Short QT Syndrome Presenting As Syncope: How Short Is Too Short?

We report the case of a 52-year-old man who presented to our emergency department (ED) after three episodes of syncope in the seven hours before admission. During his stay in the ED he had recurrent ventricular tachycardia (VT) requiring external electrical cardioversion. A 12-lead electrocardiogram (ECG) showed a short QT (SQT) interval (270 ms, QTc 327 ms), with frequent R-on-T extrasystoles triggering sustained polymorphic VT. After exclusion of other precipitating causes, the patient was diagnosed as having SQT syndrome (SQTS) according to the Gollob criteria. To our knowledge, this is the first known documentation of an SQT-caused arrhythmic episode on a 12-lead ECG, as well as the first reported case of SQTS in Portugal. The patient received an implantable cardioverter-defibrillator and was discharged. At a follow-up assessment 14 months later he was symptom-free, interrogation of the device showed no arrhythmic events, and the ECG showed a QT interval of 320 ms (QTc 347 ms).

The Proarrhythmic Effect of Cardiac Resynchronization Therapy: an Issue that Should Be Borne in Mind

The demonstrated benefits of cardiac resynchronization therapy (CRT) in reducing mortality and hospitalizations for heart failure, improving NYHA functional class and inducing reverse remodeling have led to its increasing use in clinical practice. However, its potential contribution to complex ventricular arrhythmias is controversial.We present the case of a female patient with valvular heart failure and severe systolic dysfunction, in NYHA class III and under optimal medical therapy, without previous documented ventricular arrhythmias. After implantation of a CRT defibrillator, she suffered an arrhythmic storm with multiple episodes of monomorphic ventricular tachycardia (VT), requiring 12 shocks. Subsequently, a pattern of ventricular bigeminy was observed, as well as reproducible VT runs induced by biventricular pacing. Since no other vein of the coronary sinus system was accessible, it was decided to implant an epicardial lead to stimulate the left ventricle, positioned in the left ventricular mid-lateral wall. No arrhythmias were detected in the following six months. This case highlights the possible proarrhythmic effect of biventricular pacing with a left ventricular lead positioned in the coronary sinus venous system.

Utilidade do Doppler Tecidular na Predição de Eventos Arrítmicos em Adultos com Tetralogia de Fallot Corrigida

INTRODUCTION: Adults with repaired tetralogy of Fallot (TOF) may be at risk for progressive right ventricular (RV) dilatation and dysfunction, which is commonly associated with arrhythmic events. In frequently volume-overloaded patients with congenital heart disease, tissue Doppler imaging (TDI) is particularly useful for assessing RV function. However, it is not known whether RV TDI can predict outcome in this population. OBJECTIVE: To evaluate whether RV TDI parameters are associated with supraventricular arrhythmic events in adults with repaired TOF. METHODS: We studied 40 consecutive patients with repaired TOF (mean age 35 +/- 11 years, 62% male) referred for routine echocardiographic exam between 2007 and 2008. The following echocardiographic measurements were obtained: left ventricular (LV) ejection fraction, LV end-systolic volume, LV end-diastolic volume, RV fractional area change, RV end-systolic area, RV end-diastolic area, left and right atrial volumes, mitral E and A velocities, RV myocardial performance index (Tei index), tricuspid annular plane systolic excursion (TAPSE), myocardial isovolumic acceleration (IVA), pulmonary regurgitation color flow area, TDI basal lateral, septal and RV lateral peak diastolic and systolic annular velocities (E' 1, A' 1, S' 1, E' s, A' s, S' s, E' rv, A' rv, S' rv), strain, strain rate and tissue tracking of the same segments. QRS duration on resting ECG, total duration of Bruce treadmill exercise stress test and presence of exercise-induced arrhythmias were also analyzed. The patients were subsequently divided into two groups: Group 1--12 patients with previous documented supraventricular arrhythmias (atrial tachycardia, fibrillation or flutter) and Group 2 (control group)--28 patients with no previous arrhythmic events. Univariate and multivariate analysis was used to assess the statistical association between the studied parameters and arrhythmic events. RESULTS: Patients with previous events were older (41 +/- 14 vs. 31 +/- 6 years, p = 0.005), had wider QRS (173 +/- 20 vs. 140 +/- 32 ms, p = 0.01) and lower maximum heart rate on treadmill stress testing (69 +/- 35 vs. 92 +/- 9%, p = 0.03). All patients were in NYHA class I or II. Clinical characteristics including age at corrective surgery, previous palliative surgery and residual defects did not differ significantly between the two groups. Left and right cardiac chamber dimensions and ventricular and valvular function as evaluated by conventional Doppler parameters were also not significantly different. Right ventricular strain and strain rate were similar between the groups. However, right ventricular myocardial TDI systolic (Sa: 5.4+2 vs. 8.5 +/- 3, p = 0.004) and diastolic indices and velocities (Ea, Aa, septal E/Ea, and RV free wall tissue tracking) were significantly reduced in patients with arrhythmias compared to the control group. Multivariate linear regression analysis identified RV early diastolic velocity as the sole variable independently associated with arrhythmic history (RV Ea: 4.5 +/- 1 vs. 6.7 +/- 2 cm/s, p = 0.01). A cut-off for RV Ea of < 6.1 cm/s identified patients in the arrhythmic group with 86% sensitivity and 59% specificity (AUC = 0.8). CONCLUSIONS: Our results suggest that TDI may detect RV dysfunction in patients with apparently normal function as assessed by conventional echocardiographic parameters. Reduction in RV early diastolic velocity appears to be an early abnormality and is associated with occurrence of arrhythmic events. TDI may be useful in risk stratification of patients with repaired tetralogy of Fallot.

