EpCAM y obstrucción microvascular en pacientes con un IAMCEST: estudio con resonancia magnética cardiaca / EpCAM and microvascular obstruction in patients with STEMI: a cardiac magnetic resonance study

Introducción y objetivos: La obstrucción microvascular (OMV) se asocia negativamente con la estructura cardiaca y el pronóstico de los pacientes tras un infarto agudo de miocardio con elevación del segmento ST (IAMCEST). El factor epithelial cell adhesion molecule (EpCAM), implicado en la cohesión de las células epiteliales, está poco estudiado en el contexto de la OMV. Por ello, el objetivo de este estudio es evaluar en una cohorte de pacientes con IAMCEST la asociación entre la concentración de EpCAM circulante con la extensión de la OMV, determinada por resonancia magnética cardiaca (RMC), y la función sistólica en fases crónicas. Métodos: Se incluyó prospectivamente a 106 pacientes con un primer IAMCEST tratados con angioplastia primaria percutánea. La concentración sérica de EpCAM se determinó 24h tras la reperfusión coronaria. Se estudió a todos los pacientes mediante RMC a la semana y a los 6 meses del IAMCEST. Se evaluó la correlación entre los valores de EpCAM circulante con la OMV, los índices de función sistólica y la fracción de eyección del ventrículo izquierdo. Resultados: La media de edad de la cohorte era 59±13 años y el 76% eran varones. Se dicotomizó a los pacientes según la mediana de EpCAM (4,48 pg/ml). Se observó que los pacientes que tenían valores más bajos de EpCAM presentaban una mayor extensión de la OMV (p=0,021) y un mayor tamaño de infarto (p=0,019) en los estudios de RMC realizados 1 semana después del evento cardiovascular. Respecto a las variables de presentación, la concentración de EpCAM se asoció significativamente con la presencia de OMV en análisis de regresión logística binaria univariable (OR=0,58; IC95%, 0,38-0,88; p=0,011) y multivariable (OR=0,55; IC95%, 0,35-0,87; p=0,010). A pesar de que la OMV tiende a resolverse espontáneamente en fases crónicas, unos valores más bajos de EpCAM se correlacionaron con una peor función sistólica (AU)

Introduction and objectives: Microvascular obstruction (MVO) is negatively associated with cardiac structure and worse prognosis after ST-segment elevation myocardial infarction (STEMI). Epithelial cell adhesion molecule (EpCAM), involved in epithelium adhesion, is an understudied area in the MVO setting. We aimed to determine whether EpCAM is associated with the appearance of cardiac magnetic resonance (CMR)-derived MVO and long-term systolic function in reperfused STEMI. Methods: We prospectively included 106 patients with a first STEMI treated with percutaneous coronary intervention, quantifying serum levels of EpCAM 24hours postreperfusion. All patients underwent CMR imaging 1 week and 6 months post-STEMI. The independent correlation of EpCAM with MVO, systolic volume indices, and left ventricular ejection fraction was evaluated. Results: The mean age of the sample was 59±13 years and 76% were male. Patients were dichotomized according to median EpCAM (4.48 pg/mL). At 1-week CMR, lower EpCAM was related to extensive MVO (P=.021) and larger infarct size (P=.019). At presentation, EpCAM values were significantly associated with the presence of MVO in univariate (OR, 0.58; 95%CI, 0.38-0.88; P=.011) and multivariate logistic regression models (OR, 0.55; 95%CI, 0.35-0.87; P=.010). Although MVO tends to resolve at chronic phases, decreased EpCAM was associated with worse systolic function: reduced left ventricular ejection fraction (P=.009) and higher left ventricular end-systolic volume (P=.043). Conclusions: EpCAM is associated with the occurrence of CMR-derived MVO at acute phases and long-term adverse ventricular remodeling post-STEMI

Resonancia magnética cardiaca de estrés para predecir mortalidad y toma de decisiones: registro de 2.496 pacientes mayores con síndrome coronario crónico / Stress cardiac magnetic resonance for mortality prediction and decision-making: registry of 2496 elderly patients with chronic coronary syndrome

