Early Diastolic Time Intervals Research Articles

Bidomain Predictions of Virtual Electrode-Induced Make and Break Excitations around Blood Vessels

Virtual electrodes formed by field stimulation during defibrillation of cardiac tissue play an important role in eliciting activations. It has been suggested that the coronary vasculature is an important source of virtual electrodes, especially during low-energy defibrillation. This work aims to further the understanding of how virtual electrodes from the coronary vasculature influence defibrillation outcomes. Using the bidomain model, we investigated how field stimulation elicited activations from virtual electrodes around idealized intramural blood vessels. Strength-interval curves, which quantify the stimulus strength required to elicit wavefront propagation from the vessels at different states of tissue refractoriness, were computed for each idealized geometry. Make excitations occurred at late diastolic intervals, originating from regions of depolarization around the vessel. Break excitations occurred at early diastolic intervals, whereby the vessels were able to excite surrounding refractory tissue due to the local restoration of excitability by virtual electrode-induced hyperpolarizations. Overall, strength-interval curves had similar morphologies and underlying excitation mechanisms compared with previous experimental and numerical unipolar stimulation studies of cardiac tissue. Including the presence of the vessel wall increased the field strength required for make excitations but decreased the field strength required for break excitations, and the field strength at which break excitations occurred was generally greater than 5 V/cm. Finally, in a more realistic ventricular slice geometry, the proximity of virtual electrodes around subepicardial vessels was seen to cause break excitations in the form of propagating unstable wavelets to the subepicardial layer. Representing the blood vessel wall microstructure in computational bidomain models of defibrillation is recommended as it significantly alters the electrophysiological response of the vessel to field stimulation. Although vessels may facilitate excitation of relatively refractory tissue via break excitations, the field strength required for this is generally greater than those used in the literature on low-energy defibrillation. However, the high-intensity shocks used in standard defibrillation may elicit break excitation propagation from the coronary vasculature.

The effects of hormone replacement therapy on myocardial performance in early postmenopausal women

Objectives The results of the studies in which the effect of hormone replacement therapy (HRT) on cardiac function have been evaluated are rather disputable. In these studies, cardiac function was evaluated with conventional echocardiographic methods. This study was planned in order to investigate the effects of HRT on myocardial velocities and myocardial performance index (MPI) in healthy early postmenopausal women.Method In a prospective, controlled study, 60 healthy postmenopausal women were assigned to two groups (32 in the HRT group and 28 in the control group). After conventional echocardiographic parameters were measured, tissue Doppler echocardiography recordings were obtained from the mitral and tricuspid annulus. Systolic myocardial velocity (Sm), early and late diastolic myocardial velocities (Em and Am) and time intervals were measured and MPI was calculated. Then the symptom-limited exercise stress test using the Bruce protocol was performed. After 3 and 6 months of HRT (oral 0.625 mg conjugated estrogen + 2.5 mg medroxyprogesterone acetate/day), the same examinations were repeated. The effects of HRT on myocardial velocities, MPI and exercise time were evaluated at the 3rd and 6th months.Results The parameters of the control group remained statistically unchanged during the study. HRT did not have any effect on segmental and mean left ventricular (LV) Sm or right ventricular (RV) Sm. However, LV Em/Am and RV Em/Am ratios significantly increased at the 6th month of HRT, and LV and RV MPI values were observed to decrease significantly as compared to basal values. Additionally, a significant increase was observed in exercise duration and metabolic equivalent values after 3 months of HRT, and this increase continued at the 6th month as well. The favorable changes in all parameters in the HRT group were significantly different from those of the control group.Conclusion Data obtained in this study suggest that HRT is not only effective for treating menopausal complaints but also increases cardiovascular performance by improving especially diastolic functions in early postmenopausal women.

