The association of standard 12-lead electrocardiogram (ECG) markers with benefits of the primary prophylactic implantable cardioverter-defibrillator (ICD) has not been determined in the contemporary ...era. We analysed traditional and novel ECG variables in a large prospective, controlled primary prophylactic ICD population to assess the predictive value of ECG in terms of ICD benefit.
Electrocardiograms from 1477 ICD patients and 700 control patients (EU-CERT-ICD; non-randomized, controlled, prospective multicentre study; ClinicalTrials.gov Identifier: NCT02064192), who met ICD implantation criteria but did not receive the device, were analysed. The primary outcome was all-cause mortality. In ICD patients, the co-primary outcome of first appropriate shock was used. Mean follow-up time was 2.4 ± 1.1 years to death and 2.3 ± 1.2 years to the first appropriate shock. Pathological Q waves were associated with decreased mortality in ICD patients hazard ratio (HR) 0.54, 95% confidence interval (CI) 0.35-0.84; P < 0.01 and patients with pathological Q waves had significantly more benefit from ICD (HR 0.44, 95% CI 0.21-0.93; P = 0.03). QTc interval increase taken as a continuous variable was associated with both mortality and appropriate shock incidence, but commonly used cut-off values, were not statistically significantly associated with either of the outcomes.
Pathological Q waves were a strong ECG predictor of ICD benefit in primary prophylactic ICD patients. Excess mortality among Q wave patients seems to be due to arrhythmic death which can be prevented by ICD.
Objective: This study evaluated the prognostic significance of cardiac magnetic resonance myocardial feature tracking (CMR-FT) in patients with Brugada syndrome (BrS) to detect subclinical ...alterations and predict major adverse events (MAE). Methods: CMR was performed in 106 patients with BrS and 25 healthy controls. Biventricular global strain analysis was assessed using CMR-FT. Patients were followed over a median of 11.6 8.8 ± 13.8 years. Results: The study cohort was subdivided according to the presence of a spontaneous type 1 ECG (sECG) into sBrS (BrS with sECG, n = 34 (32.1%)) and diBrS (BrS with drug-induced type 1 ECG, n = 72 (67.9%)). CMR-FT revealed morphological differences between sBrS and diBrS patients with regard to right ventricular (RV) strain (circumferential (%) (sBrS −7.9 ± 2.9 vs diBrS - 9.5 ± 3.1, p = 0.02) and radial (%) (sBrS 12.0 ± 4.3 vs diBrS 15.4 ± 5.4, p = 0.004)). During follow-up, MAE occurred in 11 patients (10.4%). Multivariable analysis was performed to identify independent predictors for the occurrence of events during follow-up. The strongest predictive value was found for RV circumferential strain (OR 3.2 (95% CI 1.4 - 6.9), p = 0.02) and RVOT/BSA (OR 3.1 (95% CI 1.0 - 7.0), p = 0.03). Conclusions: Myocardial strain analysis detected early subclinical alterations, prior to apparent changes in myocardial function, in patients with BrS. While usual functional parameters were within the normal range, CMR-FT revealed pathological results in patients with an sECG.Moreover, RV circumferential strain and RVOT size provided additional prognostic information on the occurrence of MAE during follow-up, which reflects electrical vulnerability.
This study evaluated the prognostic significance of cardiac magnetic resonance myocardial feature tracking (CMR-FT) in patients with Brugada syndrome (BrS) to detect subclinical alterations and ...predict major adverse events (MAE).
CMR was performed in 106 patients with BrS and 25 healthy controls. Biventricular global strain analysis was assessed using CMR-FT. Patients were followed over a median of 11.6 8.8 ± 13.8 years.
The study cohort was subdivided according to the presence of a spontaneous type 1 ECG (sECG) into sBrS (BrS with sECG, n = 34 (32.1%)) and diBrS (BrS with drug-induced type 1 ECG, n = 72 (67.9%)). CMR-FT revealed morphological differences between sBrS and diBrS patients with regard to right ventricular (RV) strain (circumferential (%) (sBrS −7.9 ± 2.9 vs diBrS - 9.5 ± 3.1, p = 0.02) and radial (%) (sBrS 12.0 ± 4.3 vs diBrS 15.4 ± 5.4, p = 0.004)). During follow-up, MAE occurred in 11 patients (10.4%). Multivariable analysis was performed to identify independent predictors for the occurrence of events during follow-up. The strongest predictive value was found for RV circumferential strain (OR 3.2 (95% CI 1.4 - 6.9), p = 0.02) and RVOT/BSA (OR 3.1 (95% CI 1.0 - 7.0), p = 0.03).
Myocardial strain analysis detected early subclinical alterations, prior to apparent changes in myocardial function, in patients with BrS. While usual functional parameters were within the normal range, CMR-FT revealed pathological results in patients with an sECG.
Moreover, RV circumferential strain and RVOT size provided additional prognostic information on the occurrence of MAE during follow-up, which reflects electrical vulnerability.
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Noncontact Verification of Linear Lesions. Introduction: Creation of linear lesions is an established ablation goal. Verification of complete conduction block at the ablation line is required to ...determine ablation success. Conventional mapping techniques are sequential endocardial activation mapping and documentation of double potentials. Recently, a noncontact multielectrode array catheter was developed that allows instantaneous three‐dimensional mapping by simultaneous reconstruction of > 3, 000 electrograms. In this study, we prospectively compared the accuracy of noncontact mapping to identify discontinuities in linear lesions and to verify a conduction block with that of conventional mapping techniques.
