Inappropriate Shock Despite Successful Termination of Supraventricular Tachycardia by Antitachycardia Pacing during Charging

We present a case of a 70‐year‐old man who received an inappropriate implantable cardioverter‐defibrillator shock for sinus tachycardia falling outside of the ventricular tachycardia zone. This occurred after termination of supraventricular tachycardia falling into the ventricular fibrillation zone by antitachycardia pacing. Particularities of the programming algorithms are reviewed. (PACE 2010; 33:e81–e83)     

Factor structure of paediatric timed motor examination and its relationship with IQ

Aim Brain systems supporting higher cognitive and motor control develop in a parallel manner, dependent on functional integrity and maturation of related regions, suggesting neighbouring neural circuitry. Concurrent examination of motor and cognitive control can provide a window into neurological development. However, identification of performance‐based measures that do not correlate with IQ has been a challenge. Method Timed motor performance from the Physical and Neurological Examination of Subtle Signs and IQ were analysed in 136 children aged 6 to 16 (mean age 10y 2.6mo, SD 2y 6.4mo; 98 female, 38 male) attending an outpatient neuropsychology clinic and 136 right‐handed comparison individuals aged 6 to 16 (mean age 10y 3.1mo, SD 2y 6.1mo; 98 female, 38 male). Timed activities – three repetitive movements (toe tapping, hand patting, finger tapping) and three sequenced movements (heel–toe tap, hand pronate/supinate, finger sequencing) each performed on the right and left – were included in exploratory factor analyses. Results Among comparison individuals, factor analysis yielded two factors – repetitive and sequenced movements – with the sequenced factor significantly predictive of Verbal IQ (VIQ) (ΔR²=0.018, p=0.019), but not the repetitive factor (ΔR²=0.004, p=0.39). Factor analysis within the clinical group yielded two similar factors (repetitive and sequenced), both significantly predictive of VIQ, (ΔR²=0.028, p=0.015; ΔR²=0.046, p=0.002 respectively). Interpretation Among typical children, repetitive timed tasks may be independent of IQ; however, sequenced tasks share more variance, implying shared neural substrates. Among neurologically vulnerable populations, however, both sequenced and repetitive movements covary with IQ, suggesting that repetitive speed is more indicative of underlying neurological integrity.     

Implantation of a Cardioverter/Defibrillator in the Subpectoral Region Combined with a Nonthoracotomy Lead System

An implantable cardioverter defibrillator was placed into a sub-pectoral pocket via the incision for cephalic venotomy during implantation of a nonthoracotomy lead system. The approach obviated another incision and subcutaneous tunneling of the leads. There were no perioperative complications and after 6 months of follow-up, the patient continues to tolerate the device satisfactorily.     

ORBITAL CELLULITE AND PRESEPTAL CELLULITE IN CHILDHOOD

A study was made of 112 children with preseptal cellulitis, orbital cellulitis, subperiosteal abscess, and orbital abscess. These were consecutive admissions to the Royal Alexandra Hospital for Children, Sydney, during the period June 1976 to August 1985. The average age was 3 years 6 months. The clinical and radiological signs for each group were defined.
Of the 112 children, 43.8% (with an average age of 3 years 3 months) had a clinical history of an upper respiratory tract infection. Trauma was a factor in 13.4% of patients.
Haemophilus influenzae was recovered from blood culture in two patients and from conjunctival culture in seven patients. The average age of this group was 3 years 7 months.
Plain radiographs taken of 53 patients revealed evidence of paranasal sinus disease in 29 (54.7%). Computerized tomography was performed in 14 patients.
Of seven patients requiring surgical drainage of orbital or subperiosteal abscess (average age 7 years 2 months), five had clinical upper respiratory tract infection.     

The effect of intravascular transfusion for rhesus haemolytic disease on umbilical artery Doppler flow velocity waveforms

Summary. To test the hypothesis that an increase in fetal blood viscosity is associated with an increase in resistance to flow, the effect on Doppler flow velocity waveforms of percutaneous umbilical blood sampling and intravascular transfusion was studied in 20 patients undergoing a total of 35 procedures. All but four of the 22 transfusions were associated with a decrease in resistance to flow, as shown by a reduction in the umbilical artery systolic/diastolic ratio, and this also occurred on 10 of the 13 occasions when blood sampling only was performed. These findings suggest that acute changes in blood viscosity following intravascular transfusion arc not associated with an increase in resistance to flow as assessed by Doppler velocimetry. Umbilical blood sampling per se may be associated with a Immorally mediated reduction in placental vascular resistance to flow.     

