Beats In Patients Research Articles

Catheter ablation of arrhythmic storm triggered by monomorphic ectopic beats in patients with coronary artery disease

Frequent episodes of polymorphic ventricular tachycardias/ventricular fibrillation (VT/VF) in patients with coronary artery disease can be triggered by monomorphic ventricular premature beats (VPBs) and thus, amenable to catheter ablation. The goal of this study was to review single-center experience in catheter ablation of electrical storm caused by focally triggered polymorphic VT/VF. Catheter ablation of electrical storm due to focally triggered polymorphic VT/VF was performed in nine patients (mean age, 62+/-7 years; two females). All patients had previous myocardial infarction (interval of 3 days to 171 months). Mean left ventricular ejection fraction was 27+/-6 percent. All patients presented with repeated runs of polymorphic VT/VF triggered by monomorphic VPBs. Based on mapping data, the ectopic beats originated from scar border zone on interventricular septum (n=5), inferior wall (n=3), and lateral wall (n=1). Catheter ablation was performed to abolish the triggering ectopy and to modify the arrhythmogenic substrate by linear lesions within the infarct border zone. The ablation procedure was acutely successful in eight out of nine patients. During the follow-up of 13+/-7 months, two patients died due to progressive heart failure. One patient had late recurrence of electrical storm due to ectopic beats of different morphology and was successfully reablated. Electrical storm due to focally triggered polymorphic VT/VF may occur either in subacute phase of myocardial infarction or substantially later after index event. Catheter ablation of ectopic beats triggering these arrhythmias can successfully abolish electrical storm and become a life-saving procedure.

Mitral valve prolapse: a source of arrhythmias?

Cardiac arrhythmias are frequently detected in patients with mitral valve prolapse (MVP) The proper mechanisms causing ventricular arrhythmias in patients with MVP have not been fully investigated. In the current issue of the International Journal of Cardiovascular Imaging, Turker et al. [1] evaluated the clinical, echocardiographic and heart rate variability (HRV) parameters, and plasma concentrations of electrolytes and inflammatory markers in predicting ventricular arrhythmias in 58 consecutive patients with MVP. Ventricular arrhythmias were defined as the occurrence of ventricular premature contractions (VPCs), VPC couplets, and ventricular tachycardias documented by Holter analysis, continuous monitoring or by electrocardiography. Twenty patients (34%) showed ventricular arrhythmias, and 38 (66%) patients did not have ventricular arrhythmias. Seventeen patients had VPC, 2 patients had VPC couplets and one patient had ventricular tachycardia. Univariable predictors of ventricular arrhythmias included echocardiography-determined isovolumetric relaxation time and the presence of moderate to severe mitral regurgitation. Interestingly, multivariable logistic regression analysis showed that occurrence of moderate to severe mitral regurgitation was the only independent predictor of ventricular arrhythmias. Several recent studies did already address the relation between cardiac arrhythmias and the presence of MVP. Chen et al. [2] showed that improper autonomic tone is to be considered the etiology of arrhythmias in conjunction with MVP. Heart rate turbulence (HRT) and HRV are methods assessed for autonomic dysfunction. The authors studied the relationship of HRT, HRV and the number of ventricular premature beats in patients with MVP and non-significant mitral regurgitation. No significant correlation was found between the number of VPCs and HRT/HRV parameters. Markiewicz-Łoskot et al. [3] studied electrocardiographic abnormalities in ten young athletes with MVP. Abnormal ECG repolarization was found in seven athletes. Young athletes with MVP are therefore often predisposed to electrocardiographic abnormalities of ventricular repolarization. Cetinkaya et al. [4] evaluated the risk of vasovagal syncope and cardiac arrhythmias in 37 children with MVP. Arrhythmias and the risk of vasovagal syncope, indicated by a positive tilt test, were found to be increased in children with MVP. Similar to echocardiography [5–13], cardiovascular magnetic resonance (CMR) imaging can identify MVP by similar anatomic and functional criteria [13–30]. In addition, CMR allows tissue characterization in various cardiac diseases using hyperenhancement techniques [31–38]. In this way, CMR can identify myocardial fibrosis involving the papillary muscle in MVP patients. Delayed contrast enhancement (DCE) of papillary muscles is often present in a subgroup of patients with complex ventricular arrhythmias [39]. This tissue hyperenhancement is indicative of fibrosis which may act as a focus for arrhythmias. Kwon et al. [40, 41] using delayed contrast enhancement CMR, showed a clear association of myocardial fibrosis, electrocardiography and ventricular tachyarrhythmia in hypertrophic cardiomyopathy (HCM). HCM subjects with ventricular tachycardias showed a higher percentage of myocardial scarring on DCE-CMR. As a consequence, the presence of fibrotic papillary muscles in patients with MVP might give rise to both cardiac arrhythmias and mitral regurgitation. In addition to echocardiography and CMR, multislice computed tomography (MSCT) has recently been shown to evaluate the functional status of the mitral valve in patients with MVP [42–45]. MSCT may therefore have a major role in preoperative assessment of the mitral valve apparatus before mitral valve surgery. To summarize, nowadays the diagnosis of MVP can be made by several imaging techniques. Apart from echocardiography, CMR and MSCT are capable of accurately delineating the structure and function of the mitral valve. Next, there is a clear association between the level of incompetence of the mitral valve and the presence of cardiac arrhythmias, in particular in case of MVP. These findings have been proven both by echocardiography and DCE-CMR. The study by Turker et al. [1], using echocardiography, add to these results by showing that the occurrence of moderate to severe mitral regurgitation was the only independent predictor of ventricular arrhythmias in patients with MVP.

