Isovolumic Phase Research Articles

The Structure of Left Ventricular Relaxation in Case of Ventriculography.

To study the relaxation structure of the left ventricle (LV) in patients who underwent ventriculography. LV ventriculography was performed in 37 patients. Before catheterization, echocardiography was performed in each patient. In 6 patients, the LV ejection fraction (EF) was below 40%; these patients with systolic dysfunction were not included in the study. In 31 patients, the LV EF was higher than 50%. In this group, 13 patients had NYHA functional class (FC) 2-3 chronic heart failure (CHF); the rest of the patients had FC 1 CHF. Eighteen of 31 patients had stable ischemic heart disease; 50% of these patients had a history of myocardial infarction; the rest of the patients had hypertension and atrial and ventricular arrhythmias. The dynamics of the LV pressure decrease was analyzed from the moment of the maximum rate of pressure drop, which usually coincides with the closure of the aortic valves. The pressure drop curve was logarithmized with natural logarithms and divided into 4-5 sections with different degrees of curve slope. The relaxation time constant was calculated for each section. Its inverse value characterizes the relaxation time constant (tau). In 31 patients with LV EF 52-60%, three types of the dynamics of the relaxation rate constant were identified during the pressure decrease in the isovolumic phase: in 9 patients, the isovolumic relaxation constant (IRC) steadily increased as the pressure decreased; in 13 patients, it continuously decreased; and in 9 patients, the dynamics of IRC change was intermediate, with an initial increase followed by a decrease. In diastolic dysfunction, one group of patients had an adaptation type associated with an increase in the LV wall elasticity, while the other group had a different type of adaptation associated with its decrease. Each type has advantages and disadvantages. This is probably due to changes in the structure of the sarcomeric protein connectin (titin).

Aortic valve leaflets are asymmetric and correlated with the origin of coronary arteries.

Asymmetry of the aortic valve leaflets has been known since Leonardo Da Vinci, but the relationship between size and shape and origin of the coronary arteries has never been examined. Our aim was to evaluate this anatomy in a population of pediatric patients using a cross-sectional study design. Consecutive pediatric patients with trans-esophageal echocardiography (TEE), with or without trans-thoracic echocardiography (TTE), were included in our study. Exclusion criteria: (I) bicuspid aortic valve; (II) aortic valve stenosis; (III) hypoplasia of aortic valve annulus, or aortic root; (IV) truncal valve; (V) coronary artery atresia; (VI) previous surgery on aortic valve and/or coronary arteries. In pre-operative TTE and intra-operative TEE inter-commissural distance and length of aortic valve leaflets were measured in short axis view in the isovolumic phase of systole. Echocardiography investigations, anonymized and randomly coded, were independently reviewed by at least two readers. Echocardiography, angiography, cardiac computed tomography (CT) scan and magnetic resonance imaging (MRI), and operative notes were reviewed to identify origin of coronary arteries. Two hundred sixty-one pediatric patients were identified, 93 excluded per our criteria, leaving 168 patients, age 2.6±4.3 years, weight 12.87±17.34 kg, 128 (76%) with normal and 40 (24%) with abnormal coronary arteries. In TTE and TEE measurements the non-coronary leaflet had larger area (P<0.001), while the right and left had equal areas, but different shape, with the left leaflet longer (P<0.001) and narrower (P=0.005) than the right. With the major source of blood flow from the right coronary sinus, the non-coronary leaflet was still the longest. However, there was no statically significant difference between the size and shape previously observed between the right and left leaflets. Our study showed asymmetry of size and shape among aortic valve leaflets, and a relationship with coronary artery origin. The complex aortic root anatomy must be approximated to optimize function of any surgical repair. These findings also may prove useful in the pre-operative definition of coronary artery anatomy and in the recognition of coronary artery anomalies.

