Mechanism of hemodynamic improvement by dual-chamber pacing for severe left ventricular dysfunction: an acute Doppler and catheterization hemodynamic study

Outcomes of mitral TEER in non-responders to cardiac resynchronization therapy: A systematic review and meta-analysis

BACKGROUND

Secondary mitral regurgitation (MR) worsens in 10-15 % of heart failure (HF) patients receiving cardiac resynchronization therapy (CRT). Transcatheter edge-to-edge repair (TEER) with Mitra-Clip (Abbot Vascular, Santa Clara, CA, USA) therapy is associated with improved survival and decreased rates of hospitalization for HF in selected patients with secondary MR. Data on TEER outcomes in CRT-non-responders are limited. The purpose of this meta-analysis was to evaluate outcomes of mitral TEER with Mitra-Clip in CRT-non-responders.

METHODS

Cochrane, Scopus, MEDLINE, and EMBASE were searched for studies discussing outcomes of Mitra-Clip in CRT non-responders. Two reviewers were independently involved in screening studies and extracting relevant data. Individual study incidence rate estimates underwent logit transformation to calculate the weighted summary proportion under the random effect model.

RESULTS

A total of eight reports met the inclusion criteria (439 patients). Mitra-Clip improved MR grade to ≤2+ in 83.8 % and 86.8 % of CRT non-responders at six months and one year, respectively. Symptomatic improvement (New York Heart Association class ≤II) was also found in 71 % and 78.1 % of CRT non-responders at six months and one year, respectively. The pooled overall incidence estimates of mortality at 30 days, 6 months, 1 year, and 2 years were 3.6 %, 9.2 %, 17.8 %, and 25.9 %, respectively.

CONCLUSION

TEER with Mitra-Clip in patients with significant secondary MR who do not respond to CRT was associated with MR improvement, alleviation of symptoms, and mortality rates similar to those in the COAPT trial.

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.

Value of frontal QRS axis for risk stratification of individuals with prolonged PR interval

BACKGROUND

There is ongoing controversy regarding the prognostic value of PR prolongation among individuals free of cardiovascular diseases. It is necessary to risk-stratify this population according to other electrocardiographic parameters.

METHODS

This study is based on the Third National Health and Nutrition Examination Survey. Cox proportional hazard models were constructed and Kaplan-Meier method was used.

RESULTS

A total of 6188 participants (58.1 ± 13.1 years; 55% women) were included. The median frontal QRS axis of the entire study population was 37° (IQR: 11-60°). PR prolongation was present in 7.6% of the participants, of whom 61.2% had QRS axis ≤37°. In a multivariable-adjusted model, mortality risk was highest in the group with concomitant prolonged PR interval and QRS axis ≤37° (hazard ratio [HR]: 1.20; 95% confidence interval [CI]: 1.04-1.39). In models with similar adjustment where population were reclassified depending on PR prolongation and QRS axis, prolonged PR interval and QRS axis ≤37° was still associated with increased risk of mortality (HR: 1.18; 95% CI: 1.03-1.36) compared with normal PR interval.

CONCLUSIONS

QRS axis is an important factor for risk stratification in population with PR prolongation. The extent to which this population with PR prolongation and QRS axis ≤37° is at higher risk of death compared with the population without PR prolongation.

Effects of haemodynamically atrio-ventricular optimized His bundle pacing on heart failure symptoms and exercise capacity: the His Optimized Pacing Evaluated for Heart Failure (HOPE-HF) randomized, double-blind, cross-over trial

AIMS

Excessive prolongation of PR interval impairs coupling of atrio-ventricular (AV) contraction, which reduces left ventricular pre-load and stroke volume, and worsens symptoms. His bundle pacing allows AV delay shortening while maintaining normal ventricular activation. HOPE-HF evaluated whether AV optimized His pacing is preferable to no-pacing, in a double-blind cross-over fashion, in patients with heart failure, left ventricular ejection fraction (LVEF) ≤40%, PR interval ≥200 ms and either QRS ≤140 ms or right bundle branch block.

METHODS AND RESULTS

Patients had atrial and His bundle leads implanted (and an implantable cardioverter-defibrillator lead if clinically indicated) and were randomized to 6 months of pacing and 6 months of no-pacing utilizing a cross-over design. The primary outcome was peak oxygen uptake during symptom-limited exercise. Quality of life, LVEF and patients' holistic symptomatic preference between arms were secondary outcomes. Overall, 167 patients were randomized: 90% men, 69 ± 10 years, QRS duration 124 ± 26 ms, PR interval 249 ± 59 ms, LVEF 33 ± 9%. Neither peak oxygen uptake (+0.25 ml/kg/min, 95% confidence interval [CI] -0.23 to +0.73, p = 0.3) nor LVEF (+0.5%, 95% CI -0.7 to 1.6, p = 0.4) changed with pacing but Minnesota Living with Heart Failure quality of life improved significantly (-3.7, 95% CI -7.1 to -0.3, p = 0.03). Seventy-six percent of patients preferred His bundle pacing-on and 24% pacing-off (p < 0.0001).

CONCLUSION

His bundle pacing did not increase peak oxygen uptake but, under double-blind conditions, significantly improved quality of life and was symptomatically preferred by the clear majority of patients. Ventricular pacing delivered via the His bundle did not adversely impact ventricular function during the 6 months.