Autonomic Function during Closed Loop Stimulation and Fixed Rate Pacing: Heart Rate Variability Analysis from 24-Hour Holter Recordings

Aim of this retrospective study was to analyze the effect of closed-loop stimulation (CLS) and DDD pacing mode on autonomic balance, and to evaluate heart rate variability (HRV) during CLS stimulation. Autonomic balance was estimated by a 24-hour HRV analysis of paced and spontaneous beats in patients implanted with a dual-chamber pacemaker (Inos(2+) CLS-Biotronik GmbH, Berlin, Germany) and randomly assigned to CLS or DDD pacing mode. Patients underwent two 24-hour electrocardiogram Holter recordings at the end of each 3-month pacing mode period. Each Holter recording was automatically scanned to extract sequences of consecutive beats of the same type [atrial paced (Ap)-sequence and atrial spontaneous (As)-sequence], lasting at least 130 beats. Eight hundred and ten sequences were extracted from 15 patients, and the following spectral parameters were evaluated during both CLS and DDD mode: the total power (variance), the absolute and percentage (relative to the total power) powers of the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) components, as well as the LF/HF power ratio. The two main findings of this study were: in all the patients, CLS seems to mimic short-term physiological HRV, although the variability (total power) was lower than that relative to the spontaneous beats; the HRV of the spontaneous beats had an higher LF/HF when the pacemaker was programmed as DDD respect to CLS, consistent with a shift toward sympathetic predominance.

Single-beat estimation of the left ventricular end-diastolic pressure–volume relationship in patients with heart failure

AimsTo test a method to predict the end-diastolic pressure–volume relationship (EDPVR) from a single beat in patients with heart failure.Methods and resultsPatients (New York Heart Association class III–IV) scheduled for...

Questioning Conventional Wisdom

In science, what seems obvious may not be true, and what is accepted as conventional wisdom, may sometimes be based on flawed assumptions. What is more obvious than the fact that the sun revolves around the earth? Each day the sun rises in the eastern horizon, and we observe it moving across the sky until it retires in the west. And yet, it is not true that the earth is the center of the universe. Galileo de’ Galilei, the scientist born in Pisa, was persecuted for questioning such conventional wisdom and supporting the theory proposed by Nicolaus Copernicus of a heliocentric universe. Ultimately, the truth could not be suppressed. We have many examples of progress that resulted from the questioning of strongly held beliefs that once seemed so obvious. Who anticipated that a gastric ulcer could be considered an infectious disease?1 Who expected that drugs that effectively suppressed premature ventricular beats in patients with ischemic heart disease would cause harm?2 Who believed that treatment strategies associated with substantial risk reduction might be poorly adopted into practice even 10 years after the publication of the trials establishing their efficacy?3 Who could …

