ECG predictors of T wave oversensing in subcutaneous implantable cardioverter defibrillators.

BACKGROUND: T wave oversensing (TWOS) is the commonest cause of inappropriate shocks in subcutaneous implantable cardioverter defibrillators (S-ICDs). We hypothesise that predictors of TWOS can be derived from surface ECG parameters. METHODS: In a cohort of SICD recipients in two UK centres, all patients who had TWOS (study group) were compared to all those who had not (control group). The pre-implant screen was scanned and the R wave, T wave amplitudes, QRS interval, time to peak T wave, QT interval and R:T ratio was measured using digital callipers. Logistic regression was performed to identify ECG predictors of TWOS. RESULTS: One hundred one patients were studied. Six (5.9%) had TWOS. The mean age of the population was 58.6±18years and the median follow-up was 19.5months. By univariate analysis, the predictors of TWOS are QRS duration (140.7±28.7 vs. 105.9±24.6, P=0.007), time to peak T wave (corrected for heart rate, pTc) (403.9±22.6 vs. 347.8±41.4, P=0.006), QTc interval (500.4±41.2 vs. 446.8±49.7, P=0.021), and R:T ratio (3.5±1.1 vs. 9.5±13.2, P=0.034). By multivariate analysis, time to pTc is the most predictive of TWOS. A time to pTc of 390ms cut-off point provided a sensitivity 38.5%, a specificity of 98.9%, a positive predictive value for TWOS of 83.3%, and a negative predictive value of 91.6% (AUC=0.687). CONCLUSION: In this study, time to pTc is the most powerful ECG predictor of TWOS.

Safety and efficacy of multipolar pulmonary vein ablation catheter vs. irrigated radiofrequency ablation for paroxysmal atrial fibrillation: a randomized multicentre trial.

AIMS: The current challenge in atrial fibrillation (AF) treatment is to develop effective, efficient, and safe ablation strategies. This randomized controlled trial assesses the medium-term efficacy of duty-cycled radiofrequency ablation via the circular pulmonary vein ablation catheter (PVAC) vs. conventional electro-anatomically guided wide-area circumferential ablation (WACA). METHODS AND RESULTS: One hundred and eighty-eight patients (mean age 62 ± 12 years, 116 M : 72 F) with paroxysmal AF were prospectively randomized to PVAC or WACA strategies and sequentially followed for 12 months. The primary endpoint was freedom from symptomatic or documented >30 s AF off medications for 7 days at 12 months post-procedure. One hundred and eighty-three patients completed 12 m follow-up. Ninety-four patients underwent PVAC PV isolation with 372 of 376 pulmonary veins (PVs) successfully isolated and all PVs isolated in 92 WACA patients. Three WACA and no PVAC patients developed tamponade. Fifty-six percent of WACA and 60% of PVAC patients were free of AF at 12 months post-procedure (P = ns) with a significant attrition rate from 77 to 78%, respectively, at 6 months. The mean procedure (140 ± 43 vs. 167 ± 42 min, P<0.0001), fluoroscopy (35 ± 16 vs. 42 ± 20 min, P<0.05) times were significantly shorter for PVAC than for WACA. Two patients developed strokes within 72 h of the procedure in the PVAC group, one possibly related directly to PVAC ablation in a high-risk patient and none in the WACA group (P = ns). Two of the 47 patients in the PVAC group who underwent repeat ablation had sub-clinical mild PV stenoses of 25-50% and 1 WACA patient developed delayed severe PV stenosis requiring venoplasty. CONCLUSION: The pulmonary vein ablation catheter is equivalent in efficacy to WACA with reduced procedural and fluoroscopy times. However, there is a risk of thrombo-embolic and pulmonary stenosis complications which needs to be addressed and prospectively monitored. CLINICALTRIALSGOV IDENTIFIER: NCT00678340.

The evaluation of pulmonary vein isolation and wide-area left atrial ablation to treat atrial fibrillation in patients with implanted permanent pacemakers: the Previously Paced Pulmonary Vein Isolation Study.

