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.

Transcatheter patch occlusion of the left atrial appendage using surgical adhesives in high-risk patients with atrial fibrillation.

OBJECTIVES: The efficacy of left atrial appendage (LAA) occlusion using the Transcatheter Patch (TP) (Custom Medical Devices, Athens, Greece) in conjunction with surgical adhesives was assessed. BACKGROUND: The TP is a bioabsorbable device that can be adjusted for the shape and size of the LAA without the risk of perforation. It is attached by a surgical adhesive and is released in 45 min. METHODS: Occlusion of the LAA was performed in 20 high-risk patients, 59 to 89 years of age, with atrial fibrillation. A 2-stage polyethylene glycol surgical adhesive was applied to the distal half of the device. Activation of the adhesive was achieved by direct injection of alkaline solution. Fluoroscopy and transesophageal echocardiography only were used for device placement in 17 patients. In 3 patients, angiography was used as well. Follow-up transesophageal echocardiography was performed upon discharge. RESULTS: The procedure was successful in 17 cases. In the 3 patients in whom angiography was performed, the patch did not attach and was retrieved. In 1 case, the patch was placed beyond the mouth of the appendage, resulting in a residual opening. There was further improvement of the occlusion rate on the follow-up transesophageal echocardiography. There was 1 complication related to the procedure, namely, thrombus was released from the long sheath in the left atrium upon withdrawal and required treatment to be dissolved. No recurrent strokes were reported. CONCLUSIONS: Occlusion of the LAA by the TP is feasible and effective in most patients with atrial fibrillation at high risk for embolic stroke. Angiography before placement probably affects patch adhesion and is contraindicated.

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.

Intra-aortic balloon counterpulsation 50 years later: initial conception and consequent ideas.

For nearly 50 years, intra-aortic balloon counterpulsation (IABC) has been the most widely applied temporary assistance method, operating in series with the heart. It helps wean patients from the heart-lung machine after cardiac operations. It is also used in patients with advanced coronary heart disease before and during cardiac and noncardiac operations as well as during percutaneous interventions. Cases of post-acute myocardial infarction severe cardiogenic shock can also benefit from IABC until or during revascularization or if the latter is impractical. A brief review of mostly experimental attempts is reported as "derivatives" of IABC, as they yielded interesting and sometimes intriguing results that need further investigation.

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.

Myocardial performance index suggests optimal fluid loss during hemodialysis.

BACKGROUND: Patients on long-term maintenance hemodialysis (HD) are at high risk of developing cardiovascular disease and suffering various cardiovascular complications during HD. HYPOTHESIS: The purpose of this study was to evaluate the influence of changing loading conditions on the myocardial performance index (MPI) in patients on long-term HD and to specify an optimal level of fluid loss during HD that would maintain stable global cardiac function. METHODS: The study consisted of 52 patients with end-stage renal failure (ESRF), mean age 56±11.7 y, range: 25-80 y, on regular HD. For each patient a complete echocardiographic-Doppler examination was performed before and after HD. Systolic and diastolic parameters of left ventricular function were measured, and the myocardial performance index (MPI) was calculated. RESULTS: The MPI was significantly prolonged after HD (0.47±0.15 before HD versus 0.59±0.16 after HD, p < 0.001). Mean change in body weight during HD was 2.1±0.86 kg. The MPI did not change significantly in patients with intradialytic weight loss up to 1.75 kg. CONCLUSIONS: The MPI value seems to be independent of acute preload changes only when fluid loss is less than 1.75 kg. A 1.75-kg fluid loss during HD seems to be the optimal goal. In ESRF patients on HD, the MPI seems to be a good indicator of global left ventricular function and potentially a valuable aid in the effort to maintain optimal fluid balance.

The effect of open-chest cardiac resuscitation on mitral regurgitant flow: an on-line transesophageal echocardiographic study in dogs.

INTRODUCTION: We sought to determine the effect of cardiac massage on a pre-existing regurgitant mitral valve during open-chest cardiopulmonary resuscitation (OCCPR) in an animal experiment. METHODS: Our study included 29 dogs that were used as experimental models. We anesthetized them and inserted a transesophageal echocardiographic (TEE) probe. Then we performed a transverse thoracotomy, attempting to produce acute mitral regurgitation (MR). In models that showed cardiac arrest we initiated OCCPR to restore cardiac function. The regurgitant area of mitral jet and left ventricular (LV) diameters and volumes were calculated before and during OCCPR using TEE. RESULTS: Ventricular fibrillation and/or electromechanical dissociation occurred in 13 animals (45%). In 4 models without preexisting MR, no additional regurgitation was detected during OCCPR, while in another 5 with preexisting MR we noticed a slight increase in the regurgitant flow. The regurgitant flow area changed from 0.62 +/- 1 cm2 before to 1.1 +/- 0.36 cm2 during OCCPR (p<0.008). In the 4 animals that had severe damage to the mitral apparatus after the attempts, the regurgitant flow increased from 4.01 +/- 0.93 cm2 to 7.7 +/- 2.6 cm2 (p<0.002). The LV transverse diameter decreased from 4.39 +/- 0.62 cm to 1.54 +/- 0.5 cm and its volume from 60.5 +/- 7.14 cm3 to 17.02 +/- 4.14 cm3 (both p<0.001), thus showing the effectiveness of OCCPR. CONCLUSIONS: Given the presence of preexisting mitral regurgitation, direct cardiac massage during OCCPR would probably be less effective than expected, because of an increase in the amount of the regurgitant.