Introducción y objetivos: El tratamiento del paciente mayor con síndrome coronario crónico (SCC) es un reto. Se exploró el valor pronóstico y la utilidad para la toma de decisiones de la carga isquémica determinada mediante resonancia magnética cardiaca (RMC) de estrés con vasodilatador en pacientes mayores con SCC. Métodos: Se incluyó a 2.496 pacientes mayores de 70 años estudiados con una RMC de estrés con vasodilatador por SCC conocido o sospechado. La carga isquémica (número de segmentos con déficit de perfusión inducido por el estrés) se calculó siguiendo el modelo de 17 segmentos. Posteriormente se analizó de manera retrospectiva su asociación con la mortalidad por cualquier causa y el efecto de la revascularización guiada por la RMC. Resultados: Durante una mediana de seguimiento de 4,58 años, se registraron 430 muertes (17,2%). Una mayor carga isquémica fue un predictor independiente de mortalidad: razón de riesgos, 1,04; intervalos de confianza del 95%, 1,01-1,07 por cada segmento adicional isquémico; p=0,006). Esta asociación también ocurrió en los mayores de 80 años y en las mujeres (p<0,001). Se detectó una interacción entre la revascularización y la mortalidad hacia un efecto deletéreo a baja carga isquémica y un efecto protector en caso de isquemia grave. Conclusiones: La RMC de estrés es un valioso instrumento para la estratificación del riesgo de los pacientes de edad avanzada con SCC y puede contribuir a guiar la toma de decisiones en este contexto (AU)

Introduction and objectives: The management of elderly patients with chronic coronary syndrome (CCS) is challenging. We explored the prognostic value and usefulness for decision-making of ischemic burden determined by vasodilator stress cardiac magnetic resonance (CMR) imaging in elderly patients with known or suspected CCS. Methods: The study group comprised 2496 patients older than 70 years who underwent vasodilator stress CMR for known or suspected CCS. The ischemic burden (number of segments with stress-induced perfusion deficit) was calculated following the 17-segment model. Subsequently, we retrospectively analyzed its association with all-cause mortality and the effect of CMR-guided revascularization. Results: During a median follow-up of 4.58 years, there were 430 deaths (17.2%). A higher ischemic burden was an independent predictor of mortality (HR, 1.04; 95%CI, 1.01-1.07 for each additional ischemic segment; P=.006). This association was also found in patients older than 80 years and in women (P <.001). An interaction between revascularization and mortality was detected toward deleterious consequences at low ischemic burden and a protective effect in patients with extensive ischemia. Conclusions: Vasodilator stress CMR is a valuable tool to stratify risk in elderly patients with CCS and might be helpful to guide decision-making in this scenario (AU)

Prognostic and therapeutic implications of dipyridamole stress cardiovascular magnetic resonance on the basis of the ischaemic cascade.

OBJECTIVE: To determine the prognostic and therapeutic implications of stress perfusion cardiovascular magnetic resonance (CMR) on the basis of the ischaemic cascade. SETTING: Single centre study in a teaching hospital in Spain. PATIENTS: Dipyridamole stress CMR was performed on 601 patients with ischaemic chest pain and known or suspected coronary artery disease. On the basis of the ischaemic cascade, patients were categorised in C1 (no evidence of ischaemia, n = 354), C2 (isolated perfusion deficit at stress first-pass perfusion imaging, n = 181) and C3 (simultaneous perfusion deficit and inducible wall motion abnormalities, n = 66). CMR-related revascularisation (n = 102, 17%) was defined as the procedure prompted by the CMR results and carried out within the next three months. RESULTS: During a median follow-up of 553 days, 69 major adverse cardiac events (MACE), including 21 cardiac deaths, 14 non-fatal myocardial infarctions and 34 admissions for unstable angina with documented abnormal angiography were detected. In non-revascularised patients (n = 499), the MACE rate was 4% (14/340) in C1, 20% (26/128) in C2 and 39% (12/31) in C3 (adjusted p value = 0.004 vs C2 and <0.001 vs C1). CMR-related revascularisation had neutral effects in C2 (20% vs 19%, 1.1 (0.5 to 2.4), p = 0.7) but independently reduced the risk of MACE in C3 (39% vs 11%, 0.2 (0.1 to 0.7), p = 0.01). CONCLUSIONS: Dypiridamole stress CMR is able to stratify risk on the basis of the ischaemic cascade. A small group of patients with severe ischaemia-simultaneous perfusion deficit and inducible wall motion abnormalities-are at the highest risk and benefit most from MACE reduction due to revascularisation.

Relationships between heart rate variability, functional capacity, and left ventricular function following myocardial infarction: an evaluation after one week and six months.