Circadian variation of heart rate turbulence and the number of ventricular premature beats in patients with mitral valve prolapse

Circadian variation of heart rate turbulence and the number of ventricular premature beats in patients with mitral valve prolapse

Relationship of heart rate turbulence, heart rate variability and the number of ventricular premature beats in patients with mitral valve prolapse and non-significant regurgitation

Cardiac arrhythmia is frequently detected in patients with mitral valve prolapse (MVP) and improper autonomic tone is considered the etiology. Heart rate turbulence (HRT) and heart rate variability (HRV) are methods assessed for autonomic dysfunction. To evaluate whether the number of ventricular premature contractions (VPCs) is influenced by HRT or HRV in patients with MVP. Holter monitoring for the number of VPCs and correlation analysis with HRT and HRV was performed. There were 31% and 3% with abnormal turbulence onset (TO) and turbulence slope (TS) values in totally 68 patients. No significant correlation is found between the number of VPCs and HRT, HRV parameters. In analysis the relationship between HRT and HRV parameters, TS has higher correlation with HRV than TO values, particular in time-domain.

Efficacy of Consistent Atrial Pacing Algorithm for Suppression of Atrial Arrhythmias in Patients With Sick Sinus Syndrome and Atrial Fibrillation

Atrial overdrive provides the best opportunity to suppress atrial arrhythmias. Atrial preference pacing (APP) algorithm has been designed to achieve a high percentage of atrial pacing. The aim of this study was to assess the efficacy of APP algorithm in patients with implanted pacemakers and tachycardia-bradycardia syndrome. The subjects were 17 patients (mean age, 71.7+/-9.0 years old, 4 males) implanted with a DDDR pacemaker Thera DR (Medtronic, Minneapolis, MN, USA). All patients had sick sinus syndrome and paroxysmal atrial fibrillation before pacemaker implantation. Informed consent was obtained from each participant before enrollment. DDDR and mode switch or APP were randomly programmed. After two weeks, the pacing mode was switched to another mode. The percentage of atrial pacing was significantly higher in APP than in DDDR (97.7+/-1.4 versus 52.3+/-30.8, P<0.0001). Atrial premature beat counts were significantly greater in DDDR than in APP (30689+/-42534 versus 7717+/-10700, P<0.005). There was no significant difference in mode switch episode counts between DDIR and APP (2.6+/-5.5 versus 8.4+/-19.2, NS). Although there was no significant difference in mode switch episode counts between DDDR and APP, APP algorithm can successfully prevent atrial premature beats in patients with tachycardia-bradycardia syndrome.

Fusion beat in patients with heart failure treated with left ventricular pacing: may ECG morphology relate to mechanical synchrony? A pilot study.

BackgroundElectrical fusion between left ventricular pacing and spontaneous right ventricular activation is considered the key to resynchronisation in sinus rhythm patients treated with single-site left ventricular pacing.AimUse of QRS morphology to optimize device programming in patients with heart failure (HF), sinus rhythm (SR), left bundle branch block (LBBB), treated with single-site left ventricular pacing.Methods and ResultsWe defined the "fusion band" (FB) as the range of AV intervals within which surface ECG showed an intermediate morphology between the native LBBB and the fully paced right bundle branch block patterns.Twenty-four patients were enrolled. Echo-derived parameters were collected in the FB and compared with the basal LBBB condition. Velocity time integral and ejection time did not improve significantly. Diastolic filling time, ejection fraction and myocardial performance index showed a statistically significant improvement in the FB. Interventricular delay and mitral regurgitation progressively and significantly decreased as AV delay shortened in the FB. The tissue Doppler asynchrony index (Ts-SD-12-ejection) showed a non significant decreasing trend in the FB. The indications provided by the tested parameters were mostly concordant in that part of the FB corresponding to the shortest AV intervals.ConclusionUsing ECG criteria based on the FB may constitute an attractive option for a safe, simple and rapid optimization of resynchronization therapy in patients with HF, SR and LBBB.

