Cardiac resynchronisation therapy in patients with chronic heart failure

Chronic Atrial and Ventricular Pacing in the Mouse

BACKGROUND

The mouse is the most widely used mammal in experimental biology. Although many clinically relevant in vivo cardiac stressors are used, one that has eluded translation is long-term cardiac pacing. Here, we present the first method to chronically simulate and simultaneously record cardiac electrical activity in conscious mobile mice. We then apply it to study right ventricular pacing induced electromechanical dyssynchrony and its reversal (resynchronization).

METHODS AND RESULTS

The method includes a custom implantable bipolar stimulation and recording lead and flexible external conduit and electrical micro-commutator linked to a pulse generator/recorder. This achieved continuous pacing for at least 1 month in 77% of implants. Mice were then subjected to cardiac ischemia/reperfusion injury to depress heart function, followed by 4 weeks pacing at the right ventricle (dyssynchrony), right atrium (synchrony), or for 2 weeks right ventricle and then 2 weeks normal sinus (resynchronization). Right ventricular pacing-induced dyssynchrony substantially reduced heart and myocyte function compared with the other groups, increased gene expression heterogeneity (>10 fold) comparing septum to lateral walls, and enhanced growth and metabolic kinase activity in the late-contracting lateral wall. This was ameliorated by restoring contractile synchronization.

CONCLUSIONS

The new method to chronically pace conscious mice yields stable atrial and ventricular capture and a means to dissect basic mechanisms of electromechanical physiology and therapy. The data on dyssynchrony and resynchronization in ischemia/reperfusion hearts is the most comprehensive to date in ischemic heart disease, and its similarities to nonischemic canine results support the translational utility of the mouse.

Early and Late Effects of Cardiac Resynchronization Therapy in Adult Congenital Heart Disease

Background

There are limited data about cardiac resynchronization therapy (CRT) in adult congenital heart disease. We aimed to assess early and late outcomes of CRT among patients with adult congenital heart disease.

Methods and Results

We retrospectively studied 54 patients with adult congenital heart disease (median age, 46 years; range, 18–73 years; 74% men) who received CRT implantation (biventricular paced >90%) between 2004 and 2017. Clinical and echocardiographic data were analyzed at baseline and early (mean±SD: 1.8±0.8 years) and late (4.7±0.8 years) follow‐up after CRT. Compared with baseline, CRT was associated with significant improvement at early follow‐up in New York Heart Association functional class, QRS duration, and cardiothoracic ratio (P<0.05 for all); improvement in New York Heart Association class was sustained at late follow‐up. Among patients with a systemic left ventricle (LV; n=39), there was significant increase in LV ejection fraction and reduction in LV end‐systolic volume at early and late follow‐up (P<0.05 for both). For patients with a systemic right ventricle (n=15), there was a significant early but not late reduction in systemic right ventricular basal and longitudinal diameters. Eleven patients died, and 2 had heart transplantation unrelated to systemic ventricular morphological characteristics. Thirty‐five patients (65%) responded positively to CRT, but only baseline QRS duration was predictive of a positive response.

Conclusions

CRT results in sustained improvement in functional class, systemic LV size, and function. Patients with a systemic LV and prolonged QRS duration, independent of QRS morphological characteristics, were most likely to respond to CRT.

Treatment of chronic heart failure in the 21st century: A new era of biomedical engineering has come

Chronic heart failure (CHF) is a challenging burden on public health. Therapeutic strategies for CHF have developed rapidly in the past decades from conventional medical therapy, which mainly includes administration of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and aldosterone antagonists, to biomedical engineering methods, which include interventional engineering, such as percutaneous balloon mitral valvotomy, percutaneous coronary intervention, catheter ablation, biventricular pacing or cardiac resynchronization therapy (CRT) and CRT-defibrillator use, and implantable cardioverter defibrillator use; mechanical engineering, such as left ventricular assistant device use, internal artery balloon counterpulsation, cardiac support device use, and total artificial heart implantation; surgical engineering, such as coronary artery bypass graft, valve replacement or repair of rheumatic or congenital heart diseases, and heart transplantation (HT); regenerate engineering, which includes gene therapy, stem cell transplantation, and tissue engineering; and rehabilitating engineering, which includes exercise training, low-salt diet, nursing, psychological interventions, health education, and external counterpulsation/enhanced external counterpulsation in the outpatient department. These biomedical engineering therapies have greatly improved the symptoms of CHF and life expectancy. To date, pharmacotherapy, which is based on evidence-based medicine, large-scale, multi-center, randomized controlled clinical trials, is still a major treatment option for CHF; the current interventional and mechanical device engineering treatment for advanced CHF is not enough owing to its individual status. In place of HT or the use of a total artificial heart, stem cell technology and gene therapy in regenerate engineering for CHF are very promising. However, each therapy has its advantages and disadvantages, and it is currently possible to select better therapeutic strategies for patients with CHF according to cost-efficacy analyses of these therapies. Taken together, we think that a new era of biomedical engineering for CHF has begun.

Matrix Signaling Subsequent to a Myocardial Infarction: A Proteomic Profile of Tissue Factor Microparticles

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The occurrence of an MI activates production of TFMPs.

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We induced an MI in Yucatan miniswine and collected plasma samples over a 6-month period post-MI.

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Experimental groups consisted of infarcted but untreated animals and infarcted animals treated with CRT plus β-blocker.

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Using proteomic profiling, we confirm the heterogeneity of TFMP protein content with respect to physiological status of the host temporally.

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Spatially, the contents of the TFMPs provided information about multiple entities supplemental to what we obtained from assessing a set of 8 currently used cardiac biomarkers.

