A Novel Visually Guided Radiofrequency Balloon Ablation Catheter for Pulmonary Vein Isolation: One-Year Outcomes of the Multicenter AF-FICIENT I Trial

[Figure: see text].

Decreases in cardiac catheter laboratory workload during the COVID-19 level 4 lockdown in New Zealand

An increase in coronavirus disease (COVID-19) infections prompted Level 4 lockdown throughout New Zealand from 25 March 2020. We have investigated trends in coronary and electrophysiology (EP) procedures before and during this lockdown. The number of acute procedures for ST elevation myocardial infarction remained stable. In contrast, the number of in-patient angiograms and percutaneous intervention procedures fell by 53% compared with the previous 4 weeks in 2020 and by 56% compared with the corresponding period in 2019. Further study is required to determine the reasons for these trends.

Penetrance and expressivity of the R858H CACNA1C variant in a five-generation pedigree segregating an arrhythmogenic channelopathy

BACKGROUND

Isolated cardiac arrhythmia due to a variant in CACNA1C is of recent knowledge. Most reports have been of singleton cases or of quite small families, and estimates of penetrance and expressivity have been difficult to obtain. We here describe a large pedigree, from which such estimates have been calculated.

METHODS

We studied a five-generation family, in which a CACNA1C variant c.2573G>A p.Arg858His co-segregates with syncope and cardiac arrest, documenting electrocardiographic data and cardiac symptomatology. The reported patients/families from the literature with CACNA1C gene variants were reviewed, and genotype-phenotype correlations are drawn.

RESULTS

The range of phenotype in the studied family is wide, from no apparent effect, through an asymptomatic QT interval prolongation on electrocardiography, to episodes of presyncope and syncope, ventricular fibrillation, and sudden death. QT prolongation showed inconsistent correlation with functional cardiology. Based upon analysis of 28 heterozygous family members, estimates of penetrance and expressivity are derived.

CONCLUSIONS

These estimates of penetrance and expressivity, for this specific variant, may be useful in clinical practice. Review of the literature indicates that individual CACNA1C variants have their own particular genotype-phenotype correlations. We suggest that, at least in respect of the particular variant reported here, "arrhythmogenic channelopathy" may be a more fitting nomenclature than long QT syndrome.

Effects of AV delay and VV delay on left atrial pressure and waveform in ambulant heart failure patients: insights into CRT optimization

BACKGROUND

We hypothesized that left atrial pressure (LAP) obtained by a permanent implantable sensor is sensitive to changes in cardiac resynchronization therapy (CRT) settings and could guide CRT optimization to improve the response rate. We investigated the effect of CRT optimization on LAP and its waveform parameters in ambulant heart failure (HF) patients.

METHODS

CRT optimization was performed in eight ambulant HF patients, using echocardiography as reference. LAP waveform was acquired at each of eight atrioventricular (AV) intervals and five inter-ventricular (VV) intervals. Selected waveform parameters were also evaluated for their sensitivity to CRT changes and agreement with echocardiography-guided optimal settings.

RESULTS

Optimal AV and VV intervals varied considerably between patients. All patients exhibited significant changes in waveform morphology with AV optimization. Optimal AV delay determined from echocardiography ranged between 140 ms and 225 ms. Mean LAP tended to be lower at optimal setting 14 ± 3 mmHg compared to shorter (<100 ms) or longer (>160 ms) AV settings (P = 0.16). There were clear trends to smaller peak a-wave (P = 0.11) and gentler positive a-slope (P = 0.15) and positive v-slope (P = 0.09) with longer AV delays. Mean LAP and negative v-wave slope correlated well with echo-guided optimal setting, r = 0.91 (P = 0.001) and 0.79 (P = 0.03), respectively. No significant effects on LAP or waveform were seen during VV optimization.

CONCLUSIONS

LAP and its waveform changes considerably with AV optimization. There is good agreement between echo-guided optimal setting and LAP. LAP could provide an objective guide to CRT optimization. (Clinical Trial Registry information: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00632372).

