Introduction

Coronary artery disease (CAD) is one of the leading causes of morbidity and mortality in the world and has neared its epidemic proportions. India has a similar scenario. Indian studies have revealed that cardiovascular diseases (CVDs) cause approximately 40% of deaths in urban areas and 30% of deaths in rural areas in India.1

Early detection of CAD among people with or without symptoms is the main task to reduce morbidity and mortality. There are various invasive and noninvasive methods to detect CAD among people with symptoms. Always invasive methods have their advantage and disadvantages, so noninvasive tests are low-cost modalities of CAD detection and are the need of the hour. Of these noninvasive modalities, various methods are used such as electrocardiogram (ECG), echocardiography (echo), CT, magnetic resonance imaging (MRI), and nuclear imaging.

Based on the concept that diastolic abnormalities occur earlier than symptoms, ECG changes, and systolic dysfunction during myocardial ischemia, diastolic stress test should identify ischemia earlier than another type of stress test methods.2 The authors want to study the usefulness of applying stress echo with treadmill test (TMT) for detection of CAD patients.

Aims and Objectives

The aim of this article is to measure changes in tissue Doppler imaging (TDI) parameters with exercise stress test in males and females and compare with the presence and severity of CAD on a coronary angiogram (CAG).

Material and Methods

Results

In 51 study population, the mean age was 53.9 ± 10.2 years with a male:female::1.93:1. After CAG, 41 (80.4%) patients had CAD and in 10 (19.6%) patients no-CAD. Comparison of demographic features of CAD and no-CAD groups is depicted in Table 1.

Presence of dyslipidemia and family history of CAD showed a tendency for the presence of CAD, but not the age, smoking, HTN, or diabetes. Gender distribution of the two groups is depicted in Table 2 and Fig. 1.

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Fig. 1 Gender distribution among study groups.

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Fig. 1 Gender distribution among study groups.

Comparison of demographic and laboratory parameters between the males and females showed that except for smoking, which was more in males, were comparable. CAD was more in males than females, which were statistically significant represented in Table 3.

A 2D echo is done before starting the TMT and at the first minute after TMT. Fresh WMA (wall motion abnormalities) were noted. All pulse wave and tissue Doppler-derived parameters, before and after TMT, were mentioned in Table 4. E, A velocity, E/A ratio, and DT on pulse wave Doppler before starting the TMT and also after TMT were same in both the groups (CAD and no-CAD).

However, tissue Doppler velocities were different in CAD and no-CAD patients in both at rest and after TMT Table 5.

Tissue Doppler velocities, S′ septal, E′ septal, A′ septal, S′ lateral, E′ lateral, S′ inferior, A′ inferior ratios, E/E′ septal, E/A′ septal, E/E′ lateral, E′/A lateral, E/E′ inferior, and E′/A′ inferior were significantly different even at basal echo time, which were more significant during exercise (Table 6). A′ lateral and E′ inferior were not different at basal and after stress in between the groups.

The tissue Doppler velocities ratios during TMT, but not the velocities as such, were helpful in detecting the severity of CAD (Table 7).

Treadmill test positive had 56% sensitivity for detection of CAD. Along with stress echo its sensitivity was 71%. By including WMA with other parameters, sensitivity for detection of CAD was 75%.

Even though univariate analysis showed many TDI parameters were useful in detection and severity of CAD, multivariate regression analysis did not indicate that. Multivariate regression analysis showed that positive TMT had a tendency for detection of CAD, whereas the presence of WMA after exercise was determinant for CAD (Table 8).

Discussion

Tissue Doppler examination during the stress may detect the diastolic and systolic dysfunctions due to stress-induced ischemia. Evidence has been piling on the importance of physiological assessment rather than morphologic assessment for CAD detection. Regional stunning due to myocardial ischemia can be diagnosed by tissue Doppler measurements. The myocardial ischemia can also be detected by measurement of reduced transmyocardial velocity. Regional diastolic dysfunction can be detected and measured by TDI, so TDI parameters such as systolic velocity (S′), early diastolic velocity (E′), and late diastolic velocity (A′) can reflect changes during ischemia. Changes documented during ischemia are reduced and delayed peak systolic and diastolic velocities, reduced myocardial velocity gradients, and diastolic dysfunction, which is demonstrated in various studies. Because diastolic dysfunction may persist after recovery of normal systolic function, after short time of coronary occlusion by balloon during coronary angioplasty,3 in post treadmill exercise stress, echo can identify diastolic dysfunction immediately after cessation of exercise.

