Right Ventricular Stimulation Research Articles

Direct left ventricular wire pacing during transcatheter aortic valve implantation.

Rapid ventricular pacing is used during balloon aortic valvuloplasty, balloon‑expandable transcatheter aortic valve implantation (TAVI), and for postdilatation. Right ventricular (RV) lead pacing has been regarded as a gold standard. Direct left ventricular (LV) wire pacing has recently been considered safe and effective in TAVI interventions. This study aimed to analyze procedural outcomes of direct LV pacing compared with RV stimulation in unselected patients undergoing TAVI. Direct LV wire pacing was provided via available preshaped guidewires and used only when no predictors of atrioventricular block were present. The primary study objective was the assessment of the efficacy of direct LV wire pacing. The secondary objectives included the evaluation of procedure duration and safety in comparison with the conventional method. A combined endpoint (major adverse cardiovascular event) was defined as the occurrence of death, stroke, venous puncture-related complications, and cardiac tamponade. In 2017 and 2018, 143 patients underwent transfemoral TAVI. Of these, 114 (79.7%) had self‑ ‑expandable valves implanted. Direct LV wire pacing was the dominant method of pacing (82 patients [57.3%]), and its efficacy reached 97.6%. The median (interquartile range) procedure time was shorter in the direct LV wire pacing group (80 [70-90] min vs 85 [70-95] min; P = 0.02). Major adverse cardiovascular events were more frequent in the RV lead pacing group (11.5% vs 4.9%), but no statistical significance was achieved (P = 0.13). Direct LV wire pacing during TAVI is a simple, reproducible, and safe technique, which provides reliable, sustained stimulation with a low complication rate and potential reduction of procedural time.

Echocardiographic assessment of myocardial function during His bundle and right ventricular pacing

In patients with pacemaker (PM) therapy, His bundle stimulation (HBS) may lead to amore synchronous activation of the left ventricle (LV) than conventional right ventricular stimulation (RVS). In this study, we investigated to which extent this effect can be objectified by means of contemporary echocardiographic functional imaging. In all, 15RVS patients (6women, mean age 76.6 ± 4.1years) and 15HBS patients (6women, mean age 74.6 ± 3.7years) underwent echocardiography with and without cardiac pacing. Besides LV end-diastolic volume (EDV), ejection fraction (EF), and global strain (GLS), we measured global and regional myocardial work and LV efficiency based on noninvasive pressure-strain loops. In all HBS patients, optimization of PM settings resulted in immediate changes in myocardial function parameters. With pacing, RVS patients showed ahigher decrease in EF and GLS than HBS patients. Global LV work and LV work efficiency decreased significantly only in RVS patients. Changes in regional and global myocardial function can by proven and quantified by functional echocardiography. In patients under PM therapy, HBS shows functional advantages in comparison to conventional RVS.

Left Ventricular Rapid Pacing Via the Valve Delivery Guidewire in Transcatheter Aortic Valve Replacement

ObjectivesThis study investigated whether left ventricular (LV) stimulation via a guidewire-reduced procedure duration while maintaining efficacy and safety compared with standard right ventricular (RV) stimulation. BackgroundRapid ventricular pacing is necessary to ensure cardiac standstill during transcatheter aortic valve replacement (TAVR). MethodsThis is a prospective, multicenter, single-blinded, superiority, randomized controlled trial. Patients undergoing transfemoral TAVR with a SAPIEN valve (Edwards Lifesciences, Irvine, California) were allocated to LV or RV stimulation. The primary endpoint was procedure duration. Secondary endpoints included efficacy, safety, and cost at 30 days. ResultsBetween May 2017 and May 2018, 307 patients were randomized, but 4 were excluded because they did not receive the intended treatment: 303 patients were analyzed in the LV (n = 151) or RV (n = 152) stimulation groups. Mean procedure duration was significantly shorter in the LV stimulation group (48.4 ± 16.9 min vs. 55.6 ± 26.9 min; p = 0.0013), with a difference of –0.12 (95% confidence interval: –0.20 to –0.05) in the log-transformed procedure duration (p = 0.0012). Effective stimulation was similar in the LV and RV stimulation groups: 124 (84.9%) versus 128 (87.1%) (p = 0.60). Safety of stimulation was also similar in the LV and RV stimulation groups: procedural success occurred in 151 (100%) versus 151 (99.3%) patients (p = 0.99); 30-day MACE-TAVR (major adverse cardiovascular event-transcatheter aortic valve replacement) occurred in 21 (13.9%) versus 26 (17.1%) patients (p = 0.44); fluoroscopy time (min) was lower in the LV stimulation group (13.48 ± 5.98 vs. 14.60 ± 5.59; p = 0.02), as was cost (€18,807 ± 1,318 vs. €19,437 ± 2,318; p = 0.001). ConclusionsCompared with RV stimulation, LV stimulation during TAVR was associated with significantly reduced procedure duration, fluoroscopy time, and cost, with similar efficacy and safety. (Direct Left Ventricular Rapid Pacing Via the Valve Delivery Guide-wire in TAVR [EASY TAVI]; NCT02781896)

