Petar Stojanov

Evaluation of Asynchronous Left Ventricular Relaxation by Doppler Echocardiography During Ventricular Pacing with AV Synchrony (VDD): Comparison with Atrial Pacing (AAI)

The effect of right ventricular pacing on left ventricular relaxation was studied in 13 patients (age 62 ± 3 years), with the atrial sensing ventricular pacing mode (VDD). A control group of similar age (64 ± 4 years) consisted of 11 patients with atrial pacing (AAI). The timing of events was determined in both groups at similar R‐R intervals (921 ± 77 ms vs 967 ± 37 ms). The loading conditions as estimated by peak systolic wall stress (afterload) and end‐diastolic left ventricular dimensions (preload) were approximately the same in both groups. The ratio of late to early filling velocities were similar in both groups. Dominant changes were: increased preejection period (142 ± 13 ms vs 95 ± 15 ms); and higher velocities of isovolumic relaxation flow (60 ± 34 cm/s vs 25 ± 4 cm/s) in patients with ventricular pacing. The isovolumic relaxation time was longer in patients with VDD pacing (127 ± 14 ms vs 108 ± 12 ms). Anterior systolic interventricular septal motion (paradoxal motion) was recorded in nine patients with VDD pacing and in none of the patients with AAI pacing. Isovolumic relaxation flow was detected during atrial pacing in five (45%) patients and in 13 (100%) patients during atrial sensing ventricular pacing, indicating asynchronous left ventricular relaxation. This data shows that VDD pacing compared to atrial pacing resulted in an altered activation pattern of the left ventricle, associated with delayed onset, asynchronous contraction with interventricular septal motion abnormalities and prolonged asynchronous left ventricular relaxation with abnormal motion manifested by the presence of isovolumic relaxation flow.

Assessment of Long-Term Stability of Chronic Ventricular Pacing Thresholds in Steroid-Eluting Electrodes

Sixteen patients with Medtronic 4003 steroid‐eluting electrodes implanted in the ventricular position were followed over 5 years. In each patient a special type of Medtronic 2443 pacemaker was implanted to allow programming of output at 1.35 V. Chronic threshold values in these patients measured at an output of 1,35 V were stable over the first 18 months of follow‐up. Mean values were: 0.06 ± 0.03 msec at 6 months and 0.08 ± 0.02 msec at 18 months; these did not differ from each other significantly. However, during the period from 18 to 36 months postimplantation, a significant increase in mean pacing threshold was observed: 0.08 ± 0.02 msec at 18 months postimplantation versus 0.14 ± 0.05 msec at 36 months (P < 0.01), After 36 months, the chronic pacing threshold remained stable until the end of the 5‐year follow‐up period. Further long‐term study of chronic threshold behavior of steroid‐eluting electrodes measured at low amplitudes is warranted.

Absorbable Suture Technique: Solution to the Growth Problem in Pediatric Pacing with Endocardial Leads

Endocardial pacing system implantation has been performed in 15 children of mean age 37 months (ranging from 1 day to 89 months), Endocardial lead fixation was performed by means of slowly resorbable suture (Dexon) to allow spontaneous lead migration as the child grows. During a mean follow‐up period of 61 months (range 17–108 months), none of the patients needed reintervention for correcting the lead length to allow growth.

Prevalence of Venous Obstruction in Permanent Endovenous Pacing in Newborns and Infants: Follow‐Up Study

Objective: We examined the prevalence of venous obstruction in 12 newborns and infants with permanent endovenous ventricular pacing, clinically, and by ultrasonographic assessment of hemodynamics (spontaneity, phasicity, velocity, and turbulence of flow) and morphologic parameters (compressibility, wall thickness, and thrombus presence).

Target Lead—Low Threshold Electrode

Acute and chronic threshold measurements were compared for three different electrodes: the Medtronic * Target Tip model 4011, the Medtronic Ring Tip Model 6971 and the Siemens‐Elema ** Carbon Tip Model 412S. The results of this study show that acute thresholds are lower with the Target Tip lead as compared to the other two, This finding applies to chronic thresholds as well. The results of this study favor programming to lower output energies while maintaining adequate safety margins with this lead system.

