|Year : 2005 | Volume
| Issue : 3 | Page : 98-103
Myocardial performance index evaluated with tissue doppler echocardiography at early, intermediate and late phase of acute myocardial infarction
Federico Cacciapuoti1, Raffaele Marfella2, Eleonora Manfredi1, Fulvio Cacciapuoti1, Giuseppe Caruso3, Giovanna Nittolo1, Paolo Capogrosso4
1 Laboratory of Ecochardiography, Second University of Naples- San Gennaro. Hospital-Naples, Italy
2 Cardiovascular Research Center-Second University of Naples- Naples, Italy
3 XII Medical Division. A.O.R.N. . A. Cardarelli. Naples, Italy
4 Cardiology Division-.San Gennaro. Hospital-Naples, Italy
|Date of Web Publication||18-Jun-2010|
Cattedra di Medicina Interna, Facoltą di Medicina e Chirurgia, Seconda Universitą di Napoli, Piazza L. Miraglia, 2 80138-Naples
Source of Support: None, Conflict of Interest: None
| Abstract|| |
In this study, ejection fraction% (EF%) and myocardial performance index (MPI) were recorded in 67 survivors at early, intermediate and late phase of acute myocardial infarction (AMI) .EF% was echocardiographically obtained by the Simpson's method; MPI was calculated using Tissue Doppler Echocardiography (TDE) derived from isovolumetric contraction time (ICT); isovolumetric relaxation time (IRT) and ejection time (ET). Results were compared with those obtained in 70 controls matched for age and sex.
At hospital discharge (early evaluation), EF% was < 50% with significant increase in MPI in respect to the healthy controls (increase in ICT, significant reduction in ET and IRT was unchanged). Six months later (intermediate evaluation), EF% still resulted in < 50%, MPI was slightly reduced with further increase in ICT and IRT in comparison to the early evaluation, and slight reduction in ET. Finally, one year later (late evaluation), in spite of increase in EF>50%, MPI was still increased, with slight rise in ICT, almost normalization in ET, but more evident increase in IRT.
The outcomes of MPI demonstrate that in post-AMI patients, late prevalent diastolic ventricular dysfunction occurs following an early systolic dysfunction. In this study, EF% appears to be less sensitive than MPI in defining late post-AMI left ventricular dysfunction. Finally, TDE seems to be more sensitive than conventional Doppler method in measuring MPI.
Keywords: acute myocardial infarction, myocardial performance index; tissue Doppler echocardiography; isovolumetric contraction time; isovolumetric relaxation time ejection time; ejection fraction
|How to cite this article:|
Cacciapuoti F, Marfella R, Manfredi E, Cacciapuoti F, Caruso G, Nittolo G, Capogrosso P. Myocardial performance index evaluated with tissue doppler echocardiography at early, intermediate and late phase of acute myocardial infarction. Heart Views 2005;6:98-103
|How to cite this URL:|
Cacciapuoti F, Marfella R, Manfredi E, Cacciapuoti F, Caruso G, Nittolo G, Capogrosso P. Myocardial performance index evaluated with tissue doppler echocardiography at early, intermediate and late phase of acute myocardial infarction. Heart Views [serial online] 2005 [cited 2020 Aug 10];6:98-103. Available from: http://www.heartviews.org/text.asp?2005/6/3/98/64020
| Introduction|| |
After Acute Myocardial Infarction (AMI), left ventricular function is impaired. Ventricular dysfunction may be non-invasively evaluated by Myocardial Performance Index (MPI), which was first measured by Tei in 1995 using the Doppler method , . Many authors demonstrated that the Tei index is able to evaluate some important hemodynamic indices, such as ejection fraction, peak + dp/dt and peak - dp/dt, both in healthy and in patients with cardiac diseases , . In addition, it has been found to have prognostic value in the post-AMI period ,,, . Recently, Tissue Doppler Echocardiography (TDE) has been introduced to measure MPI. Unlike conventional Doppler, TDE is able to measure the interval between end and onset of mitral flow and the ejection time simultaneously , .
