Outcomes of a 24/7 service for urgent permanent pacemaker implantation.

INTRODUCTION AND OBJECTIVES: Most of the complications associated with acute and symptomatic bradyarrhythmia (ASB) occur in the time from diagnosis to permanent pacemaker implantation (PPI). We aimed to evaluate the outcomes of an urgent 24/7 PPI service (PPI-24/7) for patients with ASB. METHODS: A total of 664 patients undergoing first-time PPI for ASB were prospectively assessed during 2 periods of identical length (18 months): 341 patients who underwent the procedure during working hours only (PPI-WH), and 323 patients who underwent the procedure after the implementation of the PPI-24/7 service. The primary safety endpoint was established as the cumulative 180-day incidence of complications related to the index arrhythmia and device implant. The primary efficacy endpoint was determined as the average number of hospital stays per patient. RESULTS: The PPI-24/7 period was associated with a significant shortening of the time from diagnosis to implantation (median [interquartile range]): 3hours [2-6] vs 16 [5-21]). The cumulative incidence of patients with complications at 180 days was lower in the PPI-24/7 period: 9% vs 17% (adjusted odds ratio, 0.5; P=.002), due to a significant reduction in preimplant complications: 2.5% vs 12% (P <.001). The average number of hospital stays was reduced by 2 per patient in the PPI-24/7 period (nonparametric P <.001). PPI-24/7 implants performed outside working hours (n=178) were safe, with a 180-day cumulative incidence in procedure-related complications of 3.9%. CONCLUSIONS: Among patients with ASB, PPI-24/7 was associated with a significant reduction in patient morbidity and efficient hospital resource use.

Clinical and economic outcomes of a systematic same-day discharge programme after pulmonary vein isolation: comparison between cryoballoon vs. radiofrequency ablation.

AIMS: Same-day discharge (SDD) is feasible after pulmonary vein isolation (PVI). We aim to compare prospectively cryoballoon (CRYO) vs. radiofrequency (RF) ablation in a systematic SDD programme. METHODS AND RESULTS: We prospectively analysed the 617 scheduled PVI performed consecutively at our institution (n = 377 CRYO, n = 240 RF) from 1 April 2019 to 31 December 2022 within a systematic programme of SDD. The feasibility of SDD, the 10-day incidence of urgent/unplanned medical care after discharge (UUC-10), and the cost per procedure due to hospital resource use were studied. The 100 procedures performed during the previous year, in which patients were systematically hospitalized, were used as a control group. Same-day discharge was achieved in 585/617 (95%) procedures, with a significant trend towards a higher monthly SDD rate from 2019 to 2022 (P = 0.03). The frequency of SDD was similar in CRYO (356/377; 94%) vs. RF (229/240; 95%). After SDD, the UUC-10 was 66/585 (11.3%), being similar for CRYO (41/356; 11.5%) and RF (25/229; 10.9%); P = 0.8 (log-rank test). Of these, 10 patients were re-hospitalized, with an identical rate in CRYO-treated (6/356; 1.7%) and RF-treated (4/229; 1.7%) patients and owing to similar causes (4 haematomas, 4 pericarditis, and 2 symptomatic sinus node dysfunction). Same-day discharge was associated with an average savings per procedure of 63% (P < 0.001), but no differences were found between the CRYO and RF (P = 0.8). CONCLUSION: In a systematic SDD programme, feasibility (95%, increasing over time), safety (11% UUC-10, 1.7% re-hospitalizations), and savings (63% per procedure) were similar for CRYO and RF ablation procedures.

Spontaneous Variation of Ventriculo-Atrial Interval after Tachycardia Induction: Determinants and Usefulness in the Diagnosis of Supraventricular Tachycardias with Long Ventriculoatrial Interval.