The Effect of Isolated Left Bundle Branch Block on the Myocardial Velocities and Myocardial Performance Index

This study was planned in order to investigate the effect of left bundle branch block (LBBB) on myocardial velocities obtained by tissue Doppler echocardiography (TDE) and myocardial performance index (MPI). Subjects with LBBB (n = 61) and age-matched healthy subjects (n = 60) were enrolled in the study. Left ventricular (LV) ejection fraction (EF), mitral inflow velocities (E-wave and A-wave), isovolumetric contraction and relaxation time (ICT and IRT), ejection time (ET), and flow propagation velocity (Vp) were measured by conventional echocardiography. Systolic velocity (Sm), early and late diastolic velocities (Em and Am) and time intervals were measured by TDE. MPI was calculated by the formula (ICT + IRT)/ET. LVEF and mitral E/A ratio were similar in both groups. Vp was lower in the LBBB group than in the control group, whereas the E/Em and the E/Vp ratio was higher. LV Sm and Em/Am ratio were lower in LBBB group. Right ventricular Sm and Em/Am ratio were similar in both groups. LV mean and RV MPI were significantly increased in LBBB group. These findings obtained by TDE show that isolated LBBB impairs the ventricular functions. Both of the LV and RV dysfunctions shown by the new parameters may contribute to increased morbidity and mortality in cases with isolated LBBB.

Effects of Menopause on the Myocardial Velocities and Myocardial Performance Index

Although menopause is known to increase cardiovascular risk and mortality, the effect of menopause on cardiac functions has not been investigated in detail. This study investigates the effect of menopause on cardiac functions by tissue Doppler echocardiography (TDE) and myocardial performance index (MPI). A total of 72 postmenopausal and 71 age-matched premenopausal women were enrolled in the study. After conventional echocardiographic parameters were measured, TDE recordings were obtained at the septal, lateral, anterior and inferior side of the mitral annulus, and tricuspid lateral annulus. Systolic velocity (Sm), early and late diastolic velocities (Em and Am) and time intervals were measured and MPI was calculated. A sequentially symptom-limited exercise stress test was performed. Although left ventricular (LV) ejection fraction and end-diastolic and end-systolic diameter were similar in both groups, LV septum and posterior wall thickness were higher in postmenopausal women. Mitral early inflow velocity and mitral early inflow velocity:mitral late inflow velocity ratio were significantly lower in postmenopausal women compared to premenopausal women. LV Sm, and LV and right ventricular (RV) Em:Am ratios were lower in postmenopausal women. MPI calculated by TDE was significantly increased in postmenopausal women. In addition, exercise duration and metabolic equivalent values were significantly lower in postmenopausal women than in premenopausal women. Menopause negatively affects MPI and myocardial velocities, both of which provide more quantitative data about myocardial functions. These findings indicate that the hormonal changes in menopause impair LV systolic and diastolic functions and RV diastolic function.

Multi–Detector Row CT Coronary Angiography: Influence of Reconstruction Technique and Heart Rate on Image Quality

To prospectively evaluate to what extent image quality in 16-detector row computed tomographic (CT) coronary angiography is a function of the heart rate and the image reconstruction technique used. A total of 70 patients (49 men, 21 women; mean age, 59.1 years +/- 5.8 [standard deviation]) consecutively underwent multi-detector row CT coronary angiography; 49 patients additionally underwent coronary angiography. Image reconstruction was based on both relative and absolute timing. A total of 20 equidistant relative and absolute image reconstructed intervals were assessed by applying a four-step grading scale. Cluster and discrimination analysis, Spearman correlation analysis, and Wilcoxon and chi2 tests were used for statistical analysis. Institutional review board approval and written informed consent were obtained. Though significantly (P < .001) better image quality was observed for image reconstruction based on absolute timing and in patients with lower heart rates, influence on diagnostic accuracy was not significant. Irrespective of the reconstruction technique used, best image quality was observed in patients with a low heart rate for middiastolic reconstruction intervals (starting points: 61% of R-R interval [range, 40%-75%] and 599.3 msec after R [range, 450-840 msec]) and in patients with a high heart rate for end-systolic or early-diastolic intervals (starting points: 27.3% of R-R interval [range, 10%-45%] and 202.3 msec after R [range, 82-336 msec]). With regard to the vessel section and reconstruction technique, cutoff heart rates of the intervals were 64.0-68.5 beats per minute. Patients with stenoses of more than 50% were identified with 86% sensitivity and specificity, and there was no significant difference between relative and absolute timing (P = .99). In multi-detector row CT coronary angiography, image quality depends on the choice of a suited reconstruction interval. In patients with high heart rates, the best image quality can be obtained with end-systolic and early-diastolic intervals; in patients with low heart rates, the best results are achieved with middiastolic intervals.

