Takashi Tokano

Clinical Significance of QRS Duration During Ventricular Pacing

To clarify the clinical significance of an abnormally prolonged paced QRS duration, we studied 114 patients who had undergone pacing for atrioventricular block (AVB). Patients were divided into two groups: group I consisted of 29 patients with at least one paced QRS duration ≥ 180 msec during the follow‐up period; group II consisted of 85 patients with paced QRS durations < 180 msec. The clinical background, QRS complexes before pacing, and the echocardiographic findings were assessed. Males (P < 0.05), those with H‐V block (P< 0.05) and a wider QRS complex of conducted and escape beats (both P < 0.01) were dominant in group I. The incidence of underlying heart disease was greater in group I than in group II (83% vs 32%, P < 0.01). Reduced left ventricular ejection fraction (LVEF) and increased left ventricular end‐diastolic dimension (LVDd) were more prominent in group I than in group II (LVEF 0.49 ± 0.17 vs 0.68 ± 0.10, P < 0.01, LVDd 57.1 ± 7.9 mm vs 48.5 ± 5.6 mm, P < 0.01). The paced QRS duration correlated with LVEF (r = ‐0.61) and LVDd (r = 0.81). A paced QRS duration ≥ 180 msec was sensitive and specific for a LVEF < 0.5 (83.3% and 85.2%) and LVDd ≥ 60 mm (100% and 81.4%). We conclude that patients with a prolonged paced QRS duration have more serious heart disease, and the paced QRS duration can be a useful indicator of impaired LV function.

Does an Early Increase in Heart Rate During Tilting Predict the Results of Passive Tilt Testing

Head‐up tilt testing is a useful but time‐consuming procedure. If we could accurately predict the tilt testing results; we would be able to substantially shorten the duration of tilt protocol. To clarify the hypothesis that an early increase in heart rate (HR) during tilting can predict the passive tilt results in our protocol (80‐degree angle for 30 minutes), we studied 115 consecutive patients (72 men, 43 women, mean age 46 ± 19 years) who were clinically diagnosed with neurally mediated syncope. Twentynine (25%) patients had a positive tilt test (P group), whereas 86 (75%) patients had a negative test (N group). The early HR increase was defined as the maximum HR during the first 5 minutes of tilting minus the resting HR before tilting. The early HR increase was significantly higher in the P group (23.8 ± 9.5 beats/min) than in the N group (17.5 ± 8.2 beats/min, P = 0.0008), but it was negatively correlated with the tilt duration to positive response (r =−0.52, P = 0.0032) and the patient age in the entire study population (r = 0.62, P < 0.0001). Results of multiple regression analysis indicated that age, tilt result, and tilt duration were independently associated with the early HR increase. As a result, an early HR increase ± 18 beats/min, the best apparent cut‐off point obtained in our study, was a sensitive (100%) marker for prediction of a positive response at ± 15 minutes of tilting, but it showed a low specificity (61 %). In conclusion, an early HR increase during 80‐degree tilting may be only predictive for a positive result ± 15 minutes because it depends on the tilt duration to a positive response and patient age.

Gender-related differences on signal-averaged electrocardiograms in healthy subjects

Abstract In conclusion, filtered QRS duration in time-domain analysis of SAEs was influenced by gender and body characteristics in healthy subjects; however, the parameters in spectral turbulence analysis were not.

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.

Rapid Improvement and Long-term Stability of Pacing Threshold with Active-fixation Screw-in Lead

Background: Active‐fixation screw‐in leads are associated with initially high thresholds. However, pacing thresholds have been shown to improve within several minutes after screwin. The aim of this study is to investigate the long‐term stability of rapidly improved pacing thresholds following the implantation of active‐fixation screw‐in leads.

A proposal of clinical ECG index “vagal score” for determining the mechanism of paroxysmal atrioventricular block

Paroxysmal atrioventricular block (P‐AVB) is a well‐known cause of syncope; however, its underlying mechanism is difficult to determine. This study aimed to evaluate a new ECG index, the “vagal score (VS),” to determine the mechanism of P‐AVB.

The use of serum bepridil concentration as a safe rhythm control strategy in patients with atrial tachyarrhythmias

The aim of this study was to evaluate the clinical significance of serum bepridil (Bep) concentration (SBC) for safely managing patients with atrial tachyarrhythmias (AT).

Dislodgment of an Atrial Screw‐In Pacing Lead 10 Years After Implantation

Dislodgment of an atrial screw‐in pacing lead is quite rare. This report describes a rare case of an atrial screw‐in lead dislodgment 10 years after implantation. Although it is an uncommon complication, very late dislodgment can occur postoperatively, and careful follow‐up is necessary. (PACE 2004; 27:264–265)

What is the optimal increase in resting heart rate with low dose isoproterenol infusion for tilt-induced vasovagal response?

Summary: Isoproterenol is widely used as a provocative medium for vasovagal responses during tilt testing. Dose of isoproterenol infusion is generally titrated empirically by increase in resting heart rate before tilt up. To determine the optimal increase in resting heart rate with isoproterenol for tilt‐induced vasovagal responses, we studied 97 consecutive patients with unexplained syncope. After the end of a negative baseline tilt (80° for 30 min), the isoproterenol tilt was performed using one of two protocols: two‐stage isoproterenol‐tilt protocol, with doses of 0.01 and 0.02 μg/kg per min for 10 min each, or one‐stage isoproterenol‐tilt protocol, with a dose of 1 or 2 μg/min for 10 min. The resting heart rate increase was defined as a percentage increase in the resting heart rate after isoproterenol infusion, compared to the baseline heart rate before the tilt test. In 117 tilt procedures, 28 (93%) of the 30 positive responses occurred with a resting heart rate increase of ≥21%. With the resting heart rate increase of 60 and 100%, 18 (60%) and 27 (90%) positive responses were observed, respectively. In conclusion, the minimum resting heart rate increase of ≥21% was required to provoke a vasovagal response during subsequent isoproterenol‐tilt (80° for 10 min). Preferably, heart rate should be increased to 60‐100% by isoproterenol titration before tilting.

Long-term reliability of sweet-tip type screw-in leads

Active fixation leads have provided stable atrial and ventricular pacing; however, long‐term follow‐up data have not been satisfactory. The purpose of this study was to investigate the long‐term reliability of active fixation leads and their electrical characteristic stability.