In this study, we tested if MPI and the main time intervals detected with TDE are useful to evaluate early, intermediate and late left ventricualar function in survivors of AMI in comparison to the healthy controls.
| Methods|| |
The study group comprised 124 consecutive patients (91 M and 33 F), age ranged from 42 to 71 years, and all survivors of anterior AMI. Criteria for inclusion in the study are: a history of typical chest pain; Q-wave in V1 - V4 and/or electrocardiographic ischemic changes of ST-T in at least two contiguous ECG-leads; an increase in troponin or a transient rise in creatinine kinase twice above to the normal limit. Exclusion criteria were: atrial fibrillation; left or right branch block; sinus tachycardia >100 beats/min; elevated values of arterial pressure (>140/80 mmHg.). During hospital-recovery, all patients received the following medical therapy: aspirin and/or heparin (100%); angiotensin-converting enzyme inhibitors (100%); long-acting nitrates (95%); diuretics (2%). Same drugs, except diuretics, were provided during one year after AMI.
At hospital discarge, all patients underwent 2-dimensional echocardiography, using a commercially available ultrasound machine (A.T.L. - 5000 H.D.I.) with a 2.5 MHz transducer. Ejection fraction (EF%) was obtained by the Simpson's biplane method  . Pulsed-wave TDE was performed by activating the tissue Doppler function in the same echocardiographic machine. Images were acquired using a variable frequency phased-array transducer (2.0 to 4.0 MHz). The filter settings were kept low, and gains were adjusted to the minimal optimal level to minimize noise and eliminate the signals produced by the transmitral flow. A 1.7 mm sample volume was used. It was placed at the lateral site of the mitral annulus in the long-axis apical-four chambers approach. The pulsed-wave TDE tracings were recorded at a sweep speed of 100 mm/sec. and three of them were used for calculation. The interval a, from the R wave to the onset of diastolic velocity, was equal to the sum of isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT) and ejection time (ET) defined as b. MPI was calculated as (a-b)/b. [Figure 1].
IRT was calculated, by subtracting the interval d (between the R wave and the cessation of systolic velocity) from the interval c (between the R wave and the onset of diastolic velocity). ICT was calculated by subtracting IRT from (a-b) [Figure 1]  .
MPI, ICT, IRT and ET were also evaluated in 87 healthy individual (55 M, 32 F, age ranging from 52 to 66 yrs), and employed as controls. These subjects were selected among the individuals with no cardiovascular complaints, and no evidence of significant cardiovascular disease, as assessed by chest X-ray, electrocardiography, and echocardiography. The controls underwent two-dimensional and TDE evaluations repeated respectively after six months and one year as in the group of patients with AMI.
To obtain the reference values, means SD of ICT, IRT, ET, MPI with TDE and EF were evaluated in control subjects. These Doppler parameters were obtained at hospital discharge (early phase), at 6 and 12 months in patients with AMI. The means reported during these three periods were compared with those obtained in normal subjects using with ANOVA, employing the Wilcoxon test for paired data. A p value of <0.05 was considered significant.
| Results|| |
109 of the 124 patients with AMI examined at hospital discarge were re-evaluated at 6 and 12 months after their discharge from hospital for AMI. 7 patients expired and another 8 patients left the study. [Table 1] shows the main clinical and hemodynamic characteristics of all enrolled patients. The mean values -SD of ICT, IRT, ET, MPI and EF obtained in control subjects are illustrated in [Table 2]: ICT = 35 - 5 ms; IRT = 75 - 7 ms; the mean value of ET was of 310 - 12 ms. MPI showed a mean of 0.35 - 0.04 and EF = 0.65 - 0.07. [Table 3] shows the echocardiographic results obtained in 109 patients with AMI at hospital discarge, after six months, and one year. ICT increased (65 - 7 ms) in comparison to the normal values, but progressively decreased after 6 months (60 - 5 ms.) and one year (45 - 4 ms) .The differences among the normal values and these records were significant (p < 0.05). On the contrary, IRT in the early phase was unchanged as compared to the controls (78 - 4 ms.), but progressively increased (80 - 6 after six months and 95 - 7 ms, after one year). There was also a significant difference between the reference and the means obtained in AMI-patients (p < 0.001). ET was reduced during early phase (275 - 13 ms) when compared with the normal values, but showed a progressive rise (290 - 11 ms at six months, and 305 - 14 ms at one year). The differences were significant (p < 0.05). As a consequence, MPI increased at early (0.52 - 0.03), intermediate (0.49 - 0.05) and late evaluations (0.45 - 0.02) when compared to the normal values (p < 0.001) Finally, EF increased from 0.35 - 0.03 (early) to 0.47 - 0.05 (6 months) until 0.52 - 0.02 (one year). The differences in MPI measurements between the normal controls and the AMI patients during the early phase were significant (p < 0.001)
| Discussion|| |
Conventionally measured MPI is a useful and non-invasive index to define left ventricular "global" function  . Its calculation, together with the evaluations of ICT, IRT and ET, allows identification of the phase of cardiac cycle that is prevalently involved in many cardiovascular diseases ,,,,,, .
