Effect of heart rate and preload on index of myocardial performance in the normal and abnormal left ventricle

Right Ventricle Function: The Role of the Forgotten Chamber in Mitral Valve Surgery

BACKGROUND

Referred to as the "forgotten chamber," the right ventricle (RV) is now widely acknowledged as a significant factor, particularly in certain cardiovascular pathologies. Despite historically being undervalued in comparison to the left ventricle, the RV function is deemed crucial in determining patient outcomes following mitral valve (MV) surgery. In the context of MV surgery, it is important to note that the RV is highly susceptible to dysfunction before, during, and after the surgical procedure. This vulnerability is also partly compounded by a lack of precise preoperative assessment, appropriate intraoperative management, and sufficient postoperative care for the RV. Moreover, it is notable that the current preoperative risk-score evaluation does not encompass considerations for the RV.

OBSERVATIONS

Sophisticated assessment methodologies, including echocardiography, cardiac magnetic resonance imaging, and invasive hemodynamic procedures, play a pivotal role in accurately evaluating the RV function in patients undergoing MV surgery. These methodologies offer invaluable insights into the extent of RV dysfunction both pre- and postoperatively. By furnishing precise measurements of RV performance, these techniques contribute to risk stratification, guide perioperative management, and may enhance surgical outcomes. Their integration into routine clinical practice is essential for optimizing patient care in the context of MV surgery.

CONCLUSIONS

This review highlights the importance of evaluating the RV before surgery, ensuring proper perioperative care, and utilizing advanced imaging to monitor RV function in order to predict the outcomes. The goal is to enhance surgical outcomes by thoroughly assessing and supporting RV function during the surgical process.

Effect of Postnatal Epigallocatechin-Gallate Treatment on Cardiac Function in Mice Prenatally Exposed to Alcohol

Prenatal alcohol exposure affects the cardiovascular health of the offspring. Epigallocatechin-3-gallate (EGCG) may be a protective agent against it, but no data are available regarding its impact on cardiac dysfunction. We investigated the presence of cardiac alterations in mice prenatally exposed to alcohol and the effect of postnatal EGCG treatment on cardiac function and related biochemical pathways. C57BL/6J pregnant mice received 1.5 g/kg/day (Mediterranean pattern), 4.5 g/kg/day (binge pattern) of ethanol, or maltodextrin until Day 19 of pregnancy. Post-delivery, treatment groups received EGCG-supplemented water. At post-natal Day 60, functional echocardiographies were performed. Heart biomarkers of apoptosis, oxidative stress, and cardiac damage were analyzed by Western blot. BNP and Hif1α increased and Nrf2 decreased in mice prenatally exposed to the Mediterranean alcohol pattern. Bcl-2 was downregulated in the binge PAE drinking pattern. Troponin I, glutathione peroxidase, and Bax increased in both ethanol exposure patterns. Prenatal alcohol exposure led to cardiac dysfunction in exposed mice, evidenced by a reduced ejection fraction, left ventricle posterior wall thickness at diastole, and Tei index. EGCG postnatal therapy restored the physiological levels of these biomarkers and improved cardiac dysfunction. These findings suggest that postnatal EGCG treatment attenuates the cardiac damage caused by prenatal alcohol exposure in the offspring.

Use of proposed systolic and myocardial performance indices derived from simultaneous ECG and PCG recordings to assess cardiac function in healthy Beagles

Background and Aim:

Cardiac time intervals (CTIs) can provide important information on the electrical and mechanical properties of the heart. We hypothesized that cardiac function can be described using the combined power of electrocardiography (ECG) and phonocardiography (PCG) signals. This study aimed to (1) validate a novel custom device in measuring CTI parameters; (2) compare CTI parameters with a commercially available device and standard transthoracic echocardiography (STE); and (3) compare calculated systolic performance index (SPI) and myocardial performance index (MPI) with Tei index from the STE.

Materials and Methods:

This study determined CTIs based on simultaneous ECG and PCG recordings in 14 healthy Beagle dogs using the custom-built device. These CTI parameters were compared with a commercially available device (Eko DUO ECG + Digital Stethoscope; Eko DUO) and the STE. Agreement of CTI parameters between the custom device and the commercially available device or STE was evaluated. Calculated SPI and MPI based on Wigger’s diagram were proposed, compared with SPI and Tei index, and correlated with STE parameters.

Results:

We found that the ECG and PCG parameters measured from the custom-built device did not differ from the commercially available device and the STE. By combining ECG and PCG signals, we established CTI parameters in healthy dogs including indices for systolic function (SPI: QS1/S1S2) and global cardiac function {F1 ([QS1+S2]/S1S2), F2 ([RS1+S2]/S1S2), and F3 (RS1 + [QS2-QT]/S1S2)}. The SPI, F2, and F3 were comparable with echocardiographic parameters describing systolic (Pre-ejection period/left ventricular ejection time [LVET]) and Tei index ([MCOdur-LVET]/LVET), respectively. Only SPI and F3 were correlated significantly with MCOdur and heart rate, respectively.

Conclusion:

We have validated the use of the custom-built device to describe CTIs that are comparable to the commercially available device and STE in healthy Beagles. The proposed SPI and MPI derived from CTI parameters can be useful in clinical practice to describe the cardiac function, especially in areas where access to STE is constrained.

Myocardial performance index in term appropriate and small for gestational age neonates - a cross sectional study

BACKGROUND

It is known that small for gestational age (SGA) babies may be at an increased risk of cardiovascular diseases during adulthood. There is paucity of literature regarding comparative cardiac functions of SGA and appropriate for gestational age (AGA) babies in neonatal period. The present study was conceived to compare the cardiac function of term small and appropriate for gestational age (AGA) babies through a relatively novel echocardiographic index in early neonatal period.

OBJECTIVES

To compare values of myocardial performance index (MPI) index (MPI = IVCT + IVRT/ET) at 48-72 hours of age among AGA and SGA babies.

METHODS

Morphological and anthropometric assessment of serially born term babies was done at time of birth to recruit hundred each of AGA and SGA babies. Tissue Doppler Imaging (TDI) was done between 48-72 hours for each enrolled baby to assess both right and left ventricle MPI in each group.

RESULTS

Mean±SD values for right ventricular MPI in AGA and SGA groups were 0.268 + 0.007 and 0.30 + 0.026 respectively (p < 0.001). Mean±SD values for left ventricular MPI in AGA and SGA groups were 0.25 + 0.012 and 0.30 + 0.017 respectively (p < 0.001). There was significant negative correlation between MPI values for either ventricles and the birth weight (spearmen's rho of -0.66) (p < 0.001). Mean±SD values for LVET in AGA and SGA group were 0.304 + 0.026 and 0.266 + 0.032 respectively (p < 0.001).

