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

Abstract

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.