Effects Of Biventricular Pacing Research Articles

Feasibility of CMR Imaging during Biventricular Pacing: Comparison with Invasive Measurement as a Pathway towards a Novel Optimization Strategy.

This prospective pilot study assessed the feasibility of cardiovascular magnetic resonance (CMR) imaging during biventricular (BIV) pacing in patients with a CMR conditional cardiac resynchronization therapy defibrillator (CRT-D) and compared the results with invasive volume measurements. Ten CRT-D patients underwent CMR imaging prior to device implantation (baseline) and six weeks after device implantation, including CRT-on and CRT-off modes. Left ventricular (LV) function, volumes, and strain measurements of LV dyssynchrony and dyscoordination were assessed. Invasive pressure-volume measurements were performed, matching the CRT settings used during CMR. Post-implantation imaging enabled reliable cine assessment, but showed artefacts on late gadolinium enhancement images. After six weeks of CRT, significant reverse remodeling was observed, with a 22.7 ± 11% reduction in LV end-systolic volume during intrinsic rhythm (CRT-off). During CRT-on, the LV ejection fraction significantly improved from 27.4 ± 5.9% to 32.2 ± 8.7% (p < 0.01), and the strain assessment showed the abolition of the left bundle branch block contraction pattern. Invasively measured and CMR-assessed LV hemodynamics during BIV pacing were significantly associated. Post-CRT implantation CMR assessing acute LV pump function is feasible and provides important insights into the effects of BIV pacing on cardiac function and contraction patterns. LV assessment during CMR may constitute a future CRT optimization strategy.

B-PO05-181 HIS BUNDLE PACING PRODUCES MORE PHYSIOLOGICAL VENTRICULAR REPOLARISATION THAN BIVENTRICULAR PACING IN HEART FAILURE WITH LEFT BUNDLE BRANCH BLOCK

Biventricular pacing (BVP) shortens left ventricular activation time (LVAT) in patients with heart failure and left bundle branch block (LBBB). His bundle pacing can correct LBBB (HBP-CRT). The effects of BVP and HBP-CRT on ventricular repolarisation are not known. To measure the effects of HBP-CRT and BVP on LV repolarisation using non-invasive epicardial mapping (ECGI). Participants were recruited in 2 groups. 1) Patients scheduled for BVP for heart failure with LBBB, 2) Individuals with normal QRS and LV function. We defined HBP-CRT as LVAT shortening >10ms. We compared the effects of HBP-CRT and BVP on ECGI-derived dispersion of repolarisation and activation-recovery intervals. 21 HBP-CRT and 21 narrow intrinsic QRS were recruited. LV repolarisation dispersion was reduced by HBP-CRT (-42.0ms, 95%CI: -52.3 to -31.7, p <0.001) but not BVP (11.9ms, -6.2 to 30.1, p=0.182, 18.5ms). Change in LV repolarisation dispersion from BVP to HBP-CRT was -56.5ms (-70.5 to 42.5, p<0.001). LV repolarisation dispersion with HBP-CRT was not different from narrow intrinsic QRS (2.8ms, -16.2 to 21.7, p=0.981). Reduction in LV repolarisation dispersion with HBP-CRT from intrinsic LBBB was similar to LVAT shortening (-45.9ms, 95%CI: -59.3 to -32.4). However, LV activation-recovery interval dispersion was also reduced by HBP-CRT (-56.5 ms, -70.5 to -42.5ms, p<0.001). HBP-CRT can normalise repolarisation dispersion, producing more physiological repolarisation than BVP. This occurs through effects on both activation and action-potential duration. HBP-CRT may prevent ventricular arrhythmias in heart failure with LBBB to a greater extent than BVP.

