The Impact of Exercise-Induced Changes in Intraventricular Dyssynchrony on Functional Improvement in Patients with Nonischemic Cardiomyopathy

Assesment of myocardial ischemia by combination of tissue synchronisation imaging and dobutamine stress echocardiography

BACKGROUND AND OBJECTIVES

Dobutamine stress echocardiography (DSE) is an important non-invasive imaging method for evaluating ischemia. However, wall motion interpretation can be impaired by the experience level of the interpreter and the subjectivity of the visual assessment. In our study we aimed to combine DSE and tissue syncronisation imaging to increase sensitivity for detecting ischemia.

SUBJECTS AND METHODS

50 patients with indications for DSE were included in the study. In 25 patients we found DSE positive for ischemia and in the other 25 patients we found it to be negative. The negative group was accepted as the control group. There was no significant difference in terms of risk factors and echocardiographic parameters between the two groups, except for wall motion scores. In both groups, left ventricular dyssychrony was accepted as the difference between time to peak systolic velocity (Ts) in the reciprocal four couple of non-apical segments at rest and during peak stress. Timings were corrected for heart rate. We compared the differences of the dyssynchronisation value at rest and during peak stress to determine the distinctions within the groups and between the groups of DSE positive and negative patients.

RESULTS

We found that stress and ischemia did not create any significant difference over the left intraventricular dyssynchrony with DSE, although at the segmenter level it prolonged the time to peak systolic velocity (p<0.05). These alterations did not show any significant difference between positive and negative DSE groups.

CONCLUSION

As a result, this segmenter dyssynchrony and the time to peak systolic velocity, which is corrected for heart rate, did not enhance any new value over DSE for detecting ischemia.

Importance of dynamic dyssynchrony in the occurrence of hypertensive heart failure with normal ejection fraction

AIMS

The impact of haemodynamic stress on left ventricular (LV) dyssynchrony in heart failure with normal ejection fraction (HFNEF) remains unknown. We sought to evaluate the relationship and predictive value of dynamic changes of LV dyssynchrony on hypertensive HFNEF.

METHODS AND RESULTS

A total of 131 subjects including 47 hypertensive HFNEF patients, 34 hypertensive patients with left ventricular hypertrophy (LVH) without HFNEF, and 50 normal controls were studied by dobutamine stress echocardiography with tissue Doppler imaging. Systolic and diastolic dyssynchrony were assessed using the LV six-basal-six-mid-segment model and cut-off values were derived from normal controls. The mean basal segments longitudinal systolic (mean Sm) and early diastolic (mean Em) velocities were measured. In normal controls, systolic and diastolic dyssynchrony did not develop during stress. The prevalence of resting systolic (36.2% vs. 38.2%, P = 0.85) and diastolic (34.0% vs. 29.4%, P = 0.66) dyssynchrony was similar in HFNEF and LVH groups. During stress, the prevalence of systolic and diastolic dyssynchrony increased dramatically to 85.1% and 87.2%, respectively, in HFNEF group, but only 52.9% and 58.8% in LVH group (P < 0.005). In HFNEF group, stress-induced increase in mean Sm was significantly blunted (2.8 ± 2.0 vs. 4.2 ± 2.4 cm/s, P = 0.004), and the increase was abolished for mean Em (-0.3 ± 2.5 vs. 2.4 ± 3.4 cm/s, P < 0.001). On multivariate analysis, stress-induced changes in mean Em (OR = 0.69, P = 0.004) and mean Sm (OR = 0.56, P = 0.004), and diastolic (OR = 4.6, P = 0.005) and systolic dyssynchrony during stress (OR = 4.3, P = 0.038) were independent determinants for occurrence of HFNEF.

CONCLUSION

Dynamic dyssynchrony during stress and impaired myocardial longitudinal function reserve are characteristics of HFNEF.

Different effect of exercise on left ventricular diastolic time and interventricular dyssynchrony in heart failure patients with and without left bundle branch block

BACKGROUND

In patients with idiopathic dilated cardiomyopathy (IDCM) a prolongation of left ventricular (LV) systole at the expense of diastolic time was demonstrated. Our study was aimed to evaluate the effect of exercise on heart rate corrected diastolic time in controls, IDCM with and without LBBB, and patients with LBBB and normal LV function.

METHODS

47 patients with IDCM, 30 without LBBB, and 17 with LBBB as well as 11 with isolated LBBB were studied during exercise using a combined hemodynamic-radionuclide angiographic approach. The phases of the cardiac cycle were derived with high temporal resolution from the ventricular time-activity curve. The loss of diastolic time per beat (LDT) was quantified using a regression equation obtained from a control group (n=24).

RESULTS

A significant LDT was demonstrated at rest and during peak exercise in IDCM patients with LBBB (39.1+/-32 and 37.3+/-30 ms; p < 0.001). In IDCM patients with normal activation LDT was unaffected at baseline, but elevated during peak exercise. This response was paralleled by an increase in interventricular mechanical dyssynchrony.

CONCLUSION

During exercise an abnormal shortening of LV diastolic time is a common characteristic of heart failure patients which can be explained by the high prevalence of mechanical dyssynchrony.