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.

Effect of pacing mode and pacing site on torsional and strain parameters and on coronary flow.

BACKGROUND: Right ventricular apical pacing may induce detrimental effects on left ventricular function and coronary flow. In this study, the effects of pacing site and mode on cardiac mechanics and coronary blood flow were evaluated. METHODS: This prospective study included 25 patients who received dual-chamber pacemakers with the ventricular lead placed in the right ventricular apex and presented in sinus rhythm (SR) at their regularly scheduled visits at the pacemaker clinic. Patients underwent complete transthoracic echocardiographic examinations while in SR, followed by noninvasive Doppler assessment of coronary flow in the left anterior descending coronary artery (LAD) and speckle-tracking echocardiography of short-axis planes in SR, atrial pacing (AAI-P), atrioventricular (dual-chamber) pacing (DDD-P), and ventricular pacing (VVI-P). RESULTS: Rotation of the base was significantly decreased with VVI-P compared with AAI-P. Left ventricular twist decreased significantly with DDD-P compared with AAI-P. Circumferential strain of the base significantly decreased with DDD-P and VVI-P compared with SR. The velocity-time integral of diastolic flow in the LAD decreased significantly with DDD-P compared with SR (10.7 ± 2.2 vs 10.2 ± 2.2 vs 8.9 ± 1.6 vs 8.7 ± 2.6 cm in SR and with AAI-P, DDD-P, and VVI-P, respectively, P = .003). Basal rotation and time from onset of the QRS complex to peak basal rotation as a percentage of systole were independently associated with the velocity-time integral of diastolic flow in the LAD during SR and the three pacing modes. CONCLUSIONS: Acute right ventricular apical pacing showed a detrimental effect on left ventricular twist and basal mechanics, with the latter being independently associated with decreased LAD diastolic flow velocity parameters.

Value of apical circumferential strain in the early post-myocardial infarction period for prediction of left ventricular remodeling.

BACKGROUND: Left ventricular (LV) remodeling after acute myocardial infarction (AMI) is related to increased morbidity and mortality. The aim of the present study was to examine whether LV deformational and torsional parameters can predict LV remodeling in patients with AMI. METHODS: Forty-two patients (age 57 ± 14 years) presenting with an anterior ST-elevation AMI and treated with primary percutaneous transluminal coronary angioplasty (PTCA) were included in the study. Four days post MI, LV ejection fraction (EF), LV torsion, longitudinal (4-, 3- & 2-chamber) and circumferential strain of the LV apex were evaluated by conventional and speckle-tracking echocardiography. The echocardiographic study was repeated at 3 months post-AMI and patients with LV remodeling, i.e. an increase >15% in LV end-systolic volume (LVESV), were identified. RESULTS: The 13 patients with LV remodeling had significantly more impaired apical circumferential strain (-7.3 ± 2.2% vs. -18.9 ± 5.2%, p=0.001), EF (42 ± 7% vs. 48.9 ± 6%, p=0.005), LV apical rotation (6.8 ± 4.8° vs. 11.1 ± 4.0°, p=0.027), and LV global longitudinal strain (-9.7 ± 1.9% vs. -12.9 ± 2.9%, p=0.03) on the 4th day post-AMI, in comparison to those without LV remodeling. Apical circumferential strain on the 4th day post-AMI showed the strongest correlation with the LVESV 3 months post-AMI (r=0.76, p=0.001), compared to EF (r=-0.60, p=0.001), global longitudinal strain (r=0.56, p=0.001), and LV apical rotation (r=-0.53, p=0.001). Furthermore, apical circumferential strain demonstrated the highest diagnostic accuracy: area under the receiver operating characteristic (ROC) curve 0.98, with sensitivity 100% and specificity 96% for prediction of LV remodeling, using a cutoff value <-11.0%. CONCLUSION: In patients with anterior AMI, LV apical circumferential strain in the early post-MI period constitutes a significant prognostic factor for LV remodeling at 3 months. Assessment of this parameter may identify patients at high risk for heart failure development.

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.

Factors Influencing the twisting and untwisting properties of the left ventricle during normal pregnancy.

AIMS: During pregnancy, important hemodynamic changes occur, consistent with an increase in preload and decrease in afterload and systemic vascular resistance. The aim of the present study was to investigate the changes in left ventricular (LV) strain and rotational properties during the 3 trimesters of normal pregnancy and to examine the factors that drive these changes. METHODS AND RESULTS: Twenty-seven pregnant women (29.7 ± 6.9 years) and 11 age-matched nonpregnant controls (29.9 ± 5.4 years) were evaluated. Conventional echocardiography and two-dimensional speckle tracking imaging were performed at 8-12 (1st trimester), 21-28 (2nd trimester), and 33-36 (3rd trimester) weeks of pregnancy. LV rotation, twist, untwisting rate, and circumferential strain were measured using the parasternal short-axis views at basal and apical levels. Global longitudinal strain was calculated from the LV apical views. Peak LV twist and peak untwisting rate increased significantly in the 3rd trimester of normal pregnancy (13.48 ± 2.90°, 13.12 ± 3.30°, 16.83 ± 3.61°, P < 0.001; and -111.52 ± 23.54°/sec, -107.40 ± 26.58°/sec, -144.30 ± 45.14°/sec, P < 0.001; in the 1st, 2nd, and 3rd trimester, respectively). Global longitudinal and circumferential strain of the apex decreased significantly from the 2nd trimester. An independent association was found between the change in LV twist and the change in LV end-systolic volume between the 1st and 3rd trimester. Peak untwisting rate at the 3rd trimester correlated significantly with peak twist and LV end-diastolic volume. CONCLUSIONS: During normal pregnancy, LV twist and peak untwisting rate increase in the 3rd trimester and correlate with end-systolic and end-diastolic volume, respectively. Circumferential strain of the apex and global longitudinal strain decrease from the 2nd trimester.