CONCLUSION

MPI had a higher absolute value in the SGA babies as compared to AGA babies. These observations point towards suboptimal cardiac performance among SGA babies as compared to AGA babies on the basis of myocardial performance index.

Modulation of left ventricular diastolic filling during exercise in persons with cervical motor incomplete spinal cord injury

PURPOSE

To characterize left ventricular diastolic function during an exertional challenge in adults with incomplete cervical spinal cord Injury (icSCI).

METHODS

In this cross-sectional study, a two-group convenience sample was used to compare left ventricular LV diastolic performance during a 5-10 W·min-1 incremental arm ergometer exercise protocol, using bioimpedance cardiography. Subjects were eight males with cervical incomplete spinal cord injury (icSCI; C5-C7: age 39 ± 14 years) versus eight able-bodied males (CON: age 38 ± 13 years). Left ventricular (LV) diastolic indices included end-diastolic volume (EDV) and early diastolic filling ratio (EDFR). LV ejection time (LVET), inotropic index (dZ/dT2) and stroke volume (SV) were compared between the groups at peak exercise, and maximum workload for the icSCI group (isomax).

RESULTS

EDV (at peak exercise:131.4 ± 7.3 vs 188.78 ± 9.4, p < 0.001; at isomax: 131.4 ± 7.3 vs 169 ± 23, p = 0.0009) and EDFR (at peak exercise 73 ± 14% vs 119 ± 11%, p = 0.006; at isomax 94 ± 10; p = 0.009) were significantly reduced in icSCI compared to CON, respectively. Significant differences in LVET (icSCI: 273 ± 48 vs CON: 305 ± 68; p = 0.1) and dZ/dT2 (icSCI: 0.64 ± 0.11 vs CON: 0.85 ± 0.31; p = 0.1) were not observed at isomax, despite a significant decrease in SV in the subjects with icSCI (77.1 ± 6.05 mL vs 105.8 ± 9.2 mL, p < 0.00) CONCLUSION: Left ventricular filling was impaired in the subjects with icSCI as evidenced at both peak exercise and isomax. It is likely that restrictions on the skeletal muscle pump mechanized the impairment but increased left ventricular wall stiffness could not be excluded as a mediator.

Indexing peak rapid filling velocity to both relaxation and filling volume to estimate left ventricular filling pressures

AIMS

The peak transmitral velocity/peak mitral annular velocity (E/e') ratio has been used as a left ventricular (LV) filling pressure (LVFP) correlate. However, the E/e' and its changes with haemodynamic alterations have not always correlated with changes in LVFP's. We hypothesized that indexing E/e' to a measure of LV filling volume may enhance the correlation with LVFP and LVFP changes.

METHODS AND RESULTS

We summarized previously obtained haemodynamic and Doppler echo data in 137 dogs with coronary microsphere embolization induced-chronic LV dysfunction prior to and following haemodynamic induced alterations in LVFP's. E/e' values were obtained as E*tau where tau is the inverse logarithmic LV pressure decay. E*tau was indexed to LV filling volume by dividing by the diastolic time velocity integral (DVI) and correlated with LV mean diastolic pressure (LVmDP). Similarly, the relationship of E/e' and E/e'/DVI to LV pre A wave pressure was evaluated in 84 patients by invasive haemodynamics and Doppler echo. Combining data from all interventions, LVmDP correlated with E*tau (r = 0.408) but more strongly with E*tau/DVI (r = 0.667, z = 3.03, P = 0.0008). The change in LVmDP correlated with the change in E*tau/DVI (r = 0.742) more strongly than E*Tau (r = 0.187, Z = 4.01, P < 0.0001). In the patient cohort, E/e' was modestly correlated with LV pre A wave pressure (r = 0.301) but more strongly correlated with E/e'/DVI (r = 0.636, z = 2.36, P = 0.0161).

CONCLUSION

Indexing E to both LV relaxation and filling volume results in a more robust relation with LVFP's and with LVFP changes.

The influence of low calcium dialysate on left ventricular diastolic function in peritoneal dialysis patients

Left ventricular (LV) diastolic function was found to be a significant predictor of cardiovascular events and general mortality in dialysis. Studies have indicated that dialysate calcium concentrations were significantly associated with cardiac function. However, the relationship between low calcium dialysate and LV diastolic function has not been clear. The aim of this study was to investigate the influence of low calcium dialysate on cardiac function in peritoneal dialysis (PD) patients. A total of 60 PD patients were enrolled in this study, with a calcium content of the PD solution of 1.25 mmol/L in 30 patients (low-calcium group) and 1.75 mmol/L in 30 patients (standard-calcium group). Standard M-mode and two-dimensional ultrasound measurements were applied to detect the cardiac function. After 12-month follow-up, we found no significant difference in blood pressure, calcium, phosphorus, parathyroid hormone (PTH), etc., between the two groups. Residual renal function (RRF), which is associated with LV cardiac function, was significantly decreased in the standard-calcium group compared with the low-calcium group (5.64 ± 3.23 vs. 9.38 ± 3.17, p = .001). Compared with the low-calcium group, E_max (peak early diastolic velocity) and A_max (peak late diastolic velocity) were significantly decreased (p < .05), whereas myocardial performance index (MPI) was obviously increased in standard-calcium group (9.69 ± 2.71 vs. 7.75 ± 0.93, p < .05). In conclusion, our data suggest that low calcium dialysate treatment is significantly associated with better LV diastolic function.

Effect of Hypoxemia with or without Increased Placental Vascular Resistance on Fetal Left and Right Ventricular Myocardial Performance Index in Chronically Instrumented Sheep

Myocardial performance index (MPI) is increased in growth-restricted fetuses with placental insufficiency, but it is unknown if this is due to fetal hypoxemia or increased placental vascular resistance (R_plac). We used chronically instrumented sheep fetuses (n = 24). In 12 fetuses, placental embolization was performed 24 h before experiments. On the day of the experiment, left (LV) and right (RV) ventricular MPIs were obtained by pulsed Doppler at baseline and in the hypoxemia and recovery phases. At baseline, R_plac was greater and fetal pO₂ lower in the placental embolization group, but RV and LV MPIs were comparable to those of the control group. During hypoxemia, mean LV MPI increased significantly only in fetuses with an intact placenta (0.34 vs. 0.46), returning to baseline during the recovery phase. Right ventricular MPI was unaffected. We conclude that fetal LV function is sensitive to acute hypoxemia. Exposure to chronic hypoxemia could pre-condition the fetal heart and protect its function with worsening hypoxemia.