In this report, we calculated MPI using TDE method. The major advantage of TDE in defining MPI is its ability to simultaneously measure both the diastolic and systolic phases in respect to the conventional Doppler , . Its increased sensitivity also derives from the measurements of direct flows' displacements rather the ventricular walls' movements. In addition, it has been shown to be independent of heart rate and blood pressure  . Thus, TDE reduces the inaccuracy dependent on the heart fluctuation and on the delayed movements of ventricular walls in respect to that one of blood flow. The increased MPI by TDE at the infarction site is an expression of myocardial damage after an AMI. However, MPI results also increased at non-infarction site when it is compared with its value in healthy subjects. It is difficult to explain this phenomenon. Probably, the spirally oriented myocardial fibers causing the shortening of the left ventricle along its long axis might have some action beyond the infarction area. For this reason, even if the left walls' derangement only interests the AMI zone, MPI results are prolonged too. MPI by TDE seems to have the advantage of assessing both regional and global left ventricular function.
In the present study, we measured MPI with TDE from the lateral site of mitral annulus in accordance with Harada et al., who referred that the lateral site of the tricuspid annulus is the more reliable in the evaluation of the right ventricular function  . Tekten et al also found that the better approach is the lateral site of the mitral annulus. A possible explanation of this finding is that the values of MPI obtained by recording from the opposite site (septal site) of mitral annulus may be affected by the function of right ventricle  .
The results achieved showed an early increase in MPI as evidenced by a clear prolongation in ICT, slight rise in IRT and reduction in ET. According to EF, these findings demonstrate an early LV systolic dysfunction, which confirms the pictures already recorded using conventional Doppler method  and are in accordance with some studies previously obtained using the polycardiography  . The echocardiographic parameters recorded six months later, testify to an attenuation of systolic dysfunction, demonstrated by a decrease in ICT and increase in ET, whereas IRT was unchanged. As a consequence, MPI also decreased. The modest increase in EF% in respect to the early record, further confirms the improvement of post AMI systolic dysfunction. A prevalent diastolic LV dysfunction is evident with the results performed one year later. In fact, whereas ICT further decreased, ET increased, coming again towards to the normal values. IRT plainly increased. The late outcome of MPI indicates a progressive normalization of LV function. This is consistent with the results reported by Szymanskj et al  and Poulsen et al  .
Thus, based on changes in ICT and ET, left systolic dysfunction appears to predominate in the early phase of AMI. Successively, a late development of impaired relaxation occurs, indicating a prevalent diastolic dysfunction resulting from the development of compensatory hypertrophy during the LV remodeling process , . The Tei-index appears more sensitive than EF. The disagreement between MPI and EF probably is due to the non-uniform left ventricular geometry and contractility after AMI  . In fact, because the ventricular contractility is abnormal, EF measured using the biplane Simpson method probably appears less sensitive than MPI evaluated with TDE. This conclusion is in accordance with the results reported by Kouris et al. who observed abnormal values of the Tei index in patients with coronary artery disease and apparently normal systolic and diastolic function. Finally, for the previous considerations about the major sensitivity of TDE method, it's possible to affirm that this one is more sensitive than the conventional pulsed-Doppler in evaluating all parameters of LV function.
| Limitations of the study and conclusive remarks|| |
The number of enrolled patients represents the main limitation of this study. This condition depends on the necessity to exclude the patients receiving b-blocker drugs. Another limitation was that only patients with signs of anterior-AMI were enrolled in the study. In addition, coronary angiography was not performed in all patients. In spite of these limitations, the measurements of MPI, ICT, IRT and ET with TDE appear able to non-invasively identify the prevalent type of early, intermediate and late LV dysfunction after AMI. Moreover, our results are in agreement with previous studies demonstrating that MPI by TDE is more useful than EF to better identify post-AMI LV dysfunction. Our study shows a more evident sensitivity in MPI, probably dependent on the segmental systolic post-necrotic LV dysfunction and on the late appearance of LV post-remodeling. Conclusively, TDE seems to be more sensitive than the conventional Doppler method to evaluate the left ventricular function.
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[Table 1], [Table 2], [Table 3]