Pacing therapy for atrioventricular dromotropathy: a combined computational-experimental-clinical study

AIMS

Investigate haemodynamic effects, and their mechanisms, of restoring atrioventricular (AV)-coupling using pacemaker therapy in normal and failing hearts in a combined computational-experimental-clinical study.

METHODS AND RESULTS

Computer simulations were performed in the CircAdapt model of the normal and failing human heart and circulation. Experiments were performed in a porcine model of AV dromotropathy. In a proof-of-principle clinical study, left ventricular (LV) pressure and volume were measured in 22 heart failure (HF) patients (LV ejection fraction <35%) with prolonged PR interval (>230 ms) and narrow or non-left bundle branch block QRS complex. Computer simulations and animal studies in normal hearts showed that restoring of AV-coupling with unchanged ventricular activation sequence significantly increased LV filling, mean arterial pressure, and cardiac output by 10-15%. In computer simulations of failing hearts and in HF patients, reducing PR interval by biventricular (BiV) pacing (patients: from 300 ± 61 to 137 ± 30 ms) resulted in significant increases in LV stroke volume and stroke work (patients: 34 ± 40% and 26 ± 31%, respectively). However, worsening of ventricular dyssynchrony by using right ventricular (RV) pacing abrogated the benefit of restoring AV-coupling. In model simulations, animals and patients, the increase of LV filling and associated improvement of LV pump function coincided with both larger mitral inflow (E- and A-wave area) and reduction of diastolic mitral regurgitation.

CONCLUSION

Restoration of AV-coupling by BiV pacing in normal and failing hearts with prolonged AV conduction leads to considerable haemodynamic improvement. These results indicate that BiV or physiological pacing, but not RV pacing, may improve cardiac function in patients with HF and prolonged PR interval.

Potential of remote monitoring to prevent sensing and detection failures in implantable cardioverter defibrillators

BACKGROUND

Sensing malfunction and misinterpretation of intracardiac electrograms (IEGMs) in patients with implantable cardioverter defibrillators (ICDs) may lead to inadequate device activity such as inappropriate shock delivery or unnecessary mode-switching. Remote monitoring has the potential for early detection of sensing malfunction or misclassification and may thus prevent adverse device activity. Therefore, the authors analyzed the amount, nature, and distribution of misclassification in current ICD and cardiac resynchronization therapy defibrillator technology using the device transmissions of the IN-TIME study population.

METHODS

All transmitted tachyarrhythmic episodes in the 664 IN-TIME patients, comprising 2214 device-classified atrial fibrillation (DC-AF) episodes lasting ≥ 30 s and 1330 device-classified ventricular tachycardia or fibrillation (DC-VT/VF) episodes, were manually analyzed by two experienced cardiologists.

RESULTS

After evaluation of all DC-VT/VF episodes, a total of 300 VT/VF events (23.1%) were false-positive, with supraventricular tachycardia being the most frequent cause (51.7%), followed by atrial fibrillation (21.3%) and T‑wave oversensing (21.0%). A total of 15 patients with false-positive DC-VT/VF received inappropriate shocks. According to the inclusion criteria, 616 IEGMs with DC-AF were assessed. A total of 19.7% were false-positive AF episodes and R‑wave oversensing was the most common reason (55.9%).

CONCLUSIONS

Remote monitoring offers the opportunity of early detection of signal misclassification and thus early prevention of adverse device reaction, such as inappropriate shock delivery or mode-switching with intermittent loss of atrioventricular synchrony, by correcting the underlying causes.

Heart Failure due to High Degree Atrio-Ventricular Block: How Frequent is it and what is the cause?

BACKGROUND

The causes of heart failure (HF) during high-grade atrio-ventricular block (AVB) are poorly understood. This study assessed the mechanisms of HF in patients with AVB.

METHODS

We studied patients presenting (over the period 2012-2016) with high-grade AVB not related to acute myocardial infarction (MI). Patients with preexisting significant valvular heart disease were excluded. All patients underwent comprehensive echocardiographic evaluation during AVB, prior to pacemaker implantation. The diagnosis of HF was based on the Framingham criteria.

RESULTS

122 patients were included in the study, 50% male, average age 76+/-13 years. Twenty-eight (23%) patients with AVB presented with HF. Univariate correlates associated with HF were decrease in cardiac output (CO) [0.67 (95% confidence interval 0.49-0.9) per liter/min, p=0.007], measures of impaired left ventricular (LV) compliance and increase in diastolic mitral regurgitation (MR) volume [1.04 (1.01- 1.07), per cc, p=0.0016]. Ventricular rate during AVB and left-ventricular ejection fraction (LVEF) were not significantly associated with the presence of HF. By multivariate nominal logistic analysis, the best model associated with HF included diastolic MR volume [OR 1.03 (1.00-1.07), p=0.03], A-wave deceleration time [OR 0.96 (0.94-0.98), p=0.001], and CO [OR 0.72 (0.48-1.00), p=0.05], (X²= 30.6; AUC 0.84; p<0.0001 for the entire model).

