Transseptal puncture for left atrial ablation: risk factors for cardiac tamponade and a proposed causative classification system

Aims

Cardiac tamponade is a high morbidity complication of transseptal puncture (TSP). We examined the associations of TSP‐related cardiac tamponade (TRCT) for all patients undergoing left atrial ablation at our center from 2016 to 2020.

Methods and Results

Patient and procedural variables were extracted retrospectively. Cases of cardiac tamponade were scrutinized to adjudicate TSP culpability. Adjusted multivariate analysis examined predictors of TRCT. A total of 3239 consecutive TSPs were performed; cardiac tamponade occurred in 51 patients (incidence: 1.6%) and was adjudicated as TSP‐related in 35 (incidence: 1.1%; 68.6% of all tamponades). Patients of above‐median age [odds ratio (OR): 2.4 (1.19–4.2), p = .006] and those undergoing re‐do procedures [OR: 1.95 (1.29–3.43, p = .042] were at higher risk of TRCT. Of the operator‐dependent variables, choice of transseptal needle (Endrys vs. Brockenbrough, p > .1) or puncture sheath (Swartz vs. Mullins vs. Agilis vs. Vizigo vs. Cryosheath, all p > .1) did not predict TRCT. Adjusting for operator, equipment and demographics, failure to cross the septum first pass increased TRCT risk [OR: 4.42 (2.45–8.2), p = .001], whilst top quartile operator experience [OR: 0.4 (0.17–0.85), p = .002], transoesophageal echocardiogram [TOE prevalence: 26%, OR: 0.51 (0.11–0.94), p = .023], and use of the SafeSept transseptal guidewire [OR: 0.22 (0.08–0.62), p = .001] reduced TRCT risk. An increase in transseptal guidewire use over time (2016: 15.6%, 2020: 60.2%) correlated with an annual reduction in TRCT (R² = 0.72, p < .001) and was associated with a relative risk reduction of 70%.

Conclusions

During left atrial ablation, the risk of TRCT was reduced by operator experience, TOE‐guidance, and use of a transseptal guidewire, and was increased by patient age, re‐do procedures, and failure to cross the septum first pass.

Outcomes From Pediatric Ablation: A Review of 20 Years of National Data

OBJECTIVES

This study set out to examine outcomes from pediatric supraventricular tachycardia ablations over a 20-year period. This study sought to examine success rates and repeat ablations over time and to evaluate whether modalities such as 3-dimensional (3D) mapping, contact force, and cryotherapy have improved outcomes.

BACKGROUND

Ablation of supraventricular tachycardia in pediatric patients is commonly performed in most congenital heart centers with excellent long-term results.

METHODS

Data were retrieved from the NICOR (National Institute of Clinical Outcomes Research) database in the United Kingdom. Outcomes over time were evaluated, and procedure-related details were compared.

RESULTS

There were 7,069 ablations performed from January 1, 1999, to December 31, 2018, at 10 centers. Overall, ablation success rates were 92% for accessory pathways, 97% for atrioventricular node re-entry tachycardia, and 89% for atrial tachycardia. There was an improvement in procedural success rates over time (p < 0.01). The use of 3D mapping did not alter success or need for repeat ablation but was associated with a higher proportion of lower fluoroscopy cases; 55% of 3D mapping cases used < 5 min of fluoroscopy (p < 0.01). Patients needing a repeat ablation were 341 (12%) for accessory pathways, 128 (7%) for atrioventricular node re-entry tachycardia, and 35 (7%) for atrial tachycardia. Overall, the risk of complete heart block was low (12 patients, <0.01%). The use of cryotherapy was associated with an increased risk of needing a repeat ablation.

CONCLUSIONS

Overall success rates from pediatric ablations are excellent and compare favorably to other registries. Introduction of newer technologies have likely made procedures safer and reduced radiation exposure, but they have not changed success rates or the need for a repeat procedure.

Diagnostic Impact of Repeated Expert Review & Long-Term Follow-Up in Determining Etiology of Idiopathic Cardiac Arrest

Background

Recognizing the etiology of sudden cardiac arrest (SCA) has an enormous impact on the management of victims and their immediate families. A significant proportion of SCA survivors with a structurally normal heart are not offered a diagnosis and there is no clear consensus on the type and duration of follow‐up. We aimed to assess the utility of a multidisciplinary approach in optimizing diagnosis of cardiac arrest etiology during follow‐up.

Methods and Results

We retrospectively assessed 327 consecutive SCA survivors (mean age 61.9±16.2 years, 80% men) who underwent secondary prevention implantable cardioverter defibrillators between May 2015 and November 2018. The initial diagnosis was recorded at the time of admission and follow‐up diagnosis was deduced from subsequent clinic records, investigations, and outcomes of multidisciplinary team meetings. Structural heart disease accounted for 282 (86%) of SCAs. Forty‐five (14%) patients had a structurally normal heart and underwent comprehensive testing and follow‐up (mean duration 93±52 weeks). On initial evaluation, 14/45 (31%) of these received a diagnosis, rising to 29/45 (64%) with serial reviews during follow‐up. Discussion in multidisciplinary team meetings and imaging reassessment accounted for 47% of new diagnoses. No additional diagnoses were made beyond 96 weeks. Nineteen (5.8%) fatalities occurred in the entire cohort, exclusively in patients with structural heart disease.

Conclusions

Systematic comprehensive testing combined with multidisciplinary expert team review of SCA survivors without structural heart disease improves the yield and time to diagnosis compared with previously published studies. This approach has positive implications in the management of SCA survivors and their families.

A Primary Prevention Clinical Risk Score Model for Patients With Brugada Syndrome (BRUGADA-RISK)

OBJECTIVES

The goal of this study was to develop a risk score model for patients with Brugada syndrome (BrS).

BACKGROUND

Risk stratification in BrS is a significant challenge due to the low event rates and conflicting evidence.

METHODS

A multicenter international cohort of patients with BrS and no previous cardiac arrest was used to evaluate the role of 16 proposed clinical or electrocardiogram (ECG) markers in predicting ventricular arrhythmias (VAs)/sudden cardiac death (SCD) during follow-up. Predictive markers were incorporated into a risk score model, and this model was validated by using out-of-sample cross-validation.

RESULTS

A total of 1,110 patients with BrS from 16 centers in 8 countries were included (mean age 51.8 ± 13.6 years; 71.8% male). Median follow-up was 5.33 years; 114 patients had VA/SCD (10.3%) with an annual event rate of 1.5%. Of the 16 proposed risk factors, probable arrhythmia-related syncope (hazard ratio [HR]: 3.71; p < 0.001), spontaneous type 1 ECG (HR: 3.80; p < 0.001), early repolarization (HR: 3.42; p < 0.001), and a type 1 Brugada ECG pattern in peripheral leads (HR: 2.33; p < 0.001) were associated with a higher risk of VA/SCD. A risk score model incorporating these factors revealed a sensitivity of 71.2% (95% confidence interval: 61.5% to 84.6%) and a specificity of 80.2% (95% confidence interval: 75.7% to 82.3%) in predicting VA/SCD at 5 years. Calibration plots showed a mean prediction error of 1.2%. The model was effectively validated by using out-of-sample cross-validation according to country.