Right ventricular function in patients with acute anterior myocardial infarction: tissue Doppler echocardiographic approach

Objective — Our purpose was to investigate the right ventricular (RV) performance of patients with a first acute anterior myocardial infarction (AAMI) by using pulsed wave Doppler tissue (PWDT) samplings of tricuspid annulus and RV free wall.Methods and results — The study group included 31 patients with AAMI and 20 age-matched controls. Conventional indexes of RV functions were the magnitude of tricuspid annular plane systolic excursion (TAPSE), and the transpulmonary and transtricuspid Doppler parameters. PWDT velocities were obtained by placing the sample volume at the lateral tricuspid annulus and the mid-segment of RV free wall; the peak systolic (S), early (E) and late (A) diastolic PWDT velocities and time intervals from ECG-Q wave to their peaks were analysed. Standard indexes were comparable except TAPSE that was significantly lower in AAMI-patients (p < 0.001). S velocities were similar; A of both regions (p = 0.018 and 0.012) and E of RV free wall (p = 0.011) were significantly increased in AAMI-group. Q-Sa intervals in both regions (p = 0.007 and 0.015) and Q-Ea of tricuspid annulus (p = 0.045) were significantly shorter in patients with AAMI.TAPSE and E of RV free wall had significant negative correlations with left ventricular systolic volume index and right atrial filling fraction (AFF), respectively (r = -0.46, p = 0.01 for both). A of tricuspid annulus had a positive correlation with left AFF (r = 0.42, p = 0.02).Conclusion — PWDT imaging of tricuspid annulus and RV free wall is capable to sensitively detect the adaptive mechanisms and unfavourable diastolic properties of RV dynamics in patients with AAMI.

Early diastolic left ventricular function as a marker of acute cardiac rejection: a prospective serial echocardiographic study

Changes in left ventricular early diastolic time intervals are sensitive indicators of incipient left ventricular dysfunction. We tested the hypothesis that acute rejection in cardiac transplant recipients is associated with alteration of early diastolic myocardial function, as expressed by the time interval Te, a parameter derived from digitized M-mode echocardiograms. Te is defined as the time interval between maximal posterior wall contraction and the point of peak posterior wall endocardium retraction velocity, as determined by the nadir of the computed first derivative curve. In trasplant patients without rejection (group A, n = 48), Te was prolonged compared to healthy individuals (group C, n = 35) (79.0 ± 12.5 ms vs 64.0 ± 7.9 ms; p < 0.0001). During acute rejection (group B, n = 18) transplant patients had significantly longer mean Te values compared to transplant patients without rejection (group A) (97.8 ± 17.9 ms vs 79.0 ± 12.5 ms; p < 0.0001). Longitudinal studies in individual patients (group D, n = 18) demonstrated that rejection is associated with prolongation of Te (94.5 ± 16.0 ms during rejection vs 79.0 ± 10.3 ms before rejection; p < 0.0002) and that Te returns to individual baseline values in response to treatment (79.2 ± 9.4 ms after therapy vs 79.0 ± 10.3 ms before rejection; NS). In a prospective study, Te changes in transplant patients (group E, n = 96) were correlated with myocardial biopsy results. Sixty-one biopsies showed acute rejection, and 115 biopsies were negative. Taking a 20% increase in Te compared to pre-rejection values as the criterion for an acute rejection, the sensitivity, specificity, positive and negative predictive values were 80, 94, 88, and 90%, respectively. We conclude that the parameter Te is a useful non-invasive marker of acute cardiac rejection.

