Will biventricular pacing replace right ventricular pacing for antibradycardia therapy?

Abstract

Evaluation of: Curtis AB, Worley SJ, Adamson PB, et al; Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK HF) Trial Investigators. Biventricular pacing for atrioventricular block and systolic dysfunction. N. Engl. J. Med. 368(17), 1585–1593 (2013).

Recent trials have shown the benefit of cardiac resynchronization (CRT) in mild or moderate heart failure with a left bundle branch block or intraventricular conduction delay. Randomized trials (including the BLOCK-HF study) have now shown that irrespective of baseline QRS duration, long-term left ventricular (LV) remodeling, dysfunction and heart failure are more common in patients with long-term conventional right ventricular (RV) than those with biventricular (BiV) pacing. The detrimental effects of long-term RV pacing may occur in patients with normal and abnormal LV ejection fractions (LVEF). LV dysfunction induced by RV pacing can be improved by upgrading to a BiV system. Possible new indications for CRT (currently under investigation), include heart failure due to diastolic dysfunction (normal LVEF) with left bundle branch block or intraventricular conduction delay in the absence of bradycardia, and conditions not necessarily associated with a wide QRS complex or bradycardia, such as hypertrophic cardiomyopathy and LV non-compaction. The widespread use of CRT will be limited by the greater complications of LV pacing, unfamiliarity with implantation techniques and cost. At first, CRT will be favored in young patients and those with a low LVEF where ventricular pacing is required >40% of the time.

Keywords::

• atrioventricular block
• biventricular pacing
• cardiomyopathy
• cardiac pacing
• cardiac resynchronization
• heart failure
• left ventricular dyssynchrony
• left ventricular remodeling

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• • The indications for cardiac resynchronization (CRT) are no longer limited to patients with a wide QRS complex and advanced heart disease as a result of recent trials that have shown benefit in mild and moderate heart failure.

• • Long-term right ventricular (RV) pacing may cause left ventricular (LV) remodeling and dysfunction even if the LV ejection fraction (LVEF) is normal before implantation. The true incidence of LV remodeling is not well known but it tends to occur especially if RV paces >40% of the time. Some pacemaker-dependent patients with RV pacing do not develop LV dysfunction for reasons that are unclear.

• • RV pacing-induced LV dysfunction may be improved by upgrading to a biventricular (BiV) system.

• • Randomized trials including the BLOCK-HF study have demonstrated that long-term conventional RV pacing is associated with a greater incidence of LV dysfunction compared with BiV pacing. The superiority of CRT over RV pacing also occurs in patients with permanent atrial fibrillation.

• • During the evolution of CRT, BiV pacing should be strongly considered for simple antibradycardia pacing if LVEF ≤35% and in young or pediatric patients. The decision to use CRT for antibradycardia pacing irrespective of QRS duration will have to be individualized in the setting of a normal or slightly decreased LVEF, and in the absence of organizational guidelines. It is unlikely that BiV pacing will completely replace standard RV pacing.

• • Possible emerging indications for CRT (still under investigation) include heart failure with normal LVEF (diastolic dysfunction) and left bundle branch block or intraventricular conduction delay and hypertrophic obstructive cardiomyopathy.

• • The BLOCK-HF trial highlighted that the complications of CRT due to LV lead implantation are not inconsequential. Such problems may detract from using CRT.

• • So far, CRT has been shown to improve symptoms and the parameters of LV function compared with standard RV pacing. As yet, no mortality reduction has been established. It is likely that longer follow-up will reveal a lower mortality of CRT compared with RV pacing.