First in human: the effects of biventricular pacing on cardiac output in severe pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) carries high morbidity and mortality despite available treatment options. In severe PAH, right ventricular (RV) diastolic pressure overload leads to interventricular septal bowing, hindering of left ventricular diastolic filling and reduced cardiac output (CO). Some animal studies suggest that pacing may mitigate this effect. We hypothesized that eliminating late diastole via ventricular pacing could improve CO in human subjects with severe PAH. Using minimal to no sedation, we performed transvenous acute biventricular (BiV) pacing and right heart catheterization in six patients with symptomatic PAH. Hemodynamic measurements were taken at baseline and during BiV pacing at various 20-ms intervals of V-V timing. We compared baseline CO to (1) CO while pacing the RV first by 80ms (mimicking RV-only pacing), and then to (2) CO during pacing at the V-V timing that resulted in the highest CO. All participants were female, PASP 74 ± 14mmHg, QRS duration 104 ± 20ms. Compared with baseline, the CO decreased when the RV was paced first by 80ms (7.2 ± 1.0 vs. 6.2 ± 1.1 L/min, p = 0.028). Pacing with optimal V-V timing produced CO similar to baseline (7.2 ± 1.0 vs. 7.4 ± 1.4, p = 0.92). Two patients (33%) met the predefined endpoint of a 15% increase in CO during pacing at the optimal V-V timing. In symptomatic PAH, V-V optimized acute BiV pacing does not consistently improve CO. However, acute BiV pacing did improve CO in a subset of this cohort. Further research is needed to identify predictors of response to cardiac resynchronization therapy in this population.

Cardiac resynchronization therapy improves left ventricular remodeling and function compared with right ventricular pacing in patients with atrioventricular block.

Right ventricular pacing (RVP) exerts a detrimental effect on left ventricular (LV) remodeling. In patients with atrioventricular block (AVB) that require ventricular pacing, the effect of biventricular pacing (BiVP) versus RVP on LV remodeling and function has not been comprehensively assessed in a meta-analysis. Electric databases MEDLINE and Cochrane Library were retrieved for randomized controlled trials (RCT) comparing RVP and BiVP in patients with AVB. Data on left ventricular ejection fraction (LVEF) and LV volumes were analyzed, stratified by different time points. Eleven RCTs were included in the final analysis. There was a significant reduction of LV end-systolic volume in BiVP compared with RVP, at 3, 6, 12, and 24months follow-up (P < 0.05 for all). BiVP was associated with a decreased LV end-diastolic volume in comparison to RVP at 3, 6, and 12months. Compared with RVP, BiVP had a higher LVEF at all follow-up visits, with mean difference of 5.91, 3.29, 3.9, 6.66, and 8.69% at 3, 6, 12, 24, and beyond 24months follow-up, respectively. The results were not significantly changed in sensitivity analysis after removal of studies with mean baseline LVEF < 50% or excluding studies with ablation-induced AVB. In patients with AVB and bradycardia that require ventricular pacing, BiVP is superior to RVP in improving LV remodeling and function.

The Impact of Cardiac Resynchronization Therapy on the Frequency of Ventricular Arrhythmias

Background: Cardiac resynchronization therapy (CRT) has a proven role in improving mortality in patients with heart failure and ventricular dyssynchrony. However, the effects of biventricular pacing (CRT) on ventricular arrhythmia susceptibility have not been definitely established, and data regarding the risk of ventricular arrhythmias (VA) with CRT has been limited and conflicting.The aim of this study was to compare the burden of VA in the short term before and after an upgrade to a cardiac resynchronization device in order to avoid the long term effects of myocardial remodeling.Methods: We analyzed 44 consecutive patients with severe LV systolic dysfunction who underwent an upgrade from a single chamber defibrillator to biventricular defibrillator due to worsening heart failure status.Results: CRT was associated with a decrease in VA in patients with high arrhythmic burden, in women and in patients older than 65.Conclusion: In this study we provide convincing evidence that in patients with identical electrophysiological substrate, biventricular pacing alone is associated with a decrease in VA burden.