Background: Determining the mechanism of supraventricular tachycardias with prolongedP ventriculoatrial (VA) intervals is sometimes a challenge. Our objective is to analyse the determinants, time course and diagnostic accuracy (atypical atrioventricular nodal reentrant tachycardias [AVNRT] versus orthodromic reentrant tachycardias through an accessory pathway [ORT]) of spontaneous VA intervals variation in patients with narrow QRS tachycardias and prolonged VA. Methods: A total of 156 induced tachycardias were studied (44 with atypical AVNRT and 112 with ORT). Two sets of 10 measurements were performed for each patient­after tachycardia induction and one minute later. VA and VV intervals were determined. Results: The difference between the longest and the shortest VA interval (Dif-VA) correlates significantly with the diagnosis of atypical AVNRT (C coefficient = 0.95 and 0.85 after induction and at one minute, respectively; p < 0.001). A Dif-VA ≥ 15 ms presents a sensitivity and specificity for atypical AVNRT of 50% and 99%, respectively after induction, and of 27% and 100% one minute later. We found a robust and significant correlation between the fluctuations of VV and VA intervals in atypical AVNRTs (Coefficient Rho: 0.56 and 0.76, after induction and at one minute, respectively; p < 0.001 for both) but not in ORTs. Conclusions: The analysis of VA interval variability after induction and one minute later correctly discriminates atypical AVNRT from ORT in almost all cases.

Cycle length of nonsustanied ventricular tachycardias among ICD patients: implications on subsequent appropriate therapies.

BACKGROUND: ICD patients with episodes of nonsustained ventricular tachycardias (NSVT) are at risk of appropriate therapies. However, the relationship between the cycle length (CL) of such NSVTs and the subsequent incidence of appropriate interventions is unknown. METHODS: 416 ICD patients with LVEF < 45% were studied. ICD programming was standardized. NSVT was defined as any VT of 5 or more beats at ≥ 150 bpm occurred in the first 6 months after implantation that terminated spontaneously and was not preceded by any appropriate therapy. The mean follow-up was 41 ± 27 months. RESULTS: We analyzed 2201 NSVTs (mean CL = 323 ms) that occurred in 250 patients; 111 of such episodes were fast (CL ≤ 300 ms). Secondary prevention (HR = 1.7; p < 0.001), number of NSVT episodes (HR = 1.05; 95% CI 1.04-1.07; p < 0.001) and beta-blocker treatment (HR = 0.7; p = 0.04) were independent predictors of appropriate interventions; however, the mean CL of NSVTs was not (p = 0.6). There was a correlation between the mean CL of NSVTs and the CL of the first monomorphic VT: r = 0.88; p < 0.001. This correlation was especially robust in individuals with > 5 NSVTs (r = 0.97; p < 0.001), with an agreement between both values greater than 95%. Patients with any fast NSVT experienced a higher incidence of VF episodes (26%) compared to those without NVSTs (3%) or with only slow NSVTs (7%); p < 0.001. CONCLUSIONS: Unlike the burden, the CL of NSVTs is not a predictor of subsequent appropriate interventions. However, there is a close relationship between the CL of NSVTs and that of arrhythmias that will later lead to appropriate therapies.

Timing of Ablation and Prognosis of Patients With Electrical Storm and Scar-Related Left Ventricular Dysfunction.

Although radiofrequency catheter ablation (RFCA) is indicated in electrical storm (ES) refractory to antiarrhythmic drugs, its most appropriate timing has not been determined. Our objective is to analyse the impact of the timing of RFCA on 30-day mortality in patients with ES and previous scar-related systolic dysfunction. In this multi-centre study, we analysed 104 patients (age: 72 ± 10, left ventricular ejection fraction: 30 ± 6%) attended consecutively due to an ES caused by monomorphic ventricular tachycardia. Sixty-four subjects were treated with RFCA (mean time from admission = 83 ± 67 hours) and 40 were not. Upon admission 25 (24%) individuals had severe heart failure. Mortality rate at 30 days was 24 (23%) patients. RFCA was associated with a reduction of 30-day mortality (hazard ratio = 0.2; p = 0.008). After showing a positive correlation between the time of the RFCA (hours) and survival at 30 days (C-statistic = 0.77; p <0.001), we found that only subjects ablated >48 hours after admission had lower mortality at 30 days than those treated conservatively: 38% (no RFCA) versus 30% (RFCA ≤48 hours) versus 7% (RFCA >48 hours) (adjusted hazard ratio for RFCA >48 hours vs others = 0.2; p = 0.007). Among the patients ablated, those who were non-inducible had lower 30-day mortality: 8% versus 29% (p = 0.03). Extracorporeal membrane oxygenation was associated with a higher rate of non-inducibility in RFCA >48 hours (100% vs 76%; p = 0.03), but not in RFCA ≤48 hours (60% vs 60%; p = 1). In conclusion, among high-risk patients with ES, RFCA performed >48 hours after admission is associated with a reduction in 30-day mortality. In such subjects, the probability of successful RFCA increases when performed under extracorporeal membrane oxygenation support.