CONCLUSIONS

This multicenter study identified 4 risk factors for VA/SCD in a primary prevention BrS population. A risk score model was generated to quantify risk of VA/SCD in BrS and inform implantable cardioverter-defibrillator prescription.

Prolonged action potential duration and dynamic transmural action potential duration heterogeneity underlie vulnerability to ventricular tachycardia in patients undergoing ventricular tachycardia ablation

Aims

Differences of action potential duration (APD) in regions of myocardial scar and their borderzones are poorly defined in the intact human heart. Heterogeneities in APD may play an important role in the generation of ventricular tachycardia (VT) by creating regions of functional block. We aimed to investigate the transmural and planar differences of APD in patients admitted for VT ablation.

Methods and results

Six patients (median age 53 years, five male); (median ejection fraction 35%), were studied. Endocardial (Endo) and epicardial (Epi) 3D electroanatomic mapping was performed. A bipolar voltage of <0.5 mV was defined as dense scar, 0.5–1.5 mV as scar borderzone, and >1.5 mV as normal. Decapolar catheters were positioned transmurally across the scar borderzone to assess differences of APD and repolarization time (RT) during restitution pacing from Endo and Epi. Epi APD was 173 ms in normal tissue vs. 187 ms at scar borderzone and 210 ms in dense scar (P < 0.001). Endocardial APD was 210 ms in normal tissue vs. 222 ms in the scar borderzone and 238 ms in dense scar (P < 0.01). This resulted in significant transmural RT dispersion (ΔRT 22 ms across dense transmural scar vs. 5 ms in normal transmural tissue, P < 0.001), dependent on the scar characteristics in the Endo and Epi, and the pacing site.

Conclusion

Areas of myocardial scar have prolonged APD compared with normal tissue. Heterogeneity of regional transmural and planar APD result in localized dispersion of repolarization, which may play an important role in initiating VT.

Outcome of ACHD patients with non-inducible versus inducible IART undergoing cavo-tricuspid isthmus ablation: the role of empiric ablation

PURPOSE

Catheter ablation for supraventricular tachycardia (SVT) in adults with congenital heart disease (ACHD) is an important therapeutic option. Cavo-tricuspid isthmus (CTI)-dependent intraatrial re-entrant tachycardia (IART) is common. However, induction of sustained tachycardia at the time of ablation is not always possible. We hypothesised that performing an empiric CTI line in case of non-inducibility leads to good outcomes. Long-term outcomes of empiric versus entrained CTI ablation in ACHD patients were examined.

METHODS

Retrospective, single-centre, case-control study over 7 years. Arrhythmia-free survival after empiric versus entrained CTI ablation was compared.

RESULTS

Eighty-seven CTI ablations were performed in 85 ACHD patients between 2010 and 2017. The mean age of the cohort was 43 years and 48% were male. Underlying aetiology included ASD (31%), VSD (11.4%), AVSD (9.1%), AVR (4.8%), Fallot's (18.4%), Ebstein's (2.3%), Fontan's palliation (9.2%) and atrial switch (13.8%). CTI-dependent IART was entrained in 59 patients whereas it was non-inducible in 28. The latter had an empiric CTI ablation. Forty-three percent of procedures were performed under general anaesthesia. There were no reported procedural complications. There was no significant difference in the mean procedure or fluoroscopy times between the groups (empiric vs entrained CTI; 169.1 vs 183.3 and 28.1 vs 19.9 min). Arrhythmia-free survival was 64.3% versus 72.8% (p value 0.44) in the empiric and entrained groups at 21 months follow-up.

CONCLUSIONS

Long-term outcomes after empiric and entrained CTI ablation for IART in ACHD patients are comparable. This is a safe and effective therapeutic option. In the case of non-inducibility of IART, an empiric CTI line should be considered in this cohort.

Trends in implantable cardioverter defibrillator and cardiac resynchronisation therapy lead parameters for patients with arrhythmogenic and dilated cardiomyopathies

Background

Implantable cardioverter-defibrillator (ICD) lead parameters may deteriorate due to right ventricular (RV) disease such as arrhythmogenic right ventricular cardiomyopathy (ARVC), with implications for safe delivery of therapies. We compared ICD and CRT-D (cardiac resynchronisation therapy-defibrillator) lead parameters in patients with ARVC and dilated cardiomyopathy (DCM).

Methods

RV lead sensing (R wave amplitude) and pacing (threshold and amplitude-pulse width product (APWP)), left ventricular (LV) pacing (APWP), and imaging parameter trends were assessed in 18 patients with ARVC and 18 with DCM.

Results

R wave amplitude did not change significantly over time in either group (over 5 years, ARVC -0.4 mV, 95% CI -3.8–3.0 mV; DCM -1.8 mV, 95% CI -5.0–1.3 mV). Within ARVC group, divergent trends were seen according to lead position. DCM patients experienced an increase in RV lead threshold (+1.1 V over 5 years, 95% CI + 0.5 to +1.7 V) and RV APWP (+0.48 Vms over 5 years, 95% CI + 0.24 to +0.71 Vms); ARVC patients had no change. ARVC patients had a higher LVEF at baseline than DCM patients (52 vs 20%, p < 0.001), though LVEF decreased over time for the former, while increasing for the latter. TAPSE did not change over time for ARVC patients.

Conclusions

Lead parameters in ARVC patients were stable over medium-term follow up. In DCM patients, RV lead threshold and RV and LV APWP increased over time. These differential responses for DCM and ARVC were not explained by imaging indices, and may reflect distinct patterns of disease progression.

Assessment of a conduction-repolarisation metric to predict Arrhythmogenesis in right ventricular disorders

BACKGROUND

The re-entry vulnerability index (RVI) is a recently proposed activation-repolarization metric designed to quantify tissue susceptibility to re-entry. This study aimed to test feasibility of an RVI-based algorithm to predict the earliest endocardial activation site of ventricular tachycardia (VT) during electrophysiological studies and occurrence of haemodynamically significant ventricular arrhythmias in follow-up.

METHODS

Patients with Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) (n = 11), Brugada Syndrome (BrS) (n = 13) and focal RV outflow tract VT (n = 9) underwent programmed stimulation with unipolar electrograms recorded from a non-contact array in the RV.