Integrated microscopy techniques for comprehensive pathology evaluation of an implantable left atrial pressure sensor

The safety and efficacy of an implantable left atrial pressure (LAP) monitoring system is being evaluated in a clinical trial setting. Because the number of available specimens from the clinical trial for histopathology analysis is limited, it is beneficial to maximize the usage of each available specimen by relying on integrated microscopy techniques. The aim of this study is to demonstrate how a comprehensive pathology analysis of a single specimen may be reliably achieved using integrated microscopy techniques. Integrated microscopy techniques consisting of high-resolution gross digital photography followed by micro-computed tomography (micro-CT) scanning, low-vacuum scanning electron microscopy (LVSEM), and microground histology with special stains were applied to the same specimen. Integrated microscopy techniques were applied to eight human specimens. Micro-CT evaluation was beneficial for pinpointing the location and position of the device within the tissue, and for identifying any areas of interest or structural flaws that required additional examination. Usage of LVSEM was reliable in analyzing surface topography and cell type without destroying the integrity of the specimen. Following LVSEM, the specimen remained suitable for embedding in plastic and sectioning for light microscopy, using the positional data gathered from the micro-CT to intersect areas of interest in the slide. Finally, hematoxylin and eosin (H&E) and methylene blue staining was deployed on the slides with high-resolution results. The integration of multiple techniques on a single specimen maximized the usage of the limited number of available specimens from the clinical trial setting. Additionally, this integrated microscopic evaluation approach was found to have the added benefit of providing greater assurance of the derived conclusions because it was possible to cross-validate the results from multiple tests on the same specimen.

Urocortin-2 infusion in acute decompensated heart failure: findings from the UNICORN study (urocortin-2 in the treatment of acute heart failure as an adjunct over conventional therapy)

OBJECTIVES

The purpose of this study is to investigate the effects of urocortin-2 as adjunct therapy in acute decompensated heart failure (ADHF).

BACKGROUND

Urocortin-2 produced favorable integrated effects in experimental heart failure but there are no equivalent human data. We describe the first therapeutic study of urocortin-2 infusion in ADHF.

METHODS

Fifty-three patients with ADHF were randomly assigned to 5 ng/kg/min of urocortin-2 or placebo infusion for 4 h as an adjunct therapy. Changes in vital signs, plasma neurohormonal and renal indices during treatment were compared using repeated-measures analysis of covariance. Ten patients in each arm underwent more detailed invasive hemodynamic evaluation.

RESULTS

Urocortin-2 produced greater falls in systolic blood pressure compared to placebo (16 ± 5.8 mm Hg, p < 0.001) with nonsignificant increases in heart rate (5.7 ± 3.8 beats/min, p = 0.07) and increased cardiac output (2.1 ± 0.4 l/min vs. -0.1 ± 0.4 l/min, p < 0.001) associated with a 47% reduction in calculated total peripheral resistance (p = 0.015). Falls in pulmonary artery and pulmonary capillary wedge pressures did not differ significantly between groups. Urocortin-2 reduced urine volume and creatinine clearance during infusion but these returned to above baseline level in the 8 h after infusion. Plasma renin activity rose briefly with urocortin-2 coinciding with reductions in blood pressure (p < 0.001). B-type natriuretic peptide levels fell significantly over 24 h with urocortin-2 (p < 0.01) but not with placebo.

CONCLUSIONS

Urocortin-2 infusion in ADHF markedly augmented cardiac output without significant reflex tachycardia. Renal indices fell transiently concurrent with urocortin-2-induced reductions in blood pressure. Further investigations are required to uncover the full potential of urocortin-2 in treating ADHF.

The performance of high sensitivity troponin for the diagnosis of acute myocardial infarction is underestimated

Many papers evaluating high sensitivity troponin assays make the diagnosis of myocardial infarction based on conventional troponin assays in clinical use at the time of recruitment. Such analyses often do not show superiority of high sensitivity assays compared with contemporary assays meeting precision guidelines.

Three hundred and twenty-two patients presenting to the emergency department between November 2006 and April 2007 for evaluation for acute coronary syndrome had serial (0 h and >6 h) bloods taken to compare troponin assays (Roche hsTnT, Abbott TnI, Roche TnT and Vitros TnI). The diagnosis of myocardial infarction was made using each troponin assay separately with which that same assay was analysed for diagnostic performance.

The rate of myocardial infarction would be 38.9% using serial hsTnT, 31.3% using serial Abbott TnI, 27.1% using serial TnT and 26.4% using serial Vitros TnI. The baseline sensitivities (0 h) are 89.9% (85.2–93.3) for hsTnT, 77.9% (71.0–87.5) for Abbott TnI, 73.0% (65.6–78.7) for TnT and 86.8% (74.6–94.4%) for Vitros TnI. The specificities (peak 0 h and >6 h samples) are 93.1% (91.2–93.1) for hsTnT, 88.3% (86.5–88.3) for Abbott TnI, 92.2% (90.5–92.2) for TnT and 90.6% (70.1–90.6) for Vitros TnI.

hsTnT has superior sensitivity for myocardial infarction than even assays at or near guideline precision requirements (Abbott and Vitros TnI). The specificity of hsTnT assay is not as poor as previous analyses suggest.

