Cardiac resynchronization therapy in China

Congestive heart failure (HF) is a major and growing public health problem.The therapeutic approach includes non-pharmacological measures,pharmacological therapy, mechanical devices,and surgery.Despite the benefits of optimal pharmacologic therapy,the prognosis is still not ideal.At this time,cardiac resynchronization therapy (CRT) has gained wide acceptance as an alternative treatment for HF patients with conduction delay. As an innovative,pacemaker-based approach to the treatment of patients with HF,CRT uses a three-lead     

Cardiac resynchronization therapy: what? Who? When? How?

Cardiac resynchronization therapy is an important and underused tool to help patients with heart failure symptoms, left ventricular systolic dysfunction (LVEF ≤ 35%), and intraventricular conduction system disease (QRS ≥ 120 msec). Cardiac resynchronization therapy paces the heart simultaneously from both right and left ventricles (through the coronary sinus). Approximately three quarters of patients who undergo a successful implant will have some degree of symptomatic improvement and have fewer heart failure hospitalizations. When cardiac resynchronization therapy is combined with a defibrillator, patients may benefit from the added protection against sudden arrhythmic death.     

Cardiac resynchronization therapy—How big of a miracle?

This review examines the clinical benefit of cardiac resynchronization therapy (CRT) in patients with severe heart failure symptoms and interventricular conduction delay. The magnitude of CRT effects on exercise duration, quality of life, and reversal of adverse remodeling are compared to angiotensin-converting enzyme (ACE) inhibitor therapy and combined β-blocker/ACE inhibitor therapy. Overall, CRT delivers substantial improvement in clinical well-being to an extent similar to or greater than what would be expected with neurohormonal intervention alone.     

Cardiac resynchronization therapy or atrio-biventricular pacing-what should it be called?

Reduced cardiac efficiency caused by suboptimal synchronization of the heart's normal contraction might contribute to the development of or exacerbate heart failure. Conceptually and in practice cardiac dyssynchrony is complex. Recent studies have shown that atrio-biventricular pacing can improve cardiac synchrony in many patients and improve cardiac function, symptoms and exercise capacity, and reduce morbidity and mortality substantially. Randomized controlled trials, however, indicate that the severity of cardiac dyssynchrony, as conventionally measured, is a poor guide to treatment benefit and that correction of dyssynchrony accounts for only part of the benefit of atrio-biventricular pacing. Although some of the benefits of atrio-biventricular pacing might be mediated by cardiac resynchronization, much of the benefit could be mediated by mechanisms that are as yet unknown. Withholding atrio-biventricular pacing in patients who do not exhibit cardiac dyssynchrony on imaging but otherwise fulfil the entry criteria used in randomized controlled trials of this therapy could be unwise. Here, we examine the evidence that cardiac resynchronization is indeed the mechanism by which atrio-biventricular pacing exerts its effects.     

Cardiac resynchronization therapy in congenital heart disease

Cardiac resynchronization therapy (CRT) is an established treatment option for adult patients suffering heart failure due to idiopathic or ischemic cardiomyopathy associated with electromechanical dyssynchrony. There is limited evidence suggesting similar efficacy of CRT in patients with congenital heart disease (CHD). Due to the heterogeneity of structural and functional substrates, CRT implantation techniques are different with a thoracotomy or hybrid approach prevailing. Efficacy of CRT in CHD seems to depend on the anatomy of the systemic ventricle with best results achieved in systemic left ventricular patients upgraded to CRT from conventional pacing. Indications for CRT in patients with CHD were recently summarized in the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS) Expert Consensus Statement on the Recognition and Management of Arrhythmias in Adult Congenital Heart Disease and are presented in the text.     

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 resynchronization therapy in the elderly heart failure patient

Ms. BP is an 83 year old white female with a long history of congestive heart failure (HF). She is now symptomatic with minimal exertion, has a left ventricular ejection fraction (LVEF) of 20%. Her CHF is due to hypertension (HTN) plus coronary artery disease (CAD) and she is on angiotensin converting enzyme inhibitor (ACEI), furosemide, digoxin, spironolactone, low dose beta blocker and nitrates. Her beta-natriuretic peptide (BNP) in clinic is 3030 pg/ml, heart rate (HR) 100, blood pressure (BP) 89/43. She has rales, jugular venous distention and pedal edema.AnⅡ/Ⅵpansystolic murmur is appreciated over her entire precordium and an S3 is apparent. Her electrocardiogram (ECG) is shown in Figure 1 and reveals sinus tachycardia with a prolonged QRS duration of 159 milliseconds. Her husband brings in a new article about Biventricular pacing and asks you if it will help her. You review her most recent echocardiogram which reveals: LV chamber severely enlarged (LV end diastolic dimension=6.2 cm); Wall motion globally impaired (LVEF=20%); Right ventricle (RV)at normal size with moderate to severe RV dysfunction; Left atrium (LA) moderately to severely enlarged; Right atrium (RA) mildly to moderately enlarged; Moderate to severe mitral regurgitation; Severe tricuspid regurgitation (TR); Estimated cardiac output=3 L/min; Pulmonary artery systolic pressure 89 mmHg; And impaired LV relaxation. Her husband is very socially conscious and you anticipate a bevy of questions. What is your response?     

