Investigating brain cortical activity in patients with post-COVID-19 brain fog

Brain fog is a kind of mental problem, similar to chronic fatigue syndrome, and appears about 3 months after the infection with COVID-19 and lasts up to 9 months. The maximum magnitude of the third wave of COVID-19 in Poland was in April 2021. The research referred here aimed at carrying out the investigation comprising the electrophysiological analysis of the patients who suffered from COVID-19 and had symptoms of brain fog (sub-cohort A), suffered from COVID-19 and did not have symptoms of brain fog (sub-cohort B), and the control group that had no COVID-19 and no symptoms (sub-cohort C). The aim of this article was to examine whether there are differences in the brain cortical activity of these three sub-cohorts and, if possible differentiate and classify them using the machine-learning tools. he dense array electroencephalographic amplifier with 256 electrodes was used for recordings. The event-related potentials were chosen as we expected to find the differences in the patients' responses to three different mental tasks arranged in the experiments commonly known in experimental psychology: face recognition, digit span, and task switching. These potentials were plotted for all three patients' sub-cohorts and all three experiments. The cross-correlation method was used to find differences, and, in fact, such differences manifested themselves in the shape of event-related potentials on the cognitive electrodes. The discussion of such differences will be presented; however, an explanation of such differences would require the recruitment of a much larger cohort. In the classification problem, the avalanche analysis for feature extractions from the resting state signal and linear discriminant analysis for classification were used. The differences between sub-cohorts in such signals were expected to be found. Machine-learning tools were used, as finding the differences with eyes seemed impossible. Indeed, the A&B vs. C, B&C vs. A, A vs. B, A vs. C, and B vs. C classification tasks were performed, and the efficiency of around 60-70% was achieved. In future, probably there will be pandemics again due to the imbalance in the natural environment, resulting in the decreasing number of species, temperature increase, and climate change-generated migrations. The research can help to predict brain fog after the COVID-19 recovery and prepare the patients for better convalescence. Shortening the time of brain fog recovery will be beneficial not only for the patients but also for social conditions.

Multidimensional gain control in image representation and processing in vision

A generic model of automatic gain control (AGC) is proposed as a general framework for multidimensional automatic contrast sensitivity adjustment in vision, as well as in other sensory modalities. We show that a generic feedback AGC mechanism, incorporating a nonlinear synaptic interaction into the feedback loop of a neural network, can enhance and emphasize important image attributes, such as curvature, size, depth, convexity/concavity and more, similar to its role in the adjustment of photoreceptors and retinal network sensitivity over the extremely high dynamic range of environmental light intensities, while enhancing the contrast. We further propose that visual illusions, well established by psychophysical experiments, are a by-product of the multidimensional AGC. This hypothesis is supported by simulations implementing AGC, which reproduce psychophysical data regarding size contrast effects known as the Ebbinghaus illusion, and depth contrast effects. Processing of curvature by an AGC network illustrates that it is an important mechanism of image structure pre-emphasis, which thereby enhances saliency. It is argued that the generic neural network of AGC constitutes a universal, parsimonious, unified mechanism of neurobiological automatic contrast sensitivity control. This mechanism/model can account for a wide range of physiological and psychophysical phenomena, such as visual illusions and contour completion, in cases of occlusion, by a basic neural network. Likewise, and as important, biologically motivated AGC provides attractive new means for the development of intelligent computer vision systems.

Controlled synthesis of a large fraction of metallic single-walled carbon nanotube and semiconducting carbon nanowire networks

Controlled synthesis of both single-walled carbon nanotube and carbon nanowire networks using the same CVD reactor and Fe/Al(2)O(3) catalyst by slightly altering the hydrogenation and temperature conditions is demonstrated. Structural, bonding and electrical characterization using SEM, TEM, Raman spectroscopy, and temperature-dependent resistivity measurements suggest that the nanotubes are of a high quality and a large fraction (well above the common 33% and possibly up to 75%) of them are metallic. On the other hand, the carbon nanowires are amorphous and semiconducting and feature a controlled sp(2)/sp(3) ratio. The growth mechanism which is based on the catalyst nanoisland analysis by AFM and takes into account the hydrogenation and temperature control effects explains the observed switch-over of the nanostructure growth modes. These results are important to achieve the ultimate control of chirality, structure, and conductivity of one-dimensional all-carbon networks.

Recognition and correction of subcuticular malposition of pacemaker pulse generators

Implantation of a cardiac pacemaker should be in the tissue plane deep to the subcutaneous tissue (i.e., between the fatty layer and the pectoralis fascia of the chest wall). Five patients with pacemaker implants between the cutis and the subcutaneous fat presented months later with chronic, unremitting, and often excruciating pain. The pulse generator in each case seemed excessively superficial and displaced, appeared too large for its known size, and was seemingly fixed to the overlying skin with exquisite sensitivity to light touch by a garment or palpation. Each had multiple consultations and treatments for pain, all without effect other than the temporary relief of local anesthesia. In three patients with obvious large subcutaneous fatty layers, the pulse generator was markedly superficial. Wound cultures were sterile in each case. Correction consisted of operative repositioning of the pulse generator into the readily developed subcutaneous tissue plane. In each patient, total and permanent relief of pain was achieved. Subcuticular positioning of permanent pacemaker pulse generators causes chronic pain that is readily relieved by operative repositioning of the pulse generator in the proper tissue plane.