Surgical radiofrequency ablation for atrial fibrillation: the Christchurch, New Zealand experience

AIMS

To report the long-term results following surgical radiofrequency ablation (RFA) for atrial fibrillation as an adjunct to other cardiac surgery at Christchurch Hospital.

METHODS

A retrospective observational audit review of outcomes. The sample population included all patients identified as having undergone surgical RFA for atrial fibrillation at Christchurch Hospital, between the first procedure performed on 2 July 2001 and 28 January 2009.

RESULTS

A total of 44 patients underwent surgical RFA between 2 July 2001 and 28 January 2009. Postoperatively there were three deaths prior to discharge (7%). Pacemakers were required in four patients (9%), and two patients subsequently underwent catheter ablation for atrial arrhythmias. In the immediate postoperative period only three patients remained in atrial fibrillation. At last follow-up up to 102 months from surgery (45 plus or minus 29 months), 27 patients had developed persistent atrial fibrillation and four persistent atrial flutter. Persisting long-term benefit was seen in seven patients (18%, 7/38); five patients were in stable sinus rhythm, one had paroxysmal atrial fibrillation and one paroxysmal atrial flutter.

CONCLUSIONS

Whilst the procedure was effectively acutely, the recurrence of atrial fibrillation was high and development of new atrial flutter common over long-term follow-up.

Pulmonary vein ablation for atrial fibrillation: the Christchurch, New Zealand experience

AIMS

To report the long-term results following percutaneous pulmonary vein ablation (PVA) for atrial fibrillation (AF) at Christchurch Hospital.

METHODS

A retrospective observational audit review of outcomes. The sample population included all patients identified as having undergone percutaneous radiofrequency ablation of multiple pulmonary veins at Christchurch Hospital, from the first procedure performed on 29 September 2001 until 15 December 2009.

RESULTS

A total of 187 patients underwent pulmonary vein ablation. The patient population was predominantly younger (mean age 51) and male (83%) with no important comorbidity. Following a single procedure only, the chance of remaining free of AF at 12 months was 0.74 for patients with paroxysmal AF (PAF) and 0.60 for patients with persistent AF (PsAF). 52 patients (28%) underwent a repeat procedure within 12 months of their index ablation owing to early recurrence of AF. 5-year survival free of clinical AF when analysed following these early repeat procedures, if required, was 0.74 and 0.56 for PAF and PsAF patients respectively. Complications occurred following 6% of procedures and were serious in 2.5%. New atrial flutter developed in 6% of patients.

CONCLUSIONS

PVA is an effective treatment for AF, with better outcomes in patients with paroxysmal atrial fibrillation. However, as it carries a significant risk, we recommend that its application be reserved for patients with highly symptomatic, medication-refractory disease.

Prediction of cardiac rhythm 1 year following cardioversion for atrial fibrillation

BACKGROUND

There is little recent information regarding outcome and its determinants following cardioversion (CV) for atrial fibrillation (AF) or flutter. This study aims to help improve prediction of cardiac rhythm outcome following CV for AF.

METHODS

Cardiac rhythm at 6 weeks and 12 months was documented following elective (EC; n=496) or immediate (IC; n=52) cardioversion for AF or atrial flutter in a single referral centre.

RESULTS

65 and 58% of IC patients remained in sinus rhythm (SR) 6 weeks and 1 year after CV (respectively) compared with 43% and 30% in EC patients (P<0.001). Independent positive predictors of SR 6 weeks after cardioversion included amiodarone therapy (OR 2.04 [1.28-3.33], P<0.01) and atrial flutter (OR 1.85 [1.09-3.13], P<0.05). Negative predictors included the need for >1 shock to achieve SR (OR 1.61 [1.12-2.37], P=0.011) and arrhythmia duration, (OR 0.96 [0.95-0.97], P<0.001). At 1 year, amiodarone, duration of arrhythmia and the need for >1 shock remained independent predictors of rhythm.

CONCLUSIONS

The number of shocks required to achieve SR is a newly demonstrated independent predictor of rhythm outcome after elective CV.

Comparison of high sensitivity and contemporary troponin assays for the early detection of acute myocardial infarction in the emergency department

Background

Current guidelines define acute myocardial infarction (AMI) by the rise and/or fall of cardiac troponin with ≥1 value above the 99th percentile. Past troponin assays have been unreliable at the lower end of the range. Highly sensitive assays have therefore been developed to increase the clinical sensitivity for detection of myocardial injury.

Methods

Three hundred and thirty-two patients with chest pain suggestive of AMI were prospectively recruited between November 2006 and April 2007. Serial blood samples were analysed to compare Roche Elecsys high sensitivity troponin T (hsTnT), Abbott Architect troponin I 3rd generation (TnI 3) and Roche Elecsys troponin T (TnT) for the diagnosis of AMI.

