RESUMO
BACKGROUND: The standard deviation of time to peak strain (TPS-SD) has been proposed as an index of left ventricular (LV) dyssynchrony in patients to be resynchronized. However, TPS-SD is sensitive to noise, and the influence of outliers on TPS-SD is also relevant. Alternatively, dyssynchrony can be indexed by temporal uniformity of strain (TUS), whereby a time plot of regional strains, arranged for LV location, is subjected to Fourier analysis. If segments shorten simultaneously (synchronously), the plot appears as a straight line, with power only in the zero-order Fourier term, whereas regionally clustered dyssynchrony generates an undulating plot with higher power in the first-order term. TUS index reflects zero-order relative to first-order plus zero-order power. METHODS: In this study, TUS and TPS-SD were computed in 68 patients (QRS duration >/= 120 ms; ejection fraction = 0.35) in whom longitudinal, circumferential, and radial strains were measured using speckle-tracking two-dimensional echocardiography before and 3 to 6 months after cardiac resynchronization therapy (CRT), together with LV volumes. RESULTS: Following CRT, LV volume decreased (diastolic, -10 +/- 20%) and ejection fraction improved from 0.23 +/- 0.07% to 0.30 +/- 0.10% (P < .001 for both). Circumferential strain was ameliorated as well (P = .054). Two-way analysis of variance revealed TUS improvement after CRT (P = .043), with a trend for CRT to contrast asynchrony at the circumferential (+0.06 +/- 0.25) and longitudinal (+0.05 +/- 0.18) levels compared with the radial level (-0.002 +/- 0.18) (interaction P = .06). This was not true for TPS-SD. Multivariate analysis revealed that only TUS, assessed before CRT circumferentially, predicted ejection fraction improvement after CRT. Other asynchrony variables failed in the model. CONCLUSION: Dyssynchrony indexed by circumferential TUS yields greater CRT benefits than that indexed by TPS-SD, supporting the idea of targeting TUS-measured dyssynchrony as a more informative quantitative measurement in CRT patients.
Assuntos
Algoritmos , Estimulação Cardíaca Artificial/métodos , Ecocardiografia Doppler/métodos , Técnicas de Imagem por Elasticidade/métodos , Interpretação de Imagem Assistida por Computador/métodos , Disfunção Ventricular Esquerda/diagnóstico por imagem , Disfunção Ventricular Esquerda/prevenção & controle , Idoso , Feminino , Humanos , Aumento da Imagem/métodos , Masculino , Pessoa de Meia-Idade , Prognóstico , Análise de Regressão , Reprodutibilidade dos Testes , Estudos Retrospectivos , Sensibilidade e Especificidade , Resultado do TratamentoRESUMO
AIMS: The development of implantable cardioverter-defibrillators (ICDs) with QRS morphology discrimination and dual-chamber sensing capabilities has improved the differentiation of supraventricular from ventricular tachycardias (VTs). Inappropriate ICD discharges may result from extracardiac signals caused by electromagnetic interference (EMI), because of electric fields and leakage currents from domestic or medical electrical devices, damaged sensing leads, and various cardiac and extracardiac signals that mimic VT and/or ventricular fibrillation. The aim of our study was to determine retrospectively the incidence and clinical relevance of these ICD behaviours and offer possible therapeutic solutions. METHODS AND RESULTS: We have observed inappropriate discharges unrelated to supraventricular arrhythmias in 13 (3.9%) of the 336 patients implanted with ICDs in our centre from 1989 to 2005. Seven patients received inappropriate shocks following exposure to external EMI: improperly grounded electric stove, electrically powered watering system, hydro-massage bath, electrical pruner, electrocautery current during cardiac surgery, transcutaneous electric nerve stimulation. In four patients, spurious discharges were related to internal noise of the ICD system from inappropriate lead connections. In two cases, erroneous antitachycardia therapy was delivered following different body signals oversensing (T-wave oversensing, wide QRS double-counting and myopotentials). In nine patients, non-invasive solutions prevented further inappropriate therapies (avoidance of EMI, malfunctioning atrial lead exclusion, ventricular sensing reprogramming). In four patients, surgical revision of the system was required (lead connections or position revision). CONCLUSION: In our experience, inappropriate ICD discharges unrelated to supraventricular arrhythmias occurred in about 4% of ICD patients. A careful evaluation of clinical data and telemetric information (lead impedance, sensed R-wave, stored electrograms) is essential in order to understand the nature of inappropriate ICD discharges and to select the most appropriate solution.
Assuntos
Desfibriladores Implantáveis/efeitos adversos , Taquicardia Supraventricular/etiologia , Idoso , Fenômenos Eletromagnéticos , Falha de Equipamento , Feminino , Humanos , Masculino , Estudos RetrospectivosRESUMO
A case of a patient with an automatic cardioverter defibrillator (ICD) and recurrent ventricular arrhythmic storms related to primary hyperparathyroidism and hypercalcaemia is reported: medical therapy was ineffective and only surgical resection of the parathyroid adenoma resolved this complex clinical condition.