Novel approach to discriminate left bundle branch block from nonspecific intraventricular conduction delay using pacing-induced functional left bundle branch block

Left bundle branch block (LBBB) has a predictive value for response to cardiac resynchronization therapy as reported by Zareba et al. (Circulation 123(10):1061-1072, 2011). However, based on ECG criteria, the discrimination between complete LBBB and nonspecific intraventricular conduction delay is challenging. We tested the hypothesis that discrimination can be performed using standard electrophysiological catheters and a simple stimulation protocol. Fifty-nine patients were analyzed retrospectively. Patients were divided into groups of narrow QRS (n = 20), wide QRS of right bundle branch block (RBBB) morphology (n = 14), and wide QRS of LBBB morphology (n = 25). Using a diagnostic catheter placed in the coronary sinus, left ventricular activation was assessed during intrinsic conduction as well as during right ventricular (RV) stimulation. In patients with narrow QRS and RBBB, the Q-LV/QRS ratio was 0.43 ± 0.013 (n = 20) and 0.41 ± 0.026 (n = 14), respectively. In patients with LBBB morphology, the Q-LV/QRS split up into a group of patients with normal (0.43 ± 0.022, n = 7) and a group with delayed left ventricular activation (0.75 ± 0.016, n = 18). By direct comparison of the Q-LV/QRS ratio during intrinsic conduction with the Q-LV/QRS ratio during RV pacing leading to a functional LBBB, a clear distinction between a group of "true LBBB" and another group of "apparent LBBB"/nonspecific intraventricular conduction delay (NICD) could be generated. We present a novel and practical method that might facilitate discrimination between patients with apparent LBBB and true LBBB by comparing Q-LV/QRS ratios during intrinsic activation and during RV stimulation. Although this method can already be directly applied, validation by 3D electrical mapping and prospective correlation to cardiac resynchronization therapy (CRT) response will be required for further translation into clinical practice.

Fragmentation of QRS complex during ventricular pacing is associated with ventricular arrhythmic events in patients with left ventricular dysfunction.

QRS fragmentation (fQRS) during baseline ventricular conduction, a myocardial fibrosis marker, is associated with increased risk of ventricular tachyarrhythmias but may not manifest unless ventricular activation change is provoked. We examined the association of fQRS during right ventricular (RV) pacing with death and ventricular tachyarrhythmia in patients with left ventricular (LV) dysfunction undergoing electrophysiology study (EPS). Study participants had LV dysfunction (ejection fraction<50%) undergoing EPS from January 2002 to May 2014 at Mayo Clinic in Rochester, Minnesota. fQRS during RV stimulation involved>2 notches on R/S waves identified in ≥2 contiguous standard electrocardiographic leads representing anterior, inferior, or lateral ventricular segments. Primary outcomes were ventricular tachyarrhythmias that were symptomatic or required intervention and total and cardiac deaths. In all, 528 patients participated (mean age, 65 years; male sex, 80%). Of them, 312 (59%) had ischemic cardiomyopathy and mean (SD) left ventricular ejection fraction (LVEF) of 33.2% (9.5%); 457 (87%) had implantable cardiac devices (implanted defibrillator, n=380). Mean (SD) follow-up was 3.2 (3.0) years. fQRS during RV pacing was observed in 292 patients (60%) in any ventricular segment. Patients with fQRS during RV pacing had 2.5 higher rate of ventricular tachyarrhythmia events than patients with no fQRS (hazard ratio [95% CI], 2.45 [1.5-4.2]; P<0.01), after correcting for baseline ventricular conduction defect and QRS duration, LVEF, inducible sustained ventricular tachycardia, diabetes mellitus, chronic kidney disease, and ischemic cardiomyopathy. RV stimulation can unmask fQRS, and it is associated with increased risk of ventricular tachyarrhythmia in LV dysfunction.