Analysis of Relaxation Phase in the Rat Heart

The rate and depth of myocardial relaxation determine left ventricular (LV) filling in early diastole. To analyze the relaxation phase, the method of logarithm of LV pressure fall in rats was used. A gradual acceleration of relaxation was found during the transition from the isovolumic phase to the auxovolumic phase, immediately before the opening of the atrioventricular valves. The relaxation rate constant in this phase has been inversely correlated with the values of the minimum LV diastolic pressure and LV endsystolic volume. The results suggest that the gradual acceleration of relaxation is due to the straightening of the spring-like structure of connectin (titin), which is compressed during contraction.

Cardiac Helical Function. Fulcrum and Torsion

The aim of this study was to investigate a) the starts and ends of the continuous myocardium; b) the slippage between the myocardial segments, when performing both torsion and ventricular detorsion, implies that there should be an antifriction mechanism that avoids dissipating the energy; c) the electrical activation of the endocardial and epicardial myocardium and secondarily understand ventricular twist and the mechanism of active suction during the diastolic isovolumic phase.

Elucidating tricuspid Doppler signal interpolation and its implication for assessing pulmonary hypertension.

Doppler echocardiography plays a central role in the assessment of pulmonary hypertension (PAH). We aim to improve quality assessment of systolic pulmonary arterial pressure (SPAP) by applying a cubic polynomial interpolation to digitized tricuspid regurgitation (TR) waveforms. Patients with PAH and advanced lung disease were divided into three cohorts: a derivation cohort (n = 44), a validation cohort (n = 71), an outlier cohort (n = 26), and a non‐PAH cohort (n = 44). We digitized TR waveforms and analyzed normalized duration, skewness, kurtosis, and first and second derivatives of pressure. Cubic polynomial interpolation was applied to three physiology‐driven phases: the isovolumic phase, ejection phase, and “shoulder” point phase. Coefficients of determination and a Bland−Altman analysis was used to assess bias between methods. The cubic polynomial interpolation of the TR waveform correlated strongly with expert read right ventricular systolic pressure (RVSP) with R 2 > 0.910 in the validation cohort. The biases when compared to invasive SPAP measured within 24 h were 6.03 [4.33; 7.73], −2.94 [1.47; 4.41], and −3.11 [−4.52; −1.71] mmHg, for isovolumic, ejection, and shoulder point interpolations, respectively. In the outlier cohort with more than 30% difference between echocardiographic estimates and invasive SPAP, cubic polynomial interpolation significantly reduced underestimation of RVSP. Cubic polynomial interpolation of the TR waveform based on isovolumic or early ejection phase may improve RVSP estimates.

Cardiac Helical Function. Fulcrum and Torsion

Background: The aim of this study was to investigate: a) the starts and ends of the continuous myocardium; b) the slippage between the myocardial segments, when performing both torsion and ventricular detorsion, implies that there should be an antifriction mechanism that avoids dissipating the energy; c) the electrical activation of the endocardial and epicardial myocardium and secondarily understand ventricular twist and the mechanism of active suction during the diastolic isovolumic phase.

Evidence of Inotropic Improvement in LVAD Patients with High I-CARS Score

<h3>Purpose</h3> A high INTERMACS Cardiac Recovery Score (I-CARS≥7) has greater likelihood of myocardial recovery in bridge-to-recovery patients compared to a low score (<7). This scoring index was limited in predicting echocardiography changes for an unselected left ventricular assist device (LVAD) population. We investigated its use in predicting pressure-volume (PV) loop changes in bridge-to-transplant patients using non-invasively derived PV loops. <h3>Methods</h3> We prospectively recruited 32 HeartWare Assist Device (HVAD) patients (mean 55.9±12.3 years, 81.3% male) and calculated their I-CARS. HVAD controller-derived parameters and oscillometric brachial pressure (SphygmoCor Xcel) were obtained to non-invasively estimate single-cycle ventricular pressure and volume. PV loops (n=77) and contractile indices were derived at pre-defined timepoints post-implant: 1, 3, 6 months (n=26, 29, 22). The trends of contractility indices, dPdtmax (peak contractility in isovolumic phase), dPdtmax/devP (sensitive to inotropic changes) and dPdtmax/LVEDV (independent of preload), were analysed according to high (≥7) vs low (<7) I-CARS. <h3>Results</h3> I-CARS was calculated in all patients (18.5% I-CARS≥7). Patients with low I-CARS were less likely to have <2 years heart failure diagnosis, more likely to have an implanted ICD and a higher pre-implant creatinine level (Table). Other demographic variables were comparable. Using a statistical linear mixed model, high I-CARS patients demonstrated a 0.50±0.15s monthly increase in dPdtmax/devP (p=0.001) and only modest changes in dPdtmax and dPdtmax/LVEDV (p=0.055, p=0.110). dPdtmax, dPdtmax/devP and dPdtmax/LVEDV remained largely unchanged in low I-CARS patients across the 6-month period. <h3>Conclusion</h3> Selective improvement in dPdtmax/devP amongst high I-CARS patients suggests strong associations between determinants of I-CARS and cardiac contractility. Larger scale studies to understand the determinants of I-CARS and its relation to inotropic improvement would inform remodelling.

