BACKGROUND:Radiofrequency ablation of intramural ventricular substrate is often limited by insufficient tissue penetration despite high energy settings. As lesion dimensions have a direct and ...negative relationship to impedance, reducing the baseline impedance may increase the ablation effect on deep ventricular tissue.
METHODS:This study included 16 patients with ventricular tachycardia or frequent ventricular premature complexes refractory to ablation with irrigated catheters. After a failed response to radiofrequency ablation, impedance was modulated by adding or repositioning return patches in an attempt to decrease the circuit impedance. Ablation was repeated at a similar location and power settings, and the effect on arrhythmia suppression and adverse effects were evaluated.
RESULTS:Six patients with idiopathic ventricular premature complexes originating from the left ventricular summit (n=4) or papillary muscles (n=2), 6 patients with noninfarct related ventricular tachycardia and 4 patients with infarct-related ventricular tachycardia had unsuccessful response to radiofrequency ablation at critical sites (number of applications10.4±3.1, power42.3±2.9 W, duration55.3±25.5 seconds, impedance reduction14.6±3.5 Ω, low-ionic solution was used in 81.25%). Modulating the return patches resulted in reduced baseline impedance (111.7±8.2 versus 134.7±6.6 Ω, P<0.0001), increased current output (0.6±0.02 versus 0.56±0.02 Amp; P<0.0001) and greater impedance drop (16.8±3.0 Ω, P<0.001). Repeat ablation at similar locations had a successful effect in 12 out of 16 (75.0%) patients. During a follow-up duration of 13±5 months, 10 out of 12 (83.3%) patients remained free of arrhythmia recurrence. The frequency of steam pops was similar between the higher and lower baseline impedance settings (7.1 versus 8.2%; P=0.74).
CONCLUSIONS:In patients with deep ventricular substrate, reducing the baseline impedance is a simple, safe, and effective technique for increasing the effect of radiofrequency ablation. However, its combination with low-ionic solutions may increase the risk for steam pops and neurological events.
We determined the contribution of multiple variables to predict arrhythmic death and total mortality risk in patients with coronary disease and left ventricular dysfunction. We then constructed an ...algorithm to predict risk of mortality and sudden death.
Many factors in addition to ejection fraction (EF) influence the prognosis of patients with coronary disease. However, there are few tools to use this information to guide clinical decisions.
We evaluated the relationship between 25 variables and total mortality and arrhythmic death in 674 patients enrolled in the MUSTT (Multicenter Unsustained Tachycardia Trial) study that did not receive antiarrhythmic therapy. We then constructed risk-stratification algorithms to weight the prognostic impact of each variable on arrhythmic death and total mortality risk.
The variables having the greatest prognostic impact in multivariable analysis were functional class, history of heart failure, nonsustained ventricular tachycardia not related to bypass surgery, EF, age, left ventricular conduction abnormalities, inducible sustained ventricular tachycardia, enrollment as an inpatient, and atrial fibrillation. The model demonstrates that patients whose only risk factor is EF < or =30% have a predicted 2-year arrhythmic death risk <5%.
Multiple variables influence arrhythmic death and total mortality risk. Patients with EF < or =30% but no other risk factor have low predicted mortality risk. Patients with EF >30% and other risk factors may have higher mortality and a higher risk of sudden death than some patients with EF < or =30%. Thus, risk of sudden death in patients with coronary disease depends on multiple variables in addition to EF.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, the scientific objective was to characterize the electrophysiological substrate of the ventricular tachycardia (VT) isthmus during sinus rhythm.
The authors have recently described the ...electrophysiological characteristics of the VT isthmus using a novel in vivo high-resolution mapping technology.
Sixteen swine with healed infarction were studied using high-resolution mapping technology (Rhythmia, Boston Scientific, Cambridge, Massachusetts) in a closed-chest model. The left ventricle was mapped during sinus rhythm and analyzed for activation, conduction velocity, electrogram shape, and amplitude. Twenty-four VTs allowed detailed mapping of the common-channel "isthmus," including the "critical zone." This was defined as the zone of maximal conduction velocity slowing in the circuit, often occurring at entrance and exit from the isthmus caused by rapid angular change in activation vectors.
The VT isthmus corresponded to sites displaying steep activation gradient (SAG) during sinus rhythm with conduction velocity slowing of 58.5 ± 22.4% (positive predictive value PPV 60%). The VT critical zone displayed SAG with greater conduction velocity slowing of 68.6 ± 18.2% (PPV 70%). Critical-zone sites were consistently localized in areas with bipolar voltage ≤0.55 mV, whereas isthmus sites were localized in areas with variable voltage amplitude (1.05 ± 0.80 mV 0.03 to 2.88 mV). Importantly, critical zones served as common-site "anchors" for multiple VT configurations and cycle lengths. Isthmus and critical-zone sites occupied only 18.0 ± 7.0% of the low-voltage area (≤1.50 mV). Isolated late potentials were present in both isthmus and nonisthmus sites, including dead-end pathways (PPV 36%; 95% confidence interval: 34.2% to 39.6%).
