Johan Brandt

Long-term pacing in sinus node disease: Effects of stimulation mode on cardiovascular morbidity and mortality

In a previous retrospective treatment-comparison study of 168 patients with sinus node disease, we found a significantly higher incidence of permanent atrial fibrillation and congestive heart failure in patients treated with ventricular (VVI) pacing compared to atrial (AAI) pacing, after an average follow-up period of 2 years. To determine whether these differences persisted and whether AAI pacing resulted in a lower mortality rate than VVI pacing during long-term follow-up, the treatment groups were restudied after an average of 4 years of pacemaker treatment. The incidence of permanent atrial fibrillation was still significantly higher (p less than 0.0005) in the VVI group than in the AAI group after the additional 2 years (VVI = 47%, an increase from 29%; AAI = 6.7%, an increase from 3.4%). Congestive heart failure occurred significantly more often in the VVI group than in the AAI group (37% vs 15%, p less than 0.005). Analysis of survival data showed a higher overall mortality rate in the VVI group (23% vs 8%, p less than 0.05). The development of high-degree atrioventricular block in the AAI group remained low (total 4.5%). Thus, in sinus node disease, the advantages of AAI over VVI pacing persist during long-term follow-up. The differences in cardiovascular morbidity between the groups tend to increase with time and appear to result in a lower mortality rate among patients treated with AAI pacing.

Atrial versus ventricular pacing in sinus node disease: A treatment comparison study

Treatment with conventional ventricular pacing does not seem to influence the natural course in patients with sinus node disease (SND). In the present study the natural course of SND was compared in patients treated with ventricular (VVI) and those treated with atrial (AAI) pacing. The study population comprised 168 patients, 89 with atrial and 79 with ventricular pacing. The two groups were comparable with respect to clinical characteristics, degree of severity of SND, and length of follow-up period (average 2 years). Development of chronic atrial fibrillation and congestive heart failure was significantly more common in patients with ventricular than in those with atrial pacing (30% vs 4%, p less than 0.001; 23% vs 7%, p less than 0.01). Second-degree atrioventricular block developed in 4% of the atrially paced patients. Thus, atrial pacing is apparently superior to ventricular pacing in patients with SND.

Natural history of sinus node disease treated with atrial pacing in 213 patients: Implications for selection of stimulation mode

OBJECTIVES This study was designed to analyze the incidence and determinants of complications and long-term survival in sinus node disease treated with atrial pacing. BACKGROUND Knowledge of the natural history of sinus node disease treated with different pacing modes is imperfect, and controversy exists regarding the optimal pacemaker therapy. METHODS A consecutive series of 213 patients with sinus node disease initially treated with atrial pacing was studied for a median follow-up period of 60 months. The end points studied were permanent atrial fibrillation, high grade atrioventricular (AV) block, P wave undersensing, pacing mode change, reoperation and death. Several prognostic factors were evaluated statistically and the survival rate was compared with that of a matched general population. RESULTS The incidence rate of permanent atrial fibrillation during follow-up was 7% (1.4%/year). The risk of this arrhythmia increased substantially with age greater than or equal to 70 years at pacemaker implantation. Only 2 of the 15 patients who developed permanent atrial fibrillation required ventricular pacing. High grade AV block occurred in 8.5% (1.8%/year) and its incidence was much greater in patients with complete bundle branch block or bifascicular block (35%) than in patients without such conduction disturbances (6%). A change to ventricular or dual-chamber stimulation was necessary in 14% of all patients, primarily because of early lead dislodgment or high grade AV block. Surgical intervention with maintenance of atrial pacing was required in 7% of patients. The survival rates of 97% at 1 year, 89% at 5 years and 72% at 10 years did not differ significantly from those of a matched general population. CONCLUSIONS In sinus node disease, atrial pacing can be successfully applied during long-term follow-up. Patients with complete bundle branch or bifascicular block in addition to sinus node disease should initially receive a dual-chamber pacemaker, but routine application of dual-chamber stimulation does not appear to be warranted.

Gastrointestinal complications after cardiac surgery

Gastrointestinal complications after cardiac surgery are often difficult to diagnose, and are associated with high morbidity and mortality rates. The aim of this study was to determine risk factors for these complications.

Far-field QRS complex sensing: prevalence and timing with bipolar atrial leads.

Sensing of farfield QRS complexes through the atrial pacemaker lead may cause a number of pacemaker function disturbances, most of which are rarely seen with modern pulse generators. However, certain pulse generator algorithms will still be jeopardized by farfield QRS complex sensing. Intracardiac electrograms with markers were obtained by telemetry in 30 patients following implantation of a permanent bipolar atrial lead and a DDDR pulse generator. The occurrence and timing of farfield QRS complex sens‐ing was studied at different atrial amplifier sensitivity settings. With paced ventricular complexes, QRS sensing was documented in all 30 cases at the maximum atrial sensitivity (0.1 mV). The median QRS complex sensing threshold was 0.3 mV, and the sensing window at high atrial sensitivities was 67‐202 ms following the ventricular pacing impulse. In one case, QRS complex sensing was seen up to an atrial sensitivity of 1.5 mV. In 12 of 13 patients with 1:1 AV conduction, atrial sensing of spontaneously conducted ventricular complexes was seen (median sensing threshold 0.2 mV; the sensing window was–23 to 114 ms relative to the ventricular amplifier sensing event). Farfield QRS complex sensing was also found in all 12 patients in whom ventricular fusion complexes were obtained (median sensing threshold 0.2 mV; the window of sensing was 64‐187 ms after the ventricular pacing impulse). Constant or intermittent QBS complex sensing via the atrial bipolar lead was thus universally demonstrable. It occurred in only a mi nority (20%) of patients at a sensitivity of 0.5 mV or less. Knowledge regarding the timing of the over sensing as related to the atrial sensitivity setting may aid in the design of algorithms of future pacemak ers and cardioverter defibrillators.