Three-dimensional transesophageal echocardiography for perioperative right ventricular assessment

BACKGROUND

In high-risk cardiac procedures, dynamic analysis of right ventricular (RV) performance is desirable, but the geometric complexity of the RV limits the applicability of current two-dimensional echocardiographic imaging techniques. This study aimed to evaluate the utility of three-dimensional transesophageal echocardiography (TEE) for the perioperative assessment of RV function and dimensions.

METHODS

Patients undergoing cardiac surgical procedures with complete TEE examinations were identified and reviewed according to current guidelines to exclude patients with significant coexisting valvular regurgitation. Full-volume, three-dimensional datasets were analyzed by two independent investigators using stand-alone software, and left ventricular and RV dimensions were recorded.

RESULTS

Datasets from 50 patients undergoing cardiac surgical procedures were evaluated for this study. The mean RV volume was 111.7 mL (range, 37.5 to 349.7 mL) at end diastole and 67.6 mL (range, 25.5 to 274.4 mL) at end systole. Intraobserver reliability was 0.93 and 0.90 for end diastolic and 0.77 and 0.87 for end systolic volumes. The interobserver reliability for RV volumes was 0.83 at end diastole and 0.86 at end systole. The mean stroke volume was 43.6 mL (range, 12 to 111.2 mL) for the RV and 49.1 mL (range, 19.9 to 102.8 mL) for the left ventricle; the correlation coefficient between the two was 0.85.

CONCLUSIONS

Three-dimensional TEE volumetric measurements were reproducible across a wide range of RV dimensions. As postulated by the continuity principle, stroke volume measurements between both ventricles correlated well, supporting the validity of this approach. Therefore, our work provides preliminary evidence that three-dimensional TEE offers reproducible information about RV function and size in the dynamic and complex perioperative setting of cardiac surgical procedures.

Diagnosis of subclinical central hypothyroidism in patients with hypothalamic-pituitary disease by Doppler echocardiography

OBJECTIVE

The diagnosis of subclinical central hypothyroidism in hypothalamic-pituitary patients cannot be established by serum markers of thyroid hormone action. Myocardial function by echocardiography has been shown to reflect thyroid hormone action in primary thyroid dysfunction. We evaluated the performance of echocardiography in diagnosing subclinical central hypothyroidism.

DESIGN

Cross-sectional and before and after.

METHODS

Echocardiography and serum thyroid hormones were assessed in overt primary (n=20) and central (n=10) hypothyroidism, subclinical primary hypothyroidism (n=10), hypothalamic-pituitary disease with normal free thyroxine (FT(4); n=25), and controls (n=28). Receiver operating characteristic (ROC) curves were generated using overt hypothyroidism patients and selected cut-off values were applied to detect both primary and central subclinical hypothyroidism. After levothyroxine (l-T(4)) intervention, patients were echocardiographically reevaluated at predefined targets: normal thyrotropin (TSH) in primary hypothyroidism, normal FT(4) in overt central hypothyroidism, and higher than pretreatment FT(4) in echo-defined subclinical central hypothyroidism.

RESULTS

Parameters with highest areas under the ROC curves (area under the curve (AUC) ≥0.94) were as follows: isovolumic contraction time (ICT), ICT/ejection time (ET), and myocardial performance index. Highest diagnostic accuracy (93%) was obtained when at least one parameter was increased (positive and negative predictive values: 93%). Hypothyroidism was echocardiographically diagnosed in eight of ten patients with subclinical primary hypothyroidism and in 14 of 25 patients (56%) with hypothalamic-pituitary disease and normal serum FT(4). Echocardiographic abnormalities improved significantly after l-T(4) and correlated (0.05<P<0.001) with changes in FT(4) (-0.62<r<-0.55) and TSH (0.63<r<0.68) in primary hypothyroidism and with FT(4) in central hypothyroidism (-0.72<r<-0.50).

CONCLUSION

Echocardiography can be useful in diagnosing subclinical central hypothyroidism in patients with hypothalamic-pituitary disease.

Improvement of myocardial performance (Tei) index closely reflects intrinsic improvement of cardiac function: assessment in revascularized hibernating myocardium

BACKGROUND

Myocardial performance index (MPI), or Tei index, is an indicator of systolic and diastolic myocardial function. MPI increases in case of cardiac dysfunction; however, whether reversal of left ventricular dysfunction is also reflected by concomitant improvement (i.e., decrease) of MPI is unknown.

METHODS

Fifty-two patients with chronic ischemic cardiomyopathy and viable myocardium by dobutamine stress echocardiography were studied by echocardiography before and more than 4 months after cardiac revascularization. Patients were in optimal medical therapy, which remained unchanged following revascularization.

RESULTS

At baseline, ejection fraction (EF: 32 ± 6%) and wall motion score index (WMSI: 2.37 ± 0.32) were impaired, and MPI averaged 0.71 ± 0.19. Revascularization markedly improved EF (44 ± 10%, P < 0.0001) and WMSI (1.77 ± 0.44, P < 0.0001). MPI also improved (0.59 ± 0.26, P < 0.0001), and its decrease was significantly correlated with the improvement in EF (r =-0.68, P < 0.0001) and to the extent of viable myocardium (r =-0.45, P = 0.0007). Responders to revascularization (≥5% increase in EF at follow-up, n = 40% and 77%) achieved a significant improvement in MPI at follow-up in contrast with nonresponders (-23 ± 25% vs. 0.02 ± 0.18%, P = 0.001). Improvement in MPI was largely driven by a significant reduction in isovolumic contraction time (P < 0.001) with consequent prolongation of the ejection phase.

CONCLUSION

In patients with chronic ischemic cardiomyopathy, MPI improves along with recovery of function, reflecting the intrinsic improvement of viable segments induced by revascularization.

Pre-ejection period by radial artery tonometry supplements echo Doppler findings during biventricular pacemaker optimization

Background

Biventricular (Biv) pacemaker echo optimization has been shown to improve cardiac output however is not routinely used due to its complexity. We investigated the role of a simple method involving computerized pre-ejection time (PEP) assessment by radial artery tonometry in guiding Biv pacemaker optimization.

Methods

Blinded echo and radial artery tonometry were performed simultaneously in 37 patients, age 69.1 ± 12.8 years, left ventricular (LV) ejection fraction (EF) 33 ± 10%, during Biv pacemaker optimization. Effect of optimization on echo derived velocity time integral (VTI), ejection time (ET), myocardial performance index (MPI), radial artery tonometry derived PEP and echo-radial artery tonometry derived PEP/VTI and PEP/ET indices was evaluated.

