Right ventricular pacing reduces the rate of left ventricular relaxation and filling

Abstract

Right ventricular pacing alters left ventricular synchrony and loading conditions, each of which may independently influence left ventricular relaxation. Addition of a properly timed atrial contraction by using sequential atrioventricular (AV) pacing minimizes changes in left ventricular loading conditions, but ventricular asynchrony persists. To separate the effects of altered loading from those of asynchrony, the effects of right ventricular pacing and sequential AV pacing on the rate of isovolumic pressure decline (relaxation time constant), myocardial (segment) lengthening rate and chamber (minor axis dimension) filling rate were examined. In 12 open chest anesthetized dogs, left ventricular pressure (micromanometer) and either left ventricular free wall segment length transients (n = 6) or minor axis dimension transients (n = 6) were measured during right atrial, right ventricular and sequential AV pacing; length and dimension were measured using ultrasonic crystals. Compared with right atrial pacing, right ventricular pacing produced a decrease in systolic pressure, a reduction in fractional shortening, a prolongation of the relaxation time constant (23.5 +/- 0.7 to 29.8 +/- 0.8 ms, p less than 0.05), slower peak segment lengthening rate (6.2 +/- 0.6 to 4.6 +/- 0.8 s-1, p less than 0.05) and a slower rate of increase in chamber dimension (3.5 +/- 0.1 to 2.7 +/- 0.1 s-1, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of right ventricular pacing on cardiac haemodynamics and transvalvular impedance

“…On the basis of TDI cross-correlation analysis, it has been claimed that apical pacing produces systolic dyssynchrony with preserved diastolic synchrony 20 . However, in agreement with previous studies 13,21 , our experience indicates that a significant diastolic impairment acutely results from ventricular pacing, affecting both the isometric relaxation and the filling process. Indeed, LVP min and E-wave DT were increased, and E' was reduced.…”

Short-Term Effects of Right-Left Heart Sequential Cardiac Resynchronization in Patients With Heart Failure, Chronic Atrial Fibrillation, and Atrioventricular Nodal Block

“…Myocardial relaxation is influenced by chamber load and homogeneity of activation. [15][16][17][18] In previous work, we did not find an improvement in ventricular relaxation with resynchronization therapy, 4 and Auricchio et al 5 found that CRT had only a modest effect on relaxation. This may, however, reflect the more complex influence of Figure 3.…”

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

“…Se ha demostrado que el retraso electromecánico intraventricular, los tiempos de contracción y relajación y la magnitud de la desincronización de la pared ventricular no son idénticos entre las dos situaciones 23 . Sin embargo, no es menos cierto que la estimulación cró-nica desde ápex de VD se asocia a efectos hemodiná-micos adversos [24][25][26] . Además, estudios clínicos y experimentales han demostrado cambios histopatológicos que podrían provocar a largo plazo un remodelado ventricular [27][28][29][30] .…”