Vasoactive intestinal peptide and related molecules induce nitrite accumulation in the extracellular milieu of rat cerebral cortical cultures

Nanomolar concentrations of vasoactive intestinal peptide (VIP), picomolar concentrations of stearyl-norleucine17-VIP (SNV) and femtomolar concentrations of NAPVSIPQ (NAP), an 8-amino-acid peptide derived from the VIP-responsive activity-dependent neuroprotective protein, provide broad neuroprotection. In rat cerebral cortical cultures, 10(-16)-10(-7) M NAP increased intracellular cyclic guanosine monophosphate (cGMP) (2.5-4-fold) and 10(-10) M NAP increased extracellular nitric oxide (NO) by 60%. In the same culture system, VIP and SNV (at micromolar concentrations) increased extracellular NO by 45-55%. The NAP dose required for cGMP increases correlated with the dose providing neuroprotection. However, the concentrations of NAP, SNV and VIP affecting NO production did not match the neuro-protective doses. Thus, NO may mediate part of the cell-cell interaction and natural maintenance activity of VIP/SNV/NAP, while cGMP may mediate neuroprotection.

Calmodulin and profilin coregulate axon outgrowth in Drosophila

Coordinated regulation of actin cytoskeletal dynamics is critical to growth cone movement. The intracellular molecules calmodulin and profilin actively regulate actin-based motility and participate in the signaling pathways used to steer growth cones. Here we show that in the developing Drosophila embryo, calmodulin and profilin convey complimentary information that is necessary for appropriate growth cone advance. Reducing calmodulin activity by expression of a dominant inhibitor (KA) stalls axon extension of pioneer neurons within the CNS, while a partial loss of profilin function decreases extension of motor axons in the periphery. Yet, surprisingly, when calmodulin and profilin are simultaneously reduced, the ability of both CNS pioneer axons and motor axons to extend beyond the choice points is restored. In the CNS, at the time when growth cones must decide whether to cross or not to cross the midline, a reduction in calmodulin and/or roundabout signaling causes axons to cross the midline inappropriately. These inappropriate crossings are suppressed when profilin activity is simultaneously reduced. Interestingly, the mutual suppression of calmodulin and profilin activity requires a minimal level of profilin. In KA combinations with profilin null alleles, defects in axon extension and midline guidance are synergistically enhanced rather than suppressed. Together, our data indicate that the growth cone must coordinate the activity of both calmodulin and profilin in order to advance past selected choice points, including those dictating midline crossovers.

Feasibility and initial results of an Internet-based pacemaker and ICD pulse generator and lead registry

The medical community has no independent source of timely information regarding the performance of pacemaker and ICD pulse generators and leads. Accordingly, the authors established an Internet-based registry of pacemaker and ICD pulse generator and lead failures (www.pacerandicregistry.com). During the first year, they found three previously unreported device problems that were promptly communicated to the participants. Of the failures reported, 11% of ICD and 10% of pacemaker pulse generator failures were heralded by signs other than the expected elective replacement indicator (ERI). Average ICD battery longevity was 4.0 +/- 0.7 years, and average dual chamber pacemaker battery longevity was 6.8 +/- 2.6 years. Disrupted insulation accounted for 54% of pacemaker and 29% of ICD lead failures. Compared to pacemaker pulse generator and lead failure, ICD device failures were more likely to cause severe clinical consequences. In conclusion, an Internet-based registry is feasible and capable of providing timely data regarding the signs, causes, and clinical consequences of pacemaker and ICD failures.

A novel peptide prevents death in enriched neuronal cultures

We have recently cloned a novel protein (activity-dependent neuroprotective protein, ADNP) containing an 8-amino-acid, femtomolar-acting peptide, NAPVSIPQ (NAP). Here we show, for the first time, that NAP exerted a protective effect on glia-depleted neurons in culture. The number of surviving neurons was assessed in cerebral cortical cultures derived from newborn rats. In these cultures, a 24-h treatment with the beta-amyloid peptide (the Alzheimer's disease associated toxin) induced a 30-40% reduction in neuronal survival that was prevented by NAP (10(-13)-10(-11) M). Maximal survival was achieved at NAP concentrations of 10(-12) M. In a second set of experiments, a 5-day incubation period, with NAP added once (at the beginning of the incubation period) exhibited maximal protection at 10(-10) M NAP. In a third set of experiments, a 10-min period of glucose deprivation resulted in a 30-40% neuronal death that was prevented by a 24-h incubation with NAP. Glucose deprivation coupled with beta-amyloid treatment did not increase neuronal death, suggesting a common pathway. We thus conclude, that NAP can prevent neurotoxicity associated with direct action of the beta-amyloid peptide on neurons, perhaps through protection against impaired glucose metabolism.