Tratamento Cirúrgico dos Defeitos do Septo Auriculo-Ventricular. Experiência Uni-Institucional

OBJECTIVES: Atrio-ventricular septal (AVSD) defects include a variable spectrum of congenital malformations with different forms of clinical presentation. We report the surgical results, from a single institution, with this type of congenital cardiac malformation. Patients with hypoplasia of one of the ventricles were excluded from this analysis. POPULATION: Between November of 1998 and June of 2005, 49 patients with AVSD were operated on by the same team and in the same department. The average age was 37.3 months (medium 6 months) and 31 patients were female. In 38 patients (78%) an inter-ventricular communication was present (AVSD-complete) and of these, 26 were of the type A of Rastelli, being 13 of type B or C. The age for defect correction of the complete form was of 5.5 months, palliative surgery was not carried out on any of the patients. Associated lesions included: Down's syndrome in 22 patients (45%), patent arterial duct in 17 patients (35%), severe AV regurgitation in 4 patients (8%), tetralogy of Fallot in two (4%) and sub-aortic stenosis in one patient (2%). Pre-operatively 10 patients presented severe congestive heart failure and two were mechanically ventilated. RESULTS: Complete biventricular correction was carried out in all patients. The average time on bypass (ECC) was 74.1+/-17.5 min. and time of aortic clamping was 52.0+/-12.9 min. The complete defects were corrected by the double patch technique, and in all patients the mitral cleft was closed, except in two with single papillary muscle. There was no intra-operative mortality, but hospital mortality was 8%(4 patients), due to pulmonary hypertension crises, in the first 15 post-operative days. The mean ventilation time was of 36.5+/-93 hours (medium 7 h) and the average ICU stay was of 4.3+/-4.8 days (medium 3 days). The minimum follow-up period is 1 month and the maximum is 84 months (medium 29.5 months), during which time 4 re-operations (8%) took place: two for residual VSD's and two for mitral regurgitation. There was no mortality at re-do surgery. At follow up there was residual mitral regurgitation, mild in 17 patients and moderate in two. Four other patients presented with minor residual defects. CONCLUSIONS: The complete correction of AVSD can be carried out with acceptable results, in a varied spectrum of anatomic forms and of clinical severity. Despite the age of correction, for the complete forms, predominantly below 12 months, pulmonary hypertension was the constant cause for post operative mortality. Earlier timing of surgery and stricter peri-operative control might still improve results.

Assistência Ventricular em Crianças

Descreve-se a utilização de um sistema de assistência mecânica bi-ventricular, para-corpórea (Berlin Heart), como ponte para transplante, numa criança de dois anos, sofrendo de miocardiopatia dilatada. O período de assistência durou três meses e meio e o transplante foi bem sucedido. Descreve-se o caso clínico, os protocolos usados e revêem-se as indicações, as técnicas e os problemas com a assistência ventricular mecânica em crianças.

Dispersão da Refractariedade Auricular como Substrato Electrofisiológico da Vulnerabilidade Auricular em Doentes com Fibrilhação Auricular Paroxística

