Usefulness of ventricular sense response in last-generation cardiac resynchronization therapy devices.

OBJECTIVES: High percentages of pacing were associated to maximal symptomatic and mortality benefit from cardiac resynchronization therapy (CRT). Loss of CRT pacing is linked to intrinsic ventricular activation preceding biventricular pacing (BiV), as it occurs in patients with atrial fibrillation (AF). Last generation CRT devices incorporate the ventricular sense response (VSR) mechanism to maintain biventricular pacing in patients with atrial arrhythmias. This work aimed to characterize electrical dyssynchrony differences among baseline, BiV and VSR pacing, and determine whether the VSR mode is as beneficial as the BiV mode in terms of electrical dyssynchrony. METHODS: Thirty-two patients implanted with CRT devices were retrospectively studied. All patients presented non-ischemic dilated myocardiopathy and complete left bundle branch block (LBBB). Every patient went through baseline, BiV and VSR pacing while recording the 12­lead ECG. Electrical dyssynchrony was assessed by a dyssynchrony index (DIn) obtained from correlation analysis on the 12­lead ECG. RESULTS: When comparing with baseline, VSR pacing improved QRS duration (178 ± 22 ms vs 158 ± 43 ms, baseline vs VSR, p < 0.05) and so did BiV pacing (178 ± 22 ms vs 142 ± 20 ms, baseline vs BiV, p < 0.05). However, electrical dyssynchrony only improved at BiV pacing (2.86±0.6 vs 0.54±0.8, baseline vs BiV, p < 0.05) while VSR showed average DIn values similar to those at baseline. CONCLUSIONS: VSR pacing did not improve the electrical synchrony while did shorten QRS duration in this sample population. Therefore, VSR paced beats would fall in the category of inefficient BiV and may not be the preferred alternative in patients with CRT and AF.

ECG parameters to predict left ventricular electrical delay.

AIMS: Left ventricular (LV) dyssynchrony lengthens the left ventricular electrical delay (LVED), measured from QRS onset to the first peak of the LV electrogram. We constructed an ECG model to predict LVED noninvasively. METHODS: Intrapatient LVED was measured during a baseline vs nonselective His bundle pacing (nHBP) protocol. This setup provided paired synchronic/non-synchronic LVEDs, allowing intrapatient comparisons. Crosscorrelation of leads II and V6 was accomplished and extracted features together with age and gender fed a linear mixed effects model to predict LVED. RESULTS: Hemodynamic increments were consistent with LVED advances under nHBP in a subset of 17 patients (dP/dtmax, baseline: 938.82 ± 241.95 mm Hg/s vs nHBP: 1034.94 ± 253.63 mm Hg/s, p = 6.24e-4). The inclusion of the area under V6 (AV 6) and the time shift of R-peaks obtained from the crosscorrelation signal (CorS) grouped by patient significantly improved LVED estimation with respect to the model based only on QRS duration, age and gender (p = 1.7e-5). CONCLUSIONS: Interlead ECG changes explained LVED, providing clues about the electrical impulse conduction within the left ventricle noninvasively.

Non-selective His bundle pacing with a biphasic waveform: enhancing septal resynchronization.

Aims: His bundle pacing has shown to prevent detrimental effects from right ventricular apical pacing (RVA) and proved to resynchronize many conduction disturbances cases. However, the extent of His bundle pacing resynchronization is limited. An optimized stimulation waveform could expand this limit when implemented in His bundle pacing sets. In this work, we temporarily implemented RVA and Non-selective His bundle pacing with a biphasic anodal-first waveform (AF-nHB) and compared their effects against sinus rhythm (SR). Methods and results: Fifteen patients referred for electrophysiologic study with conduction disturbances, cardiomyopathy and ejection fraction below 35% were enrolled for the study. The following acute parameters were measured: QRS duration, left ventricular activation (RLVT), time of isovolumic contraction (IVCT), ejection fraction (EF), and dP/dtmax. QRS duration and RLVT decreased markedly under AF-nHB (SR: 169 ± 34 ms vs. nHB: 116 ± 31 ms, P < 0.0005) while RVA significantly increased QRS duration (SR: 169 ms vs. RVA: 198 ms, P < 0.05) and did not change RLVT (P = NS). Consistently, IVCT moderately decreased under AF-nHB (SR: 238 ms vs. RVA: 184 ms, P < 0.05 vs. SR) and dP/dtmax showed a 93.35 [mmHg] average increase under AF-nHB against SR. Also, T-wave inversions were observed during AF-nHB immediately after SR and RVA pacing suggesting the occurrence of cardiac memory. Conclusions: AF-nHB corrected bundle branch blocks in patients with severe conduction disturbances, even in those with dilated cardiomiopathy, outstanding from RVA. Also, the occurrence of cardiac memory during AF-nHB turned up as an observational finding of this study.