P924Simulation of electrical fields in cardiac resynchronization therapy and temperature spread in HF ablation

Background: The electrical field (E-field) of the biventricular (BV) stimulation is important for the success of cardiac resynchronization therapy (CRT) in patients with cardiac insufficiency and widened QRS complex. The 3D modeling allows the simulation of CRT and high frequency (HF) ablation. Purpose: The aim of the study was to model different pacing and ablation electrodes and to integrate them into a heart model for the static and dynamic simulation of atrial and BV stimulation and high frequency (HF) ablation in atrial fibrillation (AF). Methods: The modeling and simulation was carried out using the electromagnetic simulation software CST (CST Darmstadt). Five multipolar left ventricular (LV) electrodes, one epicardial LV electrode, four bipolar right atrial (RA) electrodes, two right ventricular (RV) electrodes and one HF ablation catheter were modeled. Selected electrodes were integrated into the Offenburg heart rhythm model for the electrical field simulation. The simulation of an AV node ablation at CRT was performed with RA, RV and LV electrodes and integrated ablation catheter with an 8 mm gold tip. Results: The right atrial stimulation was performed with an amplitude of 1.5 V with a pulse width of 0.5. The far-field potentials generated by the atrial stimulation were perceived by the right and left ventricular electrode. The far-field potential at a distance of 1 mm from the right ventricular electrode tip was 36.1 mV. The far-field potential at a distance of 1 mm from the left ventricular electrode tip was measured with 37.1 mV. The RV and LV stimulation were performed simultaneously at amplitude of 3 V at the LV electrode and 1 V at the RV electrode with a pulse width of 0.5 ms each. The far-field potentials generated by the BV stimulations could be perceived by the RA electrode. The far-field potential at the RA electrode tip was 32.86 mV. AV node ablation was simulated with an applied power of 5 W at 420 kHz and 10 W at 500 kHz at the distal 8 mm ablation electrode. Conclusions: Virtual heart and electrode models as well as the simulations of electrical fields and temperature profiles allow the static and dynamic simulation of atrial synchronous BV stimulation and HF ablation at AF. The 3D simulation of the electrical field and temperature profile may be used to optimize the CRT and AF ablation.

SIGNIFICANCE OF THE ALGORITHMS ON MINIMIZATION OF RIGHT-VENTRICULAR ELECTROSTIMULATION IN PREVENTION OF ATRIAL FIBRILLATION PROGRESSION IN PATIENTS WITH SICK SINUS SYNDROME

Aim. To assess the efficacy of algorithms for minimization of the rightventricular stimulation (MVS) for prevention of atrial fibrillation (AF) progression in patients with sick sinus node syndrome (SSS) and documented AF in anamnesis, comparing to standard bi-chamber electrical stimulation (DDDR). Material and methods. The study was one-center, prospective, randomized trial with consequent 74 patients inclusion, who had indications to permanent DDDR due to SSS and AF in anamnesis. Patients were randomized to DDDR group (n=36) and active MVS (n=38) group. Procedure of electrocardiostimulator (ECS) maintenance was done at 6 months and 1 year. During follow-up visits, information was saved in the ECS memory, as the data on AF burden. Primary endpoints were AF burden and time to persistent AF onset. Results. During the study, there were no significant differences in AF burden between the groups. Median of AF burden was 6,0 min/day (25- 75 percentiles: 0-42 min/day) in DDDR, and 6,0 min/day (25-75 perc.: 0-42 min/day; p=0,67) in MVS group. Persistent AF development was registered in 5 patients, of those 3 (8,6%) in DDDR and in 2 (5,3%) in MVS (HR 1,25; 95% CI 0,2-7,98; p=0,47). Medication or electrocardioversion was done for 9 (25,7%) patients from DDDR and 12 (31,6%) from MVS groups (HR 0,86, 95% CI 0,31-2,38, p=0,39). Conclusion. There was no benefit of MVS algorithms in short term period in decrease of AF burden and in its progression prevention towards persistent AF in SSS patients with the anamnesis of paroxysmal AF, comparing to standard DDDR regimen of ECS.

The influence of right ventricular stimulation on acute response to cardiac resynchronisation therapy.

