Haemodynamic effects of changes in atrioventricular and interventricular delay in cardiac resynchronisation therapy show a consistent pattern: analysis of shape, magnitude and relative importance of atrioventricular and interventricular delay

Pilot study to evaluate left-to-right ventricular offset in biventricular pacing-comparison of electrocardiographic imaging and ECG

INTRODUCTION

Biventricular pacing (BiVp) improves outcomes in systolic heart failure patients with electrical dyssynchrony. BiVp is delivered from epicardial left ventricular (LV) and endocardial right ventricular (RV) electrodes. Acute electrical activation changes with different LV-RV stimulation offsets can help guide individually optimized BiVp programming. We sought to study the BiVp ventricular activation with different LV-RV offsets and compare with 12-lead ECG.

METHODS

In five patients with BiVp (63 ± 17-year-old, 80% male, LV ejection fraction 27 ± 6%), we evaluated acute ventricular epicardial activation, varying LV-RV offsets in 20 ms increments from -40 to 80 ms, using electrocardiographic imaging (ECGI) to obtain absolute ventricular electrical uncoupling (VEUabs, absolute difference in average LV and average RV activation time) and total activation time (TAT). For each patient, we calculated the correlation between ECGI and corresponding ECG (3D-QRS-area and QRS duration) with different LV-RV offsets.

RESULTS

The LV-RV offset to attain minimum VEUabs in individual patients ranged 20-60 ms. In all patients, a larger LV-RV offset was required to achieve minimum VEUabs (36 ± 17 ms) or 3D-QRS-area (40 ± 14 ms) than that for minimum TAT (-4 ± 9 ms) or QRS duration (-8 ± 11 ms). In individual patients, 3D-QRS-area correlated with VEUabs (r 0.65 ± 0.24) and QRS duration correlated with TAT (r 0.95 ± 0.02). Minimum VEUabs and minimum 3D-QRS-area were obtained by LV-RV offset within 20 ms of each other in all five patients.

CONCLUSIONS

LV-RV electrical uncoupling, as assessed by ECGI, can be minimized by optimizing LV-RV stimulation offset. 3D-QRS-area is a surrogate to identify LV-RV offset that minimizes LV-RV uncoupling.

Imaging in patients with cardiovascular implantable electronic devices: part 2-imaging after device implantation. A clinical consensus statement of the European Association of Cardiovascular Imaging (EACVI) and the European Heart Rhythm Association (EHRA) of the ESC

Cardiac implantable electronic devices (CIEDs) improve quality of life and prolong survival, but there are additional considerations for cardiovascular imaging after implantation-both for standard indications and for diagnosing and guiding management of device-related complications. This clinical consensus statement (part 2) from the European Association of Cardiovascular Imaging, in collaboration with the European Heart Rhythm Association, provides comprehensive, up-to-date, and evidence-based guidance to cardiologists, cardiac imagers, and pacing specialists regarding the use of imaging in patients after implantation of conventional pacemakers, cardioverter defibrillators, and cardiac resynchronization therapy (CRT) devices. The document summarizes the existing evidence regarding the role and optimal use of various cardiac imaging modalities in patients with suspected CIED-related complications and also discusses CRT optimization, the safety of magnetic resonance imaging in CIED carriers, and describes the role of chest radiography in assessing CIED type, position, and complications. The role of imaging before and during CIED implantation is discussed in a companion document (part 1).

Frontiers in conduction system pacing: treatment of long PR in patients with heart failure

Patients with heart failure who have a prolonged PR interval are at a greater risk of adverse clinical outcomes than those with a normal PR interval. Potential mechanisms of harm relating to prolonged PR intervals include reduced ventricular filling and also the potential progression to a higher degree heart block. There has, however, been relatively little work specifically focusing on isolated PR prolongation as a therapeutic target. Secondary analyses of trials of biventricular pacing in heart failure have suggested that PR prolongation is both a prognostic marker and a promising treatment target. However, while biventricular pacing offers an improved activation pattern, it is nonetheless less physiological than native conduction in patients with a narrow QRS duration, and thus, may not be the ideal option for achieving therapeutic shortening of atrioventricular delay. Conduction system pacing aims to preserve physiological ventricular activation and may therefore be the ideal method for ventricular pacing in patients with isolated PR prolongation. Acute haemodynamic experiments and the recently reported His-optimized pacing evaluated for heart failure (HOPE HF) Randomised Controlled Trial demonstrates the potential benefits of physiological ventricular pacing on patient symptoms and left ventricular function in patients with heart failure.

Cardiac Conduction System Pacing: A Comprehensive Update

The field of cardiac pacing has changed rapidly in the last several years. Since the initial description of His bundle pacing targeting the conduction system, recent advances in pacing the left bundle branch and its fascicles have evolved. The field and investigators' knowledge of conduction system pacing including relevant anatomy and physiology has advanced significantly. The aim of this review is to provide a comprehensive update on recent advances in conduction system pacing.

Variation in optimal hemodynamic atrio-ventricular delay of biventricular pacing with different endocardial left ventricular lead locations using precision hemodynamics

INTRODUCTION

It is not known whether the optimal atrioventricular (AVopt ) delay varies between left ventricular (LV) pacing site during endocardial biventricular pacing (BiVP) and may therefore needs consideration.

METHODS

We assessed the hemodynamic AVopt in patients with chronic heart failure undergoing endocardial LV lead implantation. AVopt was assessed during atrio-BiVP with a "roving LV lead." Up to four locations were studied: mid-lateral wall, mid-septum (or a close alternative), site of greatest hemodynamic improvement, and LV lead implant site. The AVopt was compared to a fixed AV delay of 180 ms.

RESULTS

Seventeen patients were included (12 male, aged 66.5 ± 12.8 years, ejection fraction 26 ± 7%, 16 left bundle branch block or high percentage of right ventricular pacing [RVP], QRS duration 167 ± 27 ms). In most locations (62/63), AVopt increased systolic blood pressure during BiVP compared with RVP (relative improvement 6 mmHg, interquartile range [IQR] 4-9 mmHg). Compared to a fixed AV delay, the hemodynamic improvement at AVopt was higher (1 mmHg, IQR 0.2-2.6 mmHg, p < .001). Within most patients (16/17), we observed a difference in AVopt between pacing sites (median paced AVopt 209 ms, IQR 117-250). Within this range, the hemodynamic impact of these differences was small (median loss 0.6 mmHg, IQR 0.1-2.6 mmHg).

CONCLUSION

Within a patient, different endocardial LV lead locations have slightly different hemodynamic AVopt which are superior to a fixed AV delay. The hemodynamic consequence of applying an optimum from a different lead location is small.

Comparison of methods for delivering cardiac resynchronization therapy: an acute electrical and haemodynamic within-patient comparison of left bundle branch area, His bundle, and biventricular pacing

AIMS

Left bundle branch area pacing (LBBAP) is a promising method for delivering cardiac resynchronization therapy (CRT), but its relative physiological effectiveness compared with His bundle pacing (HBP) is unknown. We conducted a within-patient comparison of HBP, LBBAP, and biventricular pacing (BVP).

