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Initial impedance decrease as an indicator of good catheter contact: Insights from radiofrequency ablation with force sensing catheters

BACKGROUNDnGood catheter-tissue contact force (CF) is critical for transmural and durable lesion formation during radiofrequency (RF) ablation but is difficult to assess in clinical practice. Tissue heating during RF application results in an impedance decrease at the catheter tip.nnnOBJECTIVEnThe purpose of this study was to correlate achieved CF and initial impedance decreases during atrial fibrillation (AF) ablation.nnnMETHODSnWe correlated achieved CF and initial impedance decreases in patients undergoing ablation for AF with two novel open-irrigated CF-sensing RF catheters (Biosense Webster SmartTouch, n = 647 RF applications; and Endosense TactiCath, n = 637 RF applications). We then compared those impedance decreases to 691 RF applications with a standard open-irrigated RF catheter (Biosense Webster ThermoCool).nnnRESULTSnWhen RF applications with the CF-sensing catheters were analyzed according to an achieved average CF <5 g, 5-10 g, 10-20 g, and >20 g, the initial impedance decreases during ablation were larger with greater CF. Corresponding median values at 20 seconds were 5 Ω (interquartile range [IQR] 2-7), 8 Ω (4-11), 10 Ω (7-16), and 14 Ω (10-19) with the SmartTouch and n/a, 4 Ω (0-10), 8 Ω (5-12), and 13 Ω (8-18) with the TactiCath (P <.001 between categories for both catheters). When RF applications with the SmartTouch (CF-sensing catheter, median achieved CF 12 g) and ThermoCool (standard catheter) were compared, the initial impedance decrease was significantly greater in the CF-sensing group with median decreases of 10 Ω (6-14 Ω) vs 5 Ω (2-10 Ω) at 20 seconds (P <.001 between catheters).nnnCONCLUSIONnThe initial impedance decrease during RF applications in AF ablations is larger when greater catheter contact is achieved. Monitoring of the initial impedance decrease is a widely available indicator of catheter contact and may help to improve formation of durable ablation lesions.

Complications of cardiac implants: handling device infections.

Managing patients with cardiac implantable electrophysiological devices (CIED) infections can be challenging. The first step should be prevention, which involves patient selection, timing of implantation, and the procedure itself. After implantation, a high degree of suspicion should be applied in order to correctly diagnose patients with infected implanted devices. It is necessary to recognize that patients can present with a wide variety of signs and symptoms. Once diagnosed, the next step is determining if it is a local pocket infection or system infection. In almost every patient, in addition to antibiotics, complete removal of ALL hardware is required. Transvenous lead extraction is now safe and effective, but should only be performed at experienced centres with a practiced extraction team, all possible needed equipment, and cardiothoracic surgical backup. After extraction, the indication for CIED therapy should be re-evaluated to determine re-implantation is warranted. Timing of re-implantation depends on a variety of factors such as type of infection or valvular involvement and should be made in concordance with an infectious disease specialist. This review is aimed at introducing the steps needed to manage patients with infected cardiac devices.

Acute Failure of Catheter Ablation for Ventricular Tachycardia Due to Structural Heart Disease: Causes and Significance

Background Acute end points of catheter ablation for ventricular tachycardia (VT) remain incompletely defined. The aim of this study is to identify causes for failure in patients with structural heart disease and to assess the relation of this acute outcome to longer‐term management and outcomes. Methods and Results From 2002 to 2010, 518 consecutive patients (84% male, 62±14 years) with structural heart disease underwent a first ablation procedure for sustained VT at our institution. Acute ablation failure was defined as persistent inducibility of a clinical VT. Acute ablation failure was seen in 52 (10%) patients. Causes for failure were: intramural free wall VT in 13 (25%), deep septal VT in 9 (17%), decision not to ablate due to proximity to the bundle of His, left phrenic nerve, or a coronary artery in 3 (6%), and endocardial ablation failure with inability or decision not to attempt to access the epicardium in 27 (52%) patients. In multivariable analysis, ablation failure was an independent predictor of mortality (hazard ratio 2.010, 95% CI 1.147 to 3.239, P=0.004) and VT recurrence (hazard ratio 2.385, 95% CI 1.642 to 3.466, P<0.001). Conclusions With endocardial or epicardial ablation, or both, acute ablation failure was seen in 10% of patients, largely due to anatomic factors. Persistence of a clinical VT is associated with recurrence and comparatively higher mortality.

Catheter ablation of atrial arrhythmias after cardiac transplantation: findings at EP study utility of 3-D mapping and outcomes.

Management of atrial arrhythmias (AA) in orthotopic heart transplant (OHT) patients is challenging.