RESULTS

Lowest values of RVI co-localised with VT earliest activation site in ARVC/BrS but not in focal VT. The distance between region of lowest RVI and site of VT earliest site (Dmin) was lower in ARVC/BrS than in focal VT (6.8 ± 6.7 mm vs 26.9 ± 13.3 mm, p = 0.005). ARVC/BrS patients with inducible VT had lower Global-RVI (RVIG) than those who were non-inducible (-54.9 ± 13.0 ms vs -35.9 ± 8.6 ms, p = 0.005) or those with focal VT (-30.6 ± 11.5 ms, p = 0.001). Patients were followed up for 112 ± 19 months. Those with clinical VT events had lower Global-RVI than both ARVC and BrS patients without VT (-54.5 ± 13.5 ms vs -36.2 ± 8.8 ms, p = 0.007) and focal VT patients (-30.6 ± 11.5 ms, p = 0.002).

CONCLUSIONS

RVI reliably identifies the earliest RV endocardial activation site of VT in BrS and ARVC but not focal ventricular arrhythmias and predicts the incidence of haemodynamically significant arrhythmias. Therefore, RVI may be of value in predicting VT exit sites and hence targeting of re-entrant arrhythmias.

Medium-term outcomes of idiopathic ventricular fibrillation survivors and family screening: a multicentre experience

Aims

Early repolarization (ER) has been linked to poorer outcomes in idiopathic ventricular fibrillation (IVF). The role of family screening in IVF is not clear. Our aim was to review predictors for poorer outcomes and evaluate the role of family screening in IVF.

Methods and results

This was a retrospective multicentre cohort study including all patients diagnosed with IVF. Data were collected on baseline characteristics, ECG findings, and recurrence of ventricular arrhythmia (VA) during follow-up. Electrocardiogram findings were reviewed in first-degree relatives that were screened. A total of 66 patients were included with male predominance (42/66, 64%) and Caucasian ethnicity (47/66, 71%). Mean age at cardiac arrest was 38 years ± 11. Thirty-one patients had ER (47%) predominantly with J-point amplitude ≥2 mm and horizontal ST segments (18/31, 58%). Recurrent VA was seen in 13 patients (20%). Horizontal ST segments were associated with increased rates of VA recurrence (OR 11, 95% CI 2.7-43.7; P = 0.0007). Early repolarization was seen in 20% of the 72 first-degree relatives and was more common if the proband had persistent ER pattern (OR 10.7, 95% CI 2.2-51.5; P = 0.003).

Conclusion

Ventricular arrhythmia recurrence was lower than previously reported. Early repolarization was common in this IVF cohort, and horizontal ST segments were suggestive predictor for poorer outcomes. Persistent ER in proband was associated with ER in first-degree relatives. With better understanding of its predictive value and the relationship to IVF, this information could potentially be used to guide family screening and identify new mutations using family members with persistent ER.

Ventricular stimulus site influences dynamic dispersion of repolarization in the intact human heart

Spatial variation of restitution in relation to varying stimulus site is poorly defined in the intact human heart. Repolarization gradients were shown to be dependent on site of activation with epicardial stimulation promoting significant transmural gradients. Steep restitution slopes were predominant in the normal ventricle.

The spatial variation in restitution properties in relation to varying stimulus site is poorly defined. This study aimed to investigate the effect of varying stimulus site on apicobasal and transmural activation time (AT), action potential duration (APD) and repolarization time (RT) during restitution studies in the intact human heart. Ten patients with structurally normal hearts, undergoing clinical electrophysiology studies, were enrolled. Decapolar catheters were placed apex to base in the endocardial right ventricle (RV_endo) and left ventricle (LV_endo), and an LV branch of the coronary sinus (LV_epi) for transmural recording. S1–S2 restitution protocols were performed pacing RV_endo apex, LV_endo base, and LV_epi base. Overall, 725 restitution curves were analyzed, 74% of slopes had a maximum slope of activation recovery interval (ARI) restitution (S_max) > 1 (P < 0.001); mean S_max = 1.76. APD was shorter in the LV_epi compared with LV_endo, regardless of pacing site (30-ms difference during RV_endo pacing, 25-ms during LV_endo, and 48-ms during LV_epi; 50th quantile, P < 0.01). Basal LV_epi pacing resulted in a significant transmural gradient of RT (77 ms, 50th quantile: P < 0.01), due to loss of negative transmural AT-APD coupling (mean slope 0.63 ± 0.3). No significant transmural gradient in RT was demonstrated during endocardial RV or LV pacing, with preserved negative transmural AT-APD coupling (mean slope −1.36 ± 1.9 and −0.71 ± 0.4, respectively). Steep ARI restitution slopes predominate in the normal ventricle and dynamic ARI; RT gradients exist that are modulated by the site of activation. Epicardial stimulation to initiate ventricular activation promotes significant transmural gradients of repolarization that could be proarrhythmic.

Diagnostic yield of molecular autopsy in patients with sudden arrhythmic death syndrome using targeted exome sequencing

AIMS

The targeted genetic screening of Sudden Arrhythmic Death Syndrome (SADS) probands in a molecular autopsy has a diagnostic yield of up to 35%. Exome sequencing has the potential to improve this yield. The primary aim of this study is to examine the feasibility and diagnostic utility of targeted exome screening in SADS victims, utilizing familial clinical screening whenever possible.

METHODS AND RESULTS

To determine the feasibility and diagnostic yield of targeted exome sequencing deoxyribonucleic acid (DNA) was isolated from 59 SADS victims (mean age 25 years, range 1-51 years). Targeted exome sequencing of 135 genes associated with cardiomyopathies and ion channelopathies was performed on the Illumina HiSeq2000 platform. Non-synonymous, loss-of-function, and splice-site variants with a minor allele frequency <0.02% in the NHLBI exome sequencing project and an internal set of control exomes were prioritized for analysis followed by <0.5% frequency threshold secondary analysis. First-degree relatives were offered clinical screening for inherited cardiac conditions. Seven probands (12%) carried very rare (<0.02%) or novel non-sense candidate mutations and 10 probands (17%) had previously published rare (0.02-0.5%) candidate mutations-a total yield of 29%. Co-segregation fully confirmed two private SCN5A Na channel mutations. Variants of unknown significance were detected in a further 34% of probands.

CONCLUSION

Molecular autopsy using targeted exome sequencing has a relatively low diagnostic yield of very rare potentially disease causing mutations. Candidate pathogenic variants with a higher frequency in control populations are relatively common and should be interpreted with caution.

Safe use of MRI in people with cardiac implantable electronic devices

MR scanning in patients with cardiac implantable electronic devices (CIEDs) was formerly felt to be contraindicated, but an increasing number of patients have an implanted MR conditional device, allowing them to safely undergo MR scanning, provided the manufacturer's guidance is adhered to. In addition, some patients with non-MR conditional devices may undergo MR scanning if no other imaging modality is deemed suitable and there is a clear clinical indication for scanning which outweighs the potential risk. The following guidance has been formulated by the British Heart Rhythm Society and endorsed by the British Cardiovascular Society and others. It describes protocols that should be followed for patients with CIEDs undergoing MR scanning. The recommendations, principles and conclusions are supported by the Royal College of Radiologists.