TUGENDHAT: a pilot randomized study on effects of biventricular pacing in patients with bradycardia pacing indication and normal systolic function on heart failure, atrial fibrillation and quality of life (results of 12 month follow-up)

Since the late 1990s, a growing number of clinical studies have indicated that long-term permanent right ventricular (RV) apical pacing will induce severe complications such as development of heart failure, increased burden of atrial fibrillation leading to decreased quality of life. To investigate whether cardiac resynchronization therapy (CRT) using biventricular (BiV) pacing can prevent the development of left ventricular (LV) dysfunction, LV remodelling, worsening of the clinical status and quality of life in chronically RV paced patients with normal LV ejection fraction (EF). A total of 127 patients with Class I indication for permanent cardiac pacing and without established indication for CRT were subjected to 6 months of RV and BiV pacing in a patient-blinded, randomized crossover trial. Treatment effects of BiV pacing were evaluated for LV function, LV remodelling and clinical status. As compared with RV pacing, BiV pacing did not significantly prevent the decrease of LV function [LVEF 61.0 % (36.0; 68.0) vs 60.5 % (38.5; 67.5) in RV pacing], did not change the functional class according to the New York Heart Association [52 % in Class II vs 53.9 % in Class II in RV pacing, and 3.9 % in Class III vs 6.9 % in Class III in RV pacing], and did not present any changes in quality of life [32.5 (18.0; 80.0) vs 32.0 (21.0; 47.0) indexes in RV pacing]. BiV pacing, compared to RV pacing, did not change LV function and quality of life in patients with the absence of LV dysfunction or remodelling, standard bradycardia pacing indications in a pilot phase (12- month follow-up) of the TUGENDHAT trial. The final report will be published after 60-month follow-up termination (Tab. 5, Fig. 3, Ref. 30).

Impact of rate control during atrial fibrillation on the proarrhythmic and antiarrhythmic effects of biventricular pacing

analysis using CHADS2 values for creating 3 categories of patients [6] (CHADS2 score of 0 to 1; 2; 3 to 6). Despite the progressive increase in events with increasing score, the effect of dabigatran was consistent. This demonstrates that the observed benefit with this drug is independent of the baseline CHADS2 value, leading us also to hypothesize that the same may be applicable to apixaban and rivaroxaban. Therefore, in face of these data, the need for an adjustment of the observed hazard ratio to the basal CHADS2 score as far as the metaanalysis endpoints are concerned seems unnecessary. The only exception to this observation may be intracranial bleeding. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [7]. References

Temporary epicardial cardiac resynchronisation versus conventional right ventricular pacing after cardiac surgery: study protocol for a randomised control trial

BackgroundHeart failure patients with stable angina, acute coronary syndromes and valvular heart disease may benefit from revascularisation and/or valve surgery. However, the mortality rate is increased- 5-30%. Biventricular pacing using temporary epicardial wires after surgery is a potential mechanism to improve cardiac function and clinical endpoints.Method/designA multi-centred, prospective, randomised, single-blinded, intervention-control trial of temporary biventricular pacing versus standard pacing. Patients with ischaemic cardiomyopathy, valvular heart disease or both, an ejection fraction ≤ 35% and a conventional indication for cardiac surgery will be recruited from 2 cardiac centres. Baseline investigations will include: an electrocardiogram to confirm sinus rhythm and measure QRS duration; echocardiogram to evaluate left ventricular function and markers of mechanical dyssynchrony; dobutamine echocardiogram for viability and blood tests for renal function and biomarkers of myocardial injury- troponin T and brain naturetic peptide. Blood tests will be repeated at 18, 48 and 72 hours. The principal exclusions will be subjects with permanent atrial arrhythmias, permanent pacemakers, infective endocarditis or end-stage renal disease.After surgery, temporary pacing wires will be attached to the postero-lateral wall of the left ventricle, the right atrium and right ventricle and connected to a triple chamber temporary pacemaker. Subjects will be randomised to receive either temporary biventricular pacing or standard pacing (atrial inhibited pacing or atrial-synchronous right ventricular pacing) for 48 hours.The primary endpoint will be the duration of level 3 care. In brief, this is the requirement for invasive ventilation, multi-organ support or more than one inotrope/vasoconstrictor. Haemodynamic studies will be performed at baseline, 6, 18 and 24 hours after surgery using a pulmonary arterial catheter. Measurements will be taken in the following pacing modes: atrial inhibited; right ventricular only; atrial synchronous-right ventricular; atrial synchronous-left ventricular and biventricular pacing. Optimisation of the atrioventricular and interventricular delay will be performed in the biventricular pacing group at 18 hours. The effect of biventricular pacing on myocardial injury, post operative arrhythmias and renal function will also be quantified.Trial RegistrationClinicalTrials.gov: NCT01027299

