Impacto de la prostatectomía radical en los resultados urodinámicos de pacientes con cáncer de próstata tratados con radioterapia de intensidad modulada / Impact of a radical prostatectomy on the urodynamic results of prostate cancer patients treated with intensity modulated radiation therapy

Introducción y objetivos Evaluar el efecto de la prostatectomía radical y la edad en los resultados urodinámicos antes y después de la radioterapia de intensidad modulada administrada a pacientes con cáncer de próstata. Materiales y métodos La muestra incluyó a 40 pacientes con cáncer de próstata, 22 de los cuales habían sido sometidos a prostatectomía radical. Se midieron y compararon los parámetros urodinámicos antes y después de una media de 4,2 meses de radioterapia. La radioterapia externa se administró mediante técnicas de terapia de arco volumétrico modulado y de radioterapia de intensidad modulada. Resultados No se vieron cambios significativos en los parámetros de uroflujometría. En el caso de la cistomanometría los datos no mostraron un aumento de la incontinencia urinaria de esfuerzo secundaria, pero sí un incremento del 7% en la incontinencia urinaria de urgencia. Hubo cambios estadísticamente significativos en la reducción de la capacidad vesical, con un deseo miccional fuerte, con urgencia miccional y también en la presión del detrusor con un deseo miccional normal. Además, el estudio de presión/flujo reveló una reducción estadísticamente significativa del volumen de orina residual. Conclusiones El efecto de la prostatectomía y la edad varía según la evolución del estudio urodinámico. Hubo una reducción significativa del volumen de orina residual, así como de la presión del detrusor, con un deseo miccional normal en los pacientes sin prostatectomía y en aquellos menores de 75 años. Además de un aumento en la incontinencia de urgencia, también se produjo un empeoramiento significativo del resultado urodinámico de llenado vesical y una disminución de la capacidad vesical cistomanométrica, con un deseo miccional fuerte y urgencia miccional. Ninguno de estos factores se vio afectado por la edad o la prostatectomía (AU)

Introduction and objectives To evaluate the effect of radical prostatectomy and age on urodynamics before and after intensity-modulated radiation therapy administered to prostate cancer patients. Materials and methods The sample consisted of 40 prostate cancer patients, 22 of whom had undergone a radical prostatectomy. Urodynamic parameters before and after an average of 4.2 months of radiotherapy were measured and compared. External radiotherapy was administered via Volumetric Modulated Arc Therapy (VMAT), Intensity Modulated Radiation Therapy (IMRT) techniques. Results Uroflowmetry presented no significant parameters. In the case of Cystomanometry, the data did not show an increase in secondary stress urinary incontinence, although there is 7 percent increase in urge urinary incontinence. There were statistically significant changes in reduced bladder capacity with a strong desire to void, with an urge to void and also in the detrusor pressure with a normal desire to void. Furthermore, pressure/flow analysis revealed a statistically significant reduction of residual urine volume. Conclusions The effect of prostatectomy and age varies according to the evolution of urodynamics. There was a significant reduction in terms of residual urine volume and detrusor pressure with a normal desire to void in patients without a prostatectomy and in those under 75 years old. In addition to an increase in urge incontinence, there was also a significant worsening of the bladder filling urodynamics and a decrease in the cystomanometric bladder capacity with a strong desire and an urge to void. None of these were modified by age or prostatectomy (AU)

Impact of a radical prostatectomy on the urodynamic results of prostate cancer patients treated with intensity modulated radiation therapy.

INTRODUCTION AND OBJECTIVES: To evaluate the effect of radical prostatectomy and age on urodynamics before and after intensity-modulated radiation therapy administered to prostate cancer patients. MATERIALS AND METHODS: The sample consisted of 40 prostate cancer patients, 22 of whom had undergone a radical prostatectomy. Urodynamic parameters before and after an average of 4.2 months of radiotherapy were measured and compared. External radiotherapy was administered via Volumetric Modulated Arc Therapy (VMAT), Intensity Modulated Radiation Therapy (IMRT) techniques. RESULTS: Uroflowmetry presented no significant parameters. In the case of Cystomanometry, the data did not show an increase in secondary stress urinary incontinence, although there is 7 percent increase in urge urinary incontinence. There were statistically significant changes in reduced bladder capacity with a strong desire to void, with an urge to void and also in the detrusor pressure with a normal desire to void. Furthermore, pressure/flow analysis revealed a statistically significant reduction of residual urine volume. CONCLUSIONS: The effect of prostatectomy and age varies according to the evolution of urodynamics. There was a significant reduction in terms of residual urine volume and detrusor pressure with a normal desire to void in patients without a prostatectomy and in those under 75 years old. In addition to an increase in urge incontinence, there was also a significant worsening of the bladder filling urodynamics and a decrease in the cystomanometric bladder capacity with a strong desire and an urge to void. None of these were modified by age or prostatectomy.

