Nasir Rahman  ( Department of Cardiology, Aga Khan University, Karachi. )
Khawar Abbas Kazmi  ( Department of Cardiology, Aga Khan University, Karachi. )
Muniza Yousaf  ( Department of Cardiology, Aga Khan University, Karachi. )

Objective: To investigate association between the Tei index and cardiac complications of ST elevation of Myocardial Infarction.
Patients and Methods: A total of a 202 adult consecutive patients with first ST elevation MI (STEMI) were studied. Tei index was obtained as: (a _ b)/b, where "a" is the interval between the cessation and onset of mitral flow and "b" is the ejection time of aortic flow measured with the help of pulsed Doppler echocardiography. Subsequent complications, included Death, Congestive Heart Failure (CHF), Cardiogenic shock, Atrial Flutter/ Atrial Fibrillation, Sustained ventricular tachycardia, Advanced Atrio- Ventricular Clock (AV Block), Myocardial Infarction (MI), Readmission (due to any cardiac cause) and Revascuralarization during the 30 days after the onset of Acute STEMI were prospectively evaluated and compared with the initial Tei index at admission.
Results: Complications were noted in 60% of the patients with acute STEMI. The Tei index was significantly increased for patients with complications compared with those without them (0.66 ± 0.13 vs. 0.30 ± 0.10, P < .0001). When Tei index > 0.40 was used for the criteria, the sensitivity, specificity, and overall accuracy to predict subsequent complications were 86%, 82%, and 83%, respectively.
Conclusion: Tei index allows approximate but quick and practical noninvasive prediction of complications in patients with STEMI (JPMA 59:75; 2009).

Ventricular impairment induced by a recent MI is responsible for an increase in ventricular volumes and reduction of myocardial kinetics, with an increase of wall motion score index (WMSI). It can also induce changes in ventricular contraction and relaxation times, with derangement in left ventricular (LV) function.^1-2 To evaluate this impairment, Tei et al proposed a new Doppler index, so called index of myocardial performance (IMP), to define ventricular function.³ This proposed Tei index is defined as the sum of isovolumic contraction time (ICT) and isovolumic relaxation time (IRT) divided by ejection time (ET).^4-6

This noninvasive Echocardiographic index of ventricular function is of clinical significance in diagnosing risk of heart diseases.⁷ Tei index is easily obtainable and has been clinically useful in assessing global ventricular function in both adults and  children.^6-7 The index combines systolic and diastolic time intervals and independent of heart rate and ventricular geometry.⁸

Tei index also allows noninvasive prediction of the prognosis of patients with cardiac amyloidosis, dilated cardiomyopathy, and primary pulmonary hypertension.^9-11 This also allows prediction of the development of CHF in patients with acute MI.^3,12-14

However, the relationship between the Tei index and various complications of acute ST Elevation Myocardial Infarction (STEMI) has not been fully investigated in Pakistan.

Therefore, the purpose of this study was to investigate the relation between Tei index and cardiac complications in STEMI.

This was a prospective study done at the department of cardiology, The Aga Khan University Hospital, Karachi, Pakistan. This study was carried out over a period of one year after the acceptance of Synopsis, i.e. from June 2006 to June 2007.  Two hundred and two patients with acute STEMI were selected without gender discrimination. The criteria for inclusion in the study were: age more than or equal to 30 years, all patients with acute STEMI, according to ACC/AHA criteria (Typical rise and gradual fall (troponin) or more rapid rise and fall (CKMB) of biomedical markers with at least one of the following: Symptoms, Development of pathologic Q waves on ECG, ECG changes suggestive of ischemia, Coronary Artery intervention and Pathological findings of acute MI),  adequate 2D echo images along with adequate doppler signals to accurately assess the Echocardiographic parameters.

The criteria for exclusion from the study were: significant mitral regurgitation (more than mild), significant Aortic Stenosis (more than mild), inadequate 2D echo images with inadequate Doppler signals and congenital heart disease.

The study was approved by ethical review committee of Aga Khan University Hospital, Karachi, Pakistan. Written informed consent was obtained from all the patients.

Patients were divided in two groups with regard to tei index of < 0.4 and > 0.4. A predefined questionnaire containing demographic data, clinical variables and echocardiographic measurements were filled.

Two-dimensional, pulsed Doppler and colour flow Doppler echocardiography examinations were performed by single institutional sonographer, immediately after patient's arrival in the coronary care unit. The cardiac ultrasonographic unit, Sonos 5500 Philips Echo Machine, with a 2.5-MHz transducer was used. All two-dimensional echocardiography data were stored digitally on the DVD/CD, and a standard videocassette recorder was used to store pulsed Doppler data measurements on high quality videotape for later analysis. Left ventricular volumes and ejection fractions were measured with Simpson's biplane disk plane method.¹⁵ Left ventricular volumes were corrected for body surface area and a mean of three measurements were used. The mitral inflow velocity pattern was recorded with the pulsed wave Doppler sample volume positioned between the tips of the mitral leaflets. The LV outflow pattern was recorded from the apical 5-chamber view with the pulsed wave Doppler sample volume positioned just below the aortic valve. Each Doppler profile was analyzed by a digital tracing, and Doppler measurements were calculated from an average of five consecutive cardiac cycles.

Doppler time intervals were measured from mitral inflow and LV outflow velocity-time intervals. The interval "a" from the cessation to the onset of mitral inflow was equal to the sum of ICT, ET, and IRT. Left ventricular ET "b" was the duration of LV outflow velocity profile. Thus the sum of ICT and IRT was obtained by subtracting "b" from "a".