Impact of Dual Chamber Pacing on the Incidence of Atrial and Ventricular Tachyarrhythmias in Recipients of Implantable Cardioverter Defibrillators

Recent observations suggest that frequent dual-chamber pacing in recipients of implantable cardioverter defibrillators (ICD) may adversely influence clinical outcomes. This prospective, multicenter study examined the relationship between the frequency of atrial (%AP) and ventricular pacing (%VP) and the incidence of atrial (AT) and/or ventricular tachyarrhythmias (VT) in a standard ICD population. A total of 141 consecutive patients with primary and secondary ICD indications were studied. Continuous arrhythmia detection with a dual-chamber ICD revealed paroxysmal AT in 60 (43%) and VT in 72 (51%) patients within 6 months of device implantation. Far-field oversensing of ventricular signals occurred in 13% of all "atrial tachy response" mode switches. Without adjustment for covariates, a higher %AP was associated with an increased incidence of AT (P < 0.05). However, this association remained only weakly significant after adjustment for covariates using a multivariate model. High New York heart failure functional classes correlated significantly with AT (P = 0.02) and VT (P = 0.007). Rate-modulated pacing, programmed in 1/3 of patients, correlated with occurrence of AT (P = 0.006), but not with occurrence of VT. With respect to dual-chamber pacing, a %AP ≥ 48% combined with a %VP > 40% was associated with an increased probability for VT. In conclusion, AT and VT occurred frequently within 6 months after dual-chamber ICD implantation. High rates of DDD/R stimulation were associated with a trend toward higher incidence of AT, VT, or both.     

High-Density Circumferential Pulmonary Vein Mapping with a 20-Pole Expandable Circular Mapping Catheter

The differentiation of pulmonary vein (PV) electrograms from atrial far-field signals during PV isolation (PVI) for atrial fibrillation (AF) may be difficult. In addition, owing to highly variable PV ostial sizes, current fixed-diameter circular PV mapping catheters may not yield optimal electrograms. We evaluated an expandable, circular 15–25 mm diameter, 20-pole mapping catheter for PV mapping during sustained AF in 25 patients. After selective PV angiography to define the ostial position and size, the catheter was introduced into each PV and withdrawn to the most stable proximal position, with optimal wall contact ensured by progressive loop expansion. At each PV ostium, electrograms recorded at high resolution (HR) were compared with those recorded at a resolution similar to that of a standard 10-pole Lasso catheter. After PVI performed during ongoing AF, the presence of residual far-field potentials (FFP) under both set-ups was compared. We mapped 97 PV, including 4 pairs with common ostia. In the HR recordings, the PV potentials had greater amplitude (0.5 ± 0.1 vs 0.3 ± 0.1 mV, P = 0.001) and fragmentation, whereas left atrial FFP were minimized. After successful isolation of all PV, FFP were observed in 33% of left superior and 28% of left inferior PV on the HR recordings, compared to 66% and 61%, respectively under normal resolution. Catheter stability and optimal wall contact, in combination with HR electrograms can optimize circumferential PV mapping during AF and improve the discrimination of FFP postablation.     

Incidence and Prevention of Cardiac Tamponade Complicating Ablation for Atrial Fibrillation

Cardiac tamponade complicating catheter ablation of atrial fibrillation (AF) occurs in approximately 1% of pulmonary vein isolation (PVI), and up to 6% of linear ablation procedures. We reviewed 348 consecutive AF ablation (including repeat) procedures over 1 year, which all included PVI, with additional linear lesions at the mitral isthmus in 73%, and cavotricuspid isthmus (CTI) in 76%. An irrigated-tip ablation catheter was used, with power limited to 25–35 W for PVI and 45–60 W for linear lesions. Tamponade occurred in seven men and three women (2.9% of the population) during the creation of linear ablation lesions. Mechanical perforations occurred in two patients, and "popping" during radiofrequency (RF) energy delivery at the mitral isthmus in six, and at the CTI in two patients. Peak RF power was significantly higher in patients with than without tamponade (53 ± 4 W vs 48 ± 7 W; P = 0.02), and was greater than 48 W in all cases of "popping." In the following year, RF power for linear ablation was limited to ≤42 W. Among 398 procedures, tamponade occurred in four patients (1.0%; P = 0.047 vs first year), three from "popping" and one from mechanical trauma. Procedural success rate remained the same despite reduction of power. Risk of tamponade was highest during linear ablation, mainly associated with high energy delivery and "popping." Reducing the energy limited, though did not eliminate this complication.     

Relation Between Cycle Length, Volume, and Pressure in Type I Atrial Flutter

Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type 1 atrial flutter conversion. Right atrial volume was estimated from B-mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8–1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm² (P = 0.04) during the pressure load induced by negative tilt (+ 3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of -2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm² (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia.