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In patients with atrial fibrillation (AF), cardiac resynchronization therapy (CRT) is challenging because the ventricular rate of conducted AF exceeds the biventricular pacing rate. In the current report, we present a patient who received a CRT device that was programmed to ventricular sense response (VSR) on with VVI 40 beats per minute to allow the AF to be paced as fusion beats. We found that the pacing configuration resulting in the narrowest QRS in this patient was VVI 40 with VSR biventricular fusion pacing during AF. VSR mode allows for CRT delivery without the need to artificially increase heart rate.

Background: Hemodynamic optimization of cardiac resynchronization therapy (CRT) can be achieved reproducibly and—with bulky, nonimplantable equipment—noninvasively. We explored whether a simple photoplethysmogram signal might be used instead. Method: Twenty patients (age 65 ± 12) with CRT underwent automatic atrioventricular (AV) delay optimization, using a multiple-transitions protocol, at two atrially paced heart rates: just above sinus rate (“slow ApVp,” 77 ± 11 beats per minute [bpm]) and 100 bpm (“fast ApVp”). We then retested to assess short-term reproducibility. Results: All 80 optimizations identified an optimum (correctly oriented parabola). At 100 bpm, the simple photoplethysmogram had wider scatter between repeat optimizations than did Finometer: standard deviation of difference (SDD) 22 ms versus 14 ms, respectively, P = 0.028. The simple photoplethysmogram improved in reproducibility when slope (instead of peak) of its signal was used for optimization, becoming as reproducible as Finometer (SDD 14 ms vs 14 ms, P = 0.50). At slow heart rate, reproducibility of simple photoplethysmogram-based optimization worsened from 14 to 22 ms (P = 0.028), and Finometer-based optimization from 14 to 26 ms (P = 0.005). Increasing the number of replicates averaged improved reproducibility. For example, SDD of simple photoplethysmogram optimization (using peak) fell from 62 ms with two replicates to 22 ms with eight replicates (P < 0.0001). At 100 bpm, the eight-replicate protocol takes ∼12 minutes. Conclusions : A 12-minute protocol of simple photoplethysmographic AV optimization can be processed fully automatically. Blinded test-retest reproducibility of the optimum AV is good and improves with more replicates. If benefits to some patients are not to be neutralized by harm to others, endpoint studies should first test check narrowness of “within-patient error bars.” (PACE 2012; 35:948–960)

Background: Implantable cardioverter-defibrillators (ICDs) represent the treatment of choice for primary and secondary prevention of sudden cardiac death but ICD therapy is also plagued by inappropriate shocks due to supraventricular tachyarrhythmias. Dual-chamber (DC) ICDs are considered to exhibit an enhanced discrimination performance in comparison to single-chamber (SC) ICDs, which results in reduction of inappropriate detections in a short- to mid-term follow-up. Comparative data on long-term follow-up and especially on inappropriate shocks are limited. Methods: The aim of the OPTION study is to assess whether an optimized treatment with DC ICDs improves patient outcome and decreases the rate of inappropriate shocks in comparison to SC ICDs. DC ICD therapy optimization is achieved by optimal customizing of antitachycardia therapy parameters, activation of discrimination algorithms, antitachycardia pacing in the slow ventricular tachycardia zone, and avoidance of right ventricular pacing with the SafeR algorithm mode. The OPTION study, a prospective, multicenter, randomized, single-blinded, parallel study, will randomize 450 patients on a 1:1 allocation to either an SC arm with backup pacing at VVI 40 beats per minute (bpm) or to the DC arm with SafeR pacing at 60 bpm. Patients will be followed for 27 months. Primary outcome measure is the time to first occurrence of inappropriate shock and a combined endpoint of cardiovascular morbidity and all-cause mortality. Conclusion: The study will evaluate the relative performance of DC in comparison to SC ICDs in terms of inappropriate shock reduction and patient outcome. (PACE 2010; 33:1141–1148)

BACKGROUND Rate responsive (RR) pacemakers are commonly implanted with nominal conservative factory-set responsiveness, which is usually accepted because established exercise protocols are time-consuming. We aimed for efficient assessment of RR pacemaker settings. METHODS We tested exercise heart rates in controls and paced patients using a brief exercise test that approximates real-life levels of exertion. The test used a nonmotorized treadmill: 30 seconds walking at patient-determined speed followed by 15 seconds brisk exertion. Subjects totaled 110: 26 with RR pacemakers; 22 with non-RR pacers; 27 "sick" nonpaced control patients; and 35 healthy controls. Heart rate (HR) was measured prior to exercise, after 30 seconds of casual walk, after 15 seconds of brisk walk, and 1 minute into recovery. Testing required

With the increasing recognition of the pacemaker syndrome and with the availability of newer methods of pacing therapy, the status of the atrioventricular (AV) conduction in patients with Sick Sinus Sydrome (SSS) becomes crucial in the choice of mode of pacing. At the Philippine Heart Center, from April 1983 to November 1986, the sinus and AV node function studies of 46 patients who, by electrophysiological studies had sinus node dysfunction (SND)-SN recovery time (SNRT) >1400 msec, were reviewed. These were arbitrarily classified according to duration of SNRT into: Group A—borderline SND, SNRT from 1,401 to 1,499 msec (n = 4); Group B—mild SND, SNRT from 1,500 to 2,499 msec fn = 25); Group G—moderate SND, SNRT from 2,500 to 3499 msec fn = 6); Group D— severe SND, SNRT of 3,500 m and above (n = 11). Out of the 46, 14 (30%) had concomittant AVN dysfunction (AVND)—antegrade block rate < 130 beats per minute (BPM). The percentage occurrence of AVND was noted as follows: Group A—25% (1/4); Group B—28% (7/25); Group G—50% (3/6); Group D—27% (3/11). Out of the 14 patients with concomittant AVND, 5(35%) had antegrade block rate < 100 BPM, 3 in Group R and 2 in Group D. The study shows that AVND occurs in only 30% of SSS patients. Its occurrence and severity has no bearing on the degree of SND. In these, antegrade block was at a rate higher than 100 BPM in the majority of patients. The data suggest that most of SSS patients may benefit from atrial demand pacemaker which therapeutically is of more advantage over the ventricular demand type inasmuch as AV synchrony is retained, thus pacemaker syndrome is prevented.

This study compares the performance of three detection algorithms for the recognition of atrial fibrillation in chronic pacing leads. Multiple serial recordings were obtained of wideband and filtered electrograms from chronic atrial and ventricular leads in dogs for a period up to 55 days following implantation. Each dog was recorded in sinus rhythm and induced atrial fibrillation. Four days were chosen for processing: The day of implantation and a day in the first, second or third, and fifth weeks. Three signal processing methods were assessed for performance in detection of atrial fibrillation: software recognition of rate with automatic threshold control, amplitude distribution, and frequency spectral analysis. A software trigger for rate determination was adjusted to thresholds of 10, 20, and 30% of maximum baseline-to-peak amplitude. At 10%, a rate boundary anywhere between 420 and 560 beats per minute (bpm) perfectly separated atrial fibrillation from sinus rhythm even though atrial electrograms were contaminated with large QRS deflections and double-sensing was present. At 20% and 30%, a rate boundary around 300 bpm could be used, but sensitivity and specificity were reduced to 90%. In amplitude distribution analysis, a percent of time within a baseline window provided perfect separation of atrial fibrillation from sinus rhythm. In all cases, the signal was within this window less than 43% of the time in atrial fibrillation, and more than 43% in sinus rhythm. In spectral analysis, frequency bands were examined for power content. In the 6 to 30 Hz band atrial fibrillation contained the greater power. Choosing 58% of total power as a discriminant, sensitivity and specificity of atrial fibrillation detection were 100% and 95% respectively.

Seventy-four patients with unipolar QRS-inhibited pacemakers (VVI) were Holter monitored to assess the occurrence of pacemaker inhibition caused by skeletal muscle potentials during daily activities. Fifty patients had high-grade atrioventricular block and 24 had sinoatrial disease. Chest wall stimulation prior to monitoring revealed asystole of > 4 seconds duration in 22 patients, and ventricular rates between 25 and 56 beats per minute in 52 patients. Fifty-one patients (69%) had one or more episodes of pacemaker inhibition from myopotentials. Inhibition occurred in all types of pacemakers studies, but was most frequent and of longest duration in patients with Siemens-Elema 207/70 (13/14 patients), Cordis Omni-Stanicor (6/7 patients), CPI Microlith (5/6 patients), and Medtronic 5945 (8/10 patients). This was not unexpected considering the filter characteristics of the pacemakers. Nine patients (12%) presented symptoms which might be ascribed to pacemaker inhibition. The longest asystole observed was 3.2 s. Seven patients had pacemakers spikes falling on or near T-waves of spontaneous heart beats because their pacemakers had been rendered refractory by myopotentials. No serious arrhythmias were seen during episodes of pacemaker inhibition or interference. More emphasis should be put on the improvement of filter characteristics of unipolar VVI-pacemakers. Pacemaker patients with symptoms of myopotential inhibition should be equipped with either a bipolar or ventricular triggered (VVT) pacemaker or with a sensitivity and/or pacing mode programmable pacemaker.