Recommendations for extraction of chronically implanted transvenous pacing and defibrillator leads: indications, facilities, training. North American Society of Pacing and Electrophysiology Lead Extraction Conference Faculty

The procedure of lead removal has recently matured into a definable, teachable art with its own specific tools and techniques. It is now time to recognize and formalize the practice of lead removal according to the current methods of medicine and the health care industry. In addition, since at this time the only prospective scientific study of lead extraction is the PLEXES trial, we suggest that studies relating to the techniques of and indications for lead extraction be designed. Recommendations for a common set of definitions, for a framework of training and reviewing physicians in the art, for general methods of reimbursement, and for consistency among clinical trials have been made. Implementation of these recommendations will require additional effort and cooperation from practicing physicians, medical societies, hospital administrations, and industry.

Experience with the insertion of vena caval filters in acutely burned patients

The use of inferior vena caval filters in patients at high risk of pulmonary emboli is a standard practice in many types of patients. The usefulness of such filters in acutely burned patients has yet to be established. Twenty inferior vena caval filters were inserted in burn patients. Five were inserted because of preexisting thromboembolic disease. Fifteen were placed prophylactically because of high-risk states, including prolonged immobilization, old age, bleeding problems, and obesity. There were no complications due to filter insertion. No postinsertion emboli were recognized. There were no cases of postinsertion thrombophlebitis. In this small series, the procedure appears to be effective and safe.

Insulation lead failure: is it a matter of insulation coating, venous approach, or both?

Lead insulation material and implant route have a major impact on lead reliability and durability. We compare the incidence of lead insulation failure resulting from both the venous approach and insulation type. Two hundred ninety consecutive leads were followed for a mean period of 57 +/- 30 months; leads with < 1 year follow-up were excluded. There were 116 Silicone Rubber insulated leads and 174 with polyurethane (151 Pellethane 80A and 23 Pellethane 55D) insulation; 279 leads were bipolar and 11 unipolar; 274 leads were implanted in the ventricle and 66 in the atrium. The venous route was the subclavian vein for 170 leads (58%) and the cephalic vein for 120 leads (42%). Insulation failure was diagnosed when a single sign of oversensing, undersensing, failure to capture, early pulse battery depletion, and lead impedance < 250 omega was present. Measurement of lead impedance was performed intraoperatively at implantation and during lead revision or pulse generator replacement. Lead failure caused by conductor coil fracture was not considered. There were 13 lead insulation failures, all among leads with polyurethane insulation (12 Pellethane 80A and 1 Pellethane 55D). Eleven failures (10%) occurred when the subclavian vein and 2 (3%) when the cephalic vein approach was used. The cumulative survival rate of polyurethane and silicone rubber insulated leads was 88.7% and 100%, respectively (P = 0.02); the cumulative survival rate of polyurethane insulated leads was 83.2% when the subclavian vein and 95.1% when the cephalic vein were used (P = 0.03). The mean time to polyurethane lead failure when the subclavian vein approach was used was 54 +/- 17 months and when the cephalic route was 73 +/- 4 months (P < 0.02). By multivariate analysis, the route of entry was found to be a significant variable related to polyurethane insulated lead failure (P < 0.05). At lead revision failure to capture was present in 7, oversensing in 4, and undersensing in 2 instances; impedance was < 250 omega in all cases. Pellethane 80A insulated leads are prone to insulation failure, but more when the subclavian vein is used, rather than the cephalic vein.

Symptomatic improvement after AV nodal ablation and pacemaker implantation for refractory atrial fibrillation and atrial flutter

Symptomatic Improvement was evaluated in 64 patients with drug-refractory atrial fibrillation or atrial flutter who underwent atrioventricular (AV) nodal ablation and permanent pacemaker implantation. The arrhythmias were chronic in 40 patients and paroxysmal in 24 patients. All were refractory to multiple drugs (3.7 +/- 1.5) and had severe symptoms: palpitations (58 patients), dyspnea (n=58), dizziness (n=38), asthenia (n=37), and chest pain (n=20). All underwent AV nodal ablation and single- (n=39) or dual-chamber (n=25) pacemaker implantation. During follow-up of 20.4 +/- 17.8 months, palpitations improved in 100% of 58 patients who had palpitations before the ablation, dyspnea improved in 75% of 58 patients, chest pain in 95% of 20 patients, asthenia in 75% of 37 patients, and dizziness in 93% of 38 patients. Moderate to significant improvement in these symptoms was reported in 83% of patients and mild improvement in 5%. Before ablation, 77% of patients were in New York Heart Association functional class III or IV. After ablation, 19% of patients were in the same functional classes (P < 0.05). Thus, AV nodal ablation and pacemaker implantation in patients with drug-refractory atrial fibrillation or flutter was associated with significant improvement in presenting symptoms and functional capacity. A randomized, controlled study is needed to compare this form of therapy with other therapeutic modalities.