METHODS AND RESULTS

Patients referred for CRT were recruited. We assessed electrical response using non-invasive mapping, and acute haemodynamic response using a high-precision haemodynamic protocol. Nineteen patients were recruited: 14 male, mean LVEF of 30%. Twelve had time for BVP measurements. All three modalities reduced total ventricular activation time (TVAT), (ΔTVATHBP -43 ± 14 ms and ΔTVATLBBAP -35 ± 20 ms vs. ΔTVATBVP -19 ± 30 ms, P = 0.03 and P = 0.1, respectively). HBP produced a significantly greater reduction in TVAT compared with LBBAP in all 19 patients (-46 ± 15 ms, -36 ± 17 ms, P = 0.03). His bundle pacing and LBBAP reduced left ventricular activation time (LVAT) more than BVP (ΔLVATHBP -43 ± 16 ms, P < 0.01 vs. BVP, ΔLVATLBBAP -45 ± 17 ms, P < 0.01 vs. BVP, ΔLVATBVP -13 ± 36 ms), with no difference between HBP and LBBAP (P = 0.65). Acute systolic blood pressure was increased by all three modalities. In the 12 with BVP, greater improvement was seen with HBP and LBBAP (6.4 ± 3.8 mmHg BVP, 8.1 ± 3.8 mmHg HBP, P = 0.02 vs. BVP and 8.4 ± 8.2 mmHg for LBBAP, P = 0.3 vs. BVP), with no difference between HBP and LBBAP (P = 0.8).

CONCLUSION

HBP delivered better ventricular resynchronization than LBBAP because right ventricular activation was slower during LBBAP. But LBBAP was not inferior to HBP with respect to LV electrical resynchronization and acute haemodynamic response.

Heart sound-derived systolic time intervals for atrioventricular delay optimization in cardiac resynchronization therapy

BACKGROUND

Phonocardiography (PCG) can be used to determine systolic time intervals (STIs) from ventricular pacing spike to the first heart sound (VS1) and from the first to the second heart sound (S1S2).

OBJECTIVE

The purpose of this study was to investigate the relations between STIs and hemodynamics during atrioventricular (AV) delay optimization of biventricular pacing (BiVP) in animals and patients.

METHODS

Five pigs with AV block underwent BiVP, while PCG was collected from an epicardial accelerometer. In 21 patients undergoing cardiac resynchronization therapy device implantation, PCG was recorded with a pulse generator-embedded microphone. Optimal AV delays derived from shortest VS1 and longest S1S2 were compared with AV delays derived from highest left ventricular pressure (LVP), maximal rate of rise in LVP, and stroke work.

RESULTS

In pigs, VS1 and S1S2 predicted the AV delays with optimal hemodynamics (highest LVP, maximal rate of rise in LVP, and stroke work) by a median error of 2-28 ms, resulting in a median loss of <2% of pump function. In patients, VS1 and S1S2 predicted the optimal AV delay by errors of 32.5 and 37.5 ms, respectively, resulting in 0.2%-0.9% lower LVP and stroke work, which were reduced to 21 and 24 ms in 8 patients with a full-capture AV delay of >180 ms.

CONCLUSION

During BiVP with varying AV delays, close relations exist between PCG-derived STIs and hemodynamic parameters. AV delays advised by PCG-derived STIs cause only a minimal loss of pump function compared with those based on invasive hemodynamic measurements.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01832493.

Basic Principles of Hemodynamics in Pacing

Pacing therapy aims to improve overall cardiac function by normalizing cardiac electrical activation. Although hemodynamic measurements allow the impact of cardiac pacing on cardiac function to be quantified, the protocol is crucial to minimize the effect of noise and achieve greater precision. Multiple steps can be undertaken to optimize accuracy of hemodynamic measurements. These include comparing with a reference state, using an average of a set number of beats, making repeated measurements, ensuring all beats are included, and pacing at faster heart rates. These measurements can aid comparison between different pacing modalities and guide optimal programming.

Acute Hemodynamic Effects of Simultaneous and Sequential Multi-Point Pacing in Heart Failure Patients With an Expected Higher Rate of Sub-response to Cardiac Resynchronization Therapy: Results of Multicenter SYNSEQ Study

The aim of the SYNSEQ (Left Ventricular Synchronous vs. Sequential MultiSpot Pacing for CRT) study was to evaluate the acute hemodynamic response (AHR) of simultaneous (3P-MPP syn) or sequential (3P-MPP seq) multi-3-point-left-ventricular (LV) pacing vs. single point pacing (SPP) in a group of patients at risk of a suboptimal response to cardiac resynchronization therapy (CRT). Twenty five patients with myocardial scar or QRS ≤ 150 or the absence of LBBB (age: 66 ± 12 years, QRS: 159 ± 12 ms, NYHA class II/III, LVEF ≤ 35%) underwent acute hemodynamic assessment by LV + dP/dtmax with a variety of LV pacing configurations at an optimized AV delay. The change in LV + dP/dt max (%ΔLV + dP/dt max) with 3P-MPP syn (15.6%, 95% CI: 8.8%-22.5%) was neither statistically significantly different to 3P-MPP seq (11.8%, 95% CI: 7.6-16.0%) nor to SPP basal (11.5%, 95% CI:7.1-15.9%) or SPP mid (12.2%, 95% CI:7.9-16.5%), but higher than SPP apical (10.6%, 95% CI:5.3-15.9%, p = 0.03). AHR (defined as a %ΔLV + dP/dt max ≥ 10%) varied between pacing configurations: 36% (9/25) for SPP apical, 44% (11/25) for SPP basal, 54% (13/24) for SPP mid, 56% (14/25) for 3P-MPP syn and 48% (11/23) for 3P-MPP seq.Fifteen patients (15/25, 60%) had an AHR in at least one pacing configuration. AHR was observed in 10/13 (77%) patients with a LBBB but only in 5/12 (42%) patients with a non-LBBB (p = 0.11). To conclude, simultaneous or sequential multipoint pacing compared to single point pacing did not improve the acute hemodynamic effect in a suboptimal CRT response population.

Clinical Trial Registration

ClinicalTrials.gov, identifier: NCT02914457.

Optimizing atrio-ventricular delay in pacemakers using potentially implantable physiological biomarkers

BACKGROUND

Hemodynamically optimal atrioventricular (AV) delay can be derived by echocardiography or beat-by-beat blood pressure (BP) measurements, but analysis is labor intensive. Laser Doppler perfusion monitoring measures blood flow and can be incorporated into future implantable cardiac devices. We assess whether laser Doppler can be used instead of BP to optimize AV delay.

METHODS

Fifty eight patients underwent 94 AV delay optimizations with biventricular or His-bundle pacing using laser Doppler and simultaneous noninvasive beat-by-beat BP. Optimal AV delay was defined using a curve of hemodynamic response to switching from AAI (reference state) to DDD (test state) at several AV delays (40-320 ms), with automatic quality control checking precision of the optimum. Five subsequent patients underwent an extended protocol to test the impact of greater numbers of alternations on optimization quality.

RESULTS

55/94 optimizations passed quality control resulting in an optimal AV delay on laser Doppler similar to that derived by BP (median absolute deviation 12 ms). An extended protocol with increasing number of replicates consistently improved quality and reduced disagreement between laser Doppler and BP optima. With only five replicates, no optimization passed quality control, and the median absolute deviation would be 29 ms. These improved progressively until at 50 replicates, all optimizations passed quality control and the median absolute deviation was only 13 ms.