CONCLUSIONS

In the setting of high-degree AVB, clinical HF occurrence correlates with impaired LV compliance and diastolic MR volume, but not with heart rate or LVEF. The cardiac performance of patients with poor LV compliance and high-volume diastolic MR may show maladjustment to slow heart rates, manifesting as low CO and HF.

Within-patient comparison of His-bundle pacing, right ventricular pacing, and right ventricular pacing avoidance algorithms in patients with PR prolongation: Acute hemodynamic study

AIMS

A prolonged PR interval may adversely affect ventricular filling and, therefore, cardiac function. AV delay can be corrected using right ventricular pacing (RVP), but this induces ventricular dyssynchrony, itself harmful. Therefore, in intermittent heart block, pacing avoidance algorithms are often implemented. We tested His-bundle pacing (HBP) as an alternative.

METHODS

Outpatients with a long PR interval (>200 ms) and intermittent need for ventricular pacing were recruited. We measured within-patient differences in high-precision hemodynamics between AV-optimized RVP and HBP, as well as a pacing avoidance algorithm (Managed Ventricular Pacing [MVP]).

RESULTS

We recruited 18 patients. Mean left ventricular ejection fraction was 44.3 ± 9%. Mean intrinsic PR interval was 266 ± 42 ms and QRS duration was 123 ± 29 ms. RVP lengthened QRS duration (+54 ms, 95% CI 42-67 ms, p < .0001) while HBP delivered a shorter QRS duration than RVP (-56 ms, 95% CI -67 to -46 ms, p < .0001). HBP did not increase QRS duration (-2 ms, 95% CI -8 to 13 ms, p = .6). HBP improved acute systolic blood pressure by mean of 5.0 mmHg (95% CI 2.8-7.1 mmHg, p < .0001) compared to RVP and by 3.5 mmHg (95% CI 1.9-5.0 mmHg, p = .0002) compared to the pacing avoidance algorithm. There was no significant difference in hemodynamics between RVP and ventricular pacing avoidance (p = .055).

CONCLUSIONS

HBP provides better acute cardiac function than pacing avoidance algorithms and RVP, in patients with prolonged PR intervals. HBP allows normalization of prolonged AV delays (unlike pacing avoidance) and does not cause ventricular dyssynchrony (unlike RVP). Clinical trials may be justified to assess whether these acute improvements translate into longer term clinical benefits in patients with bradycardia indications for pacing.

Comparison of left ventricular and biventricular pacing: Rationale and clinical implications

Cardiac resynchronization therapy constitutes a cornerstone in advanced heart failure treatment, when there is evidence of dyssynchrony, especially by electrocardiography. However, it is plagued both by persistently high (~30%) rates of nonresponse and by deterioration of right ventricular function, owing to iatrogenic dyssynchrony in the context of persistent apical pacing to ensure delivery of biventricular pacing. Left ventricular pacing has long been considered an alternative to standard biventricular pacing and can be achieved as easily as inserting a single pacing electrode in the coronary sinus. Although monoventricular left ventricular pacing has been proven to yield comparable results with the standard biventricular modality, it is the advent of preferential left ventricular pacing, combining both the powerful resynchronization potential of multipolar coronary sinus and right-sided electrodes acting in concert and the ability to preserve intrinsic, physiological right ventricular activation. In this review, we aim to present the underlying principles and modes for delivering left ventricular pacing, as well as to highlight advantages of preferential over monoventricular configuration. Finally, current clinical evidence, following implementation of automated algorithms, regarding performance of left ventricular as compared with biventricular pacing will be discussed. It is expected that the field of preferential left ventricular pacing will grow significantly over the following years, and its combination with other advanced pacing modalities may promote clinical status and prognosis of patients with advanced dyssynchronous heart failure.

Atrioventricular dromotropathy: evidence for a distinctive entity in heart failure with prolonged PR interval?

Heart failure (HF) is often accompanied by atrioventricular (AV) conduction disturbance, represented by prolongation of the PR interval on the electrocardiogram. Studies suggest that PR prolongation exists in at least 10% of HF patients, and it seems more prevalent in the presence of prolonged QRS duration. A prolonged PR interval may result in elevated left ventricular (LV) end-diastolic pressure, diastolic mitral regurgitation, and reduced LV pump function. This seems especially the case in patients with heart disease, in whom it is associated with an increased risk for atrial fibrillation, advanced AV heart block, HF, and death. These findings point towards the importance of proper AV coupling in HF patients. A few studies, strongly differing in design, suggest that restoration of AV coupling in patients with PR prolongation by pacing improves cardiac function and clinical outcomes. These observations argue for AV-dromotropathy as a potential target for pacing therapy, but other studies show inconsistent results. Given its potential clinical implications, restoration of AV coupling by pacing warrants further investigation. Additional possible future research goals include assessing different techniques to measure compromised AV coupling, determine the best site(s) of ventricular pacing, and assess a potential influence of diastolic mitral regurgitation in the efficacy of such therapy.

