European Journal of Cardiovascular Medicine

The acute coronary syndrome is a common presentation of ischemic heart disease.¹ It is also the most significant cause of death in developed and developing countries.² cardiovascular diseases (CVD) are a worldwide health epidemic³ and a substantial barrier to sustainable human development.⁴ coronary artery disease (CAD) is the leading cause of mortality worldwide. The prevalence of CAD in the Indian Population is 11% .⁵

Assessment of LV function is an essential test for any patient with acute coronary syndrome. Several methods are available for assessing LV function; Echocardiography is the most commonly and readily available method for assessing LV function. De-arrangement in LV function affects systolic function, diastolic function, or both. Echocardiography is appropriate for studying systolic function, and Doppler function provides a noninvasive technique for assessing diastolic function. These measurements change with the placement of the sample volume, heart rate, rhythm and quality of the image and are load-dependent.

The Tei index / Myocardial Performance Index (MPI) is a ratio of systolic and diastolic time intervals that can be obtained from Doppler echocardiography. The timing ratio, derived from the sum of isovolumetric contraction time and isovolumetric relaxation time divided by the overall ejection time, has been well validated in assessing overall global myocardial performance in pediatric and adult populations.^6,7 It is more indicative of net cardiac function than diastolic or systolic function alone.^8,9,10 Therefore, this study aims to evaluate whether the myocardial performance index (MPI) measured by the conventional Doppler method relates to the severity of coronary artery disease in ACS.

MPI is derived from Doppler echocardiography and is calculated using the formula:

Where:

• Isovolumic Contraction Time (IVCT): Time interval from the closure of the mitral valve and the opening of the aortic valve.
• Isovolumic Relaxation Time (IVRT): Time interval from the closure of the aortic valve and the opening of the mitral valve.
• Ejection Time (ET): Duration of the ventricular ejection phase

In this study The Tei index (non-invasive) and Angiographic severity (invasive) of lesion as assessed by Gensini scoring was correlated. MPI can be measured non-invasively and simply; an experienced echocardiographer is not necessary, nor does it significantly increase the amount of time needed for the test. It is also cost-effective, appropriate for follow-up studies, and independent of age, blood pressure, and heart rate. It also seems to have excellent predictive value in a variety of clinical contexts.

Study place: Department of Cardiology, Shri B.M. Patil Medical College Hospital and Research Centre, Vijayapura.

Study Population: Patients admitted with acute coronary syndrome (STEMI, NSTEMI and UNSTABLE ANGINA)

Study Design: Hospital based Prospective Analytical Study. (Cross Sectional Study)

 Sample Size: 155 patients admitted with acute coronary syndrome.

INCLUSION CRITERIA: Patients admitted with acute coronary syndrome (STEMI, NSTEMI and UNSTABLE ANGINA) Patients who were admitted to CCU, with first episode of acute coronary syndrome were included.

EXCLUSION CRITERIA FOR CASES: Patients with 1. Significant Valvular heart disease 2. Pericardial disease 3. Cardiomyopathies 4. Significant tachy or bradyarrhythmias. 5. Permanent /Temporary pacemaker insertion 6. Past History of old myocardial infarction and PTCA or CABG

COLLECTION OF DATA:

Institutional review board approval was sought for the study. Informed   consent was taken from all patients before the procedure.

• The entire patients who are included in the study are evaluated based on proforma, detailed history with a particular focus on chest pain duration, and risk factors were obtained.
• Patients were evaluated with a thorough echocardiographic analysis within 48 hours of admission. Their treatment history and in-hospital complications were noted.
• TWO –dimensional and M-mode measurements are obtained with patients in the left lateral position using phased array system equipped with pulse wave Doppler imaging technology.
• Parasternal long and short axis, as well as apical four- and two-chamber views, are used to evaluate the functions of the left ventricle and the heart valves.
• The left ventricle's LV dimension and fractional shortening (FS) are calculated using Teicholtz formula.
• The ejection fraction is obtained by modified Simpson's method.
• Pulse-wave Doppler measurements of mitral inflow are obtained with the transducer on the four-chamber view with a 1-2 mm Doppler sample volume placed between the tips of the mitral leaflets during diastole.
• The left ventricular outflow velocity curve is recorded from the apical long-axis view/apical five-chamber view with the sample volume positioned just below the aortic valve.
• Doppler velocities and time intervals are measured from mitral inflow and left ventricular outflow recordings as described by Tei et al.¹¹ Isovolumetric relaxation time (IVRT) is the time interval from cessation of left ventricular outflow to onset of mitral inflow, ejection time (ET or MPI Measurement B) was the time interval from the onset and cessation of left ventricular outflow, and mitral early diastolic (E) flow deceleration time (DT) was the time interval between the peak E velocity and the end of the early diastolic flow. The total systolic time interval was measured from the cessation of one mitral flow to the beginning of the following mitral inflow (MPI Measurement A). Isovolumetric contracting time (ICT) is calculated by subtracting ET and IVRT from the total systolic time interval. MPI was calculated using the formula MPI= MPI A- MPI B/MPI B or (IVRT+ICT)/ET.
• Coronary angiography is performed in all subjects, and the severity of coronary artery lesion was determined according to Gensini score calculations were done.

