Durable pulmonary vein isolation with optimized high-power and very high-power short-duration temperature-controlled ablation: A step-by-step guide.

INTRODUCTION: Through systematic scientific rigor, the CLOSE guided workflow was developed and has been shown to improve pulmonary vein isolation durability. However, this technique was developed at a time when using power-controlled ablation catheters with conventional power ranges was the norm. There has been increased adoption of a high-power and very high-power short-duration ablation practice propelled by the availability of the temperature-controlled radiofrequency QDOT MICRO catheter. METHODS: There are fundamental differences in biophysics between very high-powered temperature guided ablation and conventional ablation strategy that may impact patient outcomes. The catheter's design and ablation modes offer flexibility in technique while accommodating the individual operator's clinical discretion and preference to deliver a durable, transmural, and contiguous lesion set. RESULTS: Here, we provide recommendations for 3 different workflows using the QDOT MICRO catheter in a step-by-step manner for pulmonary vein isolation based on our cumulative experience as early adopters of the technology and the data available in the scientific literature. CONCLUSIONS: With standardization, temperature-controlled ablation with the QDOT MICRO catheter provides operators the flexibility of implementing different ablation strategies to ensure durable contiguous pulmonary vein isolation depending on patient characteristics.

Ultralow temperature cryoablation using near-critical nitrogen for cavotricuspid isthmus-ablation, first-in-human results.

INTRODUCTION: Cryoablation has evolved as a safe alternative to radiofrequency ablation in the treatment of several supraventricular arrhythmias and has potential advantages, yet is limited by the properties of the cryogen used. We investigated a novel ultralow temperature cryoablation (ULTC) system using nitrogen near its liquid-vapor critical point as a freezing source, achieving temperatures as low as -196 degrees Celsius in a long linear catheter with a continuous energy release. Initial safety, procedural and efficacy outcomes of ULTC are described in patients undergoing cavotricuspid isthmus (CTI) ablation. METHODS AND RESULTS: The Cryocure studies (NCT02355106, NCT02839304) are prospective, single-arm, multi-center, first-in-human clinical studies in 17 patients with atrial flutter (AFL) and 13 patients with atrial fibrillation (AF). A total of 30 patients, mean age 65 ± 8 years old and 67% male, were enrolled and underwent ablation of the CTI. Acute success, defined as the confirmation of stable bidirectional conduction block across the CTI, was achieved in all 30 patients. After 12 months of follow-up, 14 out of 17 AFL patients remained free from any AFL. One (3.3%) procedure-related but not device-related serious adverse event was reported, involving transient inferolateral ST-elevation associated with temporary AV conduction block. CONCLUSION: In this first-in-human clinical study the safety and performance results demonstrate the capabilities of ultralow temperature near-critical nitrogen as an effective energy source for CTI ablation. Ongoing, larger, studies should confirm our findings and evaluate the capabilities to create linear and focal transmural lesions in other arrhythmias.

Adenosine plus dipyridamole: a novel strategy to enhance adenosine-induced conduction recovery after pulmonary vein isolation.

AIMS: Intravenous administration of adenosine after a pulmonary vein (PV) isolation procedure can unmask residual, so-called 'dormant', conduction that would otherwise remain unnoticed. Elimination of these dormant potentials is challenging because of the transient effect of adenosine, often requiring repeated injections. We tested the hypothesis that dipyridamole, a drug which inhibits adenosine deamination, can provoke longer-lasting unmasking of dormant conduction. METHODS AND RESULTS: In 191 patients with drug refractory paroxysmal atrial fibrillation, a bolus of 12-24 mg of adenosine was administered after all 764 PVs were isolated. In the case of transient dormant conduction, a short infusion of dipyridamole 50 mg was given and a bolus of adenosine was repeated. In all cases, re-isolation was attempted guided by the activation pattern in the PV on a circular mapping catheter. Duration of adenosine-induced dormant conduction before and after dipyridamole was recorded as the time between administration of adenosine and cessation of dormant conduction either spontaneously or by catheter ablation. Transient dormant conduction was re-established by a single bolus of adenosine in 24 of 191 patients (12.6%). Mean duration of adenosine-induced dormant conduction before dipyridamole was 13.1 ± 6.4 s, whereas it was significantly longer at 218.9 ± 165.6 s after dipyridamole (P < 0.0001). Eighteen of the 24 PVs were re-isolated by catheter ablation before spontaneous cessation of dormant conduction, and in 6 cases dormant conduction disappeared spontaneously before PV re-isolation was achieved. CONCLUSION: Dipyridamole significantly prolongs the effect of adenosine to unmask dormant conduction after PV isolation and may thus facilitate its elimination by catheter ablation.