The Role of Occlusal Factors in the Presence of Noncarious Cervical Lesions in Young People: A Case-Control Study.

OBJECTIVE:: The aim of this retrospective case-control study was to evaluate the influence of different occlusal characteristics and self-referred bruxism in the presence of noncarious cervical lesions (NCCLs). METHODS AND MATERIALS:: The participants were 280 students (140 cases and 140 controls), with an average age of 24.5 years, from six schools of dentistry in Spain. Clinical examination was carried out to record the NCCLs and the static and dynamic occlusal characteristics. The side of mastication and bruxism was collected by questionnaire. Data variables were analyzed by means of univariate and multivariate logistic regression. Odds ratios and the respective 95% confidence intervals were calculated ( p<0.05). RESULTS:: The presence of NCCLs was significantly more likely in subjects with protrusive interferences (odds ratio [OR]=1.82); with lateral interferences, especially on the nonworking side (OR= 1.77); or who were self-reported bruxists (OR=1.72). In the multivariate analysis, protrusive interferences, bruxism, age, and the presence of attrition were risk factors for the development of NCCLs. These factors resulted in a model with an area under the receiver-operating characteristic curve of 0.667 and a positive predictive value of 61.43%. CONCLUSIONS:: There was no significant relationship between most occlusal factors and the presence of NCCLs. Only bruxism, protrusive interferences, age, and occlusal wear were risk factors. The predictive model was not sufficiently explanatory. Occlusal factors alone do not appear to be sufficient to explain the presence of NCCLs.

First report of anthelmintic resistance of equine cyathostomins in Cuba.

Anthelmintic resistance in equine cyathostomins has been described worldwide, with resistance to the benzimidazole class being particularly widespread. The status of anthelmintic efficacy in Cuba has been virtually unknown due to the lack of equine labelled products. One recent report documented suboptimal efficacy levels of extra-label albendazole products against cyathostomins, but it remains unknown to which extent benzimidazole resistance exists in the population. The aim of the present study was to evaluate the anthelmintic efficacy of two benzimidazole products labelled for equines, fenbendazole and oxibendazole. A fecal egg count reduction test (FECRT) was carried out on 132 horses aged 4 months to 18 years in 14 herds, belonging to six provinces. Ten herds exhibited signs of resistance to at least one of the benzimidazoles (mean FECRT<90%). Overall, oxibendazole exhibited higher efficacy than fenbendazole (p = 0.0062), and higher efficacy levels were found in horses never dewormed before compared to those treated within 3-12 months prior to the study (p = 0.0015). Pre-treatment larval cultures revealed the presence of large strongyles and cyathostomin larvae in all herds, while only cyathostomin larvae were detected post treatment. The present work is the first report of anthelmintic resistance in equine cyathostomins in Cuba, and suggests pre-selection for resistant strains by extra-label use of albendazole on the studied farms.

Helminth egg excretion in horses kept under tropical conditions-Prevalence, distribution and risk factors.

Increasing levels of anthelmintic resistance observed in equine cyathostomin parasites have led to recommendations of selective anthelmintic treatment strategies to lower the selection pressure favoring resistant populations. This principle is based on determining strongyle fecal egg counts from all herd members, and treating those exceeding a predetermined treatment cutoff. However, epidemiological information is lacking from horses kept under tropical conditions, where parasite burdens may be of a different composition and magnitude compared to those of horses kept under temperate climate conditions. The aim of the present work was to characterize the strongylid fauna in horses kept in tropical Camagüey, Cuba and identify risk factors associated with strongylid and ascarid egg counts. A total of 396 horses from eight different establishments were included in the study. Coprocultures revealed that Strongylus vulgaris and cyathostomins, sensu lato, were detected in all of those establishments. Prevalence and mean value of strongylid eggs per gram of feces were 97% and 1436, respectively. Eggs of Parascaris spp. were observed in 10% of horses. A multivariate mixed linear model identified sex (p=0.022), month (p=0.044), operation type (p=0.037) and time since last deworming (p<0.001) to be significantly associated in with the magnitude of strongylid fecal egg counts. A multivariate logistic regression identified horses less than two years of age (p=0.010) and horses not receiving anthelmintic treatment (p<0.001) to be significantly more likely to harbor Parascaris spp. parasites. The high magnitude and prevalence of strongylid fecal egg counts observed and the common occurrence of S. vulgaris suggest that strongylid parasite burdens are substantially different from those typically observed in managed equines kept under more temperate conditions.