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The results from this study support recommending TFMP protein content profiling be used prospectively as a viable investigative methodology for chronic ischemic cardiomyopathy to help improve our understanding of β-adrenergic receptor signaling after an MI.

This study investigated the release and proteomic profile of tissue factor microparticles (TFMPs) prospectively (up to 6 months) following a myocardial infarction (MI) in a chronic porcine model to establish their utility in tracking cellular level activities that predict physiologic outcomes. Our animal groups (n = 6 to 8 each) consisted of control, noninfarcted (negative control); infarcted only (positive control); and infarcted animals treated with cardiac resynchronization therapy (CRT) and a β-blocker (BB) (metoprolol succinate). The authors found different protein profiles in TFMPs between the control, infarcted only group, and the CRT + BB treated group with predictive impact on the outward phenotype of pathological remodeling after an MI within and between groups. This novel approach of monitoring cellular level activities by profiling the content of TFMPs has the potential of addressing a shortfall of the current crop of cardiac biomarkers, which is the inability to capture composite molecular changes associated with chronic maladaptive signaling in a spatial and temporal manner.

Left Univentricular Pacing by Rate-Adaptive Atrioventricular Delay in Treatment of Chronic Heart Failure

Background

Cardiac resynchronization therapy (CRT) is efficacious in the treatment of chronic heart failure (CHF); however, because it is non-physiological, some patients are unresponsive. The present study used rate-adaptive atrioventricular delay (RAAVD) to track the physiological atrioventricular delay and investigated the effects of left univentricular pacing on CRT.

Material/Methods

Patients with CHF fulfilling the indication of CRT Class I were categorized into a left univentricular pacing by RAAVD group and a standard biventricular pacing group. Preoperative and postoperative electrocardiography QRS duration, echocardiographic indicators, quality of life, cardiac function, and annual treatment cost were estimated. The standard deviation (R_S/R-SD5) of the S/R ratio in lead V₁ at 5 heart rate segments in the left univentricular pacing by RAAVD was calculated, and the accuracy of RAAVD in tracking the physiological AV delay was evaluated.

Results

The comparison between the left univentricular pacing by RAAVD group and the standard biventricular pacing group after operation showed a significantly reduced QRS duration (137±11 vs. 144±11 ms, P<0.05), increased AVVTI (21.84±2.25 vs. 20.45±2.12 cm, P<0.05), reduced IVMD (64.27±12.29 vs. 71.39±13.64 ms, P<0.05), decreased MRA (3.09±1.12 vs. 3.73±1.19 cm², P<0.05), and reduced average annual treatment cost (1.30±0.1 vs. 2.20±0.2 million Yuan, P<0.05). The R_S/R-SD5 in the left univentricular pacing by RAAVD group was negatively correlated with improvements in cardiac function (r=−0.394, P=0.031).

Conclusions

Left univentricular pacing by RAAVD has treatment effects similar to those of standard biventricular pacing, and is an economically and physiologically effective method for biventricular systolic resynchronization in the treatment of CHF.

From evidence-based medicine to personalized medicine, with particular emphasis on drug-safety monitoring

Nowadays, guidelines are derived from the findings of randomized controlled therapeutic trials. However, an overall significant P value does not exclude that some patients may be harmed by or will not respond to the therapeutic agent being studied. Trials in patients with a low risk of events and/or a limited chance of providing significant differences in therapeutic effects require a large patient population to demonstrate a beneficial effect. Composite efficacy endpoints are often employed to obviate the need for a large patient population when low rates of events or limited therapeutic efficacy are anticipated. Results of randomized controlled therapeutic trials are commonly expressed in terms of relative risk reduction, whereas absolute risk reduction allows the calculation of the "number needed to treat" to prevent an adverse outcome. The number needed to treat is a far more clinically relevant variable than relative risk reduction. The clinician's mission is to match treatment to patient with the goal of achieving optimal therapeutic response. Drug-safety monitoring is also of major importance to avoid exposing patients to irreversible adverse effects. Unfortunately, drug-safety monitoring is often overlooked in routine clinical practice. Finally, the lack of long-term therapeutic data (>5-10 years) is an unsolved dilemma, as most trials are limited to a duration of a few months or years.

Meta-Analysis of the Usefulness of Change in QRS Width to Predict Response to Cardiac Resynchronization Therapy

The existing data regarding the role of QRS duration (QRSd) change on cardiac resynchronization therapy (CRT) response show some inconsistent results. We conducted a meta-analysis of data obtained from observational studies to examine the impact of QRS change after CRT device implantation on the clinical and/or echocardiographic response. We searched the PubMed and EMBASE databases for relevant studies published before January 2016. Twenty-seven studies were retrieved for detailed evaluation of which 12 studies with a total population of 1,545 patients met our eligibility criteria. The analysis demonstrated that QRSd narrowing was a positive predictor of response to CRT (mean difference [MD] = -19.24 ms, 95% CI = -24.00 to -14.48 ms, p <0.00001). This effect was consistent in the studies using clinical criteria (MD = -19.91 ms, 95% CI = -27.20 to -12.62 ms, p <0.00001) and in those that used echocardiographic criteria (MD = -19.51 ms, 95% CI = -25.78 to -13.25 ms, p <0.00001). The heterogeneity test showed moderate differences among the individual studies (I² = 42%). Subgroup analysis showed that QRSd change was more pronounced in studies having a follow-up ≤6 months. We did not find significant differences in studies measuring postimplantation QRSd after a certain follow-up period compared with studies measuring QRSd immediately after CRT device implantation. Further studies should clarify the exact timing of QRSd assessments during follow-up. In conclusion, QRSd shortening after CRT device implantation is associated with a favorable clinical and echocardiographic response.