Results

Significant improvement post optimization was achieved in LV ET (286.9 ± 37.3 to 299 ± 34.6 ms, p < 0.001), LV VTI (15.9 ± 4.8 cm to 18.4 ± 5.1 cm, p < 0.001) and MPI (0.57 ± 0.2 to 0.45 ± 0.13, p < 0.001) and in PEP (246.7 ± 36.1 ms to 234.7 ± 35.5 ms, p = 0.003), PEP/ET (0.88 ± 0.21 to 0.79 ± 0.17, p < 0.001), and PEP/VTI (17.3 ± 7 to 13.78 ± 4.7, p < 0.001). The correlation between comprehensive echo Doppler and radial artery tonometry-PEP guided optimal atrioventricular delay (AVD) and optimal interventricular delay (VVD) was 0.75 (p < 0.001) and 0.69 (p < 0.001) respectively. In 29 patients with follow up assessment, New York Heart Association (NYHA) class reduced from 2.5 ± 0.8 to 2.0 ± 0.9 (p = 0.004) at 1.8 ± 1.4 months.

Conclusion

An acute shortening of PEP by radial artery tonometry occurs post Biv pacemaker optimization and correlates with improvement in hemodynamics by echo Doppler and may provide a cost-efficient approach to assist with Biv pacemaker echo optimization.

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.

Comparison of the effect of pressure loading on left ventricular size, systolic and diastolic function in canines with left ventricular dysfunction with preserved and reduced ejection fraction

Background

Decompensated heart failure may present with severe hypertension in patients with preserved (PreEF) or reduced left ventricular (LV) ejection fraction (RedEF) and is clinically indistinguishable. Previously, we demonstrated that arterial pressure elevation increases LV filling pressures in a canine model of chronic LV dysfunction with PreEF or RedEF. It is not clear whether any differences in hemodynamics, LV volume or performance, or diastolic function can be demonstrated between canines with PreEF or RedEF in response to arterial pressure elevation. We hypothesized that the LV systolic, diastolic, and hemodynamic response to pressure loading would be similar in RedEF or PreEF.

Methods

We studied 25 dogs with chronic LV dysfunction due to coronary microsphere embolization with RedEF (35 ± 4%) and 20 dogs with PreEF (50 ± 3%). Arterial pressure was increased with methoxamine infusion and hemodynamics and echo-Doppler parameters of LV size, function, transaortic and transmitral pulsed Doppler prior to and with methoxamine infusion was obtained.

Results

Though LV filling pressures were similar at baseline, LV size was larger (p < 0.01) and ejection fraction lower in dogs with RedEF (p < 0.001). With methoxamine, there were similar increases in LV size, LV pressures, and index of myocardial performance with the ejection fraction reduced similarly. Diastolic parameters demonstrated similar tau increases, E/A reduction, and diastolic filling shortening in RedEF and PreEF dogs. A similar extent of isovolumic contraction and relaxation times and index of myocardial performance prolongation occurred with pressure loading.

Conclusion

Pressure loading in a canine model of LV dysfunction with PreEF and RedEF resulted in similar degrees of LV dilatation, increased filling pressures, and increased index of myocardial performance.

Myocardial performance index is a predictor of outcome after abdominal aortic aneurysm repair

OBJECTIVE

Perioperative measurement of the myocardial performance index (MPI) with transesophageal echocardiography in patients undergoing elective abdominal aortic aneurysm repair and its association with outcome.

DESIGN

A prospective observational study.

SETTING

A tertiary care university hospital.

PARTICIPANTS

Patients undergoing elective abdominal aortic aneurysm repair.

INTERVENTION

Perioperative transesophageal echocardiography.

MEASUREMENTS

Fifty-one consecutive patients undergoing elective abdominal aortic aneurysm repair were enrolled in the study. The MPI was calculated by using pulse-wave Doppler from the midesophageal window and the deep transgastric position of the probe. In addition, diastolic function was measured as the slope of the transmitral flow propagation velocity, and ejection fraction was calculated as a measure of ventricular systolic function. Comparisons between subjects with uncomplicated versus adverse outcomes were made by using a Mann-Whitney U test. Comparison of the incidence of adverse outcome among subjects with normal and elevated MPIs was made by using a Fisher exact test. Statistical significance was set at p < 0.05.

RESULTS

It was possible to calculate MPI in all patients with transesophageal echocardiography perioperatively. Patients with adverse postoperative outcomes had an elevated MPI as compared with those without any adverse outcome (0.50 v 0.30, p < 0.001). Also, an MPI of > or = 0.36 was associated with a statistically significant higher incidence of complications (congestive heart failure/prolonged intubation) (p < 0.001).

CONCLUSIONS

The MPI is an easily obtained echocardiographic measure of global ventricular performance, which can be measured perioperatively and may be useful as a prospective risk stratification index for patients undergoing elective abdominal aortic aneurysm surgery.

Comparison between pulsed-wave Doppler- and tissue Doppler-derived Tei indices in fetuses with and without congenital heart disease

OBJECTIVES

The aim of this study was to compare the right (RV) and left (LV) ventricular Tei indices obtained by pulsed-wave Doppler (PD) and tissue Doppler (TD) methods in fetuses with structurally normal and abnormal hearts.

METHODS

This was a retrospective cross-sectional study of 147 fetuses that had a fetal echocardiogram and Tei index measured during a 2-year period. The RV and LV Tei indices were measured using both PD and TD methods. The difference between the two methods of Tei index measurement was tested using paired sample t-test, Pearson correlation coefficient was used to examine their relationship, and the agreement between the methods was tested using Bland-Altman analysis.

RESULTS

A total of 87 fetuses had normal hearts and 60 had a congenital heart defect. Both PD and TD Tei indices were measured successfully from at least one ventricle in 123 cases and from both ventricles in 110 cases. The mean TD Tei index was significantly higher than the mean PD Tei index for both ventricles (P < 0.0001). There was a weak but statistically significant correlation between the PD and TD Tei indices of the right ventricle (r = 0.20, P = 0.029), whereas the PD and TD Tei indices of the left ventricle did not correlate significantly (r = 0.04, P = 0.684). When pairs of Tei indices measured by two different methods (123 pairs for the right ventricle and 111 for the left ventricle) were tested with Bland-Altman analysis, the bias and precision were 0.147 and 0.254, respectively, for the right ventricle, and 0.299 and 0.276, respectively, for the left ventricle.

CONCLUSIONS

Correlation between Tei indices measured by PD and TD methods is weak and the agreement between individual measurements is poor. Therefore, they should not be used interchangeably in the assessment of fetal cardiac function.

Volume loading-related changes in tissue Doppler images derived from the tricuspid valve annulus in dogs

OBJECTIVE

To investigate the relationship between preload and tricuspid valve annulus-derived tissue Doppler imaging (TDI) as an index of right ventricular (RV) filling in dogs.