Execution data logs of a supercomputer workload over its extended lifetime.

The data of this research describes the logged usage of the Euler cluster located at CIEMAT (Centre for Energy, Environment, and Technology Research), spanning the period between November 2008 and March 2018. The Euler database is open access in Parallel Workload Archive format, available from the PWA repository [1] and Mendeley Data [2], allowing in this way a whole new bunch of research possibilities on computer science.

Resultados en España de la encuesta de la Sociedad Europea de Cardiología sobre terapia de resincronización cardiaca (CRT-Survey II) / Spanish results of the Second European Cardiac resynchronization therapy survey (CRT-Survey II)

Introducción y objetivos: Se describen los resultados en España de la segunda encuesta de la Sociedad Europea de Cardiología sobre terapia de resincronización cardiaca (CRT-Survey II) y se comparan con los de los demás países participantes. Métodos: Pacientes a los que se implantó un dispositivo de terapia de resincronización cardiaca entre octubre de 2015 y diciembre de 2016 en 36 centros participantes. Se recogieron datos sobre las características basales de los pacientes y del implante, y un seguimiento a corto plazo hasta el alta hospitalaria. Resultados: La tasa de éxito del implante fue del 95,9%. La mediana [intervalo intercuartílico] de implantes anuales/centro en España fue significativamente menor que en los demás países participantes: 30 [21-50] frente a 55 [33-100] implantes/año (p=0,00003). En los centros españoles hubo una menor proporción de pacientes de edad ≥ 75 años (el 27,9 frente al 32,4%; p=0,0071), una mayor proporción de pacientes en clase funcional II de la New York Heart Association (el 46,9 frente al 36,9%; p <0,00001) y un mayor porcentaje de pacientes con criterios electrocardiográficos de bloqueo de rama izquierda (el 82,9 frente al 74,6%; p <0,00001). La media de la estancia hospitalaria fue menor en los centros españoles (5,8+/-8,5 frente a 6,4+/-11,6; p <0,00001) y una mayor proporción de pacientes recibieron un cable de ventrículo izquierdo cuadripolar (el 74 frente al 56%; p <0,00001) y fueron seguidos a distancia (el 55,8 frente al 27,7%; p <0,00001). Conclusiones: La encuesta CRT-Survey II muestra que en España hay una menor proporción de pacientes de 75 o más años que reciben un dispositivo de terapia de resincronización cardiaca, una mayor proporción de pacientes en clase funcional II de la New York Heart Association, con bloqueo completo de la rama izquierda del haz de His y con seguimiento a distancia, con estancias hospitalarias significativamente menores

Introduction and objectives: We describe the results for Spain of the Second European Cardiac Resynchronization Therapy Survey (CRT-Survey II) and compare them with those of the other participating countries. Methods: We included patients undergoing CRT device implantation between October 2015 and December 2016 in 36 participating Spanish centers. We registered the patients' baseline characteristics, implant procedure data, and short-term follow-up information until hospital discharge. Results: Implant success was achieved in 95.9%. The median [interquartile range] annual implantation rate by center was significantly lower in Spain than in the other participating countries: 30 implants/y [21-50] vs 55 implants/y [33-100]; P=.00003. In Spanish centers, there was a lower proportion of patients ≥ 75 years (27.9% vs 32.4%; P=.0071), a higher proportion in NYHA class II (46.9% vs 36.9%, P <.00001), and a higher percentage with electrocardiographic criteria of left bundle branch block (82.9% vs 74.6%; P <.00001). The mean length of hospital stay was significantly lower in Spanish centers (5.8+/-8.5 days vs 6.4+/-11.6; P <.00001). Spanish patients were more likely to receive a quadripolar LV lead (74% vs 56%, P <.00001) and to be followed up by remote monitoring (55.8% vs 27.7%; P <.00001). Conclusions: The CRT-Survey II shows that, compared with other participating countries, fewer patients in Spain aged ≥ 75 years received a CRT device, while more patients were in New York Heart Association functional class II and had left bundle branch block. In addition, the length of hospital stay was shorter, and there was greater use of quadripolar LV leads and remote CRT monitoring

Effectiveness of first versus successive antitachycardia pacing attempts: predictors and clinical consequences.