BackgroundThe contribution of right ventricular (RV) stimulation to cardiac resynchronisation therapy (CRT) remains controversial. RV stimulation might be associated with adverse haemodynamic effects, dependent on intrinsic right bundle branch conduction, presence of scar, RV function and other factors which may partly explain non-response to CRT. This study investigates to what degree RV stimulation modulates response to biventricular (BiV) stimulation in CRT candidates and which baseline factors, assessed by cardiac magnetic resonance imaging, determine this modulation.Methods and resultsForty-one patients (24 (59 %) males, 67 ± 10 years, QRS 153 ± 22 ms, 21 (51 %) ischaemic cardiomyopathy, left ventricular (LV) ejection fraction 25 ± 7 %), who successfully underwent temporary stimulation with pacing leads in the RV apex (RVapex) and left ventricular posterolateral (PL) wall were included. Stroke work, assessed by a conductance catheter, was used to assess acute haemodynamic response during baseline conditions and RVapex, PL (LV) and PL+RVapex (BiV) stimulation.Compared with baseline, stroke work improved similarly during LV and BiV stimulation (∆+ 51 ± 42 % and ∆+ 48 ± 47 %, both p < 0.001), but individual response showed substantial differences between LV and BiV stimulation. Multivariate analysis revealed that RV ejection fraction (β = 1.01, p = 0.02) was an independent predictor for stroke work response during LV stimulation, but not for BiV stimulation. Other parameters, including atrioventricular delay and scar presence and localisation, did not predict stroke work response in CRT.ConclusionThe haemodynamic effect of addition of RVapex stimulation to LV stimulation differs widely among patients receiving CRT. Poor RV function is associated with poor response to LV but not BiV stimulation.Electronic supplementary materialThe online version of this article (doi:10.1007/s12471-015-0770-x) contains supplementary material, which is available to authorized users.

CARDIOSTIMULATION AND RHYTHM DISORDERS IN PATIENTS WITH CHRONIC HEART FAILURE

Chronic heart failure (CHF) is common complication of a variety of cardiovascular diseases. In patients with CHF it common to find atrial and ventricular rhythm disorders. Recently the interest to atrial fibrillation (AF) is growing due to its influence on the prognosis of patients with CHF, combination of CHF with AF has worse outcome comparing to isolated AF or CHF. These patients need to be controlled for their ventricular rate by continuous right-ventricular stimulation. However continuous right- ventricular stimulation leads to worsening of the left ventricle function through complicated mechanisms of synchrony impairment. In dyssynchrony with progression of CHF these patients need cardiac resynchronization therapy. Ventricular rhythm disorders are common in these patients and lead to the increase of death risk, hence such patients need to implant cardioverter-defibrillator, and if with biventricular stimulation there is not only a decrease of death from ventricular arrhythmias, but also decrease of the quantity of onsets of these arrhythmias, so cardiac resynchronizing therapy can prevent AF development in CHF.

Fusion of electrical wave fronts in cardiac resynchronization therapy predicts response: an acute pressure-volume loop study

Purpose: In cardiac resynchronisation therapy (CRT), the contribution of right ventricular (RV) stimulation to overall pump function remains controversial. Recent research suggests that in patients with left bundle branch block, eligible for CRT, optimal hemodynamic benefit can be obtained by fusion of the intrinsic (right bundle branch (RBB)) wave front and the invoked wave front of left ventricular (LV) pacing. RV stimulation would only be necessary in patients with long intrinsic AV-delays since in such cases fusion with the intrinsic RBB wave front would compromise optimal AV-delay. To evaluate this hypothesis, we conducted acute hemodynamic measurements in CRT patients with varying AV-delays during LV only and biventricular (Biv) pacing. Methods: Patients eligible to CRT were included. Prior to CRT implantation, patients underwent a temporary pacing procedure. Temporary leads were placed in the right atrium, RV and at the posterolateral wall, and a conductance catheter was used to acquire left ventricular pressure and volume data. Stroke work (SW) and dP/dtmax were used to assess acute hemodynamic response during RV, LV and Biv pacing. Pacing was performed with a fixed AV-delay of 100ms. Analyses were done for the total study population, as well as for a normal AV-delay and first degree AV-block group. Results: Fifty-seven patients were included (37 (65%) males, age 67±10 years, LVEF 22±13%, QRS 154±21ms, ischemic cardiomyopathy 35 (61%) patients, AV-delay 189±34ms, 18 (32%) first degree AV-block). A positive correlation was observed between AV-delay and SW response to LV only pacing (R2 = 0.08, p = 0.032). No correlation was found during Biv pacing nor in dP/dtmax response. No significant differences were found in SW and dP/dtmax response between LV only and biv pacing in the normal AV-delay group (mean 170±18ms) (ΔSW 35±45% vs 31±50%, p=0.415; Δ dP/dtmax 8±18% vs 12±25%, p=0.258, respectively) and the first degree AV-block group (mean 230±23ms) (ΔSW 45±43% vs 30±46%, p=0.124; Δ dP/dtmax 7±14% vs 5±27%, p=0.652, respectively). Conclusion: The present study revealed that a longer AV-delay was positively correlated with SW response during LV, possibly due to AV optimisation. No differences in acute hemodynamic response were found between both pacing modalities in the normal and first degree AV-block group, suggesting that wave front fusion either by biventricular pacing or by fusion of LV pacing and intrinsic conduction is of minor importance.