Modeling the Blood Pressure Response to a Ventricular Premature Complex with Special Reference to Heart Rate Turbulence

Ventricular premature beats have been used to characterize a risk factor for patients after myocardial infarction. This risk stratification has recently been improved by estimating the so-called heart rate turbulence, i.e., the acceleration and subsequent deceleration of the sinus beats following a ventricular premature beat. This response is triggered by oscillations in aortic blood pressure following a ventricular premature beat. In the following we report on a model to fit blood pressure oscillations due to ventricular premature beats in patients following myocardial infarction. The data on which this analysis is based were derived from 39 patients with varying degrees of left ventricular dysfunction following myocardial infarction. The recording included high-quality ECG and a noninvasive beat-to-beat recording of blood pressure from a finger artery. Records were chosen such that 5 to 30 ventricular premature beats occurred within a 30-min recording period. In a first step, we fed our data, i.e., a given series of coupling intervals, into two established cardiac models (Ten-Voorde and Mrovka et al.) and observed the blood pressure behavior. It turned out that both models were not able to reflect the full range of the observed blood pressure oscillations. For this reason we expanded the model of Mrovka et al. (Am J Physiol Regul Integr Comp Physiol 279: R1171–R1175, 2000), such that the desired pattern approximately appeared. This was achieved by introducing a more subtle left ventricular function curve and keeping track of the endsystolic volume in the left ventricle. After parameter fitting, a detailed picture of the hemodynamics appeared for each patient. It was found that left ventricular function and, in particular, post-extrasystolic potentiation was crucial for the prediction of the blood pressure response following a ventricular premature beat. Thus, in patients following myocardial infarction, not only impaired baroreceptor function but also altered left ventricular contraction behavior contributes to the phenomenon of heart rate turbulence.

Short-term fluctuations in sinus cycle length after premature ventricular beats in patients with hypertrophic cardiomyopathy and myocardial infarction

Background: Sinus cycle length has been reported to fluctuate after a ventricular premature beat (VPB). The purpose of this study was to assess the short-term fluctuations of sinus cycle length in patients with hypertrophic cardiomyopathy (HCM) and prior myocardial infarction (MI). Methods: The relative deviation of RR intervals from the mean of the last two RR intervals preceding a VPB were calculated during the 20 subsequent beats following the VPB from Holter recordings in 92 patients with non-obstructive HCM, 57 patients with prior MI and 54 healthy controls. Results: In controls, the deviations of the RR intervals were negative for several beats after a VPB and subsequently changed to positive before returning to the baseline. Similar changes in RR intervals following a VPB were exhibited in HCM patients; however, the late positive deviations of RR intervals were more marked than in controls. By contrast, in patients with prior MI, the early negative deviations of RR intervals were smaller compared with controls, and the deviations returned to the baseline without incidence of the positive changes. Conclusions: Short-term fluctuations in sinus cycle length after a VPB differed exclusively among HCM patients, prior MI patients, and healthy controls.

Prognostic significance of heart rate turbulence following ventricular premature beats in patients with idiopathic dilated cardiomyopathy.

Heart Rate Turbulence in Dilated Cardiomyopathy. The aim of this study was to investigate the prognostic significance of heart rate turbulence (HRT) characterized by HRT onset and slope after ventricular premature beats in patients with idiopathic dilated cardiomyopathy (IDC). Blinded HRT analysis was performed in 242 patients with IDC who were enrolled in the Marburg Cardiomyopathy database between 1992 and 2000. During 41 +/- 23 months of follow-up, 54 patients (22%) died or underwent heart transplant. On Cox univariate regression analysis, abnormal HRT onset, HRT slope, HRT onset combined with HRT slope, left ventricular (LV) ejection fraction, LV size, and New York Heart Association (NYHA) functional class III showed a significant association with total mortality or the need for heart transplant. On multivariate analysis, abnormal HRT onset identified patients without transplant-free survival, as did LV size and NYHA class III heart failure. Major arrhythmic events were observed in 42 patients (17%) during follow-up. On univariate analysis, abnormal HRT onset, HRT onset combined with HRT slope, male sex, NYHA class III, LV ejection fraction, and LV size were associated with a higher incidence of major arrhythmic events. On multivariate analysis, only LV ejection fraction remained as a significant arrhythmia risk predictor, with a relative risk of 2.2 per 10% decrease in ejection fraction (95% confidence interval 1.5-3.2). In this selected patient population with IDC, HRT onset is a significant predictor of transplant-free survival, as are LV size and NYHA class. For arrhythmia risk stratification, however, only LV ejection fraction remained a significant risk predictor on multivariate analysis.