Echocardiographic Measurement of Early Diastolic Time Intervals in Patients with Hypertension - With Reference to Regional Nonuniformity and Restoring Forces -

Echocardiographic Measurement of Early Diastolic Time Intervals in Patients with Hypertension - With Reference to Regional Nonuniformity and Restoring Forces -

Effect of Disopyramide on Systolic and Early Diastolic Time Intervals in Patients with Hypertrophic Cardiomyopathy

The present study clarified the effect of disopyramide on left-ventricular function in patients with hypertrophic cardiomyopathy (5 obstructive type: HOCM, 21 non-obstructive type: HNCM). The systolic and early diastolic time intervals were assessed 3 hours after a single oral administration of 100-mg disopyramide. The following parameters were evaluated at rest and after administration of disopyramide: 1) left-ventricular ejection time index (LVETI), 2) pre-ejection period index (PEPI), 3) the interval from aortic component of the second heart sound to mitral valve opening (IIA-MVO), and 4) the interval from MVO to O point of apexcardiogram (MVO-O). LVETI in HNCM did not change after disopyramide but that in HOCM was significantly shortened (P less than .05). PEPI in both HOCM and HNCM was significantly prolonged after administration of disopyramide. IIA-MVO time in both HOCM and HNCM was not influenced by disopyramide. MVO-O time in both HOCM and HNCM was significantly shortened after disopyramide. These results suggest that 1) shortening of LVETI in HOCM after disopyramide seemed to be due to the decrease in pressure gradient, 2) PEPI prolongation after disopyramide reflected the decrease in myocardial contractility, and 3) shortening of MVO-O time after disopyramide indicated the improvement of left-ventricular filling. The authors conclude that disopyramide may be an important new therapeutic agent in the treatment of patients with hypertrophic cardiomyopathy.

No Influence of Heart Rate on Early Diastolic Time Intervals

To elucidate the influence of the heart rate on early diastolic time intervals (EDTI) - from the second heart sound to the point of mitral valve opening (IIA-MVO) and from MVO to the O point of the apexcardiogram (MVO-O) –, we studied the relationship between R-R interval and EDTI in 38 patients with atrial fibrillation (AF): 8 patients had AF alone, 7 additionally had hypertension, 7 idiopathic dilated cardiomyopathy, 6 hypertrophic cardiomyopathy, 7 ischemic heart disease, and 3 hyperthyroidism (AF study). We also studied the change of EDTI during atrial pacing (80–140 beats/min) in 5 normal subjects (pacing study). The results were expressed by variation rate, calculated as (B-A/A) × 100 (A = EDTI at minimal R-R interval, B = maximal EDTI). AF study: The variation rates of IIA-MVO and MVO-O were 7.4 ± 5.2 and 7.1 ± 3.5%, respectively. A correlation was not found between the preceding R-R interval and EDTI. This finding was common in the diseases studied. Pacing study: The variation rates of IIA-MVO and MVO-O were 0.3 ± 0.1 and 0.2 ± 0.1%, respectively. The results indicate that EDTI were not affected by the heart rate which ranged from 50 to 140 beats/min, and thus EDTI are not necessarily to be corrected by heart rate.

The Effects of Captopril(Capril®) on Early Diastolic Time Intervals in Dilated Cardiomyopathy

The Effects of Captopril(Capril®) on Early Diastolic Time Intervals in Dilated Cardiomyopathy

Noninvasive Evaluation of Left Ventricular Diastolic Function in Patients with Angina Pectoris -Pulsed Doppler Echocardiographic Technique-

To assess the disturbed left ventricular diastolic filling by pulsed Doppler echocardiography in patients with angina pectoris who have normal systolic function, 55 subjects (33 angina patients with, 22 control subjects without significant (⩾75%) coronary artery narrowing) underwent pulsed Doppler echocardiography examination one day before coronary arteriography.From analysis of the transmitral flow velocity curve, diastolic time intervals, peak early and late atrial flow velocities, the ratio of early to atrial peak flow velocity, and deceleration slope after peak early flow velocity were measured. The angina group had a significantly higher peak atrial flow velocity (50.1 ± 10.0 cm/sec vs. 43.7 ± 9.0, p<0.05) and a lower ratio of early to atrial peak flow velocity (0.91 ± 0.24 vs. 1.17 ± 0.30, p<0.005), but peak early flow velocity, deceleration slope, and diastolic time intervals were similar in both groups. Therefore, the pulsed Doppler technique using the transmitral flow velocity curve is thought to be useful in the noninvasive evaluation of diastolic function even in patients with angina pectoris who have normal systolic function and no left ventricular hypertrophy.