Outcomes of cardiac resynchronization therapy in patients with atrial fibrillation accompanied by slow ventricular response

It remains unclear as to whether cardiac resynchronization therapy (CRT) would be as effective in patients with atrial fibrillation (AF) accompanied by slow ventricular response (AF-SVR, < 60 beats/min) as in those with sinus rhythm (SR). Echocardiographic reverse remodeling was compared between AF-SVR patients (n = 17) and those with SR (n = 88) at six months and 12 months after CRT treatment. We also evaluated the changes in QRS duration; New York Heart Association (NYHA) functional class; and long-term composite clinical outcomes including cardiac death, heart transplantation, and heart failure (HF)-related hospitalization. Left ventricular pacing sites and biventricular pacing percentages were not significantly different between the AF-SVR and SR groups. However, heart rate increase after CRT was significantly greater in the AF-SVR group than in the SR group (P < 0.001). At six and 12 months postoperation, both groups showed a comparable improvement in NYHA class; QRS narrowing; and echocardiographic variables including left ventricular end-systolic volume, left ventricular ejection fraction, and left atrial volume index. Over the median follow-up duration of 1.6 (interquartile range: 0.8–2.2) years, no significant between-group differences were observed regarding the rates of long-term composite clinical events (35% versus 24%; hazard ratio: 1.71; 95% confidence interval: 0.23–12.48; P = 0.60). CRT implantation provided comparable beneficial effects for patients with AF-SVR as compared with those with SR, by correcting electrical dyssynchrony and increasing biventricular pacing rate, in terms of QRS narrowing, symptom improvement, ventricular reverse remodeling, and long-term clinical outcomes.

Current role of echocardiography in cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure and left ventricular systolic dysfunction. Patients are usually assessed by echocardiography, which provides a number of anatomical and functional information used for cardiac dyssynchrony assessment, prognostic stratification, identification of the optimal site of pacing in the left ventricle, optimization of the CRT device, and patient follow-up. Compared to other cardiac imaging techniques, echocardiography has the advantage to be non-invasive, repeatable, and safe, without exposure to ionizing radiation or nefrotoxic contrast. In this article, we review current evidence about the role of echocardiography before, during, and after the implantation of a CRT device.

Rationale and design of the randomized multicentre His Optimized Pacing Evaluated for Heart Failure (HOPE-HF) trial

Aims

In patients with heart failure and a pathologically prolonged PR interval, left ventricular (LV) filling can be improved by shortening atrioventricular delay using His‐bundle pacing. His‐bundle pacing delivers physiological ventricular activation and has been shown to improve acute haemodynamic function in this group of patients.

In the HOPE‐HF (His Optimized Pacing Evaluated for Heart Failure) trial, we are investigating whether these acute haemodynamic improvements translate into improvements in exercise capacity and heart failure symptoms.

Methods and results

This multicentre, double‐blind, randomized, crossover study aims to randomize 160 patients with PR prolongation (≥200 ms), LV impairment (EF ≤ 40%), and either narrow QRS (≤140 ms) or right bundle branch block. All patients receive a cardiac device with leads positioned in the right atrium and the His bundle. Eligible patients also receive a defibrillator lead. Those not eligible for implantable cardioverter defibrillator have a backup pacing lead positioned in an LV branch of the coronary sinus. Patients are allocated in random order to 6 months of (i) haemodynamically optimized dual chamber His‐bundle pacing and (ii) backup pacing only, using the non‐His ventricular lead.

The primary endpoint is change in exercise capacity assessed by peak oxygen uptake. Secondary endpoints include change in ejection fraction, quality of life scores, B‐type natriuretic peptide, daily patient activity levels, and safety and feasibility assessments of His‐bundle pacing.

Conclusions

Hope‐HF aims to determine whether correcting PR prolongation in patients with heart failure and narrow QRS or right bundle branch block using haemodynamically optimized dual chamber His‐bundle pacing improves exercise capacity and symptoms. We aim to complete recruitment by the end of 2018 and report in 2020.

Diastolic mitral regurgitation following transcatheter aortic valve replacement: Incidence, predictors, and association with clinical outcomes

BACKGROUND

Diastolic mitral regurgitation (DMR) results from atrioventricular conduction disturbances, acute aortic regurgitation, and/or marked elevation of left ventricular filling pressure. Generally benign, in some clinical circumstances DMR has presumed to result in hemodynamic decompensation. The aforementioned causes of DMR are frequently encountered in patients treated by transcatheter aortic valve replacement (TAVR) but its clinical significance in this setting has not been studied. We sought to investigate the incidence of DMR and its prognostic implications following TAVR.

METHODS

Baseline clinical and echocardiographic variables from a prospective TAVR registry were analyzed to determine the correlates of post-procedural DMR and its impact on late outcomes (all-cause mortality and the composite of mortality and readmission due to heart failure).

RESULTS

Of 267 patients undergoing TAVR, post-procedural DMR was present in 25 (9.3%). Independent predictors of DMR included pacemaker implantation [OR=2.7 (95%CI 1.03-6.50)], post-procedural systolic MR and aortic regurgitation [OR=3.7 (1.20-10.80) and OR=4.1 (1.50-10.60), respectively], and use of self-expanding bioprostheses [OR=4.9 (1.60-21.0)]. The incidence of the combined endpoint of death and/or readmission for heart failure was higher in patients with versus those without DMR (25% vs. 41%, respectively, p=0.08), although this association did not attain statistical significance on multivariable analyses. Interaction term analysis indicated a trend toward a heightened risk for the composite endpoint among patients with post-procedural aortic regurgitation (≥moderate) in whom DMR occurred (χ² 2.94, p=0.09).