PURPOSE: Antitachycardia pacing (ATP) terminates the majority (but not all) of slow ventricular tachycardias (S-VT) with a cycle length (CL) > 320 ms. Usually, several ATP therapies are programmed in the S-VT zone. Our objective is to analyse the ATP effectiveness, comparing the first ATP attempt (ATP-1) to the second (ATP-2) and third (ATP-3) attempts. METHODS: We studied 556 S-VT (CL = 354 ± 18). ATP programming was standardized and included three bursts of 15 pulses at 91% of VT CL. RESULTS: ATP effectiveness declined from ATP-1 (436/556: 78%) compared to ATP-2 (24/103: 23%) and ATP-3 (10/79: 13%) (p < 0.01) for all comparisons. The percentage of variation of RR intervals (P-RR, %) was higher prior to effective ATP-1 (2.73 ± 1.45 vs. 1.23 ± 0.9; p < 0.001). After an ineffective ATP-1, the P-RR decreased dramatically, with no differences between episodes terminated or not at ATP-2 (0.6 ± 0.14 vs. 0.44 ± 0.16; p = 0.6) or ATP-3 (0.54 ± 0.15 vs. 0.52 ± 0.14; p = 0.7). The post-pacing interval-CL difference (PPI-TCLd) after an unsuccessful ATP-1 was shorter in episodes terminating at ATP-2 or ATP-3 (180 ± 24 vs. 211 ± 15 ms; p < 0.001). Several independent predictors of ATP efficacy were found, as follows: (a) ATP-1: P-RR, % (OR = 7.3; p < 0.001), beta-blockers (OR = 4.1; p < 0.001) and QRS ≥ 120 ms (OR = 0.3; p < 0.001); (b) ATP-2: PPI-TCLd, ms (OR = 0.94; p = 0.001) and QRS ≥ 120 ms (OR = 0.6; p = 0.04); (c) ATP-3: PPI-TCLd, ms (OR = 0.93; p = 0.009). CONCLUSIONS: The effectiveness of ATP is mainly due to ATP-1. The regularization of RR intervals after ineffective ATP-1 underlies the lower efficacy of successive attempts. Shorter PPI-TCLd is associated with higher effectiveness of ATP-2 and ATP-3. Since a duration of QRS ≥ 120 ms predicts a longer PPI-TCLd, patients with wide QRS complexes have less effective ATP-2 and APT-3.

Spanish Results of the Second European Cardiac Resynchronization Therapy Survey (CRT-Survey II).

INTRODUCTION AND OBJECTIVES: We describe the results for Spain of the Second European Cardiac Resynchronization Therapy Survey (CRT-Survey II) and compare them with those of the other participating countries. METHODS: We included patients undergoing CRT device implantation between October 2015 and December 2016 in 36 participating Spanish centers. We registered the patients' baseline characteristics, implant procedure data, and short-term follow-up information until hospital discharge. RESULTS: Implant success was achieved in 95.9%. The median [interquartile range] annual implantation rate by center was significantly lower in Spain than in the other participating countries: 30 implants/y [21-50] vs 55 implants/y [33-100]; P=.00003. In Spanish centers, there was a lower proportion of patients ≥ 75 years (27.9% vs 32.4%; P=.0071), a higher proportion in New York Heart Association functional class II (46.9% vs 36.9%; P <.00001), and a higher percentage with electrocardiographic criteria of left bundle branch block (82.9% vs 74.6%; P <.00001). The mean length of hospital stay was significantly lower in Spanish centers (5.8±8.5 days vs 6.4±11.6; P <.00001). Spanish patients were more likely to receive a quadripolar LV lead (74% vs 56%; P <.00001) and to be followed up by remote monitoring (55.8% vs 27.7%; P <.00001). CONCLUSIONS: The CRT-Survey II shows that, compared with other participating countries, fewer patients in Spain aged ≥ 75 years received a CRT device, while more patients were in New York Heart Association functional class II and had left bundle branch block. In addition, the length of hospital stay was shorter, and there was greater use of quadripolar LV leads and remote CRT monitoring.