Early diastolic time intervals during hypertensive pregnancy.

Early diastolic time intervals have been assessed by means of the echopolycardiographic method in 17 pregnant women who developed hypertension during pregnancy (HP) and in 14 normal pregnant women (N). Systolic time intervals (STI), stroke volume (SV), ejection fraction (EF), and mean velocity of myocardial fiber shortening (VCF) were also evaluated. Recordings were performed in the left lateral decubitus (LLD) and then in the supine decubitus (SD). In LLD, isovolumic relaxation period (IRP) was prolonged in the hypertensive pregnant women compared with normal pregnant women (HP 51 +/- 12.5 ms, N 32.4 +/- 15 ms p less than 0.05), whereas time of the mitral valve maximum opening (DE) was not different in the groups. There was no difference in SV, EF, and mean VCF, whereas STI showed only a significant (p less than 0.05) lengthening of pre-ejection period (PEP) in HP. When the subjects shifted from the left lateral to the supine decubitus position, left ventricular ejection time index (LVETi) and SV decreased significantly (p less than 0.05) in both normotensive hypertensive pregnant women. IRP and PEP lengthened significantly (p less than 0.05) only in normals, whereas they were unchanged in HP. DE time did not vary in either group. In conclusion, hypertension superimposed on pregnancy induces lengthening of IRP, as well as of PEP, and minimizes the effects of the postural changes in preload on the above-mentioned time intervals.

Clinical significance of early diastolic time intervals for the differentiation of idiopathic dilative cardiomyopathy from ischemic cardiomyopathy.

In order to differentiate idiopathic dilative cardiomyopathy from ischemic cardiomyopathy noninvasively, systolic time intervals (STIs) and early diastolic time intervals were investigated in patients with idiopathic dilative cardiomyopathy (n = 11), patients with ischemic cardiomyopathy (n = 8), and normal controls (n = 17). Minimal left ventricular pressure and pulmonary capillary wedge pressure (PCWP) were also measured to clarify the relationship between early diastolic time intervals and early diastolic hemodynamics. Cardiac function estimated by STIs was markedly depressed both in idiopathic dilative cardiomyopathy and ischemic cardiomyopathy, and there was no difference between the two diseases. In early diastolic time intervals, IIA-O time (the interval from the aortic component of the second heart sound to the O point of apexcardiogram) was significantly prolonged both in idiopathic dilative cardiomyopathy (144 +/- 31 (SD); p less than 0.01) and ischemic cardiomyopathy (153 +/- 15; p less than 0.01) compared to normal controls (126 +/- 11). IIA-MVO time (the interval from IIA to the mitral valve opening) in idiopathic dilative cardiomyopathy (49 +/- 23) was significantly shorter than that in normal controls (70 +/- 8; p less than 0.05). On the contrary, IIA-MVO time in ischemic cardiomyopathy (126 +/- 11) was markedly prolonged compared with normal controls (p less than 0.01) and idiopathic dilative cardiomyopathy (p less than 0.01). MVO-O time was significantly prolonged in idiopathic dilative cardiomyopathy (94 +/- 18; p less than 0.01). However, it was conversely shortened in ischemic cardiomyopathy (25 +/- 15) compared with normal controls (54 +/- 7; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical significance of early diastolic time intervals for the evaluation of left ventricular function in patients with coronary artery disease.