CONCLUSIONS

Laser Doppler perfusion produces hemodynamic optima equivalent to BP. Quality control can be automatic. Adding more replicates, consistently improves quality. Future implantable devices could use such methods to dynamically and reliably optimize AV delays.

Pacemaker and Atrioventricular Junction Ablation in Patients With Atrial Fibrillation—A Systematic Review of Systematic Review and Meta-Analysis

Background

Cardiac resynchronization therapy (CRT) could be considered for heart failure (HF) patients with atrial fibrillation (AF) unless a potent ventricular capture strategy is conducted. However, the benefit of a pacemaker (PM; as part of CRT) in patients with AF and whether atrioventricular junction (or nodal) ablation (AVAB) can improve the prognosis of these patients compared with those treated medically to support ventricular capture are unclear.

Methods and Results

Systematic reviews and meta-analyses investigating the roles of PMs and AVAB in patients with AF were obtained in a search of the PubMed, Embase, and Medline databases and then analyzed with respect to the following outcomes: mortality, left ventricular ejection fraction, and clinical findings including the New York Heart Association class, 6-min walk distance (6MWD), quality of life as assessed in a specific questionnaire, and response to CRT. The quality of the included reviews was assessed using the Assessing the Methodological Quality of Systematic Reviews 2 tool, which includes 16 items. This study was finally based on 13 systematic reviews or meta-analyses. The results showed that patients with AF have higher all-cause mortality rates compared with patients with sinus rhythm and that AVAB can reduce all-cause mortality in patients with AF. Although the functional improvement was better in sinus rhythm than in patients with AF, in the latter, AVAB increased the 6MWD and reduced the CRT nonresponse rate in patients with AF.

Conclusion

Atrial fibrillation is associated with a higher all-cause mortality rate in patients with CRT implantation. AVAB, by increasing the 6MWD and survival, can improve the prognosis of these patients.

Noninvasive cardiac output measurement based optimization in nonresponders of cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) is an important and effective therapy for end-stage heart failure (HF). Nonresponse to CRT is one of the main obstacles to its application in clinical practice. Herein, we investigated the utilization of the optimization technique using noninvasive cardiac output measurement (NICOM) based Mobil-O-Graph device that measures several circulation parameters noninvasively.

METHODS

Seventy-five CRT nonresponder HF patients with an implanted CRT device were included. Patients were randomized equally to 3 groups: NICOM, echocardiographic, and empirical optimization groups. After 3 months of optimization, changes in six minutes walk test (6-MWT), cardiac output (CO), left ventricular ejection fraction (LVEF), and end-systolic volume (LVESV) were measured. New York Heart Association (NYHA) class and hospitalization for HF were also determined.

RESULTS

There were no statistically significant differences among the three groups in terms of demographics, baseline characteristics. In the NICOM group, the 6-MWT, LVEF, CO, and LVESV measurements showed significant improvements compared to baseline values (P < .05). There was no significant improvement in 6-MWT, LVEF, CO, NYHA class, and LVESV in Echo and Empirical groups after 3 months (P > .05). 6-MWT, CO, LVESV percentages, and hospitalization for HF were significantly different between the groups (P < .05). In post hoc analyzes, the percentages of the change in 6-MWT, CO, LVESV, and hospitalization for HF were significantly higher in the NICOM group (P < .017).

CONCLUSIONS

This study suggests that Mobil-O-Graph device optimization according to CO measures does appear to have potential hemodynamic and clinical benefits in nonresponder CRT patients. Use of Mobil-O-Graph device as an option for optimization of CRT devices can be an attractive method of improving CRT outcomes.

Improving haemodynamic optimization of cardiac resynchronization therapy for heart failure

OBJECTIVE

Optimization of cardiac resynchronization therapy using non-invasive haemodynamic parameters produces reliable optima when performed at high atrial paced heart rates. Here we investigate whether this is a result of increased heart rate or atrial pacing itself.

APPROACH

Forty-three patients with cardiac resynchronization therapy underwent haemodynamic optimization of atrioventricular (AV) delay using non-invasive beat-to-beat systolic blood pressure in three states: rest (atrial-sensing, 66  ±  11 bpm), slow atrial pacing (73  ±  12 bpm), and fast atrial pacing (94  ±  10 bpm). A 20-patient subset underwent a fourth optimization, during exercise (80  ±  11 bpm).

MAIN RESULTS

Intraclass correlation coefficient (ICC, quantifying information content mean  ±SE) was 0.20  ±  0.02 for resting sensed optimization, 0.45  ±  0.03 for slow atrial pacing (p   <  0.0001 versus rest-sensed), and 0.52  ±  0.03 for fast atrial pacing (p   =  0.12 versus slow-paced). 78% of the increase in ICC, from sinus rhythm to fast atrial pacing, is achieved by simply atrially pacing just above sinus rate. Atrial pacing increased signal (blood pressure difference between best and worst AV delay) from 6.5  ±  0.6 mmHg at rest to 13.3  ±  1.1 mmHg during slow atrial pacing (p   <  0.0001) and 17.2  ±  1.3 mmHg during fast atrial pacing (p   =  0.003 versus slow atrial pacing). Atrial pacing reduced noise (average SD of systolic blood pressure measurements) from 4.9  ±  0.4 mmHg at rest to 4.1  ±  0.3 mmHg during slow atrial pacing (p   =  0.28). At faster atrial pacing the noise was 4.6  ±  0.3 mmHg (p   =  0.69 versus slow-paced, p   =  0.90 versus rest-sensed). In the exercise subgroup ICC was 0.14  ±  0.02 (p   =  0.97 versus rest-sensed).

SIGNIFICANCE

Atrial pacing, rather than the increase in heart rate, contributes to ~80% of the observed information content improvement from sinus rhythm to fast atrial pacing. This is predominantly through increase in measured signal.

His Resynchronization Versus Biventricular Pacing in Patients With Heart Failure and Left Bundle Branch Block

BACKGROUND

His bundle pacing is a new method for delivering cardiac resynchronization therapy (CRT).

OBJECTIVES

The authors performed a head-to-head, high-precision, acute crossover comparison between His bundle pacing and conventional biventricular CRT, measuring effects on ventricular activation and acute hemodynamic function.

METHODS

Patients with heart failure and left bundle branch block referred for conventional biventricular CRT were recruited. Using noninvasive epicardial electrocardiographic imaging, the authors identified patients in whom His bundle pacing shortened left ventricular activation time. In these patients, the authors compared the hemodynamic effects of His bundle pacing against biventricular pacing using a high-multiple repeated alternation protocol to minimize the effect of noise, as well as comparing effects on ventricular activation.

RESULTS

In 18 of 23 patients, left ventricular activation time was significantly shortened by His bundle pacing. Seventeen patients had a complete electromechanical dataset. In them, His bundle pacing was more effective at delivering ventricular resynchronization than biventricular pacing: greater reduction in QRS duration (-18.6 ms; 95% confidence interval [CI]: -31.6 to -5.7 ms; p = 0.007), left ventricular activation time (-26 ms; 95% CI: -41 to -21 ms; p = 0.002), and left ventricular dyssynchrony index (-11.2 ms; 95% CI: -16.8 to -5.6 ms; p < 0.001). His bundle pacing also produced a greater acute hemodynamic response (4.6 mm Hg; 95% CI: 0.2 to 9.1 mm Hg; p = 0.04). The incremental activation time reduction with His bundle pacing over biventricular pacing correlated with the incremental hemodynamic improvement with His bundle pacing over biventricular pacing (R = 0.70; p = 0.04).