Transesophageal atrial pacing stress echocardiography: difficulties in the performance and the interpretation of the test.

INTRODUCTION: Transesophageal atrial pacing stress echocardiography (TEAPSE) has been proposed as an alternative stress echo test in selected patients with known or suspected coronary artery disease. The purpose of this study was to determine: (1) whether TEAPSE could serve as a suitable provocative stress test in patients with stroke and (2) to investigate whether the pseudohypertrophy during TEAPSE that has been observed in experimental studies is also seen in the clinical setting. METHODS: TEAPSE at increasing heart rates was performed in 29 patients with stroke. The end-diastolic and end-systolic left ventricular (LV) wall/cavity circumferential area was traced and the ratio was calculated at each pacing stage, as well as the percent systolic thickening. RESULTS: A progressive increase in LV wall thickness was noted at high TEAPSE rates (from 1.31 +/- 0.21 mm at baseline to 1.47 +/- 0.27 mm at +50 beats/min of TEAPSE, p<0.05). The ratio wall/cavity area increased significantly at end diastole (from 1.65 +/- 0.36 at baseline to 2.12 +/- 0.49 at +50 beats/min, p<0.05). Percent systolic thickening was inversely correlated with the increase in wall thickness (r=-0.30, p<0.004) and the ratio wall/cavity area in diastole (r=-0.41, p<0.001). Feasibility of TEAPSE was 52% (15 of the 29 patients). CONCLUSIONS: The occurrence of pseudohypertrophy during TEAPSE in conjunction with the low feasibility rate makes the performance and the interpretation of the test problematic. Therefore, other modalities of stress echocardiography should be considered for routine clinical use and TEAPSE could be applied in specific circumstances when other modalities are either contraindicated or unavailable.

Diurnal correlation of ambulatory blood pressure and interstitial glucose in patients with normal glucose tolerance.

OBJECTIVE: Among the physiological variables whose diurnal profile is governed by circadian rhythmicity, plasma glucose concentrations, and arterial blood pressure constitute key elements of the physiological regulation of energy homeostasis. Evidence on their diurnal association derived from frequent measurements of both variables is, however, lacking in humans. METHODS: We investigated the relationship between blood pressure levels recorded by an ambulatory device and interstitial glucose concentrations on an outpatient basis, in patients with normal glucose tolerance (N=20), either normotensive (group A; N=10), or newly diagnosed with essential hypertension (group B; N=10). RESULTS: In the population throughout the 24-h monitoring period, there was a significant positive correlation between interstitial glucose concentrations and systolic, diastolic, and mean 24-h blood pressure levels, which was retained in patients with hypertension compared with normotensive patients. In patients with newly diagnosed hypertension, interstitial glucose concentrations exhibit significant correlation to systolic blood pressure levels during the 24-h period, but no association with diastolic and mean blood pressure during the night, whereas the reverse is the case in patients with normal glucose tolerance and normal blood pressure. CONCLUSION: Diurnal variations of continuously monitored interstitial glucose concentrations significantly associate with blood pressure levels in both normotensive and hypertensive humans, indicating a common pathway of circadian autoregulation, probably stemming from both central mechanisms and peripheral inputs. Such a pathway might underlie similar pathophysiological aberration in disease states such as the metabolic syndrome.

Effect of dobutamine on left ventricular functional geometry after acute myocardial infarction: experimental study.

INTRODUCTION: Acute myocardial infarction causes left ventricular (LV) remodelling, which forms the substrate for its early and late complications. The aim of this experimental study was to evaluate the acute changes in LV functional geometry after acute myocardial infarction using echocardiography and to investigate the effect of continuous intravenous dobutamine administration on those changes. METHODS: In 22 pigs acute myocardial infarction was induced by ligation of the anterior descending branch of the left coronary artery. In 11 animals dobutamine was administered at a rate of 5 microg/kg/min (Group B), while the remainder (Group A) served as controls. Before infarction and 5, 15, 45 and 75 minutes after, the fractional shortening of the long (FSL) and short (FSS) axes of the LV were measured echocardiographically and the ejection fraction (EF) was calculated. RESULTS: In Group A FSL and EF reduced significantly after infarction (p < 0.0001), while FSS increased significantly (p < 0.05). In Group B FSL and EF reduced significantly 5 minutes after infarction and then returned progressively to normal values after 15 min (EF) and 45 min (FSL). FSS did not change significantly during 75 minutes after infarction. CONCLUSIONS: Dobutamine, administered at a rate of 5 microg/kg/min during acute experimental anterior myocardial infarction, before the appearance of early complications, may prevent the acute, unfavourable remodelling of the LV, as manifested by a decrease in FSL and EF and a compensatory increase in FSS.

Preservation of coronary sinus flow after complete ligation of all coronary arteries.