High rate right ventricular pacing causes global impairment of myocardial blood flow in an experimental model of heart failure

Purpose: Prolonged right ventricular (RV) pacing at high heart rate (HR) induces progressive left ventricle (LV) dysfunction in the experimental animal. It is unclear whether RV stimulation, either acute or prolonged, may also alter regional and global myocardial blood flow (MBF). The aim of this study is to assess regional and global MBF at spontaneous sinus rhythm and during RV apical pacing at baseline and after 4 weeks of prolonged high rate RV stimulation in a group of minipigs. Methods: Six adult minipigs underwent RV pacing (220 beats/min) for 4 weeks. Positron emission tomography (ECAT HR Plus, Siemens, CTI Inc.) and 2D-echocardiography (ECHO) were performed at baseline (PRE) and soon after interruption of 4 weeks high rate pacing (POST). Global and regional myocardial blood flow (MBF) ([13N]ammonia as a flow tracer) were quantified from PET data at spontaneous HR (PM-off) and during pacing at 20 beats over spontaneous HR (PM-on). LV fractional shortening (FS) was measured from ECHO. Results: From PRE to POST, FS significantly decreased from 37±0.8% to 20±0.5% (p<0.01). Prolonged high rate pacing caused also a significant decrease of global MBF from 1.09±0.24 ml/min/g (mean HR 71 bpm) to 0.78±0.26 ml/min/g (mean HR 83 bpm) (P<0.001) at PM-off and from 1.33±0.40 ml/min/g (mean HR 94 bpm) to 1.12±0.39 ml/min/g (mean HR 103 bpm) (p<0.001) at PM-on. Acute RV pacing induced LV dyssynchrony at ECHO and inhomogeneity of regional MBF distribution (higher flow in the septum than in the lateral wall) at baseline. After 4 weeks pacing acute RV stimulation still caused LV dyssynchrony which was no more able to induce regional MBF inhomogeneity (Table I). Table I MBF values are in ml/min/g. *p<0.001 vs PRE. Conclusions: Prolonged high rate RV pacing in minipigs causes global reduction in LV function and a global decrease of MBF as observed in clinical dilated cardiomyopathy. LV dyssynchrony, caused by acute RV stimulation, is associated with regional differences in MBF only at baseline. These results suggest that prolonged tachycardia more than dyssynchrony causes MBF impairment in RV pacing induced heart failure.

Acute effects of right ventricular pacing on cardiac haemodynamics and transvalvular impedance

To assess the acute side-effects of right ventricular (RV) stimulation applied in apex and mid-septum, in order to establish the optimal lead location in clinical practice. During pacemaker implantation, the ventricular lead was temporarily fixed in the apex and then moved to mid-septum. In both positions, surface and endocardial electrograms and transvalvular impedance (32 cases), left ventricular (LV) pressure (23), and transthoracic echocardiography (10) were acquired with intrinsic activity and VDD pacing. A larger increase in QRS duration was noticed with apical than septal pacing (65±25 vs. 45±29 ms; P<10(-4)). The proportion of cases where RV stimulation affected the transvalvular impedance waveform was higher with apical lead location (56% vs. 20%; P<0.02). VDD pacing at either site reduced the maximum dP/dt by 6% with respect to intrinsic AV conduction (IAVC; P<0.005). The maximum pressure drop taking place in 100 ms was reduced by 6 and 8%, respectively, with apical and septal pacing (P<0.01 vs. IAVC). Apical VDD decreased mitral annulus velocity in early diastole (E') from 7.5±1.4 to 5.9±0.9 cm/s (P<0.02) and prolonged the E-wave deceleration time (DT) from 156±33 to 199±54 ms (P<0.02), while septal pacing induced non-significant modifications in E' and DT. Ventricular stimulation acutely impairs LV systolic and diastolic performance, independent of the pacing site. Septal lead location preserves RV contraction mechanics and reduces the electrical interventricular delay.