BACKGROUND: Relationships between heart rate (HR) variability and different prognostic markers such as ejection fraction, functional capacity, and patency of the infarct-related artery, as well as the comparison of their time courses are not fully elucidated. HYPOTHESIS: The aim of study was to assess prospectively the early postinfarction changes in HR variability and its evolution over a period of 6 months: the relationships between HR variability and functional capacity in exercise testing; left ventricular function in cardiac catheterization: status of the infarct-related artery; and the comparison of their time courses. METHODS: In 42 patients with anterior myocardial infarction, a study was made of the early changes in HR variability analyzed by the complex demodulation method, its evolution over a period of 6 months. and the relationships between HR variability and (1) functional capacity in exercise testing, (2) left ventricular function in cardiac catheterization, and (3) status of the infarct-related artery. RESULTS: At 1 week HR variability parameters correlated directly with functional capacity indicators such as METS, percent change in HR from rest to peak exercise (%deltaHR), difference between initial and peak HR (HR range), percent peak theoretical HR (% peak HR), left ventricular ejection fraction (EF), and, inversely, with end-systolic volume (ESV). Stepwise multiple regression analysis to establish HR variability parameters (recorded at 1 week) as related to functional capacity and left ventricular function at 1 week and 6 months postinfarction established the following variables: (1) At 1 week: standard deviation (SD) of the RR cycles in relation to %deltaHR (r = 0.60, p <0.0001), HR range (r = 0.43, p < 0.01), and EF (r = 0.79, p < 0.0001). (2) At 6 months, the sole accepted HR variability parameter was the SD in relation to %deltaHR (r = 0.38, p < 0.05) and HR range (r = 0.45, p < 0.01). No variability parameter was accepted in relation to METS, % peak HR, or ESV. Relationship between EF or ESV and HR variability parameters was not significant when both were evaluated at 6 months. At that time, there was a significant increase in all HR variability parameters among all surviving patients (n = 39), with the exception of the LF/HF ratio and mean RR cycle. The percent increase in HR variability between the first week and 6 months was greater among those patients with the lowest basal EF. No relation was established between HR variability and patency of the infarct-related artery. CONCLUSION: The decrease in HR variability observed following myocardial infarction is associated with a diminished functional capacity and an increased alteration of the EF. This does not affect the recovery of HR variability, which was observed in all surviving patients.

Anticoagulant therapy modifies fibrinolytic dysfunction in chronic atrial fibrillation.

OBJECTIVE: We evaluated the changes in fibrinolytic activation markers before starting anticoagulation, at 1 and 6 months following the introduction of anticoagulant therapy. DESIGN AND METHODS: Tissue plasminogen activator (t-PA), its endothelial inhibitor (PAI-1), plasmin:antiplasmin complexes (PAPc), modified antithrombin III (ATM), D dimer (D-D) and fibrinogen (FIB) were measured in 36 patients with chronic atrial fibrillation. Fifteen of them had rheumatic mitral stenosis and 21 had nonrheumatic atrial fibrillation. Basal levels were compared with a sex- and age-matched healthy control group. RESULTS: At baseline, patients with atrial fibrillation showed significantly higher plasma levels of PAI-1, ATM, D-D and FIB levels (p < 0.05) than controls, and no differences in t-PA and PAPc concentrations. Levels of t-PA, PAI-1, ATM and D-D decreased significantly under anticoagulant therapy, whereas FIB levels were not significantly modified. PAPc levels were significantly increased at 6 months in the rheumatic group but did not differ significantly in the nonrheumatic group. CONCLUSIONS: Patients with chronic atrial fibrillation show a hypercoagulant state and a relatively low fibrinolytic function. After 6 months of anticoagulant therapy, an improvement in fibrinolytic function markers was detected.

Changes in left ventricular filling pattern during dobutamine stress Doppler echocardiography.

AIMS: To study the left ventricular filling pattern during stress Doppler echocardiography and its utility in the detection of myocardial ischaemia. METHODS AND RESULTS: Fifty-seven consecutive patients underwent dobutamine stress echocardiography. The left ventricular filling pattern (E-wave velocity; A-wave velocity; E/A ratio; E-wave deceleration time) was analysed at baseline and at maximum heart rate reached. The percentage increase in these parameters from baseline to peak heart rate was also determined. Myocardial ischaemia (regional contractility worsening) was induced in 19 cases (ischaemic group) but not in 38 cases (non-ischaemic group). There were no differences between both groups at baseline. E-wave deceleration time decreased in the non-ischaemic group (197+/-63 vs. 167+/-65 ms, P=0.01) and increased in the ischaemic group (203+/-42 vs. 315+/-135 ms, P<0.0001). A percentage increase in E-wave deceleration time of >30% showed a positive predictive value of 93% and a negative predictive value of 86% for detecting ischaemia, and in the multivariate analysis it was the only Doppler parameter (P<0.0001) that predicted the induction of ischaemia. CONCLUSION: We conclude that myocardial ischaemia provokes an increase in E-wave deceleration time. Analysis of left ventricular filling could help in the identification of those cases which are positive for ischaemia.