Reappraisal of classical electrocardiographic criteria in detecting accessory pathways with a strict para-Hisian location.

BACKGROUND: Identification of electrocardiographic (ECG) criteria for para-Hisian accessory pathways (APs) is based on a small series of patients. The presence of a negative delta wave in leads V(1) and V(2) has been suggested as an ECG marker of this AP location. OBJECTIVE: To validate these ECG findings in a large series of patients with strict invasive criteria for that location. METHODS: We included 105 patients (39 women, 66 men; mean age 26 ± 12 years, range 5-82 years) with an ECG pattern compatible with preexcitation through an anteroseptal or midseptal AP following established ECG criteria. A para-Hisian AP was defined when the location of its successful catheter ablation coincided with either the largest recordable His bundle electrogram or a His bundle potential of>0.1 mV. Patients without that definition were included in the control group. RESULTS: A para-Hisian location of the AP was found in 52 patients. AP locations of the remaining 53 patients (control group) were anteroseptal (n = 39), midseptal (n = 9), and fasciculoventricular (n = 5). A negative delta wave in leads V(1) and V(2) was observed in 13 patients with para-Hisian APs (sensitivity 25%; specificity 92%). However, the sum of initial r-wave amplitudes in those leads was<0.5 mV in 44 of the patients with para-Hisian APs and in 13 patients of the control group (sensitivity 85%; specificity 75.5%; area under receiver-operator characteristic curve 0.85). CONCLUSIONS: The presence of negative delta waves in leads V(1) and V(2) indicates a poor sensitivity and high specificity to detect APs with a strict definition of para-Hisian location. The sum of initial r-wave amplitudes in those ECG leads could be a useful, adjunctive marker in the noninvasive identification of these challenging APs.

A new algorithm for rhythm discrimination in cardioverter defibrillators based on the initial voltage changes of the ventricular electrogram.

AIMS: Ventricular activation onset is faster in supraventricular beats than in ventricular rhythms. The aim of this study was to evaluate a criterion to differentiate supraventricular (SVT) from ventricular tachycardia (VT) based on the analysis of the initial voltage changes in ICD-stored morphology electrograms. METHODS: Far field ICD-stored EGMs were obtained from 68 VT and 38 SVT episodes in 16 patients. The first EGM peak was detected, three consecutive time epochs were defined within the preceding 80 ms window and the voltage changes with respect to a sinus template were analysed during each time period and combined into a single parameter for rhythm discrimination. RESULTS: The algorithm was tested in an independent validation group of 442 VT and 97 SVT spontaneous episodes obtained from 22 patients with a dual chamber ICD. The area under the receiver-operator characteristics (ROC) curve indicated that the arrhythmia separability with this method was 0.95 (tolerance interval: 0.85-0.99) and 0.98 (0.87-0.99) for the control and validation groups respectively. A specificity of 0.91 was obtained at 95% sensitivity in the validation group. CONCLUSION: The analysis of voltage changes during the initial ventricular activation process is feasible using the far field stored electrograms of an ICD system and yields a high sensitivity and specificity for arrhythmia discrimination.

Effect of occlusal splint and transcutaneous electric nerve stimulation on the signs and symptoms of temporomandibular disorders in patients with bruxism.

A crossed-design experimental study has been made involving simple blind paired data and random assignment to treatment, with the aim of evaluating the action of an occlusal splint with transcutaneous electric nerve stimulation (TENS) upon the manifestations of temporomandibular disorders (TMD) in patients with bruxism. The prevalence of TMD in the 24 patients with bruxism was 62.5%%; the corresponding severity, as determined by the pantographic reproducibility index (PRI), was mild (mean value: 20.71). Clicking and pain in the lateral pterygoid muscle were the most frequent clinical manifestations. The occlusal splint and TENS did not significantly improve the signs and symptoms of TMD in these patients with bruxism.

Determinants of inducibility of ventricular tachycardia.