BACKGROUND: The practise of catheter ablation for atrial fibrillation (AF) is increasing rapidly and is recommended as the treatment of choice in many patient subgroups. At present, the efficacy of this procedure has been assessed by means of electrocardiographic recording, intermittent Holter monitoring and evaluation of patient symptoms. We sought to evaluate the true efficacy of this procedure in patients with sophisticated permanent pacemakers capable of continuous long-term cardiac rhythm monitoring. METHODS: Twenty-five patients (aged 63.7 (9.4), 20 men), seven with persistent AF and 18 with prolonged paroxysmal AF, underwent a mean of 1.7 AF ablation procedures. All the patients had previously been implanted with a pacemaker or atrial defibrillator device. Data were downloaded from the device Holter before catheter ablation and at 2, 4, 6 and 8 months postprocedure(s). The primary outcome measure was AF burden. The secondary outcomes were patient symptom and quality-of-life measures. RESULTS: Initial AF burden was 43.8 (35.5)%. After catheter ablation(s), this was significantly reduced at 2 months to 23.8 (35.4)% (p=0.023), at 4 months to 21.4 (34.1)% (p=0.008), at 6 months to 14.5 (28.1)% (p=0.002) and at 8 months to 15.0 (29.4%) (p=0.003). Only nine (36%) of 25 patients demonstrated no recurrence of arrhythmia during follow-up completion, consistent with a long-term cure. Quality-of-life indices showed significant improvement after ablation. CONCLUSIONS: Catheter ablation for AF significantly improves patient symptoms and reduces AF burden after long-term beat-to-beat monitoring by implanted cardiac pacemaker and defibrillator devices. However, AF recurrence is common after these procedures.

Unlinked anonymous HIV prevalence among New Zealand sexual health clinic attenders: 2005-2006.

This unlinked anonymous study aimed at determining the prevalence of HIV among sexual health clinic attenders having blood samples taken for syphilis and/or hepatitis B serology in six major New Zealand cities over a 12-month period in 2005-2006. Overall, seroprevalence was five per 1000 (47/9439). Among men who have sex with men (MSM), the overall prevalence and that of previously undiagnosed HIV were 44.1 and 20.1 per 1000, respectively. In heterosexual men, the overall prevalence was 1.2 per 1000 and in women 1.4 per 1000. HIV remains to be concentrated among homosexual and bisexual men. Comparison with a previous survey in 1996-1997 suggests an increase in the prevalence of undiagnosed HIV among MSM and also an increase in the number of MSM attending sexual health clinics. The low prevalence of HIV among heterosexuals suggests no extensive spread into the groups identified at risk of other sexually transmitted infections.

High altitude arrhythmias.

OBJECTIVE: To investigate the cause and nature of palpitations occurring at high altitude. METHODS: Implantable loop recorders were inserted subcutaneously in the left pectoral region of 9 healthy male volunteers. Subjects flew to Kathmandu (1,250 m) and then Lukla (2,800 m) before immediately commencing an identical ascent and descent profile to high altitude. The loop recorders were activated with any episode of palpitations and during exercise, rest and sleep. Arterial oxygen saturation was assessed concomitant with device activation. RESULTS: Above 5,000 m all subjects reported palpitations during exercise. All subjects demonstrated sinus tachycardia and marked sinus arrhythmia; one subject demonstrated atrial flutter; one subject had non-conducted p waves, and a further subject had marked ST segment depression. CONCLUSIONS: Significant arrhythmias occur at high altitude. In view of the increased risk of sudden cardiac death at high altitude, and considering that the elderly account for 15% of the 100 million visitors to altitude annually, further investigation is required.

A comparison of intubating conditions in children following induction of anaesthesia with propofol and suxamethonium or propofol and remifentanil.

Sixty ASA 1 and 2 children aged between 2 and 16 years who required tracheal intubation as part of anaesthesia for elective surgery were studied. We evaluated intubating conditions, haemodynamic responses and duration of apnoea following propofol 4 mg.kg-1 combined with either remifentanil 1.25 microg.kg-1 (group R), or suxamethonium 1 mg.kg-1 (group S). Tracheal intubation was graded as excellent, good or poor according to ease of laryngoscopy, vocal cord position, coughing, and jaw relaxation and limb movement. Thirty of group S and 28 of group R children were successfully intubated on the first attempt. Overall, intubation conditions were excellent or good in 26/30 (87%) patients in group S and 20/30 (67%) in group R (p<0.05). Mean apnoea time was 190 s in group S, and 362 s in group R (p<0.001). Heart rate increased in response to suxamethonium (p<0.01) and both systolic and diastolic blood pressure decreased in the remifentanil group (p<0.01).

Sudden cardiac death: opportunities for prevention.

The evidence base for implantable cardioverter-defibrillator (ICD) therapy requires expansion of guidance/indications to allow UK physicians to treat a broader range of patients. The ICD clinical consultees to the National Institute for Health and Clinical Excellence (NICE) review current guidance/guidelines, explain the evidence base, and suggest a UK ICD implantation strategy.

What is the role for revascularisation in patients being considered for ICD therapy?