Permanent Endovenous Pediatric Pacing: Absence of Lead Failure—20 Years Follow‐Up Study

Background: The aim of the study was to analyze endovenous pacing lead survival in pediatric population implanted by cephalic cut down, or by axillary vein puncture.

Association between stimulated QT interval and ventricular rhythm disturbances: influence of autonomic nervous system.

To examine the association between ventricular rhythm disturbances and changes in the pacemaker‐induced stimulated T interval (STIM‐T interval), we compared findings from monitoring of two patient groups. The first group consisted of 15 patients with QTX microprocessor pacemakers and the second group consisted of 198 patients with documented ventricular rhythm disturbances and coronary artery disease (CAD). In the first group, which was free of ventricular rhythm disturbances and manifest coronary artery disease, the STIM‐T interval was measured every 4 hours over a 36‐hour period at four pacemaker frequency settings (70, 80, 90, and 100) in order to observe the circadian variation of the STIM‐T interval as a function of changes in autonomic nervous system (ANS) tone. The second group was comprised of patients with CAD and over 30 VES/hrs (Lown grade classification 1–5), and taking no antiarrhythmic medication. These patients were followed using 24‐hour Holter monitoring over a minimum of 23 hours and with less than 5% artifact/recording. Information regarding mean hourly heart rate, total number of VES, VES pairs, VT runs, and ischemic episodes in this group was compared with changes in the STIM‐T interval in the first group. The STIM‐T interval was found to be shorter during the day and longer at night at all heart rate settings. The total frequency of VES, of VES pairs, VT runs, and ischemic episodes in the second group varies in a similar circadian fashion. The greatest total number of VES, of VES pairs, VT runs, and ischemic episodes was recorded in the waking hours, at the same time when the STIM‐T interval is the shortest, while this number was significantly lower during sleep, when the STIM‐T interval of the first group is the longest. This coincidence of circadian variation pattern between STIM‐T interval in group I, and ventricular arrhythmias and ischemic episodes in group II, suggests that alterations in ANS tone reflected in the STIM‐T interval may be an important factor in the occurrence of these untoward events.

Transvenous Permanent Pacing in a One‐Day‐Old Infant

The epicardial route is the generally accepted approach for pacemaker implantation in newborns and infants. Ahhough transvenous lead implantation is the method of choice in adnlts, it has usually been used only in larger children, initially when their weight exceeded 15 kg/ although smaller infants have been implanted. Decrease in pacemaker weight and size, along with reduction of lead diameter, has facilitated transvenons implantation in children weighing < 15 kg.̂ We report tranvenous implantation in a 1-day-old infant.

Low incidence of complications after cephalic vein cutdown for pacemaker lead implantation in children weighing less than 10 kilograms: A single-center experience with long-term follow-up

BACKGROUND Only a few studies on the cephalic vein cutdown technique for pacemaker lead implantation in children weighing ≤10 kg have been reported even though the procedure is widely accepted in adults. OBJECTIVE The purpose of this study was to prove that cephalic vein cutdown for pacemaker lead implantation is a reliable technique with a low incidence of complications in children weighing ≤10 kg. METHODS The study included 44 children weighing ≤10 kg with an endocardial pacemaker. Cephalic, subclavian, and axillary vein diameters were measured by ultrasound before implantation. The measured diameters were used to select either an endocardial or epicardial surgical technique. Regular 6-month follow-up visits included pacemaker interrogation and clinical and ultrasound examinations. RESULTS Two dual-chamber and 42 single-chamber pacemakers were implanted. Mean weight at implantation was 6.24 kg (range 2.25-10.40 kg), and mean age was 11.4 months (range 1 day-47 months). In 40 children (90.1%), the ventricular leads were implanted using the cephalic vein cutdown technique, and implantation was accomplished via the prepared right external jugular vein in 4 of the children (9.9%). The atrial leads were implanted using axillary vein puncture and external jugular vein preparations. Mean follow-up was 8.9 years (range 0-20.9 years). Only 1 pacemaker-related complication was detected (a lead fracture near the connector that was successfully resolved using a lead repair kit). CONCLUSION The cephalic vein cutdown technique is feasible and reliable in children weighing ≤10 kg, which justifies the application of additional surgical effort in the treatment of these small patients.