Drug-eluting stents for the treatment of pulmonary vein stenosis after atrial fibrillation ablation.

AIMS: Pulmonary vein (PV) stenosis (PVS) is a complication of radiofrequency PV isolation (PVI). Reported restenosis rates after balloon dilatation and bare-metal stent implantation are high. Drug-eluting stent implantation (DES) has not been reported in the setting of PVS. METHODS AND RESULTS: Patients suspected of having PVS after PVI based on clinical symptoms and transesophageal echocardiography (TEE) follow-up (FU) were referred for PV DES. One or more branches of the affected PV as documented by angiography were stented (paclitaxel or zotarolimus DES). Follow-up consisted of repeat PV angiography and TEE. Over a period of 2 years, five patients were treated with a total of eight DES. A paclitaxel DES was used in seven of eight implants. Mean FU was 12 ± 14 months during which all patients remained asymptomatic. Transesophageal echocardiography Doppler maximal flow velocity (V(max)) of the affected PVs rose from 58 ± 6 cm/s pre-PVI to 207 ± 20 cm/s pre-DES (+358%, P < 0.0001). After DES, V(max) decreased acutely with 86 ± 15 cm/s (-58%, P < 0.01). During FU, V(max) remained stable in three patients and increased moderately in one. Angiography at 3 months confirmed absence of restenosis in the first three patients and moderate (40%) restenosis in one patient. In one patient, an increase of V(max) back to pre-DES values correlated with a 65% peri-stent stenosis, treated with a redo DES. In total, after seven primary DES only one (asymptomatic) proximal margin restenosis required re-stenting. CONCLUSION: Initial experience with DES for PV stenosis suggests an excellent stent patency rate. Transesophageal echocardiography Doppler measurements provide a viable way of monitoring stent patency.

Intra- and interobserver variability during in vitro validation of two novel methods for intra-abdominal pressure monitoring.

OBJECTIVE: Intra-abdominal pressure (IAP) measurement techniques vary in automaticity and reproducibility. This study evaluated the intra- and interobserver variability of two new IAP measurement techniques. METHODS: A one-half open, 30-l container was used with two IAP catheters (Foley Manometer, balloon-tipped catheter) contained in a 100-ml infusion bag. To simulate intra-abdominal hypertension the container was filled with water using 5-cm increments (0-25 cmH2O). Pressure was determined by observers using the Foley Manometer and simultaneously recorded using an IAP monitor. Observers were blinded to the reference levels. RESULTS: Fifteen observers conducted three pressure readings at each of the six pressure levels with the Foley technique, giving 270 readings. These were paired with the automated monitor readings and the height of the water column. The intra- and interobserver coefficients of variation were low for both methods. The Spearman correlation coefficient was higher than 0.9 for all paired measurements and Bland-Altman analysis comparing the reference H2O column to both measurement techniques showed a very good agreement at all pressure intervals (bias 0.1+/-0.6 cmH2O) and a consistent, low underestimation of the reference water column pressure by both techniques. CONCLUSIONS: Both the Foley Manometer and the IAP monitor are reliable and reproducible methods to measure IAP in this in vitro model. The coefficient of variation for each technique is low and decreases with increasing IAP, the monitor giving more reproducible results than the Foley Manometer.

Intra-abdominal hypertension in the critically ill: it is time to pay attention.

PURPOSE OF THE REVIEW: There has been an exponentially increasing interest in intra-abdominal hypertension (IAH). Comparison of the published data however is difficult due to the lack of consensus definitions. This review will focus on the available literature from the last 2 years. A Medline and PubMed search was performed using 'intra-abdominal pressure' (IAP), 'intra-abdominal hypertension' (IAH), and 'abdominal compartment syndrome' (ACS) as search items. The aim was to find an answer to the question 'Isn't it time to pay attention to intra-abdominal pressure in the critically ill?' RECENT FINDINGS: Although the number of studies published on this topic is steadily increasing and confirms the pathophysiologic implications of IAH on end-organ function within and outside the abdominal cavity it remains difficult to compare the literature data because the measurement methods and definitions used are not uniform. Provocative data have been published regarding the interactions between the abdominal and thoracic compartments especially in patients with capillary leak and fluid overload; most of this data raises even more questions than it gives answers and may therefore strengthen the nonbelievers who consider IAP, IAH and ACS as epiphenomena in critically ill patients. Unless the international scientific community does not come forward with clear-cut definitions we will keep comparing 'apples with oranges.' SUMMARY: It is time to pay attention to intra-abdominal pressure in the critically ill. It is also time for standardized IAP measurement methods, good consensus definitions and randomized interventional studies.