Comparison of vectorcardiographic and 12-lead electrocardiographic detections of abnormalities in repolarization properties due to preexcitation in patients with Wolff-Parkinson-White syndrome: proposal of a novel concept of a "remodeling gradient".
(25/507)
Repolarization abnormalities after radiofrequency ablation in patients with manifest Wolff-Parkinson-White syndrome (WPW) have been attributed to cardiac memory of pre-existing changes in repolarization properties. We compared spatial ventricular gradient (VG) from vectorcardiograms with QRST values of 12-lead ECG in 41 patients with WPW (group A, manifest WPW due to left-sided accessory pathway (n = 20); group B, manifest WPW due to right-sided accessory pathway (n = 12); group C, concealed WPW (n = 9)) before and after ablation. Group N (n = 607) served as control. In groups A and B, the abnormalities of spatial VG and QRST values of 12-lead ECG that existed before and 1 day after ablation significantly decreased 1 week after ablation. In group C, spatial VG and QRST values of 12-lead ECG showed no significant changes. The diagnostic ability of spatial VG is almost equivalent to that of the QRST value of ECG in detecting repolarization abnormalities in patients with WPW before and after ablation. We propose a new concept of a "remodeling gradient" directing from the preexcited area to the opposite side of the ventricle as a result of preexcitation-induced electrical remodeling. (+info)
Ratiometry of transmembrane voltage-sensitive fluorescent dye emission in hearts.
(26/507)
Transmembrane voltage-sensitive fluorescence measurements are limited by baseline drift that can obscure changes in resting membrane potential and by motion artifacts that can obscure repolarization. Voltage-dependent shift of emission wavelengths may allow reduction of drift and motion artifacts by emission ratiometry. We have tested this for action potentials and potassium-induced changes in resting membrane potential in rabbit hearts stained with di-4-ANEPPS [Pyridinium, 4-(2-(6-(dibutylamino)-2-naphthalenyl) ethenyl)-1-(3-sulfopropyl)-, hydroxide, inner salt] using laser excitation (488 nm) and a two-photomultiplier tube system or spectrofluorometer (resolution of 500-1,000 Hz and <1 mm). Green and red emissions produced upright and inverted action potentials, respectively. Ratios of green emission to red emission followed action potential contours and exhibited larger fractional changes than either emission alone (P < 0.001). The largest changes and signal-to-noise ratio (signal/noise) were obtained with numerator wavelengths of 525-550 nm and denominator wavelengths of 650-700 nm. Ratiometry lessened drift 56-66% (P < 0.015) and indicated decreases in resting membrane potential. Ratiometry lessened motion artifacts and increased magnitudes of deflections representing phase-zero depolarizations relative to total deflections by 123-188% in intact hearts (P < 0.02). Durations of action potentials at different pacing rates, temperatures, and potassium concentrations were independent of whether they were measured ratiometrically or with microelectrodes (P > or = 0.65). The ratiometric calibration slope was 0.017/100 mV and decreased with time. Thus emission ratiometry lessens the effects of motion and drift and indicates resting membrane potential changes and repolarization. (+info)
ST depression only on the initial 12-lead ECG: early diagnosis of acute myocardial infarction.
(27/507)
AIMS: To compare the diagnostic ability of the 12-lead ECG with body surface mapping for early detection of acute myocardial infarction in patients presenting with ST depression only on the 12-lead ECG. METHODS AND RESULTS: Fifty-four consecutive patients with chest pain <24 h and ST depression were recruited. A 12-lead ECG and 80-lead body surface map were recorded at presentation from which univariate and multivariate prediction models of acute myocardial infarction were developed. Patients were randomly divided into a training-set and a validation-set. Acute myocardial infarction occurred in 16/30 training-set and 8/24 validation-set patients. Univariate prediction of acute myocardial infarction by the 12-lead ECG, based on the depth or numbers of leads with ST depression, was not improved by assessment of ST elevation outside the conventional 12 leads using body surface mapping. The optimum multivariate 12-lead ECG model developed in training-set patients (six ST depression variables) had poor sensitivity (38%) although good specificity (81%) for acute myocardial infarction when tested prospectively in validation-set patients. In contrast, the optimum body surface mapping model developed in training-set patients (three isointegral or isopotential variables) achieved high sensitivity (88%) whilst maintaining good specificity (75%) for acute myocardial infarction when tested prospectively in validation-set patients. CONCLUSION: Body surface mapping, when compared with the 12-lead ECG, may improve the early diagnosis of acute myocardial infarction in patients presenting with chest pain and ST depression only on the 12-lead ECG. (+info)
Dynamic relationship of cycle length to reentrant circuit geometry and to the slow conduction zone during ventricular tachycardia.