Beta-blocker therapy is associated with a lower incidence of syncope due to fast ventricular tachycardias among implantable cardioverter-defibrillator patients with left ventricular dysfunction: results from a multicenter study.

INTRODUCTION: Among implantable cardioverter-defibrillator (ICD) patients, a substantial proportion of syncopes are due to fast ventricular tachycardias (FVTs). In the experimental models of ventricular tachycardias, the arterial vasoconstriction plays an important role in recovering the arterial pressure. Since beta-blockers increase vascular resistance, we hypothesized that beta-blockers could reduce the occurrence of syncope due to FVTs. Our objective was to determine the relationship between the beta-blocker therapy and the incidence of syncope in FVT (cycle length [CL] 250-320 ms) occurring in ICD patients. Slow VTs were excluded because of the lack of symptoms and VF episodes because of the small number. METHODS AND RESULTS: In this multicenter study, 226 patients (LVEF 31 ± 10%) with single-chamber ICDs were followed. FVT programming was standardized, including antitachycardia pacing (ATP) as initial therapy. Symptoms were correlated with ICD-stored episode data of FVTs. The beta-blocker therapy was determined at each FVT presentation. We analyzed 289 FVTs (CL 291 ± 21 ms; 77% under beta-blockers; median of the duration:8 s) occurring consecutively in 52 ICD patients. The frequency of FVT-related syncope was 22 (7.6%). Beta-blockers were associated with a lower heart rate preceding FVT (85 ± 22 vs. 94 ± 23 bpm; p = 0.009), a higher ATP effectiveness (86 vs. 57%; p < 0.001), a lower duration of episodes (8 [2] vs. 10 [14] s; p < 0.001), and a lower incidence of FVT-related syncope (4.5 vs. 18%; p < 0.001). By logistic regression, a FVT > 8 s (OR = 21; p = 0.003) and the beta-blocker therapy (OR = 0.3; p = 0.012) were found as independent predictors of syncope. CONCLUSION: Among ICD patients with left ventricular dysfunction, beta-blockers are associated with a lower incidence of FVT-related syncope.

Prognostic Significance of Nonsustained Ventricular Tachycardia Episodes Occurring Early After Implantable Cardioverter-Defibrillator Implantation Among Patients With Left Ventricular Dysfunction.

Nonsustained ventricular tachycardias (NSVTs) are frequently observed in patients with left ventricular (LV) dysfunction. The prognostic implications of such NSVTs are conflicting. Our objective was to determine the relation between the burden of NSVT occurring early (within the first 6 months after ICD implant) and prognosis among ICD patients with LV dysfunction. We followed 416 ICD patients (age: 65 ± 11 years; LV ejection fraction: 30 ± 8; ischemic origin: 62%; primary prevention: 63%) with LV dysfunction for 41 ± 27 months. ICD programming was standardized. NSVT was defined as any VT of ≥5 beats at ≥150 beats/min which did not meet the detection criteria occurring within the first 6 months after ICD implant. A total of 250 patients (60%) presented at least one NSVT (median = 2; interquartile range 0 to 7). We classified the patients into 3 groups according to the number of NSVTs: no NSVT (n = 166); 1 to 5 NSVTs (n = 130); and >5 NSVTs (n = 120). The incidence of cardiac mortality (7.2% vs 17.7% vs 31.7%; p = 0.003), hospitalizations for heart failure (10.6% vs 24.4% vs 44.7%; p <0.001), and appropriate shock (15.7% vs 24.8% vs 43.8%; p <0.001) increased significantly with the number of NSVTs. By multivariate analysis, >5 NSVTs were found to be an independent predictor of cardiac mortality (hazard ratio [HR] 1.75; p = 0.03), hospitalization due to heart failure (HR 1.72; p = 0.001), and appropriate shock (HR 1.89; p <0.001) but not of inappropriate therapy (HR 0.9; p = 0.6). In conclusion, among ICD patients with LV dysfunction, NSVT episodes occurring in the first 6 months after implant are independently associated with a poor prognosis. Subjects with >5 NSVTs are at the highest risk.

Differences in ventricular tachyarrythmias and antitachycardia pacing effectiveness according to the ICD indication (primary versus secondary prevention): an analysis based on the stored electrograms.