ANIMALS

7 Beagles.

PROCEDURES

Peak systolic RV pressure and RV end-diastolic pressure (RVEDP) were measured in anesthetized dogs. Pulsed Doppler was used to measure tricuspid valve inflow and pulmonary valve outflow velocities. The TDI velocities were measured at the lateral corner of the tricuspid valve annulus. Lactated Ringer's solution was infused at 200 mL/kg/h for 60 minutes via the cephalic vein.

RESULTS

IV infusion significantly increased heart rate, RV pressure, and RVEDP. Early diastolic flow (E-wave) and ejection time significantly increased. The myocardial performance index (MPI) significantly decreased. Intravenous infusion significantly increased the ratio of the E'-wave (peak myocardial velocity during early diastole) to the A'-wave (peak myocardial velocity during late diastole; E':A' ratio) and myocardial velocity during systole (S'), early diastole (E'), and late diastole (A'). The TDI-isovolumic relaxation time and TDI-MPI decreased significantly. The RVEDP was correlated with late diastolic flow (A-wave), ratio of the E-wave to the A-wave (E:A ratio), E'-wave, A'-wave, S'-wave (peak myocardial velocity during systole), TDI-isovolumic relaxation time, TDI-MPI, and ratio of the E-wave to the E'-wave (E: E' ratio). The A-wave and E:A ratio and TDI-derived isovolumic relaxation time, S' duration, and E'-wave could predict the RVEDP.

CONCLUSIONS AND CLINICAL RELEVANCE

The TDI velocities were affected by RV filling pressure in healthy dogs, whereas other TDI profiles, such as MPI and E':A' ratio, were independent of acute filling abnormalities.

Effects of changes in loading conditions and heart rate on the myocardial performance index in cats

OBJECTIVE

To evaluate the effect of changes in hemodynamics on the myocardial performance index (MPI) in cats.

ANIMALS

6 mixed-breed cats.

PROCEDURES

Cats were anesthetized by administration of thiopental sodium; anesthesia was maintained by administration of isoflurane. Systolic arterial pressure and central venous pressure were measured by use of catheters, and heart rate was controlled by right atrial pacing. Afterload was increased by balloon occlusion of the descending aorta, and preload was increased by IV infusion of lactated Ringer's solution at a rate of 40 mL/kg/h. Echocardiography was performed for each condition.

RESULTS

Atrial pacing significantly increased heart rate. The MPI did not change with heart rate. Arterial pressure and MPI increased significantly during aortic occlusion. The IV infusion increased fractional shortening but did not change the MPI. Multiple regression analysis revealed that the MPI was not affected by heart rate, systolic arterial pressure, central venous pressure, fractional shortening, or velocity of the E wave.

CONCLUSIONS AND CLINICAL RELEVANCE

The MPI can be used to assess cardiac function in healthy cats. The MPI is independent of heart rate and systolic arterial pressure but is sensitive to changes in afterload.

Comparison of the myocardial performance index derived by use of pulsed Doppler echocardiography and tissue Doppler imaging in dogs with volume overload

OBJECTIVE

To investigate the relationship between the myocardial performance index (MPI) determined by use of pulsed Doppler (PD) echocardiography and tissue Doppler imaging (TDI) in the response to volume overload-related changes in left ventricle (LV) performance.

ANIMALS

7 male Beagles.

PROCEDURES

Dogs were anesthetized and intubated. A 6-F fluid-filled catheter was placed in the LV to measure LV peak systolic (LVPs) and LV end-diastolic (LVED) pressures. Preload was increased by IV infusion of lactated Ringer's solution (rate of 200 mL/kg/h for 60 minutes) into a cephalic vein. Transmitral flow velocities and aortic outflow were measured, and TDI velocities were obtained from the 4-chamber view.

RESULTS

Acute volume overload induced a significant increase in heart rate, LVPs pressure, and LVED pressure, compared with baseline values. A significant decrease in the PD-MPI and TDI-MPI values and a significant correlation (r = 0.70) between PD-MPI and TDI-MPI were detected. The PD-derived A-wave velocity, ejection time, and isovolumic relaxation time (IRT) and the TDI-derived IRT, MPI, and ratio of the velocity of the E wave to the velocity of the ventricular portion of the E wave during early diastole had equal ability to predict LVED pressure (r(2) = 0.63).

CONCLUSIONS AND CLINICAL RELEVANCE

The TDI-MPI was closely correlated with LV filling pressure and may be helpful in evaluating global cardiac function in dogs.

Effect of preload and heart rate on the doppler and tissue doppler-derived myocardial performance index

Doppler-derived myocardial performance index (MPI) has been described as a noninvasive measurement of LV function. Our aim was to investigate the effect of hemodialysis related volume reduction and heart rate changes on the Doppler-derived LV MPI, and Doppler tissue imaging (DTI) derived left and right ventricular MPI.

METHOD

The study group comprised 32 consecutive patients (mean age: 43 +/- 18 yrs) undergoing hemodialysis. Patients underwent echocardiography before and immediately after hemodialysis session. Left and right ventricular MPI derived from conventional pulsed-wave Doppler and DTI was calculated. The difference in MPI, heart rate and body weight was calculated before and after hemodialysis.

RESULTS

Doppler-derived LV MPI, and right ventricular MPI obtained by DTI were increased (p = 0.05) but the LV MPI obtained by DTI was unchanged after hemodialysis. There is a significant positive correlation between the Doppler-derived LV MPI difference and volume reduction (r = 0.38, p = 0.032). The heart rate difference was correlated with Doppler-derived LV MPI difference, and DTI derived right ventricular MPI difference (r = 0.38, p = 0.034; r = 0.48, p = 0.006, respectively). Whereas, DTI derived LV MPI difference was not correlated with heart rate difference. By the multivariate analysis, there was no correlation between Doppler-derived LV MPI difference with heart rate difference, and volume reduction. Right ventricular MPI difference correlated with heart rate difference (r = 0.41, p = 0.021) but not with volume reduction. Doppler-derived MPI is partially influenced by preload and heart rate changes. However, DTI derived LV MPI is not influenced by preload and heart rate changes.

Effect of External Constraint on the Index of Myocardial Performance in a Canine Model of Left Ventricular Dysfunction

BACKGROUND

With left ventricular (LV) dysfunction, it is not clear how alterations in external constraint influence the index of myocardial performance (IMP). We have previously demonstrated that pericardial constraint is a factor in the production of the restrictive filling pattern. We hypothesized that altering pericardial constraint by changing intracardiac volume or removing the pericardium would produce similar directional changes in LV ejection time (LVET) and isovolumic relaxation time (IRT) resulting in minimal IMP changes.