A systematic review of ICD complications in randomised controlled trials versus registries: is our 'real-world' data an underestimation?

Implantable cardioverter defibrillator (ICD) implantation carries a significant risk of complications, however published estimates appear inconsistent. We aimed to present a contemporary systematic review using meta-analysis methods of ICD complications in randomised controlled trials (RCTs) and compare it to recent data from the largest international ICD registry, the US National Cardiovascular Data Registry (NCDR).

PubMed was searched for any RCTs involving ICD implantation published 1999–2013; 18 were identified for analysis including 6433 patients, mean follow-up 3 months–5.6 years. Exclusion criteria were studies of children, hypertrophic cardiomyopathy, congenital heart disease, resynchronisation therapy and generator changes.

Total pooled complication rate from the RCTs (excluding inappropriate shocks) was 9.1%, including displacement 3.1%, pneumothorax 1.1% and haematoma 1.2%. Infection rate was 1.5%.There were no predictors of complications but longer follow-up showed a trend to higher complication rates (p=0.07). In contrast, data from the NCDR ICD, reporting on 356 515 implants (2006–2010) showed a statistically significant threefold lower total major complication rate of 3.08% with lead displacement 1.02%, haematoma 0.86% and pneumothorax 0.44%.

The overall ICD complication rate in our meta-analysis is 9.1% over 16 months. The ICD complication reported in the NCDR ICD registry is significantly lower despite a similar population. This may reflect under-reporting of complications in registries. Reporting of ICD complications in RCTs and registries is very variable and there is a need to standardise classification of complications internationally.

Is CRT pro-arrhythmic? A comparative analysis of the occurrence of ventricular arrhythmias between patients implanted with CRTs and ICDs

Aim and Hypothesis: Despite the proven symptomatic and mortality benefit of cardiac resynchronization therapy (CRT), there is anecdotal evidence it may be pro-arrhythmic in some patients. We aimed to identify if there were significant differences in the incidence of ventricular arrhythmias (VAs) in patients undergoing CRT-D and implantable cardioverter-defibrillators (ICD) implantation for primary prevention indication. We hypothesized that CRT is unlikely to be pro-arrhythmic based on the positive mortality and morbidity data from large randomized trials.

Methods and Results: A retrospective analysis of device therapies for VA in a primary prevention device cohort was performed. Patients with ischemic (IHD) and non-ischemic (DCM) cardiomyopathy and ICD or CRT+ICD devices (CRT-D) implanted between 2005 and 2007 without prior history of sustained VA were included for analysis. VA episodes were identified from stored electrograms and defined as sustained (VT/VF) if therapy [anti-tachycardia pacing (ATP) or shocks] was delivered or non-sustained (NSVT) if not. Of a total of 180 patients, 117 (68% male) were in the CRT-D group, 42% IHD, ejection fraction (EF) 24.5 ± 8.2% and mean follow-up 23.9 ± 9.8 months. 63 patients (84% male) were in the ICD group, 60% IHD, EF 27.7 ± 7.2% and mean follow-up 24.6 ± 10.8 months. Overall, there was no significant difference in the incidence of VA (35.0 vs. 38.1%, p = 0.74), sustained VT (21.3 vs. 28.5%, p = 0.36) or NSVT (12.8 vs. 9.5%, p = 0.63) and no significant difference in type of therapy received for VT/VF: ATP (68 vs. 66.6%, p = 0.73) and shocks (32 vs. 33.3%, p = 0.71) between the CRT-D and ICD groups, respectively.

Conclusion: In patients with cardiomyopathy receiving CRT-D and ICDs for primary prophylaxis, there was no significant difference in the incidence of VA. From this single center retrospective analysis, there is no evidence to support cardiac resynchronization causing pro-arrhythmia.

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.

ClinicalTrials.gov Identifier

NCT00678340.

The use of a novel nitinol guidewire to facilitate transseptal puncture and left atrial catheterization for catheter ablation procedures

AIMS

An increasing number of transseptal punctures (TSPs) are performed worldwide for atrial ablations. Transseptal punctures can be complex and can be associated with potentially life threatening complications. The purpose of the study was to evaluate the safety and efficacy of a novel transseptal guidewire (TSGW) designed to facilitate TSPs.

METHODS AND RESULTS

Transseptal punctures were performed using a SafeSept TSGW passed through a standard TSP apparatus. Transseptal punctures were performed by standard technique with additional use of a TSGW allowing probing of the interatrial septum without needle exposure and penetration of the fossa into the left atrium (LA). Transseptal puncture using the TSGW was performed in 210 patients. Left atrial access was achieved successfully in 205 of 210 patients (97.6%) and in 96.3% of patients undergoing repeat TSP. Left atrial access was achieved with the first pass in 81.2% (mean 1.4 ± 0.9 passes, range 1-6) using the TSGW. No serious complications were attributable to the use of the TSGW, even in cases of failed TSP.

CONCLUSIONS

The TSGW is associated with a high success rate for TSP and may be a useful alternative to transoesophageal or intracardiac echocardiogram-guided TSP.

Haemolytic crisis associated with ragwort poisoning and rail chewing in two thoroughbred fillies

Events leading to the deaths of two fillies at pasture are described. Pasture hay containing the flowering stages of Senecio jacobea (ragwort) had been fed three to four months earlier. Paddocks were subdivided with posts and rails treated with copper chrome arsenate. Six horses on the property chewed rails spasmodically. Both fillies presented with haemoglobinurea. Values in liver of 83 mg Cu kg and kidney 35 mg Cu kg wet weight and serum 1.4 mg Cu/l together with histophathology of seneciosis support a sequence of ragwort poisoning followed by copper accumulation in liver and kidney terminating in a haemolytic crisis. The source of copper appeared to he from wood containing concentrations of copper of 0.17% at the core and 1.68% in shavings from surface of treated timber.

Resolution of dyssynchronous left ventricular failure via cardiac resynchronization and subsequent radiofrequency ablation in an infant with pre-excitation

Ventricular pre-excitation causing reversible left ventricular (LV) systolic dysfunction has been reported in adults and children. We describe severe heart failure secondary to ventricular pre-excitation in a 3-month-old girl who presented with echocardiographic evidence of marked intraventricular dyssynchrony. The patient was initially considered for transplantation, but dual chamber left atrioventricular epicardial pacing initiated at 4.5 months of age resulted in a marked clinical and echocardiographic improvement. Five years later, successful radiofrequency ablation resulted in loss of pre-excitation and reversal of LV dyssynchrony, thus allowing pacemaker explantation. To our knowledge, this is one of very few reported cases of pre-excitation-induced cardiomyopathy affecting a young infant and the only case palliated with resynchronization pacing.

Incidence of left atrial thrombus prior to atrial fibrillation ablation: is pre-procedural transoesophageal echocardiography mandatory?