(28/507)
BACKGROUND: Knowledge of cycle-to-cycle changes in isthmus geometry is of potential importance for radiofrequency catheter ablation to stop reentrant ventricular tachycardia. It was hypothesized that isthmus geometry often undergoes continuous evolution throughout reentry and that cycle-length variability measurements could be used to segment reentry into distinct phases and to predict changes in isthmus geometry. METHODS AND RESULTS: A canine infarct model of reentrant ventricular tachycardia in the epicardial border zone with a figure 8 pattern of conduction was used for analysis (25 monomorphic reentry episodes, 20 experiments). Tachycardias were segmented, on the basis of cycle-length variations, into 2 to 3 distinct phases corresponding to onset, maintenance, and spontaneous termination, when it occurred (6/25 episodes). Trends of linear cycle-length change occurred throughout the maintenance phase in all tachycardias. For each trend, quantitative geometric parameters of the isthmus were measured, and the following linear relationships were established. During a trend, the slow conduction zone activation interval and tachycardia cycle length increased, while isthmus length decreased. When isthmus length decreased, isthmus width decreased at its narrowed portion. Larger decreases in isthmus length corresponded to higher rates of linear cycle-length prolongation. Also, greater cycle-length variability tended to prolong tachycardia. CONCLUSIONS: Cycle-length alterations occur throughout reentry in this canine model and are predictive of isthmus geometry changes. Because similar reentry dynamics, which affect catheter ablation efficacy, have been observed clinically, estimation of changes in geometry during electrophysiological study may help target ablation sites. (+info)
Role of functional block extension in lesion-related atrial flutter.
(29/507)
BACKGROUND: A line of block in the right atrium (RA) between the venae cavae is necessary to obtain classic atrial flutter (AFL). We tested the hypothesis that the location of that line of block would determine whether the AFL reentrant circuit would be due to single-loop reentry or figure-of-8 reentry. METHODS AND RESULTS: Simultaneous mapping from 392 sites (both atria and the atrial septum) was performed in 13 normal dogs before and after creating a linear lesion on the RA free wall. The lesion was 1 to 1.5 cm anterior and parallel to the crista terminalis (7 dogs) or posterior and close to the crista terminalis region (6 dogs). Sustained AFL (>2 minutes) was then induced. In 4 dogs with an anterior lesion, the AFL reentrant circuit traveled around the lesion (lesion reentry). In 9 dogs (3 with anterior lesions and 6 with posterior lesions), the AFL reentrant circuit included the anterior RA free wall, the atrial septum, and Bachmann's bundle (single-loop reentry). In these 9 dogs, the fixed line of block was extended to the superior and/or inferior vena cava by a functional line of block, thereby preventing lesion reentry. No figure-of-8 reentry was induced. CONCLUSIONS: In this model, the location of a fixed line of block and its functional extension determine the type of AFL reentry. These data provide an explanation for the chronic AFL that occurs in some patients after surgical repair of congenital heart lesions. (+info)
Different patterns of atrial activation in idiopathic atrial fibrillation: simultaneous multisite atrial mapping in patients with paroxysmal and chronic atrial fibrillation.
