS--30 consecutive patients (mean SD age 65 (12) years) with sick sinus syndrome who required permanent pacing, without evidence of conduction disturbance on 12 lead electrocardiograms or 24 hour ambulatory electrocardiographic monitoring and without other cardiovascular or systemic disease. INTERVENTIONS--Activity sensing or minute ventilation driven systems (AAI/AAIR) were implanted alternately. RESULTS--The mean (SD) peak heart rate in AAI mode was 122(28)v 130(22) in AAIR mode (p < 0.02) for the whole group and 104(17) v 120(5) (p < 0.003) for the patients with chronotropic incompetence. Exercise time was 12.3 (4.1) minutes in AAI and 12.3 (3.8) minutes in AAIR mode (NS) in the chronotropically incompetent patients. There were no significant differences in the Borg scores at peak exercise in AAI v AAIR mode in either group. The frequency per hour of atrial and ventricular arrhythmias showed no significant differences between the two modes in either the group as a whole or in the subgroups with chronotropic incompetence. CONCLUSION--AAIR pacing confers little benefit in sick sinus syndrome compared with AAI pacing.     

心房按需起搏的临床应用

AAI起搏是治疗房室传导正常的病态窦房结综合征(SSS)的理想方法,它可保持正常的房室收缩顺序及防止VVI起搏时心房压力上升,对预防心房纤颤(Af)有一定作用。本组17例AAI起搏主要用于房室传导正常的SSS,其中4例合并间断发作的Af,1例合并阵发性室上性心动过速(PSVT)。在随诊观察1～15个月之间,Af未再发作,PSVT也得到控制。本组17例全都采用螺旋形主动电极。我们体会其优点为电极可固定在心房之任何部位,操作简单,不易移位,采用可程控多参数的SSI型起搏器,便于定期进行心房调搏,观察房室传导功能的变化及处理可能发生的感知障碍及输出阻滞。     

Arterial thromboembolism in patients with sick sinus syndrome: prediction from pacing mode, atrial fibrillation, and echocardiographic findings

OBJECTIVE: To evaluate whether thromboembolism in sick sinus syndrome can be predicted by pacing mode, atrial fibrillation, or echocardiographic findings. METHODS: Patients were randomised to single chamber atrial (n = 110) or ventricular (n = 115) pacing. They were divided into subgroups with and without brady-tachy syndrome at time of randomisation. The occurrence of atrial fibrillation and thromboembolism during follow up were investigated and compared with echocardiographic findings. RESULTS: The annual risk of thromboembolism was 5.8% in patients with brady-tachy syndrome randomised to ventricular pacing, 3.2% in patients without brady-tachy syndrome randomised to ventricular pacing, 3% in patients with brady-tachy syndrome randomised to atrial pacing, and 1.5% in patients without brady-tachy syndrome randomised to atrial pacing. In atrial paced patients without brady-tachy syndrome at randomisation and without atrial fibrillation during follow up, the annual risk of thromboembolism was 1.4%. Left atrial size measured by M mode echocardiography was of no value in predicting thromboembolism. CONCLUSIONS: Arterial thromboembolism in patients with sick sinus syndrome is very common and is associated primarily with brady-tachy syndrome at randomisation and with ventricular pacing. The risk of thromboembolism is small in atrial paced patients in whom atrial fibrillation has never been documented.     

In recurrent atrial fibrillation should a sinus rhythm always try to be maintained? How?]

This paper presents the therapeutic options for recurrent paroxysmal atrial fibrillation. In the majority of patients, sinus rhythm should be maintained in order to improve cardiac function and decrease the risk of systemic embolism. Therapeutic options include serial pharmacological agents (with repeated external cardioversion) or non-pharmacological therapy: catheter or surgical ablation and atrial pacing.     

AAI与DDD起搏对病窦综合征患者的影响

目的比较AAI与DDD起搏方式对有正常房室传导功能的病窦综合征患者预后的长期影响。方法104例因病窦综合征置入起搏器的患者,按不同起搏方式分为两组:AAI组36例,DDD组68例。术后随访内容包括起搏器程控,患者的症状、体征,心电图和/或动态心电图,超声心动图及心功能分级(NYHA)。主要终点为心房颤动(简称房颤)的发生率,次要终点为脑卒中的发生率,心功能分级及超声心动图检查指标。结果随访43.2±15.7(21～79)个月,①DDD组房颤发生率明显高于AAI组(20.6%vs5.6%,P<0.05),而脑卒中发生率无差异(7.4%vs2.8%,P>0.05);②左房内径、左室舒张末期内径和左室射血分数在AAI组置入前后无差异,而DDD组术后左房内径、左室舒张末期内径增大,左室射血分数下降(P均<0.05);③AAI组与DDD组比较,对心功能影响较小。结论对于房室传导功能正常的病窦综合征患者,与DDD起搏比较,AAI起搏房颤发生率较低,对心功能影响较小,更符合生理性。     