During the study period from 18thDecember 2022 to 31st May 2024 patients who fulfilled the inclusion and exclusion criteria were included in the study.The mean MPI was 0.56 with standard deviation of 0.16 and median of 0.54 . The minimum MPI in the study was 0.30 and the maximum was 0.90.ROC curve was drawn. Area under the curve was calculated. Sensitivity and specificity were calculated.The ROC analysis indicates that the classifier has an outstanding performance, with an AUC of 0.998. This high AUC value, close to 1, signifies excellent discriminative ability, meaning the model can almost perfectly distinguish between positive and negative classes. The standard error of 0.002 denotes high precision in the AUC estimate, while the p-value of <0.001 shows that the model's performance is significantly better than random guessing. Additionally, the narrow 95% confidence interval of 0.993 to 1.000 further confirms the reliability and accuracy of the AUC estimate, making this classifier highly effective for the binary classification task.

Figure 1 – ROC CURVE TEI INDEX VS GENSINI (LOW VS HIGH)

TEI INDEX VS GENSINI (LOW VS HIGH)

Table 1 TEI INDEX VS GENSINI (Low vs High) – AREA UNDER THE CURVE

From the ROC curves comparing high vs. low MPI values, an MPI threshold of 0.78 demonstrated a sensitivity of 83% and a specificity of 100%. The Positive Predictive Value (PPV) was 100%, and the Negative Predictive Value (NPV) was 98.33%. This resulted in a diagnostic accuracy of 98.46%.

Assessing systolic and diastolic function through non-invasive methods is crucial for risk stratification and prognosis in patients with acute coronary syndrome (ACS). While ejection fraction (EF), determined by routine 2D echocardiography, is widely used to evaluate left ventricular function, it primarily focuses on systolic function and has several limitations. These include the impact of geometric assumptions and errors from tangential tomographic planes, which complicate the evaluation of left ventricular volumes.

The association between the Gensini Score (GS) and the Myocardial Performance Index (MPI) was investigated using correlation analysis. A robust positive connection was seen between MPI and GS .

During ACS, both systolic and diastolic functions are often impaired, making a combined measure of left ventricular performance potentially more informative than assessing systolic or diastolic function alone. The Myocardial Performance Index (MPI), or Tei index, evaluates both systolic and diastolic function and is calculated using the formula (IVCT + IVRT) / ET. MPI has key advantages: it is independent of arterial pressure, heart rate, ventricular geometry, and atrioventricular valve regurgitation when patients are supine. Preload changes do not significantly affect the Tei index, though age, rhythm and conduction disturbances, and changes in loading can impact Doppler signals of transmitral flow, commonly used to study diastolic function. In patients with acute myocardial infarction, MPI values are notably higher compared to healthy controls, reflecting increased IVCT and IVRT, and decreased ET during the acute phase. This results in a higher MPI, which correlates with both mortality and morbidity.Several studies have demonstrated elevated MPI in ACS patients, but few have examined the relationship between MPI and severity of coronary involvement as measured by tools like the Gensini scores. Our study is the first to explore the relationship between MPI and Gensini scores in ACS patients, including STEMI, NSTEMI, and unstable angina.

LIMITATIONS OF THE STUDY - This study was conducted at a single center. Its results require further validation through a large-scale, multicenter, randomized prospective study.

The myocardial performance index (MPI) findings will help us diagnose coronary artery disease non-invasively in an appropriately selected patient for planning further management

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