INTRODUCTION: The contribution of the collateral network to myocardial oxygenation under normal circumstances is not clear. However, it is possible that in diseased myocardium this network may be activated and contributes significantly to cardiac blood supply. The purpose of this study was to examine the coronary sinus flow after acute, synchronous, complete occlusion of all epicardial coronary arteries and to investigate methods to increase the flow in the setting of ischaemia. METHODS: In 8 pigs, the coronary sinus flow was measured after complete ligation of all coronary arteries. In two of the 8 experiments adrenaline and dobutamine were infused into the left ventricular cavity, while clamping of the ascending aorta was performed in another three animals in an effort to increase left ventricular systolic pressure. RESULTS: The mean coronary sinus flow decreased from 36.06 +/- 11.01 ml/min to 5.61 +/- 6.96 ml/min (p < 0.001) after ligation of the coronary arteries. A 67% mean reduction of coronary sinus flow at the first minute after ligation was observed and a progressive decrease of coronary sinus outflow to almost zero within 60 minutes was seen in some experiments. Neither infusion of adrenaline and dobutamine nor ascending aorta clamping increased the coronary sinus flow. CONCLUSIONS: The preservation of coronary sinus flow after the complete occlusion of all coronary arteries indicates that retrograde flow through the collateral network from cardiac chambers may exist. Methods that increase the blood flow through the collateral network may contribute to the improvement of myocardial perfusion in severe coronary insufficiency.

Impact of the time rate of blood pressure variation on left ventricular mass.

OBJECTIVES: Blood pressure (BP) changes are steeper in hypertensive than in normotensive individuals, whereas an increased rate of BP fluctuations is associated with medial hypertrophy of the carotid arteries. We evaluated the association between the rate of BP variation derived from ambulatory blood pressure monitoring (ABPM) data analysis and left ventricular mass (LVM). METHODS: ABPM and echocardiographic measurements of LVM were performed in 365 normotensive, 185 white-coat hypertensive (WCH) and 448 uncomplicated hypertensive individuals. RESULTS: The daytime and night-time rate of systolic blood pressure (SBP) and diastolic BP variation were significantly higher in hypertensive than in normotensive (P < 0.001) and WCH (P < 0.05) individuals. In the entire study population multiple linear regression models revealed independent determinants of LVM in the following rank order: body mass index (beta + 0.266, P < 0.001), daytime SBP (beta + 0.264, P < 0.001), male sex (beta +0.220, P < 0.001), age (beta + 0.203, P < 0.001), daytime heart rate (HR; beta - 0.191, P < 0.001), daytime rate of SBP variation (beta + 0.167, P < 0.001), and SBP dipping (beta - 0.132, P < 0.001). A 0.1 mmHg/min increase in the daytime rate of SBP variation correlated with an increment of 7.087 g (95% confidence interval 4.775-9.399) in the LVM. The addition of the daytime rate of SBP variation in the multiple regression model for the prediction of LVM significantly increased the adjusted model R [R change 0.024 (2.4%); P for change < 0.001]. CONCLUSION: Steeper BP variations may produce a greater stress on the left ventricular wall and may have an additive role to body habitus, BP and HR levels in the detection of cardiac hypertrophy. Target-organ damage in hypertensive patients, in addition to BP levels, dipping status and BP variability, may also be related to a steeper rate of BP oscillations.

Twenty-four-hour heart rate and blood pressure are additive markers of left ventricular mass in hypertensive subjects.

BACKGROUND: We investigated whether mean heart rate (HR(24)) and blood pressure (BP) parameters during 24-h ambulatory BP monitoring (ABP) are independent or additive markers of left ventricular (LV) mass in subjects with newly diagnosed, untreated hypertension. METHODS: A total of 250 patients (40% women, 60% men; mean age 59.6 +/- 11 years) with essential hypertension who were attending the outpatient Hypertension Unit were studied. All patients underwent 24-h ABP and HR monitoring as well as echocardiography for assessment of left ventricular (LV) dimensions and function. RESULTS: A decreasing HR24 or increasing ABP parameters (ie, systolic, diastolic, mean BP, and pulse pressure) were associated with increasing LV mass (P < .001) and wall thickness (P < .01). In multivariate analysis, after adjusting for age, gender, body surface area, body mass index, hematocrit, glucose, cholesterol, smoking, and each of the measured ABP parameters separately, decreasing HR24 was independently related to increasing LV mass in addition to ABP and body size parameters (P < .001). The addition of HR24 in different multivariate models for prediction of LV mass significantly increased the adjusted model r2 (range of r2 change: 0.039 to 0.064, P for change <.05). Decreasing HR24 or HR during daytime (6 am to 10 pm) was associated with a higher likelihood of LV hypertrophy in addition to ABP parameters (adjusted odds ratio 0.92 (CI 0.87 to 0.98), per 1 beat/min greater HR24 P = .002 and 0.93 (CI: 0.87 to 0.98), per 1 beat/min greater HR in the daytime P = .017). CONCLUSION: The 24-h HR and BP during ABP are independent and additive markers of increased LV mass in untreated hypertensive individuals.