CONCLUSIONS

His resynchronization delivers better ventricular resynchronization, and greater improvement in hemodynamic parameters, than biventricular pacing.

Effect of increasing heart rate on finger photoplethysmography fitness index (PPGF) in subjects with implanted cardiac pacemakers

Finger photoplethysmography (PPG) is a noninvasive method that measures blood volume changes in the finger. The PPG fitness index (PPGF) has been proposed as an index of vascular risk and vascular aging. The objectives of the study were to determine the effects of heart rate (HR) on the PPGF and to determine whether PPGF is influenced by blood pressure (BP) changes. Twenty subjects (78±8 years, 3 female) with permanent cardiac pacemakers or cardioverter defibrillators were prospectively recruited. HR was changed by pacing, in a random order from 60 to 100 bpm and in 10 bpm increments. At each paced HR, the PPGF was derived from a finger photoplethysmogram. Cardiac output (CO), stroke volume (SV) and total peripheral resistance (TPR) were derived from the finger arterial pressure waveform. Brachial blood pressure (BP) was measured by the oscillometric method. This study found that as HR was increased from 60 to 100 bpm, brachial diastolic BP, brachial mean BP and CO were significantly increased (p<0.01), whilst the PPGF and SV were significantly decreased (p<0.001). The effects of HR on the PPGF were influenced by BP, with a decreasing HR effect on the PPGF that resulted from a higher BP. In conclusion, HR was a significant confounder for PPGF and it must be taken into account in analyses of PPGF, when there are large changes or differences in the HR. The magnitude of this effect was BP dependent.

Long-term reverse remodeling by cardiac resynchronization therapy with MultiPoint Pacing: A feasibility study of noninvasive hemodynamics-guided device programming

BACKGROUND

Cardiac resynchronization therapy (CRT) with multipoint left ventricular (LV) pacing (MultiPoint Pacing [MPP]) improves acute hemodynamics and chronic outcomes in comparison to conventional biventricular pacing (BiV), though MPP programming questions persist.

OBJECTIVES

In this multicenter feasibility study, we evaluated the feasibility of using noninvasive systolic blood pressure (SBP) to guide MPP programming and assessed the chronic 6-month echocardiographic CRT response.

METHODS

Patients implanted with MPP-enabled CRT-defibrillator devices underwent noninvasive hemodynamic assessment (finger arterial pressure) during a pacing protocol that included atrial-only pacing and various BiV and MPP configurations. Each configuration was repeated 4 times, alternating with a reference pacing configuration, to calculate the SBP difference relative to reference (ΔSBP). CRT configurations with the greatest ΔSBP were programmed. An independent core laboratory analyzed baseline and 6-month echocardiograms, with CRT response defined as a 6-month reduction in LV end-systolic volume ≥ 15%.

RESULTS

Forty-two patients (71% male; LV ejection fraction 30.3% ± 7.5%; QRS duration 161 ± 19 ms; 26% had ischemic cardiomyopathy) were enrolled in 4 European centers. Relative to atrial-only pacing, the best BiV and best MPP configurations produced significant SBP elevations of 3.1 ± 4.2 (P < .01) and 4.1 ± 4.1 mm Hg (P < .01), respectively (BiV vs MPP; P < .01). Greater SBP elevations were associated with the best MPP compared with the best BiV configurations in 29 of 37 patients completing the pacing protocol (78%). Of MPP-programmed patients completing the 6-month follow-up visit, 23 of 27 (85%) were classified as CRT responders (6-month reduction in LV end-systolic volume 37.0% ± 13.6%).

CONCLUSION

Acute noninvasive hemodynamics after CRT device implantation predominantly favored MPP over BiV programming. MPP programming guided by noninvasive hemodynamics resulted in positive LV structural remodeling.

Cardiac resynchronization therapy: mechanisms of action and scope for further improvement in cardiac function

Aims

Cardiac resynchronization therapy (CRT) may exert its beneficial haemodynamic effect by improving ventricular synchrony and improving atrioventricular (AV) timing. The aim of this study was to establish the relative importance of the mechanisms through which CRT improves cardiac function and explore the potential for additional improvements with improved ventricular resynchronization.

Methods and Results

We performed simulations using the CircAdapt haemodynamic model and performed haemodynamic measurements while adjusting AV delay, at low and high heart rates, in 87 patients with CRT devices. We assessed QRS duration, presence of fusion, and haemodynamic response. The simulations suggest that intrinsic PR interval and the magnitude of reduction in ventricular activation determine the relative importance of the mechanisms of benefit. For example, if PR interval is 201 ms and LV activation time is reduced by 25 ms (typical for current CRT methods), then AV delay optimization is responsible for 69% of overall improvement. Reducing LV activation time by an additional 25 ms produced an additional 2.6 mmHg increase in blood pressure (30% of effect size observed with current CRT). In the clinical population, ventricular fusion significantly shortened QRS duration (Δ-27 ± 23 ms, P < 0.001) and improved systolic blood pressure (mean 2.5 mmHg increase). Ventricular fusion was present in 69% of patients, yet in 40% of patients with fusion, shortening AV delay (to a delay where fusion was not present) produced the optimal haemodynamic response.

Conclusions

Improving LV preloading by shortening AV delay is an important mechanism through which cardiac function is improved with CRT. There is substantial scope for further improvement if methods for delivering more efficient ventricular resynchronization can be developed.

Clinical Trial Registration

Our clinical data were obtained from a subpopulation of the British Randomised Controlled Trial of AV and VV Optimisation (BRAVO), which is a registered clinical trial with unique identifier: NCT01258829, https://clinicaltrials.gov

Distinct impacts of heart rate and right atrial-pacing on left atrial mechanical activation and optimal AV delay in CRT

BACKGROUND

Controversy exists regarding how atrial activation mode and heart rate affect optimal atrioventricular (AV) delay in cardiac resynchronization therapy. We studied these questions using high-reproducibility hemodynamic and echocardiographic measurements.

METHODS

Twenty patients were hemodynamically optimized using noninvasive beat-to-beat blood pressure at rest (62 ± 11 beats/min), during exercise (80 ± 6 beats/min), and at three atrially paced rates: 5, 25, and 45 beats/min above rest, denoted as Apaced,r+5 , Apaced,r+25 , and Apaced,r+45 , respectively. Left atrial myocardial motion and transmitral flow were timed echocardiographically.

RESULTS

During atrial sensing, raising heart rate shortened optimal AV delay by 25 ± 6 ms (P < 0.001). During atrial pacing, raising heart rate from Apaced,r+5 to Apaced,r+25 shortened it by 16 ± 6 ms; Apaced,r+45 shortened it 17 ± 6 ms further (P < 0.001). In comparison to atrial-sensed activation, atrial pacing lengthened optimal AV delay by 76 ± 6 ms (P < 0.0001) at rest, and at ∼20 beats/min faster, by 85 ± 7 ms (P < 0.0001), 9 ± 4 ms more (P  =  0.017). Mechanically, atrial pacing delayed left atrial contraction by 63 ± 5 ms at rest and by 73 ± 5 ms (i.e., by 10 ± 5 ms more, P < 0.05) at ∼20 beats/min faster. Raising atrial rate by exercise advanced left atrial contraction by 7 ± 2 ms (P  =  0.001). Raising it by atrial pacing did not (P  =  0.2).

