The relationship between diastolic function of the left ventricle and QT dispersion in patients with myocardial infarction

Survey of the effect of streptokinase on ventricular repolarization by examining the QT dispersion in patients with acute myocardial infraction in Seyed-Al-Shohada hospital, Urmia

Cardiovascular events are the most common cause of morbidity and mortality throughout the world and myocardial infarction is the most common cause of these accidents. Myocardial infarction impairs the mechanical and electrical activity of the heart that these disorders predispose the patient to cardiac arrhythmias including ventricular tachycardia. QT dispersion is an important parameter to evaluate the heterogeneity of ventricular repolarization that minimal and the maximum interval is QTc in 12-lead EKG. In this study, 200 patients with the diagnosis of acute myocardial infraction with ST-segment elevation were hospitalized and treated with streptokinase. Patient records were extracted from the medical records department. EKG was studied before receiving streptokinase, an hour after receiving streptokinase and 4 days later for calculating and comparing QTd. It was concluded that QTd mean in EKG one hour after receiving streptokinase is decreased compared to pre-operation but this decline is not statistically significant. QTd mean in EKG day 4 after MI is slightly increased compared to the baseline, which is not statistically significant.

Selection of patient for cardiac resynchronization therapy: role of QT corrected dispersion

AIMS

About 30 to 50% of patients undergoing cardiac resynchronization therapy (CRT) may not show clinical or echocardiographic improvement, despite fulfilling guidelines recommendations for CRT. For this reason, we need a more accurate method to assess CRT eligibility. The aims of this study were to verify, on a 12-month follow-up, the usefulness of QT corrected dispersion (QTcD) in a patient's selection for CRT.

METHODS

We stratified 53 patients who underwent CRT, into two groups based on the estimation of QTcD, that is, QTcD > 60 ms and QTcD ≤ 60 ms. In all patients were performed New York Heart Association (NYHA) class determination, six-minute walking test, QtcD, and QRS measurements, and complete echocardiographic assessment at 1, 3, 6, and 12 months after implantation.

RESULTS

At baseline, there were no significant differences in clinical, echocardiographic, and electrocardiographic parameters duration between two groups. At 12-month follow-up between the two groups, there were significant differences in NYHA (1.2 ± 0.4 vs 2 ± 0.6; P < 0.01), six-minute walking distance (422 ± 68 vs 364 ± 68; P < 0.01), left ventricular (LV) ejection fraction (34 ± 7% vs 28 ± 6%; P < 0.01), LV end-diastolic diameter (57 ± 7 vs 63 ± 8; P < 0.01), and LV intraventricular dyssynchrony (24 ± 14 vs 39 ± 23; P < 0.01).

CONCLUSION

This study suggests that QTc dispersion in addition to QRS duration could improve the sensitivity of electrocardiogram in a patient's selection for CRT.

The effects of perindopril on QT duration and dispersion in patients with coronary slow flow

Coronary slow flow (CSF) is characterized by delayed opacification of coronary arteries in the absence epicardial occlusive disease. QT duration and dispersion have been reported to be longer in patients with CSF. ACE inhibitors may improve CSF through positive effects on endothelial function. The study included 32 patients having CSF and 25 subjects having normal coronary arteries in coronary angiography. The patients were evaluated with 12-leads electrocardiography and echocardiography before and 3 months after treatment with perindopril. Compared to the control group, maximum corrected QT duration (QTcmax) (432.0 ± 28.9 vs. 407.0 ± 39.1 ms, p = 0.008) and QT dispersion (QTcD) (64.0 ± 16.5 vs. 37.3 ± 12.1 ms, p < 0.001), mitral inflow deceleration time (DT) (251.3 ± 49.4 vs. 218.8 ± 44.5 ms, p = 0.013), and isovolumetric relaxation time (IVRT) (115.8 ± 18.4 vs. 107.2 ± 22.9 ms, p < 0.001) were significantly longer and E/A ratio 0.85 ± 0.2 vs. 1.1 ± 0.3, p = 0.004) was lower in patients with CSF. QTcmax (to 407.0 ± 28.0 ms, p = 0.001), QTcD (to 44.5 ± 11.4 ms, p < 0.001), DT (to 221.6 ± 37.7 ms, p < 0.001) and IVRT (to 103.8 ± 16.1 ms, p < 0.001) were significantly decreased and E/A ratio (to 0.98 ± 0.3, p < 0.001) was significantly increased after treatment with perindopril. Coronary slow may be associated with prolonged QT interval and increased QT dispersion and impaired diastolic filling. Perindopril may be helpful in restoration of these findings.