Atrial electrical remodeling plays a part in recurrence of atrial fibrillation (AF). It has been related to an increase in heterogeneity of atrial refractoriness that facilitates the occurrence of multiple reentry wavelets and vulnerability to AF. AIM: To examine the relationship between dispersion of atrial refractoriness (Disp_A) and vulnerability to AF induction (A_Vuln) in patients with clinical paroxysmal AF (PAF). METHODS: Thirty-six patients (22 male; age 55+/-13 years) with > or =1 year of history of PAF (no underlying structural heart disease--n=20, systemic hypertension--n=14, mitral valve prolapse--n=1, surgically corrected pulmonary stenosis--n=1), underwent electrophysiological study (EPS) while off medication. The atrial effective refractory period (AERP) was assessed at five different sites--high (HRA) and low (LRA) lateral right atrium, high interatrial septum (IAS), proximal (pCS) and distal (dCS) coronary sinus--during a cycle length of 600 ms. AERP was taken as the longest S1-S2 interval that failed to initiate a propagation response. Disp_A was calculated as the difference between the longest and shortest AERP. A_Vuln was defined as the ability to induce AF with 1-2 extrastimuli or with incremental atrial pacing (600-300 ms) from the HRA or dCS. The EPS included analysis of focal electrical activity based on the presence of supraventricular ectopic beats (spontaneous or with provocative maneuvers). The patients were divided into group A--AF inducible (n=25) and group B--AF not inducible (n=11). Disp_A was analyzed to determine any association with A_Vuln. Disp_A and A_Vuln were also examined in those patients with documented repetitive focal activity. Logistic regression was used to determine any association of the following variables with A_Vuln: age, systemic hypertension, left ventricular hypertrophy, left atrial size, left ventricular function, duration of PAF, documented atrial flutter/tachycardia and Disp_A. RESULTS: There were no significant differences between the groups with regard to clinical characteristics and echocardiographic data. AF was inducible in 71% of the patients and noninducible in 29%. Group A had greater Disp_A compared to group B (105+/-78 ms vs. 49+/-20 ms; p=0.01). Disp_A was >40 ms in 50% of the patients without A_Vuln and in 91% of those with A_Vuln (p=0.05). Focal activity was demonstrated in 14 cases (39%), 57% of them with A_Vuln. Disp_A was 56+/-23 ms in this group and 92+/-78 ms in the others (p=0.07). Using logistic regression, the only predictor of A_Vuln was Disp_A (p=0.05). CONCLUSION: In patients with paroxysmal AF, Disp_A is a major determinant of A_Vuln. Nevertheless, the degree of nonuniformity of AERP appears to be less important as an electrophysiological substrate for AF due to focal activation.

Inducibility of Atrial Fibrillation During Electrophysiologic Evaluation is Associated with Increased Dispersion of Atrial Refractoriness

The impact of atrial dispersion of refractoriness (Disp_A) in the inducibility and maintenance of atrial fibrillation (AF) has not been fully resolved. AIM: To study the Disp_A and the vulnerability (A_Vuln) for the induction of self-limited (<60 s) and sustained episodes of AF. METHODS AND RESULTS: Forty-seven patients with paroxysmal AF (PAF): 29 patients without structural heart disease and 18 with hypertensive heart disease. Atrial effective refractory period (ERP) was assessed at five sites--right atrial appendage and low lateral right atrium, high interatrial septum, proximal and distal coronary sinus. We compared three groups: group A - AF not inducible (n=13); group B - AF inducible, self-limited (n=18); group C - AF inducible, sustained (n=16). Age, lone AF, hypertension, left atrial and left ventricular (LV) dimensions, LV systolic function, duration of AF history, atrial flutter/tachycardia, previous antiarrhythmics, and Disp_A were analysed with logistic regression to determine association with A_Vuln for AF inducibility. The ERP at different sites showed no differences among the groups. Group A had a lower Disp_A compared to group B (47+/-20 ms vs 82+/-65 ms; p=0.002), and when compared to group C (47+/-20 ms vs 80+/-55 ms; p=0.008). There was no significant difference in Disp_A between groups B and C. By means of multivariate regression analysis, the only predictor of A_Vuln was Disp_A (p=0.04). Conclusion: In patients with PAF, increased Disp_A represents an electrophysiological marker of A_Vuln. Inducibility of both self-limited and sustained episodes of AF is associated with similar values of Disp_A. These findings suggest that the maintenance of AF is influenced by additional factors.

Incidência de Arritmias Ventriculares em Doentes com Disfunção Sistólica Ventricular Esquerda Grave: Existe Benefício Após Terapêutica de Ressincronização Cardíaca