Autonomic tone in patients with supraventricular arrhythmia associated with mitral valve prolapse in young men.

This study examined the relation between autonomic tone and the frequency and duration of supraventricular arrhythmias (SVA) in 44 men (mean age 17 +/- 5 years) with mitral valve prolapse (MVP), confirmed by echocardiography. Ambulatory and short-term electrocardiograms (ECG) were recorded, and transesophageal pacing was performed. Frequency domain heart rate variability (HRV) indices were obtained from short-term ECG recordings at rest and during postural stress. In 14 patients, the index of parasympathetic activity was significantly higher (2.1 +/- 0.01 vs -1.5 +/- 0.01, P < 0.01), and associated with a high incidence of vagally-mediated SVA. The frequency of SV premature beats in patients with parasympathetic prevalence was 58 +/- 86/hour versus 10 +/- 27/hour in patients with sympathetic prevalence (P < 0.05). In 30 patients with high sympathetic activity, the index of sympathetic tone was significantly higher (3.1 +/- 0.01 vs 0.5 +/- 0.01) and the high frequency/low frequency ratio significantly lower (0.294 +/- 0.03 vs 0.581 +/- 0.02, P < 0.05), though the incidence of SVA was significantly lower and duration shorter. The algorithm allowed the noninvasive quantitative assessment of autonomic activity and mechanism behind the development of SVA, which may help in the choice of treatment.

Atrial premature beats in patients with focal atrial fibrillation: incidence at baseline and impact of provocative maneuvers.

This study evaluated the incidence of atrial premature beats (APBs) and the impact of various provocative maneuvers in patients with focally initiated AF. Fifty patients (39 men, 57 +/- 0.4 years) with focally initiated, paroxysmal AF underwent Holter recording and a standardized protocol of provocative maneuvers: vagomechanical stimulation, adenosine 12 mg i.v., esmolol 500 ng/kg i.v., orciprenaline i.v. 5 mg/50 mL saline 0.9%, and atropine 0.01 mg/kg i.v. A surface ECG was recorded for 20 minutes at baseline and following each part of the protocol. High focal activity was defined as > or = 1 APB/minute. During Holter ECG, 29 (58%) patients had an amount of < 200 APBs, 12 (24%) patients < 700 > or = 200, and 9 (18%) patients > or = 700 APBs. Less than 1 hour of high focal activity was observed in 34 (68%) of the 50 patients. Before starting provocative maneuvers 15 (30%) patients had high focal activity whereas 35 (70%) presented < 1 APB/minute. In 29 (58%) patients APBs increased by > or = 1/min during provocative maneuvers: by vagomechanical stimulation in 11 patients, after adenosine in 15, esmolol in 12, orciprenaline in 15, and after atropine in 9 patients. In all patients with > or = 1 APB/min at baseline, focal activity decreased or disappeared during some single provocative maneuvers. AF occurred in eight patients under provocative maneuvers. No predictive factors of a successful provocative maneuver were detected with regard to the baseline patients characteristics and Holter results. In conclusion, patients with focally initiated AF have a low incidence of spontaneous APBs. Various provocative maneuvers successfully increase APBs in more than half of the patients; orciprenaline had the highest efficacy. Some provocative maneuvers may suppress APBs in the setting of high focal activity at baseline.

Heart rate changes preceding ventricular ectopy in patients with ventricular tachycardia caused by reentry, triggered activity, and automaticity