CONCLUSIONS

Hemodynamic optimal AV delay shortens with elevation of heart rate. It lengthens on switching from atrial-sensed to atrial-paced at the same rate, and echocardiography shows this sensed-paced difference in optima results from a sensed-paced difference in atrial electromechanical delay. The reason for the widening of the sensed-paced difference in AV optimum may be physiological stimuli (e.g., adrenergic drive) advancing left atrial contraction during exercise but not with fast atrial pacing.

Multicenter Randomized Controlled Crossover Trial Comparing Hemodynamic Optimization Against Echocardiographic Optimization of AV and VV Delay of Cardiac Resynchronization Therapy: The BRAVO Trial

OBJECTIVES

BRAVO (British Randomized Controlled Trial of AV and VV Optimization) is a multicenter, randomized, crossover, noninferiority trial comparing echocardiographic optimization of atrioventricular (AV) and interventricular delay with a noninvasive blood pressure method.

BACKGROUND

Cardiac resynchronization therapy including AV delay optimization confers clinical benefit, but the optimization requires time and expertise to perform.

METHODS

This study randomized patients to echocardiographic optimization or hemodynamic optimization using multiple-replicate beat-by-beat noninvasive blood pressure at baseline; after 6 months, participants were crossed over to the other optimization arm of the trial. The primary outcome was exercise capacity, quantified as peak exercise oxygen uptake. Secondary outcome measures were echocardiographic left ventricular (LV) remodeling, quality-of-life scores, and N-terminal pro-B-type natriuretic peptide.

RESULTS

A total of 401 patients were enrolled, the median age was 69 years, 78% of patients were men, and the New York Heart Association functional class was II in 84% and III in 16%. The primary endpoint, peak oxygen uptake, met the criterion for noninferiority (p_{noninferiority} = 0.0001), with no significant difference between the hemodynamically optimized arm and echocardiographically optimized arm of the trial (mean difference 0.1 ml/kg/min). Secondary endpoints for noninferiority were also met for symptoms (mean difference in Minnesota score 1; p_{noninferiority} = 0.002) and hormonal changes (mean change in N-terminal pro-B-type natriuretic peptide -10 pg/ml; p_{noninferiority} = 0.002). There was no significant difference in LV size (mean change in LV systolic dimension 1 mm; p_{noninferiority} < 0.001; LV diastolic dimension 0 mm; p_{noninferiority} <0.001). In 30% of patients the AV delay identified as optimal was more than 20 ms from the nominal setting of 120 ms.

CONCLUSIONS

Optimization of cardiac resynchronization therapy devices by using noninvasive blood pressure is noninferior to echocardiographic optimization. Therefore, noninvasive hemodynamic optimization is an acceptable alternative that has the potential to be automated and thus more easily implemented. (British Randomized Controlled Trial of AV and VV Optimization [BRAVO]; NCT01258829).

Cyclic Nonrespiratory Pulse Pressure Oscillations Caused by Atrioventricular Dissociation

Dynamic preload assessment tests, especially pulse pressure variation (PPV) and stroke volume variation (SVV), are increasingly acknowledged in mechanically ventilated patients as being predictors of fluid responsiveness. However, the limitations of this method are often neglected or overlooked. One of the prerequisites for PPV and SVV evaluation, in addition to intermittent positive pressure ventilation, is a “regular heart rhythm,” which may be an ambiguous term. We present a case where, despite a regular (paced) rhythm, atrioventricular dissociation was present and resulted in marked PPV elevation, which subsequently disappeared once sinus rhythm returned. Our case indicates that PPV and SVV should be interpreted with caution when atrioventricular dissociation is present.

His Bundle Pacing: A New Frontier in the Treatment of Heart Failure

Biventricular pacing has revolutionised the treatment of heart failure in patients with sinus rhythm and left bundle branch block; however, left ventricular-lead placement is not always technically possible. Furthermore, biventricular pacing does not fully normalise ventricular activation and, therefore, the ventricular resynchronisation is imperfect. Right ventricular pacing for bradycardia may cause or worsen heart failure in some patients by causing dyssynchronous ventricular activation. His bundle pacing activates the ventricles via the native His-Purkinje system, resulting in true physiological pacing, and, therefore, is a promising alternate site for pacing in bradycardia and traditional CRT indications in cases where it can overcome left bundle branch block. Furthermore, it may open up new indications for pacing therapy in heart failure, such as targeting patients with PR prolongation, but a narrow QRS duration. In this article we explore the physiology, technology and potential roles of His bundle pacing in the prevention and treatment of heart failure.

Effects of pacing modality on noninvasive assessment of heart rate dependency of indices of large artery function

Studies investigating the relationship between heart rate (HR) and arterial stiffness or wave reflections have commonly induced HR changes through in situ cardiac pacing. Although pacing produces consistent HR changes, hemodynamics can be different with different pacing modalities. Whether the differences affect the HR relationship with arterial stiffness or wave reflections is unknown. In the present study, 48 subjects [mean age, 78 ± 10 (SD), 9 women] with in situ cardiac pacemakers were paced at 60, 70, 80, 90, and 100 beats per min under atrial, atrioventricular, or ventricular pacing. At each paced HR, brachial cuff-based pulse wave analysis was used to determine central hemodynamic parameters, including ejection duration (ED) and augmentation index (AIx). Wave separation analysis was used to determine wave reflection magnitude (RM) and reflection index (RI). Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). Pacing modality was found to have significant effects on the HR relationship with ED (P = 0.01), central aortic pulse pressure (P = 0.01), augmentation pressure (P < 0.0001), and magnitudes of both forward and reflected waves (P = 0.05 and P = 0.003, respectively), but not cfPWV (P = 0.57) or AIx (P = 0.38). However, at a fixed HR, significant differences in pulse pressure amplification (P < 0.001), AIx (P < 0.0001), RM (P = 0.03), and RI (P = 0.03) were observed with different pacing modalities. These results demonstrate that although the HR relationships with arterial stiffness and systolic loading as measured by cfPWV and AIx were unaffected by pacing modality, it should still be taken into account for studies in which mixed pacing modalities are present, in particular, for wave reflection studies.

Is maternal smoking during pregnancy associated with an increased risk of congenital heart defects among offspring? A systematic review and meta-analysis of observational studies

OBJECTIVE

To investigate the association between maternal smoking during pregnancy and risk of congenital heart defects (CHDs) among offspring.

METHODS

PubMed, EMBASE, and Web of Science were searched for eligible studies. The outcomes of interest included risk of any CHD and nine subtypes. We summarized study characteristics and used a random-effects model in meta-analysis, and a two-stage dose-response model was utilized to assess the association between smoking consumption and risk. Statistical heterogeneity was assessed by a chi-squared test of the Cochrane Q statistic and I-squared value. Publication bias was assessed by funnel plots and Egger's test, and trim and fill method was utilized when publication bias existed.