Cardiac memory in humans: vectocardiographic quantification in cardiac resynchronization therapy

"Cardiac memory" (CM) refers to a change in repolarization induced by an altered pathway of activation. The effects of biventricular pacing on CM induction have not been investigated. To investigate the development of CM during cardiac resynchronization therapy (CRT) through vectorcardiography (VCG). Eleven patients undergoing CRT were enrolled. VCG was acquired during spontaneous ventricular activation at baseline and during AAI and DDD pacing immediately after and 7, 14, 21 and 60days after the implantation. At 1-week follow-up, during AAI pacing T vector angles significantly changed (azimuth 23±19°; p=0.002; elevation 23±27°; p=0.019) and magnitude significantly increased (baseline 1.13±0.69mV; 7days: 1.77±1.27mV; p=0.026). T angle changes remained stable throughout the follow-up period while a further significant increase in magnitude was observed at 60days (2.21±1.50mV; p=0.01 vs. baseline and p=0.04 vs. 7days). Paced T vector magnitude at implant (2.24±1.25mV) decreased significantly at 7days (1.64±1.26mV; p=0.030) with a further significant decrease at 60days (1.40±1.18mV; p=0.003 vs. baseline; p=0.02 vs. 7days). CRT induces a significant change in T vector magnitude, azimuth, and elevation after resumption of spontaneous ventricular activation after 7days from implantation. While further changes in T vector angle were not observed, after 2months of CRT a significant decrease of paced T vector magnitude and a significant increase of spontaneous T vector magnitude were observed.

Cardiac resynchronization therapy: is systole all that matters?

Next, the majority of patients recruited in this study had an ischaemic aetiology of heart failure; in these patients, it is mandatory to assess e’ as the average of the two or four basal segments to avoid the effect of regional dysfunction. 4 Surprisingly, the average E/e’ was not significantly improved in these patients, but only septal E/e’ that can be influenced by regional dysfunction typical of ischaemic disease. Another important consideration is that diastolic filling may be significantly influenced by AV interval optimization after CRT. In particular, proper AV setting determines an adequate LV filling without blunting the A wave. The authors partially overcome this limitation performing AV interval optimization in all the patients early after CRT implantation but they did not repeat AV interval optimization 6 months after CRT. This operation may have significant relevance after 6 months because different loading conditions, LV reverse remodelling, and also better LV relaxation/contractility may have changed the AV interval that warrants optimal LV filling. Importantly, this study underscored the relevance of assessing BNP levels: they were related to diastolic indices, tended to be higher in non-responders, and significantly decreased after CRT only in responders. Brain natriuretic peptide levels have already been shown to be well correlated with diastolic function, in particular with LV end-diastolic pressure obtained by invasive measurement. 5 Recently, in a sub-analysis of the CARE-HF (CArdiac REsynchronisation-Heart Failure) trial, BNP levels together with the severity of mitral regurgitation at baseline have been shown to be the most powerful independent predictors of mortality in patients undergoing CRT. 6 Therefore, based on these considerations, the reduction in BNP levels after CRT may be used as an important laboratory marker of a positive CRT response and should be assessed together with clinical and echocardiographic responses. Finally, in order to better clarify the effect of CRT on diastolic function, the next step is to explore the effects of biventricular pacing on diastolic dyssynchrony. Similarly to systolic dyssynchrony, diastolic dyssynchrony may occur in heart failure patients with prolonged QRS duration. Previous studies have shown that systolic and diastolic dyssynchrony assessed with tissue Doppler