Objectives Although enhanced sympathetic tone is thought to be proarrhythmic and β-blockade reduces the risk of sudden cardiac death in survivors of myocardial infarction, the role of the autonomic nervous system in triggering spontaneous ventricular ectopy and ventricular tachycardia (VT) has not been fully elucidated. The purpose of this study was to compare and contrast autonomic tone preceding spontaneous ventricular arrhythmias in patients with reentrant, triggered, and automatic forms of VT. Background The prevailing model of reentrant VT is based on a triggering beat interacting with a fixed substrate. Within this model, cyclic fluctuations in autonomic tone comprise a “third factor” that may initiate the triggering extrasystoles as well as alter the substrate, facilitating perpetuation of tachycardia. Consistent with this model, adrenergic stimulation can facilitate the induction of reentrant arrhythmias as well as arrhythmias resulting from enhanced automaticity and those caused by triggered activity resulting from cyclic adenosine monophosphate–dependent delayed afterdepolarizations. Methods and Results On the basis of the results at electrophysiologic study, 26 patients with coronary artery disease were identified as having reentrant VT, 11 were identified as having idiopathic VT caused by triggered activity, and 4 were identified as having idiopathic VT caused by enhanced automaticity. Each patient underwent 24-hour electrocardiographic monitoring, and the mean sinus R-R intervals immediately preceding each sinus beat as well as the 15 beats preceding sinus beats, premature ventricular contractions (VPCs), and complex ventricular ectopy (couplet/nonsustained VT) were computed. In addition, high-frequency heart rate variability was determined. Heart rate accelerated before spontaneous ventricular ectopy for all three arrhythmia mechanisms. R-R intervals preceding episodes of complex ventricular ectopy were significantly shorter than the corresponding intervals preceding single VPCs in patients with triggered VT [ p = 0.006 and 0.01, R-R(-1) and R-R(-15), respectively] and in those with reentrant VT ( p = 0.007 and p = 0.05). There were no corresponding differences in high-frequency heart rate variability. R-R intervals preceding single VPCs were significantly shorter than the corresponding intervals preceding sinus beats in patients with automatic VT ( p = 0.0004 and 0.0001, respectively), which was accompanied by a small reduction in high-frequency heart rate variability ( p = 0.04). Conclusions Heart rate accelerates before spontaneous ventricular ectopy in patients with VT. The acceleration is disproportionate to parasympathetic withdrawal, implicating increased endogenous sympathetic tone in the genesis of spontaneous ventricular arrhythmias caused by all three electrophysiologic mechanisms: reentry, triggered activity, and automaticity. (Am Heart J 1998;136:425-34.)

Immediate Reinitiation of Atrial Fibrillation Following Internal Atrial Defibrillation

Although the recurrence rate of atrial fibrillation has been reported to be similar to that after external and internal cardioversion, little is known about immediate reinitiation of atrial fibrillation (IRAF) following internal cardioversion. Thirty-eight patients (24 men; mean age 63 +/- 13 years) underwent internal atrial defibrillation. Catheter-based defibrillation electrodes were positioned in the anterolateral right atrium and the coronary sinus. All patients were cardioverted at a mean threshold of 4.6 +/- 3.4 J. Five of 38 patients (13%) had 1 to 4 episodes of IRAF. No difference in clinical and echocardiographic characteristics were observed when patients with and without IRAF were compared. Atrial fibrillation was always reinitiated by an atrial premature beat. When the earliest atrial endocardial activation time on the defibrillation catheters was analyzed, these atrial premature beats did not seem to originate from the defibrillation catheters. Twenty-one patients had atrial premature beats without IRAF. When the coupling intervals of the first atrial premature beat in patients without and with IRAF after conversion were compared, a significant difference was found (661 +/- 229 vs 418 +/- 79 msec, P < 0.05). IRAF was successfully treated with repeated shock delivery after the administration of atropine in 1 patient and intravenous flecainide in 2. Only repeated shock delivery was sufficient to treat IRAF in another 2 patients. Late recurrences of atrial fibrillation occurred in 3 of 5 with IRAF and in 19 of 33 patients without IRAF (P = NS). IRAF after internal atrial defibrillation occurred in 13% of patients, was always initiated by an atrial premature beat having a short coupling interval not originating from the defibrillation catheters, and was prevented by repeated shock delivery with or without preceding administration of pharmacologic agents. IRAF did not predict early recurrences of the arrhythmia after discharge from the hospital, emphasizing the necessity to treat immediate reinitiation promptly to achieve a successful cardioversion.