AIMS

The exact role of transoesphageal echo (TOE) prior to atrial fibrillation (AF) ablation remains unclear. This study examines the incidence and predictors of left atrial (LA) thrombus in patients undergoing AF ablation.

METHODS AND RESULTS

Patients were treated with warfarin for at least 4 weeks prior to ablation. This was substituted with therapeutic dalteparin 3 days before the procedure. All patients underwent TOE to exclude LA thrombus. Six clinical risk factors for thrombus were defined, known to be risk factors for stroke in AF: age>75, diabetes, hypertension, valve disease, prior stroke, or transient ischaemic attack and cardiomyopathy. A total of 635 procedures were performed. The incidence of thrombus was 12/635 (1.9%) despite therapeutic anti-coagulation. Patients with thrombus had larger LA diameter, mean 50.6+/-6.2 mm vs. 44.2+/-7.6 (P=0.006). In univariate analysis, persistent AF [odds ratio (OR)=10.4 with 95% CI 1.8-19.1], hypertension [OR=11.7 with 95% CI 2.5-54.1], age>75 (OR=4.5 with 95% CI 1.2-17.2), and cardiomyopathy (OR 5.9 with 95% CI 1.8-19.1) were significantly associated with thrombus. In multivariate analysis, hypertension (OR=14.2 with 95% CI 2.6-77.5), age>75 (OR=8.1, 95% CI 1.5-44.9), and cardiomyopathy (OR=10.5 with 95% CI 2.6-77.5) were independently associated with thrombus. There was no thrombus in patients without clinical risk factors.

CONCLUSION

In patients presenting for AF ablation, LA thrombus is only seen in those with clinical risk factors. TOE is indicated in this group but may be unnecessary in patients without clinical risk factors.

High-density substrate mapping in Brugada syndrome: combined role of conduction and repolarization heterogeneities in arrhythmogenesis

BACKGROUND

Two principal mechanisms are thought to be responsible for Brugada syndrome (BS): (1) right ventricular (RV) conduction delay and (2) RV subepicardial action potential shortening. This in vivo high-density mapping study evaluated the conduction and repolarization properties of the RV in BS subjects.

METHODS AND RESULTS

A noncontact mapping array was positioned in the RV of 18 BS patients and 20 controls. Using a standard S(1)-S(2) protocol, restitution curves of local activation time and activation recovery interval were constructed to determine local maximal restitution slopes. Significant regional conduction delays in the anterolateral free wall of the RV outflow tract of BS patients were identified. The mean increase in delay was 3-fold greater in this region than in control (P=0<0.001). Local activation gradient was also maximally reduced in this area: 0.33+/-0.1 (mean+/-SD) mm/ms in BS patients versus 0.51+/-0.15 mm/ms in controls (P<0.0005). The uniformity of wavefront propagation as measured by the square of the correlation coefficient, r(2), was greater in BS patients versus controls (0.94+/-0.04 versus 0.89+/-0.09 [mean+/-SD]; P<0.05). The odds ratio of BS hearts having any RV segment with maximal restitution slope >1 was 3.86 versus controls. Five episodes of provoked ventricular tachycardia arose from wave breaks originating from RV outflow tract slow-conduction zones in 5 BS patients.

CONCLUSIONS

Marked regional endocardial conduction delay and heterogeneities in repolarization exist in BS. Wave break in areas of maximal conduction delay appears to be critical in the initiation and maintenance of ventricular tachycardia. These data indicate that further studies of mapping BS to identify slow-conduction zones should be considered to determine their role in spontaneous ventricular arrhythmias.

A novel algorithm for determining endocardial VT exit site from 12-lead surface ECG characteristics in human, infarct-related ventricular tachycardia

INTRODUCTION

Characteristics of the 12-lead ECG during VT are used to guide initial placement of mapping catheters in endocardial ventricular tachycardia (VT) ablation. Previously constructed algorithms for guidance in human infarct-related VT are limited to patients known to have anterior or inferior infarcts only. We hypothesized that 12-lead ECG characteristics could be used to determine VT exit site in patients with all types of infarction of unknown location.

METHODS AND RESULTS

From noncontact activation maps of 121 LV VT in 51 patients undergoing catheter ablation, VT exit sites were determined and correlated with ECG characteristics according to bundle branch block configuration, limb lead polarity and patterns of precordial R-wave transition. Eight ECG patterns were identified that accounted for 71% of all VT and gave a positive predictive value (PPV) > or =70% using the first two criteria. No correlation was found with patterns of R-wave transition. Using these criteria an algorithm was developed, which was then applied prospectively and blinded to a further 17 VT in 11 patients. Of the 15 VT (88%) to which the algorithm predicted an exit site location (with a PPV > or =70%), 14 VT (93%) were correctly predicted by the algorithm.

CONCLUSION

This algorithm can be used to predict endocardial LV VT exit site location in patients undergoing catheter ablation of VT without knowledge of or reference to infarct location, and can be applied to patients with posterior and/or multiple sites of infarction.

Comparison of Noncontact and Electroanatomic Mapping to Identify Scar and Arrhythmia Late After the Fontan Procedure

Background— The right atrium late after the Fontan procedure is characterized by multiple complex arrhythmia circuits. We performed simultaneous electroanatomic and noncontact mapping to assess the accuracy of both systems to identify scar and arrhythmia.

Methods and Results— Mapping was performed in 26 patients aged 26.8±8.9 years, 18.7±4.4 years after Fontan surgery. The area and site of abnormal endocardium defined by electroanatomic mapping (bipolar contact electrogram <0.5 mV) were compared with those defined by noncontact mapping during sinus rhythm and by dynamic substrate mapping. Contact and reconstructed unipolar electrograms at a known distance from the multielectrode array, recorded by the noncontact system simultaneously at 452 endocardial sites, were compared for morphological cross correlation, timing difference, and amplitude. Mapping of arrhythmias was performed with both systems when possible. The median patient abnormal endocardium as defined by electroanatomic mapping covered 38.0% (range 16.7% to 97.8%) of the right atrial surface area, as opposed to 60.9% (range 21.3% to 98.5%) defined by noncontact mapping during sinus rhythm and 11.9% (range 0.4% to 67.3%) by dynamic substrate mapping. A significant decrease in electrogram cross correlation ( P =0.003), timing ( P =0.012), and amplitude ( P =0.003) of reconstructed electrograms, but not of contact electrograms ( P =0.742), was seen at endocardial sites >40 mm from the multielectrode array. Successful arrhythmia mapping by electroanatomic versus noncontact mapping was superior in 15 patients (58%), the same in 6 (23%), and inferior in 5 (19%; P =0.044).

Conclusions— Electroanatomic mapping is the superior modality for arrhythmia mapping late after the Fontan procedure. Noncontact mapping is limited by a significant reduction in reconstructed electrogram correlation, timing, and amplitude >40 mm from the multielectrode array and cannot accurately define areas of scar and low-voltage endocardium.