RESULTS

Forty-three observational epidemiologic studies were included. The pooled risk ratio (RR) of any CHD was 1.11 (95% CI: 1.04, 1.18), but it exhibited substantial statistical heterogeneity (p < 0.001, I²=69.0%). In sensitivity analysis, we observed significant associations for atrial septal defect (ASD) and marginally significant associations for septal defects (SPD). The two-stage dose-response analysis showed evidence to support that higher levels of tobacco smoke was associated with an increased risk of septal defects, particularly for ASD and VSD (ventricular septal defect).

CONCLUSION

Our study presents evidence to support the cardiovascular teratogenic effect of maternal smoking during pregnancy, and their offspring may suffer from approximately a 10% relative increase in the risk of CHDs on average.

In Heart Failure Patients with Left Bundle Branch Block Single Lead MultiSpot Left Ventricular Pacing Does Not Improve Acute Hemodynamic Response To Conventional Biventricular Pacing. A Multicenter Prospective, Interventional, Non-Randomized Study

INTRODUCTION

Recent efforts to increase CRT response by multiSPOT pacing (MSP) from multiple bipols on the same left ventricular lead are still inconclusive.

AIM

The Left Ventricular (LV) MultiSPOTpacing for CRT (iSPOT) study compared the acute hemodynamic response of MSP pacing by using 3 electrodes on a quadripolar lead compared with conventional biventricular pacing (BiV).

METHODS

Patients with left bundle branch block (LBBB) underwent an acute hemodynamic study to determine the %change in LV+dP/dtmax from baseline atrial pacing compared to the following configurations: BiV pacing with the LV lead in a one of lateral veins, while pacing from the distal, mid, or proximal electrode and all 3 electrodes together (i.e. MSP). All measurements were repeated 4 times at 5 different atrioventricular delays. We also measured QRS-width and individual Q-LV durations.

RESULTS

Protocol was completed in 24 patients, all with LBBB (QRS width 171±20 ms) and 58% ischemic aetiology. The percentage change in LV+dP/dtmax for MSP pacing was 31.0±3.3% (Mean±SE), which was not significantly superior to any BiV pacing configuration: 28.9±3.2% (LV-distal), 28.3±2.7% (LV-mid), and 29.5±3.0% (LV-prox), respectively. Correlation between LV+dP/dtmax and either QRS-width or Q-LV ratio was poor.

CONCLUSIONS

In patients with LBBB MultiSPOT LV pacing demonstrated comparable improvement in contractility to best conventional BiV pacing. Optimization of atrioventricular delay is important for the best performance for both BiV and MultiSPOT pacing configurations.

TRIAL REGISTRATION

ClinicalTrials.gov NTC01883141.

Acute contractile recovery extent during biventricular pacing is not associated with follow-up in patients undergoing resynchronization

Background

It has been reported that contractility, as assessed using dobutamine infusion, is independently associated with reverse remodeling after CRT. Controversy, however, exists about the capacity of this approach to predict a long-term clinical response. This study's purpose was to assess whether long-term CRT clinical effects can be predicted according to acute inotropic response induced by biventricular stimulation (CRT on), as compared with AAI–VVI right stimulation pacing mode (CRT off), quantified at the time of implantation.

Methods

In 98 patients (ejection fraction 29 ± 10%), acute changes in left ventricular (LV) elastance (Ees), arterial elastance (Ea), and Ees/Ea, as assessed from slope changes of the force–frequency relation obtained when the heart rate increased, and also assessed while measuring triplane LV volumes and continuous noninvasive blood pressure, were related to death or rehospitalization during a 3-year follow-up. Other covariances tested were age, gender, disease etiology, QRS duration, amount of mitral regurgitation, LV diastolic volume, ejection fraction, and the degree of asynchrony and longitudinal strain at baseline.

Results

There was a marked increment in the Ees slope with CRT (interaction P = 0.004), no Ea change, and modest Ees/Ea increase (interaction P < 0.05). In Cox analysis, however, neither slope changes nor baseline values of Ees, Ea, and Ees/Ea were associated with long-term follow-up. Only ventricular diastolic volume (direct relation P = 0.002) and QRS duration (inverse relation P = 0.009) predicted death/rehospitalization.

Conclusions

Acute contractile recovery in CRT patients is not associated with 3 years prognosis. Instead, death or rehospitalization can be predicted from QRS duration and LV diastolic volume at baseline.

Prolongation of atrio-ventricular node conduction in a rabbit model of ischaemic cardiomyopathy: Role of fibrosis and connexin remodelling

Conduction abnormalities are frequently associated with cardiac disease, though the mechanisms underlying the commonly associated increases in PQ interval are not known. This study uses a chronic left ventricular (LV) apex myocardial infarction (MI) model in the rabbit to create significant left ventricular dysfunction (LVD) 8 weeks post-MI. In vivo studies established that the PQ interval increases by approximately 7 ms (10%) with no significant change in average heart rate. Optical mapping of isolated Langendorff perfused rabbit hearts recapitulated this result: time to earliest activation of the LV was increased by 14 ms (16%) in the LVD group. Intra-atrial and LV transmural conduction times were not altered in the LVD group. Isolated AVN preparations from the LVD group demonstrated a significantly longer conduction time (by approximately 20 ms) between atrial and His electrograms than sham controls across a range of pacing cycle lengths. This difference was accompanied by increased effective refractory period and Wenckebach cycle length, suggesting significantly altered AVN electrophysiology post-MI. The AVN origin of abnormality was further highlighted by optical mapping of the isolated AVN. Immunohistochemistry of AVN preparations revealed increased fibrosis and gap junction protein (connexin43 and 40) remodelling in the AVN of LVD animals compared to sham. A significant increase in myocyte–non-myocyte connexin co-localization was also observed after LVD. These changes may increase the electrotonic load experienced by AVN muscle cells and contribute to slowed conduction velocity within the AVN.

•

Chronic myocardial infarction (MI) causes changes in atrio-ventricular node (AVN) function.

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Isolated hearts post-MI show delays in ventricular activation due to slowed conduction via the AVN.

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Isolated AVN preparations demonstrated AVN electrical remodelling post-MI.

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Electrical remodelling is associated with fibrosis and altered expression of connexins in the AVN.

•

AVN dysfunction post-MI is caused by localized functional and structural remodelling.

The Role of Atrioventricular and Interventricular Optimization for Cardiac Resynchronization Therapy

Many patients with left ventricular systolic dysfunction may benefit from cardiac resynchronization therapy; however, approximately 30% of patients do not experience significant clinical improvement with this treatment. AV and VV delay optimization techniques have included echocardiography, device-based algorithms, and several other novel noninvasive techniques. Using these techniques to optimize device settings has been shown to improve hemodynamic function acutely; however, the long-term clinical benefit is limited. In most cases, an empiric AV delay with simultaneous biventricular or left ventricular pacing is adequate. The value of optimization of these intervals in "nonresponders" still requires further investigation.

Cardiac resynchronization therapy update: evolving indications, expanding benefit?