Sodium-dependent transport of phosphate in neuronal and related cells

Sodium-dependent phosphate entry into neuronal cells was demonstrated in synaptic plasma membrane vesicles and synaptosomes prepared from rat brains, in PC12 cells and in primary culture of pituitary cells. The extent of the sodium-dependent phosphate transport in the synaptic plasma membrane preparation, at [Na]out = 110 mM and [P(i)]out = 0.1 mM, varied between 0.28 to 1.02 nmol phosphate/mg membrane protein/min. In pituitary cells the value was only about 0.05 nmol P(i)/mg protein/min. In PC12 cells the activity increased from 0.0085 to 0.26 nmol P(i)/mg protein/min in the transit from undifferentiated to differentiated cells. The dependence of phosphate on sodium concentrations fits a model in which two sodium ions are required to transfer the phosphate into the cells with a K[Na]0.5 of 43 mM. The K(m) for the phosphate transport in the synaptic plasma membrane preparations was between 0.1 and 0.45 mM. It is concluded that sodium-driven active transport of phosphate is a ubiquitous activity in various types of neuronal cells.

Transtelephone monitoring for pacemaker follow-up 1981-1994

Transtelephone monitoring (TTM) is capable of detecting pacemaker pulse generator malfunction, battery depletion, and lead failure. The accuracy of TTM was analyzed by a review of Montefiore Medical Center records between October 1981 and March 1994. Each group of transmissions from a single patient, starting with implant and ending with a pacemaker operation, was defined as a closed cycle (CLOSE), if undergoing continuing follow-up at the time of analysis, as a continuing cycle (CONT), and if a cycle had ended with death or loss to follow-up, an open cycle (OPEN). TTM records of 2,632 patients were analyzed, providing 3,291 cycles. There were 731 CONT, 433 CLOSE, and 2,127 OPEN cycles; 331 procedures were indicated by TTM, of which 279 were impending depletion, 30 sudden depletion, and 22 lead malfunctions. Of the 102 procedures not indicated by TTM, 85 were for nonurgent reasons (recall: 41; DDD upgrade: 16; patient/MD request: 28) and 17 for urgent reasons. In patients followed by TTM who had a lead problem, 22 were detected by TTM before clinical manifestations and 16 were not. There were no cases in which TTM follow-up did not detect battery depletion. The total number of TTM contacts, available for 3,094 cycles, was 88,654 (range, 1-163, median 19), of which 0.4% yielded a procedure. During the same period, 75% of all secondary interventions during the first 2 years occurred during the first 2 months after implant because of lead malfunction, with a subsequent SI rate of 0.005 per month for the third through the twenty-fourth months.

Comparison of long-term outcomes of patients treated with nonthoracotomy and thoracotomy implantable defibrillators

In 193 consecutive patients treated with implantable defibrillators at our institution, thoracotomy approaches were used in 87 patients and nonthoracotomy approaches in 106 patients. Long-term outcomes of the 2 groups were compared by the intention-to-treat analysis. Surgical mortality (30-day mortality) rates were 5.7% in the thoracotomy group and 0% in the nonthoracotomy group. Six of 106 patients who underwent nonthoracotomy implantation had a high defibrillation threshold and did not receive nonthoracotomy defibrillators. The duration of follow-up was 52 +/- 31 months in the thoracotomy group, and 23 +/- 15 months in nonthoracotomy group. Actuarial survival rates at 6 and 24 months were, respectively, 90% and 81% in nonthoracotomy patients and 89% and 80% in thoracotomy patients (p = NS). In patients with left ventricular ejection fraction <30%, surgical mortality was 0% by the nonthoracotomy and 10% by the thoracotomy approach. Despite the 10% difference in 30-day mortality, survival rates at 6 months were 85% in nonthoracotomy patients and 81% in thoracotomy patients. At 24 months they were 73% in nonthoracotomy patients and 74% in thoracotomy patients. Thus, this nonrandomized study suggests that while short-term survival is better in nonthoracotomy patients than thoracotomy patients, the difference in survival diminishes quickly during the first few months and disappears by 6 months. The results were similar in patients with severe ventricular dysfunction. Several important implantable-cardioverter defibrillator (ICD) trials initially utilized thoracotomy ICDs. Although questions may be raised with regard to applicability of such a trial in the era of nonthoracotomy ICDs, this study suggests that the results of such ICD trials will be largely applicable to patients treated with nonthoracotomy ICDs.

Effect of varying atrial sensitivity, AV interval, and detection algorithm on automatic mode switching

Automatic mode switching (AMS) is absolutely dependent on atrial tachyarrhythmia detection. The effects of programming several features that could influence tachyarrhythmia detection were assessed in 18 patients (six women; mean age 64 years) with pacemakers having AMS capability. The atrial electrogram amplitude in sinus rhythm at implant (SR-EGM), last measured atrial sensing threshold prior to tachycardia (A-SENS), and atrial sensing threshold for effective AMS during atrial tachyarrhythmia (AMS-SENS) were obtained. Additionally, ten patients had AV intervals increased from 60 to 200 ms, while seven patients had detection algorithms made more stringent from 5 beats at 150 beats/min to 11 beats at 200 beats/min to assess their effects on AMS efficacy.