Estimulación paraseptal permanente: Indicaciones y seguimiento / Permanent Para-Hisian Pacing: Indications and Follow-Up

Introducción Se ha demostrado que la estimulación definitiva en el ápex del ventrículo derecho provoca disincronía ventricular izquierda y eventualmente deterioro contráctil y ello ha llevado a la búsqueda de otros sitios alternativos de estimulación. Las indicaciones y los resultados de la estimulación septal, así como las dificultades técnicas del implante, se encuentran actualmente en estudio. Objetivos Analizar la indicación, la factibilidad y el seguimiento en un grupo de pacientes con estimulación septal parahisiana. Material y métodos Se evaluaron 22 pacientes con edades entre 27 y 68 años, con complejo QRS angosto sin trastorno de conducción intraventricular, con indicación de marcapasos. Se utilizaron catéteres comunes para la aurícula con fijación activa y catéteres con vaina deflectable para la estimulación septal. Durante el implante y el seguimiento se midieron los umbrales y la amplitud de la onda R. Resultados Los umbrales durante el implante fueron menores de 2 voltios/0,50 mseg y la onda R mayor de 5 m V. El tiempo de implante promedio de los catéteres convencionales fue de 30 ± 10 min y el de los catéteres especiales, de 15 ± 5 min. El seguimiento promedio fue de 24 meses. Los umbrales crónicos fueron de 2,5 ± 1,5 voltios con una amplitud de onda R media de 5 ± 2 voltios. Hubo un desplazamiento durante el seguimiento. Conclusiones La estimulación septal parahisiana presentó un índice bajo de complicaciones. El uso de catéteres y vainas especiales redujo el tiempo de implante. La ubicación parahisiana se caracterizó por umbrales más altos y amplitud de la onda R menor que en la comunicada durante estimulación convencional. La estimulación septal parahisiana sería una alternativa válida para evitar la disincronía producida por la estimulación del ventrículo derecho en pacientes sin trastornos de la conducción intraventricular.

Background It has been demonstrated that permanent right ventricular apical pacing produces left ventricular dyssynchrony and decreases contractile function. For this reason other sites of stimulation have been explored. The indications, outcomes and technical difficulties of para-hisian pacing are currently under investigation. Objectives To analyze the indications, feasibility and follow-up in a group of patients undergoing para-hisian pacing. Material and Methods A total of 22 patients between 27 and 68 years with indication of permanent pacing, narrow QRS complexes and preserved intraventricular conduction were evaluated. Activefixation atrial leads and ventricular leads with a deflectable sheath for parahisian stimulation were used. Pacing thresholds and R-wave amplitude were measured during implantation and follow-up. Results During implantation, pacing thresholds were <2 V/0.50 ms and R-wave amplitude was >5 m V. The average duration of placement of conventional leads and special leads were 30±10 min and 15±5 min, respectively. Mean follow-up was 24 months. Chronic thresholds were 2.5±1.5 Volts, and mean R-wave amplitude was 5±2 Volts. One lead displacement was reported during follow-up. Conclusions Para-hisian pacing presented a low rate of complications. The use of special leads and sheaths reduced the implantation time. Compared to conventional pacing, para-hisian pacing presented higher thresholds and lower R-wave amplitude. Para-hisian pacing would be a valid option to avoid ventricular dyssynchrony related to right ventricular pacing in patients with preserved intraventricular conduction.