Pacing-induced cardiomyopathy in patients with right ventricular stimulation for &gt;15 years

The prevalence of pacing-induced cardiomyopathy (PiCMP) has been reported to be 9% 1 year after implantation. As long-term data are sparse, the aim of our study was to evaluate the prevalence of PiCMP in a cohort of patients with at least 15 years of right ventricular (RV) pacing. Inclusion criteria were RV stimulation for at least 15 years due to atrioventricular block III° and absence of structural heart disease at the time of initial implantation. All patients were examined by echocardiography and spiroergometry. Pacing-induced cardiomyopathy was pre-defined as left ventricular (LV) ejection fraction (LVEF) ≤45%, dyskinesia during RV pacing and absence of other known causes of cardiomyopathy. Twenty-six patients from our outpatient department met the inclusion criteria. Pacing-induced cardiomyopathy was diagnosed in four patients (15.4%). Echocardiography showed significant LV remodelling in PiCMP patients [LVEF 41.0 ± 4.5%, LV end-diastolic diameter (LVEDD) 54.0 ± 2.7 mm] compared with patients with preserved LVEF (LVEF 61.2 ± 5.8%, P = 0.002, LVEDD 45.6 ± 4.0 mm, P= 0.004). There were no significant differences regarding age, gender, duration of RV pacing, heart rate, interventricular mechanical delay, QRS duration or prevalence of sinus rhythm, and arterial hypertension between both groups. The longest intraventricular delay was significantly shorter in patients with preserved LVEF (65.5 ± 43.0 ms) compared with PiCMP patients (112.5 ± 15.0 ms, P= 0.043). Exercise capacity and quality of life did not differ significantly between both groups. Considering the very long duration of RV stimulation in our study population (24.6 ± 6.6 years), the prevalence of PiCMP was remarkably low. Pacing-induced cardiomyopathy was associated with more pronounced intraventricular dyssynchrony.

Biventricular pacing in patients with Tetralogy of Fallot: Non-invasive epicardial mapping and clinical impact

IntroductionPatients who have undergone repair of Tetralogy of Fallot (TOF) often present with right bundle branch block. Cardiac resynchronization therapy (CRT) with right ventricular (RV) or biventricular (BiV) stimulation has been proposed as a modality to correct electrical abnormalities and improve cardiac contractility in patients with repaired TOF. We aimed to 1) compare ventricular electrical activation in adults with repaired TOF during RV versus BiV stimulation, using a non-invasive epicardial mapping system, and 2) examine the clinical mid-term effects of BiV resynchronization. Methods9 adults with repaired TOF were implanted with a CRT system and underwent 1) a non-invasive epicardial mapping (n=9) during sinus intrinsic rhythm, RV and BiV pacing 2) a clinical evaluation (n=7) before and after 6months CRT with assessment of NYHA class and exercise capacity. ResultsDuring intrinsic rhythm, non-invasive mapping demonstrated delayed activation of the right compared with the left ventricle in all patients, with the greatest activation delay noted near the infundibulum. However, we observed important differences among patients, in the severity of activation delays. Global activation time and an index of dyssynchrony were improved (p<0.05) during BiV pacing compared with RV pacing and spontaneous rhythm. BiV pacing increased (p<0.05) exercise tolerance and lowered the mean NYHA functional class at 6months of follow up. ConclusionPatients with corrected TOF present with different patterns of ventricular activation. RV stimulation modestly improved RV activation sequence and was associated with a delayed LV activation. Biventricular stimulation significantly decreased right and left ventricular dyssynchrony.

Right ventricular lead positioning does not influence the benefits of cardiac resynchronization therapy in patients with heart failure and atrial fibrillation