Right atrial angiography facilitates transseptal puncture for complex ablation in patients with unusual anatomy

OBJECTIVE

The number of transseptal punctures performed worldwide has increased exponentially with the development of ablation therapies for atrial arrhythmias. Safe access into the left atrium in these procedures is often complicated by abnormal anatomy. We assessed the potential of right atrial angiography to facilitate transseptal puncture for atrial ablation.

METHODS AND RESULTS

We examined all transseptal punctures performed for complex left atrial ablation in our centre over a 29-month period. In cases where conventional transseptal techniques failed, we performed orthogonal right atrial angiography to define cardiac anatomy and orientation. During the study period, 255 transseptal procedures were performed. Of these, 16 cases were complicated by distorted atrial anatomy, extreme cardiac rotation or unexpected location of the atria in relation to the diaphragm, preventing left atrial access using conventional fluoroscopy. The application of right atrial angiography facilitated successful transseptal puncture in all patients when use of conventional mapping catheters and fluoroscopy proved unhelpful. There were no complications relating to right atrial angiography.

CONCLUSION

These cases highlight a number of difficulties encountered when performing transseptal punctures. Previously reported adjunctive techniques require specialised equipment, general anaesthesia or multiple catheters that may be unavailable or impede the procedure. Right atrial angiography is a simple and safe adjunct to conventional techniques to facilitate complex transseptal procedures.

Delayed paced ventricular activation in the long QT syndrome is associated with ventricular fibrillation

BACKGROUND

LQTS may cause sudden cardiac death (SCD), but the mechanisms linking gene mutations to ventricular fibrillation (VF) are unclear.

OBJECTIVE

To determine whether ventricular activation delays in congenital long QT syndrome (LQTS) are associated with VF and to describe these delays clinically by measuring activation through ventricular myocardium after a premature extrastimulus.

METHODS

Forty-six patients with LQTS, including 16 with VF (LQTS VF) were investigated, and the results were compared with those from 24 patients with hypertrophic cardiomyopathy and VF (HCM VF). Electrograms in response to premature stimuli were analyzed for increases in electrogram duration (DeltaED) and the S1S2 coupling intervals at which electrogram latency starts to increase (S1S2(delay)). Two piecewise continuous straight line segments were fitted to the last electrogram deflection as a function of S1S2 interval in the LQTS and HCM VF populations, and the difference in their gradient (alpha) was taken as an index of the abruptness of the onset of this delay.

RESULTS

Thirteen LQTS VF and six LQTS non-VF patients had values of DeltaED and S1S2(delay) comparable to those in HCM VF patients, while the remainder (three LQTS VF and 24 LQTS non-VF) had lower values (P<.001). There was only a weak correlation between delay and the corrected QT interval. The HCM and LQTS VF patients could be separated by the value of alpha (P<.01), with the LQTS patients having a more abrupt onset of delay.

CONCLUSIONS

Large delays in ventricular activation after an extrastimulus occur in patients with the LQTS, especially those with VF. The change in delay is abrupt in the LQTS, indicating sudden block to activation creating a dynamic substrate for arrhythmogenesis.

Arrhythmogenic right ventricular cardiomyopathy: clinical presentation, diagnosis, and management

Arrhythmogenic right ventricular cardiomyopathy, also known as right ventricular dysplasia, is a genetically determined heart muscle disease associated with arrhythmia, heart failure, and sudden death. Autosomal dominant inheritance is typical. The identification of causative mutations in cell adhesion proteins has shed new light on its pathogenesis. Fibrofatty replacement of the myocardium, the hallmark pathologic feature, may be a response to injury caused by myocyte detachment. Sudden death is often the first manifestation in probands, emphasizing the importance of evaluating asymptomatic relatives for the disease. Standardized guidelines facilitate the clinical diagnosis of right ventricular dysplasia. However, familial studies have highlighted the need to broaden the diagnostic criteria, which are highly specific but lack sensitivity for early disease. Modifications have been proposed for the diagnosis of right ventricular dysplasia in relatives. Early right ventricular dysplasia is characterized by a "concealed phase" in which electrocardiographic and imaging abnormalities are often absent, but patients may nonetheless be at risk for arrhythmic events. Detection at this stage remains a clinical challenge, underscoring the potential value of mutation analysis in identifying affected persons. Serial evaluation of patients with suspected right ventricular dysplasia is recommended as clinical features may develop during the follow-up period. The onset of symptoms such as palpitation or syncope may herald an active phase of a previously quiescent disease, during which patients are at increased risk for sudden death. Greater awareness of right ventricular dysplasia among physicians and judicious use of implantable cardioverter-defibrillators may help to prevent unnecessary deaths.

Coronary angiography in the fully anticoagulated patient: the transradial route is successful and safe

The radial approach to coronary angiography is intuitively attractive for fully anticoagulated patients (INR > 2) but no data exist concerning efficacy or safety of this procedure. The consensus view is that the femoral approach is contraindicated in fully anticoagulated patients, and though some operators undertake femoral catheterization in such patients and use closure devices, there are no data to suggest that it is safe to do so. At our institution, the radial approach for coronary angiography is reserved for patients in whom there is a relative contraindication to the femoral route. We have undertaken over 600 radial coronary angiograms in such patients since 1996, 66 of whom underwent transradial catheterization specifically because of anticoagulation status (INR > 2). Thirty-eight patients (58%) were male, average age 67 +/- 11 years. All 66 patients had an INR > 2 but < 4.5. The approach was left radial in 26 (39%), right radial in the remainder; sheath size was 4 Fr in 4 (6%), 5 Fr in 13 (20%), and 6 Fr in 49 (74%). Seven operators in total were involved, though two operators undertook the majority of cases (47; 71%). Success rate was 97%, with no failure of access, and only one minor postprocedural hemorrhage. Failures were due to radial artery atherosclerosis (1) and subclavian tortuosity (1). The radial approach to coronary angiography is safe and to be recommended in the fully anticoagulated patient.