Cardiac resynchronisation therapy (CRT) is an effective intervention for appropriately selected patients with heart failure, but exactly how it works is uncertain. Recent data suggest that much, or perhaps most, of the benefits of CRT are not delivered by re-coordinating left ventricular dyssynchrony. Atrio-ventricular resynchronization, reduction in mitral regurgitation and prevention of bradycardia are other potential mechanisms of benefit that will vary from one patient to the next and over time. Because there is no single therapeutic target, it is unlikely that any single measure will accurately predict benefit. The only clinical characteristic that appears to be a useful predictor of the benefits of CRT is a QRS duration of >140 ms. Many new approaches are being developed to try to improve the effectiveness of and extend the indications for CRT. These include smart pacing algorithms, better pacing-site targeting, new sensors, multipoint pacing, remote device monitoring and leadless endocardial pacing. Whether CRT is effective in patients with atrial fibrillation or whether adding a defibrillator function to CRT improves prognosis awaits further evidence.

Feasibility of a novel atrioventricular delay optimization method using transmitral and pulmonary venous flow in patients with sequential ventricular pacing or cardiac resynchronization therapy

Background

Although several echo-Doppler methods were proposed to optimize atrioventricular (AV) delay in patients with sequential ventricular pacing, “echo-guided” AV optimization has not been widely adopted clinically. A combination of trasmitral flow (TMF) and pulmonary venous flow (PVF) measurements may be beneficial to further optimize AV delay to achieve better cardiac function. The aim of this study was to assess the feasibility and usefulness of AV delay optimization by combined use of TMF and PVF.

Methods

A total of 32 patients after sequential ventricular pacemaker implantation were enrolled and studied. The optimal AV delay was defined as the timing to minimize the duration between PVF reversal (a) wave and the duration of the “A” wave of TMF. Stroke volume was measured at the “optimized” AV delay (AVD_OPT) and was compared with that obtained at shorter (AVD_OPT − 50 ms) and longer (AVD_OPT + 50 ms) AV delays.

Results

AV optimization was feasible in 27 of 32 patients (87 %). Stroke volume at AVD_OPT was significantly higher than that at shorter or longer AV delay (63 ± 18 ml vs. 57 ± 15 ml vs. 56 ± 16 ml, P = 0.001).

Conclusions

AV delay optimization using TMF and PV flow was feasible. Usefulness of this method requires further investigation with a larger study population.

Evidence that conflict regarding size of haemodynamic response to interventricular delay optimization of cardiac resynchronization therapy may arise from differences in how atrioventricular delay is kept constant

Aims

Whether adjusting interventricular (VV) delay changes haemodynamic efficacy of cardiac resynchronization therapy (CRT) is controversial, with conflicting results. This study addresses whether the convention for keeping atrioventricular (AV) delay constant during VV optimization might explain these conflicts.

Method and results

Twenty-two patients in sinus rhythm with existing CRT underwent VV optimization using non-invasive systolic blood pressure. Interventricular optimization was performed with four methods for keeping the AV delay constant: (i) atrium and left ventricle delay kept constant, (ii) atrium and right ventricle delay kept constant, (iii) time to the first-activated ventricle kept constant, and (iv) time to the second-activated ventricle kept constant. In 11 patients this was performed with AV delay of 120 ms, and in 11 at AV optimum. At AV 120 ms, time to the first ventricular lead (left or right) was the overwhelming determinant of haemodynamics (13.75 mmHg at ±80 ms, P < 0.001) with no significant effect of time to second lead (0.47 mmHg, P = 0.50), P < 0.001 for difference. At AV optimum, time to first ventricular lead again had a larger effect (5.03 mmHg, P < 0.001) than time to second (2.92 mmHg, P = 0.001), P = 0.02 for difference.

Conclusion

Time to first ventricular activation is the overwhelming determinant of circulatory function, regardless of whether this is the left or right ventricular lead. If this is kept constant, the effect of changing time to the second ventricle is small or nil, and is not beneficial. In practice, it may be advisable to leave VV delay at zero. Specifying how AV delay is kept fixed might make future VV delay research more enlightening.

Strategies to improve cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.

British randomised controlled trial of AV and VV optimization ("BRAVO") study: rationale, design, and endpoints

Background

Echocardiographic optimization of pacemaker settings is the current standard of care for patients treated with cardiac resynchronization therapy. However, the process requires considerable time of expert staff. The BRAVO study is a non-inferiority trial comparing echocardiographic optimization of atrioventricular (AV) and interventricular (VV) delay with an alternative method using non-invasive blood pressure monitoring that can be automated to consume less staff resources.

Methods/Design

BRAVO is a multi-centre, randomized, cross-over, non-inferiority trial of 400 patients with a previously implanted cardiac resynchronization device. Patients are randomly allocated to six months in each arm. In the echocardiographic arm, AV delay is optimized using the iterative method and VV delay by maximizing LVOT VTI. In the haemodynamic arm AV and VV delay are optimized using non-invasive blood pressure measured using finger photoplethysmography. At the end of each six month arm, patients undergo the primary outcome measure of objective exercise capacity, quantified as peak oxygen uptake (VO₂) on a cardiopulmonary exercise test. Secondary outcome measures are echocardiographic measurement of left ventricular remodelling, quality of life score and N-terminal pro B-type Natriuretic Peptide (NT-pro BNP). The study is scheduled to complete recruitment in December 2013 and to complete follow up in December 2014.

Discussion

If exercise capacity is non-inferior with haemodynamic optimization compared with echocardiographic optimization, it would be proof of concept that haemodynamic optimization is an acceptable alternative which has the potential to be more easily implemented.

Trial registration

Clinicaltrials.gov NCT01258829

Optimal Strategies on Avoiding CRT Nonresponse

OPINION STATEMENT

The high rate of nonresponse to cardiac resynchronization therapy (CRT) has remained nearly unchanged since the treatment was introduced. We believe that this is directly related to the many persisting unknowns regarding the mechanical function of asynchronous hearts and the use of electrical stimulation to counteract the deleterious effects of that asynchrony. As a consequence, the key questions pertaining to the pre-implant, intra-implant, and postimplant phases remain unanswered or only partially answered. QRS duration is an imperfect selection criterion, as it does not discriminate the activation pattern. The inclusion of QRS morphology in the international professional practice guidelines is an important first step toward increasing the yield of this therapy. The invasive and the noninvasive electrical mapping techniques seem highly promising and need to be tested in large trials. The site of stimulation is a key element of the response to CRT; additional research must be pursued in this field.

Effects of AV delay and VV delay on left atrial pressure and waveform in ambulant heart failure patients: insights into CRT optimization

BACKGROUND

We hypothesized that left atrial pressure (LAP) obtained by a permanent implantable sensor is sensitive to changes in cardiac resynchronization therapy (CRT) settings and could guide CRT optimization to improve the response rate. We investigated the effect of CRT optimization on LAP and its waveform parameters in ambulant heart failure (HF) patients.

METHODS

CRT optimization was performed in eight ambulant HF patients, using echocardiography as reference. LAP waveform was acquired at each of eight atrioventricular (AV) intervals and five inter-ventricular (VV) intervals. Selected waveform parameters were also evaluated for their sensitivity to CRT changes and agreement with echocardiography-guided optimal settings.

RESULTS

Optimal AV and VV intervals varied considerably between patients. All patients exhibited significant changes in waveform morphology with AV optimization. Optimal AV delay determined from echocardiography ranged between 140 ms and 225 ms. Mean LAP tended to be lower at optimal setting 14 ± 3 mmHg compared to shorter (<100 ms) or longer (>160 ms) AV settings (P = 0.16). There were clear trends to smaller peak a-wave (P = 0.11) and gentler positive a-slope (P = 0.15) and positive v-slope (P = 0.09) with longer AV delays. Mean LAP and negative v-wave slope correlated well with echo-guided optimal setting, r = 0.91 (P = 0.001) and 0.79 (P = 0.03), respectively. No significant effects on LAP or waveform were seen during VV optimization.

