Dusan Velimirovic

The Etiology of Syncope in Pacemaker Patients

A total of 46 patients with syncopal episodes after VVI pacemaker implantation were studied. Of these, 92% had one to three syncopal episodes and 8% more than three. All underwent a thorough clinical examination, which included chest X ray, echocardiogram, neurological exam, and the following protocol: 24‐hour Holler monitoring, EEG, blood pressure (BP) measurement in three positions, Doppler exam of the carotid vessels, fasting blood glucose, and head‐up tilt table test (60 minutes, 60°). Holter monitoring showed exit block in two patients (4.3%) and failed sensing in one (2.1%). In two patients there was unilateral slowing on EEG. Orthostatic hypotension was found in four patients (8.6%), and hypoglycemia in three insulin‐dependent diabetics. An ocdusive atherosclerotic plaque in the carotid artery was found in three patients (6,5%). Syncope was induced in 17 patients (36,9%) by the tilt table test, after a mean standing time of 47 ± 11 minutes. The mean resting systolic BP of these patients was 140 ± 24 mmHg, and fell to a mean level of 56 ± 8 mmHg (mean systolic BP drop was 79 ± 8 mmHg). Sixteen of these 17 patients with positive tilt table were being paced at the time of syncope and one had a spontaneous heart rate of 73 beats/min. In 14 cases (30.4%) the cause of syncopai episodes after this extensive workup remained unexplained. These results indicate that pacemaker dysfunction is a not major cause of syncopal episodes in pacemaker patients and that these are most often due to vasovagal syncope. Long‐term follow‐up is warranted to determine the prognostic significance of various types of syncope in pacemaker patients.

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).

Circadian Variations of Heart Rate and STIMT Interval: Adaptation for Nighttime Pacing

DJORDJEVIC, M., et al.: Circadian Variations of Heart Rate and STIM‐T Interval: Adaptation for Nighttime Pacing. In order to determine the optimal pacing rate for pacemaker patienfs at night, 150 normal subjects with regular sinus rhythm and free of manifest heart disease, were studied using 24‐hour Rolter monitoring. Minimum and average heart rates were analyzed on an hourly basis. The study group was divided into six age groups, 25 subjects each, ranging from 20–29 years to 60–69 years. The minimum heart rate during the night was found to be lower than 65 ppm for all groups. The youngest subjects showed the largest variation in the minimum heart rate. The results suggest that an automatic lowering of the pacing rate during the night would allow for longer periods of sinus rhythm, thereby improving hemody‐namic performance and reducing pacemaker power consumption. Suitable sensors for automatic lowering of the pacing rate include inbuilt 24‐hour clock systems and the QT interval that lengthens during sleep.

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.

Epidural lead fracture caused by material processing fault.

Fracture of the epidural lead (Pisces Quad 3487) is documented in four out of eight patients with an implanted Itrel pacing system for treatment of peripheral vascular disease. In two patients, lead fracture was established during x‐ray fluoroscopy. In the remaining two patients, x‐ray examination did not reveal any fracture, due to proximity of the fragments. Microscopic examination of the extracted lead, however, confirmed lead fracture, as well as the presence of tissue fluid and thrombus between the two ends of the spiral shaped lead, but no insulation defect was observed. A cross‐sectional area on the fracture line of the broken lead was examined using scanning electron microscopy. It was found, by tracing the radial marks to their point of convergence, that the initial microcrack started from a large inclusion of the calciumsilicon type at the lead surface. The initial microcrack was propagated by the fatigue mechanism. The presence of a large inclusion at the surface suggests that the main cause of the failure of the investigated epidural leads could be improper fabrication of the material. The high incidence of epidural lead fracture in our group suggests that this complication should be considered as a possible cause of epidural spinal electrical stimulation pacing system dysfunction.

The Loss of Circadian Heart Rate Variations in Patients Undergoing Mitral Valve Replacement and Corridor Procedure — Comparison to Heart Transplant Patients

We have presently demonstrated that when added to mitral valve replacement (MVR) the corridor procedure is 75% efficient in restoring and maintaining sinus rhythm in patients with chronic atrial fibrillation (AF), caused by rheumatic mitral valve disease, (follow up 13.9months). In the same patient population, we observed that the typical day-night cycle heart rate (HR) variations were lost and our present study concentrates on this subject. Heart rate variability analysis based on 24-h Holter ECG recording (StrataScan 563 DelMar Avionics) or hospital discharge (12th-14th postoperative days) was performed in 3 patient groups: Group I: Patients with a Corridor procedure added to MVR (12pts, m/f 10/2, mean age 47.3+/-7.5yr); Group II (control): with patients MVR performed through the left atrial approach, without additional antiarrhythmic procedures (10pts, m/f 3/7 mean age 51.5+/-6.7yr), and Group III: heart transplant recipients (5pts, mean age 46.4+/-11.22yr). We analyzed the hourly heart rate over 24-h period divided into three 8-h segments (07-14h; 15-22h and 23-06h). Statistical comparison of mean hourly heart rate values was made between the three time periods of Holter monitoring. The Corridor procedure performed with mitral valve replacement resulted in conversion of sinus rhythm in 75% of patients (Group I), but postoperative heart rate variability analyses based on Holter monitoring disclosed that the mean heart rate was not statistically significantly difficult between the three 8-h segments of the day-night (P>0.05). The same results were found in the group of patients after heart transplant (P>0.05). The same results were found in the group of patients after heart transplant (P>0.05). In the second group (classical MVR), statistically significant differences in mean HR variation existed between the three 8-h intervals (P<0.05), and although atrial fibrillation occurred postoperatively physiologic circadian heart rate variations were preserved. With the Corridor procedure, both atria were surgically and electrically isolated and chronotropic function of the ventricles was restored by creating a small strip of atrial tissue with isolated sinus node and atrio-ventricular node, connected to the ventricles. This technique produced heart denervation nervous system influence, producing the loss of circadian HR variations, similar to the transplanted heart.

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.