(30/507)
OBJECTIVES: We aimed to evaluate: 1) the behavior of electrical activity simultaneously in different atrial regions during atrial fibrillation (AF); 2) the difference of atrial activation between paroxysmal and chronic AF; 3) the atrial refractoriness dispersion; and 4) the correlation between the effective refractory periods (ERPs) and the FF intervals. BACKGROUND: Little data exist on the electrophysiologic characteristics of the different atrial regions in patients with AF. A more detailed knowledge of the electrical activity during AF may provide further insights to improve treatment of AF. METHODS: Right and left atria were extensively mapped in 30 patients with idiopathic AF (18 paroxysmal and 12 chronic). In different atrial locations, we analyzed 1) the FF interval duration; and 2) the grade of organization and, in case of organized electrical activity, the direction of atrial activation. Furthermore, in patients with paroxysmal AF, we determined the atrial ERP, evaluated the ERP dispersion and assessed the presence of a correlation between the ERPs and the FF intervals. RESULTS: In patients with chronic AF, we observed a shortening of the FF intervals and a greater prevalence of disorganized activity in all the atrial sites examined. In patients with paroxysmal AF, a significant dispersion of refractoriness was observed. The right lateral wall showed longer FF intervals and more organized atrial activity and, unexpectedly, the shortest mean ERPs. In contrast, the septal area showed shorter FF intervals, greater disorganization and the longest mean ERPs. CONCLUSIONS: Electrical activity during AF showed a significant spatial inhomogeneity, which was more evident in patients with paroxysmal AF. The mean FF intervals did not correlate with the mean ERPs. (+info)
Influence of atrial flutter ablation on right to left inter-atrial conduction.
(31/507)
AIMS: Ablation of the atrial isthmus between the tricuspid annulus and the inferior vena cava changes P-wave morphology during low lateral right atrial pacing. For better understanding of the mechanism of this alteration, the sequence of activation of the inter-atrial septum and the left atrium were compared before and after ablation of the isthmus between the inferior vena cava and the tricuspid annulus. METHODS AND RESULTS: In 13 patients, left atrial mapping was performed using a duodecapolar electrode catheter advanced to the far distal coronary sinus. The inter-atrial septum was mapped using a right atrial duodecapolar electrode catheter. Conduction times were measured during low lateral right atrial pacing from the pacing artefact and during sinus rhythm from the earliest right atrial electrogram to every intra-cardiac electrogram before and after the ablation. During low lateral right atrial pacing, isthmus ablation resulted in a significant delay in every left atrial lead. Changes were maximal at the posterior aspect of the left atrium and minimal at its anterior aspect. No significant change was discernible on the inter-atrial septum. During sinus rhythm, atrial activations remained unchanged. CONCLUSION: Electrocardiographic changes of P-wave morphology result from alteration in the sequence of left atrial activation rather than that of the inter-atrial septum. (+info)
Electromechanical mapping for detection of myocardial viability in patients with ischemic cardiomyopathy.
(32/507)
BACKGROUND: We evaluated the ability of electromechanical mapping of the left ventricle to distinguish between nonviable and viable myocardium in patients with ischemic cardiomyopathy. METHODS AND RESULTS: Unipolar voltage amplitudes and local endocardial shortening were measured in 31 patients (mean+/-SD age, 62+/-8 years) with ischemic cardiomyopathy (ejection fraction, 30+/-9%). Dysfunctional regions, identified by 3D echocardiography, were characterized as nonviable when PET revealed matched reduction of perfusion and metabolism and as viable when perfusion was reduced or normal and metabolism was preserved. Mean unipolar voltage amplitudes and local shortening differed among normal, nonviable, and viable dysfunctional segments. Coefficient of variation for local shortening exceeded differences between groups and did not allow distinction between normal and dysfunctional myocardium. Optimum nominal discriminatory unipolar voltage amplitude between nonviable and viable dysfunctional myocardium was 6.5 mV, but we observed a great overlap between groups. Individual cutoff levels calculated as a percentage of electrical activity in normal segments were more accurate in the detection of viable dysfunctional myocardium than a general nominal cutoff level. The optimum normalized discriminatory value was 68%. Sensitivity and specificity were 78% for the normalized discriminatory value compared with 69% for the nominal value (P:<0.02). CONCLUSIONS: Endocardial ECG amplitudes in patients with ischemic cardiomyopathy display a wide scatter, complicating the establishment of exact nominal values that allow distinction between viable and nonviable areas. Individual normalization of unipolar voltage amplitudes improves diagnostic accuracy. Electroanatomic mapping may enable identification of myocardial viability. (+info)