METHODS

We studied 13 canines with chronic moderate LV dysfunction. LV pressures, transmitral and transaortic Doppler were obtained prior to and following pericardiectomy (PECT) with alterations of intracardiac volume, using inferior vena caval occlusion (IVCO) and volume loading.

RESULTS

With an intact pericardium, IVCO reduced LV size, LV end diastolic pressure (LVEDP), and increased deceleration time (all P < 0.05) but did not affect IMP. Volume loading increased LV size, LVEDP, and shortened deceleration time (all P < 0.05). LVET and IRT lengthened (P < 0.05), and IMP declined (0.58 +/- 0.24 to 0.52 +/- 0.13, P < 0.05). Following PECT, IVCO reduced LV volumes and LVEDP (P < 0.05), but did not change IMP. Volume loading increased LV size, stroke volume, and LVEDP (all P < 0.05). IMP declined (0.57 +/- 0.13 vs 0.51 +/- 0.14, P < 0.05) due to an increase in both LVET and IRT (P < 0.05). Comparison of stages prior to and following PECT revealed an increased LVET and stroke volume (P < 0.05) but a similar IMP.

CONCLUSION

Increases in intracardiac volume associated with elevated LVEDP resulted in reduced IMPs. Pericardiectomy increases LV volumes, stroke volume, and LVET but did not influence IMP.

Isovolumic Acceleration Measured by Tissue Doppler Echocardiography Is Preload Independent in Healthy Subjects

BACKGROUND

Isovolumic acceleration (IVA) as assessed by Tissue Doppler Imaging (TDI) has been proposed as a measure of left ventricular (LV) contractility. IVA is believed to be less dependent on preload than previously proposed estimates. IVA has been measured at different locations, and studies have shown conflicting results.

OBJECTIVES

We investigated the impact of increased preload on modern echocardiographic estimates of contractility, including IVA performed at different locations, in healthy volunteers.

METHODS

Seventeen young healthy individuals (male 13, age 31(+/- 9) years) with no prior history of cardiovascular or metabolic diseases had a Doppler and Tissue Doppler echocardiographic study performed at baseline and after a rapid infusion of 30 ml/kg of bodyweight of isotonic saline. Results are given as mean +/- standard deviation (SD), differences tested by paired t-test.

RESULTS

Echocardiographic parameters used to determine changes in preload, altered significantly. E/e' increased both at the lateral (5 +/- 1 vs 7 +/- 1 P < 0.01) and at the septal side of the annulus (7 +/- 2 vs 9 +/- 2, P < 0.01). Afterload remained unchanged. IVA was unchanged regardless of the measurement location: in the basal free wall (1.21 +/- 0.58 vs 0.98 +/- 0.41, not significant (NS)) or in the mitral annulus (1.18 +/- 0.56 vs 1.15 +/- 0.33, NS). Peak systolic strain, measured at the basal segment of LV septum, increased significantly (15.4 +/- 5.0 vs 20.7 +/- 5, P < 0.05), while all other measurements for strain or strain rate (SR) remained unchanged.

CONCLUSION

IVA is unchanged following significant increases in preload in healthy subjects, and thus is a potentially useful measure of global LV contractility.

Right ventricular myocardial performance index predicts perioperative mortality or circulatory failure in high-risk valvular surgery

BACKGROUND

The prognostic value of right ventricular myocardial performance index (RVMPI) and right ventricular fractional area change (RVFAC) in mitral or aortic valve surgery has not been well described. The main objective of this study is to assess the prognostic value of RVMPI and RVFAC in predicting postoperative mortality or circulatory failure.

METHODS

RVMPI and RVFAC were prospectively measured after induction of anesthesia using transesophageal echocardiography in 50 consecutive patients undergoing corrective mitral or aortic valve surgery. Univariate and multivariate analyses were performed for the primary clinical end point of in-hospital mortality or circulatory failure.

RESULTS

In the study population, the mean age was 67 +/- 9 years. The primary end point occurred in 17 patients (34%); three patients died, and 14 patients presented signs of circulatory failure. Multivariate regression analysis identified RVMPI and RVFAC as variables of prognostic significance.

CONCLUSION

Preoperative RVMPI and RVFAC could have an incremental value in predicting postoperative mortality and morbidity in valvular heart surgery. Future studies are needed to validate these results in a larger population.

Changes in myocardial function and hemodynamics after ligation of the ductus arteriosus in preterm infants

OBJECTIVE

To characterize the changes in systemic hemodynamics and systolic, diastolic, and global myocardial performance after patent ductus arteriosus (PDA) ligation in very-low-birth-weight infants.

STUDY DESIGN

Echocardiograms were performed on 23 neonates (mean gestational age, 26.2 +/- 2.2 weeks) at 2.3 +/- 2.0 hours before PDA ligation (n = 23) and at 2.0 +/- 1.4 hours (n = 23) and 23.5 +/- 2.5 hours after (n = 11) PDA ligation.

RESULTS

Mean blood pressure, heart rate, load-independent contractility, shortening fraction, left ventricular (LV) afterload, and diastolic function did not change. Preload (early and atrial mitral inflow velocities) decreased immediately after ligation but remained unchanged thereafter. LV output decreased and systemic vascular resistance increased after surgery. The LV myocardial performance index (MPI), a measure of global myocardial performance, deteriorated acutely after ligation but improved by 23.5 hours after surgery. Changes in LV MPI were most closely correlated with changes in LV output.

CONCLUSIONS

After PDA ligation, LV output and MPI decrease, due primarily to a decrease in LV preload, although LV contractility and diastolic function do not change. However, the changes in LV MPI after ligation also reflect an acute deterioration followed by an improvement in global cardiac function, because LV loading conditions remained unchanged after surgery and thus cannot explain the improvement in MPI by 24 hours after ligation.

Beat-to-beat change in "myocardial performance index" related to load

BACKGROUND

This study was designed to assess the relationship of the "myocardial performance index" (MPI) to the beat-by-beat change in pre-load with static or unchanged contractile status.

METHODS

Eight anesthetized juvenile pigs were studied using direct measurement of the left ventricular pressure and volume. Transient inflation of a vena cava balloon catheter produced controlled pre-load alterations. Consecutive beats were analyzed, grouped for first, second, third, etc. during the pre-load alteration, and evaluated for the change in MPI during the same contractile status with a controlled pre-load alteration. Two pharmacologic inotropic interventions were also included to generate several myocardial conditions in each animal.

RESULTS

MPI demonstrated a strong linear relationship to the pre-load and after-load. MPI increased progressively during decreasing end-diastolic volume, mostly related to changes in ejection time. MPI was observed at the same level for three different myocardial function conditions (all eight animals), with a different relationship between MPI and pre-load noted for each observation.