Baseline TDI systolic velocity (S′) was lower in CAD patients than without CAD (6.25 vs. 8.11 cm/s) as shown in other studies. This study had lower E′ and A′ in CAD patients. However, E/E′ slightly higher than normal value in CAD group (9.37 vs. 8.37). Tissue Doppler systolic velocity for different segments in baseline mainly basal septal, basal lateral, and basal inferior are 8.11, 10.47, and 8.75 cm/s, respectively. There were significant changes of tissue Doppler echo parameters in patients with CAD after stress test. The systolic velocity did not increase after stress test in CAD patients.

Hoffmann et al4 have studied 82 patients with suspected angina pectoris, no previous cardiac history, and normal ejection fraction. All the patients were examined with color TDI before CAG, at baseline. The baseline TDI parameters in patients with and without CAD compared with this study (Table 9).

As shown above, there is a statistically significant difference in average S′ and average E/E′ between patients with and without CAD whereas difference in average E′ and average A′ is statistically insignificant. In this study in the CAD group, the average S′, average E′, and average A′ along with the average E/E′ were significantly lower values than in no-CAD group, which were statistically significant. The increase in E/E′ ratio did not correlate with SVD but well with DVD and TVD.

In the study by Nitta et al,5 the hypothesis that, in patients with nonobstructive CAD documented by CAG, the index of LV diastolic function from ECG-gated SPECT is useful in detecting myocardial ischemia, was tested. Multivariate logistic regression analysis showed that peak filling rate (PFR) at redistribution was an independent predictor of the presence of myocardial ischemia in patients with nonobstructive CAD, by angiogram (odds ratio: 0.15, 95% confidence interval: 0.04–0.51, p = 0.002). Summed difference scores (SDS) in patients with myocardial ischemia and those without were 3.5 ± 1.8 and 0.4 ± 0.5, respectively (p < 0.001). PFR after stress was significantly lower in patients with myocardial ischemia than in those without. Lower PFRs after stress and at redistribution were inversely correlated with SDS. PFR was correlated with mitral annular velocity on tissue Doppler echo, which is widely used as an index of LV diastolic function in the clinical setting.

In the MYDISE6 (Myocardial Doppler in Stress Echocardiography) study, Mädler et., al have studied tissue Doppler digital data during dobutamine stress in 289 patients, and measured myocardial responses of 11 LV segments, by offline analysis. Ninety-two normal patients were compared with 48 patients with coronary disease, in a prospective series of 149 patients referred with chest pain. Optimal diagnostic accuracy was achieved by logistic regression models, using systolic velocities at maximal stress in seven myocardial segments, adjusting for independent correlations directly with heart rate and inversely with age and female gender (all p < 0.001). They have demonstrated that CAD can be diagnosed accurately and objectively, from off-line measurements of myocardial velocities recorded noninvasively by tissue Doppler echocardiography during dobutamine stress.

In this study, difference in average S′ and average E′ among two study groups is statistically insignificant, but difference in average A′ and Avg E/E′ has significant p value. The diastolic parameters E prime and A prime were not competitively increased in CAD group. However, there were decrease in E velocity and increase in A velocity as occurred in other studies. Average E/E′ ratios of all three myocardial segments measured are significantly increased and the increasing change (3.15) well correlated with CAD detection in diastolic stress test. The average increase in E/E′ ratio well correlated in patients with positive TMT.

In this study, TMT positive had 56% sensitivity for detection of CAD, when combining an increase in E/E′ value with stress echo, its sensitivity rose to 71%. Moreover including objective measurement of WMAs with other parameters sensitivity for detection of CAD was as high as 75% in this study. It needs further study with a larger population to decide whether E/E′ stands as a sensitive marker to diagnose CAD.