The VT critical zone corresponds to a location characterized by SAG and very low voltage amplitude during sinus rhythm. Thus, it allows identification of a re-entry anchor with high sensitivity and specificity. By contrast, voltage and electrogram characteristics during sinus rhythm have limited specificity for identifying the VT isthmus.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Whether echocardiographic markers of remodeling are associated with ventricular tachyarrhythmias is unknown.
The purpose of this study was to determine whether a transthoracic echocardiographic (TTE) ...marker of spherical left ventricular (LV) remodeling is associated with appropriate implantable cardioverter-defibrillator (ICD) therapy in patients with primary prevention ICDs.
From TTE images, we calculated sphericity index (SI), the ratio of biplane LV end-diastolic volume to the volume of a hypothetical sphere with a diameter of the LV end-diastolic length, and examined the relation between SI and therapy for ventricular tachyarrhythmias in 278 patients with primary prevention ICDs and in 50 controls without structural heart disease or ventricular arrhythmias.
SI in normal healthy adult subjects and in subjects receiving ICDs was 0.44 ± 0.02 and 0.65 ± 0.04, respectively (P <.001). Median time to first appropriate ICD therapy was significantly shorter in ICD patients with SI in the upper vs lower 50% of SI values (1.40 vs 2.38 years, P = .02 for conventional ICD patients; 1.54 vs 2.65 years, P = .02 for cardiac resynchronization therapy-defibrillator CRT-D patients). In multivariable Cox regression analysis, SI in the upper 50% was independently associated with appropriate ICD therapy after multivariable adjustment (hazard ratio 2.2, P = .03 for ICD cohort; hazard ratio 4.4, P = .01 for CRT-D cohort). SI was not associated with total mortality in either cohort.
SI is associated with appropriate ICD therapy, but not total mortality, in patients receiving primary prevention ICDs. These observations suggest spherical LV remodeling may predispose to ventricular arrhythmias. Furthermore, SI appears to add predictive accuracy for appropriate ICD therapy in patients with reduced ejection fraction.
Background Primary prevention implantable cardioverter defibrillators (ICDs) reduce all-cause mortality by reducing sudden cardiac death. There are conflicting data regarding whether patients with ...more advanced heart failure (HF) derive ICD benefit owing to the competing risk of non-sudden death. Methods We performed a patient level meta-analysis of New York Heart Association class (NYHA) class II/III HF patients (left ventricular ejection fraction ≤35%) from 4 primary prevention ICD trials (MADIT-I, MADIT-II, DEFINITE, SCD-HeFT). Bayesian–Weibull survival regression models were employed to assess the impact of NYHA class on the relationship between ICD use and mortality. Results Of the 2763 patients who met study criteria, 68% (n = 1867) were NYHA II and 52% (n = 1435) were randomized to an ICD. In a multivariable model including all study patients, the ICD reduced mortality HR 0.65, 95% posterior credibility interval (PCI) 0.40–0.99. The interaction between NYHA class and the ICD on mortality was significant (posterior probability of no interaction = 0.036). In models including an interaction term for the NYHA class and ICD, the ICD reduced mortality among NYHA class II patients (HR 0.55, PCI 0.35–0.85) and the point estimate suggested reduced mortality in NYHA class III patients (HR 0.76, PCI 0.48–1.24) although this was not statistically significant. Conclusions Primary prevention ICDs reduce mortality in NYHA class II patients and trend towards reducing mortality in the heterogeneous group of NYHA class III patients. Improved risk stratification tools are required to guide patient selection and shared decision making among NYHA class III primary prevention ICD candidates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Of the 100,000-plus implantable cardioverter–defibrillators (ICDs) implanted in the United States annually, at least 25% are generator replacements required for depleted batteries. Should all those ...patients be receiving replacement ICDs?
Clinical trials of implantable cardioverter–defibrillators (ICDs) continue to drive expanding indications for these devices.
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More than 100,000 ICDs are implanted in the United States annually. Of these procedures, at least 25% are generator replacements required as a result of depleted battery life.
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Because of the high cost and concern about patient selection, the appropriateness of initial device placement has been closely scrutinized. But there has been little consideration as to what happens in the years after implantation, when ICD batteries drain sufficiently to require replacement, device leads become defective, or systems become infected. Should all these patients receive replacement ICDs? . . .
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