CONCLUSIONS

Although DMR following TAVR is common (occurring in approximately 1 of 10 patients), it is not independently associated with an increased risk of death and/or readmission for heart failure. Therefore, DMR post TAVR is more likely a marker of cardiac dysfunction than a causative factor.

Surgical Aspects of Cardiac Resynchronisation Therapy

Despite significant advances in the pharmacological treatment of heart failure, rates of mortality and morbidity from the condition remain a concern. The introduction of cardiac resynchronisation therapy (CRT) has been a welcome addition to the treatment strategy of patients who display ventricular dyssynchrony. Several control studies have shown significant benefits from this intervention in particular improved mortality and reduction in symptom burden. In this short review, we focus on several concepts of CRT and discuss the implications of surgical implantation of the left ventricular (LV) lead as compared to the standard transvenous approach.

Outcomes Related to First-Degree Atrioventricular Block and Therapeutic Implications in Patients With Heart Failure

The prevalence of first-degree atrioventricular block in the general population is approximately 4%, and it is associated with an increased risk of atrial fibrillation. Cardiac pacing for any indication in patients with first-degree heart block is associated with worse outcomes compared with patients with normal atrioventricular conduction. Among patients with heart failure, first-degree atrioventricular block is present in anywhere between 15% and 51%. Data from cardiac resynchronization therapy studies have shown that first-degree atrioventricular block is associated with an increased risk of mortality and heart failure hospitalization. Recent studies suggest that optimization of atrioventricular delay in patients with cardiac resynchronization therapy is an important target for therapy; however, the optimal method for atrioventricular resynchronization remains unknown. Understanding the role of first-degree atrioventricular block in the treatment of patients with heart failure will improve medical and device therapy.

Biventricular pacing in heart failure: a review

Biventricular pacing has been an exciting recent advance in the management of drug-refractory heart failure. This new therapy has evolved as much from necessity as scientific observation, since benefits derived from pharmacotherapy currently appear to have reached their peak. Clinical trials of biventricular pacing are establishing morbidity and mortality benefits in heart failure. New challenges in the use of these pacemakers are now arising. These include the accurate diagnosis of ventricular dyssynchrony and, hence, potential responders to the refinement of implantation of the left ventricular lead to the appropriate dyssynchronous ventricular area and optimization of pacemaker programming. This review gives a general overview of the principles and the current evidence for the use of biventricular pacemakers in the treatment of heart failure. In addition, a discussion of current research and future projects is included.

Efficient preloading of the ventricles by a properly timed atrial contraction underlies stroke work improvement in the acute response to cardiac resynchronization therapy

BACKGROUND

The acute response to cardiac resynchronization therapy (CRT) has been shown to be due to 3 mechanisms: resynchronization of ventricular contraction, efficient preloading of the ventricles by a properly timed atrial contraction, and mitral regurgitation reduction. However, the contribution of each of the 3 mechanisms to the acute response to CRT, specifically stroke work improvement, has not been quantified.

OBJECTIVE

To use a magnetic resonance image-based anatomically accurate 3-dimensional model of failing canine ventricular electromechanics to quantify the contribution of each of the 3 mechanisms to stroke work improvement and identify the predominant mechanisms.

METHODS

An MRI-based electromechanical model of the failing canine ventricles assembled previously by our group was further developed and modified. Three different protocols were used to dissect the contribution of each of the 3 mechanisms to stroke work improvement.

RESULTS

Resynchronization of ventricular contraction did not lead to a significant stroke work improvement. Efficient preloading of the ventricles by a properly timed atrial contraction was the predominant mechanism underlying stroke work improvement. Stroke work improvement peaked at an intermediate atrioventricular delay, as it allowed ventricular filling by atrial contraction to occur at a low diastolic left ventricular pressure but also provided adequate time for ventricular filling before ventricular contraction. Reduction of mitral regurgitation by CRT led to stroke work worsening instead of improvement.

CONCLUSION

Efficient preloading of the ventricles by a properly timed atrial contraction is responsible for a significant stroke work improvement in the acute CRT response.

Optimizing cardiac resynchronization therapy for congestive heart failure

In patients with advanced systolic heart failure and mechanical dyssynchrony, cardiac resynchronization therapy (CRT) is an effective means of improving symptoms and reducing mortality. There are now several recognized approaches to optimize CRT. Imaging modalities can assist with identifying the myocardium with the latest mechanical activation for targeted left ventricular lead implantation. Device programming can be tailored to maximize biventricular pacing, and thereby is its benefit. Cardiac imaging has shown that atrioventricular and interventricular intervals can be adjusted to further reduce dyssynchrony. We review these various approaches that maximize the benefit derived from CRT.

Cardiac resynchronization therapy is certainly cardiac therapy, but how much resynchronization and how much atrioventricular delay optimization?