Transradial coronary angiography in patients with contraindications to the femoral approach: An analysis of 500 cases

The transradial approach to coronary angiography is considered by some to be a route of choice, by others to be a route that should be used only where there are relative contraindications to the femoral approach. We present the largest series to date of patients in whom transradial coronary angiography was undertaken specifically because of contraindications to the femoral approach. Since 1995, patients at this cardiothoracic center have been considered for a transradial approach to coronary angiography if there were relative contraindications to the femoral route. Data from 500 patients was prospectively collected. Patients were aged 66 +/- 9 years; 72% were male. Indications for the radial approach included peripheral vascular disease (305), therapeutic anticoagulation (77), musculoskeletal (59), and morbid obesity (32). Sixty-eight patients (14%) required a radial procedure following a failed femoral approach. Access was right radial 291 (58%), left radial 209 (42%). Eighteen operators were involved, but two operators undertook 355 (71%) of the cases. Catheter gauge was 6 Fr (n = 243; 49%), 5 Fr (219; 43%), and 4 Fr (29; 6%). The procedure was successful in 463 cases [92.6%; 88.2% for nonmajority vs. 94.4% (P < 0.05) for the two majority operators]. Success in males (93.6%) significantly exceeded that in females (90.1%; P < 0.05). In-catheter-laboratory duration was 45 +/- 17 min; fluoroscopy time, 7.5 +/- 6 min; radiation dose, 40 +/- 23 CGy. The procedure was without incident in 408 cases (82%). There were procedural difficulties in 18% of cases, including radial artery spasm (12%) and vasovagal response (5%). The incidence was higher with 6 Fr catheters (23%) than with 5/4 Fr (15%; P < 0.05). Major procedural complications occurred in three cases: brachial artery dissection in one and cardiac arrest in two. Postprocedure major vascular complications numbered three: claudicant pain on handgrip in one, ischemic index finger (with subsequent terminal phalanx amputation due to osteomyelitis) in one, and ischemic hand for 4 hr in one. Patients with contraindications to the femoral approach form a high-risk group. In these patients, transradial cardiac catheterization can be performed successfully and with a low risk of major complications. Minor adverse features remain frequent, occurring in one in five cases, though difficulties are minimized both with increasing operator experience and smaller sheath diameter.

Catheter cryoablation of supraventricular arrhythmias: a painless alternative to radiofrequency energy

Cryothermy has potential advantages over RF energy for catheter ablation, including reversibility of lesion formation, catheter stability, and less procedural discomfort. Cryoablation procedures were performed in 14 patients with atrioventricular reentrant tachycardias (AVNRTs), 13 patients with accessory pathway (AP)-mediated tachycardias, and 5 patients with atrial fibrillation. The numbers of energy applications, pain scores, procedural times, and outcomes were recorded and compared with age- and sex-matched patients undergoing similar RF procedures. Cryoablation was successful in 26 of 32 patients (11/14 AVNRT, 10/13 AP, 5/5 AF) compared with 30 of 32 undergoing RF procedures, with similar numbers of energy applications and procedural times. Cryothermy was painless in all patients, and the overall procedural discomfort was significantly less than in patients treated with RF (1.3 +/- 2.2 vs 6.1 +/- 3.5). In patients with anteroseptal pathways, cryomapping successfully identified safe sites to target the delivery of energy. Cryothermy is a painless and safe alternative to RF. It may be particularly useful for catheter ablation of patients with pathways close to the atrioventricular node.

Comparison of the affinity of beta-blockers for two states of the beta 1-adrenoceptor in ferret ventricular myocardium

We compared the potency of 11 clinically available beta-blockers as antagonists of the positive inotropic effects of (-)-isoprenaline and CGP12177 on ferret ventricular myocardium. (-)-CGP12177, (-)-pindolol and (-)-alprenolol were non-conventional partial agonists with intrinsic activity of 0.7, 0.2 and 0.1 respectively. All beta-blockers antagonized in a concentration-dependent and surmountable manner the positive inotropic effects of both (-)-isoprenaline and CGP12177. The potency of each beta-blocker was consistently higher against (-)-isoprenaline than against CGP12177. Two groups of beta-blockers were identified. In one group the difference between the pK(B) values of blockade against (-)-isoprenaline and CGP12177 was 1.1 - 1.6 log units ((-)-alprenolol, (-)-pindolol, (-)-bupranolol, nadolol and carvedilol). In the other group the pK(B) difference was of 2.1 - 3.0 log units ((-)-atenolol, metoprolol, bisoprolol, sotalol, (-)-propranolol and (-)-timolol). The beta-blockers competed with (-)-[(125)I]-cyanopindolol for binding to ventricular beta(1)-adrenoceptors. The binding affinities correlated with the corresponding blocking potencies against (-)-isoprenaline. On average the pK(i) values were 0.5 log units smaller than the pK(B) values against (-)-isoprenaline but 1.6 log units greater than the pK(B) values against CGP12177. In ferret ventricle the effects of (-)-isoprenaline appear to be antagonized by beta-blockers through the state of the beta(1)-adrenoceptor for which (-)-[(125)I]-cyanopindolol and beta-blockers have high affinity. The cardiostimulant effects of CGP12177 appear to be mediated through a low-affinity state of the beta(1)-adrenoceptor for which beta-blockers have low affinity.

β2 Adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium

OBJECTIVE

To define the effects of β2 adrenergic receptor stimulation on ventricular repolarisation in vivo.

DESIGN

Prospective study.

SETTING

Tertiary referral centre.

PATIENTS

85 patients with coronary artery disease and 22 normal controls.

INTERVENTIONS

Intravenous and intracoronary salbutamol (a β2 adrenergic receptor selective agonist; 10–30 μg/min and 1–10 μg/min), and intravenous isoprenaline (a mixed β1/β2adrenergic receptor agonist; 1–5 μg/min), infused during fixed atrial pacing.

MAIN OUTCOME MEASURES

QT intervals, QT dispersion, monophasic action potential duration.

RESULTS

In patients with coronary artery disease, salbutamol decreased QTonset and QTpeak but increased QTend duration; QTonset–QTpeak and QTpeak–QTend intervals increased, resulting in T wave prolongation (mean (SEM): 201 (2) ms to 233 (2) ms; p < 0.01). There was a large increase in dispersion of QTonset, QTpeak, and QTend which was more pronounced in patients with coronary artery disease—for example, QTend dispersion: 50 (2) ms baselinev 98 (4) ms salbutamol (controls), and 70 (1) ms baseline v 108 (3) ms salbutamol (coronary artery disease); p < 0.001. Similar responses were obtained with isoprenaline. Monophasic action potential duration at 90% repolarisation shortened during intracoronary infusion of salbutamol, from 278 (4.1) ms to 257 (3.8) ms (p < 0.05).

CONCLUSIONS

β2adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium. The increase in dispersion of repolarisation provides a mechanism whereby catecholamines acting through this receptor subtype may trigger ventricular arrhythmias.

Beta(2) adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium

OBJECTIVE

To define the effects of beta(2) adrenergic receptor stimulation on ventricular repolarisation in vivo.

DESIGN

Prospective study.

SETTING

Tertiary referral centre.

PATIENTS

85 patients with coronary artery disease and 22 normal controls.

INTERVENTIONS

Intravenous and intracoronary salbutamol (a beta(2) adrenergic receptor selective agonist; 10-30 microg/min and 1-10 microg/min), and intravenous isoprenaline (a mixed beta(1)/beta(2) adrenergic receptor agonist; 1-5 microg/min), infused during fixed atrial pacing.

MAIN OUTCOME MEASURES

QT intervals, QT dispersion, monophasic action potential duration.