RESULTS

Sensitivities:Mean SR-EGM = 3.55 mV; mean A-SENS = 2.06 mV; and mean AMS-SENS = 1.46 mV. Fourteen patients developed atrial fibrillation and four atrial flutter. Thirteen of 14 patients who developed atrial fibrillation sensed adequately at > or = 1.0 mV in normal sinus rhythm (NSR), but only six patients had effective AMS at these settings in atrial fibrillation. Three of four patients who developed atrial flutter had effective AMS at > or = 2.0 mV. AV Interval:AMS was effective in eight of ten patients at AV intervals up to 200 ms. One patient lost AMS at an AV interval of 120 ms. Algorithm: In two of seven patients, AMS was not effective if the detection algorithm was more stringent than five beats at 150 beats/min.

CONCLUSIONS

(1) In atrial fibrillation, effective AMS requires more sensitive atrial settings than in NSR; (2) AV intervals as short as 120 ms can interfere with AMS function; and (3) More stringent detection algorithms may be inappropriate for effective AMS function.

Failure rates of leads, pulse generators, and programmers have not diminished over the last 20 years: formal monitoring of performance is still needed. BILITCH Registry and STIMAREC

Formal Monitoring of Performance is Still Needed. In order to detect trends in the number of device or component failures that have occurred among permanent pacemaker systems since the 1970s, we reviewed the data of the five largest pacemaker manufacturers from the Bilitch Registry of permanent pacemaker pulse generators, the Stimarec failure registry, the general accounting office summaries of the United States Veterans Administration (VA) Registry of Pacemaker Leads, and the Implantable Lead Registry, from the Cleveland Clinic Lead registry, and the recalls and safety alerts issued by the United States Food and Drug Administration (FDA) over the last 20 years. The definition of failure followed the criterion, or criteria, developed within each registry and differed significantly between the registries. The 20-year period between 1976 and 1995 was divided into 5-year quartiles (QT): QT 1 = 1976-1980; QT2 = 1981-1985; QT3 = 1986-1990; and QT4 = 1991-1995. For pulse generators, the number of models with failures in each quartile in the Bilitch Registry were: QT 1 = 9; QT 2 = 11; QT3 = 17; QT4 = 13. In Stimarec, the number of units reported as having reached a dangerous condition were: QT1 = 710; QT2 = 212; QT3 = 114; QT4 = 310. From the FDA reports, the number of units included in recalls or safety alerts were: QT3 = 6,085; QT4 = 135,766. For permanent pacemaker leads, the numbers of failed or dangerous leads recorded in Stimarec were: QT3 = 16; QT4 = 32. In the VA Registry, the number of models having a below average survival was 2/92 (2.7%). In the Implantable Lead Registry, the number of models having a below average survival was 3/21 (14%). In the Cleveland Clinic series, 6/13 (46%) of lead models were recognized to have some failure involving the conductor, insulation, or connector. In the FDA reports, the number of leads involved in either recall or safety alert were: QT3 = 20,354; QT4 = 332,105. For programmers, the number of units involved either in a recall or safety alert were: QT3 = 11,124; QT4 = 3,528. In all of these series, each of the five largest manufacturers had some models or units involved in each time period. This review of programs has revealed: 1. The incidence of failures, recalls, or safety alerts did not decline over time; and 2. Despite changes in technology, formal monitoring of pacemaker systems is still warranted.

Lead fracture in cephalic versus subclavian approach with transvenous implantable cardioverter defibrillator systems

Lead fracture, occurring in approximately 1%-4% of patients, is an infrequent, but potentially catastrophic complication of permanent pacing systems. Its incidence in transvenous defibrillator systems has not been established. We analyzed data from 757 patients undergoing implantation of transvenous cardioverter defibrillator systems using the Medtronic Transvene Lead system between October 20, 1989 and June 25, 1992 to determine if site of venous approach influenced incidence of lead fracture. All patients received a 3-lead system in 1 of 3 configurations: (1) right ventricle/superior vena cava/subcutaneous patch; (2) right ventricle/coronary sinus/subcutaneous patch; or (3) right ventricle/superior vena cava/coronary sinus. Of 767 right ventricular leads placed, 523 were placed via the subclavian vein, 221 via cephalic vein, and 18 via the internal jugular (5 leads were implanted using another vein). The total number of leads is greater than the total number of patients, as five patients received a second defibrillator system if the initial system was explanted and reimplanted for any reason. Seven patients (0.9%) had right ventricular lead fracture, presenting with inappropriate defibrillator shocks (1), loss of pacing ability (3), both loss of pacing ability and inappropriate shocks (1), or increased pacing threshold (2). All patients required reoperation. All had leads placed by the subclavian venous approach, with chest X ray confirming fracture at the clavicle-first rib junction in 6 of 7 cases. Using Fisher's Exact test, the difference in lead fracture between subclavian and cephalic vein implant approached statistical significance (P = 0.08). The trend toward increased lead fracture incidence with leads placed via subclavian vein suggests that cephalic vein approach may be preferable to avoid this complication.