Cardiac resynchronization therapy has become a standard therapy for patients who are refractory to optimal medical therapy and fulfill the criteria of QRS >120 ms, ejection fraction <35% and NYHA class II, III or IV. Unless there is some other heretofore unrecognized effect of pacing, the benefits of atrio-biventricular pacing on hard outcomes observed in randomized trials can only be attributed to the physiological changes it induces such as increases in cardiac output and/or reduction in myocardial oxygen consumption leading to an improvement in cardiac function efficiency. The term “Cardiac Resynchronization Therapy” for biventricular pacing presupposes that restoration of synchrony (simultaneity of timing) between left and right ventricles and/or between walls of the left ventricle is the mechanism of benefit. But could a substantial proportion of these benefits arise not from ventricular resynchronization but from favorable shortening of AV delay (“AV optimization”) which cannot be termed “resynchronization” unless the meaning of the word is stretched to cover any change in timing, thus, rendering the word almost meaningless. Here, we examine the evidence on the relative balance of resynchronization and AV delay shortening as contributors to the undoubted clinical efficacy of CRT.

Cardiac resynchronisation therapy: a randomised trial of factory or echocardiographic settings for optimum response

BACKGROUND

We aimed to assess whether echocardiographically-optimised atrioventricular (AV) and interventricular (VV) delay programming provided any additional benefit over standard settings following biventricular pacemaker implantation in patients with advanced heart failure.

METHODS

Paired data were collected on 22 patients (aged 67.5 ± 8.3 years, 16 male) with refractory heart failure, NYHA class III/IV symptoms, sinus rhythm, LBBB and a broad QRS complex >120 ms. All patients underwent implantation of a biventricular pacemaker and were randomised to eight weeks of factory pacing mode (Mode 1) or echocardiographically-guided pacing mode (Mode 2), followed by eight weeks in the alternate mode, in a randomised blinded crossover design.

RESULTS

Peak oxygen consumption, 6 min walk distance, NYHA class and quality of life scores improved after biventricular pacing, but no significant difference was found between the two modes, with the exception of peak oxygen consumption score (baseline: 14.8 ± 0.9, Mode 1: 14.6 ± 1.2, Mode 2: 16.1 ± 1.2 mL/kg/min), which was better in Mode 2 than Mode 1 (p 0.003).

CONCLUSION

Transthoracic echocardiographic optimisation of AV and VV delays following biventricular pacing may offer additional clinical benefit in an unselected group of patients when compared with factory settings.

Incidence and predictors of pacemaker reprogramming: potential consequences for remote follow-up

AIMS

Remote follow-up (FU) enables to cope with the expanding number of pacemaker (PM) FU. Although remote FU offers comparable monitoring options to in-office FU, reprogramming of device settings is not available, thereby imposing a potentially important restriction to the applicability of remote FU.  The aim of this study was to assess in a large cohort of bradycardia PM recipients, the incidence of PM reprogramming during long-term FU and its predictors, to judge the possibilities for remote FU.

METHODS AND RESULTS

Between 2003 and 2010 all in-office FU of 1517 bradycardia PM recipients included in the FOLLOWPACE study were recorded. Only 24.5% of all 13 258 recorded FU visits >3 months after implantation were visits-with-reprogramming (VWRs), occurring in 1158 patients (79%). Fifty percent of patients were free of reprogramming at 9 months, and 29% at 24 months. Using multivariable binary logistic regression analysis, the following patient characteristics were predictive for frequent PM reprogramming, defined as >3 VWRs during 3 year FU: age, a history of atrial arrhythmias, PM complication <3 months after implantation, congestive heart failure, PM indication, and lead fixation method. This model had a receiver operating characteristic area of 0.66 (95% confidence interval 0.61-0.71).

CONCLUSION

This study observed a low proportion of VWR (∼25%) during a mean FU of 5.3 years; however, those patients at high risk for PM reprogramming cannot easily be predicted. The vast majority of patients (>80%) do not need frequent reprogramming, suggesting a potential benefit of using remote FU to reduce the number of unnecessary in-office visits.

How to improve outcomes: should we put more emphasis on programming and medical care and less on patient selection?

Many factors contribute to the pathophysiology and progression of heart failure (HF), offering the potential for many synergistic therapeutic approaches to its management. For patients, who have systolic HF, prolonged QRS and receiving guideline-indicated pharmacological therapy, cardiac resynchronization therapy (CRT) may provide additional benefits in terms of symptom improvement and mortality reduction. Nevertheless, in many patients, moderate or severe symptoms may persist or recur after CRT implantation due to either the severity or progression of the underlying disease, the presence of important co-morbidities or suboptimal device programming. Identifying and, where possible, treating the reasons for persistent or recurrent symptoms in patients who have received CRT is an important aspect of patient care. The present review summarizes the available evidence on this topic.

Management of the postoperative pediatric cardiac surgical patient

OBJECTIVE

To review the salient aspects and latest advances in the management of the postoperative pediatric cardiac patient.

DATA SOURCE

A Medline-based literature source.

CONCLUSION

The practice of pediatric cardiac intensive care has evolved considerably over the last several years. These efforts are the result of a collaborative effort from all subspecialties involved in the care of pediatric patients with congenital heart disease. Discoveries and innovations that are representative of this effort include the extension of cerebral oximetry from the operating room into the critical care setting; mechanical circulatory devices designed for pediatric patients; and surgery in very low birth weight neonates. Advances such as these impact postoperative management and make the field of pediatric cardiac intensive care an exciting, demanding, and evolving discipline, necessitating the ongoing commitment of various disciplines to pursue a greater understanding of disease processes and how to best go about treating them.