Evaluation of Cardiac Function of Pregnant Women with High Blood Pressure during Gestation Period and Coupling of Hearts with Peripheral Vessels by Ultrasonic Cardiogram under Artificial Intelligence Algorithm.

The research was aimed at analyzing the value of the optimized eXtreme Gradient Boosting (XGBoost) algorithm-based ultrasound cardiogram images in the diagnosis of pregnant hypertension patients. A total of 145 pregnant women (85 cases suffered from hypertension disease during pregnancy and 60 other normal women were healthy) were selected as the reference to the comparison and analysis of ultrasound cardiac function parameter, common carotid artery parameter, and the coupling relationship between hearts and cervical vessels of pregnant hypertension patients. The results demonstrated ultrasound cardiac function parameter of pregnant hypertension patients as follows. The maximum volume of the left atrium (LAVmax) was 35.65 mm, left ventricular end-systolic volume (LVESV) was 31.07 mm, and left ventricular end-diastolic volume (LVEDV) was 88.73 mm. All the above indexes were obviously higher than those of the normal control group (P < 0.05). Besides, intima-media thickness (IMT) of common carotid artery (465.84 μm), pulse wave velocity (PWV) (8.09 m/s), pressure of turning point 1 from isovolumic contraction phase to ejection phase (PT1) (126.5 mmHg), arterial enhancement pressure (AP) (6.14 mmHg), and arterial pressure enhancement index (8.58%) were all significantly higher than those of the normal control group (P < 0.05). In addition, the correlation between the coupling (E/A) of hearts and carotid artery of pregnant hypertension patients and PWV was not obvious (r = −0.08432, P > 0.05). The results of the research indicated that intima-media inside carotid artery of pregnant hypertension patients thickened obviously, and it became less elastic compared with that of normal healthy pregnant women. What is more, cardiac morphological changes were manifested mainly as the enlargement of the left atrial chamber and the thickening of the interventricular septum. Volume load and blood flow velocity both increased, and left ventricular diastolic function was damaged. XGBoost algorithm-based ultrasound cardiogram images could improve the diagnostic effects of hypertension during pregnancy effectively.

Derivation of in vivo pressure-volume loops for post-heart transplant patients using real-time 3D echocardiography and left ventricular catheterisation