Methods and Results: In 12 patients with atrial flutter, radiofrequency pulses were applied between the tricuspid annulus and either the inferior vena cava or the eustachian ridge. Following each application, pulse propagation at the ablation line was determined during pacing by conventional mapping techniques. The findings were compared to high‐density isopotential mapping using the noncontact multielectrode array catheter. It was found that noncontact mapping reliably distinguished conduction delays from a conduction block as defined by contact mapping. In addition, noncontact mapping instantaneously identified the area where a discontinuity in the line of block was present. In these patients, complete conduction block was achieved by radiofrequency pulses guided by the noncontact mapping system.
Conclusion: Noncontact mapping is highly accurate in distinguishing conduction delays from a complete conduction block. By providing an instantaneous high‐density propagation vector at all sites along the ablation line, three‐dimensional isopotential mapping is helpful in localizing discontinuities of linear lesions and, thus, may facilitate the creation of a complete conduction block.
Chronic atrial fibrillation (AF), which is refractory to external electrical direct current shock and/or pharmacologic cardioversion, may be successfully cardioverted using internal atrial ...defibrillation. To avoid unnecessary procedures, it is important to be able to predict which patients will revert to AF. Thirty-eight patients with chronic AF underwent successful internal atrial defibrillation and were followed for 6 months after restoration of sinus rhythm. Left atrial (LA) diameter, left ventricular ejection fraction, maximum LA appendage area, and peak emptying velocities of the LA appendage were analyzed to determine which of these factors were associated with recurrence of AF. Forty-nine percent of patients had a recurrence of AF within 6 months following internal atrial defibrillation. The preprocedural ejection fraction (mean ± SD 59 + 14% vs 57 + 13%, p = 0.63), LA diameter (4.2 ± 0.6 cm vs 4.5 ± 0.6 cm, p = 0.16), and LA appendage area (5.0 ± 1.5 cm
2 vs 5.8 ± 1.5 cm
2, p = 0.13) did not differ significantly between patients who maintained sinus rhythm and those who had recurrence of AF. Peak emptying velocities of the LA appendage before cardioversion were significantly lower in patients with recurrence of AF compared with patients who maintained sinus rhythm (0.26 ± 0.1 m/s vs 0.49 ± 0.17 m/s, p = 0.001). A peak emptying velocity <0.36 had a sensitivity of 82% and a specificity of 83% for predicting recurrence of AF.
The purpose of this study was to compare the effect of intravenous flecainide and ajmaline with respect to their ability to induce or accentuate the typical ECG pattern of Brugada syndrome.
Brugada ...syndrome is associated with a high incidence of sudden cardiac death. The typical ECG pattern of ST-segment elevation in the right precordial leads often is concealed, but it can be unmasked with sodium channel blockers such as flecainide and ajmaline. Little is known about the relative effectiveness of these provocative agents in unmasking Brugada syndrome.
Intravenous pharmacologic challenge with flecainide and ajmaline was performed. Whole-cell patch clamp techniques were used to assess the relative potency of ajmaline and flecainide to inhibit the transient outward current (I(to)).
A coved-type ST-segment elevation in the right precordial leads was induced or enhanced in 22 of 22 patients following ajmaline administration. Among the 22 patients, only 15 patients showed positive response to flecainide, resulting in a positive concordance of 68%. Both drugs produced equivalent changes in QRS and PQ intervals, suggesting similar effects on sodium channel current. Whole-cell patch clamp experiments revealed a reduction of the total charge provided by I(to) with an IC(50) of 216 and 15.2 microM for ajmaline and flecainide, respectively.
Our data demonstrate disparate response of Brugada patients to flecainide and ajmaline, with a failure of flecainide in 7 of 22 cases (32%). Greater inhibition of I(to) by flecainide may render it less effective. These observations have important implication for identification of patients at risk for sudden death.
Introduction: The principal aim of this study was to assess the efficacy of quinidine in suppressing IKr in vitro and in modulating the rate dependence of the QT interval in the “SQT1” form of the ...short QT syndrome.
Methods and Results: Graded‐intensity bicycle exercise testing was performed off drug in three patients and during oral quinidine in two patients with short QT syndrome and compared to a control group of healthy normal subjects. The in vitro effects of quinidine on currents in patch clamp technique were investigated. Off drugs QTpV3/heart rate correlation is much weaker in patients with short QT syndrome, and QTpV3 shortens less with heart rate increase compared to normal subjects. In addition to prolonging the QT interval into the normal range, quinidine restored the heart rate dependence of the QT interval toward a range of adaptation reported for normal subjects. Data from heterologous expression of wild‐type and mutant HERG genes indicate the mutation causes a 20‐fold increase in IC50 of d‐sotalol but only a 5.8‐fold increase in IC50 of quinidine.
Conclusion: Oral quinidine is effective in suppressing the gain of function in IKr responsible for some cases of short QT syndrome with a mutation in HERG and thus restoring normal rate dependence of the QT interval and rendering ventricular tachycardia/ventricular fibrillation noninducible.
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