Tachycardia-bradycardia syndrome (so-called "sick sinus syndrome"). Pathology, mechanisms and treatment

The tachycardia-bradycardia syndrome consists of paroxysmal atrial fibrillation, flutter or tachycardia followed by sinoatrial block or sinus arrest resulting in Stokes-Adams attacks. Detailed histologie findings of the conduction system of 2 patients with this entity correlated well with the clinical observation of cardiac rhythm disturbances in the sinus node, atria and atrioventricular (A-V) junction. Eight other patients with the syndrome were studied clinically. The mechanisms (as revealed by the electrocardiogram) producing the bradycardia phase include depression of pacemaker function (arrest) or of conduction (exit block) of the sinus impulse, or both, plus depression of A-V junctional impulse formation. Proper therapy usually requires electrical pacing in conjunction with administration of digitalis or propranolol, or both. Our findings suggest that the term “sick sinus syndrome” is an inaccurate and inappropriate synonym for the tachycardia-bradycardia syndrome.     

Pacing therapy for atrial tachyarrhythmias

The use of pacing techniques for the treatment of atrial tachyarrhythmias has been advocated for more than 30 years. Although it has played a beneficial role in the management of paroxysmal supraventricular tachycardia (PSVT) in drug-refractory patients, tachycardia acceleration and development of atrial fibrillation has been the major drawback. With the availability of radiofrequency catheter ablation therapy, the use of implantable antitachycardia devices for PSVT is currently negligible. From retrospective and small control studies it has been shown that atrial or dual-chamber pacing in patients with sick sinus syndrome has been associated with a lower incidence of paroxysmal atrial flutter or fibrillation than in those who received a ventricular pacemaker. Furthermore, recent studies have reported the potential benefit of reducing frequency of paroxysmal atrial flutter and fibrillation with multisite atrial pacing. As a result, there is a resurgence of research interest in antitachycardia pacing for prevention of atrial tachyarrhythmias. This paper briefly describes the basic aspects of antitachycardia pacing, reviews the data on the use of implantable antitachycardia devices for PSVT and the selection of patients, and assesses the current status of research on atrial pacing for prevention of paroxysmal atrial flutter and fibrillation.     

Physiologic limitations of dual chamber stimulators during physical activity

Dual chamber DDD pacing is fully physiologic when chronotropic response of sinus node to exercise is normal and when retrograde ventriculo-atrial conduction is absent. Comparison of results from exercise test with increasing work load showed that atrial-triggered ventricular pacing provides a significant functional benefit (delta VO2 15%) P less than 0.01, if compared with fixed rate ventricular pacing. The benefit is closely related with the amount of sinus rate increase during exercise. In patients with sinus node syndrome the atrial triggered ventricular pacing rate did not show significant increase during exercise and exercise capability was similar to that observed with fixed ventricular pacing. Retrograde ventriculo-atrial conduction was observed in 56% of patients with sick sinus syndrome and 28% of patients with complete AV block and was the reason for endless loop tachycardias (ELTs). ELTs can be eliminated by lengthening atrial refractory period (ARP). In patients with ARP greater than or equal to 250 ms (47%), mild (8:7, 4:3) or important (2:1) AV block appeared during exercise test, with sudden drop of pacing rate and cardiac output at highest work load. Among other "physiologic" pacing modes, respiration traced ventricular stimulation showed high physiologic sensitivity (90%) and haemodynamic benefit comparable to that obtained during dual chamber pacing and without the related disadvantages.     

Atrial pacing in the management of sick sinus syndrome: Long-term observation for conduction disturbances and supraventricular tachyarrhythmias

Atrial pacing (AAI) in sick sinus syndrome (SSS) has been questionedbecause of the risk of distal conduction disturbances (DCD)and atrial tachyarrhythmias. The authors studied the incidenceof clinically relevant DCD and arrhythmias in 52 SSS patientswith AAI. The observation time was 25–67 (mean 48) months. Invasive electrophysiologic investigation was performed preoperativelyin 29 cases and preoperative atrial pacing to Wenckebach blockor to 150 ppm in 23. The preoperative investigation showed prolongedHV-time in three cases and Wenckebach block at 110ppm in onecase, while six patients had LAH-block, five RBB-block and twofirst degree A V-block. No further DCD developed in any of thesepatients. Second-degree type IA V-block developed in two patientsafter 2 and 19 months, respectively. One had been treated withdigitalis and verapamil and was asymptomatic. The other patient,who had a low ventricular rate, experienced near-syncope. Thesetwo blocks could not be predicted from the preoperative andperoperative investigations. In five patients (10%) permanent atrial fibrillation developedduring the follow-up period. The incidence of concomitant supraventriculartachyarrhythmias in the patients with the bradycardia-tachycardiasyndrome appeared to be unaffected by the pacemaker treatment.     