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.

The impact of ultrasound contrast medium administration on the right ventricle in patients with heart failure.

BACKGROUND: The purpose of the present study was to examine the effect of SonoVue™ on right ventricular (RV) dimensions and contractility in patients with heart failure. PATIENTS AND METHODS: Twenty-four patients were divided into two groups. Group A consisted of 15 patients with heart failure and group B (control) of nine patients without heart disease. SonoVue was administered at low (2 ml) and high (4 ml) doses in both groups separately, in a random order. RV dimensions, contractility, peak systolic pressure gradient from tricuspid regurgitation (TRPG) and the time to maximal RV end-diastolic dimension (EDD), as well as the time for RV-EDD to return to the baseline value (recovery), were calculated in every cardiac cycle starting before the administration of SonoVue (baseline) until the recovery of RV-EDD. RESULTS: Low-(group A, p<0.001 and group B, p<0.05) and high-dose (group A, p<0.0001 and group B, p<0.01) contrast infusion increased the RV-EDD compared to baseline values. TRPG increased significantly (p<0.05) in both groups, under low-as well as high-dose. In group A, high-dose compared to low-dose produced a significant delay in the time duration to max RV-EDD (p<0.05) and in the time to RV-EDD recovery (p<0.0001). CONCLUSION: The administration of SonoVue in patients with heart failure was followed by an acute, transient, dose-dependent increase in RV-EDD and TRPG, without any effect on RV contractility.

Effect of dobutamine combined with intra-aortic balloon counterpulsation on left ventricular function early after acute myocardial infarction: experimental study.

Acute myocardial infarction (AMI) causes left ventricular (LV) remodeling, which forms the substrate for its early and late complications. The purpose of this study was to compare the acute effect of dobutamine or intra-aortic balloon pumping (IABP), alone or in combination, on LV function in the early phase of an experimental AMI. In 18 pigs, AMI was induced by ligation of the left anterior descending artery (LAD). IABP or dobutamine infusion at a rate of 5 µg/kg/min, or a combination of the two, was applied immediately after ligation of the LAD. Echocardiographic measurements of the long and short LV axes were obtained before (baseline) and post LAD ligation and at the end of each intervention for 5, 15, and 30 min. The fractional shortening (FS) of both axes, as well as the ejection fraction (EF), was calculated. The combination of dobutamine with IABP increased the EF significantly after the AMI in comparison to dobutamine or IABP alone, and improved the stroke volume, cardiac output, and long axis FS in comparison to IABP alone. Dobutamine alone produced a significantly higher increase of EF in comparison to IABP alone. These results indicate that the combination of dobutamine with IABP may be useful during AMI.

Pacing within the ischemic area significantly decreases the left ventricular ejection fraction during experimental acute myocardial infarction.

BACKGROUND: The aim of this study was to examine the effects on left ventricular (LV) function of LV apical or/and lateral wall pacing during an experimental acute myocardial infarction. METHODS: In 12 anesthetized pigs, epicardial LV pacing at the apex or lateral wall, or at both sites simultaneously, was performed before and after left anterior descending (LAD) ligation. Data concerning LV function were obtained by two-dimensional echo during spontaneous sinus rhythm (SR) and during pacing before and 15, 45, 60, and 90 minutes after LAD ligation. RESULTS: Before ligation of the LAD, pacing at the lateral wall (48.04 ± 6.25%) or both sites (45.71 ± 6.31%) reduced the LV ejection fraction (EF) significantly (P < 0.01) in comparison to SR (55.44 ± 4.10%). However, during pacing at the apex (50.19 ± 6.50%), the reduction was not significant. After LAD ligation, the EF during lateral pacing (43.02 ± 7.71%) was significantly higher than during apical pacing (38.78 ± 8.26%, P < 0.04) but was not significantly different from that during dual-site pacing (41.65 ± 8.69%). CONCLUSIONS: Pacing within the ischemic LV apical zone after LAD ligation impairs left ventricular ejection fraction, as compared with pacing the nonischemic LV lateral wall, and should therefore be avoided in clinical settings where the LV pacing site may be chosen.

Effect of early changes in functional geometry of left ventricular contraction on the development of ventricular fibrillation during acute myocardial ischaemia. An experimental study.

OBJECTIVE: The early appearance of ventricular fibrillation (VF) following acute myocardial infarction (MI) is associated with adrenergic effects and electrical interactions although some early "mechanical" changes may also occur. The aim of the present experimental study was to examine whether early changes in the functional geometry of left ventricular (LV) contraction may be associated with ventricular arrhythmias occurring during the first 120min of MI. METHODS: In 11 swine left anterior descending (LAD) coronary artery ligation was performed. Aortic flow, LV end-diastolic pressure (LVEDP), LV long and short axis lengths were measured and their fractional shortening (FS) was calculated before and during the initial 120min period of MI. RESULTS: LV long axis FS and aortic flow decreased (p<0.001) whereas LVEDP increased (p<0.01) in all 11 animals within 30min following LAD ligation. LV long and short axis lengths and LV short axis FS did not change significantly. VF occurred in 5 of the 11 animals within this 30min period. LV short axis FS decreased (p<0.05) in all 5 animals prior to VF and increased (p<0.05) in all 6 animals without VF. In 3 of the 6 animals that had no VF during the initial 30min VF occurred later. Similarly, LV short axis FS decreased prior to VF in all those 3 animals. LV short axis FS did not decrease in any of the remaining 3 swine without VF during the same period of time. CONCLUSION: Early changes in the functional geometry of LV contraction, in the form of a reduction of LV short axis FS, are associated with a greater incidence of VF in experimental acute MI.