Abstract Background Image-based methods that combine catheterisation with non-concurrent cardiac magnetic resonance (CMR) imaging data and echocardiography (echo) is gaining more interest than the conductance catheter method to derive pressure-volume loops (PVLs) due to improved accuracy and accessibility of LV volume quantification [1–3]. However, accurate temporal registration between LV pressure and volume is not well developed. Purpose We propose a framework for temporally registering invasive LV and aortic pressures (LVP and AOP) acquired during left heart catheterisation with real time 3D echocardiography (RT3DE) to generate in vivo PVLs in a group of heart transplant (HTx) recipients. Methods 25 orthotopic HTx recipients (mean age: 54±8 years and 7 female) indicated for routine coronary assessment were recruited for invasive hemodynamic measurement and RT3DE imaging. A fluid-filled pigtail catheter was used to measure LVP and AOP with simultaneous electrocardiogram (ECG) over several (9–15) heartbeats. Within an hour of catheterisation, single-beat transthoracic RT3DE of the LV was performed from the apical window in a left lateral decubitus position. Imaging parameters were optimized for each patient to maximize the temporal resolution (between 15–41 imaging frames per cycle). We developed a piecewise linear temporal scaling method based on cardiac events (end-diastole (ED), end of isovolumic contraction (eIVC), end-systole (ES), end of isovolumic relaxation (eIVR), and diastasis (DS)) of RT3DE and haemodynamic measurement to resample the LVP at the RT3DE imaging frames between the cardiac events to construct PVLs (Fig. 1a). Geometric LV models were manually fitted at ED and ES, followed by automatic tracking across intermediary frames to estimate LV volume over the entire cardiac cycle (Fig. 1b). The temporally aligned pressure values were further averaged to find the beat-averaged LV PVL (Fig. 1c). Results Based on the number of cardiac cycles selected for haemodynamic analysis, multiple in vivo PVLs were constructed for each patient. A beat-averaged PVL was also computed for each patient (Fig.1d). With the exception of one case, the beat-averaged PVLs exhibited classically representative shape with distinct isovolumic contraction and isovolumic relaxation phases. The individual diastolic PVRs for all patients are shown in Fig.1e, with beat-to-beat variation observed in most patients. For some cases, the variation manifested as an offset in LVP, whereas changes in the diastolic PVR slope were observed in other cases. Conclusion Temporal alignment scheme based on cardiac events allowed accurate derivation of patient-specific in vivo PVLs from catheterization and RT3DE measurements. Application to heart transplant recipients revealed beat-to-beat variation of haemodynamic state. Further analysis of the diastolic PVRs will allow quantification of chamber stiffness for HTx recipients. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Health Research Council of New Zealand Patient-specific PVLs

Effect of Sarcomere Length Change During Isovolumic Phase of Left Ventricle on Hemodynamics

Effect of Sarcomere Length Change During Isovolumic Phase of Left Ventricle on Hemodynamics

Application of vector flow mapping technique in the assessment of left intraventricular pressure gradients in heart failure patients

Objective To evaluate the changes of intraventricular pressure differences (IVPDs) and intraventricular pressure gradients (IVPGs) in different phases of cardiac cycle in patients with heart failure(HF) patients by relative pressure imaging based on vector flow imaging(VFM). Methods Forty-nine HF patients with left ventricular ejection fraction (LVEF) lower than 0.50 hospitalized in Qilu Hospital of Shandong University from November 2018 to January 2019, including thirty-three patients with HF with reduced ejection fraction (HFrEF group) and fifteen patients with midrange ejection fraction (HFmrEF group), and forty-three controls were enrolled in this study. Clinical data and echocardiographic images were collected and the conventional left ventricular diameter, mass, volume, and systolic and diastolic function parameters were measured. IVPDs and IVPGs during isovolemic systole (IC), rapid ejection (RE), isovolemic diastole (IR), rapid filling (RF) and atrial systole (AC) phases were obtained by the VFM technique. The changes of IVPDs and IVPGs in different phases between the HF and control groups, and their correlations with conventional ultrasound parameters were analyzed. Results IVPDs and IVPGs in heart failure group were significantly reduced compared with the control group especially in isovolumic relaxation phase(all P<0.001). IVPDs and IVPGs showed a decreasing trend in the control group, HFmrEF group and the HFrEF group(P<0.001). IVPDs and IVPGs were correlated with LVID, LVMI, ESV, LVEF, GLS and E/e′ (all P<0.01), among which IVPD-IR and IVPG-IR were best correlated. IVPD-IR and IVPG-IR had excellent diagnostic efficacy for HF patients with LVEF<0.5, with cut-off values of <0.73 mmHg (AUC=0.915, P<0.001) and <0.103 mmHg/cm (AUC=0.932, P<0.001), respectively. Conclusions Early diastolic hemodynamics are severely impaired when systolic function declines.IVPG-IR, as a marker of left ventricular diastolic function, significantly correlates with left ventricular systolic function, and can be used as a potential indicator for assessing left ventricular systolic and diastolic function in patients with heart failure and identifying patients with heart failure. Key words: Vector flow imaging; Relative pressure imaging; Intraventricular pressure gradients; Heart failure