Prothrombotic state and elevated levels of plasminogen activator inhibitor-1 in mitral stenosis with and without atrial fibrillation.

Patients with mitral stenosis in sinus rhythm are in a prothrombotic state and have fibrinolytic dysfunction, shown by an increase in levels of the inhibitor of tissue plasminogen activator, D-dimer, and modified antithrombin III. This state may be observed even in patients without dilated left atria (diameter < or =45 mm).

Acute cardiac rupture complicating pre-discharge exercise testing. A case report with complete echocardiographic follow-up.

The case of a 76 year-old male who suffered acute free wall rupture and sudden hemodynamic deterioration during the recovery phase of a pre-discharge exercise testing (performed 7 days after a noncomplicated myocardial infarction) is presented. Usefulness of echocardiography in early diagnosis, management (guiding pericardiocentesis) and follow-up is remarked and, on the other hand, medical treatment after a successful resuscitation is confirmed as an alternative option in these cases.

Are double potentials markers of a specific zone of the atrioventricular junction in the isolated rabbit heart?

A study is made of the characteristics of the atrial potentials recorded in the Koch triangle and its proximity, their variations on modifying the site of cardiac pacing, and their usefulness as markers of a distinct zone of the AV junction. In 12 isolated and perfused rabbit heart preparations an analysis was made of the endocardial atrial electrograms recorded with a multiple electrode positioned in the AV junction. The electrograms were obtained during spontaneous rhythm and on pacing at the crista terminalis (CT), interatrial septum (IAS), left atrium, and right ventricle. Double potentials were frequently obtained. On pacing at the CT, high-low double potentials (DP [H-L]) were more frequent (P < 0.05) in the low CT (11% +/- 4% of the electrodes) and posterior zone of the Koch triangle (6% +/- 5%), than in the IAS (1% +/- 2%) and anterior zone of the Koch triangle (2% +/- 3%). A similar tendency was observed either on pacing at the left atrium or during spontaneous rhythm. During pacing at the IAS the percentages of low-high double potentials (DP (L-H]) were significantly higher (P < 0.05) in the low CT (7% +/- 6%). DP (H-L) were of low sensitivity in indicating a given zone; maximum sensitivity was 61% in the low CT when pacing at the CT. DP (L-H) proved even less sensitive in indicating a given zone, though their specificity was greater in the low CT (91%) during pacing at the IAS. The specific zones in which the highest percentages of DP (H-L) or DP (L-H) are obtained depend on the site of cardiac pacing. On pacing at the IAS, DP (L-H) are more specific of the low CT. During pacing at both the CT and at the IAS, DP (H-L) sensitivity in indicating a given zone is low.

Modification of atrioventricular nodal electrophysiology by selective radiofrequency delivery on the anterior or posterior approaches.