CONCLUSIONS

LAP and its waveform changes considerably with AV optimization. There is good agreement between echo-guided optimal setting and LAP. LAP could provide an objective guide to CRT optimization. (Clinical Trial Registry information: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00632372).

Cardiac resynchronisation therapy optimisation strategies: systematic classification, detailed analysis, minimum standards and a roadmap for development and testing

In this article an international group of CRT specialists presents a comprehensive classification system for present and future schemes for optimising CRT. This system is neutral to the measurement technology used, but focuses on little-discussed quantitative physiological requirements. We then present a rational roadmap for reliable cost-effective development and evaluation of schemes. A widely recommended approach for AV optimisation is to visually select the ideal pattern of transmitral Doppler flow. Alternatively, one could measure a variable (such as Doppler velocity time integral) and "pick the highest". More complex would be to make measurements across a range of settings and "fit a curve". In this report we provide clinicians with a critical approach to address any recommendations presented to them, as they may be many, indistinct and conflicting. We present a neutral scientific analysis of each scheme, and equip the reader with simple tools for critical evaluation. Optimisation protocols should deliver: (a) singularity, with only one region of optimality rather than several; (b) blinded test-retest reproducibility; (c) plausibility; (d) concordance between independent methods; and (e) transparency, with all steps open to scrutiny. This simple information is still not available for many optimisation schemes. Clinicians developing the habit of asking about each property in turn will find it easier to win now down the broad range of protocols currently promoted. Expectation of a sophisticated enquiry from the clinical community will encourage optimisation protocol-designers to focus on testing early (and cheaply) the basic properties that are vital for any chance of long term efficacy.

Effects of moderate-intensity aerobic cycling and swim exercise on post-exertional blood pressure in healthy young untrained and triathlon-trained men and women

Aerobic exercises such as running, walking and cycling are known to elicit a PEH (post-exercise hypotensive) response in both trained and UT (untrained) subjects. However, it is not known whether swim exercise produces a similar effect in normotensive individuals. The complex acute physiological responses to water immersion suggest swimming may affect BP (blood pressure) differently than other forms of aerobic exercises. We tested the hypothesis that an acute bout of swimming would fail to elicit a PEH BP response compared with an equivalent bout of stationary cycling, regardless of training state. We studied 11 UT and ten triathlon-trained young healthy normotensive [SBP/DBP (systolic BP/diastolic BP) <120/80 mmHg)] men and women (age 23±1 years) who underwent 30 min of intensity-matched cycling and swimming sessions to assess changes in BP during a 75-min seated recovery. CO (cardiac output), SV (stroke volume), TPR (total peripheral resistance), HR (heart rate), HRV (HR variability) and core and skin temperature were also assessed. In UT subjects, PEH was similar between cycling (-3.1±1 mmHg) and swimming (-5.8±1 mmHg), with the greater magnitude of PEH following swimming, reflecting a significant fall in SV between modalities (P<0.05). Trained individuals did not exhibit a PEH response following swimming (0.3±1 mmHg), yet had a significant fall in SBP at 50 min post-cycling exercise (-3.7±1 mmHg) (P<0.05). The absence of PEH after swimming in the trained group may reflect a higher cardiac sympathetic outflow [as indicated by the LF (low-frequency) spectral component of HRV) (25 and 50 min) (P<0.05)] and a slower return of vagal tone, consistent with a significant increase in HR between modalities at all time points (P<0.05). These results suggest that training may limit the potential for an effective post-exertional hypotensive response to aerobic swimming.

Cardiac resynchronization therapy and AV optimization increase myocardial oxygen consumption, but increase cardiac function more than proportionally

BACKGROUND

The mechanoenergetic effects of atrioventricular delay optimization during biventricular pacing ("cardiac resynchronization therapy", CRT) are unknown.

METHODS

Eleven patients with heart failure and left bundle branch block (LBBB) underwent invasive measurements of left ventricular (LV) developed pressure, aortic flow velocity-time-integral (VTI) and myocardial oxygen consumption (MVO2) at 4 pacing states: biventricular pacing (with VV 0 ms) at AVD 40 ms (AV-40), AVD 120 ms (AV-120, a common nominal AV delay), at their pre-identified individualised haemodynamic optimum (AV-Opt); and intrinsic conduction (LBBB).

RESULTS

AV-120, relative to LBBB, increased LV developed pressure by a mean of 11(SEM 2)%, p=0.001, and aortic VTI by 11(SEM 3)%, p=0.002, but also increased MVO2 by 11(SEM 5)%, p=0.04. AV-Opt further increased LV developed pressure by a mean of 2(SEM 1)%, p=0.035 and aortic VTI by 4(SEM 1)%, p=0.017. MVO2 trended further up by 7(SEM 5)%, p=0.22. Mechanoenergetics at AV-40 were no different from LBBB. The 4 states lay on a straight line for Δexternal work (ΔLV developed pressure × Δaortic VTI) against ΔMVO2, with slope 1.80, significantly >1 (p=0.02).

CONCLUSIONS

Biventricular pacing and atrioventricular delay optimization increased external cardiac work done but also myocardial oxygen consumption. Nevertheless, the increase in cardiac work was ~80% greater than the increase in oxygen consumption, signifying an improvement in cardiac mechanoenergetics. Finally, the incremental effect of optimization on external work was approximately one-third beyond that of nominal AV pacing, along the same favourable efficiency trajectory, suggesting that AV delay dominates the biventricular pacing effect - which may therefore not be mainly "resynchronization".

Cardiac resynchronization therapy mechanisms in atrial fibrillation

This article examines how to assess the reliability of potential techniques for performing optimization of biventricular pacemakers in patients with atrial fibrillation. It explores the magnitude of improvement that is likely to be obtained with the optimization of biventricular pacing in this clinical setting and discusses the lessons that can be learned with regard to the mechanisms of action of biventricular pacing in the general heart failure population.

Optimisation of cardiac resynchronization therapy in clinical practice during exercise

Aims

Although cardiac resynchronisation therapy (CRT) is an established treatment to improve cardiac function, a significant amount of patients do not experience noticeable improvement in their cardiac function. Optimal timing of the delay between atrial and ventricular pacing pulses (AV delay) is of major importance for effective CRT treatment and this optimum may differ between resting and exercise conditions. In this study the feasibility of haemodynamic measurements by the non-invasive finger plethysmographic method (Nexfin) was used to optimise the AV delay during exercise.

Methods and results

Thirty-one patients implanted with a CRT device in the last 4 years participated in the study. During rest and in exercise, stroke volume (SV) was measured using the Nexfin device for several AV delays. The optimal AV delay at rest and in exercise was determined using the least squares estimates (LSE) method. Optimisation created a clinically significant improvement in SV of 10 %. The relation between HR and the optimal AV delay was patient dependent.

Conclusion

A potential increase in SV of 10 % can be achieved using Nexfin for optimisation of AV delay during exercise. A considerable number of patients showed benefit with lengthening of the AV delay during exercise.