Little is known about the optimal right ventricular (RV) pacing site in cardiac resynchronization therapy (CRT). This study compares bi-ventricular pacing at the left ventricular (LV) free wall combined with two different RV stimulation sites: RV outflow tract (RVOT+LV) vs. RV-apex (RVA+LV). Thirty-three patients (32 males) with chronic heart failure, NYHA class III-IV, optimal drug therapy, QRS-duration ≥150 ms, and chronic atrial fibrillation (AF) received CRT with two different RV leads, in the apex (RVA) or outflow tract (RVOT), together with an LV lead, all connected to a bi-ventricular pacemaker. Randomization to pacing in RVOT+LV or RVA+LV was made 1 month after implantation and cross-over to the alternate pacing configuration occurred after 3 months. The median age of patients was 69 ± 10 years, the mean QRS was 179 ± 23 ms, and 58% of patients had ischaemic heart disease. Seven patients had pacemaker rhythm at inclusion and 60% were treated with atrioventricular-junctional ablation before randomization. In the RVA+LV and RVOT+LV pacing modes, 67 and 63% (nonsignificant) responded symptomatically with a decrease of at least 10 points in the Minnesota Living with Heart Failure score. The secondary end-points (6-min walk test, peak oxygen uptake, N-Terminal fragment of B-type Natriuretic Peptide, and left ventricular ejection fraction) showed significant improvement between baseline and CRT, but not between RVOT+LV and RVA+LV. In this randomized controlled study, the exact RV pacing site, either apex or outflow tract, did not influence the benefits of CRT in a group of patients with chronic heart failure and AF. ClinicalTrials.gov ID: NCT00457834.

Right ventricular stimulation threshold at ICD implant predicts device therapy in primary prevention patients with ischaemic heart disease

Myocardial excitability is known (amongst other reasons) to be related to the degree of ischaemia, contractile dysfunction and heart failure. It was hypothesized that the right ventricular (RV) stimulation threshold has prognostic value with respect to the occurrence of ventricular arrhythmias (VAs) and patient survival in recipients of an implantable cardioverter defibrillator (ICD). Ischaemic heart disease patients receiving an ICD at Leiden University Medical Center as primary prevention for sudden cardiac death were included in this study. Right ventricular thresholds were determined at ICD implant. Data were collected on VAs triggering ICD therapy and on all-cause mortality. A total of 689 consecutive patients were included (87% male, age 63 ± 11 years, left ventricular ejection fraction (LVEF) 29 ± 11%) and followed for a median of 28 months. Post-implant RV-threshold was 0.7 ± 0.5 volt (V) at 0.5 ms pulse duration. Best dichotomous separation was reached at a cut-off of 1 V. During follow-up, 167 (24%) patients received appropriate ICD therapy, 88 (13%) had appropriate shocks and 134 (19%) died. Cumulative appropriate shock incidence for patients with RV threshold ≥ 1 V (n = 166) was 16% at 1 year, 24% at 3 years and 34% at 5 years compared with 4, 11 and 17% for patients with an RV-threshold < 1 V (n = 523). Adjusted hazard ratio of RV threshold ≥ 1 V was 2.0 (95% CI: 1.4-2.9) for appropriate therapy, 3.3 (95% CI: 2.0-5.4) for appropriate shocks and 1.6 (95% CI: 1.1-2.5) for mortality. The RV stimulation threshold at ICD implant has a strong independent prognostic value for the occurrence of VAs triggering appropriate ICD therapy, appropriate shocks and mortality.

Biventricular stimulation improves right and left ventricular function after tetralogy of Fallot repair: Acute animal and clinical studies

Optimal treatment of right ventricular (RV) dysfunction observed in patients after tetralogy of Fallot (TOF) repair is unclear. Studies of biventricular (BiV) stimulation in patients with congenital heart disease have been retrospective or have included patients with heterogeneous disorders. The purpose of this study was to determine the effects on cardiac function of stimulating at various cardiac sites in an animal model of RV dysfunction and dyssynchrony and in eight symptomatic adults with repaired TOF. Pulmonary stenosis and regurgitation as well as RV scars were induced in 15 piglets to mimic repaired TOF. The hemodynamic effects of various configurations of RV and BiV stimulation were compared with sinus rhythm (SR) 4 months after surgery. In eight adults with repaired TOF, RV and left ventricular (LV) dP/dt(max) were measured invasively during SR, apical RV stimulation, and BiV stimulation. At 4 months, RV dilation, dysfunction, and dyssynchrony were present in all piglets. RV stimulation caused a decrease in LV function but no change in RV function. In contrast, BiV stimulation significantly improved LV and RV function (P < .05). Echocardiography and epicardial electrical mapping showed activation consistent with right bundle branch block during SR and marked resynchronization during BiV stimulation. In patients with repaired TOF, BiV stimulation increased significantly RV and LV dP/dt(max) (P < .05). In this swine model of RV dysfunction and in adults with repaired TOF, BiV stimulation significantly improved RV and LV function by alleviating electromechanical dyssynchrony.