An analysis was made in 14 isolated and perfused rabbit hearts of the electrophysiological effects of selective radiofrequency (RF) delivery in the anterior (group I, n = 7) or posterior zone (group II, n = 7) of the Koch triangle, with the aim of modifying atrioventricular nodal (AVN) conduction without suppressing 1:1 transmission. After opening the right atrium, RF was delivered (0.5 W) with a 1-mm diameter unipolar electrode positioned in the selected zone until a prolongation of no less than 15% was obtained in the Wenckebach cycle length (WCL). Before and after (30 min) RF, anterograde and retrograde AVN refractoriness and conduction were evaluated, stimulating from the crista terminalis (CT), the interatrial septum (IAS), and from the RV epicardium. After RF, the following percentage increments were observed in group I: AH(CT) = 36% +/- 9%, AH(IAS) = 38% +/- 11%, WCL(CT) = 28% +/- 8%, WCL(IAS) = 22% +/- 6%, functional refractory period (FRP) of the AVN(CT) = 13% +/- 11%, FRP-AVN(IAS) = 13% +/- 8%, retrograde WCL = 20% +/- 19%, and retrograde FRPVA = 13% +/- 16%. The increments observed in group II and the significances of the differences with respect to group I were: AH(CT) = 11% +/- 14% (P < 0.01), AH(IAS) = 19% +/- 32% (NS), WCL(CT) = 42% +/- 14% (P < 0.05), WCL(IAS) = 42% +/- 16% (P < 0.01), FRP-AVN(CT) = 28% +/- 28% (NS), FRP-AVN(LAS) = 21% +/- 19% (NS), retrograde WCL = 35% +/- 24% (NS), and retrograde FRP = 16% +/- 13% (NS). In both groups, the AH interval variations were not correlated with those of the rest of the parameters analyzed. Truncated nodal function curves suggestive of a dual AV nodal pathway were obtained in three experiments, though in only one of them was this observed under basal conditions. In the other two experiments, with dual AV nodal physiology only after RF (one from each group), AV nodal reentrant tachycardias were triggered with atrial extrastimulus at coupling intervals equal to or shorter than at those that cause a sudden lengthening of the AH interval, RF delivered in the anterior and posterior zones of the Koch triangle produced effects of different magnitude on the AH interval and Wenckebach cycle length. In the anterior zone the AH interval was prolonged to a greater extent, while in the posterior zone the effects were greater on the Wenckebach cycle length. No correlation existed between the variations in AH interval and Wenckebach cycle length, regardless of where RF was delivered. The evaluation of anterograde AV nodal refractoriness was similar when stimulating from the crista terminalis or from the interatrial septum. By delivering RF, it was possible to induce dual AV nodal physiology and reentrant tachycardias.

Role of infarction artery status in left ventricular remodeling after acute myocardial infarction.

The aim of this study was to evaluate the relation between the infarction artery status and left ventricular volumes, independently of regional ventricular dysfunction, at 4-6 weeks after a first myocardial infarction. The study group consisted of 100 patients, of whom 80 received thrombolytic treatment. Coronary and contrast left ventricular angiograms were performed at 36+/-5 days postinfarction. Left ventricular end-diastolic and end-systolic volumes were measured. The centerline chord motion method was used to calculate the extent of wall motion abnormality (percentage of chords with hypokinetic motion) and its severity (maximum units of S.D. below the normal wall motion reference). Minimum lumen diameter, patency and collateral flow in the infarction artery were also analyzed. Eight patients (group I) showed occlusion with poor collateral flow in the infarction artery, 22 patients (group II) occlusion with good collateral flow, 38 patients (group III) severe residual stenosis (minimum lumen diameter < or = 1 mm), and 32 patients (group IV) non-severe residual stenosis (minimum lumen diameter > 1 mm). Patients from group I presented greater wall motion abnormality in terms of both extent (P=0.005) and severity (P=0.007), and greater end-diastolic (P=0.07) and end-systolic (P=0.0008) volumes; there were no differences among groups II, III and IV. By stepwise multivariate regression analysis, the extent of wall motion abnormality was the main determinant of end-diastolic (P=0.0001) and end-systolic (P=0.0001) volumes; occlusion with poor collateral flow was also a significant independent factor for end-systolic volume (P=0.03). Total occlusion (including both with and without collaterals) and the minimum lumen diameter did not correlate with end-diastolic and end-systolic volumes. We concluded that (A) the extent of regional dysfunction is the primary determinant of left ventricular volumes at 4-6 weeks postinfarction. (B) The status of the infarction artery is a weak predictor of end-diastolic volume, which is the best descriptor of ventricular remodeling, although occlusion with poor collateral flow is associated to larger end-systolic volume.

[Apical hypertrophic myocardiopathy and multiple fistulae between the coronary vessels and the left ventricle]. / Miocardiopatía hipertrófica apical y múltiples fístulas entre coronarias y ventrículo izquierdo.

A male patient presented with symptoms of angor under effort. Echocardiography and angiocardiography revealed apical hypertrophic myocardiopathy, associated with multiple fistulas connecting the anterior descending coronary artery and right coronary artery with the cavity of the left ventricle, as demonstrated by coronariography. We comment on the hypothesis that support a causal relationship between the two anomalies, microfistulas being the possible cause of the reactive hypertrophy through the induction of a coronary steal phenomenon with local ischemia; alternatively, the myocardiopathy itself might be the cause of microfistulas formation by inducing an anomaly in the Thebesius venous system. A pathogenic relationship is suggested between the syndrome of angor and these two rare pathological entities.

[Hypertrophic myocardiopathy and ostium primum]. / Miocardiopatía hipertrófica y ostium primum.