RESULTS

In patients with coronary artery disease, salbutamol decreased QT(onset) and QT(peak) but increased QT(end) duration; QT(onset)-QT(peak) and QT(peak)-QT(end) intervals increased, resulting in T wave prolongation (mean (SEM): 201 (2) ms to 233 (2) ms; p < 0.01). There was a large increase in dispersion of QT(onset), QT(peak), and QT(end) which was more pronounced in patients with coronary artery disease-for example, QT(end) dispersion: 50 (2) ms baseline v 98 (4) ms salbutamol (controls), and 70 (1) ms baseline v 108 (3) ms salbutamol (coronary artery disease); p < 0.001. Similar responses were obtained with isoprenaline. Monophasic action potential duration at 90% repolarisation shortened during intracoronary infusion of salbutamol, from 278 (4.1) ms to 257 (3.8) ms (p < 0.05).

CONCLUSIONS

beta(2) adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium. The increase in dispersion of repolarisation provides a mechanism whereby catecholamines acting through this receptor subtype may trigger ventricular arrhythmias.

Syncope after effort

A 29-year-old man developed recurrent syncope following exertion. Cardiac investigations revealed no evidence of structural heart disease, but during exercise testing, in the recovery phase, he sustained a bradycardia and then asystole for a prolonged period. Before cardiac massage could be instituted a tonic-clonic fit occurred, and this initiated a return to sinus rhythm. His symptoms were abolished following the implantation of a dual-chamber pacemaker.

Comparison of central venous and inferior vena caval pressures

Inferior vena caval pressures were measured in 60 patients undergoing cardiac catheterization and compared with central venous pressure from within the right atrium. Mean pressures within the abdominal inferior vena cava were essentially the same as mean right atrial pressure, suggesting that the inferior vena cava provides a useful safe alternative for measuring central venous pressure.

Coronary angiography in the presence of peripheral vascular disease: femoral or brachial/radial approach?

Peripheral vascular disease is considered a relative contraindication to the femoral approach for coronary angiography, but no data exist comparing the femoral and brachial/radial routes under these circumstances. We examined the influence of vascular approach on outcome. Two hundred and ninety-seven patients, mean age 67.1 +/- 8.4 years, with clinical or radiographic evidence of aortofemoral peripheral arterial disease underwent diagnostic coronary angiography during a 3-year period at this cardiothoracic center. The approach was successful in 121 of 154 femoral cases (79%) compared with 130 of 143 brachial/radial cases (91%; P < 0.01). Of the 33 failed femoral cases, 15 were then approached from the other femoral artery, with success in 6 (40%), while 18 were approached from the arm, with success in all (100%; P < 0.01). Brachial/radial cases took significantly longer than femoral cases (51 +/- 19 vs. 42 +/- 22 mins; P < 0.01). In cases where the femoral pulse was considered normal, the femoral approach nonetheless failed in 19 of 95 (20%). Major vascular complications (e.g., pulseless limb, arterial dissection, hemorrhage, or false aneurysm) occurred in nine femoral cases vs. zero brachial/radial cases (P < 0.01). Patients with peripheral vascular disease who undergo coronary angiography from the femoral artery have a 1-in-5 risk of procedural failure, necessitating use of an alternative vascular approach, and a 1-in-20 risk of a major vascular complication. Normality of femoral arterial pulsation is not a good predictor of femoral success. Brachial/radial approaches take longer, but succeed more frequently and have a negligible major vascular complication rate. We believe that patients with peripheral vascular disease should undergo coronary angiography via brachial or radial approach. Cathet. Cardiovasc. Intervent. 49:32-37, 2000.

Blockade of putative beta4- and beta1-adrenoceptors by carvedilol in ferret myocardium

The putative beta4-adrenoceptor mediates positive inotropic effects, action potential shortening and arrhythmias in ferret ventricle. Here we compared the affinity of carvedilol at the putative beta4-adrenoceptor and beta1-adrenoceptor, activated by (+/-)-CGP 12177 and (-)-isoprenaline, respectively. In paced right ventricular preparations, carvedilol (0.01-10 micromol/l) was a simple competitive antagonist of the positive inotropic effects of (+/-)-CGP 12177 (slope of Schild-plot = 1.02, pK(B) = 6.8) and (-)-isoprenaline (slope of Schild-plot = 0.98, pK(B) = 8.1). Carvedilol also blocked putative beta4- and beta1-adrenoceptors of left ventricle, left atrium and sino-atrial pacemaker. Carvedilol therefore interacts with the putative beta4-adrenoceptor according to the law of mass action and may provide a lead in the development of putative beta4-adrenoceptor-selective antagonists.

Action potential shortening through the putative beta4-adrenoceptor in ferret ventricle: comparison with beta1- and beta2-adrenoceptor-mediated effects

The electrophysiological responses to (-)-CGP 12177 ((-)-4-(3-tertiarybutylamino-2-hydroxypropoxy) benzimidazol-2-one), an agonist for the putative beta4-adrenoceptor, were investigated on isolated perfused ferret hearts paced at 100 min(-1) and compared to those of (-)-noradrenaline and (-)-adrenaline, mediated through beta1- and beta2-adrenoceptors respectively. The three agonists decreased ventricular monophasic action potential duration but prolonged the action potential plateau; beta3-adrenoceptor-selective agonists had no effect. (-)-CGP 12177 was the most potent, but (-)-noradrenaline the most efficacious; both agonists caused ventricular extra-systoles. Because only (-)-noradrenaline but not (-)-CGP 12177 elicited shortening of the refractory period, the mechanism of arrhythmias mediated through beta1- and putative beta4-adrenoceptors may be different.

Coronary angiography from the radial artery--experience, complications and limitations

AIMS

to assess the outcomes, complications and limitations of coronary angiography performed via percutaneous radial artery puncture.

METHODS AND RESULTS

two hundred and fifty patients underwent diagnostic coronary angiography from the radial artery, 182 (72.8%) of whom had contraindications to the femoral approach, for example due to peripheral vascular disease (n=85), therapeutic anticoagulation (29), or failed femoral approach (17). Procedural success in this high-risk population was achieved in 231 patients (92.4%). Principle reasons for failure were unsuccessful radial access (5) and arterial spasm (5). Procedure duration (SD) for an operator's first 20 cases compared with cases thereafter (min) was 47.7 (16.7) vs. 41.5 (14.6), P=0.0004; fluoroscopy time (min) 9.7 (7.1) vs. 6.6 (5.1), P=0.0001 and procedural success 89.6% vs. 94.1%, P=ns. Complications included two deaths associated temporally with catheterisation, three cases of arterial dissection without ischaemic sequelae and one transient ischaemic attack.

CONCLUSIONS

coronary angiography can be performed successfully from the radial artery, but this approach has limitations, which include the need to demonstrate dual palmar vascular supply, the prolonged learning phase, the procedural failure rate, patient discomfort and a demonstrable incidence of vascular and haemodynamic complications. We believe that radial coronary angiography should only be undertaken when there is a contraindication to the femoral approach.