Patients being considered for ICD therapy are a heterogeneous group.For the vast majority, who have significant left ventricular impairment, it has become common practice to assess their coronary artery anatomy as a surrogate for ischaemia and/or viability. Such patients are therefore frequently under the care of both electrophysiologists and interventionists. The coronary anatomy often raises the dilemma about whether such patients should undergo revascularisation. If the patients present with angina or in the context of an acute myocardial infarct then this decision is clear cut. By contrast, however, a significant proportion of them have no history to suggest ongoing ischaemia or of recent MI. In conventional practice, therefore, there would be no decisive mandate to offer them revascularisation, especially PCI, in the absence of further objective evidence of ischaemia or viability. A review of the literature in our paper does not resolve this dilemma.Further observational data are required to help guide cardiologists as to which of these patients will benefit from revascularisation, since in many cases the coronary anatomy is no surrogate for the presence of ischaemia or viability.

Educational governance for the regulation of industry sponsored continuing medical education in interventional and device based therapies.

The relationship between industry and clinicians in educational programmes needs to be regulated. Industry may be best placed to deliver educational programmes in "craft" related specialties and particularly in areas where device implantation/technology based therapy has a major clinical role. The authors supervise industry sponsored clinical teaching at a purpose built independent teaching facility, and have developed the concept of educational governance to regulate their relationship with their industry sponsor and that concept is presented.

Radiation peak skin dose to risk stratify electrophysiological procedures for deterministic skin damage.

UNLABELLED: Ionising radiation is has the potential to cause harm both by increasing the probability future malignancy (stochastic mechanisms) and by direct physical injury (deterministic mechanisms). Several measures have been developed to quantify radiation exposure during a procedure and cardiologists usually refer to fluoroscopic screening time (FST). FST, however, has limitations for predicting deterministic injury which is directly dependant on peak skin dose (PSD). We compared FST to PSD for a range of interventional cardiac electrophysiology procedures. METHODS: All patients undergoing electrophysiology procedures during a 2-month period in our institution were studied. Demographic details, nature of procedure, FST and PSD were measured. The FST to PSD ratio was calculated and compared between patient and procedural factors. RESULTS: 67 procedures on patients (23 female) with body mass index (BMI) of 28 (SD 5) Kg/m2 were studied. Screening times ranged from 0.2 to 96.6 min (median 11.2). PSD ranged from <0.1 to 1108 mGy (median 141). There was a positive correlation between PSD to FST ratio and BMI (r = 0.59, p < 0.001). The PSD to FST ratio was higher in cardiac resynchronization therapy (CRT) devices than single or dual chamber ICDs (p = 0.002). CONCLUSION: FST is not a reliable predictor of deterministic skin injury and in high-risk procedures such as CRT devices and those on individuals of high BMI PSD should be measured.

Use of tissue microarray for interlaboratory validation of HER2 immunocytochemical and FISH testing.

AIMS: To evaluate the use of tissue microarray (TMA) technology as a validation tool for HER2 testing by both immunocytochemistry (ICC) and fluorescence in situ hybridisation (FISH) in the diagnostic setting. METHODS: TMA constructs from 57 cases of breast cancer were evaluated for HER2 (by ICC and FISH) by two centres. The results were compared. RESULTS: There was a high level of concordance for both ICC and FISH. In five "discrepant" cases only three would have had a potential impact on patient management. CONCLUSIONS: Validation of HER2 analysis in the clinical setting by ICC and FISH is essential. The use of TMAs provides for an economy of scale and would be practical in the setting of interlaboratory and intralaboratory validation. It is suggested that routine HER2 ICC and FISH should continue to be performed in laboratories on whole sections. Following this, TMAs would be constructed for all cases of breast cancer. ICC and FISH would be performed on these to validate the results. The TMAs would be available for circulation to other centres for validation purposes. The standardisation of testing between centres, the potential difficulty of minimum case numbers, and the workload issues surrounding validation would all be facilitated by this approach.

Evaluation of body weight as a predictive factor for transvenous ventricular defibrillation characteristics.

AIMS: To investigate the correlation between body weight and defibrillation threshold (DFT) for transvenous lead systems using a porcine model. METHODS AND RESULTS: Twenty-eight pigs were anaesthetised and DFTs assessed in single and dual coil configurations using a four-reversal binary search method. DFT was correlated with body weight in the RV --> Can and RV --> SVC + Can configurations. A Pearson correlation coefficient and a two-sided p-value were calculated. A positive correlation exists between body weight and DFT in RV --> Can (r=0.66, p<0.000) and RV --> SVC + Can (r=0.44, p=0.018). CONCLUSION: There is a significant correlation between body weight and DFT in swine. This tends to be greater in the two-electrode than in the three-electrode configuration. With these and previous human observations, one may predict a higher DFT in heavy individuals and make appropriate procedural adjustments.