The SASPREN primary care survey -- who consults the family doctor?

OBJECTIVE

To describe selected characteristics of patients consulting general/family practitioners in the Western Cape.

DESIGN

A cross-sectional survey design was employed in which doctors completed a structured questionnaire during or immediately after each consultation.

SETTING

Data were collected by family practitioners in private practice who were affiliated to the South African Sentinel Practitioner Research Network (SASPREN).

PARTICIPANTS

All patients who had a face-to-face encounter with the doctor at his/her surgery. A total of 2 473 such encounters was included.

MAIN OUTCOME MEASURES

Age, sex, race, method of payment and smoking status.

RESULTS

Females outnumbered males in all race groups except blacks, where they comprised 48% of patients. Most patients were under the age of 14 years (23.3%) or between 25 and 44 years (33.3%). However, after the demography of the catchment population was taken into account, the highest utilisation of general practitioner services was found to be at extremes of age. This utilisation pattern was demonstrated in both sexes and all races. In relation to their distribution in the population, whites and Indians are over-represented in private practice while blacks and coloureds are under-represented. The bulk of patients (67%) pay for general practitioner services via some form of insurance (medical aid or benefit fund), but significant differences exist across race groups. In the case of blacks and Indians, the majority (72% and 64% respectively) of consultations are funded 'out of pocket'. An alarmingly high smoking prevalence was found in black and coloured men. In all race/sex groups smoking rates peak between 25 and 44 years. In this age group, 68.6% of black men and 73.3% of coloured men were current smokers.

CONCLUSIONS

This study provides essential information on patients seen in family practice. Access to family doctor services in the Western Cape should be improved for blacks and coloureds. There is an urgent need for smoking cessation interventions in the region.

Suppression of ventricular output by noise in the atrial channel in a dual chamber pacemaker

In a pacemaker dependent, 60-year-old man with complete heart block, programming high (5.0 V and 1.0 ms) atrial output and 5.0 volt and 0.5 ms ventricular output while in the DDD mode of a pulse generator, resulted in loss of ventricular channel output with resulting asystole, while the simultaneous, pulse generator produced ECG interpretation channel falsely indicated continuing ventricular channel output. Ventricular pacing was promptly restored by programming to the emergency VVI mode. At later operation the atrial lead was determined to be defective, with a low impedance, while the ventricular lead was intact (lead impedance telemetry was not available). The manufacturer has acknowledged a pulse generator design anomaly that may occur in the setting of a low atrial impedance and issued a Health Safety Alert.

Long-term outcomes and modes of death of patients treated with nonthoracotomy implantable defibrillators

Long-term outcomes of all patients who underwent nonthoracotomy implantable cardioverter-defibrillator (ICD) implantation at our institution from April 1991 to October 1994 were studied using the intention-to-treat analysis. Of 94 consecutive patients, 81 underwent nonthoracotomy ICD implantation and 13 underwent thoracotomy (for concomitant surgery in 11 and unavailability of nonthoracotomy leads in 2). Six of 81 patients had a high defibrillation threshold, 4 subsequently underwent thoracotomy, and 2 were treated with amiodarone. Surgical mortality was 0%. The duration of follow-up was 20 +/- 13 months, and was > 12 months in 74% of 67 living patients. Actuarial survival rates at 1 and 2 years were, respectively, 98% and 94% for sudden death and 91% and 83% for total mortality. Deaths during long-term follow-up were mostly due to nonsudden cardiac or noncardiac deaths. Two-year mortality rates were 12% and 25% in patients with ejection fraction > or = 30% and < 30%, respectively. Thus, instances of sudden death and surgical mortality are very few in patients with nonthoracotomy ICDs. Deaths during long-term follow-up are mostly due to nonsudden cardiac and noncardiac deaths. Therefore, ICD therapy may have greater impact on survival in patients with lower risks of nonsudden cardiac and cardiac death (e.g., younger patients with minimal heart disease) than in patients with severe cardiac or noncardiac disease. Prospective studies are needed to address this question.