When is an optimization not an optimization? Evaluation of clinical implications of information content (signal-to-noise ratio) in optimization of cardiac resynchronization therapy, and how to measure and maximize it

Impact of variability in the measured parameter is rarely considered in designing clinical protocols for optimization of atrioventricular (AV) or interventricular (VV) delay of cardiac resynchronization therapy (CRT). In this article, we approach this question quantitatively using mathematical simulation in which the true optimum is known and examine practical implications using some real measurements. We calculated the performance of any optimization process that selects the pacing setting which maximizes an underlying signal, such as flow or pressure, in the presence of overlying random variability (noise). If signal and noise are of equal size, for a 5-choice optimization (60, 100, 140, 180, 220 ms), replicate AV delay optima are rarely identical but rather scattered with a standard deviation of 45 ms. This scatter was overwhelmingly determined (ρ = -0.975, P < 0.001) by Information Content, [Formula: see text], an expression of signal-to-noise ratio. Averaging multiple replicates improves information content. In real clinical data, at resting, heart rate information content is often only 0.2-0.3; elevated pacing rates can raise information content above 0.5. Low information content (e.g. <0.5) causes gross overestimation of optimization-induced increment in VTI, high false-positive appearance of change in optimum between visits and very wide confidence intervals of individual patient optimum. AV and VV optimization by selecting the setting showing maximum cardiac function can only be accurate if information content is high. Simple steps to reduce noise such as averaging multiple replicates, or to increase signal such as increasing heart rate, can improve information content, and therefore viability, of any optimization process.

[Cardiac resynchronization therapy: preoperative screening. How can we reliably predict response to CRT?]

Cardiac resynchronization therapy (CRT) is an established therapy for patients with advanced heart failure, depressed left ventricular function, and wide QRS complex. However, about 30 to 45% of patients do not respond to CRT. Assuming that the main therapeutic action of CRT is the correction of dyssynchronous myocardial contraction, a plethora of echocardiographic dyssynchrony parameters have been proposed to improve the prediction of response to CRT. However, one multicenter study has recently questioned the utility of any of these indexes. This review delineates the various causes of non-response to CRT, explains the different levels and mechanisms of dyssynchrony and gives a critical overview of currently available echocardiographic techniques for assessment of dyssynchrony. Based upon a discussion of the evidence coming from randomized multicenter studies and against the background of national and international cardiac societies' guideline recommendations on CRT, a rational basis for the evaluation of patients for CRT is proposed.

Acute haemodynamic effects of accelerated idioventricular rhythm in primary percutaneous coronary intervention

AIMS

Accelerated idioventricular rhythm (AIVR) is very frequently observed in primary percutaneous coronary intervention (PCI), however knowledge of the haemodynamic effects is lacking.

METHODS AND RESULTS

We studied an ST-segment elevation myocardial infarction cohort of 128 consecutive patients (aged 62±11 years) in whom AIVR occurred following reperfusion during primary PCI. Mean systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were determined during periods of AIVR and sinus rhythm. We grouped patients according to the infarct-related artery and the site of the coronary occlusion. AIVR caused an immediate reduction in SBP (130±27 vs. 98±22 mmHg, p<0.001) and DBP (80±19 vs. 69±16 mmHg, p<0.001) and a small increase in heart rate (78±12 vs. 83±11 bpm, p<0.001) as compared to sinus rhythm, irrespective of infarct-related artery. Both absolute as well as relative reduction in SBP were more pronounced in distal than proximal left coronary artery (LCA) occlusions (36±16 vs. 27±12 mmHg, p<0.01, respectively 25±9 vs. 20±8%, p<0.05). These haemodynamic differences between proximal and distal occlusion sites were not observed in the right coronary artery.

CONCLUSIONS

AIVR following reperfusion is associated with marked reduction in both SBP and DBP, irrespective of infarct-related artery. These haemodynamic effects are accompanied by only a very modest increase in heart rate during AIVR. Patients with a culprit lesion in the proximal LCA showed a smaller reduction in systolic blood pressure than distal LCA lesions.

The use of exercise echocardiography in the evaluation of mitral regurgitation

Mitral regurgitation (MR) is the second most common valvular disease in western countries after aortic stenosis. Optimal management of patients with MR depends on the etiology of the regurgitation and is based predominantly on left ventricular function and functional status. Recent outcome studies report high risk subsets of asymptomatic patients with MR, and practice guidelines underscore the importance of a well-established estimation of exercise tolerance and recommend exercise testing to objectively assess functional status and hemodynamic factors.

Atrioventricular and interventricular delay optimization in cardiac resynchronization therapy: physiological principles and overview of available methods

In this review, the physiological rationale for atrioventricular and interventricular delay optimization of cardiac resynchronization therapy is discussed including the influence of exercise and long-term cardiac resynchronization therapy. The broad spectrum of both invasive and non-invasive optimization methods is reviewed with critical appraisal of the literature. Although the spectrum of both invasive and non-invasive optimization methods is broad, no single method can be recommend for standard practice as large-scale studies using hard endpoints are lacking. Current efforts mainly investigate optimization during resting conditions; however, there is a need to develop automated algorithms to implement dynamic optimization in order to adapt to physiological alterations during exercise and after anatomical remodeling.