Left ventricular mechanical activity detected by impedance recording

AimsRecording and analysing impedance fluctuation along the cardiac cycle in the right (RV) and left ventricles (LV).Methods and resultsDuring a biventricular (BiV) implantation procedure, impedance was sequentially derived between the atrial ring electrode and either electrode (tip or ring) of the RV lead [transvalvular impedance (TVI)], and between the atrial ring and either the tip or ring electrode of a coronary sinus lead, positioned in a cardiac vein [left ventricle impedance (LVI)]. The LVI signal was also recorded by the implanted pacemaker at the 1 day and 3 months follow-ups. With intrinsic conduction, TVI showed an average increase of 53 ± 29 Ω during ventricular systole, whereas at the same time, LVI decreased by 45 ± 21 Ω (25 and 23 patients, respectively, out of 28 tested cases). Transvalvular impedance and LVI displayed a similar time course, which appeared to be related to the systolic timing in the RV and LV. Both LVI amplitude and duration decreased as a function of the cardiac rate. The LVI deflection started immediately after LV stimulation, and often anticipated the R-wave sensing after contralateral pacing. At the 3-month follow-up, LVI amplitude was decreased in 70% of cases and increased in the remainder, with a non-significant average change of −5 ± 85% with respect to the acute recordings.ConclusionTransvalvular impedance properties are consistent with the assumption of an inverse relationship with RV volume. Though LVI requires a different physical interpretation, the waveform duration might reflect the timing of LV myocardial contraction. In this hypothesis, the relationship between TVI and LVI could provide insight into the effects of BiV pacing on mechanical synchronization.

The effect of biventricular pacing on cardiac function after weaning from cardiopulmonary bypass in patients with reduced left ventricular function: A pressure–volume loop analysis

The effect of biventricular pacing on cardiac function after weaning from cardiopulmonary bypass in patients with reduced left ventricular function: A pressure–volume loop analysis

Effect of cardiac resynchronization therapy on regional left ventricular function: a speckle tracking strain analysis

The mechanisms associated with cardiac resynchronization therapy (CRT) benefits have been elucidated in part, however little is known about the effects of biventricular pacing (BVP) on regional myocardial contractility. Twenty patients with conventional CRT criteria were studied before and after device implantation. Speckle tracking strain analysis was performed from standard bidimensional acquisitions during different pacing configurations. Longitudinal and transverse strains were measured for the six basal left ventricular (LV) segments. Acute CRT improved LV end-diastolic and end-systolic volumes without significantly modifying LV ejection fraction. Moreover, CRT produced significant changes in regional strain. When compared with spontaneous rhythm, simultaneous BVP caused a significant increase in longitudinal septal strain (-4.8 vs. -7.3%, P = 0.003) and a significant decrease in longitudinal lateral strain (-8.2 vs. -5.9%, P = 0.03). Simultaneous BVP also induced a significant decrease in transverse lateral strain from 17.9 to 10.9% (P = 0.004). In this acute echocardiographic study, BVP decreased lateral wall deformation while improving septal wall contraction, thus potentially improving LV contractile pattern.