Long-term follow-up of pacemaker lead systems: establishment of standards of quality

The functional details of all 5,405 pacemaker leads implanted on Montefiore Medical Center were contemporaneously recorded between 1960 and May 31, 1993. Some models have been observed for as long as 24 years. Ventricular leads with more than 50 and atrial leads with more than 30 implanted units have been continually and repeatedly subjected to actuarial cumulative survival rate (CSR) analysis during which clinical decisions, such as continued lead implantation, cessation of use, or early withdrawal from service, were made. CSR evaluation for many lead models by the Mantel-Haenszel method allowed comparison of the performance of contemporaneous lead models with older and new technologies. No effect on lead longevity, durability, on mode of end of lead service, lead removal independent of function (e.g., for infection), materials, or physiological failure was found due to an operator or anatomical route of venous access. Multifilar silicone rubber insulated leads have longevity (CSR) superior to monofilar silicone rubber leads. The cumulative survival of silicone rubber insulated monofilar models 6901, 6907, continuous lead (CL), 4 mm, and 2 mm was 79%-91%, 20 years after implantation. Multifilar silicone rubber insulated models 6961 and 4116 had a cumulative survival of 99%-100%, 15 years after implantation. Among multifilar polyurethane insulated leads, distinct longevity differences exist between formulations and contemporaneous models that are normally similar, yielding a bimodal longevity distinction; model 6971 (ventricular) has 95% CSR and 6991U (atrial) has 94% CSR, 10 years after implantation. Both performed less well than other contemporaneous models, which approximate 100% CSR. The 10-year CSR for leads implanted between 1960-1975 (Era 1) is 98.7%, and the 10-year CSR of leads implanted between 1981-1985 (Era 3) is 99.4%. Comparison of individual lead models, and all leads of specific eras, allows development of survival expectations and standards of quality for comparison between contemporaneous lead models and different eras of manufacture. As the highest available lead CSR sets the standard, statistical deviation of a model from the best performance of a specific era should be considered as an indication of reduced quality.

Direct and telemetered lead impedance

OBJECTIVES

We undertook this study to determine whether telemetered lead impedance measurements (LIM) can be correlated with direct LIM and to determine the stability of LIM over time when measured directly and via telemetry.

METHODS

Direct LIM and telemetered LIM were measured in 91 patients; 101 leads during initial implantation and 40 leads during pulse generator replacement. Differences in direct LIM measured during initial implant and pulse generator replacement (direct-direct) were compared in 41 patients (28 atrial leads and 37 ventricular leads). The stability of telemetered LIM obtained immediately postoperatively, at 1 month and 1 year, postimplantation was assessed in 50 patients (23 atrial and 49 ventricular leads).

RESULTS

In atrial leads acute direct LIM was 633.9 +/- 18.4 omega versus 575.8 +/- 18.5 omega for telemetered LIM (r = 0.58), and chronic direct LIM was 670.9 +/- 49.3 omega versus 607.0 +/- 36.3 omega for telemetered LIM (r = 0.87). In ventricular leads acute direct LIM was 747.3 +/- 16.9 omega and 684.7 +/- 16.4 omega for telemetered LIM (r = 0.69), and chronic direct LIM was 674.8 +/- 29.9 omega and 625.2 +/- 28.5 omega for telemetered LIM (r = 0.68). The mean direct-direct LIM rose 124 omega (P < 0.001) in atrial leads and 10 omega (P = NS) in ventricular leads. Telemetered LIM for atrial leads was 581.0 +/- 27.6 omega immediately postimplantation compared to 625.7 +/- 34.8 omega at 1 month and 754.1 +/- 43.0 omega at 1 year. Telemetered LIM for ventricular leads was 661.3 +/- 17.5 omega at implant, 684.6 +/- 20.7 omega at 1 month and 724.7 +/- 22.7 omega at 1 year.

CONCLUSIONS

There is a good but limited correlation between direct and telemetered LIM. Mean direct LIM obtained at initial implantation is similar to that measured at pulse generator replacement. The telemetered LIM is stable over the first month postimplantation but tends to rise during the first year of follow-up and substantial changes in impedance are not uncommon in individuals with normal function. There is a tendency for LIM to rise with lead maturation. If telemetered LIM is to be followed over time, a baseline telemetered value should be obtained immediately postoperatively.

Comparison of defibrillator therapy and other therapeutic modalities for sustained ventricular tachycardia or ventricular fibrillation associated with coronary artery disease

Outcomes of 282 patients referred to the arrhythmia service at Montefiore Medical Center for sustained ventricular tachycardia (n = 214) or ventricular fibrillation (n = 68) associated with coronary artery disease were analyzed retrospectively. All patients underwent serial drug trials by electrophysiologic testing and Holter monitoring. Sixty-eight patients who did not respond to drug therapy were treated with implantable cardioverter-defibrillators (ICD group), and 214 patients were treated with other methods guided by electrophysiologic testing and Holter monitoring (non-ICD group). The non-ICD group included 49 patients who responded to drug therapy as judged by electrophysiologic testing, as well as patients who did not respond and were not treated with defibrillator therapy for various reasons. Ten patients died in the hospital (2 patients in the ICD group, 8 in the non-ICD group). Actuarial survival rates free of total cardiac death at 1, 2, and 3 years were, respectively, 94%, 87%, and 85% in the ICD group, and 82%, 78%, and 73% in the non-ICD group (p = NS). Survival rates free of total death at 1, 2, and 3 years were 90%, 82%, and 76% in the ICD group, and 82%, 76%, and 70% in the non-ICD group, respectively (p = NS). Survival rates free of total cardiac and total deaths of 49 patients treated with an effective regimen determined by electrophysiologic testing were not significantly different from those of the ICD group. This retrospective study suggests that outcomes of patients treated with ICDs may not be dramatically different from those of patients treated with other methods guided primarily by electrophysiologic testing.(ABSTRACT TRUNCATED AT 250 WORDS)