Intra-operative defibrillation testing and clinical shock efficacy in patients with implantable cardioverter-defibrillators: the NORDIC ICD randomized clinical trial

Aims This trial was designed to test the hypothesis that shock efficacy during follow-up is not impaired in patients implanted without defibrillation (DF) testing during first implantable cardioverter-defibrillator (ICD) implantation. Methods and results Between February 2011 and July 2013, 1077 patients were randomly assigned (1 : 1) to first time ICD implantation with (n = 540) or without (n = 537) DF testing. The intra-operative DF testing was standardized across all participating centres, and all ICD shocks were programmed to 40 J irrespective of DF test results. The primary end point was the average first shock efficacy (FSE) for all true ventricular tachycardia and fibrillation (VT/VF) episodes during follow-up. The secondary end points included procedural data, serious adverse events, and mortality. During a median follow-up of 22.8 months, the model-based FSE was found to be non-inferior in patients with an ICD implanted without a DF test, with a difference in FSE of 3.0% in favour of the no DF test [confidence interval (CI) −3.0 to 9.0%, Pnon-inferiority <0.001 for the pre-defined non-inferiority margin of −10%). A total of 112 procedure-related serious adverse events occurred within 30 days in 94 patients (17.6%) tested compared with 89 events in 74 patients (13.9%) not tested (P = 0.095). Conclusion Defibrillation efficacy during follow-up is not inferior in patients with a 40 J ICD implanted without DF testing. Defibrillation testing during first time ICD implantation should no longer be recommended for routine left-sided ICD implantation.

Reduction of RV pacing by continuous optimization of the AV interval

Background: In patients requiring permanent pacing, preservation of intrinsic ventricular activation is preferred whenever possible. The Search AV+ (SAV+) algorithm in Medtronic EnPulse™ dual‐chamber pacemakers can increase atrioventricular (AV) intervals to 320 ms in patients with intact or intermittent AV conduction. This prospective, multicenter study compared the percentage of ventricular pacing with and without AV interval extension.

Far‐Field QRS Complex Sensing Via the Atrial Pacemaker Lead. II. Prevalence, Clinical Significance and Possibility of Intraoperative Prediction in DDD Pacing.

To study the prevalence and significance of far‐field QRS complex sensing via unipolar atrial electrodes, we attempted to provoke this phenomenon postoperatively in 119 patients with DDD pacemakers. It occurred in 42 patients (35%), with different types of atrial electrodes. In 27 cases with documented far‐field QRS complex sensing, selection of an adequate atrial amplifier sensitivity eliminated the problem; in the remaining 15 cases, other program adjustments were necessary. In all patients DDD pacing could be maintained, and no reoperations were required. In a retrospective analysis of a subgroup of 26 patients, all having received endocardial unipolar carbon tip electrodes in the right atrial appendage, the possibility of predicting subsequent far‐field QRS complex sensing was studied. The occurrence thereof was not significantly related to patient age or sex, indication for pacing, or routinely obtained electrophysiological measurements. Potential far‐field QRS complex sensing via the atrial electrode is significantly common in patients with DDD pacemakers. Patient characteristics and intraoperatively measured intraatrial signal amplitudes are not useful in predicting the postoperative occurrence of the phenomenon. As a rule, it can be handled effectively by pulse generator reprogramming.

Far-field QRS complex sensing via the atrial pacemaker lead. I. Mechanism, consequences, differential diagnosis and countermeasures in AAI and VDD/DDD pacing.

Unintended sensing of QRS complexes via atrial pacemaker leads may cause disorders of pacemaker function in AAI, VDD and DDD pacing. The consequences of this phenomenon depend upon the pacing mode and the timing of the inappropriate sensing as related to the technical characteristics of the pulse generator. With AAI pacemakers, “inappropriate pacemaker bradycardia” may be seen or P‐wave undersensing may be simulated. With VDD and DDD systems a special kind of pacemaker mediated tachycardia or apparent P‐wave undersensing may result. With knowledge of the underlying mechanisms, differential diagnosis is possible. The countermeasures available are discussed.

Percent ventricular pacing with managed ventricular pacing mode in standard pacemaker population

AIMS Unnecessary right ventricular pacing has deleterious effects and becomes more significant when cumulative percent ventricular pacing (Cum%VP) exceeds 40% of time. The Managed Ventricular Pacing (MVP) mode has been shown to significantly reduce the percent ventricular pacing compared to the DDD/R mode. This study assessed the percent of ventricular pacing in a standard pacemaker population programmed to MVP and for which patients it is possible to achieve a Cum%VP < or = 40%. METHODS AND RESULTS Unselected, consecutive patients were implanted with a dual chamber pacemaker with a mean follow-up period of 76 days. The Cum%VP was calculated from device diagnostics between pre-hospital discharge (PHD) and the 1-month post implant visit. The median Cum%VP of 107 patients (age 67.2 +/- 14 years; 53% male) who were programmed to MVP was 3.9%. The median Cum%VP was 1.4% in patients with sinus node disease (SND) and 28.8% in patients with AV block (AVB). Cum%VP < or = 40% was observed in 72% of all patients, in 50% of AVB patients, and in 86% of SND patients. CONCLUSION The MVP mode is capable of achieving a low percent of ventricular pacing in a standard pacemaker population with SND and AVB. In addition, 72% of patients in MVP mode demonstrated Cum%VP < or = 40%.