The characteristics of left coronary blood flow velocity waveforms during normal sinus rhythm and at postextrasystolic beat in patients with non-obstructive hypertrophic cardiomyopathy

The characteristics of left coronary blood flow velocity waveforms during normal sinus rhythm and at postextrasystolic beat in patients with non-obstructive hypertrophic cardiomyopathy

Periodicity of global ventricular activation of sinus beats in patients with coronary artery disease and sustained ventricular tachycardia

Despite increasing clinical reliance on signal-averaged electrocardiograms for determining risk for development of sustained ventricular tachycardia (VT), the periodicity of global ventricular activation during sinus rhythm has not been defined. Accordingly, epicardial and transmural ventricular electrograms during 6 consecutive sinus beats were evaluated in 10 patients with abnormal signal-averaged electrocardiograms who were undergoing surgery for VT. Bipolar electrograms were recorded with sock and needle electrodes from up to 96 epicardial and 156 transmural sites. Electrogram morphology, duration and activation were compared on a beat-to-beat basis. In all, 9,816 electrograms were analyzed. Mean durations of epicardial and transmural electrograms were 33 ± 16 ms (range 6 to 199) and 23 ± 10 ms (range 6 to 72), respectively, with a beat-to-beat variation of 1.9 ± 1.4 ms per site. Similarly, local activation times did not vary significantly during the 6 cardiac cycles analyzed (mean variation 1.7 ± 2.0 ms). Local conduction failure was not observed. Although electrograms during the terminal 40 ms of the QRS were significantly longer (36 ± 20 vs 26 ± 12 ms, p < 0.001) when compared with those recorded earlier during the QRS complex, beat-to-beat variation in duration (2.1 ± 1.6 ms) and activation (1.7 ± 2.3 ms) was not significant. Results demonstrate that epicardial and transmural electrograms recorded during sinus rhythm in patients with sustained VT are periodic signals and thus establish a physiologic basis for signal averaging of electrocardiographic waveforms in these patients.

Relationship between redistribution on exercise thallium-201 scintigraphy and repetitive ventricular premature beats in patients with recent myocardial infarction

The relationship between myocardial ischemia detected by exercise thallium-201 scintigraphy and repetitive ventricular premature beats (VPBs) during ambulatory monitoring was evaluated in 57 patients with recent myocardial infarction. Multivariate analysis was performed to obtain the relatively important factor related to repetitive VPBs with the use of the following variables: age, redistribution, left ventricular ejection fraction, serum potassium and magnesium concentration, QRS score, left ventricular aneurysm, and the number of diseased vessels. Thirty-five patients had redistribution, but only three of them had repetitive VPBs during exercise testing. The average heart rate before 79% of 398 episodes of repetitive VPBs during ambulatory monitoring was in the range of 56 to 70/min. These data indicate that most of repetitive VPBs during ambulatory monitoring were not provoked by exercise-induced acute myocardial ischemia. However, redistribution was found to be an important factor associated with repetitive VPBs. The electrical abnormality relating to a substrate characterized by chronic reversible ischemia may explain the association between redistribution and repetitive VPBs.

Signal averaging of pre- and post-extrasystolic beats in patients with ventricular arrhythmias

To evaluate the effects of premature ventricular beats on the impulse conduction of adjacent sinus cycles, we compared the high amplification signal-averaged electrocardiogram parameters of the pre- and post-extrasystolic beats with those of the remaining sinus cycle. According to the duration of filtered QRS (fQRS), to the voltage of root mean square of the terminal 40 ms (RMS 40) and to the duration of low amplitude terminal components of the sinus cycles, ventricular late potentials were detected in nine out of 29 subjects. Patients with an abnormal signal-averaged electrocardiogram exhibited a longer fQRS (146 +/- 6 versus 116 +/- 2 ms), a reduced RMS40 voltage (18 +/- 2 versus 80 +/- 10 microV) and a prolonged duration of less than 40 microV components (42 +/- 4 versus 17 +/- 2 ms). Analysis of the pre-extrasystolic beats did not reveal any significant variation in the above parameters, showing a mean difference of 0.44 +/- 2.4 ms; 0.02 +/- 1.14 microV; 1 +/- 1.9 ms and of -1.45 +/- 1.02 ms; 3.5 +/- 8.6 microV; -0.7 +/- 0.84 ms respectively, for patients with and without ventricular late potentials. In addition, no significant variation was observed when the post-extrasystolic beats were considered. These results indicate that the sinus cycles adjacent to premature ventricular discharges do not present variations of signal-averaged electrocardiogram parameters that may suggest an influence of the ectopic beats on their intramyocardial impulse propagation.