The index of combined LV systolic and diastolic function (the sum of ICT and IRT divided by ET) was calculated as (a - b) / b.3 (Figure). In addition, patient's heart rate and Blood Pressure were also taken at the time of admission.

Complications with acute MI were divided in two groups. Cardiac death, cardiogenic shock and STEMI were major outcome complications. Need for revascularization, readmission due to cardiac reasons, CHF, cardiac arrhythmias and advanced atrioventricular block were the minor outcome complications. All patients were prospectively evaluated for 30 days after the onset and compared with the initial cardiac function evaluated with Doppler echocardiography at the time of admission in the acute phase, for major outcome complications. For minor outcome complications, patients were followed during hospital stay. Follow up was done by chart review, where required. Any cardiac complications as per definition were recorded on a predefined Performa. Definitions [(f1)] of the complications are summarized in (Table 1).

All the Echocardiographic measurements were done by the single observer, who was unaware of the clinical and hemodynamic information, to avoid technical errors. Data was obtained from three consecutive cardiac cycles and was averaged.

Results were expressed as the means. Variables were compared with the Tei Index by Chi Square Test. Presence of Cardiac complications in patients with acute STEMI were presented by frequency distribution. Fisher Exact Test was applied to test an association between tei index (categorized as < 0.4 and > 0.4) and development of any one of the end points after STEMI. A P < 0.05 was considered statistically significant. Tie index was also measured as a continuous variable.

Total of 202 patients having STEMI were enrolled in the study, out of which 157 were male patients and 44 were female. Out of these patients 24% were hypertensive, 19 % diabetic, 32 % had dyslipidemia and 13 % had renal failure with average tei index of 0.49, 0.54, 0.48 and 0.47 respectively. Out of 202 patients, 121 (60%) developed complications. The absolute Tei Index values with Odd and Hazard ratio in different cardiac complications is shown in Table 2.

 Relations between Complications and Functional Indices LV EF were significantly reduced (P < .001). The Tei index was also significantly increased for patients with complications compared with those without i.e. The overlap [(t2)] [(t2)] of the Tei index between the two groups was relatively small (Table 2). Sensitivity and Specificity of Tie index and EF was compared and shown in Table 3. Tei index >0.40 and EF <45% were found as significant predictors of subsequent complications, but this was found that tei index of > 0.4 has better sensitivity and specificity in predicting cardiac complications after acute STEMI. About 22% of the patients with normal EF, showed abnormal Tie Index. Out of these 22%, 97% of the patients developed cardiac complications. [(t3)]

 Acute MI is characterized by variable degrees of LV systolic and diastolic dysfunction, which have both been reported to have independent prognostic value.^16-20 It is hypothesized that a measure of combined systolic and diastolic myocardial function is a better predictor of global LV function and outcome in patients with acute STEMI. Abnormalities and changes in LV systolic and diastolic time intervals have been described but less thoroughly studied in relation to outcome. In the present study, the Tei index, which combines systolic and diastolic time intervals, was compared with conventional echocardiographic variable (EF) and was correlated with outcome in patients with acute ST elevation MI. The isovolumetric contraction time was significantly prolonged (100msec) and ejection time shortened (150msec) in patients with MI. These alterations in time intervals resulted in a significant increase in the value of the Tei index in patients with MI.

An abnormal index (>0.40) was found in 90.6 % of the patients with MI, whereas an ejection fraction (<50%) was present in 98%. The index was significantly more sensitive than the ejection fraction in the prediction of LV dysfunction based on the clinical development of cardiac complications. The index was significantly higher and the ejection fraction lower in patients with cardiac complications than in those without heart failure. Shortening of the ejection time and prolongation of the isovolumetric contraction time has previously been demonstrated in patients with cardiac complications, consistent with the findings in this study.²¹ Ejection fraction as measured by 2-dimensional echocardiography has a good interest correlation when the LV geometry is uniform. However, if the ventricular chamber is irregular, as is typical after infarction, the true volume by echocardiography is less accurate.²¹ Thus measurement of ejection fraction after MI may be less reliable by the biplane Simpson method because it depends on ventricular geometry, which is abnormal.¹⁵ In contrast, the Tei index does not depend on ventricular geometry and incorporates diastolic function in addition to systolic function. Thus the index is expected to be more sensitive than simple measurement of the systolic ejection fraction, which was confirmed in the present study according to sensitivity and specificity results. Furthermore, the index is easily obtained within a few minutes and therefore does not substantially prolong the acquisition time of the echocardiographic examination.

A prediction of complications with STEMI from echocardiographic functional indices has been investigated. Fleischmann et al found that WMSI, Left Ventricular EF, and restrictive LV filling enable the prediction of complications.²² Møller et al have differentiated normal from pseudo normal/restrictive mitral flow and shown that pseudo normal or restrictive mitral flow pattern enables the prediction of complications after a first acute MI²³ The use of the Tei index has been demonstrated in relation to patient prognosis, haemodynamic condition, right ventricular function, evaluation of restenosis after percutaneous transluminal coronary angioplasty, and other conditions.²⁴ However, study confirmed that Tei index which measures both systolic and diastolic dysfunction can predict cardiac complications more accurately.

Possible limitations in this study can be: Mitral and aortic flow velocity was recorded separately, with potential measurement variability. Although there was significant correlation between the Tei index and cardiac complications for patients with STEMI, the same correlation was not significant for patients with abnormal right ventricular function, abnormal atrioventricular conduction, in addition to LV function, can be significant determinants of hemodynamics in patients with these patients, which may result in the lack of significant correlation.

Further studies are needed to assess the long-term predictive value of the Tei index and the value of the Tei index during the post-MI remodeling process.

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