A 45-year-old male with palpitations and a heart murmur was investigated. Echocardiography and haemodynamic study revealed the presence of a ostium primum type interatrial communication with left-right shunting and asymmetric hypertrophic heart disease. There was no subaortic obstruction, but anterior systolic movement of the mitral valve was detected that did not contact with the interventricular septum--in part due to the paradoxical motion of the latter. The possible benefit of surgery in this infrequent association is discussed, and a review is made of the literature.

Effect of site, summation and asynchronism of inputs on atrioventricular nodal conduction and refractoriness.

The impulses coming from the sinus node synchronically penetrate the AV node via the crista terminalis and inter-atrial septum. Studies in superfused rabbit AV preparations suggest that the crista terminalis is a more effective input than the inter-atrial septum, and that the summation of both inputs facilitates AV nodal conduction. The aim of this study was to verify the hypothesis in a more physiological model, such as the whole rabbit heart perfused by a Langendorff system. Fifteen rabbit hearts were studied in a Langendorff perfusion system with six bipolar extracellular electrodes: two for stimulating (crista terminalis and inter-atrial septum) and four for recording (crista terminalis, inter-atrial septum, His bundle electrogram and right ventricle). Seven hearts (Group I) were consecutively paced at the crista terminalis, inter-atrial septum and both sites simultaneously, to determine the AV nodal Wenckebach cycle length and effective refractory period under basal conditions and after acetylcholine (0.75 x 10(-6) M). In eight hearts under 0.75 x 10(-6) M acetylcholine (Group II), the crista terminalis and inter-atrial septum were simultaneously (delay = 0 ms) or sequentially (delay = 2, 4, 6, 8, 10, 12, 14, and 16 ms) stimulated to calculate the AV nodal effective refractory period and the AH interval at an atrial coupling interval 5 ms longer than the AV nodal effective refractory period, for each delay tested.(ABSTRACT TRUNCATED AT 250 WORDS)

[Transcatheter ablation with high-frequency currents as a method for creating useful experimental models in the study of cardiac conduction and automatism]. / Ablación transcatéter con corrientes de alta frecuencia como método para la creación de modelos experimentales útiles en el estudio de la conducción y el automatismo cardíacos.

PURPOSE: analyze the utility of transcatheter ablation with high-frequency currents to create different experimental models of altered cardiac automatism and conduction. METHOD: the results were obtained in six anesthetized dogs subjected to electrophysiological study after selectively applying transcatheter radiofrequency ablation to different zones of the specific cardiac conduction system. Ablation was carried out using conventional bipolar 7F catheter-electrodes. High-frequency currents (0.7 MHz) were emitted through the distal electrode, with variable intensity and duration according to the aim of the experiment. Anatomic (fluoroscopic) and electrophysiological criteria were used to position the electrode within the ablation zone. RESULTS: selective radiofrequency application to the atrioventricular junction zone affords complete A-V blocks with escape rhythms located in the A-V node or His-Purkinje system, together with different degrees of infra- and intra-hisian and intranodal blocks. The modification of intranodal refractoriness and conduction without interrupting atrial pulse transmission may manifest atypical patterns with truncated nodal conduction curves. The abolition of sinus function through ablation in the zone of the sulcus terminalis makes it possible to obtain supraventricular subsidiary rhythms. The obtaining of intranodal complete blocks with supra-Hisian escape rhythms demonstrates phenomena such as the modulation of subsidiary automatism by non-transmitted atrial pulses, analyzed by constructing phase-response curves. CONCLUSION: transcatheter ablation using high-frequency currents is useful in demonstrating phenomena related to intranodal and His-Purkinje conduction, subsidiary pacemaker automatism or the modulation of automatism and conduction via non-transmitted pulses.

[Left ventricular outflow obstruction due to accessory mitral tissue]. / Obstrucción a la eyección ventricular izquierda causada por tejido mitral accesorio.

An asymptomatic 31-year-old woman was studied because she presented a systolic ejection cardiac murmur. The echocardiogram showed a mobile, sac-like mass attached to the ventricular surface of the anterior mitral leaflet and its chordae tendineae and papillary muscle. This structure moved to the left ventricular outflow tract during every systole occupying the subaortic area. Conventional and color-coded Doppler examination revealed left ventricular outflow obstruction caused by the accessory mitral valve tissue that produced a high-velocity turbulent flow pattern in the subaortic area where the sac-like structure approximated to the outflow tract walls.