Effect of Biventricular Pacing During a Ventricular Sensed Event

Loss of biventricular (BiV) pacing occurs during ventricular sensed events such as frequent ventricular ectopy, nonsustained ventricular tachycardia, and intrinsic atrioventricular nodal conduction, such as in atrial fibrillation. Ventricular sense response (VSR) pacing, a novel cardiac resynchronization therapy pacing strategy, maintains BiV pacing during these sensed ventricular events. Patients who underwent echocardiographic optimization after BiV pacemaker implantation were enrolled, and aortic velocity-time integrals (VTIs) were recorded and compared during intrinsic conduction without pacing, optimized BiV pacing, and intrinsic conduction with VSR pacing alone. Thirty-two patients were enrolled (mean age 68 +/- 11 years, 78% men), with a mean baseline QRS duration of 164 +/- 24 ms and a mean left ventricular ejection fraction of 23 +/- 10%. The mean aortic VTI during intrinsic conduction with VSR pacing was 16.5 +/- 3.6 cm, compared with 15.3 +/- 3.4 cm during intrinsic conduction without pacing (p <0.001). The mean aortic VTI with optimized BiV pacing was 17.3 +/- 3.6 cm, significantly better (p <0.001) compared with intrinsic conduction without pacing. Improvements in aortic VTI were higher with optimized BiV pacing compared with VSR pacing alone (p = 0.02). In the subgroup of patients with left bundle branch block-type activation, the hemodynamic improvements realized with VSR pacing were similar to optimized BiV pacing. Mean aortic VTI improvements with VSR were similar in patients with ischemic and nonischemic cardiomyopathy. In conclusion, a cardiac resynchronization therapy algorithm that maintains BiV pacing during a ventricular sensed event appears to have an aortic VTI response that is significantly better compared with intrinsic conduction without pacing.

Effect of biventricular pacing on ventricular repolarization and functional indices in patients with heart failure: lack of association with arrhythmic events

We prospectively assessed the effects of biventricular (BiV) pacing on electrocardiographic (ECG) and vectorcardiographic (VCG) descriptors of ventricular depolarization and repolarization and their association with appropriate implantable cardioverter defibrillator (ICD) activation. We studied 70 consecutive heart failure (HF) (37 ischaemic) patients (64 males, age 66.3 years) with a history of syncope or sustained ventricular tachycardia (VT) who underwent implantation of a BiV-ICD. An invasive electrophysiological study (EPS) was performed before the implantation and 12-lead digital ECGs before and 30 days after implantation. Serial echocardiographic studies were performed. Follow-up duration was 1 year. Maximum (P < 0.001) and minimum (P = 0.004) QT intervals were significantly decreased, whereas QT dispersion was not altered (P = 0.086). QRS duration was shortened (P < 0.001), whereas QRS dispersion was significantly decreased (P = 0.034). Spatial T and QRS vector amplitudes decreased (P < 0.001, for both), whereas the spatial QRS-T angle was not affected (P = 0.671). Twenty-seven (38.6%) patients, experienced appropriate ICD therapies during follow-up. None of the ECG or VCG parameters (pre- or post-implant) were able to identify patients with appropriate ICD therapies during follow-up. Only the presence of a previous episode of sustained VT (spontaneous or inducible on EPS) was strongly associated with appropriate ICD therapies (multivariate P = 0.00 014; odds ratio 24.5). Improvement or no alteration of ECG and VCG descriptors of ventricular depolarization and repolarization was demonstrated after implantation of a BiV-ICD in HF patients. None of these parameters were associated with appropriate ICD therapies, whereas a previous episode of VT or induction of sustained VT on EPS predicted appropriate ICD treatments.

The effect of biventricular pacing on cardiac function after weaning from cardiopulmonary bypass in patients with reduced left ventricular function: A pressure–volume loop analysis