PURPOSE: To determine whether monomorphic ventricular tachycardias (VTs) have different characteristics and/or responses to antitachycardia pacing (ATP) with respect to the indication-primary prevention (PP) versus secondary prevention (SP)-among ICD patients with left ventricular dysfunction. METHODS: We prospectively studied 551 VT (cycle length [CL] 329 ± 35 ms; PP 34%) occurring in 67 ICD patients with left ventricular dysfunction (LVEF 35 ± 8%). ICD programming was standardized, including ATP for slow (CL 400-321 ms) and fast VT (CL 250-320 ms). We analyzed the following aspects: CL, percentage of variability of the 12 RR intervals prior to ATP (P-RR)-which was calculated by dividing the mean difference between each R-R interval with the next one by the CL × 100-and type of termination: immediate (VT ceased immediately upon ATP completion) or delayed (VT persisted after ATP). RESULTS: ATP was successful in 86% of VTs. VTs occurring in SP patients had a lower P-RR, median (IQR) 2.7% (1.2-3.7) versus 1.9% (0.9-3.2); p = 0.002; they terminated immediately after ATP less frequently (27% versus 12%; p < 0.001), and although they were more frequently slow (51% versus 67%; p = 0.01), ATP was less effective in them, 92 versus 80% (p = 0.02). CONCLUSIONS: VTs occurring in SP patients are slower, more stable, and they terminate less frequently at ATP. Therefore, compared with PP, SP patients seem to have fewer self-terminating VTs.

Fragmentation of the paced QRS complex: a marker of antitachycardia pacing effectiveness among ICD patients.

INTRODUCTION: The presence of notches in the paced QRS complex (P-QRS) from the right ventricular apex (RVA) reflects delays in the activation of the left ventricle and may therefore be associated with longer times of stimulus conduction. Our objective was to determine prospectively the relationship between the duration of a notch ≥0.1 mV in the P-QRS (DN) and the effectiveness of antitachycardia pacing (ATP). METHODS AND RESULTS: We followed 286 implantable cardioverter-defibrillator (ICD) patients with left ventricular dysfunction (pacing site: RVA) for 41 ± 27 months. ICD programming was standardized. P-QRS (100 bpm) was obtained at implant (50 mm/s). A total of 955 monomorphic ventricular tachycardias (VTs) with a cycle length of 335 ± 32 milliseconds occurred consecutively in 108 patients. ATP was successful in 84% of VTs. DN correlated with the probability of ineffective ATP (C = 0.67; P < 0.001), the cutoff point with the best sensitivity and specificity being 50 milliseconds. The adjusted mean ATP effectiveness per patient was 76% (95% CI: 72-85). Patients with a DN ≥ 50 milliseconds had a lower ATP efficiency: 67% (56-77) versus 92% (87-97) and a higher proportion of VTs terminated with shocks (SH): 31% (21-42) versus 8% (2-14); P < 0.001 for both. Although the occurrence of VT was similar (41% vs. 40%), the incidence of VT-related SH was higher in patients with a DN ≥ 50 (25% vs. 14%; P = 0.01) in the overall study population (n = 286). CONCLUSIONS: When ATP is applied to the RVA, a DN ≥ 50 milliseconds is associated with a lower ATP effectiveness and a higher risk of SH due to VT.

Morphology of far-field electrograms and antitachycardia pacing effectiveness among fast ventricular tachycardias occurring in ICD patients: a multicenter study.