P625Impact of hemodialysis on a novel and noninvasive index for quantification of stroke work obtained by left ventricular pressure-volume loop area using speckle tracking echocardiography

Abstract Background Left ventricular (LV) pressure-strain and pressure-volume (P-V) loop area reflect global myocardial work (MW) and stroke work (SW), but clinical use of these indexes is limited by the need of invasive pressure measurement. A noninvasive method to obtain LV pressure-strain loop area was recently introduced to examine MW by speckle tracking echocardiography (STE). Purpose We sought to evaluate the impact of preload change on MW and SW obtained using this novel method and to examine the utility to assess LV contractile performance by the SW and end-diastolic volume (EDV) relation (SW-VED) in patient with hemodialysis (HD). Methods LV pressure in a cardiac cycle was estimated using systolic blood pressure (SBP), LV minimum diastolic pressure (mDP) and end-diastolic pressure (EDP) in 20 HD patients (age 67±9)and 25 controls (age 67±9) by utilizing the profile of an empiric, normalized reference curve adjusted according to the duration of LV isovolumic and ejection phases as defined by timing of aortic and mitral valve events by echocardiography. Pulmonary capillary wedge pressure (ePCWP) is estimated as 10.8 – 12.4 × Log (left atrial active emptying function/minimum volume): KT index as previously reported. LVEDP were estimated as 12.3 – 10.1 × KT index. We examined the relation between LV pressure decline (Tau) and mDP by catheterization in 126 patients. Tau is estimated as isovolumic relaxation time/(ln 0.9 × systolic BP − ln ePCWP) as previously reported. SW was obtained by P-V loop area using the combination of pressure (SBP, mDP and EDP) and LV volume by 3D-STE. Echo parameters and BP were measured before and after HD and before and after leg up in controls. Results The mDP obtained by catheterization had a good correlation with Tau (Tau = 33.7 + 2.06 × mDP, r=0.70, p&lt;0.01). LVEF by 3D-STE was increased in controls after leg up (59±5 to 62±4%) associated with increased LVEDV (85±25 to 91±26ml), whereas there was no difference in LVEF before and after HD (61±9 vs 61±10%) instead of decreased EDV after HD (101±23 to 92±24ml). SBP and PCWP in HD was decreased after HD (SBP: 149±25 to 140±15, PCWP: 9.8±4.3 to 8.5±3.6mmHg). MW and SW were increased after leg up in controls (1706±443 to 1972±461mmHg% and 4072±1938 to 5044±1958mmHgml) and those were decreased after HD (1964±441 to 1794±756mmHg% and 5475±1335 to 4722±1949mmHgml). LV SW-VEDin HD without LV dilation (EDVI&lt;70ml/m2, n=12) was decreased compared to controls (143±115 vs 241±152) and that in HD with LV dilation was further decreased compared to HD without dilation. Conclusion LVSW noninvasively obtained by P-V loop area was increased in controls associated with increased preload and decreased in HD with decreased preload and SW-VED was deceased in HD. This novel and noninvasive method may be of potential utility to assess LV contractility and have a clinical interest and value to assess LV function.

