Right ventricular bifocal stimulation in the treatment of dilated cardiomyopathy with heart failure

Abstract

Objective -To describe a new more efficient method of endocardial cardiac stimulation, which produces a narrower QRS without using the coronary sinus or cardiac veins. In dilated cardiomyopathy some degree of delay occurs in myocardial stimulus conduction, which causes QRS widening. Associated lesions in the conduction system also often cause QRS widening. In these cases, when a cardiac pacemaker is necessary, paced QRS is more enlarged, easily achieving 200 ms or even more. The delayed ventricular activation, by itself, provokes systolic and diastolic dysfunction, and increases mitral regurgitation 1 . Since the beginning of cardiac pacing, it has been known that the contraction caused by a paced QRS is less effective than the one resulting from a normal QRS. When the QRS is wide, the increased pressure caused by the first stimulated myocardium area is lessened by the natural complacence of other areas that will be activated later. On the other hand, in the normal contraction, the fast myocardial cell activation creates a mechanical synergism, extremely favorable for taking maximum advantage of the inotropic state. It causes a pressure wave with high dP/dt, which is a faster, highly efficient rise in pressure. In the dilated myocardium, the activation generated by a pacemaker is distributed over a longer time, causing a pressure wave that is more attenuated proportionally to the paced QRS widening. To preserve systolic and diastolic functions, and reduce mitral insufficiency, it appears to be fundamental to pace both ventricles with a normal QRS, or at least with the shortest PRS possible. This can be easily obtained by AAI pacing, when the patient has intra-and atrioventricular conduction systems preserved. In the case of AV block, the resulting ventricular paced QRS (almost always placed on the right ventricle) is very wide. It is possible to have a narrow QRS simultaneously pacing more than one point. Recent studies have shown narrow QRS and improved myocardial contractility, when both ventricles are simultaneously paced 2 . The problem is access to the left ventricle. The first approach was epicardial, which requires a thoracotomy 3 . The alternative is the use of cardiac veins; through the coronary sinus. This method avoids thoracoto- Methods -

Right bundle branch block and heart failure: Can a bifocal right ventricular pacing be an alternative to biventricular pacing?

“…First data in favor of this technique were obtained in 1999 by Pachón Mateos et al [12], who described and used bifocal pacing in 39 patients with dilated cardiomyopathy (including 17 patients affected by Chagas disease), heart failure and indication to permanent pacing: they demonstrated the effi cacy of bifocal pacing compared to conventional right ventricular apical stimulation, with narrowing of QRS complex, reduction in mitral regurgitation, improvements in contractility and diastolic left ventricular function, quality of life and NYHA functional class.…”

Cardiac Pacing Induced Cardiomyopathy: Mith or Reality Sustained by Evidence?

“…Pachón et al [ 66 - 68 ] used bifocal pacing of the RV (conventional electrodes in septum and apex) in an attempt to promote the resynchronization of the LV. Despite the relatively small number of patients, the authors observed a reduction in diQRS and mitral regurgitation, in addition to significant improvement of systolic and diastolic function, which resulted in functional and quality of life improvements for the individuals.…”

Terapia de ressincronização cardíaca nas cardiomiopatias chagásica e não chagásicas

“…A TRC tende a atingir benefício máximo quanto mais próximo de 100% for a porcentagem de estimulação biventricular (Jaffe e Morin, 2014 (Delgado et al, 2011). Adicionalmente, a quantidade de fibrose miocárdica avaliada por ressonância nuclear magnética cardíaca ou por imagem na medicina nuclear pode estar correlacionada aos não respondedores (White et al, 2006;Adelstein e Saba, 2007;Wong et al, 2013) Com o universo da TRC no paciente chagásico pouco explorado, a aplicação de outras técnicas de ressincronização puderam ser discutidas nessa população como a estimulação bifocal (Pachón Mateos et al, 1999;Pachón et al, 2001).…”