INTRODUCTION: Fast ventricular tachycardias (FVT) are less likely to be terminated by antitachycardia pacing (ATP). No information is available regarding the ability of far-field electrogram (Ff-EG) morphology (Ff-EGm) in predicting the result of the subsequent ATP. Our objective is to determine the relationship between Ff-EGm and ATP efficacy. METHODS AND RESULTS: In this multicenter study we analyzed 289 FVT (cycle length [CL]: 250-320 milliseconds) occurring consecutively in 52 ICD patients with Medtronic devices (LVEF: 37 ± 6; pacing site: right ventricular apex). FVT programming was standardized, including a single ATP burst as initial therapy. The configuration of Ff-EG was HVA versus HVB. FVTs were classified in QFVT or non-QFVT according to the presence or absence of a negative initial deflection in the Ff-EG. The mean CL was 291 ± 24 milliseconds. We observed 4 Ff-EGm: QS (n = 14, 5%), QR (n = 158, 55%), R (n = 93, 32%), and RS (n = 24, 8%). The ATP effectiveness was 80% (86% in QS, 85% in QR, 74% in R, 62% in RS). The frequency of successful ATP was higher in QFVT: 86 versus 71% (P = 0.002). By logistic regression analysis, a QFVT pattern (OR = 2.3; P = 0.015) remained as an independent predictor of effective ATP. ATP was safer in QFVTs, the frequencies of shock (14% vs 29%; P = 0.002), acceleration (5.1 vs 12.3%; P = 0.02), and syncope (4.6 vs 12.3%; P = 0.01) being lower. CONCLUSIONS: Since ATP is less effective in non-QFVTs, they are less well tolerated. Therefore, the substrate of non-QFVTs may need a specific treatment.

Influence of cycle length variations on antitachycardia pacing effectiveness among ICD patients.

BACKGROUND: Antitachycardia pacing (ATP) fails to terminate 5% to 25% of ventricular tachycardias (VTs) occurring in implantable cardioverter-defibrillator patients. We speculated that small fluctuations in VT cycle length (CL) may be related to the efficacy of subsequent ATP. OBJECTIVE: The purpose of this study was to determine the relationship between the R-R variations of the last 12 R-R intervals before ATP and the efficacy of the first ATP attempt. METHODS: We studied 551 VTs (CL 329±35 ms) occurring in 67 patients. We also analyzed the percentage of variation (P-RR), which was calculated by dividing the mean difference between each R-R interval and the next one by the CL (×100), and the acceleration index (AI), which was calculated by dividing the CL of the first 6 R-R intervals by the CL of the next 6. RESULTS: The effectiveness of the first ATP therapy was 81%, being higher in VTs with AI<1 (85% vs 64%; P<.001). After classifying the events according to the tertiles of P-RR, ATP efficiency was better in higher values of P-RR (VTs with AI<1): 99% (third tertile) vs 85% (second tertile) vs 76% (first tertile), P<.001; and for VTs with AI≥1: 94% vs 68% vs 42% (P<.001). By logistic regression, P-RR (%; odds ratio 2.37; P<.001), and AI<1 (odds ratio 4.17; P<.001) were found to be independent predictors of successful first ATP attempts. CONCLUSION: Small changes in CL increase the effectiveness of ATP significantly. VTs with lower degrees of R-R fluctuations, especially when the pattern is a progressive CL shortening, are infrequently terminated by ATP.

Influence of beta-blocker therapy on antitachycardia pacing effectiveness for monomorphic ventricular tachycardias occurring in implantable cardioverter-defibrillator patients: a dose-dependent effect.

AIMS: To determine, in a non-selected population of 282 implantable cardioverter-defibrillator (ICD) patients with left ventricular dysfunction, the influence of the dose of beta-blockers on antitachycardia pacing (ATP) effectiveness and on the incidence of shock due to monomorphic ventricular tachycardias (VT). METHODS AND RESULTS: We followed 282 ICD patients along 26 +/- 19 months. Antitachycardia pacing and shock programming were standardized. We determined the indexed dose equivalent of beta-blockers (IDE-BB), using metoprolol as a reference, at each VT presentation. The median of IDE-BB was 55 mg/m(2)/day. We analysed 846 VT occurred in 100 patients. The ATP success rate was 84%. Upon classification of the events into three groups (IDE-BB = 0, IDE-BB < 55, and IDE-BB > or = 55), the frequency of effective ATP increased with the IDE-BB: 75 vs. 83 vs. 92% (P < 0.001). According to logistic regression, IDE-BB remained as an independent predictor of effective ATP (P < 0.001) and VT-related shock (P = 0.001). Both the mean ATP effectiveness per patient (67 vs. 80 vs. 91%, P = 0.007) and the mean survival time free of VT-related shock (583 vs. 847 vs. 1158 days, P = 0.019, log-rank test) increased linearly with the dose of beta-blockers. CONCLUSION: Beta-blockers increase the effectiveness of ATP through a dose-dependent effect. As a result, they reduce the incidence of shocks due to VT.