Intracardiac Echocardiography‐Guided Cardiac Resynchronization Therapy: Technique and Clinical Application

We undertook a pilot investigation to evaluate the feasibility of a novel technique using intracardiac echocardiography (ICE) for intraoperative assessment of cardiac resynchronization therapy (CRT). We evaluated ICE intraoperative imaging of left ventricular (LV) function and aortic valvular flow as well as safety of implementation. ICE was used to guide CRT system lead placement, assess impact of pacing modes, and optimization of device programming. Twenty-three patients underwent ICE imaging. ICE showed global hypokinesis in six patients, regional wall motion abnormality only in 10 patients, and both in seven patients. Optimized CRT modes included mean atrioventricular (AV) interval of 170 ms and interventricular timing using simultaneous right ventricular (RV)-LV pacing (five patients), LV pacing only (one patient), and sequential LV to RV stimulation (15 patients) or RV to LV stimulation (two patients). ICE-guided CRT acutely improved mean left ventricular ejection fraction (LVEF) from 24 +/- 9% to 41 +/- 1% (P < 0.00001). During follow-up of 3-24 (mean 11) months, New York Heart Association class improved in all patients from a mean of 3.2 +/- 0.4 at implant to 1.6 +/- 0.7 (P < 0.0001), with improvement of LVEF from 19 +/- 7% to 34 +/- 12% (P = 0.0001). Actuarial survival was 83% at 12 months. (1) ICE imaging is reliable and safe for continuous intraoperative imaging of LV wall motion, and assesses baseline status and impact of CRT interventions.(2) Intraoperative ICE-guided CRT optimization resulted in an increase in LVEF acutely and consistent improvement in heart failure.(3) Sequential biventricular pacing and longer AV interval programming were more often used in ICE-guided CRT.

Left Ventricular Mechanical Assist Devices and Cardiac Device Interactions: An Observational Case Series

Nonpulsatile left ventricular assist devices (LVADs) are increasingly used for treatment of refractory heart failure. A majority of such patients have implanted cardiac devices, namely implantable cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy-pacemaker (CRT-P) or cardiac resynchronization therapy-defibrillator (CRT-D) devices. However, potential interactions between LVADs and cardiac devices in this category of patients remain unknown. We reviewed case records and device logs of 15 patients with ICDs or CRT-P or CRT-D devices who subsequently had implantation of a VentrAssist LVAD (Ventracor Ltd., Chatswood, Australia) as destination therapy or bridge to heart transplantation. Pacemaker and ICD lead parameters before and after LVAD implant were compared. In addition, ventricular tachyarrhythmia event logs and potential electromagnetic interference reports were evaluated. Right ventricular (RV) sensing decreased in the first 6 months post-LVAD. Mean R-wave amplitude preimplant was 10.9 +/- 5.25 mV compared with 7.2 +/- 3.4 mV during follow-up (P = 0.02). RV impedance also decreased from 642 +/- 240 ohms at baseline to 580 +/- 212 ohms at follow-up (P = 0.007). There was a significant increase in RV stimulation threshold following implantation of the LVAD from 0.8 +/- 0.6 V at baseline to 1.4 +/- 1.0 V in the first 6 months postimplant (P = 0.01). A marked increase in ventricular tachyarrhythmia burden was observed in three patients. One patient displayed electromagnetic interference between the LVAD and defibrillator, resulting in inappropriate defibrillation therapy. LVADs have a definite impact on cardiac devices in respect with alteration of lead parameters, ventricular tachyarrhythmias, and electromagnetic interference.

Ist bei Optimierung der rechtsventrikulären Stimulation eine Resynchronisationstherapie überhaupt erforderlich?

Cardiac resynchronization therapy (CRT) using biventricular stimulation is hampered by coronary venous imponderabilities, complex implantation procedures, technical malfunctions and complications as well as disappointing responder rates. Despite its pathophysiological soundness and some initial success, the use of AV sequential pacing for the treatment of heart failure has been abandoned because right ventricular (RV) apical stimulation may be detrimental for cardiac mechanics, may worsen heart failure and may increase mortality. Attempts at avoiding desynchronizing effects and improving hemodynamics by pacing from alternative RV sites have been numerous but not convincing. Whether patients with left ventricular dysfunction or overt heart failure may benefit from pacing the RV outflow tract or septum, from dual site RV or His bundle stimulation instead of left ventricular based resynchronization is the topic of this review.