EFFECTS OF QRS DURATION ON MYOCARDIAL PERFORMANCE AS ASSESSED BY Z-RATIO AND TEI-INDEX IN CHRONIC HEART FAILURE PATIENTS

Objective: We aimed to compare the effect of QRS duration on Tei-index, a measure of effective pump time and myocardial performance, and Z ratio. Methodology: We retrospectively analysed the ECG and Echocardiographic data of 83 patients with stable chronic heart failure in cardiology department of a teaching hospital. Echocardiograms were recorded using a Hewlett Packard Sonos 2000 echocardiograph with a 2.5 MHz transducer. Results: Tei-index and Z-ratio were previously reported3 within normal limits in normal controls (n= 17). Tei-index was significantly increased in patients with heart failure but with normal activation (p < 0.0001), but not the Z-ratio (p = 0.4). Both Z-ratio and Tei-index were abnormal in dilated cardiomyopathy with LBBB (p<0.0001). There was a significant inverse correlation between the duration of QRS and Z-ratio (r=-0.58; p<0.0001). Similarly QRS duration is directly correlated with Tei-index (r=0.36; p=0.0008). Varying values of QRS duration have different effects on the Z-ratios. There is a significant difference in the Zratio of patients with QRS duration of < 120 ms (Z-ratio 78 +/- 9), compared with QRS of > 120 ms (Z-ratio 68 +/- 11), with a p-value of < 0.0001. There was a significant difference in the Tei-index of patients with QRS of < 120 ms, (0.56 +/- 0.19) compared to that of patients with QRS of > 120 ms (0.66 +/- 0.18), (p=0.03). Conclusions: There is a strong correlation between QRS duration and Z-ratio as well as with Tei-index. Tei-index is sensitive to the presence of DCM, whether or not activation is normal whereas Z-ratio is much more specific for electrical abnormalities. QRS duration has profound effects on the mechanical activity of the heart in systole and diastole in patients with chronic heart failure.