To investigate non-invasively the diagnostic significance of diastolic properties in coronary artery disease (CAD), the following early diastolic time intervals (EDTIs): IIA-O time (from the aortic component of the second heart sound to the O-point on the apexcardiogram), IIA-MVO time (from IIA to the mitral valve opening) and MVO-O time (from MVO to the O-point), were estimated in 18 patients with angina pectoris (AP) and 29 with old myocardial infarction (OMI) who were subdivided into two groups according to ejection fraction (EF): group I (OMI-I): more than 50% and group II (OMI-II): less than 50%. Seventeen patients without evidence of CAD were used as controls (N). Left ventricular pressure (LVP) and pulmonary capillary wedge pressure (PCWP) were measured simultaneously to clarify the relationship between EDTIs and early diastolic hemodynamics. IIA-O time and IIA-MVO time in AP, OMI-I and OMI-II were significantly longer than in N. This prolongation accorded with the reduction of left ventricular function. MVO-O time in AP and OMI-I also was significantly longer compared with that in N. In OMI-II, however, it was significantly shorter than in N. The prolongation of IIA-MVO time reflected impaired LV relaxation accompanied by LV dysfunction. The maintenance of low minimal LVP was the main contributor to the lengthening of MVO-O time in AP and OMI-I. Conversely, elevated minimal LVP and impaired LV relaxation resulted in the shortening of MVO-O time in OMI-II.(ABSTRACT TRUNCATED AT 250 WORDS)

Difference in myocardial characteristics between hypertrophic cardiomyopathy and myocardial hypertrophy due to essential hypertension.

To investigate the qualitative difference in myocardial hypertrophy that exists between hypertrophic cardiomyopathy (HCM) and essential hypertension (HT), we measured the mean wall thickness (MWT), the early diastolic time intervals (IIA-MVO time: from the second heart sound to the point of mitral valve opening, MVO-O time: from MVO to the O point of apexcardiogram) and the MVO-O/IIA-MVO ratio. The MWT in HCM and HT was measured by biventriculogram and echocardiogram, respectively. The MWT showed no significant difference between HT (13.1 +/- 3.0 mm) and non-obstructive type of HCM (14.8 +/- 3.7), but the MWT in obstructive type (1.08 +/- 0.24) was significantly thinner than that in HT. As the MWT increased, both IIA-MVO and MVO-O time were prolonged in both groups. But the mode of prolongation was quite different. In HT, the prolongation of the IIA-MVO time was almost always greater than that of the MVO-O time. In HCM, the prolongation of the latter was greater than that of the former. The MVO-O/IIA-MVO ratio in HT was significantly less than that in normal subjects, but those in HCM were significantly greater. These findings suggest that the differences in the early diastolic time intervals between HCM and HT are not due to the magnitude of the left ventricular hypertrophy, but due to myocardial characteristics.

Diagnostic significance of early diastolic time intervals in patients with hypertrophic cardiomyopathy and myocardial hypertrophy due to essential hypertension.

In order to differentiate hypertrophic cardiomyopathy (HCM) from myocardial hypertrophy due to essential hypertension (HT), echocardiogram, apexcardiogram and phonocardiogram were simultaneously recorded in patients with HCM (n = 22), HT (n = 34) and normal subjects (N) (n = 22). The following early diastolic time intervals were measured: 1) IIA-O time, 2) IIA-MVO time (IRT) and 3) MVO-O time. The IIA-O time was 119 +/- 9 msec in N, 159 +/- 31 in HT (p less than 0.001, vs N) and 228 +/- 57 in HCM (p less than 0.001, vs N and HT, respectively). The IIA-MVO time was 66 +/- 11 msec in N, 95 +/- 18 in HT (p less than 0.001, vs N) and 102 +/- 24 in HCM (p less than 0.001, vs N). The MVO-O time was 53 +/- 9 msec in N, 66 +/- 21 in HT and 126 +/- 48 in HCM (p less than 0.001, vs N and HT, respectively). These results showed that among the early diastolic time intervals HT was abnormal only in the IIA-MVO time. On the other hand, HCM had abnormalities not only in the IIA-MVO time but also in the MVO-O time. Both the IIA-MVO and the MVO-O times in hypertrophic non-obstructive cardiomyopathy were prolonged significantly as compared to those in obstructive one. Analysis of early diastolic time intervals may be very useful to differentiate HCM, especially of the non-obstructive type, from HT.