Cardiac resynchronisation therapy and left bundle branch area pacing
THE CONTEXT
Cardiac resynchronisation therapy (CRT) treats selected patients with heart failure whose left ventricular contraction is poorly coordinated because of left bundle branch block.
Mechanism and lead arrangement
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Left bundle branch block can impair coordinated left ventricular contraction and aggravate heart failure in susceptible patients.
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Conventional CRT uses a right atrial lead, a right ventricular lead and a third lead passed through the coronary sinus into a vein on the left ventricular epicardial surface.
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Simultaneous septal and left ventricular epicardial pacing resynchronises left ventricular contraction.
Patients and benefits
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CRT improves symptoms and quality of life and reduces mortality in patients with NYHA class III–IV heart failure who have sinus rhythm, left bundle branch block and a left ventricular ejection fraction of 35% or less.
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Biventricular CRT also prevents heart failure progression in similar patients with mild NYHA class I–II symptoms.
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CRT devices are more effective in patients in sinus rhythm than in those with AF.
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CRT can be combined with a defibrillator as CRT-D because many patients with heart failure are predisposed to ventricular arrhythmias.
Left bundle branch area pacing
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Emerging evidence suggests that left bundle branch area pacing (LBBAP) is at least as effective at delivering cardiac resynchronisation as biventricular CRT pacing, and it is entering clinical practice.
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In LBBAP, the ventricular lead of a dual chamber pacemaker is advanced deep into the interventricular septum.
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The lead activates the His–Purkinje conduction system rather than local myocardium, resulting in a narrow or near-normal QRS.