Results

One hundred and ten (33.1%) patients were diagnosed with AMI. Test performance for the diagnosis of AMI, as quantified by receiver operating characteristic area under the curve (95% confidence intervals) for baseline/follow-up troponins were as follows: hsTnT 0.90 (0.87–0.94)/0.94 (0.91–0.97), TnI 3 0.88 (0.84–0.92)/0.93 (0.90–0.96) and TnT 0.80 (0.74–0.85)/0.89 (0.85–0.94). hsTnT was superior to TnT ( P < 0.001/0.013 at baseline/follow-up) but equivalent to TnI 3. For patients with a final diagnosis of AMI, baseline troponins were raised in more patients for hsTnT (83.6%) than TnI 3 (74.5%) and TnT (62.7%). A delta troponin of ≥20% increased the specificity of hsTnT from 80.6% to 93.7% but reduced sensitivity from 90.9% to 71.8%.

Conclusion

hsTnT was superior to TnT but equivalent to TnI 3 for the diagnosis of AMI. Serial troponin measurement increased test performance. hsTnT was the most likely to be raised at baseline in those with AMI. A delta troponin increases specificity but reduces sensitivity.

High sensitivity troponin outperforms contemporary assays in predicting major adverse cardiac events up to two years in patients with chest pain

Background

Previous studies have shown a risk of subsequent major adverse cardiovascular events (MACEs) in patients with suspected acute coronary syndromes (ACSs) and elevated cardiac troponin. The aim of this study was to compare prognostic utility of high-sensitivity troponin with contemporary troponin assays in such patients.

Methods

In total, 332 patients with suspected ACS were investigated between November 2006 and April 2007; all were followed for two years. Blood samples were analysed to compare Roche Elecsys high-sensitivity troponin T (hsTnT), Abbott Architect troponin I 3rd generation (TnI 3) and Roche Elecsys troponin T (TnT), for the prediction of MACE (composite of cardiovascular death, non-fatal myocardial infarction and revascularization).

Results

Sixty-eight patients (20.5%) experienced MACE between discharge and two years. Receiver operating characteristic (ROC) curve derived area under the ROC curve (95% confidence intervals) for baseline hsTnT were 0.70 (0.63–0.76), TnI 3 0.66 (0.59–0.73) and TnT 0.61 (0.53–0.69). hsTnT ( P = 0.001) was superior to TnT and TnI 3 trended ( P = 0.094) to superiority but were equivalent to each other. hsTnT best stratified patients with cumulative event rates for two-year MACE of 35.6% for levels ≥99th percentile, 17.9% for levels between the limit of detection (LOD) and 99th percentile and 5.4% for levels <LOD compared with TnI 3: 33.0%, 31.1% and 10.9%, respectively. TnT had MACE rates of 36.7% when ≥99th percentile and 15.4% when <99th percentile (=LOD).

Conclusions

hsTnT outperformed contemporary TnI and TnT assays for the prediction of MACE at two years. Those with levels below the LOD for hsTnT identified a group of patients at very low risk for adverse events.

Direct left atrial pressure monitoring in severe heart failure: long-term sensor performance

We report the stability, accuracy, and development history of a new left atrial pressure (LAP) sensing system in ambulatory heart failure (HF) patients. A total of 84 patients with advanced HF underwent percutaneous transseptal implantation of the pressure sensor. Quarterly noninvasive calibration by modified Valsalva maneuver was achieved in all patients, and 96.5% of calibration sessions were successful with a reproducibility of 1.2 mmHg. Absolute sensor drift was maximal after 3 months at 4.7 mmHg (95% CI, 3.2–6.2 mmHg) and remained stable through 48 months. LAP was highly correlated with simultaneous pulmonary wedge pressure at 3 and 12 months (r = 0.98, average difference of 0.8 ± 4.0 mmHg). Freedom from device failure was 95% (n = 37) at 2 years and 88% (n = 12) at 4 years. Causes of failure were identified and mitigated with 100% freedom from device failure and less severe anomalies in the last 41 consecutive patients (p = 0.005). Accurate and reliable LAP measurement using a chronic implanted monitoring system is safe and feasible in patients with advanced heart failure.

An entirely subcutaneous implantable cardioverter-defibrillator

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system.

METHODS

First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients.

RESULTS

The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (+/-SD) energy requirement (36.6+/-19.8 J vs. 11.1+/-8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10+/-1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.

CONCLUSIONS

In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. (ClinicalTrials.gov numbers, NCT00399217 and NCT00853645.)