Cardiac arrhythmias and conduction disturbances in autoimmune rheumatic diseases

Rhythm and conduction disturbances and sudden cardiac death (SCD) are important manifestations of cardiac involvement in autoimmune rheumatic diseases (ARDs). In patients with rheumatoid arthritis (RA), a major cause of SCD is atherosclerotic coronary artery disease, leading to acute coronary syndrome and ventricular arrhythmias. In systemic lupus erythematosus (SLE), sinus tachycardia, atrial fibrillation and atrial ectopic beats are the major cardiac arrhythmias. In some cases, sinus tachycardia may be the only manifestation of cardiac involvement. The most frequent cardiac rhythm disturbances in systemic sclerosis (SSc) are premature ventricular contractions (PVCs), often appearing as monomorphic, single PVCs, or rarely as bigeminy, trigeminy or pairs. Transient atrial fibrillation, flutter or paroxysmal supraventricular tachycardia are also described in 20-30% of SSc patients. Non-sustained ventricular tachycardia was described in 7-13%, while SCD is reported in 5-21% of unselected patients with SSc. The conduction disorders are more frequent in ARD than the cardiac arrhythmias. In RA, infiltration of the atrioventricular (AV) node can cause right bundle branch block in 35% of patients. AV block is rare in RA, and is usually complete. In SLE small vessel vasculitis, the infiltration of the sinus or AV nodes, or active myocarditis can lead to first-degree AV block in 34-70% of patients. In contrast to RA, conduction abnormalities may regress when the underlying disease is controlled. In neonatal lupus, 3% of infants whose mothers are antibody positive develop complete heart block. Conduction disturbances in SSc are due to fibrosis of sinoatrial node, presenting as abnormal ECG, bundle and fascicular blocks and occur in 25-75% of patients.     

Incidence and risk indicators of thromboembolism during the acute phase of single chamber ventricular pacing

BACKGROUND: The incidence of thromboembolism may be higher in single chamber ventricular pacing than in physiological pacing. However, the incidence of thromboembolism during the acute phase of single chamber ventricular pacing (within 14 days) is not known. OBJECTIVES: The incidence and the risk indicators of thromboembolism were investigated during the acute phase of single chamber ventricular pacing. METHODS: Fifty-five consecutive patients (22 males, 33 females, mean age 67 +/- 9 years) who required VVI pacemakers due to brady-tachy sick sinus syndrome (42 patients) or brady atrial fibrillation (13 patients) in the period from April 1975 to December 2000 were retrospectively reviewed. The patients were divided into groups with thromboembolism and without thromboembolism, and the risk indicators for thromboembolism were analyzed. RESULTS: Seven patients (13%) suffered systemic thromboembolism. Three patients had thromboembolic events during temporary ventricular pacing, and four patients had thromboembolic events just after permanent VVI pacemaker implantation. The following risk indicators were identified in the patients with thromboembolism: hyperlipidemia, hypertension, organic heart disease (p < 0.05, respectively), and diabetes mellitus (p < 0.0005). CONCLUSIONS: Patients with brady-tachy sick sinus syndrome and brady atrial fibrillation have a significant risk of thromboembolism during the acute phase of single chamber ventricular pacing. Effective anticoagulation is needed in these patients.     

Permanent cardiac pacing and thromboembolic risk in elderly patients

In patients undergoing permanent cardiac pacing, the maintenance of atrial contractility is important to ensure adequate ventricular filling and to guarantee an optimal ventricular ejection capacity. The appropriate pacing mode, assuring a suitable mechanical atrioventricular coupling, prevents the onset of atrial fibrillation and contributes to reduction of the risk of subsequent systemic and pulmonary thromboembolic episodes. We examined 461 patients (266 males and 195 females, aged between 52 and 97 years, average age 76.5 +/- 18) paced for conduction disturbances of various degrees and etiology. Of them, 323 patients received ventricular demand pacemaker (VVI group, average age 77.9 years); 138 underwent dual chamber pacing (DCP group, average age 75.2 years), 117 of the latter received universal demand pacing (DDD) and 21 atrial synchronous ventricular demand pacing (VDD). The patients were subsequently divided into two age-groups: Group A (/= 75 years, 287 patients). According to pacing mode and successive development of stable atrial fibrillation (AF), we analysed the occurrence of systemic and/or pulmonary thromboembolic episodes and the incidence of fatal events. During our study, performed from January 1986 to August 1993, 70 embolic episodes were observed in the VVI group and six in the DCP group. Eighty-four patients with VVI units developed AF during follow-up, compared with only five patients in the DCP group. Our data indicate that VVI patients have a higher incidence of AF, embolic complications and cerebrovascular mortality, in comparison with the DCP group. VVI pacing should be avoided, especially in older patients, when atrial rhythmical activity is present.