We analyzed the incidence and predictive factors for induction of clinical ventricular tachycardia (VT) during an electrophysiologic study in 127 patients with structural heart disease and spontaneous VT documented by 12-lead electrocardiography. Eighty-five patients had coronary artery disease (CAD), 24 had idiopathic dilated cardiomyopathy (IDC), and 18 had right ventricular dysplasia (RVD). Clinical variables were age, gender, electrocardiographic patterns of spontaneous arrhythmia, cardiac diagnosis, left ventricular (LV) ejection fraction (EF), infarct location, and presence of LV aneurysm. Clinical VT was induced in 76 patients (60%, group 1) and was not induced in 51 patients (group 2). Clinical VT was induced in 83% of patients with RVD, 58% of patients with CAD, and 50% of patients with IDC (p = 0.07). LVEF tended to be significantly higher in group 1 than in group 2 (p = 0.06). The presence of left QRS axis in the frontal plane during spontaneous VT was significantly associated with a higher inducibility both in the general group (69% vs 46%, p <0.02) and in patients with CAD (70% vs 44%, p <0.02). In patients with CAD, only the presence of a left QRS axis was significantly associated with a higher inducibility. A multivariate analysis identified only the left QRS axis as a significant and independent predictor of induction of clinical VT. The association of a leftward axis with inducibility suggests that vectorial factors in the depolarization wavefronts may be related to inducibility since conventional stimulation is performed from the right ventricle, producing a leftward axis in most cases.

[Predictors of sudden death in coronary artery disease]. / Predictores de muerte súbita en la enfermedad coronaria.

Although advances in the management of acute myocardial infarction have resulted in a decline in long-term risk of sudden death, it continues to be high in certain subsets of patients. Thus, it is important to identify and treat these patients. Left ventricular ejection fraction less than 0.40, frequent premature ventricular ectopy on Holter monitoring, late potentials on signal-averaged electrocardiogram, impaired heart rate variability, abnormal baroreflex sensitivity and inducible sustained monomorphic ventricular tachycardia during electrophysiological study are predictors of sudden death and arrhythmic events. Although the negative predictive value of each factor is high, the positive predictive accuracy is low. Several tests can be combined to obtain higher positive predictive values. In fact, in some studies combined noninvasive tests have been used to select patients for ventricular stimulation study. Some preventive treatment can be applied in these patients. Available data do not justify prophylactic therapy with amiodarone in high-risk survivors of acute myocardial infarction. Sudden death and total mortality have been significantly reduced in postinfarction patients by long-term beta blockade. Hence, beta blockers should be given to all patients with acute myocardial infarction who do not have contraindications to their use. The MADIT study has shown the beneficial effect of implantable cardioverter defibrillator in reducing mortality in patients with prior myocardial infarction, an ejection fraction less than 0.36, asymptomatic nonsustained ventricular tachycardia, and inducible sustained ventricular tachycardia, unsuppressable by procainamide. Besides, several studies are under way to evaluate the prophylactic use of implantable defibrillator for improving survival in high-risk patients.

Usefulness of unipolar electrograms to detect isthmus block after radiofrequency ablation of typical atrial flutter.

BACKGROUND: RS morphology of the unipolar electrogram is associated with propagation of the wave front through the exploring electrode, whereas positive uniphasic (R) unipolar electrograms are characteristic of the end of activation. METHODS AND RESULTS: Unipolar electrograms were recorded in 45 consecutive patients with atrial flutter who were undergoing radiofrequency ablation (RFA). Bidirectional cavotricuspid isthmus (CTI) block was achieved in 44 patients. The unipolar electrogram obtained before RFA at the low anterolateral right atrium during coronary sinus pacing changed from RS, rS, or QS to R or Rs in all patients after clockwise CTI block was obtained. The morphology of unipolar electrograms recorded close to the coronary sinus during pacing from the low anterolateral right atrium changed from RS or rS to R or Rs in all but 4 patients after counterclockwise CTI block. In the patient in whom CTI block was not achieved, the RS morphology of the unipolar electrogram remained unchanged. In 18 patients, the results of the RFA were assessed with only the unipolar electrogram. The unipolar electrogram correctly predicted 100% and 89% of the cases of clockwise and counterclockwise CTI block, respectively. CONCLUSIONS: The creation of CTI block is associated with an easily detectable loss of negative components and development of an R or Rs pattern of the unipolar electrogram recorded close to the ablation line while pacing at the opposite side of the CTI.

Growth efficiency in transgenic tilapia (Oreochromis sp.) carrying a single copy of an homologous cDNA growth hormone.