Introdução: A terapêutica de ressincronização cardíaca (TRC) tem benefícios significativos em doentes seleccionados. O impacto desta modalidade na incidência de taquidisritmias ventriculares permanece controverso. Analisámos a ocorrência de terapêuticas apropriadas em doentes submetidos a TRC combinada com cardioversor-desfibrilhador (CDI). Métodos: Estudo de 123 doentes com fracção de ejecção ventricular esquerda (FEVE) < 35%, submetidos a implantação com sucesso de TRC-CDI ou CDI isoladamente (prevenção primária). Resultados: Idade média foi 63±12 anos, FEVE de 25±6%, seguimento mediano de 372 dias. Implantou-se TRC-CDI em 63 doentes (grupo A) e CDI isoladamente em 60 doentes (grupo B). No grupo A tivemos 86% de respondedores clínicos, menor prevalência de miocardiopatia isquémica(30% versus 72%), e mais doentes em classe III da NYHA antes da implantação do dispositivo(90% versus 7%) comparativamente com o grupo com CDI isoladamente. Não se identificaram diferenças relativamente à incidência de terapêuticas apropriadas (19% versus 12%) ou no tempo para a primeira terapêutica (305 dias versus 293 dias). A mortalidade total foi de 11% no grupo A e de 12% no grupo B. As curvas de Kaplan-Meier para eventos arrítmicos em doentes com TRC, não mostraram diferenças significativas (HR 3,02, IC 95% 0,82-11,09, p = NS) comparativamente com doentes sem TRC. Conclusões: Em doentes submetidos a TRC-CDI por prevenção primária, apesar da elevada taxa de respondedores, a incidência de terapêuticas apropriadas não foi diferente do obtido em doentes com CDI isoladamente.

Bloqueio Aurículo-Ventricular de Alto Grau Induzido por Angina de Prinzmetal

Apresentamos o caso de uma mulher de 46 anos com episódios frequentes de dor precordial e síncope associados a elevação do segmento ST e períodos de bloqueio aurículoventricular de alto grau transitórios. A coronariogafia excluiu lesões significativas e a doente foi tratada com nitratos e antagonistas do cálcio. Verificou-se persistência da sintomatologia associada a períodos de bloqueio aurículo-ventricular sintomáticos, refratários a otimização terapêutica. Implantação de pacemaker DDD-R. Follow-up de 4 meses sem intercorrências.

Taquicardia Juncional Recíproca Permanente: uma Taquicardia Incessante da Infância

A taquicardia juncional recíproca permanente é uma forma de taquicardia supraventricular de reentrada pouco comum, embora constitua a causa mais frequente de taquicardia incessante em crianças. O seu carácter permanente causa disfunção ventricular esquerda e miocardiopatia dilatada e é de difícil controlo terapêutico. Objectivo: Rever as características clínicas mais significativas desta arritmia, a sua evolução e as opções terapêuticas actuais. Métodos: estudo retrospectivo, analisando a forma de apresentação e evolução, com particular relevo para a resposta à terapêutica farmacológica e alternativas terapêuticas. Doentes: Grupo de 5 doentes com o diagnóstico de taquicardia juncional recíproca permanente. Resultados: As crianças estudadas tinham idades compreendidas entre os 14 dias e os 12 anos. Três encontravam-se assintomáticas. O primeiro ecocardiograma demonstrou dilatação do ventrículo esquerdo e diminuição da fracção de encurtamento em uma das crianças. A terapêutica farmacológica foi inicialmente eficaz em todos os casos. Ao longo do seguimento (0,2-4,5 anos) a arritmia tornou-se refractária em um dos casos, pelo que se procedeu a ablação da via anómala por radiofrequência. Conclusões: A taquicardia juncional recíproca permanente tem diversas formas de apresentação. A terapêutica farmacológica é recomendada, mas tem carácter transitório. A ablação por radiofrequência é o tratamento definitivo, estando condicionada pela idade dos doentes.

Time to Left Ventricular Reverse Remodeling after Cardiac Resynchronization Therapy: Better Late than Never

INTRODUCTION: Left ventricular reverse remodeling (LVRR), defined as reduction of end-diastolic and end-systolic dimensions and improvement of ejection fraction, is associated with the prognostic implications of cardiac resynchronization therapy (CRT). The time course of LVRR remains poorly characterized. Nevertheless, it has been suggested that it occurs ≤6 months after CRT. OBJECTIVE: To characterize the long-term echocardiographic and clinical evolution of patients with LVRR occurring >6 months after CRT and to identify predictors of a delayed LVRR response. METHODS: A total of 127 consecutive patients after successful CRT implantation were divided into three groups according to LVRR response: Group A, 19 patients (15%) with LVRR after >6 months (late LVRR); Group B, 58 patients (46%) with LVRR before 6 months (early LVRR); and Group C, 50 patients (39%) without LVRR during follow-up (no LVRR). RESULTS: The late LVRR group was older, more often had ischemic etiology and fewer patients were in NYHA class ≤II. Overall, group A presented LVRR between group B and C. This was also the case with the percentage of clinical response (68.4% vs. 94.8% vs. 38.3%, respectively, p<0.001), and hospital readmissions due to decompensated heart failure (31.6% vs. 12.1% vs. 57.1%, respectively, p<0.001). Ischemic etiology (OR 0.044; p=0.013) and NYHA functional class