Patients with severely reduced left ventricular function undergoing coronary artery bypass grafting have increased complication rates. We hypothesized that temporary postoperative atrial synchronous biventricular pacing would improve left ventricular function after cardiopulmonary bypass. A left ventricular pressure-volume catheter was placed in 21 patients undergoing coronary artery bypass grafting (ejection fraction 29% +/- 5%). Pressure-volume loops were obtained after weaning from cardiopulmonary bypass with atrial synchronous biventricular, left ventricular, and right ventricular outflow tract pacing and atrial-only stimulation at 90 beats/min. Steady-state systolic and preload-independent parameters were superior for atrial synchronous biventricular and left ventricular pacing and atrial-only pacing relative to atrial synchronous right ventricular outflow tract pacing (P < .05). Diastolic parameters, excepting maximum negative rate of left ventricular pressure change, were unaffected. No significant differences were observed between atrial synchronous biventricular and left ventricular pacing and atrial-only pacing. Systolic dyssynchrony was significantly lower for atrial synchronous biventricular pacing (21% +/- 5%), atrial synchronous left ventricular pacing (20% +/- 6%), and atrial-only pacing (20% +/- 6%) versus atrial synchronous right ventricular outflow tract pacing (25% +/- 7%, P < .05). Atrioventricular interval during atrial-only stimulation was positively correlated with difference in stroke work between atrial synchronous biventricular pacing and atrial-only pacing (r(2) = 0.78, P > .001). Postoperative atrial synchronous biventricular and left ventricular pacing and atrial-only stimulation significantly improve systolic function relative to atrial synchronous right ventricular outflow tract pacing. If atrioventricular conduction is prolonged, atrial synchronous biventricular pacing is preferable to atrial-only pacing.

The effect of biventricular pacing after coronary artery bypass grafting: A prospective randomized trial of different pacing modes in patients with reduced left ventricular function

Biventricular pacing acutely improves left ventricular function in patients with heart failure and left ventricular dyssynchrony. Pressure-volume loop analysis has shown acute perioperative hemodynamic benefits of biventricular pacing immediately after weaning from cardiopulmonary bypass in patients undergoing coronary artery bypass grafting, but whether these effects can be maintained for the early postoperative period is unclear. We hypothesized that biventricular pacing is superior to atrioventricular universal pacing at right ventricular outflowtract and atrial inhibited pacing in patients undergoing coronary artery bypass grafting. Ninety-four patients (mean age, 67 +/- 9 years; mean ejection fraction, 35% +/- 4%) were prospectively randomized to undergo biventricular, atrioventricular universal, or atrial inhibited pacing at 90 beats/min for 96 postoperative hours. Clinical end points and postoperative hemodynamics, aminoterminal pro-brain natriuretic peptide, inotropic support, atrial fibrillation, ventricular arrhythmias, and renal function were evaluated. Diastolic pulmonary arterial pressure, mean arterial pressure, mixed venous saturation, cardiac index, and cardiac power index did not differ significantly among groups for all time points. Neither raw aminoterminal pro-brain natriuretic peptide nor differential from preoperative values differed significantly among groups at any time point. Median intensive care unit stay (19.5 hours) did not differ significantly by pacing mode. Incidences of postoperative atrial fibrillation were 40% for atrial inhibited, 29% for atrioventricular universal, and 37% for biventricular (differences not significant). Renal function was unaffected by pacing mode. Despite short-term hemodynamic benefits for patients with reduced left ventricular function, biventricular pacing did not lead to improved postoperative hemodynamics or clinical outcome.

Effect of biventricular pacing on ventilatory and perceptual responses to exercise in patients with stable chronic heart failure