Evaluation of diastolic left ventricular energy loss in patients with pregnancy-induced hypertension using vector flow mapping

Objective To quantify the diastolic average energy loss (EL) of left ventricle in patients with pregnancy-induced hypertension (PIH) by vector flow mapping (VFM) technique and explore the clinical significance of EL in evaluating left ventricular diastolic function in patients with PIH. Methods Fifty-seven cases of singletonic PIH in late pregnancy (PIH group) and 38 cases of the third trimester normal singleton pregnancy (control group) were enrolled in this study. VFM were used to analyze the total average energy loss (ELt) and average energy loss at the basal level (ELb), the papillary muscle level (ELp), and the apical level (ELa) in isovolumic relaxation, rapid filling, mid-diastol and atrial systole phases, and the differences between the two groups were compared. The correlation between ELt and E/e in both groups were analyzed. Results In PIH group, ELt, ELb, ELp and ELa in the mid-diastolic and atrial systolic phases were significantly higher than those in control group (all P<0.01); ELt, ELp, ELa in isovolumic diastolic phase and ELt, ELb and ELa in fast filling phase were higher than those in control group (all P<0.05). There was a positive correlation between ELt and E/e in isovolumic diastolic phase, rapid filling phase and atrial systolic phase in PIH group (r=0.326, 0.386, 0.403; all P<0.05). There was a positive correlation between the ELt of fast filling and atrial systolic phases and E/e in control group (r=0.498, 0.371; all P<0.05). Conclusions Increased left ventricular diastolic flow EL in PIH patients reflects the abnormal intraventricular hemodynamic changes, and it is related to left ventricular diastolic function parameters for the quantitatively evaluation of PIH patients, and might be feasible to reveal the extent and mechanism of left ventricular diastolic dysfunction. Key words: Vector flow mapping; Pregnancy-induced hypertension; Ventricular function, left; Energy loss

Left ventricular energy loss during systole in patients with hypertension detected by ultrasonic vector flow mapping

Objective To evaluate the value of left ventricular energy loss (EL) in the systolic left ventricular hemodynamic changes in hypertensive patients by ultrasonic flow vector imaging(VFM). Methods Ninty-eight hypertensive patients were divided into non left ventricular hypertrophy group (NLVH group) and left ventricular hypertrophy group (LVH group) according to the left ventricular mass index(LVMI). Thirty-one healthy adults were erolled as control group. The average total energy loss (EL-T), basal energy loss (EL-B), middle energy loss (EL-M) and apical energy loss (EL-A) of each isovolumic contraction phase, fast ejection phase and slow ejection phase were obtained by VFM, the difference among the three groups were compared. Results ①EL-T and EL-B in isovolumic phase, rapid ejection phase and slow ejection phase in NLVH group were higher than those in control group (P<0.05 or P<0.01); EL-T, EL-B, EL-M and EL-A in isovolumic phase, rapid ejection phase and slow ejection phase in LVH group were all higher than those in control group (P<0.05 or P<0.01); EL-M in isovolumic phase and rapid ejection phase, EL-T, EL-B, EL-M and EL-A in slow ejection phase in LVH group were higher than those in the NLVH group (P<0.05 or P<0.01). ②There was a positive correlation between EL-T and LVMI (r=0.311, P<0.01), EL-B and LVMI (r=0.219, P<0.05), EL-M and LVMI(r=0.207, P<0.05), EL-T and LVEF(r=0.340, P<0.05), EL-B and LVEF(r=0.367, P<0.01) in isovolumic contraction phase. There was a positive correlation between EL-B and LVEF(r=0.359, P<0.01) in rapid ejection phase. There was a positive relation between EL-B and LVEF(r=0.352, P<0.05) in slow ejection phase. Conclusions The EL of systolic peroid in hypertensive patients increased, which suggests that the left ventricular hemodynamic changes abnormally, VFM can accurately evaluate the changes of hemodynamic during systole. Key words: Echocardiography; Hypertension; Ventricular function, left; Vector flow mapping

The assessment of diastolic blood flow field related energy loss of left ventricle in patients with right heart dual-chamber pacing using ultrasonic vector flow mapping