Cardiac resynchronization therapy in the elderly: a realistic option for an increasing population?

Cardiac resynchronization therapy (CRT) has become a mainstay of heart failure treatment. Since heart failure is a disease primarily affecting older patients it is important to evaluate the performance of CRT in this population. Elderly has been suggested as a subgroup less likely to benefit from CRT. This is an important issue that should be clarified, because most patients with heart failure are old. The present review discusses the available data concerning cardiac resynchronization therapy in the elderly, focusing on efficacy, indication, safety, and impact of co-morbidities.     

Cardiac resynchronization in heart failure: well-established therapy or new approach with unanswered questions?

Biventricular pacing is a new development in the treatment of ventricular failure associated with intraventricular conduction delays, and the term ventricular resynchronization has been coined, implying for many authors that synchronous right and left ventricular activation and contraction are the goal of therapy. However, there is ample evidence that isolated left ventricular stimulation may be at least as efficacious as biventricular stimulation, and the mechanisms of functional improvement remain speculative. The role of mitral regurgitation and its modification with resynchronization has not been fully evaluated. Long-term prognosis, effect on mortality and predictors of a positive response are important unanswered questions. It is clear that a narrow-based QRS complex is not a good indicator of a favorable response. We need to better understand the effect of the activation sequence on left ventricular contraction dynamics, including mitral valve function, to refine the technique and indications for resynchronization therapy.     

Cardiac resynchronization therapy: who is suitable? Who requires an additional ICD as a backup?

Cardiac resynchronization therapy (CRT) has significant positive effects on the quality of life, enables patients to cope more efficiently with cardiopulmonary stress and leads to a reduction of total mortality in patients suffering from congestive heart failure NYHA classes III and IV, reduced ventricular function and left bundle branch block with a QRS complex wider than 150 ms. In a large number of patients suited for CRT, an additional defibrillator function seems to work out well concerning an additional prognostic improvement by means of reducing sudden cardiac death. Due to partially contradictory study outcomes, it still remains to be discussed whether all patients suited for CRT really need an ICD.     

Lymphedema: which drug therapy?

Treatment of primary or secondary lymphedema includes essentially complex decongestive physiotherapy. For many years now, drugs active in reducing volume of lymphedema are prospected. But few studies are available. Only few drugs have been tested. Diuretics have been the first to be used with short and brief efficacy. Benzopyrones were the most tested product with encouraging but conflicting results. New treatments are proposed without randomized controlled studies. Prevention of lymphedema remains essential in particular after treatment of breast cancer.     

What is cardiac resynchronization therapy?

Cardiac resynchronization refers to pacing techniques that change the degree of atrial and ventricular electromechanical asynchrony in patients with major atrial and ventricular conduction disorders. Atrial and ventricular resynchronization is usually accomplished by pacing from more than one site in an electrical chamber--atrium or ventricle--and occasionally by stimulation at a single unconventional site. Resynchronization produces beneficial hemodynamic and antiarrhythmic effects by providing a more physiologic pattern of depolarization. Atrial resynchronization may prevent atrial fibrillation in selected patients with underlying bradycardia or interatrial block. Its antiarrhythmic effect in the absence of bradycardia is unclear. Ventricular resynchronization is of far greater clinical value than atrial resynchronization. Biventricular (or single-chamber left ventricular) pacing is beneficial for patients with congestive heart failure, severe left ventricular systolic dysfunction, dilated cardiomyopathy (either ischemic or idiopathic), and a major left-sided intraventricular conduction disorder, such as left bundle branch block. The change in electrical activation from resynchronization, which has no positive inotropic effect as such, is translated into mechanical improvement with a more coordinated left ventricular contraction. Several recent randomized trials and a number of observational studies have demonstrated the long-term effectiveness of ventricular resynchronization in the above group of patients. The high incidence of sudden death among these patients has encouraged ongoing clinical trials to evaluate the benefit of a system that combines biventricular pacing and cardioversion-defibrillation into a single implantable device.     

Cardiac resynchronisation therapy: what kind of equipment to use?

Cardiac resynchronization therapy is indicated in advanced heart failure refractory to optimal drug treatment patients with left ventricular systolic dysfunction and QRS >120 milliseconds. The choice of the device has to consider several parameters: Do we have to implant a CRT pacemaker or a intracardiac cardioverter defibrillator (ICD)? The prevalence of sudden cardiac death is high in heart failure patients. In patients with an ischemic cardiomyopathy, primary prevention of sudden cardiac death trials suggests to implant a biventricular ICD. In patients with a non ischemic cardiomyopathy, the question is more controversial althought the resullts of the SCD-HeFT and COMPANION trials yielded interesting results for iCD implantation. However, the final decision has to consider the patient's baseline characteristics such as age, presence of comorbidities and cost of the device. Today, devices with totally independent ports of the right and left ventricles have technical advantages and thus are more relevant. Cardiac resynchronization therapy is a heart failure treatment and the new devices provide new tools to assess heart failure parameters such as patient's activity, respiratory parameters or heart rate variability. Left ventricular pacing alone is currently under evaluation such as atrial fibrillation prevention algorithms, atrial fibrillation being frequent in herta failure patients with hemodynamic deleterious consequences.