An Even More Physiological Pacing: Changing the Sequence of Ventricular Activation

Sincronia ventricular em portadores de miocardiopatia dilatada e indivíduos normais: avaliação através da ventriculografia radioisotópica

“…For example, in cases of LBBB, there is an earlier activation of the septal region associated with an stress of lateral region, resulting in delayed contraction of this wall and a great stress of the already activated septum, impairing myocardial contraction 25 . CRT leads to improved electrical activation with consequent improvement of ventricular synchrony and pump function efficiency, as well as reduction of mitral regurgitation [1][2][3][4][5][6] . Approximately 30% of patients receiving a pacemaker for resynchronization do not present the expected benefits.…”

“…On the other hand, a significant proportion of patients with HF, marked left ventricular dysfunction and QRS <120 ms may benefit with this therapy. However, according to the current selection criteria, patients with QRS <120 ms are not candidates to CRT 1,8,26 . Several studies have suggested that the measurement of ventricular dyssynchrony degree by means of diagnostic methods, such as nuclear magnetic resonance, echocardiogram with tissue Doppler and radionuclide ventriculography could better predict the response to CRT [8][9][10][11][12][14][15][16][17]26 .…”

“…With emergence of Cardiac Resynchronization Therapy (CRT) in the beginning of the 1980's, the study of ventricular contraction synchrony became very important 1 . CRT, by means of atrial-biventricular stimulation, improves quality of life and tolerance to exercise; and reduces the number of hospitalizations 2,3 , mortality due to progression of heart failure (HF) and total mortality 4,5 .…”

“…QRS duration has been the main parameter used in the identification of ventricular dyssynchrony 1 . However, increasing evidence has shown a poor correlation between the clinical and functional response to CRT and the duration of QRS interval 8,9 .…”

Tratamiento de la insuficiencia cardíaca avanzada mediante estimulación biventricular. Experiencia inicial en una serie de 22 casos consecutivos

“…La asociación de bloqueo auriculoventricular de primer grado y complejo QRS > 120 ms, específicamente por bloqueo de rama izquierda, produce una asincronía auriculoventricular, interventricular e intraventricular que conduce a una inefectiva contribución auricular al llenado, provoca insuficiencia mitral protodiastólica, acorta la diástole y la contracción isovolumétrica y descoordina la sístole ventricular, reduciendo su eficiencia [3][4][5] . La estimulación auriculobiventricular minimiza estas alteraciones al revertir los retrasos en la conducción auricular, auriculoventricular y ventricular [6][7][8] . Los principales estudios han demostrado que esta técnica mejora la capacidad funcional, la calidad de vida y los parámetros hemodinámicos agudos, aunque hasta la fecha no existen datos concluyentes acerca de su efecto en la supervivencia [9][10][11][12][13] .…”