Effect of left ventricular pacing mode and site on hemodynamic, torsional and strain indices.

INTRODUCTION: Several reports have indicated that left ventricular (LV) lead placement at an optimal pacing site is an important determinant of short- and long-term outcome. This study investigated the effect of pacing mode (atrioventricular [AV] or ventricular) and site (LV apical or lateral) outside the ischemic region on the LV hemodynamic, torsional and strain indices in the ischemic myocardium. METHODS: Experiments were conducted in anesthetized open-chest pigs (n = 15) 30 min after LAD ligation to investigate the hemodynamic effects of temporary epicardial AV and ventricular LV pacing at the LV apical (outside the ischemic region) or lateral wall. LV hemodynamic data were recorded (ejection fraction, stroke volume, dP/dtmax, systolic pressure, cardiac output and e/e΄ ratio) and torsional (twist, rotation), as well as deformation (radial and circumferential strain), indices of LV function were assessed using two-dimensional speckle tracking imaging. RESULTS: The LV function was highly dependent on the pacing mode and site. LV dP/dtmax, systolic pressure and twist decreased significantly during LV pacing in comparison to sinus rhythm (p = 0.004, p<0.001, p = 0.002, respectively). Torsion in sinus rhythm decreased significantly during AV-pacing at the lateral wall (0.11±0.04°/mm vs. 0.06±0.02°/mm, p = 0.005) but did not change significantly during AV-pacing at the apex (0.07±0.05°/mm). CONCLUSIONS: LV pacing at the apical or lateral wall, in the ischemic myocardium, leads to a suboptimal response in comparison to sinus rhythm. LV pacing at the apex outside the ischemic area exhibits a better response than pacing at the lateral wall, possibly because pacing from this site leads to a more physiological propagation of electrical conduction.

Atrioventricular left ventricular apical pacing improves haemodynamic, rotational, and deformation variables in comparison to pacing at the lateral wall in intact myocardium: experimental study.

Aim. To assess the effect on left ventricular (LV) function of atrioventricular (AV) and ventricular pacing at the LV apical or lateral wall and to compare the normal torsional and deformation pattern of the intact LV myocardium with those created by the aforementioned LV pacing modes and sites. Methods. Experiments were conducted in pigs (n = 21) with normal LV function to investigate the acute hemodynamic effects of epicardial AV and ventricular LV pacing at the LV apical or lateral wall. Torsional and deformation indices of LV function were assessed using speckle tracking echocardiography. Results. AV pacing at the apex revealed a significant reduction in the radial strain of the base (P < 0.03), without affecting significantly the ejection fraction and the LV torsion or twist. In contrast, AV pacing at the lateral wall produced, in addition to the reduction of the radial strain of the base (P < 0.01), significant reduction of the circumferential and the radial strain of the apex (both P < 0.01) as well as of the ejection fraction (P < 0.002) and twist (P < 0.05). Conclusions. In pig hearts with intact myocardium, LV function is maintained at sinus rhythm level when AV pacing is performed at the LV apex.

Apical rotation as an early indicator of left ventricular systolic dysfunction in acute anterior myocardial infarction: experimental study.

INTRODUCTION: The aim of this study was to determine whether left ventricular (LV) apical rotation assessed by speckle tracking echocardiography (STE) can predict global LV systolic dysfunction after acute anterior myocardial infarction (AMI). METHODS: STE analysis was applied to LV short-axis images at the basal and apical levels in 21 open-chest pigs, before and after left anterior descending coronary artery ligation. LV radial and circumferential strain and strain rate, apical and basal rotation, and LV torsion were recorded. RESULTS: LV apical rotation (3.68 ± 1.73° pre-AMI vs. 2.19 ± 1.64° post-AMI, p<0.009), peak systolic rotation rate, and radial and circumferential strain as well as strain rate decreased significantly 30 min postAMI. The LV global torsion decreased significantly. Strain and rotational changes of the LV apex were primarily correlated with ejection fraction (EF), but those of the LV base were not. EF had a significant correlation with the global LV twist (r=0.31, p<0.05). On multivariate linear regression analysis, fractional shortening of the long-axis (FSL) (b=0.58, p<0.001), rotation of the LV apex (b=0.32, p<0.006) and LV dp/dtmax (b=0.26, p<0.02) were independently related with EF. On analysis, of the receiver operating characteristic curve, the area under the curve for apical rotation was 0.765, p<0.006; the best cutoff value of 2.92° had sensitivity 80% and specificity 71% in predicting EF<40%. CONCLUSION: Apical rotation assessed by STE is a potential noninvasive early indicator of global LV systolic dysfunction in AMI and has a satisfactory association with LVEF. Its assessment could be valuable in clinical and research cardiology.