Growth hormone (GH) has been shown to have a profound impact on fish physiology and metabolism. However, detailed studies in transgenic fish have not been conducted. We have characterized the food conversion efficiency, protein profile, and biochemical correlates of growth rate in transgenic tilapia expressing the tilapia GH cDNA under the control of human cytomegalovirus regulatory sequences. Transgenic tilapia exhibited about 3.6-fold less food consumption than nontransgenic controls (P < 0.001). The food conversion efficiency was significantly (P < 0.05) higher (290%) in transgenic tilapia (2.3 +/- 0.4) than in the control group (0.8 +/- 0.2). Efficiency of growth, synthesis retention, anabolic stimulation, and average protein synthesis were higher in transgenic than in nontransgenic tilapia. Distinctive metabolic differences were found in transgenic juvenile tilapia. We had found differences in hepatic glucose, and in agreement with previous results we observed differences in the level of enzymatic activities in target organs. We conclude that GH-transgenic juvenile tilapia show altered physiological and metabolic conditions and are biologically more efficient.

Rate-dependent conduction block of the crista terminalis in patients with typical atrial flutter: influence on evaluation of cavotricuspid isthmus conduction block.

BACKGROUND: The crista terminalis (CT) has been identified as the posterior boundary of typical atrial flutter (AFL) in the lateral wall (LW) of the right atrium (RA). To study conduction properties across the CT, rapid pacing was performed at both sides of the CT after bidirectional conduction block was achieved in the cavotricuspid isthmus by radiofrequency catheter ablation. METHODS AND RESULTS: In 22 patients (aged 61+/-7 years) with AFL (cycle length, 234+/-23 ms), CT was identified during AFL by double electrograms recorded between the LW and posterior wall (PW). After the ablation procedure, decremental pacing trains were delivered from 600 ms to 2-to-1 local capture at the LW and PW or coronary sinus ostium (CSO). At least 5 bipolar electrograms were recorded along the CT from the high to the low atrium next to the inferior vena cava. No double electrograms were recorded during sinus rhythm in that area. Complete transversal conduction block all along the CT (detected by the appearance of double electrograms at all recording sites and craniocaudal activation sequence on the side opposite to the pacing site) was observed in all patients during pacing from the PW or CSO (cycle length, 334+/-136 ms), but it was fixed in only 4 patients. During pacing from the LW, complete block appeared at a shorter pacing cycle length (281+/-125 ms; P<0.01) and was fixed in 2 patients. In 3 patients, complete block was not achieved. CONCLUSIONS: These data suggest the presence of rate-dependent transversal conduction block at the crista terminalis in patients with typical AFL. Block is usually observed at longer pacing cycle lengths with PW pacing than with LW pacing. This difference may be a critical determinant of the counterclockwise rotation of typical AFL.

Caracterización de una población bruxista y evaluación de la terapéutica mediante análisis cluster / Characterization of a bruxist population and therapeutical evaluation by means of a cluster analysis

El efecto de la férula oclusal y el TENS ha sido estudiado en una muestra de 24 pacientes bruxistas (apretadores y rechinadores) que fueron diagnosticados por medio de un cuestionario y anamnesis. Se estudiaron diferentes variables tanto cualitativas como cuantitativas, atendiendo a aspectos psicológicos, de oclusión tanto estática como dinámica, actualidad electromiográfica e índices electromiográficos en músculos posturales y elevadores y presencia de desarreglos internos de la articulación temporomandibular. El método estadístico utilizado fue el análisis cluster. Los resultados no mostraron claramente una discriminación entre grupos tanto entre apretadores y rechinadores como entre los dos tipos de tratamiento...

[Radiofrequency ablation of ventricular tachycardia in patients with ischemic cardiopathy]. / Ablación de taquicardia ventricular mediante radiofrecuencia en pacientes con cardiopatía isquémica.