Objective To assess the changes of diastolic blood flow field and energy loss of left intra-ventricular flow in patients with heart dual-chamber pacing using ultrasonic vector flow mapping(VFM), and to explore the clinical value of VFM technology for the assessment of left ventricular diastolic function in patients with cardiac pacing. Methods After routine echocardiographic exam for 51 patients with dual-chamber pacing as pacemaker group and 73 volunteers as control group, the color Doppler flow imagings from standard dynamic apical two, three and four-chamber views for 3 completed cardiac cycles were acquired in VFM mode, and were imported to DAS-RSI workstation subsequently. The off-line measurement of diastolic left intra-ventricular flow for prescription parameter, such as energy loss, vortex area and vortex intensity, was performed. The left intra-ventricular parameters of two groups were compared for difference, and the correlationship between parameters at isovolumetric, early, mid and late diastolic phases was analyzed with SPSS 17.0 statistical software. Results 1) The energy losses of pacemaker group compared with the those of control group were significantly higher at isovolumetric, early, and late diastolic phases(Z=-6.689, -5.683, -3.014, -4.418, P<0.001), and at mild-diastole, energy loss was reduced mildly(Z=-3.014, P<0.05). 2) Vortical intensity of pacemaker group was significantly greater than that of the control group in isovolumic, early and late diastolic phases (t=2.388, 2.988, 3.153, P<0.05) separately, there was not statistically vertical intensity differences in mid-diastole between the two groups and no significant vortical area difference between the two groups. 3) There was no correlationship in the two groups for all the phases between energy loss and vertical area or intensity. For each phases, vortical area of the control group was correlated with vortical intensity(r=0.396-0.809, P=0.003-0.000). Only isovolumic vortical area was correlated with the vortex intensity in pacemaker group (r=0.807, P=0.000). Conclusions The dual-chamber pacing of right ventricle and right atrium could induce a significant energy loss of left intra-ventricular fluid and obvious abnormal distribution of eddies during diastole. The disappearence of correlationship between vertical area and intensity in cardiac pacemaker group during left diastole might lead to more turbulance flow and energy loss of left ventricle during right dual chamber pacing. Key words: Echocardiography; Ventricular function, left; Cardiac pacing, artificial; Vector flow mapping

Renal Denervation Improves Cardiac Diastolic Dysfunction by Restoring Serca2a Transcription in Uninephrectomized Rats

Background: The mortality and morbidity of heart failure with preserved ejection fraction has increased. Sarcoplasmic reticulum Ca2+-ATPase type 2a (SERCA2a) regulates cardiac functions, and a reduction in SERCA2a expression has been documented in left ventricular (LV) diastolic dysfunction. By contrast, SERCA2a overexpression improves LV diastolic dysfunction. Thus, transcriptional regulation of SERCA2a may be a new therapeutic target. The aim of this study was to determine whether renal denervation, a treatment for resistant hypertension, is a regulator of SERCA2a transcription in vivo. Methods: Uninephrectomy and 6-week salt loading in three-week-old male Sprague-Dawley rats were used to devise a cardiac diastolic dysfunction model, and mechanical renal denervation was performed. The expression of SERCA2a and related molecules was evaluated with quantitative polymerase chain reaction and western blot analyses. The maximal positive LV pressure development (+dP/dtmax) and time constant at the isovolumic relaxation phase (Tau) were determined with cardiac catheters. Results: Uninephrectomy combined with a high-salt diet significantly reduced the messenger RNA expression and protein abundance of SERCA2a, which were restored by renal denervation. In accordance with changes in SERCA2a transcription, uninephrectomy and the high-salt diet decreased LV diastolic function, which was evaluated by Tau and restored by renal denervation. LV systolic function, measured with +dp/dtmax, was preserved. Renal denervation did not lower blood pressure, urinary protein levels, cardiac hypertrophy, or fibrosis. Conclusions: We found that renal denervation is a regulator of SERCA2a transcription in vivo. Our data may provide new therapeutic insights into LV diastolic dysfunction and warrant further study.