Despite the growing evidence supporting the use of biventricular cardiac resynchronization therapy (CRT) in patients with chronic heart failure (CHF), the mechanisms whereby acute hemodynamic improvements lead to improved exertional dyspnea are not precisely known. We hypothesized that improved cardiac function and ventilation-perfusion relations following CRT would reduce ventilatory demand, thereby improving dynamic operating lung volumes and enhancing tidal volume expansion during exercise. This, in turn, would be expected to reduce perceived exertional dyspnea and contribute to improved exercise performance. In a randomized, double-blind, crossover study, we compared cardiovascular, metabolic, ventilatory responses (breathing pattern, operating lung volumes, pulmonary gas exchange) and exertional symptoms in seven stable CHF patients who undertook incremental cardiopulmonary cycle exercise test with CRT switched to the "on" (CRT(on)) or "off" (CRT(off)) modality. Following CRT(on), peak oxygen uptake was significantly increased by 15%, and dyspnea ratings were lower for a given work rate (at work rate of 40 W, dyspnea = 1 +/- 0.4 vs. 2.5 +/- 0.9 Borg units, P < 0.05) and ventilation (at ventilation of 31 l/min, dyspnea = 2 +/- 0.7 vs. 3.3 +/- 1.1 Borg units, P < 0.05). CRT(on) was associated with improvements in ventilatory threshold, oxygen pulse, and oxygen uptake/work rate relationships (10.2 +/- 1 vs. 7.9 +/- 1.3 ml.min(-1).W(-1), P < 0.05). CRT(on) reduced the ventilatory requirement during exercise as well as the steepness of ventilation-CO(2) production slope (35 +/- 4 vs. 45 +/- 7, P < 0.05). Changes in end-expiratory lung volume during exercise were less with CRT(on) than with CRT(off) (0.12 vs. 0.37 liter, P < 0.05), and breathing pattern was correspondingly slower and deeper. Biventricular pacing improved all noninvasive indexes of cardiac function and oxygen delivery during exercise. The decreased ventilatory demand, improved dynamic operating lung volumes, and the increased ability to expand tidal volume during exercise are potential factors in the reduction of exertional dyspnea.

Abstract 4344: Biventricular Pacemaker Therapy Corrects Dyssynchrony in Non-Obstructive Hypertrophic Cardiomyopathy

Background. Previous studies have reported dyssynchrony using Tissue Doppler in patients with hypertrophic cardiomyopathy (HCM). In this study we assessed dyssynchrony using speckle tracking echocardiography (STE) in patients with non-obstructive hypertrophic cardiomyopathy vs a healthy control group and in a subgroup of highly symptomatic patients evaluated the acute effects of biventricular pacing on STE and Tissue Doppler (TDI) derived measures of dyssynchrony. Methods. We studied 48 healthy controls (age 48 ±18yrs, 22 males, LVEF 63 ±5%, QRS 86 ±7ms) and 57 patients with HCM (age 54 ±11yrs, 38 males, LVEF 61 ±7%, QRS 110 ±36ms). A subgroup of 15 symptomatic patients with HCM (Peak VO2&lt;60% predicted) underwent biventricular pacing (age 53 ±12yrs, 12 males, LVEF 61 ±7%, QRS 110 ±32ms). Echocardiography was performed with the pacemaker off (VVi30) and on (DDDR, AV delay 90ms, LV-RV delay 0 – 4ms). Using STE, the standard deviation (SD) in time to peak longitudinal strain (Tϵ-SD), the time to peak longitudinal systolic velocity (Ts) for each of 18 left ventricular segments and the SD of this timing (Ts-SD) was derived. Using TDI dyssynchrony was assessed from the SD of Ts for the basal six segments and the maximum difference in Ts between any two basal segments (Ts-peak[basal]). Results. Using STE, Tϵ-SD (54.99 ±33.61ms vs 24.55 ±21.18ms p&lt;0.001), Ts-SD (71.06 ±32.32ms vs 46.17 ±21.50ms p&lt;0.001) and Ts (155.74 ±23.14ms vs 123.71 ±11.25ms p&lt;0.001) were greater in HCM than in controls. Using STE we demonstrated that biventricular pacing significantly reduced Tϵ-SD and Ts-SD to values similar to those observed in controls (Ts-SD p=0.13). Using TDI we demonstrated that biventricular pacing significantly reduced Ts, Ts-SD, and Ts-peak[basal]. See Table . (All values expressed as mean ±SD) Conclusion. Cardiac resynchronisation therapy significantly reduced dyssynchrony in symptomatic patients with non-obstructive HCM as demonstrated using STE and TDI. Table

Acute and Chronic Hemodynamic Effects of Biventricular Pacing in Patients with Coronary Artery Disease and Lateral LV Wall Infarct

Acute and Chronic Hemodynamic Effects of Biventricular Pacing in Patients with Coronary Artery Disease and Lateral LV Wall Infarct