Criteria for patient selection in cardiac resynchronization therapy

Since the implementation of cardiac resynchronization therapy (CRT) the prognosis of patients with severe heart failure has been improved owing to a reduction in morbidity and mortality rates, as several multicenter trials have shown. However, several patients treated by CRT still lack improvement or even deteriorate during therapy. In some of them, this might be due to the severity and progression of chronic heart failure. In others, the criteria for the indication of CRT and/or optimized device programming might have not been met. Thus, one important option to improve CRT outcome is to improve CRT patient selection. A lot of publications describing various methods identifying a positive or negative prediction of CRT have been released. In summary, decision making based on all these partly contradictory publications indicate a strong need for guidelines for the use of such expensive therapy. The purpose of this article is to give an overview of CRT and summarize the different methods and the limitations of CRT patient selection parameters. With the focus of the different guidelines, this article tries to give an appropriate overview and aid decision making in CRT patients, including a short view of possible new indications.

Atrial pacing or ventricular backup-only pacing in implantable cardioverter-defibrillator patients

BACKGROUND

The need for pacing support in typical ICD patients is unknown.

OBJECTIVE

This study sought to determine whether atrial pacing with ventricular backup pacing is equivalent to ventricular backup pacing only in implantable cardioverter-defibrillator (ICD) patients.

METHODS

We randomized 1,030 patients from 84 sites with indications for ICDs, with sinus rhythm, and without symptomatic bradycardia to atrial pacing with ventricular backup at 60 beats/min (518) or ventricular backup pacing at 40 beats/min (512). The primary end points were time to death, heart failure hospitalization (HFH), and heart failure-related urgent care (HFUC).

RESULTS

Follow-up was 2.4 ± 0.8 years when the trial was stopped for futility. There were 355 end point events (103 deaths, 252 HFH/HFUC) in 194 patients favoring ventricular backup pacing (event-free rate 77.7% vs. 80.3% for atrial pacing at 30 months; hazard ratio 1.14, upper confidence bound 1.59, prespecified noninferiority threshold 1.21), therefore equivalence between pacing arms was not demonstrated. Overall HFH/HFUC rates were slightly higher during atrial pacing (event-free rate 85.4% vs. 86.4% for ventricular backup pacing). Exploratory analyses revealed that the difference in HFH/HFUC rates was largely seen in patients with a PR interval ≥230 ms. There were no differences between groups for atrial fibrillation, ventricular tachycardia/ventricular fibrillation, quality of life, or echocardiographic measurements. Fewer patients in the atrial pacing group were reported to develop an indication for bradycardia pacing (3.7% vs. 7.3%, P = .0053).

CONCLUSION

Equivalence between atrial pacing and ventricular backup pacing only could not be demonstrated.

CLINICAL TRIALS IDENTIFIER

NCT00281099.

Does biventricular pacing improve hemodynamics in children undergoing routine congenital heart surgery?

Biventricular (BiV) pacing or cardiac resynchronization therapy (CRT) is an established therapy for heart failure in adults. In children, cardiac dyssynchrony occurs most commonly following repair of congenital heart disease (CHD) where multisite pacing has been shown to improve both hemodynamics and ventricular function. Determining which patient types would specifically benefit has not yet been established. A prospective, repeated measures design was undertaken to evaluate BiV pacing in a cohort of children undergoing biventricular repair for correction of their CHD. Hemodynamics, arterial blood gas, electrocardiographic (ECG), and echocardiographic data were collected. Pacing protocol was undertaken prior to the patient's extubation with 20 min of conventional right ventricular (RV) or BiV pacing, preceded and followed by 10 min of recovery time. Multivariate statistics were used to analyze the data with p values <0.05 considered significant. Twenty-five (14 female) patients underwent surgery at a median (range) age of 5.2 (0.1-37.4) months with no early mortality. The Risk-adjusted classification for Congenital Heart Surgery (RACHS) scores were 2 in 14 patients, 3 in eight patients, and 4 in three patients. None had pre-existing arrhythmias, dyssynchrony, or required pacing pre-operatively. No patient required implantation of a permanent pacemaker post-operatively. The median cardio-pulmonary bypass time was 96 (55-236) min. RV and BiV pacing did not improve cardiac index from baseline (3.23 vs. 3.42 vs. 3.39 L/min/m2; p > 0.05). The QRS duration was not changed with pacing (100 vs. 80 vs. 80 ms; p > 0.05). On echocardiography, the time-to-peak velocity difference between the septal and posterior walls (synchrony) during pacing was similar to baseline and was also not statistically significant. BiV pacing did not improve cardiac output when compared to intrinsic sinus rhythm or RV pacing in this cohort of patients. Our study has shown that BiV pacing is not indicated in children who have undergone routine BiV congenital heart surgery. Further prospective studies are needed to assess the role of multisite pacing in children with ventricular dyssynchrony such as those with single ventricles, those undergoing reoperation or those with high RACHS scores.