CONCLUSIONS

MPI is strongly load dependent, and can vary widely in value for the same contractile status if the load is varied. The use of this index in critically ill patients should be limited in this respect. Further work is needed to establish the relationship of MPI to load and contractile status.

Changes in the myocardial performance index during dobutamine administration in anesthetized cats

OBJECTIVE

To investigate the relationship between myocardial performance index (MPI; also known as the Tei index) and cardiac function in anesthetized cats administered dobutamine.

ANIMALS

6 adult cats.

PROCEDURES

Cats were anesthetized by administration of propofol (6 mg/kg, IV), and anesthesia was maintained by administration of isoflurane. Heart rate and systolic arterial pressure (SAP) were monitored. Stroke volume, cardiac output, and aortic blood flow (ABF) were measured by use of transesophageal ultrasonography. Left ventricular fractional shortening (LVFS), mitral E-wave velocity-to-A-wave velocity (E:A) ratio, and ejection time were measured by use of transthoracic echocardiography. Dobutamine was administrated via a cephalic vein at rates of 2.5, 5.0, and 10 microg/kg/min.

RESULTS

Heart rate, SAP, cardiac output, and ABF increased with dobutamine administration, whereas stroke volume significantly decreased. The LVFS significantly increased, and the E:A ratio significantly decreased. Total isovolumic time and the MPI significantly decreased. The MPI was negatively correlated (r=-0.63) with LVFS. Conversely, the MPI was positively correlated with the E:A ratio (r=0.47), stroke volume (r=0.66), and total isovolumic time (r=0.95). However, the MPI was not significantly correlated with heart rate, SAP, cardiac output, or ABF.

CONCLUSION AND CLINICAL RELEVANCE

Analysis suggested that the MPI provides a sensitive clinical assessment of cardiac response to medication in cats, which may be similar to the usefulness of the MPI reported in humans.

Disturbed glucose metabolism is associated with left ventricular dysfunction using tissue Doppler imaging in patients with myocardial infarction

AIMS

To investigate the association between glucose abnormalities and left ventricular (LV) function assessed by tissue Doppler imaging (TDI) in patients with previous history of myocardial infarction and without known diabetes mellitus.

PATIENTS AND METHODS

In a cross-sectional study, 123 patients, aged 31-80 years, with a history of previous myocardial infarction and without known diabetes mellitus were examined with TDI echocardiography. A standard oral glucose test (OGTT) with 75 g of glucose was performed.

RESULTS

Two-hour plasma glucose were significantly and negatively associated with TDI parameters such as LV ejection time; early diastolic filling velocity (E'-v); ratio of the early to late diastolic filling velocity (E'/A') and positively associated with regional myocardial performance index (MPI) (P<0.05). Left ventricular ejection time and MPI were significantly higher; E'/A' and E'-v were significantly lower in patients with disturbed glucose metabolism compared with patients with normal glucose tolerance (P<0.01). These differences remain significant also when the patients with DM were excluded.

CONCLUSIONS

The present study demonstrates that disturbed glucose metabolism is associated with more pronounced LV dysfunction using TDI in patients with myocardial infarction. These abnormalities in LV function were more common not only in subjects with diabetes, but also in patients with prediabetic condition, impaired glucose intolerance.

Evaluation of cardiac global function using the myocardial performance index by tissue Doppler echocardiography in patients with uremia

OBJECTIVE

The purpose of this study was to assess global ventricular function in patients with uremia by means of the myocardial performance index (MPI) derived from tissue Doppler echocardiography.

METHODS

According to the left ventricular mass index and pericardial effusion, 45 patients with uremia were classified into 2 groups: a uremia group and a uremia with pericardial effusion group. To calculate left ventricular MPI (LVMPI) and right ventricular MPI (RVMPI) by tissue Doppler echocardiography, the isovolumic contraction time (ICT), isovolumic relaxation time (IRT), and ejection time (ET) were measured at different sites in the mitral and tricuspid annuli.

RESULTS

The mean ICT and IRT were longer, the ET was shorter, and the LVMPI and RVMPI were higher in the 2 disease groups than in a control group, and the indices were higher in the uremia with pericardial effusion group than in the uremia group. The increase of the LVMPI was more obvious than that of the RVMPI. There was a significant difference in the mean LVMPI and RVMPI among the 3 groups (P<.01). The MPI was positively correlated with the IRT and the sum of the ICT and IRT and negatively correlated with the ET.

CONCLUSIONS

Both left and right ventricular systolic and diastolic function are impaired in patients with uremia. The MPI could be measured by tissue Doppler echocardiography, and we suggest that this index provides a novel, noninvasive method for clinical research on global myocardial performance in patients with uremia.

Left Ventricular Tei Index in Children: Comparison of Tissue Doppler Imaging, Pulsed Wave Doppler, and M-Mode Echocardiography Normal Values

The Tei index has been found to be useful for analyzing systolic and diastolic global ventricular function in a wide variety of congenital and acquired cardiac abnormalities. However, there are some discrepancies between reports as to the normal values for the Tei index obtained by the different echocardiographic techniques and by different investigators. We conducted a prospective study to determine the normal range of left ventricular Tei index (LVTX) values in a broad sample of children using tissue Doppler imaging, pulsed wave Doppler, and M-mode echocardiography. In all, 289 children with normal echocardiogram findings (age 1 day-18 years, body surface area 0.08-2.4 m(2), heart rate 46-182/min) were studied. The LVTX was calculated by all 3 methods in each patient during a single echocardiographic examination. The normal LVTX values (mean +/- SD) for the 3 techniques were: LVTX-Doppler tissue imaging = 0.38 +/- 0.06; LVTX-pulsed wave Doppler = 0.36 +/- 0.07; and LVTX-M-mode echocardiography = 0.29 +/- 0.08. LVTX-Doppler tissue imaging and LVTX-pulsed wave Doppler values were only slightly but statistically significantly different (P < .05). LVTX-M-mode echocardiography values were consistently and significantly less than those obtained by both of the other two methods (P < .01, respectively). The effects of age, body surface area, and heart rate were not clinically significant. These results are similar but not identical to those from prior studies.

Effect of changes in contractility on the index of myocardial performance in the dysfunctional left ventricle

BACKGROUND

The index of myocardial performance has prognostic power in patients with cardiomyopathy and following myocardial infarction. As the index of myocardial performance has been shown to be preload and afterload dependent, the effect of altering contractility on IMP and its components with left ventricular dysfunction has been incompletely delineated.

METHODS

Chronic left ventricular dysfunction was induced in 10 canines using coronary microsphere embolization. Each dog was instrumented and imaged with 2D echo and Doppler. At the same atrially paced rate, contractility was increased with a dobutamine infusion and then following 4 weeks of oral digoxin.