QTc dispersion in hyperthyroidism and its association with pulmonary hypertension

BACKGROUND

Several studies have reported that hyperthyroidism is associated with prolonged QT interval corrected by the heart rate (QTc) and pulmonary hypertension (PHT).

METHODS

Forty-seven patients with newly diagnosed overt hyperthyroidism and 20 healthy people were enrolled in the study. Transthoracic echocardiography, 12-lead surface electrocardiogram, and thyroid hormone levels were studied at the time of enrollment and after achievement of euthyroid state with propylthiouracil treatment.

RESULTS

Baseline clinical characteristics were similar. However, heart rate (90.5+/-19.6 vs 79.2+/-13.7 bpm, P = 0.024), pulmonary artery systolic pressure (PASP) (26.0+/-12.0 vs 10.6+/-4.0 mmHg, P < 0.001), E deceleration time (DT) (191.8+/-25.6 vs 177.0+/-10.7 ms, P = 0.016), isovolumetric relaxation time (IVRT) (91.38+/-12.3 vs 79.6+/-10.5 ms, P < 0.001), and QTc dispersion (QTcD) (50.3+/-17.2 vs 38.9+/-11.6 ms, P = 0.009) were significantly higher in hyperthyroid patients compared to control group. Heart rate (to 74.1+/-13.8, P < 0.001), QTcD (to 37.3+/-10.1 ms, P < 0.001), DT (to 185.3+/-19.7 ms, P = 0.008), IVRT (to 88.6+/-10.3 ms, P = 0.056), and PASP (23.1+/-10.1 mmHg P < 0.001) were significantly decreased after achievement of euthyroid state. Although PHT was present in 16 patients before treatment only six patients still had PHT during euyhyroid state. Compared to patients with normal PASP, QTcD was significantly longer in patients with PHT (56.5+/-15.8 vs 37.9+/-12.8 mmHg P < 0.001). There were also significant correlations between QTcD and presence of PHT (r = 0.516, P < 0.001) and PASP (r = 0.401, P = 0.009).

CONCLUSIONS

Hyperthyroidism is a reversible cause of PHT and diastolic dysfunction. Increased QTcD observed in hyperthyroidism may be associated with PHT and diastolic dysfunction. These abnormal findings in hyperthyroidism often normalize with the achievement of euthyroid state.

Association of corrected QT dispersion with symptoms improvement in patients receiving cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is theoretically expected to affect repolarization as well as depolarization. We studied the effects of CRT on corrected QT (QTc) dispersion in association with symptomatic improvement. QTc dispersion was analyzed in 26 consecutive patients (67 +/- 6 years old, 18 men and 8 women) who underwent CRT. CRT responders and nonresponders were defined as patients showing and not showing > or = 1 class New York Heart Association symptomatic improvement 3 months after CRT, respectively. QTc interval, QRS width, and QTc dispersion were measured automatically from digital data using an analyzing system. There were 18 CRT responders and 8 nonresponders among the patients. CRT responders showed significantly larger QTc dispersion than CRT nonresponders before CRT (102 +/- 26 vs 40 +/- 12 ms, P < 0.01). A significant decrease in QTc dispersion by CRT was observed in responders (102 +/- 26 to 52 +/- 15 ms, P < 0.01). In contrast, QTc dispersion was not decreased by CRT in nonresponders (40 +/- 12 to 39 +/- 11 ms, not significant). The difference observed before CRT was thus abolished after CRT (52 +/- 15 vs 39 +/- 11 ms, not significant). Baseline values and changes in QRS width or QTc, as well as asynchrony of wall motion determined by tissue Doppler imaging, were not different between CRT responders and nonresponders before CRT. The present study with a small number of patients shows the potential utility of QTc dispersion for distinguishing CRT responders from CRT nonresponders before CRT, and warrants further study with a greater number of patients.

Acute reduction of ventricular volume decreases QT interval dispersion in elderly subjects with and without heart failure