ICD implantation via thoracoscopy, "mailslot" thoracotomy, and subxiphoid incision

An improved method of thoracoscopic implantable cardioverter defibrillators implantation is described. "Mailslot" thoracotomy is more expeditious than thoracoscopic implantation via multiple ports. If required for adequate defibrillation thresholds, subxiphoid, subdiaphragmatic implantation of a defibrillator patch may be performed.

Report of the NASPE Policy Conference training requirements for permanent pacemaker selection, implantation, and follow-up. North American Society of Pacing and Electrophysiology

NASPE proposes and supports the concept of a two-tracked training system in cardiac pacing. Track I training will properly train physicians for the prescription of pacemakers and the monitoring of pacemaker patients, and track II training will properly prepare physicians for the implantation of pacemakers. Regardless of specialty (cardiologist or surgeon) or training venue (cardiac pacing fellowship, cardiac electrophysiology and pacing fellowship, sabbatical or mentor sponsored training), it is recommended that these minimum standards be required for hospital credentialing. NASPE also supports the voluntary institution by training program directors of core pacing training in cardiovascular disease and cardiac electrophysiology fellowships. This core training does not in itself constitute proper track I or II training for physicians interested in adequately prescribing, monitoring, or implanting cardiac pacemakers.

Cefetamet pivoxil vs cefaclor in the treatment of acute otitis media in children

74 children with acute otitis media (AOM) were entered into an observer-blind randomised multicentre general practice study to compare the efficacy and safety of the new third generation oral cephalosporin, cefetamet pivoxil, at a dose of 10 mg/kg twice daily with the efficacy and safety of cefaclor 10 mg/kg twice daily administered for 10 days. Of 36 evaluable patients in the cefaclor treatment group, 28 (78%) were cured, and a further 4 were improved, giving an overall efficacy rate (cure/improvement) of 89%. Of 36 evaluable patients in the cefetamet pivoxil treatment group, 31 (86%) were cured, and a further 4 were improved, giving an overall efficacy rate of 97%. Adverse events were reported in 4 patients: 1 cefaclor recipient and 3 patients in the cefetamet pivoxil treatment group. Diarrhoea, the most frequently observed adverse event, occurred in both treatment groups. The study results indicate that cefetamet pivoxil and cefaclor appear to have similar efficacy and safety in the treatment of AOM in children.

Influence of left ventricular function on survival and mode of death after implantable defibrillator therapy (Cleveland Clinic Foundation and Montefiore Medical Center experience)

To determine the influence of left ventricular (LV) function on survival and mode of death in patients with an implantable cardioverter-defibrillator (ICD), sudden death, surgical mortality, total arrhythmia-related death, total cardiac death and total death were retrospectively evaluated in 377 consecutive patients. The outcomes were also compared between patients with an LV ejection fraction > or = 30% (214 patients, group 1) and < 30% (148 patients, group 2). Surgical mortality was 3.9% (1.8% in group 1, 7% in group 2). During the follow-up of 25 +/- 20 months, actuarial survival rates of all patients at 3 years were 96% for sudden deaths, 81% for total cardiac deaths and 74% for total mortality. When the 2 groups were compared, survival rates of groups 1 and 2 at 3 years, respectively, were 99 and 90% for sudden death (p < 0.05), 97 and 84% for sudden death and surgical mortality (p < 0.01), 94 and 80% for the total arrhythmia-related death (p < 0.001), 88 and 68% for total cardiac death (p < 0.0001), and 81 and 62% for total mortality (p < 0.002). In group 2, 73% of total cardiac deaths within 1 year were causally related to the arrhythmia. Thus, in patients with an ICD, sudden death rates were very low. However, total cardiac death and total death rates were relatively higher. The outcomes of patients with an ICD were strongly influenced by the degree of LV dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical removal of infected transvenous pacemaker leads

Infection, though uncommon, can be the most lethal of all potential complications following transvenous pacemaker implantation. Eradication of infection associated with pacemakers requires complete removal of all hardware, including inactive leads. Since 1972, 5,089 patients have had 8,508 pacemaker generators implanted at Montefiore Medical Center. There were 91 infections (1.06%); four of our patients required surgical removal. Nine additional patients were referred for surgical removal of infected transvenous pacemaker leads from other institutions. Surgical methods for removal included use of cardiopulmonary bypass or inflow occlusion. Surgery may be safely used in unstable or elderly patients and should not be reserved as a last resort. This article reviews our surgical experience removing infected pacemaker leads at Montefiore Medical Center.