RESULTS

With chronic left ventricular dysfunction, a reduced left ventricular ejection fraction (42 +/- 3%, p < 0.001) and increased index of myocardial performance (0.58 +/- 0.17, p < 0.01) due to isovolumic contraction time lengthening and shortened left ventricular ejection time were noted. Dobutamine increased ejection fraction (p < 0.001), reduced left ventricular end diastolic pressure (p < 0.01), and reduced the index of myocardial performance (0.33 +/- 0.17, p < 0.001) due to isovolumic contraction time, isovolumic relaxation time, and left ventricular ejection time shortening. Digoxin increased ejection fraction (p < 0.05), reduced left ventricular end diastolic pressure (p < 0.05), and reduced the index of myocardial performance (0.42 +/- 0.13, p < 0.01) due to isovolumic contraction time shortening (p < 0.001). Both dobutamine and digoxin lengthened the diastolic filling period (p < 0.01).

CONCLUSION

Increased inotropy with digoxin and dobutamine reduced the index of myocardial performance in dogs with left ventricular dysfunction. Shortened isovolumic contraction time, increased diastolic filling period, and reduced left ventricular end diastolic pressure with digoxin may provide insight into its efficacy in heart failure.

Effects of modulation of left ventricular contractile state and loading conditions on tissue Doppler myocardial performance index

The Tei index is clinically useful to quantify left ventricular (LV) function, but it requires sequential Doppler recordings from two different views. A related myocardial performance index (MPI) using tissue Doppler (TD) can be rapidly calculated from a single beat; however, its ability to quantify contractility and the effects of acute changes in loading have not been determined. Our aim was to test the hypothesis that TD MPI can quantify contractile state but is affected by acute alterations in loading, using LV pressure-volume relations in an animal model. Eight dogs were studied by using mitral annular TD, high-fidelity pressure, and conductance catheters. TD MPI was calculated as (a' - b')/b', where a' was the duration of mitral annular velocity during diastole and b' was the duration of the systolic wave. End-systolic elastance (Ees), the time constant of isovolumic relaxation (tau), and peak positive and negative first derivative of pressure (dP/dtmax and dP/dtmin, respectively) were used as measures of LV function. Data were obtained at baseline, at dobutamine and esmolol infusion to alter contractile state, and at inferior vena cava and aortic occlusion to alter preload and afterload. TD MPI decreased from 0.83 (SD 0.19) to 0.62 (SD 0.20) with dobutamine and increased to 1.19 (SD 0.26) with esmolol. TD MPI significantly correlated with dP/dtmax (r = -0.76), Ees (r = -0.68), dP/dtmin (r = 0.82), and tau (r = 0.78); however, it was affected by acute decreases in preload [from 0.83 (SD 0.19) to 1.09 (SD 0.36)] and acute increases in afterload [to 1.23 (SD 0.17)]. All the above increases and decreases and r values were significant (P < 0.05 vs. baseline). In conclusion, TD MPI can rapidly quantify alterations in LV contractile state but is affected by acute alterations in preload and afterload.

Comparison of the Tei index with invasive measurements of right ventricular function

The Doppler-derived Tei index has been reported to be clinically useful in assessing global right ventricular function. It could increase in response to combinations of increased pulmonary artery pressure and/or ventricular dysfunction. We compared the Tei index with invasive measurements of right ventricular function during acute pulmonary hypertension. Right and left ventricular pressures, pulmonary and aortic pressures, pulmonary flow and right ventricular volume by sonomicrometry were measured in six anaesthetized sheep. Graded pulmonary arterial hypertension was induced by a mechanical occlusion maneuver. Pressure-volume loops were generated during preload reduction through caval occlusion. Epicardial echocardiograms were also performed. Invasive indexes including preload recruitable stroke work, ventricular diastolic time constant and stiffness constant, and cardiac output were assessed, as were noninvasive echocardiographic indexes including Tei index and E/A ratio. The right ventricular pressure-volume loop became rectangular, with well-defined isovolumic phases. The slope of preload recruitable stroke work was increased significantly during pulmonary pressure of 30 mm Hg. The ventricular time constant showed a significant increase with no change of chamber stiffness during pulmonary pressure of 35 mm Hg. Concomitantly, the Tei index increased significantly from 0.06+/-0.03 to 0.31+/-0.06, together with the shortening of the ejection time and a decrease of the E/A ratio (P<0.05). Thus, the right ventricular Tei index was noted to be affected by acute graded afterload increase. The alteration in invasive measurements of systolic and diastolic function makes the Tei index a sensitive indicator of right ventricular dysfunction in the settings of acute pulmonary hypertension.

Index of myocardial performance is afterload dependent in the normal and abnormal left ventricle

BACKGROUND

The index of myocardial performance (IMP) has been used as a prognostic systolic-diastolic index for patients with dilated cardiomyopathy and postmyocardial infarction. To date, systematic evaluation of afterload alteration (arterial pressure) on IMP has not been performed with normal or reduced left ventricular (LV) function.

METHODS

We studied 15 mongrel dogs at baseline, after the induction of acute ischemic LV dysfunction, and with chronic LV dysfunction. Each dog was atrially paced, and the arterial pressure was reduced with nitroprusside (NTP) (>10 mm Hg) and increased with methoxamine (Methox) (>30 mm Hg) in random order. Hemodynamics and transmitral and transaortic pulsed Doppler were obtained.

RESULTS

With normal LV function, there were no changes in IMP with NTP. Methox reduced IMP (0.51 +/- 0.12-0.45 +/- 0.12, P < .05) as a result of a shortened isovolumic contraction time (ICT). With acute LV dysfunction, IMP declined with NTP (0.74 +/- 0.19-0.65 +/- 0.17, P < .01) because of a shortened ICT and isovolumic relaxation time. Methox prolonged IMP (0.73 +/- 0.16-0.83 +/- 0.21, P < .05). With chronic LV dysfunction, NTP resulted in a reduced IMP (0.75 +/- 0.27-0.57 +/- 0.27, P < .01) as a result of a reduced ICT and isovolumic relaxation time and a prolonged LV ejection time associated with an increased LV ejection fraction. Methox increased IMP (0.72 +/- 0.26-1.31 +/- 0.43, P < .001) because of an increased ICT and isovolumic relaxation time and a reduced LV ejection time associated with a reduced LV ejection fraction. Forward stepwise regression indicated that both LV systolic pressure ( P = .0006) and LV ejection fraction ( P = .0222) were independent predictors of IMP.

CONCLUSION

IMP is afterload dependent in the normal LV. IMP is afterload dependent with acute and chronic LV dysfunction by influencing the isovolumic indices and LV ejection time in opposite directions. Further systematic evaluation of IMP is needed if this index is to be useful as a prognostic indicator.