To evaluate the effects of acute reduction in ventricular volume (VV) on QT interval dispersion (QTd), 14 men with heart failure (HF; 74.5 ± 2 yr of age) and 11 healthy male control subjects (68 ± 2 yr of age) were studied. For 15 min, lower body negative pressure (LBNP) was applied at −15 and −40 mmHg to reduce venous return. At baseline and during LBNP application, QTd was measured with an 87-lead, body-surface-mapping device; chamber volumes were assessed by radioisotope ventriculography; blood pressure (BP) and heart rate (HR) were continuously monitored; and blood samples were obtained for assessment of norepinephrine (Nor) levels. At −15 mmHg, LNBP application induced a significant decrease in VV but did not change BP and HR in both groups. In addition, Nor levels increased significantly ( P ≤ 0.05) in the control group (from 286.7 ± 31.5 to 388.8 ± 41.2 pg/ml) and in HF patients (from 405.8 ± 56 to 477.6 ± 47 pg/ml), and QTd was significantly ( P ≤ 0.05) decreased in the control group (57.2 ± 3.8 vs. 49.1 ± 3.4 ms) and in HF patients (67.8 ± 6 vs. 63.7 ± 5.9 ms). No additional decreases in VV or QTd were produced by −40 mmHg LNBP, but Nor levels did increase in both groups and reach 475.5 ± 34 and 586.5 ± 60 pg/ml ( P < 0.05) in the control and HF groups, respectively; BP did not change, but HR also increased in both groups. In conclusion, an acute LBNP-induced reduction in VV caused a decrease in the QTd of elderly men regardless of the existence of HF. Because increased sympathetic activity with more intense LBNP was not accompanied by additional changes in QTd, altered QTd may be better related to changes in VV than to autonomic nervous system activity.

QT dispersion correlates with systolic rather than diastolic parameters in patients receiving anthracycline treatment

OBJECTIVE

The aim of this study was to investigate the relation of QT dispersion to left ventricular (LV) systolic and diastolic function in patients undergoing anthracycline therapy.

METHODS

We used echocardiography to evaluate LV systolic and diastolic function and electrocardiography to evaluate QT dispersion and corrected QT dispersion (QTcD) in patients with hematological diseases, who received anthracycline therapy.

PATIENTS

Seventy-two patients with hematological diseases who were receiving anthracycline treatment were enrolled in the present study.

RESULTS

LV end-diastolic diameter or LV end-systolic diameter had a significant positive correlation to QTcD (r = 0.35, p < 0.01, r = 0.43, p < 0.01). Also left ventricular ejection fraction of (LVEF) or fractional shortening had a significant negative correlation to QTcD (r = -0.46, p < 0.001, r = -0.27, p = 0.02). The highest QTcD group had a significantly larger LV end-diastolic diameter or LV end-systolic diameter than the lowest QTcD [48.5 +/- 5.7 vs. 44.4 +/- 4.5 (mm), p < 0.001, 34.1 +/- 6.4 vs. 28.8 +/- 4.3 (mm), p < 0.001] and the highest QTcD group had a significantly lower LVEF than the lowest QTcD [57.5 +/- 8.0 vs. 65.5 +/- 6.4 (%), p < 0.001]. On the other hand, none of the diastolic function markers were significantly correlated with QTcD.

CONCLUSION

We concluded that increased QTcD is correlated with LV dilation and systolic dysfunction induced by anthracycline therapy, and does not reflect a dispersion of ventricular repolarization or asynchronous motion.

Relation of early changes of QT dispersion to changes in left ventricular systolic and diastolic function after a first acute myocardial infarction

OBJECTIVE

To describe the relation between changes of left ventricular systolic and diastolic function and changes of QT dispersion (difference in duration between longest and shortest QT interval) following acute myocardial infarction.

DESIGN

QT dispersion was determined at admission, hospital discharge, and 1 and 3 months following myocardial infarction in 64 consecutive 1-year survivors. Patients were divided into Group A where QT dispersion was < 52 ms at all recordings or initially > 52 ms but decreased during follow-up, and Group B where QT dispersion remained increased > or = 52 ms at all measurements. Doppler-Echocardiography was carried out on day 1, day 5, and after 1, 3, and 12 months.

RESULTS

In 26 patients QT dispersion remained increased > or = 52 ms during the first 3 months after infarction. Among these a significant increase of end-systolic volume was seen whereas low or rapid normalized QT dispersion was associated with a significant decrease of ventricular volumes. After 1 year end-systolic (70 +/- 32 ml vs 49 +/- 16 ml, p = 0.006) and end-diastolic volumes (138 +/- 41 ml vs 105 +/- 22 ml, p = 0.001) were higher in Group B. In a multivariate model Group B was significantly related to an increase of end-diastolic volume (p = 0.01). In Group A diastolic function improved in eight patients and in two it deteriorated, whereas improvement was seen in one patient and deterioration in nine patients from Group B (p < 0.01).

CONCLUSION

Following myocardial infarction low QT dispersion is associated with preserved left ventricular function, whereas persistently increased dispersion is associated with left ventricular dilation and deterioration of diastolic function.