PURPOSE: We analyze the efficacy of radiofrequency catheter ablation and the clinical significance of inducible ventricular tachycardia that had never been documented before (non clinical ventricular tachycardia) in patients with ventricular tachycardia and coronary artery disease. METHODS: Thirty-four patients (30 men, aged 61 +/- 10 years, left ventricular ejection fraction 31 +/- 10%) with coronary artery disease and documented clinical ventricular tachycardia underwent radiofrequency ablation. Thirty-four clinical ventricular tachycardia and 11 non clinical ventricular tachycardia were treated with radiofrequency. Initial therapeutic success was considered when none of the ventricular tachycardia treated with radiofrequency could no longer be induced at the last stimulation protocol before discharge. RESULTS: Clinical ventricular tachycardia was successfully ablated in 23 patients (68%). Initial therapeutic success was obtained in 21 patients (62%). In 6 of them, 7 non clinical ventricular tachycardia poor tolerated were also induced. During a mean follow-up of 26 +/- 15 months ventricular tachycardia recurred in 6 patients (29%). Five of the 6 patients who recurred were discharged with no inducible non clinical ventricular tachycardia. Three patients died during the follow-up. Two of them from heart failure (one with previous recurrence) and the other suddenly with documented asystole after loss of consciousness without previous recurrence. CONCLUSIONS: In our series of patients with ventricular tachycardia and coronary artery disease selected for radiofrequency ablation, acute success was obtained in 62%. After a mean follow-up of 2 years, 44% of all the patients were free from ventricular tachycardia. Although the possibility of ventricular tachycardia recurrence is high (29%), the recurrence rate is not increased by the inducibility of non clinical ventricular tachycardia.

[Internal cardioversion with low-energy shocks in atrial fibrillation resistant to external electric cardioversion]. / Cardioversión interna con choques de baja energía en fibrilación auricular resistente a cardioversión eléctrica externa.

BACKGROUND AND OBJECTIVE: Although external electrical cardioversion is effective in most patients with atrial fibrillation, there are cases refractory to external cardioversion. This study is aimed at showing our initial experience with an internal cardioversion system in patients with previous unsuccessful external cardioversion. PATIENTS AND METHODS: Between February, 1997 and September, 1998 nine consecutive patients with spontaneous chronic or persistent atrial fibrillation that failed external cardioversion, were included. Internal cardioversion was performed under sedation with two electrodes that had a 5.5 cm coil placed in the lateral right atrium and coronary sinus. Both electrodes were connected to an external defibrillator capable of delivering R-wave synchronized low-energy biphasic shocks following a minimum RR interval of 500 ms. Energy between 2 J and 10 J was applied until the restoration of sinus rhythm or a maximum of 2 shocks of 10 J. RESULTS: Sinus rhythm was achieved in the nine patients, but in two of them atrial fibrillation recurred after a few beats. Both had underlying structural heart disease. The other 7 patients, 5 of them without structural heart disease, were in sinus rhythm at discharge. No mechanic complications or ventricular arrhythmias were observed. Six patients are in sinus rhythm after 4 +/- 3 months of follow-up. CONCLUSIONS: Low-energy intracardiac cardioversion is useful in some patients with atrial fibrillation that had failed external cardioversion and can be performed without general anesthesia.

Randomized, prospective comparison of four burst pacing algorithms for spontaneous ventricular tachycardia.

"Less aggressive" burst stimulation is more effective in terminating spontaneous monomorphic ventricular tachycardia with a lesser acceleration rate. Higher ventricular tachycardia cycle length and use of 91% coupling interval were independent predictors for pacing termination.

First postpacing interval variability during right ventricular stimulation: a single algorithm for the differential diagnosis of regular tachycardias.

BACKGROUND: Failure to differentiate supraventricular from ventricular arrhythmias is the most frequent cause of inappropriate implantable cardioverter-defibrillator therapies. Although a sudden-onset criterion is available to differentiate sustained monomorphic ventricular tachycardias (SMVTs) and sinus tachycardias (STs), SMVTs arising during ST and SMVTs gradually accelerating above the cutoff rate can remain undetected. Regular paroxysmal atrial tachycardias (ATs) also can be undetected by onset and stability algorithms. We hypothesized that the first postpacing interval (FPPI) variability after overdrive right ventricular pacing may differentiate SMVTs from STs and ATs. METHODS AND RESULTS: FPPI variability was measured in 23 SMVTs (cycle length [CL] 366+/-50 ms [VT group]), 27 supraventricular tachycardias, 15 episodes of induced or simulated ATs (CL 376+/-29 ms [AT group]), and 12 exercise-related STs (CL 381+/-24 [ST group]). Sequences of trains of 5, 10, and 15 beats were delivered with a CL 40 ms shorter than the tachycardia CL. An FPPI absolute mean difference between consecutive trains of 5 and 10 beats (deltaFPPI) < or =25 ms identified all VTs (mean difference 5+/-7 ms). In the AT group, the deltaFPPI was >25 ms in all sequences (mean difference 129+/-60 ms, P<0.01). In the ST group, the deltaFPPI was >50 ms in all STs (mean difference 118+/-47 ms, P<0.01). CONCLUSIONS: FPPI variability may differentiate SMVT from AT and ST. This criterion is potentially useful in implantable devices that use a single ventricular lead.