Electrical Propagation in the Mechanisms of Torsion and Suction in a Three-phase Heart

Background: The hypothesis of Torrent Guasp considers that the ventricular myocardium consists of a continuous muscular bandthat begins at the level of the pulmonary valve and ends at the level of the aortic root, limiting both ventricular chambers. Thisanatomy would provide the interpretation for two fundamental aspects of left ventricular dynamics: the mechanism of left ventriculartorsion and rapid diastolic filling due to the suction effect.Objectives: The aim of this study was to investigate the electrical activation of the endocardial and epicardial bands to understandventricular torsion, the mechanism of active suction during the diastolic isovolumic phase and the significance of the residual volume.Methods: Five patients underwent three-dimensional electroanatomic mapping. As the descending band is endocardial and theascending band is epicardial, two sites of puncture were used.Results: Three-dimensional endo-epicardial mapping demonstrates an electrical activation sequence in the area of the apical loop inagreement with the synchronic contraction of the descending and ascending band segments. The simultaneous and opposing radialactivation of the ascending band segment, starting in the descending band segment, in the area in which both band segments intertwine,is consistent with the mechanism of ventricular torsion. The late activation of the ascending band segment is consistent withits persistent contraction during the initial period of the isovolumic diastolic phase (the basis of the suction mechanism), and takesplace without need of postulating further electrical activation after the QRS complex.Conclusions: This study explains the process of ventricular torsion and the suction mechanism, and demonstrates that the activationof the ascending band segment completes the QRS, ruling out the traditional concept of passive relaxation during isovolumic diastole.

Age-dependent and ‘pathologic’ changes in ICG waveforms resulting from superposition of pre-ejection and ejection waves

Impedance cardiography (ICG) is a popular bioimpedance application used for the non-invasive evaluation of the left ventricular stroke volume and contractility. It implies the correct determination of ejection start and end points and the amplitudes of certain peaks in a differentiated impedance cardiogram. An accurate identification of ejection onset by ICG is often problematic, especially in cardiologic patients, due to the peculiar character of the waveforms. A simple theoretical model was employed to test the consequences of the hypothesis that two major processes can contribute to the formation of an impedance systolic wave: (1) the pre-ejection changes in heart geometry and the surrounding vessels produced by ventricular contraction during the isovolumic phase, and (2) the expansion of aorta and adjacent arteries during the ejection per se. The former process initiates the pre-ejection wave while the latter triggers the ejection wave, both of which contribute to the impedance pulse waves associated with the heartbeats. A new two-bell model predicts a potential mechanism responsible for the abnormal shapes of ICG derivative dZ/dt due to the presence of the pre-ejection waves and explains the related errors in systolic time intervals and amplitude parameters derived from such ICG waveforms. It also advances an alternative viewpoint on the nature of the dZ/dt B-point notch. An appropriate decomposition method opens a promising way to avoid the masking effects of these waves and to correctly determine the onset of ejection as well as the corresponding peak amplitudes from the ‘pathologically shaped’ ICG signals.

Is MRI the Preferred Method for Evaluating Right Ventricular Size and Function in Patients With Congenital Heart Disease?

Is MRI the Preferred Method for Evaluating Right Ventricular Size and Function in Patients With Congenital Heart Disease?

CARDIAC-BORDER SEGMENTATION IN 2D ECHOCARDIOGRAPHY IMAGE SEQUENCE USING LEVEL SET METHOD TO MEASURE GLOBAL PARAMETERS

Identifying end-diastole (ED) and end-systole (ES) frames is highly important in the process of evaluating cardiac function and measuring global parameters accurately, such as ejection fraction (EF), cardiac output (CO) and stroke volume (SV). The aim of this study is to develop a new method based on measuring volume changes in left ventricle (LV) during cardiac cycle. For this purpose, the level set method is used both in detecting endocardium border and quantifying cardiac function of all frames. Demonstrating LV volumes at a time displays ED and ES frames and volumes used in calculating required parameters. Since ES and ED frames exist in iso-volumic phases of the cardiac cycle with minimum and maximum values of LV volume signals, such peaks can be utilized in finding related frames. The results obtained from 44 volunteers, as golden values, were validated by an experienced echocardiologist through manual annotation and comparison of EF, CO and SV measurements. These measurements prove the suggested method provides accurate and reliable automatic detection of ED and ES frames.