Relation of the unipolar low-voltage penumbra surrounding the endocardial low-voltage scar to ventricular tachycardia circuit sites and ablation outcomes in ischemic cardiomyopathy.

Magnetic resonance (MR)‐imaging has shown that infarct scars causing ventricular tachycardia (VT) can extend deep to and beyond bipolar low‐voltage areas (LVAs) and may be a source of ablation failure. We hypothesized that the size of the unipolar LVA “penumbra” beyond the overlying bipolar scar may predict outcome of endocardial VT ablation.

Impact of general anesthesia on initiation and stability of VT during catheter ablation

BACKGROUNDnRadiofrequency ablation of ventricular tachycardia (VT) may be performed with general anesthesia (GA) or conscious sedation; however, comparative data are limited.nnnOBJECTIVEnThe purpose of the study was to assess the effects of GA on VT inducibility and stability.nnnMETHODSnA retrospective comparison of 226 patients undergoing radiofrequency ablation for scar-related VT under GA or intravenous conscious sedation was performed. Data were then prospectively collected in 73 patients undergoing noninvasive programmed stimulation (NIPS) while awake, followed by GA and invasive programmed stimulation for VT induction.nnnRESULTSnIn the retrospective study, groups did not differ in VT inducibility, complications, or abolition of clinical VT. Intravenous hemodynamic support was used more often in the GA group. In the prospective group, 12 patients (16%) were noninducible with NIPS. Of the 61 patients with inducible VT with NIPS, 5 (8%) were noninducible with GA, 25 (41%) were inducible with more aggressive simulation, and 31 (51%) were inducible with the same or less aggressive stimulation. Of the 56 patients who were inducible with NIPS and under GA, 28 (50%) had the same induced VTs and 28 (50%) had different induced VTs. In 23 of 56 patients, the clinical VT morphology was known. The clinical VT was reproduced with NIPS in 17 of 23 patients (74%) and under GA in 13 of 23 patients (59%). Under GA, nonclinical VTs were more often induced in patients with a lower ejection fraction and nonischemic cardiomyopathy.nnnCONCLUSIONnGA does not prevent inducible VT in the majority of patients. GA is associated with an increased use of hemodynamic support, but this did not adversely affect VT stability or procedure outcomes.

Reentrant Ventricular Tachycardia Originating From the Periaortic Region in the Absence of Overt Structural Heart Disease

Background—In the absence of overt structural heart disease, most left ventricular outflow tract ventricular tachycardias (VTs) have a focal origin and are benign. We hypothesized that multiple morphologies (MMs) of inducible left ventricular outflow tract VT may indicate a scar-related VT that can mimic idiopathic VT. Methods and Results—Of 54 consecutive patients referred for ablation of sustained outflow tract VT without overt structural heart disease, 24 had left ventricular outflow tract VT, 10 had MM VT, and 14 had a single VT (SM). The MM group were older (70.3±4.3 versus 53.9±15.9 years; P=0.004), had more hypertension (100% versus 29%; P=0.0006), and had longer PR intervals and QRS durations compared with the SM group. In contrast to the SM group, the MM group VTs had features consistent with reentry, including induction by programmed stimulation without isoproterenol, entrainment in some, and abnormal electrograms in the periaortic area. Periaortic region voltages suggested scar in the MM group, but not in the SM group. MRI in 2 MM patients was consistent with scar, but not in 10 SM patients. Longer radiofrequency applications were required in the MM group than in the SM group. At a median follow-up of 9.7 (3.0–32.0) months, recurrences tended to be more frequent in the MM group than in the SM group (70% versus 22%; P=0.07). Conclusions—VTs from small regions of periaortic scar can mimic idiopathic VT but are suggested by multiple VT morphologies and are more difficult to ablate. Whether these patients are at greater risk, as feared for other scar-related VTs, warrants further study.

Early release of high-sensitive cardiac troponin during complex catheter ablation for ventricular tachycardia and atrial fibrillation.

BackgroundRadiofrequency ablation results in intentional cardiac injury. We aimed to assess the kinetics of cardiac injury as measured by cardiac troponin release following ventricular ablation and atrial ablation.MethodsPatients undergoing ablation for ventricular tachycardia (VT) with structural heart disease (19 patients) or atrial fibrillation (AF, 24 patients) were prospectively enrolled. High-sensitivity cardiac troponin T (hs-cTnT) and high-sensitivity cardiac troponin I (hs-cTnI) were measured before ablation as well as 30xa0min, 60xa0min, 90xa0min, 120xa0min, 4xa0h, 8xa0h, and 24xa0h after applying the first ablation lesion.ResultsMedian ablation time, power used, and energy delivered were 28xa0min, 39xa0W, and 69,713xa0J in VT ablations and 55xa0min, 29xa0W, and 95,425xa0J in AF ablations, respectively. Release of hs-cTnT occurred promptly with both, but reached greater levels earlier for ventricular compared to atrial ablation (hs-cTnT after 30xa0min 191 vs. 31xa0ng/l, after 1xa0h 467 vs. 80xa0ng/l; hs-cTnI after 30xa0min 132 vs. 30xa0ng/l, after 1xa0h 331 vs. 76xa0ng/l; pu2009<u20090.001 for all comparisons). After 24xa0h, levels were similar (hs-cTnT 1325 vs. 1303xa0ng/l, pu2009=u20090.92; hs-cTnI 2165 vs. 1996xa0ng/l, pu2009=u20090.55). Levels of hs-cTnT after 24xa0h correlated well with the energy delivered in AF ablations (ru2009=u20090.81 and ru2009=u20090.75, pu2009<u20090.001), but not in VT ablations (ru2009=u20090.35 and ru2009=u20090.44, pu2009=u2009ns).ConclusionsEvidence of cardiac injury as indicated by the release of hs-cTnT and hs-cTnI occurs early with atrial and ventricular ablation. Higher early levels are observed in ventricular ablations, but levels are similar after 24xa0h. The extent of total troponin release seems to correlate well with the amount of energy delivered in AF ablations, but not in VT ablations.

Incidence of nonphysiologic short VV intervals detected by the sensing integrity counter with integrated bipolar compared with true bipolar leads: clinically inconsequential or cause for concern?

IntroductionThe need to detect impending implantable cardiac defibrillator (ICD) lead failure has grown. Automated sensing diagnostics have been developed for this reason. The sensing integrity counter (SIC) is one such oversensing diagnostic, which forms an integral part of the Medtronic™ lead integrity alert (LIA) feature on implantable defibrillators. It records nonphysiologic short VV intervals (NPSVVIs). It is unclear whether SIC data derived from integrated bipolar (IBP) leads need to be interpreted differently when compared to true bipolar (TBP) leads. We hypothesized that IBP ICD leads by virtue of a larger “antennae” may generate more NPSVVIs on than TBP leads, leading to more false-positive SIC counts.MethodsEqual durations of remote monitoring records of 44 patients (mean age of 65.9u2009±u20092.2xa0years, 52xa0% female) with IBP ICD leads and Medtronic (MDT) generators (IBP group) were compared with those of 44 randomly selected patients (64.0u2009±u20092.2xa0years, 24xa0% female) who had TBP ICD leads and MDT generators (TBP group). Mean surveillance time, defined as the time over which the cumulative SIC count was acquired, was 614u2009±u200944xa0days (TBP group) vs. 620u2009±u200949xa0days (IBP group, pu2009=u2009ns). The mean time of follow-up following the first documented short VV interval was 115.2xa0months in the integrated bipolar group and 66.9xa0months in the true bipolar group. Leads on advisory were excluded from the study.ResultsA total of 26/44 patients in the IBP group displayed NPSVVI compared to 11/44 patients in the TBP group (59 vs. 25xa0%; pu2009=u20090.002, Fisher exact test). When adjusted for gender and lead age, the difference was still significant (pu2009=u20090.008). When evaluating the clinical consequence of NPSVVI in this cohort, 3/11 TBP leads with NPSVVI of >0 were eventually extracted due to additional abnormalities vs. 0/26 IBP leads with NPSVVI (pu2009=u20090.02, Fisher exact test). None of the IBP group patients with NPSVVI have developed inappropriate therapy from lead noise or a need for abandonment or extraction.ConclusionIntegrated bipolar ICD leads are more likely to have elevated SIC counts than true bipolar leads despite revealing no other evidence of lead failure. There does not appear to be a need for heightened surveillance in IBP leads with observed elevated SIC counts that have no other findings to suggest lead malfunction.

Reply to Letter

We would first like to thank Drs. Yamada, Osorio, and Kay for their interesting letter regarding our paper on catheter ablation of atrial arrhythmias after cardiac transplantation.1 The case presented in their letter along with the approach used is very interesting.2 We of course agree that in some cases mapping the recipient to donor connection (RDC) might be challenging and not straightforward. We ourselves experienced a challenging case where a patient with RDC tachycardia went from organized flutter to atrial fibrillation to asystole in the recipient heart, which made mapping very challenging. With asystole in the recipient atrium, pacing is needed to create conduction for mapping, and 2:1 conduction from recipient to donor makes it easier to tell which atrium is where.